STUDIES ON INORGANIC ION EXCHANGERS SUMMARY · of ions on the basis of their different sizes. The...
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STUDIES ON INORGANIC ION EXCHANGERS SUMMARY THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN CHEMISTRY BY Hasan M. A. Abdul Aziz DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY ALIGARH INDIA OCTOBER, 1984
Transcript of STUDIES ON INORGANIC ION EXCHANGERS SUMMARY · of ions on the basis of their different sizes. The...
STUDIES ON INORGANIC ION EXCHANGERS
SUMMARY
THESIS SUBMITTED FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY IN
CHEMISTRY
BY
Hasan M. A. Abdul Aziz
DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY
ALIGARH INDIA
OCTOBER, 1984
- > " ' • ^ " " ' ? t ^ . .
f2-71.S T H
The thesis entitled "Studies on Inorganic ion exchangers"
comprises of five chapters. The first chapter deals with the
general introduction on ion exchange, A critical review of
studies on inorganic ion exchangers has been given based on the
literature survey consulted through available Journals, The
importance of inorganic ion exchangers has been emphasized over
their organic counterparts which sho\* limitations for high
temperature and presence of ionizing radiation. The first
synthetic inorganic ion exchanger which has been studied in
detail is zirconium phosphate, A number of similar substances
may be prepared by combining oxides of groups III and IV with
the more acidic oxides of groups V and VI of the periodic table.
The structure of these inorganic ion exchangers is stiff,
therefore, they are more selective and suitable for the separation
of ions on the basis of their different sizes. The related
earlier work on synthetic inorganic ion exchangers and chelating
ion exchange resins have been summarized In two tables. As many
as 265 references have been listed.
The second chapter deals with the "Separation of anions
and cations on thorium tellurite - a new amphoteric ion exchanger",
This material worlcs as a cation exchanger in the alkaline medium
and as an anion exchanger in the acidic medium. Its application
towards important separations such as: bromate from bromide, of
nitrite from nitrate marked its analytical utility. The
( 1 1 )
preparation of the material Is quite simple i , e , by mixing-
solutions of thorium n i t r a t e and sodium t e l l u r i t e in the
required r a t i o a t pH 1. The anion exchange capacity var ies
from 0.8 t o ±,k meq per gram. For ca t ions the sorption
capacity va r i e s from 0.68 to 0.8A» mllllmoles per gram.
However, t h i s material does not show any H l ibe ra t ion
capaci ty . The exchanger shows no de t e r io ra t i on in i t s exchange 0
behaviour upto 150 C. The chemical composition of the exchanger
has been found to be Th:Te ratio of 1:2. On the basis of
distribution studies a number of separations for cations as well
as anions achieved, are reported.
The third chapter deals with the "Synthesis and
properties of thorium triethylamlne as a new anion exchanger".
The introduction of triethylamlne in the metal oxide framework
has been made to observe Its anion exchange behaviour on one
hand and chelate formation with cations on the other. It is
likely that the incorporated triethylamlne acquires a free
positive charge on its nitrogen atom and is responsible for
its anion exchange capacity while the presence of nitrogen
with a lone pair of electrons offers sites for the complex
formation with the metal ion. Thorium triethylamlne has been
found to behave as a monofunetional anion exchanger on the
basis of pH titration. A study of K^ values at different
concentrations of sodium hydroxide has been made and a number
( l i l )
of anion separations have been achieved on the bas i s of large
differences In K va lues . Chemical s t a b i l i t y , chemical
composition, heat e f fec ts and IR have been studied to charac
t e r i z e the material formed.
The s tudies on "Synthesis and propert ies of zirconium
tr ie thylamine as a new anion exchanger" have been reported in
fourth chapter . Zirconium tr iethylamine shows many proper t ies
s imilar to thorium tr iethylamine e . g . anion exchange behaviour,
sorption behaviour. However, zirconium triethylamine i s
b e t t e r than thorium triethylamine in chemical s t a b i l i t y and
sorption capaci ty . The IH studies confirm that in the formation
of these types of exchangers the amine i s incorporated with the
metal oxide forming the matrix.
The f i f th chapter deals with the "Redox s tudies on
hydrazine sorbed zinc s i l i c a t e " . This gives a new c l a s s of
exchange mater ial by the sorption of a reducing agent,
hydrazine sulphate, on an inorganic ion exchanger, zinc s i l i c a t e ,
The most important advantage of such mater ia ls for redox studies
over dissolved redox reagents i s the i n so lub i l i t y of the redox
exchanger in the medium. Therefore, the solution i s free from
contamination of any redox mater ia l or i t s products. Only
e lec t rons and protons are t ransferred between the exchanger and
the so lu t ion . Imraobillzatlon of hydrazine in the layers of
zinc s i l i c a t e makes i t to lose i t s ion exchange capacity and
( iv )
to acquire redox properties Instead. Dilute acidic, dilute
basic and neutral solutions can be safely used for redox
studies on this material. The successful reductions of
Fe(lll), V(V), Mo(Vl), Cr(Vl) and Sb(V) have been achieved on
Its column. The reduction of only those substances Is possible
whose redox potentials are less than that of reducing agent
Incorporated with the exchanger. Therefore, attempts to reduce
As(V) were failed. The rate of reduction has been studied
and found to be fast enough.
STUDIES ON INORGANIC ION EXCHANGERS
THESIS SUBMITTED FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY IN
CHEMISTRY
BY
Hasan M. A. Abdul Aziz
DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY
ALIGARH INDIA
OCTOBER. 1984
T2728
(^^^Pt^^h^l
^ / / . - ; • ' ^ • - ' ^
j-agdlsn J). (Kai^al M.Sc, Ph.D,
READER IN CHEMISTRY
DEPARTMENT OF CHEMISTRY ALIGARH MUSLIM UNIVERSITY
ALIGARH-202001 INDIA
C E R T I F I C A T E
This Is to ce r t i fy tha t the work embodied In
t h i s t h e s i s i s o r ig ina l and i s su i table for submission
for the award of Ph.T), degree in Chemistry.
^/C ^ i ^ ^ -/ J.P.RAWAT /
DEDICATED to mt( brother SHAFIQUE M. ABDUL MAJEED
Without whose sacrifice I could not have undertaken this work.
^tknotDletrgement
A C K N O W L E D G E M E N T
I express my deep sense of gra t i tude and indebtedness
t o Dr. J.P.Rawat for h i s excellent advice and able guidance.
He was always a source of insp i ra t ion throughout the en t i r e
course of my t h e s i s work.
I am very much thankful to Prof. Wasiur Rehman and
Prof. M.S.Ahmed of the Department of Chemistry, Aligarh
Muslim Univers i ty , Aligarh for providing me a l l research
f a c i l i t i e s ,
I fee l very happy in paying my sincere thanks to
Dr. Mohd.Iqbal and Dr. Masood Alam for t h e i r valuable
suggestions during the preparation of t h i s t h e s i s . I am
thankful to my research colle,agues espec ia l ly Mr. Balbir Singh
for t h e i r cooperation during my work.
Las t , but not the l e a s t , I am also thankful to the
Cultural Department, Ministry of Education, Government of
India, for f inanc ia l a s s i s t ance .
M-iiFf^M I HASAN M.A.ABDUL AZIZ /
C O N T E N T S
I . LIST OF PUBLICATIONS
I I I , LIST OF FIGURES
I V . CHAPTER - I
INTRODUCTION
REFERENCES
PAGE
(1 )
I I . LIST OF TABUES ( j l )
(V)
1
35
V . CHAPTER _ I I
SEPARATION OF ANIONS AND CATIONS ON THORIUM
TELLURITE - A NEW AMPHOTERIC iQN EXCHANGER 52
EXPERIMENTAL
RESULTS
DISCUSSION
REFERENCES
53
55
73
76
V I . CHAPTER - I I I
SYNTHESIS AND PROPERTIES OF THORIUM TRIETHYLAMINE
AS A NEW ANION EXCHANGER 77
EU^RimNTAL Q^
RESULTS g2
DISCUSSION ^Q5
REFERENCES ^^Q
PAGE
V I I . CHAPTER - IV
SYNTHESIS AND PROPERTIES OP ZIRCONIUM TRIETHYL-
AMINE AS A NEW ANION EXCIUNGER 1 ^
EXPERIMENTAL 112
RESULTS
DISCUSSION
BEFERENCES
129
13^
VIII. CHAPTER - V
REDOX STUDIES ON HYDRAZINE SULPHATE SORBED ZINC
SILICATE ^^^
EXEERIMENTAL l^g
RESULTS ^^g
DISCUSSION jj^g
REFERENCES ^e^
( 1 )
L I S T 0 F P U B L I C A T I O N S
1 . SEPARATION OF ANIONS AND CATIONS ON THORIUM TELLURITE -
A NEW AMPHOTERIC ION EXCHANGER.
J.LIQUID CHROMATOGRAPHY, 7 ( 8 ) , I 6 9 I ( 1 9 8 4 ) .
2 . REDOX STUDIES ON HYDRAZINE SULPHATE SORBED a;iNC SILICATE
J.INDIAN CHEMICAL SOCIETY. LX ( l O ) , 993 ( 1 9 8 3 ) .
3 . SYNTHESIS AND PROPERTIES OF THORIUM TRIETHYLAMINE AS A
NEV ANION EXCHANGER.
CHROMATOGRAPHIA (COMMUNICATED).
4 . SYNTHESIS AND PROPERTIES OF ZIRCONIUM TRIETHYLAMINE AS A
NEW ANION EXCllAN(a:R.
J .LIQUID CHROMATOGRAPHY (COMMUNICATED),
( 11 )
L I S T O P T A B L E S
PAGE
TABLE I
TABLE II
TABLE III
TABIE IV
TABLE V
TABIE VI
TABLE VII
TABIE VIII
TABLE IX
TABIE X
TABIE XI
TABIE X I I
TABIE X I I I
TABLE XIV
SYNTHESIS AND ION EXCHANGE PROPERTIES OF
MULTIVALENT METAL SALTS 5
SOME OF THE CHELATING ION EXCHANGE RESINS 26
CONDITION OF PREPARATION AND PROPERTIES
OF THORIUM TELLURITE 54
ANION EXCHANGE AND CATION SORPTION CAPACITY
FOR VARIOUS ANIONS 56
ANION EXCHANGE CAPACITY AT DIFFERENT
TEMPERATURES - 58
COMPOSITION OF THORIUM TELLURITE 5 9
DISSOLUTION OF THORIUM TELLURITE 6 0
DIRECT POTENT lOMETRIC TITRATION FOR THORIUM
TELLURITE EXCHANGER , 61
REVERSE POTENTIOMETRIC TITRATION FOR THORIUM
TELLURITE EXCHANGER 63
DISTRIBUTION COEFFICIENT VALUES OF SOME ANIONS 65
DISTRIBUTION COEFFICIENT VALUES OF SOME CATIONS 66
CONDITIONS OF PREPARATION OF THORIUM
TRIETHYLAMINE EXCHANGER 80
ION EXCHANGE CAPACITIES OF THORIUM TRIETHYL
AMINE FOR DIFFERENT ANIONS 82
ION EXCHANGE CAPACITY OF THE EXCHANGER FOR
FIVE CYCLES 85
( i i i )
TABLE XV
TABIE XVI
TABLE XVII
TABLE XVIII
TABLE XIX
TABLE XX
TABLE XXI
TABLE XXII
TABLE XXIII
TABLE XXIV
TABIE XXV
TABLE XXVI
TABIE XXVII
PAGE
ION EXCHANGE CAPACITY AS A FUNCTION OF
CONCENTRATION OF ELUTING REAGENT 86
CAPACITY AT DIFFERENT TEMPERATURES FOR
BICHROMATE IONS 88
WEIGHT LOSS OP THE EXCHANGER AT DIFFERENT
TEMPERATURES 9I
STABILITY OF THORIUM TRIETHYLAMINE EXCHANGER 92
DISTRIBUTION COEFFICIENTS OF SOME ANIONS ON
THORIUM TRIETHYLAMINE EXCHANGER 97
QUANTITATIVE SEPARATION OF ANIONS ON THORIUM
TRIETHYLAMINE EXCHANGER ioh
CONDITIONS OF PREPARATION AND PROPERTIES OF
ZIRCONIUM TRIETHYLAMINE EXCHANGER I I 3
ANION EXCHANGE CAPACITIES OF ZIRCONIUM
TRIETHYLAMINE FOR DIFFERENT ANIONS 116
STABILITY OF ZIRCONIUM TRIETHYLAMINE IN
DIFFERENT SOLVENTS 118
CAPACITY OF EXCHANGER FOR CHROMATE IONS
AT DIFFERENT TEMPERATURES I I 9
K^ VALUES FOR DIFFERENT ANIONS IN a
DIFFERENT SOLVENTS 123
QUANTITATIVE SEPARATION OF ANIONS ON
ZIRCONIUM TRIETHYLAMINE 128
WEIGHT LOSS OF THE EXCHANGER AT DIFFERENT
TEMPERATURES I30
( iv )
TABLE XXVIII
TABLE XXIX
TABLE XXX
TABLE XXXI
TABLE XXXII
TABLE XXXIII
TABLE XXXIV
PAGE
DISSOLUTION OF HYDRAZINE SULHIATE 133
REDUCTION OF F e ( I I l ) TO F e ( l l ) AND
V(V) TO V(IV) 140
REDUCTION OF Mo (VI) TO Mo(lV) AND
Sb(V) TO S b ( I I l ) 141
REDUCTION OF Ce(IV) TO C e ( l l l ) AND
Cr(Vl ) TO C r ( I I I ) 142
MAXIMUM REDOX CAPACITY OP SOME REDUCIBLE
SUBSTANCES I43
RATE OP REDUCTION OF VANADIUM(V) TO
VANADIUM(IV) 145
STANDARD REDOX POTENTIAL OF REDOX COUPIES 149
( V )
L I S T O F F I G U R E S
PAGE
FIGURE 1
FIGURE 2
FIGURE 3 ( a )
(b)
FIGURE k (a )
(b)
FIGURE 5 (a)
(b)
FIGURE 6 (a)
(b)
FIGURE 7
FIGURE 8
FIGURE 9
FIGURE 10
FIGURE 11
FIGURE 12
ANION EXCHANGE CAPACITY AT DIFFERENT
TEMPERATURES
POTENT 10METRIC TITRATION CURVES ON
THORIUM TELLURITE EXCIIANOER
SEPARATION OP Hg(IT) FROM C u ( I I )
SEPARATION OF N i ( I I ) PROM C u ( l l )
SEPARATION OF C d ( l l ) FROM P b ( l l )
SEPARATION OF H g ( I l ) FROM V o ( l )
SEPARATION OP NO" FROM NO'
SEPARATION OF PO^" FROM MoOr' .
SEPARATION OF V0~ PROM MoOr"
SEPARATION OF S 0 ' ~ FROM SO"
SEPARATION OF BrO" FROM Br"
ION EXCHAN(» CAPACITY AGAINST IONIC
RADII (FOR HALIDES)
PLOT OF ION EXCHANGE CAPACITY AGAINST
NUMBER OF REGENERATION CYCLES
ION EXCHANGE CAPACITY AS A FUNCTION OF
CONCENTRATION OF ELUENT
PLOT OF CAPACITY AGAINST TEMKRATURE
THERMOGRAM OF THORIUM TRIETHYLAMINE
EXCHANGER
57
62
68
68
69
69
70
70
71
71
72
84
Qk
87
89
90
( vi )
PAGE
FIGURE 13
FIGUHE Ik
FIGURE 15 (a)
FIGURE 16 (a)
(b)
FIGURE 17 (a)
(b)
FIGURE 18 (a)
(b)
FIGURE 19
FIGURE 20
FIGUHE 21
FIGURE 22
FIGURE 23 (a)
(b)
FIGURE 2^ (a)
(b)
I.R.SPECTRUM OF THORIUM TRIETHYLAMINE
EXCHANGER
POTENTlOMETRIC TITRATION CURVE FOR THORIUM
TRIETHYLAMINE EXCHANGER
SEPARATION OF I " FROM C r 0 7 "
SEPARATION OF B r " FROM CrO""*
SEPARATION OF I ~ FROM Cr o l "
SEPARATION OF Br"* FROM C r „ 0 " " 2 7
SEPARATION OF I ~ FROM V0~
SEPARATION OF Br FROM PO 3-
SEPARATION OF S C N " FROM C r _ 0 ~ " 2 7 3 .
SEPARATION OF I FROM F e ( C N ) ^
SEPARATION OF l " FROM S O J " 2 3
ION EXCHANGE CAPACITY AGAINST IONIC RADII
(FOR HAL IDES)
I.R.SIECTRUM OF ZIRCONIUM TRIETHYLAMINE
EXCHANGER
POTENTIOMETRIC TITRATION CURVE FOR
ZIRCONIUM TRIETHYLAMINE EXCHANGER
SEPARATION OF Br" FROM Or O"" 2 7
SEPARATION OF I ~ FROM CrgO""
SEPARATION OF C l ~ FROM AsO"
SEPARATION OF SCN~ FROM CrgO""
9
95
99
99
100
100
101
101
102
102
103
115
120
122
125
125
126
126
( v i l )
PAGE
i'lGUHE 25 ( a ) SEPARATION OF B r FROM CrO~~ 12?
(b) SEPARATION OF l " FROM CiO^" 127
FIGURE 26 RATE OF REDUCTION OF VANADIUM(V) 141,
CMPTER-I
INTRODUCTION
Now-a-days the Ion-exchange has come to be recognized
as an extremely valuable technique. All over the world
numerous plants are In operation for developing the separations
of Inorganic, organic and biochemical mixtures. Ion-exchange
Is a process in which an Insoluble (or immiscible) mater ia l ,
when comes In contact with an e l ec t ro ly t e so lu t ion , takes up,
s to lchlometr lca l ly , Ions of pos i t ive or negative charge and
re leases other Ions of l ike charge from the exchanger phase
Into the solution phase. In labora tor ies Ion-exchangers are
used as an important tool for the solut ion of new problems
facing our I n d u s t r i a l i s t s and s c i e n t i s t s . The most Important
application of ion-exchange i s the pur i f ica t ion of water In
an age when a i r and water pol lut ion Is leading to an alarming
s i t u a t i o n .
A descr ip t ion of ion-exchange process can be ci ted In
the most ancient l i t e r a t u r e following a paragraph wri t ten In
the holy Bible , Moses ( l ) wrote tha t the b i t t e r water can be
made drinkable by using pieces of wood, A r i s t o t l e (2) stated
that sea water loses parts of a s a l t content when f i l t e r ed
through cer ta in type of s o i l . The ion-exchange proper t ies of
wood cel lulose In the f i r s t case and tha t of s i l i c a t e s In the
second case might have served to improve the t a s t e of water.
For a long period no ef for ts were made to c i t e the ancient
references.
The phenomenon of Ion-exchange was rediscovered toy
Thomson (3) and Vay (k) In 1850 toy the name of "toase exchange**
In minerals present In s o i l . This was at the time when the
s tudies were lacking even In the ex is tence of Ions in s o l u t i o n .
However, the phenomenon of "toase exchange" was sys temat ica l ly
studied t o toe reversltole and t o involve chemically equivalent
quant i t ies of the toase taken up and of that re l eased ,
never the le s s , i t was recognized as an important phenomenon
t o s o i l f e r t i l i t y . I t was estatolished toy Eichom that z e o l i t e s
were responsltole for t h i s exchange In s o i l s ( 5 ) . Aluminium
s i l i c a t e was f i r s t synthesized toy Harms and Rumpler ( 6 ) .
According to Lemtoerg (7) and Wiegner (8) the materia ls
responsltole for t h i s phenomenon were mainly c l a y s , z e o l i t e s ,
g luconi tes and humic a c i d s . These d i scover i e s led to the use
of the natural materials for water so f ten ing . Amtoitious Gans
adopted t h i s technique to recover gold from sea water. But
h i s amtoition remained unfu l f i l l ed toecause the material of t h i s
type availatole at that time proved t o toe inadequate for the
purpose. Gans (9) recognized the pract ica l u t i l i t y of the
ion-exchange phenomenon for water softening using natural and
synthet ic z e o l i t e s and c l a y s . The exhausted toed of the Ion-
exchanger was regenerated toy passing a concentrated so lut ion
of sodium or potassium s a l t s . Because of p laus l to i l l ty of
regeneration these z e o l i t e s and c l a y s could toe used over and
again. Limitations of z e o l i t e s and c lays were soon rea l i zed ,
i . e . z e o l i t e s are decomposed toy ac ids whereas c l a y s are
'i 3
d i f f i c u l t t o handle. To overcome these l imi ta t ions a search
for s table Ion-exchange material was s t a r t e d . In 1931
Kullgran (lO) observed tha t su lphi te ce l lu lose works as an
ion-exchanger for the determination of copper.
An in te res t ing discovery began in 1935 when Adams and
Holmes found that crushed phonograph recoipds exhibi t Ion-
exchange p rope r t i e s . This remarkable effect led the inventors
t o the synthesis of organic ion-exchange res ins which had much
b e t t e r propert ies than any of the previous products (11).
Various improvements were made in these r e s ins , mainly a f t e r
world war I I by companies in U.S.A. and England. These
re s ins are s table towanls acids and easy to handle . The
s t ruc ture can be varied as des i red , therefore , the d i f f i c u l t i e s
observed with z e o l i t e s and clays were removed by the
introduct ion of r e s i n s . Since then these organic ion-
exchangers have been used both in laboratoiy and on indus t r i a l
scale for separa t ions , recoveries of metals, pur i f i ca t ion of
water, concentration of e l e c t r o l y t e s , react ions of p rec ip i t a t e s
and elucidating the mechanism of many react ions (12) .
The appl ica t ions of organic ion-exchange r e s in s are
a l so limited under ce r ta in condit ions i . e . they are unstable
In aqueous systems at high temperatures and in presence of
the ionizing r a d i a t i o n s . For these reasons there has been a
revived in te res t in inorganic ion-exchangers In recent years ,
as they are unaffected by ionizing radia t ions and are less
sensi t ive t o higher temperatures. The s t ruc ture of these
Inorganic ion-exchangers I s s t i f f , therefore , they are more
select ive and su i tab le for the separation of Ions on the bas i s
of t h e i r d i f fe ren t s i ze s . For t h i s reason they can also be
used as ionic or molecular s i eves . Being su i tab le towards
ionizing rad ia t ions they can be used advantageously In
reac tor technology. In order to understand these applicat ions
and to Improve upon them systematic fundamental s tudies are
being persuaded on these ma te r i a l s . This new in t e r e s t In
Inorganic Ion-exchanger may be said to begin in 19^3. I t was
f i r s t shown by Boyd (13) tha t columns containing f inely
divided zirconium phosphate supported on s i l i c a gel could be
used to separate uranium and plutonlum from f iss ion products
by an ion-exchange process. In addition t o zirconium
phosphate many other similar substances may be prepared by
combining oxides of group IV with the more acidic oxides of
groups V and VI of the periodic Table. Such ion-exchangers
are as follows in Table I ,
El
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22
The preparation of an anion exchanger r e s in with good
chemical an l thermal s t a b i l i t y remains an outstanding problem.
The anion exchange resins are usual ly prepared by introducing
an amine or ammonium grouping as a source of pos i t ive lonogenic
group into polystyrenedivinyl benzene copolymer through a
Friedel-Craf ts condensation. The common Ion exchangers are
based on trimethylamine. An inorganic anion exchanger can be
prepared by introducing tr lethylamine group in to the hydrous
oxide of a t e t r a v a l e n t metal ion. The amine group may also
act as a chelat ing group to ce r t a in ca t ions and hence such a
mater ial may be useful in two ways ( l ) as anion exchanger, and
(11) a chelate exchanger.
A new chela t ing mater ia l , tltanium(TV) diethanolamlne,
has been prepared by modification of hydrous t i tanium oxide
(2^^) .
A new c l a s s of ion-exchange res ins was developed by
Gregor in 1952 by subs t i tu t ing a chelate group in a highly
crosslinked hydrocarbon matrix. Since then many such substances
known as chelat ing ion-exchangers have been described in the
l i t e r a t u r e . In these types of exchangers the use of chemical
react ions can a l so be considered to play an important r o l e .
The chelating ion-exchange mater ia ls behave a l ike t rue ion-
exchangers and the functional group i s a chela t ing group which
is fixed within the matr ix. Formation of a complex with a metal
ion i s an example of a coordination compound in which the donor
23
of lone pair of electrones is the complexing agent and the
central metal ion forms a coordinate-covalent bond with it.
The formation of the complex depends upon the stability
constant of the chelate formed.
A large number of processes for the preparation of
chelating ion-exchangers have been cited in the literature
in the recent past. They are based mainly on condensation,
polymerization or addition polymerization and introduction
of chelating function either during polymerization or
attaching after polymerization.
Varied physical forms may thus be obtained with such
a wide range of preparations. Further the nature of chemical
additions is based on the introduction of wide range of
materials. Chelating exchangers thus have the desirable
properties of high capacity, high selectivity, kinetics and
high reaction rate.
In addition to the materials mentioned so far a number
of other types of exchangers have been developed. In particular,
electron exchangers, redox exchangers and chelate ion-exchangers
have found the highest Interest of all such materials. The
electron exchangers may be considered as solid oxidation and
reducing agents. They contain the species forming a redox
couple and after having oxidised (or reduced) a substrate the
electron exchangers can be regenerated by a suitable oxidizing
24
or reducing agent. The r e a c t i v i t y of e lect ron exchangers Is
due to h u i l t - i n redox components. Ihe most important advantage
of e lec t ron exchangers over dissolved oxidising or reducing
agents i s t h e i r i n so lub i l i t y and hence an electron exchanger
can he eas i ly separated from the solut ion containing a
subs t ra te being oxidised or reduced. The solution i s free
from the contamination of any redox agent or i t s products .
Only e lec t rons and protons are t ransferred between the r e s in
and the so lu t ion . Therefore, the only possible change in the
so lu t ion , except for the redox react ion of the subs t r a t e , i s
a change in pH, Another advantage of e lectron exchangers i s
tha t they can be readi ly regenerated (oxidised or reduced)
a f t e r use ,
TVie electron exchangers are character ised by t h e i r
redox capac i ty , redox po ten t i a l and reac t ion r a t e . The redox
capaci ty i s the amount (in equivalents) of a substrate being
oxidised or reduced by a specified amount of the exchanger.
The reac t ion rate indicates the time required for redox process
under a given set of condi t ions .
Vernon (245) has sunmjarized the nature of such compounds
r ecen t ly , Polycondensatlon has been applied by Bayer (246,24?)
for the preparation of chelat ing exchangers containing glyoxal
bi8-2-hydroxyanll groups and he successfully recovered copper
and uranium from sea water by the use of these ma te r i a l s , He
also produced a sulphur analogue res in wliich is se lec t ive to
25
silver, gold, mercury and which has also been used for the
recovery of gold from sea water, a problem first taken by
Gans (9). The chelating agent may also be placed In the
mobile phase, using a non ionic reverse phase support, which
essentially becomes a cation exchanger (248), The interest
in this field has been developed recently and such exchangers
are reported in Table TI.
26
TABLE I I
SOME OF TIIE CHELATING ION-EXt;nANGE ItESINS
SL. TYBE OF CHELATING IlESIN SORPTION NO, CAPACITY,
( in ,moles / g )
SELECTIVITY REFERENCE
1 . Oxime and d ie thy lamlno r e s i n
2 , 8-hydroxyqulnoline and 8-hydroxyqulnadine r e s i n
3 . 0-hydroxyoxime r e s i n
4 , Th iog lyco la te r e s i n
2,00 Cu(TT)
5 . Amino acid type r e s i n
6 . Phosphate type r e s i n
7 . N-Acylphenyl-hydroxy1amines
C u ( l l ) and Z n ( l l )
Mo(VI) and C u ( I l )
Ag( l ) B i ( I I l ) S n ( I v ) , S b ( l I l ) , Hg(Tl) from O.IM acid;Cd(TT). Fb( I l ) ,U(VI ) from pll 3 .5
U(VI). C u ( l l ) , N i ( l l ) and F e ( l T l )
U(VI) and Th(lV)
(2^9)
(250)
(251)
(252)
0.-^5
(253)
(253)
(25k)
27
The studies of inorganic based chelate exchangers are
meagre. Therefore, the synthesis and use of such exchangers
in chemical analysis m ^ be of Importance, A new approach
has been t r i e d to introduce the coraplexing agents with the
matrix of the exchanger. On t h i s ba s i s aluminium t r i e t h a n o l -
amlne and thorium trlethanolamlne have been synthesized.
Thorium trlethanolamlne has been found t o behave as a good
chelat ing exchanger.
For a complete descr ipt ion of a material as an ion-
exchanger the following propert ies must be studied;
1, The Ion-exchange capaci ty ,
2 , The res is tance towards acids and bases ,
3 , Composition,
h. Potentlometrie titrations,
5, Distribution of counter ions between solution and exchanger
phases,
6, Kine t ics ,
7, Thermodynamics, and
8, Analyt ical app l i ca t ions .
Ion-exchange capacity i s one of the most fundamental
quan t i t i e s for charac ter iza t ion of any Ion-exchange ma te r i a l .
For a strong lon-exchanger, the capacity can readi ly be
determined by d i rec t t i t r a t i o n . Various types of capac i t i e s
can be expressed In d i f fe ren t manners. The equilibrium ion-
exchange capacity for a strong lon-exchanger can be determined
28
Tjy d i r e c t t i t r a t i o n of strong cation exchanger (In H form)
with a strong base . Majority of the synthetic inorganic Ion-
exchangers behave as a weak Ion-exchanger and therefore , the
d i r ec t t i t r a t i o n I s not r e l i a b l e . In t h i s case lon-exchange
capacity Is determined by replacement of hydrogen ions from
the exchanger phase by the counter ions of a neutral s a l t
solut ion and then determination of the equilibrium ion-exchange
capaci ty i s done by pH- t l t r a t l ons , Maximum ion-exchange
cai)acity equal t o the number of ionogenic groups per specified
amount of lon-exchanger may d i r e c t l y be determined by simple
column operation passing the e l e c t r o l y t i c solution over the
ion-exchange mater ia l"( in H* form) and t i t r a t i n g the l ibera ted
acid In the effluent by a standard base so lu t ion . Although the
pure lon-exchange capacity of a sol id ion-exchanger can be
determined in several ways, a gravimetric method (255) offers
for many Ion-exchangers the advantage of r e l a t i ve ly high
accuracy and very simple equipment requirements for only one
difference weighing without any ana ly t i ca l cheitilcal
determination of ton. Breakthrough capacity (256) i . e . , the
useful capacity for u t i l i z i n g the column operat ions, Is of
importance when the ra te of exchange i s slow. This r a t e may
be so slow tha t the t o t a l capacity may not be u t i l i zed In an
actual operat ion. The operation i s discontinued at
breakthrough before reaching the complete equil ibrium. This
capacity which is u t i l i z ed un t i l breakthrough occurs i s
known as breakthrough capacity or dynamic capaci ty . I t
29
depends upon operating conditions and Is lower than the
equilibrium Ion-exchange capacity.
The lon-exchange meterla] must be studied for chemical
stability in acidic and basic media to cheek its limitations.
The most valuable application of Ion exchange for
the analytical chemist is the ion exchange chromatography.
The components of a mixture of cations or anions Ina sample
can be separated from each other by this technique under
suitable conditions which can be adjusted by simple approaches.
The affinity of an ion exchanger for an exchangeable
ion (counter ion) is given quantitatively by the distribution
coefficient K., which is defined as follows:
K " ^o" Concentration in the exchanger phase d Ion concentration in solution
The distribution of an ion between the exchanger and
solution phases is a measurement of selectivity. Often, the
ion-exchanger takes up certain ions in preference to the other
present counter ions. This selectivity may depend, mainly
upon: (1) Donnan potential, (il) sieve action, and (ill) complex
formation. The selectivity is an Important factor to study the
separations. On the basis of distribution coefficients it is
possible to predict the separation of one ion from the other.
30
The Inorganic ion-exchangers have found numerous
Important ana ly t ica l applicat ions as categorized below:
( i ) Purif icat ion of substances on a large sca le ,
( i i ) Separation of one ion from the other on a small ion-
exchanger column,
( i l l ) Ion-exchange paper chromatographic separat ions,
( iv) Elec t rophores is ,
( v) Ion-exchanger for gas chromatography,
( v i ) Solid s ta te separa t ions ,
( v i i ) Specific spot t e s t s ,
( v l i i ) Use of ion-exchanger beads to locate the end point in
t i t r a t i o n , and
( ix) Use of ion se lec t ive e l ec t rodes .
Purif icat ion on a large scale can be made by passing
the sample solut ion through the Ion-exchanger beds which take
up ce r t a in mater ia ls in preference of o the r s . The exchanger
bed can be regenerated into sui table form by conventional
methods (257). The technique can also be u t i l i s e d to recover
t r a c e s of elements from the d i lu te so lu t ions . The elements
present In ionic form are exchanged by equivalent amount of
the counter ion present in the exchanger. The elements can
be eluted from the exchanger by su i table e l e c t r o l y t i c reagent .
Ion-exchange i s , with very few exceptions, a revers ib le
process . The meta l l ic ions are exchanged s toJchlometr lcal ly
with hydrogen ions in exchanger phase and the metal ions can
31
be determined I n d i r e c t l y by the a p p l i c a t i o n of exchange
r e a c t i o n s :
nRII* • M""^ = MR -f nil'*' n
where R r e p r e s e n t s the s t r u c t u r a l u n i t of the ion-exchanger ,
and H**" and M"* are the c a t i o n s t ak ing par t in the i o n -
exchange. A s i m i l a r method can be adopted for the replacement
of anions by hydroxyl ions s t o i c h i o m e t r i c a l l y ,
Ion-exchange has resolved the most d i f f i c u l t problem
in chemical a n a l y s i s I . e . s epa ra t ion of t y p i c a l components
having s i m i l a r enough p r o p e r t i e s . Column chromatography i s
v a l u a b l e , s ince the substances separa ted are c o l l e c t e d
q u a n t i t a t i v e l y .
Since the c r y s t a l l i n e ion-exchangers have c a v i t i e s
of d e f i n i t e s i z e , t hey a l s o possess ion s ieve p r o p e r t i e s .
The coun te r Ions having l a r g e r r a d i i than the ho les in the
c a v i t y cannot p e n e t r a t e and t h e r e f o r e , they can be separa ted
from those sma l l e r ions which can e a s i l y e n t e r i n t o the
c a v i t y . These s e p a r a t i o n s were f i r s t achieved by C l e a r f i e l d
on zirconium phosphate c r y s t a l s (258) and a re summarized
below:
Zirconium phosphate and anhydrous metal s a l t were
heated in a plat inum d i s h . The exchange r e a c t i o n tak ing p lace
32
is represented by the following equation:
Zr(HP0^)2.H20 * 2/X MCl^ — ^ ^""^^h/X ^^hh * "^^ * V
When zinc chloride or hafnium chloride were exchanged a new
phase was obtained which persisted to about 2/3 of total
capacity of the exchanger. These wide ranges of metal content
forming the same structure indicate that solid solutions of
cation within crystal lattice are forming. The fact that a
variety of cation type gives the same phases (almost identical
Interplaner spacing but different intensities) Indicates that
the crystal lattice remains rigid with the cations occupying
similar exchanged sites. This Is unlike the behaviour of
zirconium phosphate exchanging Ions in aqueous electrolyte
solution where the lattice expands by the movement of the
c><-zirconium phosphate layers to accommodate hydrated
cations. The elution of cations with dilute acid solutions
proved the phenomenon as ion-exchange, the cations could
also be removed by contacting the exchange phases with
gaseous hydrogen chloride.
Some ion-exchange separations were also achieved,
A solution containing equal parts of lithium chloride and
caesium chloride was evaporated to dryness and the dry salt
mixture was ground together with c<-zirconium phosphate.
33
On heating the mixture at 125 C lithium exchanged leaving
caesium because the cavJtleb are large enough to permit a O A.
cation of about 2-6 A, Thus Cs should he excluded as was
observed experimentally.
However, very few l i t e r a t u r e i s available on ion-
exchange in molten s a l t . Alber t i and A l l u l l i (259) t reated
ion-exchange on amorphous zirconium phosphate in molten
n i t r a t e s . They found that lithium ion is grea t ly preferred
over potassium ions by the exchanger.
Albert i a lso studied the specific conductance of
amorphous zirconium phosphate In Li ^ Na , K and Cs forms
over the range 2-^0/^ conversions (26o). The specif ic
conductance of Li"*" and Cs*** fonns was found to decrease with
percent conversion while that of the Na* and K^ forms f i r s t
increases and then decreases as conversion proceeds, A
t en t a t i ve model was proposed to explain the observed
phenomenon.
Within only a couple of decades ion-exchange has
become one of the most important techniques for de l i ca t e
separations in ana ly t i ca l and preparative inorganic chemistry,
Ion-exchange has played an important role in the separation
of rare ear ths in the i so la t ion and iden t i f i ca t ions of
t ransuranic elements and for the enrichment of i so topes .
34
Most of the Ion-exchange operat ions, whether In the
laboratory or in the indus t r i e s , are carr ied out in columns.
Column operation i s b e t t e r than batch process, pa r t i cu la r ly
for separat ions , as in column separations a new theo re t i ca l
plate comes in contact every time when tlie solut ion i s passed
through a bed of ion-exchange beads where I t s composition i s
changed by ion-exchange, while in the batch operation, the
complete separation may not always be possible as the
equilibrium i s to be maintained in the system and the
equilibrium Is based on the d i s t r i bu t i on coeff ic ient of the
const i tuent present in the sample so lu t ion .
The present work deals with the synthesis of a new
amphoteric inorganic ion exchanger, thorium t e l l u r i t e . I t s
propert ies and appl icat ions for the separation of cat ions and
of anions have been s tudied. Two new anion exchangers based
on t r ie thylamine, zirconium tr iethylamine and thorium
triethylamine have been synthesized. Their anion exchange
behaviour and other propert ies have been s tud ied , A new
redox exchange mater ia l has been prepared by immoblliizlng
hydrazine sulphate on zinc s i l i c a t e . The successful reduction
of cer ta in metal ions has been s tudied.
35
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CHAPTER-II
SEPARATION OF ANIONS AND CATIONS ON THORIUM TELLURITE-
A NEW AMPHOTERIC ION EXCHANGER
52
Separation of anions have been of much Interest to
various workers (1-2), But that have largely been accomplished
on organic anion exchangers. Some of the synthetic Inorganic
Ion exchangers are also known to behave both cation as well as
anion exchangers. Such an amphoteric behaviour has been found
to be limited mainly to the hydroxides of: Sn(IV) (3), Zr(IV)
( ), Al(III) (5) and few others (6-7). Their behaviour is
usually a function of pH.
Studies on a new inorganic ion exchanger, thorium
tellurite has been reported in this chapter. This material
works as a cation exchanger in the alkaline medium and as an
anion exchanger in the acidic medium. Its application towards
separation of BrOl from Br", NOg from NOl marked its
analytical utility. Such exchangers should be of much use
where a single mixed bed of cation and anion exchangers
is used.
53
EXIERIMENTAL
Apparatus
A metzer spectra 75 and Ellco pH meter Li 10 (India)
were employed for spectrophotometric and pH measurements.
The shaking of the samples were done on a SICO shaking
machine.
Reagents
A known amount of thorium n i t r a t e (B.D.H.) and sodium
t e l l u r i t e (B.D.H.) were dissolved in water in separate standard
f lasks for preparing O.lM so lu t ion .
All the solut ions of various cat ions and anions used
for K, values and separation s tudies were prepared by taking
300 mg of pa r t i cu l a r cation or anion dissolving in 100 ml
of d i s t i l l e d water .
Synthesis Procedure
Five d i f fe ren t samples of thorium t e l l u r i t e were
prepared by mixing O.lM thorium n i t r a t e and O.lM sodium t e l l u r i t e
in the volume r a t i o as given in Table I I I . The white p rec ip i t a te
so obtained was kept at room temperature for k8 hrs t o ensure
complete p r ec i p i t a t i o n . The prec ip i ta te was then f i l t e r e d , o
washed and dried in an oven at ^0 C. It took nearly a week
for the product to dry completely on treatment with delonlzed
54
water the dried sample broke down into small pieces. It was o
aga in d r i e d a t kO C i n t h e oven . The e x c h a n g e r was t h e n
Conver ted i n t o d e s i r e d fo rm. F o r c o n v e r s i o n i n t o a p a r t i c u l a r
a n i o n i c form an a c i d i c s o l u t i o n of t h e a n i o n should be t a k e n .
When d e s i r e d t o be t a k e n in a c a t i o n i c form, a b a s i c c a t i o n
s o l u t i o n , e . g . Ca(0H)2 f o r c a l c i u m shou ld be employed ,
TABUE I I I
CONDITION OF PI^PARATION AND PROPERTIES OF THORIUM TELLURITE
SAMPLE CONDITIONS OF SYNTHESIS MOLARITY OP REAGENTS
I
THORIUM SODIUM NITRATE TELLU
RITE
T i MIXING pH VOLUME RATIO
PROPERTIES
ION- NATURE OF EXCHANCE PRECIPITATION CAPACITY
S I
S I I
S I I I
S IV
S V
0 . 1
0 . 1
0 . 1
0 . 1
O.J
0 . 1
0 . 1
0 . 1
0 . 1
0 . 1
I j l
1:2
1:3
3 : 1
2 j l
0
1
2
3
1
0 . 8 2
1.40
OAk
0.00
0.60
Thick
Thick
Mild
No precipitation
Thick
55
RESULTS
Anionic Exchange Capacity
The anion exchange Cfipaclty was determined by column
operation. One gram thorium tellurite in desired anionic form
was taken on a glass wool support of a column and IM solution
of various anions was passed through it at a flow rate of -1
0.50 ml min . The eluted anions were then determined in the
effluents. To determine the anion exchange capacity for
sulphate the exchanger was taken In sulphate form. The eluted
sulphate ions were determined by precipitation with barium
chloride and back titrating the excess of barium Ions with 0,1M
EBTA. For other ions the exchanger was taken in chloride form
and the eluted chloride ions were determined by Mohr's
method (8).
Cation Sorption Capacity
One gram of thorium tellurite was taken in a glass
column and 10 ml fractions of cationic solution containing
predetermined amount of the cations Cu(TT), Fe(IIl), NI(II),
Co(II), Cd(Il) and Mg(n) were passed through the column at
a flow rate of 0,5 ml mln" . The amount of cation in the
collected effluent was determined for each fraction. The
process was kept continued till the amount of cation in the
influent and the effluent remained the same. The amount
sorbed was then calculated by substracting the amount of
56
c a t i o n found In the e f f l u e n t front the amount I n i t i a l l y taken
i n I n f l u e n t . The r e s u l t s are summarized in Table IV.
TABLE IV
ANION EXCHANGE AND CATION SORPTION CAPACIIT FOR VARIOUS ANIONS
SL. NO.
ANIONS EXCHANGE CAPACITY,
m.eq .g"
CATIONS SORPTION CAPACITY
m.moles g -1
1 .
2 .
3 .
k,
5.
6.
CI
NO"
< -
< -
Br"
OH"
1.40
1.00
l.?A
0.80
1.22
1.40
0.60
(0H~ uptake)
(OH" l i b e r a t i o n )
Cu 2*
Ni 2+
Fe
Co
3+
2 +
Mg 2 +
0.84
0.80
0.68
0.74
0.80
Effect of drying temperature on anion exchange capacity
Thorium t e l l u r i t e sample was heated at d i f ferent
temperatures in a muffle furnace for 2 h r s . The anion exchange
capacity of each of the dried sample was then determined by
column operat ion. The r e s u l t s are presented in Table V and
plotted in Figure 1 .
57
< Q. < O
liJ CD Z < I o ><
z o z <
cr
6
100 200 300 400
TEMPERATURE ( **c )
500
FIG.l. ANION EXCHANGE CAPACITY AT DIFFERENT TEMPERATURES
58
TABLE V
ANION EXCHANGE CAPACITY AT DIFFERENT TEMPERATURES
SL. ' TEMPERATURES ' ANION EXCHANGE CAPACITY N O . t f \
(meq/gm)
1 . 50 1 .35
2 . 100 1.35
3 . 150 1.32
4 . 200 1.08
5 . 250 0 . 8 0
6 . 300 0 . 5 8
7 . 350 0 . 2 0
8 . 400 0 . 0 6
Chemical C o m p o s i t i o n
200 mg p o r t i o n of t h e Ion e x c h a n g e r was d i s s o l v e d In
30 ml of hot c o n c e n t r a t e d h y d r o c h l o r i c a c i d . The s o l u t i o n
was t h e n c o o l e d t o room t e m p e r a t u r e and d i l u t e d t o 250 ml w i t h
de ion l i i ed w a t e r . 100 ml of t h i s s o l u t i o n was t a k e n and
t e l l u r i u m was p r e c i p i t a t e d w i t h h y d r a z i n e h y d r o c h l o r i d e -
s u l p h u r d i o x i d e m i x t u r e ( 9 ) . In a n o t h e r 100 ml p o r t i o n
t h o r l u m ( l V ) was d e t e r m i n e d v o l u m e t r i c a l l y w i t h ET)TA s o l u t i o n .
T e l l u r i u m and t h o r i u m were d e t e r m i n e d t h r i c e f o r r e p r o d u c i b l e
r e s u l t s . R e s u l t s a r e g i v e n i n T a b l e VI,
TABLE VI
COMPOSITION OF THORIUM TELLURITE
59
SAMPLE NO.
MILLIMOLES OF MTLLIMOLES OF MO IE RATIO THORIUM TELLURIUM Th:Te
1
2
3
0.48
0.48
0.47
0.97
0.96
0.95
1:201
1:2
Is 201
Chemical S t ab i l i t y
0,50 gm of the exchanger was shaken in a conical flask
for four hours in the solution in which i t s d i s so lu t ion was to
be checked. The supernate was decanted and i t s thorium(IV)
content was determined t i t r i m e t r l c a l l y with EDTA. Tellurium
was determined spectrophotometrically with thiourea (lO), The
r e s u l t s are given In Table VII,
TABLE VII
DISSOLUTION OF THORIUM TELLURITE
60
SOLVENT
Th
AMOUNT, mg
Te
D e i o n i z e d w a t e r
HNO-
HNO-3
NIl OE
Nil, OH
HCl (
HCl (
CH 01]
NaOH
NaOH
(IM)
(2M)
[ (2M)
[ iw)
:iM)
;2M)
[
(IM)
(2M)
Acetone
0 . 0
0 . 0
1^.2
0 . 0
1.21
0 . 0 3
12 .80
0 . 0
8 .0
O'i.O
0 . 0
0 . 0 0
0 . 0 5
2 2 . 6 2
0 . 0
1.82
0 . 0 6
21.2C
0 . 0
1 0 . 1
2 2 . 2
0 . 0
Ton exchiuio^ti p o l e n t i o m e t r i c t i t r a t i o n
Thorlura t e l l u r i t e b e i n g a m p h o t e r i c In n a t u r e , t h e pH
t i t r a t i o n s were performed in tooth a l k a l i and a c i d s o l u t i o n s w i t h
t h e i r r e s p e c t i v e s a l t s f o l l o w i n g Topp and p a p p e r ' s method ( 1 1 ) .
To s t u d y t h e c a t i o n exchange h e h a v i o u r , O.IM s o l u t i o n of a l k a l i
6 1 .
(NaOII, MOH and LlOIl) and O.IM s o l u t i o n of t h e i r r e s p e c t i v e s a l t s
were shaken with 0«5 gtn of the exchanger . The mixing r a t i o of
t h e two s o l u t i o n s were "taken In such a way t h a t t o t a l volume
remained 20 ml in a l l t h e c a s e s . Af ter being shaken fo r four
hours the pll of the r e a c t i o n mixture was measured. S i m i l a r
exper iments were perfoime-] t ak ing IICI, HgSO. and HNO, with
t h e i r r e s p e c t i v e s a l t s for de termining the anion exchange
behav iour on thorium t e l l u r i t e . F igure 2 g ives pH t i t r a t i o n
curves In both a l k a l i and acid s o l u t i o n s with t h e i r r e s p e c t i v e
s a l t s . The r e s u l t s a re presented in Tab les VII I and IX.
TABLE VII I
DIRECT POTENTIOMLTRIC TITRATION FOR THORIUM TELLURITE EXCIIANGKI
t
SL. VOLU>E OF O.IN HCl (ml) pH ^^* (TOTAL VOLUME OF O.lN HCl ^
O.iN NaCl = 20 ml)
1. 0 9.40 2. 2 6.40
3. 4 3.90
^. 6 2.90
5. 8 2.40 6. 10 2.00 7. 12 1.94 8. 14 1.90 9. 16 1.86
10. 18 1.84 11. 20 1.82
62
I a
(a) 0-1NNaOH + 0-1NNaCl (b) 0-INHCl + 0-INNaCl
0 4 8 12 16 20
VOLUME OF EQUILIBRATING SOLUTION
FIG.2. POTENTIOMETRIC T ITRATION CURVES ON THORIUM TELLURITE EXCHANGER
63
TABLE IX
REVERSE POTENTlOMETRIG TITRATION FOR TIIoniUM TELLURITE EXCHANGER
SL . VOLUME OF C.IN NaOH (ml) pH
^ ^ ' (TOTAL VOLUME OF O.lN NaOH + O.IN NaCl = 20 ml )
1. 0 2 .60
2 . 2 3.52
3 . - 4 .80
k, 6 6.22
5 . 8 6 .78
6. 10 6.90
7. 12 7.68
8. 14 8.70
9 . 16 9.30
10. 18 9.80
1 1 , 20 10.06
K Values d
Distrll)ution coefficient values for various anions and
cations were determined by batch process. A known amount of
cation or anion solution was shaken for six hours at room
temperature with 0.5 g of the exchanger in a conical flask
containing the solutions in which its distribution studies were
64
desired to be made. The total volume of the equilibrating
mixture was maintained at 50 ml. The liquid was drained off
and its cation/anlon content was determined. -The K, values a
were then determined by the formula
Amount of cation/anlon in the solution phase d " Amount of cation/anlon in the exchanger phase
The results are presented In Tables X and XI.
65
TABLE X
DISTRIDUTION COEFFICIENT VALUES OF SOME ANIONS
ANIONS
NO^
NO"
C l~
Br"*
l "
SO^"
SO^"
A s O j "
AsO"
l o ;
BrO^
S2O3
SCN"
Cr^l' 2 -
WO4
Moof
VO3-
Fe(CN)^"
H.r
1
METHOD OF DETERMINATION
S p e c t r ,
S p e c t r ,
T l t r ,
T i t r .
T i t r .
T i t r .
T i t r .
l o d . T i t r .
S p e c t r ,
l o d . T i t r .
l o d . T i t r .
l o d . T i t r .
S p e c t r ,
T i t r .
S p e c t r ,
S p e c t r .
S p e c t r ,
S p e c t r .
S p e c t r ,
1
DE IONIZED l ATER
T.A.
400
2400
2800
3100
16S0
1440
2049
2296
ilOO
156
85
720
T . A .
585
T .A .
442
714
340
^d 1
O.OOIM NH.OH
4
2000
165
1992
2120
2052
436
1020
1150
1164
842
26
10
529
2811
446
3242
32
512
116
ml g "
1
O.OlM NH^OH
940
38
728
948
1012
230
156
609
522
491
06
00
321
852
319
1086
15
328
42
1
O.IM NH^OH
28
06
102
86
495
112
60
3^9
310
226
00
00
206
224
216
156
00
164
00
1
O.IM HCl
T .A .
380
2400
2394
2843
1290
1320
1922
1984
988
180
78
688
T . A .
476
T . A .
591
7^0
290
66
TABUE XI
DISTRIBUTION COEFFICIENT VALUES OF SOME CATIONS
METAL IONS
Cu(ll)
Fe(lII)
Ni(ll)
Co(ll)
Pb(Il)
Cd(ll)
ng(ii)
Ag(l)
Sr(lT)
U02(II)
Mg(ll)
Ba(ll)
Ca(ll)
Separati
t
DEIONIZED WATER
800
T.A.
21
h-55
863
319
165
761
250
6 18
260
110
3k2
on
1 1
O.OOIM HNO^
468
3^0
18
313
30
22
105
252
92
3 2
150
103
220
^d 1
0 .OlM HNO^
335
78
13
268
28
6
63
182
64
221
00
kO
119
ml g-^
f
O.IM HNO
93
k
2
103
20
00
45
74
38
89
00
2
82
1
O.OlM NH^OH
90000
T.A,
59
4800
8421
27
185
1292
143
7952
280
400
480
1
O.IM Nil, OH
4
T.A.
T.A.
637
5688
9200
419
1440
2281
290
8836
300
630
596
1
O.OlM NaNO,
600
T.A.
782
532
8000
302
196
820
211
630
460
108
390
The separation of anions/cat lons with appreciable
d i f ferences in t h e i r K values were t r i e d . 2 g of thorium
67
tellurite was talcen on a glass wool support In the glass
columns having a height 50 cm and diameter 0.69 cm. The
column was washed thoroughly with deionized water and a
mixture containing known amounts of anions or cations to bo
separated was passeil through the exchanger bed at a very-
slow rate. Repeated recyclization of the mixture was done
to allow adequate adsorption of the anions/cations. The
elutlon was then done by the solutions in which the K values
were lowest. In the eluted fractions the qualitative tests
for both the components were performed. The results are
plotted from Figures 3a to 7.
6
o
o o
001 M NH4OH
•< >-
H2O 0-1MHN03
200
OOIMNH4OH H2O 0-1MHNO
0 40 80 120 160 200
VOLUME OF EFFLUENT(ml)
FIG.3.(a) SEPARATION OF Hg(ll) FROM Cu(ll) (b).SEPARATION OF Ni ( ID FROM Cudl)
69
0-1MHN03
80 120 160 200
o
CM O
o O-OIMNH^OH H,0
.4 ^ 0-1MHN03
VOLUME OF EFFLUENT(ml)
FlG.4.(a) SEPARATION OF Cddl) FROM Pb(ll) (b) SEPARATION OF Hg(ll) FROM UO^ (ID
a.
z o
0-001MNH40H H9O 0-1MNH40H 70
400-
300-
200-
100-
20 40 60 80 100 120 140
O 0-001MNH40H
L< ^ 0-lM NH4OH
20 40 60 80 100 120 140
VOLUME OF EFFLUENT(ml)
FIG.5. ( a ) SEPARATION OF NO2 FROM N0""3
( b ) SEPARATION OF PO^" FROM M 0 O 4 '
71
O-OOIMNH^OH HjO OOIMNH4OH
o 2 <
o
20 40 60 80 100 120
O-OOIMNH^OH H2O O-IMNH^OH
20 AO 60 80 100 120
VOLUME OF EFFLUENT(ml)
2 -FIG.6. (a) SEPARATION OF V O 3 FROM M 0 O 4
(b) SEPARATION OF SgO^" FROM SO4"
72
H2O OlMNH^OH
o» 400
20 40 60 80 100 120
VOLUME OF EFFLUENT (ml)
FIG.7. SEPARATION OF Br03 FROM Br"
73
DISCUSSION
The exchanger , thorium t e l l u r i t e i s b e s t prepared
when i t s ac id c o n c e n t r a t i o n was maintained a t pH 1 as sho^vn in
Table I I I , The exchanger so, prepared sample I I not only gave
a good y i e l d hut a l s o b e t t e r chemical s t a b i l i t y and, t h e r e f o r e ,
sample I I was taken for the d e t a i l e d s t u d i e s .
The r e s u l t s of the ion exchange c a p a c i t y of thorium
t e l l u r i t e a re shown in Table IV. The anion exchange c a p a c i t y -1 -1
v a r i e s from 0 .8 m.eq.g t o 1.4 m.eq.g . The m a t e r i a l pos se s se s a high a f f i n i t y for Oli" as i s ev iden t from the f ac t
- 1 t h a t r e l e a s i n g capac i t y for OK i s only 0.60 m.eq.g while
t h a t for i t s uptake i s 1.4 m.eq .g" . This shows t h a t thorium
t e l l u r i t e a c t s as a weak base in 0H~ form.
Although the exchanger , thorium t e l l u r i t e lacked a H
l i b e r a t i o n c a p a c i t y i t shows s t rong uptake fo r c e r t a i n meta l
i o n s . Table IV a l s o shows the r e s u l t s of the so rp t ion c a p a c i t y
f o r some of the b i - and t r i v a l e n t metal i o n s . The so rp t i on
c a p a c i t y v a r i e s from 0.68 t o 0.84 m.moles g" , Strong adherence
of some of the metal ions t o the exchanger frame work makes i t
an ext remely usefu l m a t e r i a l fo r t he l igand exchange s t u d i e s
in ammonium hydroxide medium - one of the moat widely used
e l u e n t for l i gand exchange chromatographic s t u d i e s .
The r e s u l t s of the e f f e c t of drying tempera ture on the
ion exchange c a p a c i t y of thorium t e l l u r i t e shown in Table V
74
reveal tha t the exchanger shows no de te r io ra t ion in i t s exchange
behaviour upto 150 C, but the anion exchange capaci ty decreases
appreciably vhen the drying Is done above t h i s temperature.
The r e s u l t s of d isso lu t ion of thorium t e l l u r i t e in
d i f fe ren t concentrations of ac ids , base and neu t r a l solut ions
are shown in Table VII. I t can be seen that the mater ia l i s
s table in aqueous ammonia upto hU; In IICI and IINO, upto IM,
Concentration of neutral solut ions and nou-aqueous solvents
have no effect on the s t a b i l i t y of the exchanger. Higher
concentrat ions of strong acids and strong bases , however,
cause appreciable dissolut ion of i t s cons t i t uen t s .
The r e s u l t s of the chemical composition of the exchanger
from Table VI shovred tha t thorium and tel lur ium are present in
the ra t io Th:Te as l s 2 . Shown in Figure 2 are the pll t i t r a t i o n
curves for anion as well as ca t ion exchange behaylour on thorium
t e l l u r i t e . A c lea r bl funct ional cat ion exchange behaviour i s
observed in NaOH medium while i t s behaviour as an anion exchanger
i s not c lear In the acidic medium.
The r e s u l t s of the d i s t r i b u t i o n s tudies for various
anions and cat ions are presented in Tables X and XI. I t can be
seen from these t ab les tha t K values for both anions as well as
cat ions decrease with increase in the concentration of the
equi l ib ra t ing so lu t ion . K^ values were the highest In water
medium. I t can a lso be seen tha t almost a l l the anions exhibi t
75
greater adsorption In O.lN IICI. This shows that unlike most
of the other known Inorganic ion exchangers, thorium tellurite,
shows anion exchange behaviour in acidic medium. The lower
C values of various anions in aqueous ammonia is, probahly,
due to the greater preference of the exchanger for OH" ions
than for all other anions. Thorium tellurite sei'ves as a
cation exchanger in the basic mediiim and hence the cationlc
uptake In O.OlN NaOH was higher than that in water medium.
With Increasing concentration of acid the desorption of metal
Ions increased.
On the basis of large differences in K^ values various
separations of anions and cations have been tried. Separation
of Cu(ll) fromHg(ll), Cu(ll) from Nl(ll), Vb(Il) from Cd(ll)
and UOgCll) from Hg(Il) have been successfully achieved and the
order of elution and eluents used are shown in Pigs. 3a-4b-
The successful separations of anions are NO- from NOgJ MoOj^"
from P0^~; V0~ from MoO^~; SO^" from S^O," and BrO^ from Br"".
The order of separations are presented in Figures 5a-7.
76
REFERENCES
1 . P o l l a r d , F . H . , N lck l e s s ,G . and Rothwel l ,M,T, , J .Chromatog . ,
10, 212 (1963) .
2 . Brown ,L .C , Begum,G.M, and Boyd,G.E., J .Amer .Chem.Soc,
9 1 ( 9 ) , 2250 (1969) .
3 . Kraus,K.A, , P h i l l i p s , H . O . , Car l son ,T .A, and J o h n s o n , J , S , ,
Proc .2nd .Tnt .Conf ,Peacefu l Uses of Atomic energy , Geneva,
28 , 3 (1958) .
k, B r l t z , B . and Nanco l l as ,G .H, , J . Inorg .Nuc l .Chem; , 3 1 , 3861
(1969) .
5 . Al>e,M. and I t o , T , , Nippon Kagaku Z a s s h i , 86, 817 (1965) .
6 . VenIcataramani,B. and Venkateshwar lu ,K,S, , J . I n o r g . N u c l .
Chem., 42 , 909 (1980) .
7 . Rawa t , J ,P . and I q b a l , K . , Annali Dl Chlmica, 69, 241 (1979) .
8 . Neu8s,R, and Naiman,B., " Q u a n t i t a t i v e Analysis '* , 3rd Edn.
McGraw H i l l , New York, p . 70 (1962) .
9 . Furraan,N.H,, Standard methods o f Chemical A n a l y s i s , Vol , I ,
VI Edn. D.Van Nostrand C o . I n c . , P r i n c e t o n , New J e r s e y ,
932 (1962) .
10. S n e l l , P . D . , S n e l l , C . T , and S n e l l , C , A . , Co lo r ime t r i c ne thods
of a n a l y s i s . Vol . I IA, D.Van Nostrand C o . I n c . , P r i n c e t o n ,
N . J . , p . 683 (1959) .
1 1 . Topp,H.E. and Pepper ,K.V. , J .Chem.Soc. , 3299 (1949) .
CHAPTER-III
SYNTHESIS AND PROPERTIES OF THORIUM TRIETHYLAMINE
AS A NEW ANION EXCHANGER
77
Aflams S. Holmes in t h e i r f i r s t patents (1) described
anion exchange res ins along with the cation exchangers. These
anion exchange res ins contained ivealc base amino groups where
the amine group works as a source of posi t ive fixed charge.
The l a t e r studies revealed tha t the stronnr hase exchange to
res ins are based upon quaternary ammonium groups (-NR ) where
R may he methyl, ethyl or other organic subs t i tuen t s (2) .
Strong base ion excban^fei-s are based on diethanolamine a l so .
The anion exclinn'^e res ins have limited appl ica t ions
at higher temperatures and in presence of ionizing rad ia t ion .
Therefore, to overcome these l imi ta t ions e f fo r t s were made
to develop inorganic ion exchanp;ers. In the continued effort
to obtain such nev inorganic anion exchangers with grea ter
s e l e c t i v i t y , g rea te r thermal s t a b i l i t y and g rea te r res is tance
for ionizing rad ia t ion , the hydroxides of ce r t a in metals
were f i r s t t r i e d . The hydroxides of I I I group and TV group
metals like Sn(IV) (3), Zr(lV) {k), Al(lIT) (5) and few others
(6-7) have been found to show anion exchange behaviour only
a t lower pH values . These mater ia ls found limited use at
higher pll va lues . To overcome such l imi ta t ions e f fo r t s are
made to develop some anion exchangers based on metal hydroxides
with amino groups. The introduction of tr iethanolamine was
made for the preparation of such an inorganic ion exchanger (8) .
As strung base cxchan'^ers can be pre pare 1 by the use of
t e r t i n i y alkyl amines, therefore , t r iethylamine based Inorganic
78
anion exchangers are being explored In this work i.e. thorium
trlethylamine mentioned In this chapter and zirconium
trlethylaraine in the next.
An advantage in introducing amine group is also
observed for its chelate formation with the metal ions. By
introducing a chelating group in the matrix of the inorganic
Ion exchangers It Is possible to synthesize chelate Ion
exchangers which have high selectivity, high capacity and
fast kinetics giving rapid equilibration with metal containing
solutions. The preparation of such Inorganic mixed organic
chelate Ion exchangers with desirable chemical and physical
properties can be explored in future. Furthermore, such a
material will be of great use in extraction of metals over
the process of conventional solvent extraction which becomes
uneconomic In handling large volumes of solutions with low
concentrations of metal, A suitable chelating exchanger with
high selectivity may be developed and applied for this purpose,
They may also be used in the metal recovery - regeneration
process for several times with a very little (or no decrease)
In Ion exchange capacity.
In the present work the material thorium trlethylamine
has been studied, at the first level, to behave as a new
Inorganic anion exchanger, to develop some analytically
important separations of anions and to propose Its utility
as a chelating material for uptake of Cu(ll), Composition
79
determination and I.R, studies are made to characterize the
ion exchanger formed.
80
EXfERTMENTAL
Apparatus
Bausch and Lomb s p e c t r o n i c 20 (U.S.A.) for spec t ropho to -
metrlc determinations, E l ico pH meter model Ll-10 (India) for
pH measurements and an e l e c t r i c temperature control led SICO
shaker lo r shaking purposes were used.
Reagents
Thorium n i t r a t e (B.D.H.), t r le thylamine (E.Merck) were
used. Other chemicals were of ana ly t i ca l ly purif ied grade.
Synthesis
Thorium trlethylamine was prepared by mixing 0.1
molar solution of thorium nitrate and 0.1 molar solution of
trlethylamine in the volume ratio of 1:4. The precipitate
prepared in this way was kept standing for 2k hours at a
temperature 25 C +_ 2, The precipitate was filtered and then
washed with deionlzed water. The precipitate was kept in
the oven at 40 C till completely dried. It was then kept in
the air for 6 hours and then It was immersed in deionlzed
water. On Immersion, the exchanger broke down into smaller 0
p a r t i c l e s . I t was f ina l ly kept In the oven at 40 C for
drying. The exchanger p a r t i c l e s were then converted in to
n i t r a t e form by putting the ion exchange p a r t i c l e s in 1 molar
solution of sodium n i t r a t e for 12 hours In te rmi t t en t ly
81
replacing the supernatant liquid with a fresh solution of
sodium nitrate. Table XII shows the mixing ratios of
thorium nitrate and triethylamine and the nature of the
precipitate.
TABLE XII
CONDITIONS OF PREPARATION OF THORIUM TRIETHYLAMINE EXCHANGER
SAMPIES
S 1
S 2
S 3
S 4
S 5
1
CONDITIONS
MaLARITY OF
Th( lV) n i t r a t e
O.IM
O.IM
O.JM
O.IM
O.IM
OF SYNTHESIS
' REAGENTS t
T r i e t h y l amine
O.IM
O.IM
O.IM
O.IM
O.IM
1
MIXING VOLUME RATIO
Th:Amine
1:1
1:2
1:3
1:4
1:5
• NATURE OF PRECIPITATE
No precipitate
Precipitate appears but dissolves
-do-
A thick precipitate
Precipitate occurs
s 6 O.IM O.IM 2:1
but disappears on shaking
No ppt
82 RESULTS
Anion exchange c a p a c i t y
The a n i o n exchange c a p a c i t y of t h o r i u m t r i e t h y l a m i n e
was d e t e r m i n e d by column m e t h o d . One cram e x c h a n g e r was t a k e n
In a g l a s s column measur ing 20 cm in l e n g t h and h a v i n g 6 mm
d i a m e t e r . G l a s s wool was put in t h e b o t t o m of t h e column a s
t h e s u p p o r t . I o n - e x c h a n g e r was c o n v e r t e d in t h e d e s i r e d form
( c h l o r i d e , b r o m i d e , i o d i d e , t h i o s u l f a t e , c h r o m a t e , d i c h r o m a t e )
by t r e a t i n g w i t h 1 molar s o l u t i o n s of s o d i u m / p o t a s s i u m s a l t s
of d i f f e r e n t a n i o n s . The column was washed w i t h d e i o n i z e d
w a t e r c o m p l e t e l y t o remove t h e e x c e s s of a n i o n s . The e l u e n t
used was 1.0 m o l a r sodium n i t r a t e s o l u t i o n and t h e r a t e was - 1
m a i n t a i n e d a t 0 . 5 ml min . T a b l e X I I I shows t h e a n i o n
exchange c a p a c i t y f o r d i f f e r e n t a n i o n s . Anion exchange
c a p a c i t y of h a l i d e i o n s i s p l o t t e d a g a i n s t i o n i c r a d i i ( P i g . 8)
TABLE X I I I
ION EXCHANGE CAPACITIES OF THORIUM TRIiCTIIYLAMINE
FOR DIFFERENT ANIONS
SL, NO.
1 ,
2 .
3 . k.
5. 6, 7.
ANIONS
C h l o r i d e
Bromide
I o d i d e
T h i o s u l f a t e
Chromate
D i c h r o m a t e
C o p p e r ( T l )
SALTS TAIffiN CAPACITY (meq/gm)
Sodium chloride
Potassium bromide
Potassium iodide
Sodium thiosulfate
Potassium chromate
Potassium dichromate
Copper nitrate
0.68 0.61 O.'J.e 0.58 1.85 3.10 0.10^
Sorption capac i ty .
83
Sorption capacity
One gram of the exchanger was taken in the column with
glass wool support, 10 ml of O.OlM copper n i t r a t e solut ion
was added over the column at a flow ra te of 0.5 ml/mln. The
effluent was then t i t r a t e d and the amount of copper ions was
quant i ta t ive ly determined. A fresh sample of 10 ml of O.OlM
copper n i t r a t e was added over the column and effluent was
t i t r a t e d against 0,01 molar EDTA solution using buffer of
pH 3.6 and PAN ind ica to r . By suhstract ing the volume of ET>TA
t i t r a t e d against eff luent from the volume of EDTA consumed
for 10 ml of O.OlM solut ion and then adding a l l these values
for each operation, the sorption capacity was ca l cu l a t ed .
Sorption capacity for copper(II) was found to he O.lO meq/gm.
Recycligation
For recycl iza t ion the exchanger weighing one gm
was converted in chromate form by IM potassium chromate solution,
To the column, the exchanger in chromate form was added. After
completely washing the exchanger with delonlised water, the
anions were eluted with IM sodium n i t r a t e so lu t ion . This
cycle was repeated for five t imes . The r e s u l t s are presented
in Table XIV and Figure 9,
84
u < " a ,-< «
o z <
o X ixl
E
E
'E > cr I - «
o — UJ
U Q:
2£
0-7
o^e
0-5
0-4
0 3
0-2
0-1
0-0 1-70
F IG.8 .
.J - I \ I 1-80 1-90 2-00
IONIC RADII
2-10 2-20
ION E X C H A N G E C A P A C I T Y AGAINST IONIC RADII (FOR HALIDES )
2'Oh
1-5
1-0
0-5
0-0 ± X ± I II III IV V
NUMBER OF CYCLES
FIG.9 PLOT OF ION E X C H A N G E CAPACITY AGAINST NUMBER OF R E G E N E R A T I O N CYCLES
85
TABLE XIV
ION EXCHANGE CAPACITY OF THE EXCHANGER
FOR FIVE CYCLES
NU>fBEH OF CYCLES ION EXCIlANGii CAPACITY (meq gm"^) FOR CHROMATE IONS
I 1.85
I I 1,80
I I I 1.70
IV 1.6^
V 1.60
Anion exchange c a p a c i t y a s a f u n c t i o n of c o n c e n t r a t i o n of e l u t t n ^
r e a g e n t
Ion exchange c a p a c i t y of most of t h e i n o r g a n i c ion
e x c h a n g e r s I s d e p e n d e n t t o some e x t e n t on t h e volume and
c o n c e n t r a t i o n of e l u e n t bein,<?; Aveak c a t i o n o r a n i o n e x c h a n g e r .
The optimum c o n d i t i o n s f o r t h e c o n c e n t r a t i o n of e l a t i n g r e a g e n t
was d e t e r m i n e d hy f i r s t t a k i n g 1 gra t h o r i u m t r i e t h y l a m l n e in
c h r o m a t e form. Sodium n i t r a t e of O.OlM, 0.05M, O.lM, 0.5M,
l.OM, 1.50M, 2.0M, 2.50M and 3.0M c o n c e n t r a t i o n s w e r e used a s
e l u e n t s . The e l a t e d ch romate s o l u t i o n was t i t r a t e d a g a i n s t
O.OlM sodium t h i o s u l p h a t e s o l u t i o n . The t o t a l volume of
86
e f f l u e n t was f i x e d a s 300 m l . The r e s u l t s a r e summarized
In T a b l e XV and p l o t t e d in F i g u r e 1 0 .
• TABii: XV
ION EXCHANGE CAPACITY AS A FUNCTION OF CONCENTRATION
OF ELUTING liJ:-AGLNT
SL. CONCENTRATION OF KNO^ ION EXClUNGE CAPACITY
( M o l a r i t y ) (meq.gro"" )
1 . 0 . 0 1 0 . 8 0
2 . 0 . 0 5 0 . 9 5
3 . 0 . 1 0 1.00
4 . 0 . 5 0 1.05
5 . 1 .00 1.08
6 . 1.50 1.10
7 . 2 . 0 0 1.10
8 . 2 . 5 0 1.10
9 . 3 . 0 0 1.10
Heating effect
Thorium trlethylamlne was heated in a muffle furnace
at different temperatures for k hours. The capacity of the 0 0 0 0 O
e x c h a n g e r was d e t e r m i n e d a t 60 C, 100 C, 200 C, 300 C and hOO C
1-2
87
1-0
&
E r 0-8
< Q. < o ui o z < X o X UJ
z o
0 - 6 -
0-4
0-2
FIG. lO.
I 0-5
± X _ X -3-0 1-0 1.5 2-0 2-5
MOLAR CONCENTRATION OF KNO3
ION EXCHANGE CAPACITY AS A FUNCTION OF CONCENTRATION OF ELUENT
88
r e s p e c t i v e l y . Table XVI g i v e s the c a p a c i t i e s a t d i f f e r e n t
t e m p e r a t u r e s . Resul t s a re p lo t t ed in F igure 1 1 .
TABLE XVI
CAPACITY AT DIFFERENT TEMPERATURES FOR DICHROMATE IONS
SAMPLE NO. ' TEMPERATURE ' CAPACITY
(C ) (meq/gm)
1 ^0 3 .10
2 60 3.10
3 100 2.13
4 150 1.12
5 200 0.10
6 300 0 .09
The r e s u l t s of weight l o s s a t d i f f e r e n t t empera tu re s
are presented in Table XVII. The percent weight l o s s v e r s u s
tempera ture p lot i s given in F igure 1 2 .
89
I £
cr
E
>-
(3 < a. <
100 150 200 250
TEMPERATURE ( **c)
FIG.II. PLOT OF CAPACITY AGAINST TEMP ERATURE
90
16k
u-
12
tf) 10 if) o
X 8
100 200 _J 300
_JL 400
TEMPERATURE
FIG-12. THERMOGRAM OF THORIUM TRIETHYLAMINE EXCHANGER
91
TABLE XVII
VEIGITT LOSS OP TIIE EXCHANGER AT DII-TERENT TE>fK:RATUHES
SAMPLE NO.
1
2
3
k
5
1 t
TEMPERATURE
0
(C)
100
150
200
300
400
WEIGHT TAKEN
(gm)
0 .500
0 . 5 0 0
0 . 5 0 0
0 . 5 0 0
0 . 5 0 0
1
\iE IGHT FOUND
(gm)
0 . ^ 3 8 1
0 . 4 3 3 0
0 . 4 3 2 5 .
0 .4316
0 .4292
1
WE IGHT LOST
( p e r gram e x c h a n g e r )
0 . 1 2 3 8
0 . 1 3 4 0
0 . 1 3 7 5
0 . 1 3 6 8
0 . 1 4 1 6
Chemical s t a b i l i t y
The chemical s t a b i l i t y of tliorluni t r le thylamlne was
determined by shaking 0,5 graa of exchanger for four h r s in
d i f f e ren t solut ions in which i t s s t a b i l i t y was to be checked.
In the supernatant l i qu id , the amount of thorium was determined
by t i t r a t i n g a known volume of solution against 0.02 molar
EDTA solution while tr iethylamine was determlnerl in another
known volume of sample spectrophotometrically by Ninhydrin
(9 ) . Results are presented in Table XVIII.
SL. NO.
92
TABlii XVIII
STABILITY OF THORIUM TniETIlYLAJITKh; EXCHANGER
SOLVENT SYSTEMS SOLUBILITY (mg/50 ml)
Thor iun i ( lV) T r i e t h y l a m l n e
1 , D e i o n i z e d w a t e r
2 , H y d r o c h l o r i c a c i d (O.IM)
3 , S u l f u r i c a c i d (O.IM)
k. N i t r i c a c i d (O.IM)
5 . P o n n i c a c i d (O.IM)
6 . A c e t i c a c i d (O.IM)
7 . Sodium h y d r o x i d e (IM)
8 . Ammoniura h y d r o x i d e (IM)
9 . Sodium n i t r a t e (IM)
1 0 . E t h y l a l c o h o l
1 1 . P e r c h l o r i c a c i d (O.IOM)
1 2 . H y d r o c h l o r i c a c i d (O.OlM)
0 , 0 0
1 0 . 2 0
1 8 . 0 0
^ . 5 0
0 . 3 0
1 .00
0 . 0 0
0 . 0 2
0 . 0 0
0 . 0 0
5 .00
0 . 0 0
0 . 0 0
1 6 . 0 0
4 0 . 0 0
1 0 , 0 0
1 ,10
2 . 3 0
0 . 0 0
0 . 0 5
0 . 0 0
0 . 0 0
1 1 . 3 0
0 . 0 0
Composition
1 gm of the exchanger was dissolved in 25 ml of
conc.HCl. Heating was avoided in preparing the solution. The
volume was made upto 100 ml with deionized water. The amount
93
o l thorium was determined by t i t r a t i n g against O.OIM EDTA
solut ion using Cu-Pan Indica tor . Trlethylamine present In
another sample was determined spectrophotometrically toy
Nlnhydrln. The r a t i o of thorium and t r le thylamine in the
exchanger was found to he 1:3.
I .R . Studies
For charac te r iza t ion of the exchanger, I .R, s tudies
were made. The spectrum was observed by using KBr d i s c . The
r e s u l t s are given in Figure 13,
Potentioroetrie t i t r a t i o n s
Potentlometrie t i t r a t i o n s were performed by Topp and
Papper method (10) . 0,5 gni of the exchanger was shaken with
the solution of O.OIM HCl and 0,01M NaCl. The t o t a l volume
of the reaction mixture was kept 50 ml In a l l the c a s e s .
The pH of the so lu t ions , a f te r equ i l ib ra t ion for four h r s ,
were then determined. The r e s u l t s are plotted in Figure 1^,
K, values
Dis t r ibu t ion s tudies for anions were detennined by
batch process, 1 ml of anionic solution was taken in a 50 ml
standard f lask . The remaining volume of the f lask was f i l l ed
up with delonized water or d i f ferent concentrat ions of sodium
hydroxide, the so lu t ions in which the K, values were t o be
94
Q: ijj
O z < X
u X LU LU
z
< -J >-I h-cr h-
D GC O X h
O
D QC H O LU OL
C/) •
£2 g Lu
( •/•) 33NVi i lWSNVdi
o in
in •4-
o
in CO
o CO
in CM
O I Z r— o • o U-o UJ
s
o >
I
> X f -UJ
cc \-
D
CC o I H cr O U-
UJ > cc D u z o I-< cr H
95
l-
u nr 1-UJ ? O H Z UJ
O a.
cr ULI
O z <
I o X UJ
III z 5 <
o
96
s tudied . The solut ions were then t ransfer red in 250 ml
Erlenmeyr flasSts, The exchanger weighing 0.5 gram was
then added t o each f lask . These f lasks were then shaken for
4 h r s in a shaker to a t t a i n equilil3rium. The amounts of
anions before and a f te r equ i l ib ra t ion were then determined.
Dis t r ibu t ion coeff icient values can be determined by using
the formula-
I - F Volume of solution d F Weight of exchanger
where I and P are the i n i t i a l and f inal volumes of t l t r a n t
before and a f t e r equ i l i b r a t i on . The r e s u l t s of K, values
of some common anions are presented in Table XIX.
97
TABLE XIX
DISTRIBUTION COEFFICIENTS OF SOME ANIONS ON
THORIUM TRIETHYLAMINE EXCHANGER
SL. NO.
1 .
2 .
3 .
h.
5.
6 .
7 .
8 .
9 .
1 0 .
1 1 .
1 2 .
1 3 .
1 4 .
1 5 .
1 6 .
i
ANIONS
C h l o r i d e
Bromide
I o d i d e
T h i o c y a n a t e
B i c h r o m a t e
T h i o s u l f a t e
Chroraate
l o d a t e
F e r r l o y a n i d e
S u l f i t e
Bromate
P e r s u l f a t e
A r s e n i t e
P e r r o c y a n i d e
Vanada t e
Phospha te
t
HgO
2^10
5^0
438
358
T . A .
T . A .
T . A .
1340
T .A .
933
2062
1042
1933
T .A .
T .A .
T . A .
K^ a
10 M NaOH
168
540
438
293
T . A .
T .A.
T .A.
1100
T.A.
930
2062
1042
1930
T . A .
T . A .
T . A .
VALUES
1
10"^M NaOH
155
392
258
244
T . A .
T . A .
T . A .
744
850
786
919
567
1425
1205
900
1500
10"^M NaOH
104
178
54
28
270
217
402
loo
500
77
44
233
1120
400
305
256
• io"Si NaOH
34
18
13
04
02
08
04
00
00
02
00
00
335
150
98
04
T.A. = Total adsorption
98
Quanti tat ive separations
On the Ijasls of large differences in K . values many
ana ly t i ca l ly Important separat ions of anions were t r ied and
achieved, 2.00 gm of anion exchanger (150-200 mesh size) in
n i t r a t e form was placed in a g lass column f i t t e d with glass
wool. A mixture of anion solut ions was then poured into the
column. The solut ion was passed through the column a t a
slow ra te to ensure complete adsorption of anions . These
anions were adsorbed at the top of the exchanger bed forming
i n i t i a l zone. The f rac t ions of 10 ml e lu t e were then -1
col lected at a flow rate of 0.5 ml min throughout e lu t lon
process. The column was washed with deionized water . The
anions were eluted by appropriate e lu t ing reagent . The anions
were determined by known methods. The e lu t i ng f ract ions were
having only one component of the mixture. Separations of - - 2 - 2 - - - - Z
I and Br from CrO. and CrgO , I and Br from VO and PO^, . . 2- 5"" - 2 -
SCN and I from CrgO- and Fe(CN)g and I from S^O. were
successfully achieved. Figures 15-19 represent the e la t ion
curves for the separat ion of anions and Table XX gives the
quant i ta t ive separation of anions on exchanger columns.
,
I
o o z 2 t—
6
O' 04
I '
X ' o o z z ^ o o o o ,
I
'
' k
'
y^
n
1 • ^ o O ^M
1 1
1 1 -
CD j^'-"'^
1 1 1 •
-
^ X * * ^ •"
^ ^ _
o o
o
o Psl
99
i
X
o o 2 5 *
o
^ O i
<^J X ' X i
o o z z r-o o o •
o '
1
' ,
' .
'
u ^^
) 1 > *
o
1 1
.
»-• ^ _^^--^
• « = = : ^ ^ 1 1 r-—n
• •
-
7 f 1 ^
J m — X fT i V——
o <ti
o sf
o
o o CM
o
o C>4
"E N-*»
1 -
z UJ 3
u. u. Ui
u.
o Ul z 3 - 1
o >
' ^ O u
O 5 O QC U.
1 • — •
\x.
o z o H < Q: < Q. UJ to
'-'
I'? o t_
u 5 O cr u.
' t _ CD
L-
O z o — H < QC < Q. UJ
(/)
.—
o 00
o
o tM
o o CM
o o (M
o o
o x>
6
C iuj)iNVbiii wioo JO awmoA
100
o 00
o
o
o o
o (£> r—
o CM
E i-
z 3
U.
u. UJ ll.
o UJ 2 3 -J
o >
1 r> O
o 5 O Q: Li. 1
u. O z o """" h-< QC < CL UJ C/) —.
o
.1 r-
O 1 li U
5 O LL,
CD
ll
O
z o «— H < cc < CL UJ if) ,_,
o
o 00
o «4-
6
C )UJ) iUVtilil WtO-0 do 3WmOA
101
40 80 120 160 200
VOLUME OF EFFLUENT(ml)
FIG.I7 (a) (b)
SEPARATION OF T FROM V O j SEPARATION OF Br* FROM PO4 3-
3 0-40
z <
k-
o 6 u. o UJ
o >
0-1M NaOH
0-80-
0-40
240
40 80 120 160 200
VOLUME OF EFFLUENT(ml)
FIG.I8.(a) SEPARATION OF SCN~FROM C r g O ^ "
(b) SEPARATION OF I " FROM CFeCCN)^] 3 -
103
« r f
£
z 1*20 < a:
S 0-80
o
° OAO
O-OOOlMNaOH
_ r \ /v
H;?0 0-1M NaOH
s2or
1 r ^ 1 0-40 0-80 1-20 1-60 2-00
VOLUME OF EFFLUENT (ml)
FIG. 19. SEPARATION OF I FROM S2O3 2 -
104
TABLE XX
QUALITATIVE SEPARATION OF ANIONS ON
THORIUM TRIETIIYLAMINE EXCHANGER
SL. NO.
1 .
2 .
3 .
4 .
5.
6.
7.
8 .
9.
f
MIXTUIffi
l "
CrO^"
B r "
C r o ; -
I "
C r ^ o "
B r "
Cr^O^"
l "
vo; Br"
3 -
SCN"
C r ^ o " "
l "
F e ( C N ) ^ '
I ~
S g o ; -
1
ELUENTS
O.OOIM NaOH
O.IM NaOH
G.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOOIM Naon
O.IM NaOH
O.OOOIM NaOH
• O.IM NaOH
O.OOOIM NaOH
O.IM NaoH
1
ELUATE
(ml)
80
loo
80
90
80
110
80
110
100
100
90
90
90
120
80
110
80
80
1
AI'fOUNl L0AT)ED
(rag)
2 .667
11 .078
2 . 6 4
11 .078
2 .667
13 .068
2 . 6 4
1 3 . 0 6 8
2 . 1 0
4 . 2 7
2 .64
4 . 5 6
1.595
13 .068
2 . 6 6 7
8 .586
2 . 6 6 7
3 . 1 9 2
1
AMOUNT FOUND
(Mg)
2 . 5 4 0
10 .904
2 . 4 8
1 0 . 8 4 6
2 . 4 7 6
1 2 . 7 4 4
2 . 5 2
12 .852
2 . 0 0
4 . 0 0
2 . 5 2
4 . 2 0
1.450
12 .744
2 .476
8 . 2 6 8
2 .540
3 . 0 8
1
1o ERROR
4 . 7 6
1.57
6 . 0 6
2 . 0 9
7 .16
2,i»8
4 . 5 4
1.65
4 . 7 6
6 .32
4 . 5 4
7 .90
9 .09
2 . 4 8
7 . 1 6
3 . 7 0
4 . 7 6
3 . 5 0
105
DISCUSSION"
The r e s u l t s suraraarized in Table XIT inrJlcate t h a t
a complete p r e c i p i t a t i o n of thorium t r i e t h y l a m i n e occurred only
when the metal t o amine r a t i o was maintainerl a t 1 : ^ . Any s
a l t e r a t i o n in t h i s r a t i o e i t h e r die! not allow t o p r e c i p i t a t e
formation or i f formed then t! e d i s s o l u t i o n a f t e r s tanding or
shak ing . The m a t e r i a l behaves as an anion exchanger (Table X I I l )
I t i s l i k e l y t h a t t l ie incorpora ted t r i e t h y l a m i n e
a c q u i r e s a f ree p o s i t i v e charge on i t s n i t r o g e n atom
C fU 2 5
N -— CgH-
S"5
i s r e s p o n s i b l e for i t s anion exchange c a p a c i t y . However, the
anion exchange capac i ty v a r i e s from 0JtS t o 3.10 for the an ions
t e s t e d . The v a r i a t i o n i s probably due t o the d i f f e r e n c e In
s e l e c t i v e uptake of d i f f e r e n t a n i o n s . For h a l i d e ions the o rder
can be given as Cl~ ^ Br"" > I " . This i n d i c a t e s t h a t the
c a p a c i t y dec reases l i n e a r l y as the ion ic s i ze i n c r e a s e s . Th i s
i s r ep re sen t ed by a p lot made in c a p a c i t y v s . ionic r a d i i
fo r t h e s e ions (Figure 8 ) .
A very high value of ion exchange capac i ty towards
106
dlchromate Ions (3.iO-n!eq/gm) i s in accordance with the r e s u l t s
of zirconia (11) showing high se l ec t i v i t y towards dichroniate.
As thorium an ! zirconium showjnany s imi lar proper t ies
therefore t h i s property i s l ike ly to he s im i l a r . Fur ther ,
our contention regarding the form.'t ion of t h i s type of exchanger
i s that the amine i s incorporated with tlie nietnl oxide forming
the matr ix .
Ifhen the exchanger a f t e r keeping in n i t r i c acid and
subsequent washing was kept in contact with sodium n i t r a t e
solut ion, i t failed to re lease H ions indicat ing tha t the
exchanger has no cation exchange capaci ty . This may be re la ted
to the pos s ib i l i t y t h a t there is no fixed negative charge with
the exchanger matr ix.
However, when the exchanger was placed in IM cupric
n i t r a t e solution for 18 hrs i t turned blue i . e . the sorption of
Cu(Il) Ions took place (Table XIII) but the sorption capacity
was poor as compared to i t s anion. The sorption of Cu(IT) ions
by thorium triethylamine a lso suggests the presence of nitrogen
atom of amine group (-N-) that offers s i t e s for the complex
formation with the metal ion. As complex fozmation is a highly
specif ic in terac t ion which Is further influenced by the Ion
exchange phase, the re fore , the bond formed by the in te rac t ion
of copper(lT) with amine in the exchanger phase i s very strong
and can not bo broken by simple complexing agents . However,
when EBTA is used as eluent i t showed the release of copper (IT)
107
Ions. This Is because ET)TA being a higher complexing agent
(chelating agent) than trlethylamine, is capable of releasing
Cu(ll) from the thorium trlethylamine phase. Therefore,
these materials can not compete with thv- Inorganic cation
exchangers in the physical and chemical stability.
The results of the composition studies reveal that
thorium and trlethylamine are present in the exchanger In the
molar ratio of 1:3•
The results of heating affect on capacity (Table XVI)
indicate that the capacity decreases as the temperature is 0 O
Increased above 60 C and is nearly l o s t above 200 C, In t h i s
respect the l imi ta t ion of using anion exchange res ins a lso
p e r s i s t s with thorium trlethylamine exchanger. The r e s u l t s
of Tabic XVII giving weight loss per gram of the exchanger
at different temperatures predict the losses of water and o o
amine molecules at 100 C and 200 C respec t ive ly . The weight
loss Is not appreciable at temperatures higher than 200 C
(Figure 12), These r e su l t s are in accordance with the
capaci ty as a function of heating temperatures (Figure 11) .
The Infrared absorption spectrum of thorium t r i e t h y l -
amine exchanger shown in Figure 13 indica tes the absorption
peaks a t t r ibu ted to various groups as follows: <"1
(a) A broad peak ranging from 3300-3600 cm is due to -OH stre tching v ib ra t ions .
108
(b) A medium peak due to C-II stretching vibration lies at
29^0 cm"^. - 1
(c) A strong peaic at 1380 cm is due to C-II bending v ibra t ions
and C-N v ibra t ions ,
(d) A strong C-C s t re tching vibrat ion i s observed in the
frequency range of 1620-1640 cm"" .
(e) A medium C-N bending frequency i s observed in the frequency -1
range of 1070-1080 cm
(f) Thorium-oxygen bending frequency is confirmed by the
medium peak in the range of 800-8^0 cm"" ,
From these observations i t i s quite c l ea r that the
ion exchanger, thorium tr iethylamine is s t i l l in possession of
amine group.
The potentlometric t i t r a t i o n curve plot ted in Figure 14
reveals that the exchanger behaves as a monofunctlonal exchanger,
The r e s u l t s of clieniical s t a b i l i t y of the exchanger
in different solvent systems, presented in Table XVIII show
tha t the exchanger i s quite s table in deionized water,
concentrated solut ions of neutral" s a l t s and basic media.
However, the s t a b i l i t y of exchanger i s limited in the solut ions
of strong a c i d s . This i s probably because strong acids may
affect the matrix containing thorium.
Thus a l ike anion exchange r e s i n s , thorium tr ie thylamine
i s also less s t ab le and i t s s t a b i l i t y and capacity decreases
109
o a f t e r 60 C by the release of amine. The exchanger can be used
as a chelate Ion exchanger but the sui table e l a t i n g agent for
ca t ions i s to be t r i e d . The r e s u l t s of Table XIX for K values d
of various anions in d i f fe ren t solvent systems reveal that the
d i s t r i bu t ion coef f ic ien ts of d i f fe ren t anions are general ly
high in delonized water. A decrease in K, values was observed
when sodium hydroxide solution was used for equil ibrium s t u d i e s . K values decreased as the concentration of NaOH
d
was increased. When exchanger was placed in O.IM sodium
hydroxide solut ion, the ion exchanger showed high a f f i n i t y
for hydroxyl ions . Hence other ions showed l e s s uptake in the
presence of hydroxyl Ions.
On the bas i s of large differences in the d i s t r ibu t ion
behaviour of various anions many separations were t r i e d .
Separations of Cror" from Br~ and I~, CrgOZ"" from SCN", Br",
I ' and SCN", VOl from l " , PO^"" from Br", SCN", Fe(CN)g" and
s o " " from l " were successfully achieved (Figures 15-19).
Fur ther the r e s u l t s are quant i ta t ive (Table XX).
Thus thorium tr lethylamine may be used as an anion
exchanger with se lec t ive uptake of d i f fe ren t anions.
no
REFERENCES
1. B.A.Adams and E .L.Holmes, B r i t . P a t e n t ^50, 309, ^ S ,
pa ten t 2151883, 1939, Through Ion exchange by F .He l f r l ch
p . kl (1962) .
2 . R .Pa te rson , "An i n t r o d u c t i o n t o ion exchange". Heydon
and Son L td . London p . 12 (1970) .
3 . K.A.Kraus, H , O . P h i l l i p s , T.A.Carlson and J . S . J o h n s o n ,
Proc .2nd . In t .Conf .Peaceful Uses Atom.Energy, Geneva,
28 , 3 (1958) .
k» B .Br i t z and G.H.Nancollas , J .Tnorg.Nucl .Chem., 3 1 , 3861
' (1969)*
5 . M.Ahe and T .T to , Nippon ICagaku Z a s s h i , 86, 81? (1965) .
6 . B.Venkatarartianl and IC.S.Venkateshwarlu, J . I n o r g . N u c l .Chem.,
k2, 909 (1980) .
7 . J .P.Rawat and M. Iqba l , Annall T)l Chiraica, 69, 241 (1979) .
8 . J .P .Rawat , M.Iqbal and Masood Alam, Annall Di Chlmlca
(In P r e s s ) ,
9 . F .D.Sne l l and C . T . S n e l l , Co lo r lme t r l c methods of Ana lys i s ,
Vol . IV, Edn I I I , D.Van Nostrand Company I n c . P r i n c e t o n ,
New J e r s y , 37 (1954) .
10 . N.E.Topp and K.W.Pepper, J .Chem.Soc. , 3299 (1949) .
1 1 . R .Pa te r son , "An i n t r o d u c t i o n t o ion exchange" Heydon and
Son L t d . London p . 99 (1970) .
CHllPTER-IV
SYNTHESIS AND PROPERTIES OF ZIRCONIUM TRIETHYLAMINE
AS A NEW ANION EXCHANGER
I l l
In the continued effort t o synthesize a new inorganic
anion exchanger based on metal hydroxides with amino group,
some mater ia ls of t h i s kind have been t r i ed in our l a b o r a t o r i e s .
Aluminium triethanolaroine was found t o behave as anion
exchanger ( l ) . Thorium triethanolamine as a chela t ing ion
exchanger has a lso been studied (2 ) , The s tudies on thorium
t r le thylamlne, summarized in the preceding chapter , pave the way
to develop some new ion exchanging mater ia l s of t h i s type to be
u t i l i z ed for some ana ly t i ca l ly Important separat ions on the bas i s
of t h e i r anion exchange behaviour and for sorption of metal Ions
on the bas is of t h e i r chelating a c t i o n . Therefore, the s tudies
-sz int?"^"-* *'" '-T,»+»%oo<c'.a flwather mater ia l of t h i s kind,
zirconium tr lethylamlne and to compare i t s behaviour with
thorium t r l e thy lamlne . The mater ia l has been studied for i t s
anion exchange capaci ty , sorption capaci ty and d i s t r i b u t i o n
of d i f ferent anions t o measure s e l e c t i v i t y . Composition
s tudies and I,R, s tudies are made to character ize the exchanger.
112
EXPERIMENTAL
Apparatus
An e l e c t r i c temperature c o n t r o l l e d STCO shaker , Bausch
and Lotnb s p e c t r o n l c 20 (U.S.A.) and E l i c o pll meter model Ll - lO
(India) were used for shaking purposes, spectrophotometrlc
determination and pH measurements r e spec t ive ly .
Reagents
Zirconium oxychloride (B.T).H.) triethylamine (E.Merck)
were used. The other chemicals were of analytical grade.
Synthesis
Zirconium triethylamine was prepared by mixing a
0.1 molar solution of triethylamine in the ratio of 1:2
(Table XXl)». The precipitate thus obtained was kept standing o
for 2k hours at room temperature (25 +, 1 C), The p rec ip i t a t e
was then f i l t e red and washed with deionlzed water . I t was o
dried in an a i r oven a t ^0 C and then kept in the a i r for
12 hours . The dried material on Immersion in water broke down
in small p ieces . The exchanger granules were converted into
n i t r a t e form by keeping In 1 molar sodium n i t r a t e solut ion
overnight in te rmi t t en t ly replacing the supernatant l iquid
with gresh solution of sodium n i t r a t e . I t was f ina l ly washed o
and dried at 40 C.
113
a 9
5z; O
H
o x/i
g O
o M
o en
O M M
o o
CO
i 111
55 {H
« Pi CO o
« < M Cd O
o
I
o CI u
o
B
B
B W)
' ^ cr
a
O
Oi
o
\X
O CM
(0 IH 0 0) C CL O Pu (0 (0
« a> > +» r-l CO O •4J (0 •H W P . - H
•H iQ O 0) 43
M fi •H A) (0
»H 3 JB
1
o •7
o •p CO 4» •H Ci.
•H
o 4> h o. JU o •H A •P
CO h CO 0) p . a. CQ «D
« o; > • » rH CO O V (0
- -H to (X*H
•H IQ O « +> t s
I o
CO
c3
O
H
3 §
0 •H B CO H >. .C
•H
E H
0)
•H O
O tf
M O
CO
CM T H
ca ••
TH
t ^ •• •H
"H
•« l ^
O O
•H ^
X o o
CO ca (O t ^
(O 4«
CO CO
114
RESULTS
Anton exchange capacity *
The anion exchange capacity of zirconium triethylamine
was determined by column method. The anion exchanger weighing
one gram was poured in a glass column measuring 20 cm long and
0.6 cm diameter with a glass wool support. The capacity was
calculated for different anions namely, chromate, dlchromate,
chloride, bromide, iodide, thlosulphate, sulphate and thlo-
cyanate. By converting the exchanger In the required form
with sodium or potassium salts of the required ions. The
column was washed with deionized water. The eluent used was
IM sodium nitrate. The elutlon rate was fixed at 0.5 ml/
minute. Table XXII gives a view of the exchange capacities
for different anions. Anion exchange capacity of hallde ions
is plotted against ionic radii (Figure 20).
115
< a.
< ^
uj £ CD 0>
5 e UJ
z o
0-15
0-10
0-05 1-70
-J I I I 1-80 1-90 2-00 2.10
IONIC RADII
2-20
FIG.20. ION EXCHANGE CAPACITY AGAINST IONIC RADII ( FOR HALIDES )
116
TABLE XXII
ANION EXCHANGE CAPACITIES OF ZIRCONIUM TRIETHYLAMINE
FOR DIFFERENT ANIONS
SL. NO.
ANIONS SALTS TAKEN CAPx\C ITY (meq/gm)
1 .
2.
3.
4.
5.
6.
7.
8.
Chloride
Bromide
Iodide
Sulfate
Thlosulfate
Thlocyanate
Chromate
Bichromate
Sodium chloride
Potassium bromide
Potassium iodide
Sodium su l fa te
Sodium th lo su l f a t e
Potassium thlocyanate
Potassium chroma te
Potassium dichromate
0.20
0.16
0.10
1.00
0.27
0.15
2.50
3.20
Sorption capacity
One gram of t he exchanger was taken in the column,
10 ml of O.OlM copper solution was added over the column at
a ra te of 0.5 ml/minute. The eff luent was then t i t r a t e d and
copper ions were determined. A fresh sample of 10 ml of O.OlM
copper n i t r a t e was added over the column and the ef f luent was
again t i t r a t e d . The reading of EBTA consumed for t o t a l effluent
was subtracted from the reading of EDTA consumed for t o t a l
117
Influent (O.OlM copper n i t r a t e ) . The sorption capaci ty was
ca lcula ted from these readings. For determining copper Ions,
the solution was t i t r a t e d against 0.01 molar EDTA solut ion
using buffer of pH 3»6 and Pan Ind ica tor . The sorption
capaci ty of copper(II) was found to be 0.42 meq/g of zirconium
t r i e thy lamlne .
Composition
1 gram of zirconium tr ie thylamlne was dissolved In
50 ml of aquaregia. Heating was avoided for preparing so lu t ion .
I t was then made upto the mark in 100 ml standard flaslc with
deionized water . The amount of zirconium present in the sample
was determined by chelometric t i t r a t i o n s using Copper-Pan
ind ica tor while quant i ta t ive determination of t r ie thylamlne in
another portion of the sample was done spectrophotometrically
by ninhydrin (3) , Zirconium and tr iethylamlne were found in
the r a t i o of 1:2 in the exchanger.
Chemical s t a b i l i t y
To check the chemical s t a b i l i t y of the exchanger
zirconium t r ie thylamlne, 0.5 gram of the exchanger was shaken
with d i f ferent solvents for four hours . The amount of zlrcoriiun
present In the supernatant l iquid was determined by t i t r a t i n g
a known volume of the solution against EDTA and the amount of
t r ie thylamlne was determined spectrophotometrically in another
118
sample by nlnhydrin. Table XXIII gives the s t a b i l i t y of
exchanger In d i f f e ren t solvent systems.
TABLE XXIII
STABILITY OF ZIRCONIUM TRIETHYLAMINE IN DIFFERENT SOLVENTS
SL. NO.
SOLVENT SYSTEMS SOLUBTLTTY (mg/50 ml )
Z i r c o n i u m
CO
00
00
00
2 . 5
1 6 . 0
00
00
7 . 5 0
2i».0
2 . ^ 0
00
1
Triethylamlne
00
00
00
00
3 . 0
20.10
00
00
12.60
^0.90
5.00
00
1. Deionized water
2. Sodium nitrate
3. Ammonium hydroxide (IM)
4. Sodium hydroxide (IM)
5. Formic acid (O.IOM)
6. Hydrochloric acid (O.IOM)
7. Methyl alcohol
8. Ethyl alcohol
9. N i t r i c acid (O.IOM)
10. Sulfuric acid (O.IOM)
11. Acetic acid (O.IOM)
12. Hydrochloric acid (o.OlM)
Effect of heatlnia;
Different samples of zirconium tr ie thylamlne were heated
119
In the muffle fumance for ^ hours . The capacity of exchanger • e o o o o
a t 60 , 100 , 150 , 200 , 300 and kOO C were d e t e r m i n e d
r e s p e c t i v e l y . The r e s u l t s a r e summarized i n T a b l e XXIV.
TABLE -XXIV
CAPACITY OF EXCHANGER FOR CHROMATE IONS
AT DIFFERENT TEMEERATUHfciS
SAMPLE NO. TEMPERATURE CAPACITY
(meq/gm)
1
2
3
k
5
6
o" 60
100
150
200
300'
c 0
c »
c c
0
c 9
c
2.50
2.50
1.92
1.60
0.31
0.23
St ruc tura l s tudies
To character ize the exchange I .R. s tudies were performed
The spectrum of zirconium tr iethylamlne was observed by using
KBr d i s c . The r e s u l t s are presented in Figure 2 1 .
120
LU O z < X u X UJ
lU
z < -J >• I
cr h-
D Z o u cc N Ix. O
D CE h-U UJ a (/)
QC
CM
6 Li-
( '/o ) BDNVi i lWSNVai
1 2 1
Potentiometric t i t r a t i o n s
pH t i t r a t i o n s of the exchanger zirconium tr ie thylamine
were performed by shaking 0,5 gm of the exchanger with solut ion
of O.OlM HCl and I t s s a l t s of O.OlM concentration by Topp and
Pepper method (k). The volume of react ion mixture was kept
50 ml In each case . The pH of the solut ion was noted a f t e r
equ i l i b ra t ing the solut ion for four hoursiFig22).
Dis t r ibu t ion studies
K- values for anions were determined by batch process.
1 ml of anionic solution was taken In a 50 ml standard f l a sk .
The remaining volume was f i l l ed up with the solution In which
i t s d i s t r i b u t i o n s tudies were to be s tudied . This solut ion
was then shaken for k hours with the exchanger weighing 0.5 gm
in a shaker. The anions which remained in the solut ion a f t e r
equ i l ib ra t ion were then determined. Total amount of anions
were a lso determined without e q u i l i b r a t i o n . The formula given
below Is used for determining d i s t r i bu t i on coeff ic ient values
of ions
r, T - F Volume of solution ^ F Weight of exchanger
where I and F stand for the I n i t i a l and f inal volumes of t l t r a n t
before and a f te r equ i l i b r a t i on . The r e su l t s of K, values d
In deionized water and different concentrations of sodium
122
£ ••-•
O X
I
O o 2
o ir>
lO •4
o >t
l O CO
o en
in <N4
O CM
ir>
o r—
'
o I 2 o •
o UL
O
O >
5 2 z o u a " N
O Li-
>
D O
Z QC o ^ b 2 < <
LlJ
u
n 2 < O -J
O tr a. 1-
in
CM
O
Hd
123
hydroxide solutions are summarized in Table XXV.
TABLE XXV
K^ VALUES FOR DIFFERENT ANIONS IN DIFFERENl' SOLVENTS a
SL. NO.
ANIONS K VALUES IN d
T T T -r
Water NaOH NaOH NaOH NaOH ( 1 0 " \ ) ( 1 0 ~ ^ M ) ( 1 0 " " M ) ( i o " S f )
1 .
2 .
3 .
k.
5.
6 .
7.
8 .
9.
1 0 .
1 1 .
1 2 .
1 3 .
1 ^ .
1 5 .
1 6 .
1 7 .
C h l o r i d e
Bromide
I o d i d e
Dlch romate
Chromate
T h i o s u l f a t e
T h l o c y a n a t e
l o d a t e
P e r s u l f a t e
Brornate
S u l f i t e
S u l f a t e
F e r r l c y a n i d e
P e r r o c y a n i d e
A r s e n i t e
Phospha te
Vanada te
267+5
200+^3
115+Ji
T .A.
T .A.
T .A .
132+2
800jf2
566+5
l l U + 8
T .A.
T ,A.
T.A.
T .A.
T .A.
T .A.
560+3
256+4
175+2
79+3
T . A .
T . A .
T .A .
116+3
620+4
263+6
466+6
T . A .
T . A .
T .A .
T .A.
T . A .
2750^:5
340+2
171^3
153^4
72+^2
T .A .
271+^3
T .A .
108+^2
4144-5
100+^2
372 + 5
T .A.
T .A .
300+4
150+3
T .A.
230+2
120+3
48^2
20+_2
43+3
4+1
60+1
l l j f4
10+;1
56+6
54+1
31+:2
00
34
00
4jfl
2750+6
12512
25+2
42+3
8+2
34+3
00
00
2^1
00
00
5+1
11+2
00
23
00
00
584.2
.2012
25^2
T . A , = T o t a l a d s o r p t i o n .
12,4
Separations
On the basis of large differences in K^ values many
analytically Important separations of anions were achieved.
The column was prepared using 2.0 gram of the exchanger
(150-200 mesh size) in nitrate form in a glass column having a
height of 30 Cms and diameter 0.6 cm. A mixture of anion
solutions was applied on the column. The solution was allowed
to follow down very slowly through the column. These anions
were adsorbed at the top of the exchanger bed forming initial
zone. The column was washed with deionized water. The anions
were then eluted by appropriate eluting reagent. The amount
of anlais were then determined by standard methods. The
eluted fraction was having only one component of the mixture.
Separations of CrgOl*" from Br", l"; AsOg from Cl~; CrOr" from
l", Br*" and CroOl" from SCN"" were successfully achieved.
The elutlon curves for each set of separation are shown in
Figures 22-24 and quantitative separations of anions on
zirconium trlethylamine exchanger are given in Table XXVI.
-
I o o z z *— o
1
o . CM
I ' I ' o 0 z z r -
o o o 6 '
•
' 1
'
' 1
1 1 r^ o
o
' 1
-
' ^ •sC_
J J» ^ y^
~~-r~—
—
-
2 T >
/
o o CM
o
125
,
I o o z s. *" • o
1
o -CM
I ' i
I o o z z r—
o o o o
1
.
' L
• I
^^ o
K-*
1
1 1 "^ o
CM 1 -
u
1 1
1 CD /^
1 1
—
• -
mf m.
o CM <—
o 00
o
o o M CM
o o CM
O (O
O CM
.^*s
\-z lU 3
U. Ul
u. o Ui
s 3 _J
o >
• r« O
CVJ I -
o 5 O (X u.
L-
l i -O
z o mmmm
\-< cc < OL Ld CO
1 r^
O (\J
(-U
5 u oc u.
1
M
LL.
o z O .» h-< cc < a. LLI
(/)
o CO
o
O XI
o o
(NJ
o o CM
O
r^
o
r^
o CO
o
o >* o
( l i u ) i N V a i l i WLO-0 dO 3WmOA
0-1MNaOH
o •
o u. o
D -J
o >
0 AO 80 120 160 200 2A0
0-1M NaOH
0-80
0-AO
40 80 120 160 200 240 280
VOLUME OF EFFLUENT (ml)
F IG .24 . ( a ) SEPARATION OF Cl~ FROM A s O g
(b) SEPARATION OF S C N " FROM C r ^ O y
1
I o 0 z z r~
o
> o
CM I '
i
I o 0 z z «" o o o o
'
I
' L
' .
^ o
r
1 1 s j O
o ______—
1 1
1 L .
CD ^
1 1 l ~ ~
» -
—
—
O • « *
CM
O o CM
o (D
*—
O CM r*
O CD
O
o
o CM
o o CM
o (O
f>*
F 1 -z u 3 - J u. l l . Ul
u. o
ai i . -J _ i o >
\^[ 2^
O 2 ^ ?i LiL OC
Li_ 1
1- 1 CD t-i
U. U.
o o Z Z o o 1- H < < QC CC ^ < CL a. LU UJ (J) if)
o CM
o 00
o
127
O JD
in CM
o
o CM
o CM
O O CM
O CO o
CM o 00
o
(lUJ) i N V b i l i WlO-0 dO 3WmOA
128
TABLE XXVI
QUANTITATIVE SEPARATIONS OP ANIONS ON ZIRCONIUM TRIETHYLAMINE
SL. NO.
1.
2.
3.
4.
5.
6.
1
MIXTURE
Br"
Cr^O--
r
Cr^O--
Br*
Cro;-
l'
cio;-
Cl"
AsOg
SCN*
CrgO--
1
BLUENTS
O.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
O.OOIM NaOH
O.IM NaOH
O.OOIM NaOH
O.IM NaOH
O.OOOIM NaOH
O.IM NaOH
1 -
ELUATE
(ml)
100
100
80
100
90
120
90
100
120
90
120
120
1 AMOUNT LOADED
(mg)
2.640
13.068
2.667
13.068
2,640
11.078
2.667
11.078
2.023
3.050
3.509
13.068
t
AMOUNT FOUND
(mg)
2.560
12.852
2.540
12.852
2.480
10.846
2.603
10.904
1.917
2.890
3.422
12.852
1
RECOVERY
96.96
98.34
95.23
98.34
93.93
97.90
97.60
98.42
94.76
94.75
97.52
98.34
129
DISCUSSION
The r e s u l t s of Table XXI show that for complete
prec ip i ta t i on t o occur, zirconium oxychloride t o tr iethylamine
r a t i o must be kept 1:2, ifhen zirconium tr ie thylamine in
H form was kept in contact with a so lut ion of sodium n i t r a t e
no re l ease of H was observed. When exchanger was kept in
copper(II) s o l u t i o n i t turned to blue in appearance. Copper(II)
ions were so strongly attached t o zirconium tr iethylamine
exchanger that even strong che la t ing group EDTA did not
completely detach copper ( l l ) from the exchanger. Hence sorpt ion
capacity was calculated by column method. Due t o t h i s great
a f f ec t ion of the exchanger for metal ions l i k e C u ( l l ) , K, va lues
were not ca l cu la ted for the metal i o n s . Anion exchange capac i ty
of the exchanger Is quite h igh . The capaci ty for dichromate
3 , 2 0 , chromate 2 ,50 and for su l fa te i s 1,00 meq/gm. A very
high value of ion exchange capaci ty towards dichromate ion
(3 .2 meq/gm) i s in accordance with the r e s u l t s of z l rcon ia (5)
and a l s o d i scussed in the preceding chapter page 105 . The
order for capac i ty for h a l l d e s i s CI ^ B r ~ > l"". The capac i ty
of the exchanger decreases as the ionic s i z e of the hal lde
Increases (Figure 2 0 ) , For some other ion ic s p e c i e s the capacity
decreases In the order CrgOl*^ ^ ^ 4 ^ ®2^3~* Thus the exchanger
behaves a c h e l a t i n g as we l l as an anion exchanger on the b a s i s ol
above d i s c u s s i o n s i t i s concluded that zirconium tr ie thylamine
130
shows anion exchange capacity due to the presence of -N - group
and chelat ing proper t ies due t o the presence of -N- group.
The r e s u l t s presented in Table XXIV give the ef fect of
temperature on the capacity of the exchanger. The capacity
decreases vrlth the increase In temperature. At higher
temperatures the water molecules and amine molecules are los t
from the exchanger thereby decreasing the capac i ty . As a
r e s u l t t h e capacity at higher temperatures i s much low. Loss
in weight per gram of the exchanger at d i f f e r en t temperatures
presented in Table XXVII indicate that a t 100 C the weight
loss Is because of loss in water molecules and amine molecules e e
upto 300 C, Above 300 C t h e r e i s no a p p r e c i a b l e weight l o s s
s ince a l l the amine i s l o s t . These r e s u l t s a r e in accordance
wi th the r e s u l t s of c a p a c i t y a t d i f f e r e n t t e m p e r a t u r e s
(Table XXIV).
TABLE XXVII
Iv-EIGHT LOSS OF THE EXCnANGER AT DIFFERENT TEMPERATURES
I I ' t t
SAMPLE NO. TEMPERATURE \fElGHT TAKEN WEIGHT FOUND WEIGHT LOST
(gm) (gm) (per gram)
1
2
3 k
5
100
150
200
300
^00
0.500
0.500
0,500
0.500
0.500
0.455^ 0.4362
0.4180
0.4040
0.4010
0.0892
0.1276
0.1640
0.1920
0.1980
131
The re su l t s of composition s tudies show tha t zirconium
and tr iethylamine are present in the molar r a t i o of 1:2 in the
exchanger. The r e su l t s of potentioraetrlc t i t r a t i o n curve
plotted in Figure 22 reveal that the exchanger zirconium
tr iethylamine behaves as a monofunctional exchanger.
The infrared spectrum of zirconium tr ie thylamine in
Figure 21 shows the absorption peaks at d i f fe ren t values of
wave numbers as given below:
(a
s t re tching v ib ra t ions ;
(h
(c
(d
(e
(t
A broad peak ranging from 3300-3550 cm" i s due t o -OH
A strong peak at 1380 cm" i s due t o C-N v ibra t ions and
C-H bending v ib ra t ions ;
A medium peak l i e s at 2930 cm" due t o C-H s t re tching
v ib ra t ions ;
A strong C-C s t re tching vibrat ion i s observed in the
frequency range of 1620-1660 cm" ;
A medium C-N bending frequency l i e s in the frequency range
of 1070-1080 cm" ; and -1
A medium peak in the frequency range of 800-840 cm i s observed due t o metal-oxygen bending v i b r a t i o n s .
I t i s quite c l ea r tha t the exchanger zirconium t r i e t h y l
amine contains amine group and the metal oxygen bond. I t
confirms that in the formation of t h i s type of exchanger the
amine is Incorporated with the metal oxide forming the mat r ix .
132
The d i s t r i bu t ion behaviour of anions (Table XXV)
Indicates tha t the K, values were high when delonlzed water
was used as a medium. Dis t r ibu t ion values were l ess when
sodium hydroxide solution was used l o r s t u d i e s . K, values d
decreased as the concentration of sodium hydroxide solut ion
was increased. Being a weak anion exchanger, zirconium
trlethylamine has a high a f f in i ty for hydroxyl ions hence
anions other than hydroxyl ion showed l e s s uptake in the
presence of hydroxyl ions .
Owing t o the large differences in the d i s t r i b u t i o n
values of various anions, many ana ly t i ca l ly Important separa
t ions were t r i e d . Separation of CrOr" from Br", T ~; of CrgO"'
from B r " l " , SON"; of Cl"* from AsOg were successfully achieved
(Table XXVT). These r e s u l t s also show a high s e l e c t i v i t y
towards CrO^" and CrgOZ" as predicted by capaci ty (Table XXIT),
On comparison of the behaviour of zirconium t r l e t h y l
amine with that of thorium tr le thylamine (in the preceding
chapter) the following three facts may be pointed out : ( i )
The chemical s t a b i l i t y of zirconium t r le thylamine i s b e t t e r
than thorium trlethylamine (compare Tables XVIII & XXIII);
(11) the va r i a t ion in Ion exchange capaci ty in case of
zirconium tr lethylamine with a wider range than the t r l e t h y l
amine. Although the trend is s imilar as may be checked with
the var ia t ion of hallde ions capacity on both the exchangers
133
with ionic r a d i i (Figures 8 & 20); and (111) zirconium
tr lethylamlne shows a remarkable high sorption capacity for
CU(TT) which gives i t s possible u t i l i t y as a b e t t e r chela t ing
material for cer ta in ions. However, the s e l e c t i v i t y for
different anions i s of nearly the same order with both
ma te r i a l s .
134
REFERENCES
1 . J .P.Rawat , M.Iqbal and Masood Alam, Annall Bl Chlmica
(In P r e s s ) .
2 . J.P.Rawat and Masood Alam, Annali Dl Chimica (In P r e s s ) ,
3 . F .D.Snel l and C . T . S n e l l , Co lo r l rae t r l c methods of Ana lys i s ,
Vol . IV, Edn I I I , D.Van Nostrand Company I n c . P r i n c e t o n ,
New J e r s y , 37 (1954) .
h, N.E.Topp and K.W.Pepper, J .Chem.Soc. , 3299 (19^9) .
5 . R .pa te r son , "An . in t roduc t ion t o ion exchange" Heydon and
Son L td . London, p . 99 (1970) .
CHAPTER-V
REDOX STUDIES ON HYDRAZINE SULPHATE SORBED ZINC SILICATE
135
The Inorganic ion-exchangers have found appl ica t ions
in many important f i e l d s . They are now heing extensively
used for the redox purposes in the modem l abo ra to r i e s . The
de f in i t e advantage of redox ion exchangers over the conventional
methods of oxidation or reduction i s t h e i r In so lub i l i t y in the
medium of react ion and thus the interference that are caused
by the unreacted redox substances are avoided. The oxidizing
or reducing substances can be eas i ly separated from the
substances with which they have reacted.
The few inorganic ion exchangers which have been used
for redox s tudies are zirconium molybdate (1) , zirconium
metatungstate (2) , zirconium phoaphoiodate (3) and few others
(4-6) , A new c l a s s of ion exchangers have recent ly been
prepared by Immobilizing some complexing agents on the common
ion exchangers ( 7 | 8 ) , The s tud ies on such products, however,
have been made only towards achieving separat ions of ana ly t i ca l
Importance ( 9 - l o ) . In t h i s chapter a new redox exchange
material has been prepared by the sorption of a reducing agent,
hydrazine sulphate , on zinc s i l i c a t e , a strong adsorbent and
a l so an inorganic ion exchanger (11,12). The successful
reduction of F e ( l l l ) , Mo(VT), V(V), Ce(lV), Sb(V) and Cr(VT)
have been achieved quan t i t a t ive ly using the above redox
exchange ma te r i a l .
136
EXPERIMENTAL
Reagents
Zinc nitrate (E.Merck), sodium silicate (Rledel,
German) and hydrazine sulphate (Merck) were used. All the
other reagents were of analytical grade.
Synthesis
Zinc s i l i c a t e was prepared hy mixing a O.lM solut ion
of zinc n i t r a t e and a O.lM solut ion of sodium s i l i c a t e . The
white p rec ip i t a t e so ohtalned was kept standing for 24 hours
at room temperature. The p r ec ip i t a t e was then f i l t e r e d ,
washed and dried at 40 C. The dried product was kept immersed
in a O.lM solut ion of hydrazine sulphate for ahout 2k hours.
Excess of hydrazine sulphate was washed out with demlnerallzed o
water and dried in an oven at 40 C,
Hydrazine sulphate uptake
The capacity of zinc s i l i c a t e to take up hydrazine
sulphate from i t s aqueous solut ion was estimated by shaking a
predetermined quantity of hydrazine sulphate solut ion with one
gram of the untreated zinc s i l i c a t e for six hours . Amount of
hydrazine sulphate remaining in the supemate was then determine
by t i t r a t i o n against 0.05M KBrO- solution using indigo as
indicator (13) . The amount of hydrazine sulphate i n i t i a l l y
137
taken minus the amount found after shaking with the exchanger
gave the total amount of the reducing agent taken up by the
exchanger.
138
RESULTS
Chemical stability
500 mg of the hydrazine sulphate sorbed zinc silicate
was shaken with the appropriate solvent for six hours at room
temperature. The amount of hydrazine released into the solution
was determined in the supernatant liquid in the manner mentioned
above. The results are summarized in Table XXVTII.
TABLE XXVIII
DISSOLUTION OF HYDIUZINE SULPHATE
t I
SL. SOLVENT HYDRAZINE SULPHATE RELEASED NO. (mg)
1 .
2 .
3.
k.
5.
6.
7.
Demineraliz
IM HCl
2M HCl
IM HgSO^
2M H2S0^
IM NH.OH 4
IM NaOH
ed water 0.0
25.0
75.0
20.0
78.0
0.0
50.0
139
Redox studies
Reduction of Pe(IIT), Mo(Vl), V(V), Ce(lV), Cr(Vl) and
Sb(V) to their respective lower oxidation state were performed
by passing their solutions through a column containing one gram
of hydrazine sulphate sorbed zinc silicate on a glass wool
support. The effluent was collected In a beaker containing a
dilute solution of sulphuric acid to avoid air oxidation of
the reduced products. Fe(II) and Mo(IV) obtained as effluent
were determined by titrating with a standard solution of
KMnO^ (14,15), V(V) (16), Ce(Vl) (17), Sb(V) (18) and
Cr(Vl) (19) were determined lodometrically before and after
the passage through the exchanger column. The amount Initially
taken minus the amount finally found gave the total amount
reduced by the exchanger,
(a) Reduction of Fe(lll) to Fe(ll) and V(V) to V(TV)
Results of reduction of Fe(lTl) to Fe(ll) and reduction
of V(V) to V(IV) are given in Table XXIX.
140
TABLE XXIX
REDUCTION OF Fe ( ITT) TO Fe(TT) AND V(V) TO V(lV)
SAMPLE NO.
1
2
3
4
5
6
t
AMOUNT OF EXCHANGER
(g )
0 . 5
1.0
1.0
1.0
1.0
2 . 0
1
P e ( I I I ) TAKEN
(mg)
5 .20
1 3 . 0 0
1 5 . 0 0
1 0 . 4 0
7 . 6 0
2 6 . 0 0
• F e ( I l ) POUND
(mg)
5 .17
1 2 . 6 0
1 2 . 6 0
1 0 . 0 0
7 . 6 0
2 5 . 2 0
v(v) TAKEN
(mg)
7 . 2 0
11 .25
IkAO
2 2 . 5 0
8 .60
3 0 . 2 0
1
V(IV) FOUND
(mg)
7 .05
1 1 . 1 0
U . I O
1 4 . 0 0
8 .40
2 8 . 2 0
(b ) R e d u c t i o n of Mo(y i ) t o Mo(IV) and Sb(V) t o S b ( l T l )
R e s u l t s of r e d u c t i o n of Mo(Vl) t o Mo(lV) and r e d u c t i o n
of Sb(V) t o S b ( I I l ) a r e p r e s e n t e d i n T a b l e XXX.
141
TABLE XXX
REDUCTION OF MO(VT) TO Mo (TV) ANO Sl,(V) TO Sl)(lTl)
SAMPLE NO.
1
2
3
k
5
6
i •
AMOUNT OF EXCHANGER
( g )
1 .0
1 .0
1 .0
1 .0
0.5
2 . 0
Mo(VI) TAKEN
(n»g)
10.6
21.2
7.2
10.6
5.3
18.2
• Mo(IV) FOUNB
(mg)
8 . 8
8 . 9
7 .2
8 . 9
4 . 6
1 8 . 0
• Sb(V) TAICEN
(n>g)
5 . 8
8 . 0
1 5 . 6
1 6 . 2
8 . 0
3 1 . 0
1
S b ( T I l ) FOUND
(mg)
5.6
7.3
15 .2
15 .2
7.3
• 3 0 . 2
(c) Reduction of Ce(IV) to Ce(lll) and Cr(Vl) to Cr(lIT)
Results of reduction of Ce(IV) to Ce(III) and reduction
of Cr(Vl) to Cr(IIl) are given In Table XXXI.
142
TABLE XXXI
REDUCTION OF Ce(lV) TO Ce(IIl) AND Cr(Vl) TO Cr(lII)
SAMPLE NO.
1
2
3
k
5
1 t
AMOUNT OF EXCHANGER
(g)
0.5
1.0
1.0
1.0
1.0
Ce(IV) TAKEN
(mg)
10.5
25.6
21.0
15.2
10.5
1
Ce(IIl) FOUND
(mg)
10.0
20.0
20.0
14.8
10.2
1
Cr(VT) TAKEN
(mg)
2.0
h.O
3.0
3.6
8.0
1
Cr(III) FOUND
(mg)
1.8
3.9
2.8
3.5
3.9
Maximum redox capacity
Maximum redox capacity was determined by repeatedly
passing the solutions of reducing metal ions through a column
containing one gram of hydrazine sulphate sorbed zinc silicate
on glass wool support. Volume of the titrant needed for
reducing the substances was then calculated by substracting
the volume of titrant consumed against unreduced substance
from the volume of titrant consumed for the effluent. The
maximum redox capacity in equivalents was then determined by
multiplying the volume of titrant with the concentration of
143
t i t r a t i o n f o r e v e r y s u b s t a n c e . The r e s u l t s a r e p l o t t e d
In T a b l e XXXTI.
TABLE XXXTI
MAXIMUM REDOX CAPACITY OF SOMK REDUCIBLE SUBSTANCES
1 i
SAMPLE NO. SUBSTANCE REDUCED MAXlMU>f AMOUNT REDUCED
(ffiilllequlv/g)
1 Fe(lll) 0.22
2 Mo(Vl) 0.27
3 V(V) 0.27
4 Sb(V) 0.25
5 Ce(lV) 0.12
6 Cr(VT) 0.22
Rate of reduction
The rate of reduction was determined by talcing a
weighed amount of exchanger In stoppered conical flasks and
shaking thoroughly with the solution concerned in a shaking
machine. After appropriate intervals of time, the contents
of the flasks were filtered and the reduced species formed
determined. The results are shown In Table XXXIII and In
Figure 26.
144
E o z 3 O UL
3 O < Z < >
20 30 t (min )
VANADIUM ( V ) T A K E N =A-5mg
FIG.26. RATE OF REDUCTION OF VANADIUM (V)
145
TABLE XXXIII
RATE OF REDUCTION OF VANADIUM(V) TO VANADIUM(IV)
Amount of vanadium(V) taken = 12 .75 mg
TIME (mln . ) AMOUNT OF V(IV) FOUND
(rag)
0 0.00
1 0 . 7 7
5 1 .79
10 2,Oh
20 2 . 5 1
30 2 . 5 1
60 2 . 5 1
146
DISCUSSION
The redox exchangers may be considered as solid
oxidation and reducing agents. They contain the species forming
a redox couple and after having oxidised (or reduced) a
substrate the redox exchanger can be regenerated by a suitable
oxldlzin/s; or re'lucing agent. The most Important advantage of
redox exchangers over dissolved oxidizing or reducing agents
is their Insolubility and hence a redox exchanger can be easily
separated from the solution containing a substrate being
oxidized or reduced. The solution is free from contamination
of any redox agent or its products. Only electrons and protons
are transferred between the exchanger and the solution. Therefore,
the only possible change in the solution, except for the
redox reaction of the substrate, is a change in pH. Another
advantage of electron exchangers is that they can be readily
regenerated (oxidized or reduced) after use.
The product zinc silicate shows a remarkable property
to sorb oxidizing or reducing agents when kept immersed in their
aqueous solutions. Immobilization of such substances in the
layers of zinc silicate makes it to lose its ion exchange capacity
and acquire redox properties instead. This property is because
of the fact that the available pores which otherwise would have
been a site of ion-exchange process have now been occupied by
the sorbed substance. The redox ion exchangers which contain
147
the redox couple in the exchanger phase, a l s o behave in a way
similar to e lec tron exchangers. The present redox exchanger
has been prepared by the sorption of hydrazine sulphate on z inc
s i l i c a t e . This material has been u t i l i z e d for the reduction
of some reducible spec ies whose redox p o t e n t i a l s are lovfer than
that of hydrazine/NH_ couple .
The uptake of hydrazine sulphate by z inc s i l i c a t e has
been studied and i s found t o be 0.28 m l l l l e q u i v a l e n t s / g . The
chemical s t a b i l i t y of the sorbed substance has been studied in
d i f ferent concentrat ions of ac ids and b a s e s . Di lute a c i d i c ,
d i l u t e bas ic and neutral so lu t ions can be s a f e l y used for the
reduction processes .
The r e s u l t s presented in Table XXIX show the success fu l
reduction of P e ( I I l ) to Fe(Tl) and V(V) t o V(IV). The maximum
amounts of Fe(TII) and V(V) that can be reduced are 12,6 mg
and 1^.1 mg r e s p e c t i v e l y . The r e s u l t s of the reduction of
Mo(VT) and Sb(V), presented in Table XXX and that of Cr(Vl) and
Ce(TV) reported In Table XXXI indicate that the maximum amounts
of MO(VT), Ce(TV), Cr(Vl) and Sb(V) which can be reduced by one
gram of the exchanger are 8 ,9 mg, 20 ,0 mg, 38 rag and 15,2 mg
r e s p e c t i v e l y . For the reduction of higher amounts of these
substances a bigger column should be taken. When these amounts
are viewed in terms of number of equiva lents , It has been
observed that except f o r C e ( I V ) the maximum redox capacity of
148
one gram of the exchanger ranges between 0.22 to 0,2 7 m l l l l -
equlvalents/g (Table XXXTT). This shows tha t the t o t a l
capacity of the column i s u t i l i zed for every reduction
reaction mentioned above. The number of mi l l lequivalents of
Ce(IV) reduced is only 0,12 which is far l e s s than the number
of mi l l l equiva len ts of hydrazine sulphate present in the exchanger.
This , probably. I s because of the tendency of the aqueous
solut ion of ce r r i c ammonium sulphate t o undergo hydrolysis In
the absence of a concentrated solut ion of HgSO.• And use of a
solut ion having a sulphuric acid concentration more than IN
causes release of hydrazine sulphate in to the eluate (Table XXVIII)
The r e s u l t s of the redox s tudies show tha t the reduction
of only those substances are possible whose redox po ten t i a l s
are less than tha t of reducing agent incorporated with the
exchanger. Attempts at reducing As(V) t o As( I I l ) on these
columns have failed since As(V)/As(lIl) couple has a higher redox
po ten t ia l than hydrazine/NH_ couple. Redox poten t ia l s of some
of the reducible species are given in Table XXXIV t o support
the above d iscuss ion .
149
TABLE XXXIV
STANDARD REDOX POTENTIAL OF REDOX COUPLES
t e REDOX COUPLE E , VOLTS
C r ( V l ) + 3 e " •: ^ C r ( I I l ) 1 .33
F e ( l I I ) * e " ^=t F e ( l l ) 0 . 7 7
C e ( I V ) + e " - ^—:*- C e ( l l l ) 1 .61
Sb(V) + 2 e ' - ^ S b ( I I l ) 0 . 7 5
2NH_ ( a q ) • 20H'' ^ NgH^ + SHgO + 2 e " O.Ol
The r e a c t i o n r a t e I n d i c a t e s t h e t ime r e q u i r e d f o r
r e d o x p r o c e s s u n d e r a g iven s e t of c o n d i t i o n s . The r a t e of
r e d u c t i o n of V(V) t o V(TV) I s i l l u s t r a t e d i n F i g u r e 2 6 . I t can
he seen t h a t on ly 20 m i n u t e s a r e r e q u i r e d f o r c o m p l e t e c o n v e r s i o n
of V(V) t o V ( I V ) . T h i s f a s t r a t e of r e d u c t i o n I s not found
w i t h t h e e x c h a n g e r s h a v i n g F e ( I I l ) , t u n g s t e n o r molyhdenum(Vl)
a s o x i d i z i n g g r o u p s . The column c a n be r e g e n e r a t e d by p u t t i n g
t h e e x c h a n g e r in t h e h y d r a z i n e s u l p h a t e s o l u t i o n a g a i n f o r
o v e r a n i g h t .
150
REFERENCES
1 . R.G.Safina, E .S.Bolchinova and N.E .Renlsova, Z h u r . P r l k l a d ,
Khim., hh, 2337 (1971) .
2 . E .S.Bolchinova and N.O.Osipora, Zhur .Pr ik lad .Khim,,
49 , 1728 (1972) .
3 . J .P.Rawat and M.Iqba l , Annal i d i Chlmica, 69 , 2kt (1979) .
h, E ,S .Bolchinova , R.G.Safina, V.V.Belove and L.G.Kar l tonova,
Zhur .P r ik lad .Khim. , ^ 9 , 1385 (1976) .
5 . V.V.Volkhtn, S.A.Kolesova, M.V.Zlbberman, L .T .Pykht Ina ,
V.V.Tetenov and A.V.Kalyuzhnvl, Zhur .P r ink lad .Khim, ,
49, 1728 (1976) ,
6 . B .D.Flockhar t , M.C.Megarry and R.C.Plnk, Adv.Chem.Ser,,
121, 509 (1973) (Molecular s i e v e s , 3rd I n t e m a t .Conference)
7 . K.Bra j ten , Chem.Anal. (Warsaw), 18, 125 (1973) .
8 . K.Braj ten , J .Chromatogr . , 103 , 385 (197^)«
9 . J.P.Rawat and M.Iqbal , J . L l q u i d Chromatogr . , 3 , 591 (1980) .
10 . J.P.Rawat and M.Iqbal , J ,L iqu id Chromatogr . , 3 , 1657 (1980)
1 1 . J.P.Rawat and M.Iqbal , J . L i q u i d Chromatogr . , 3 ( ^ ) , 591-603
(1980) .
12 . J .P.Rawat , M.Iqbal and Masood Alam, J . L i q u i d Chromatogr , ,
5 ( 5 ) , (1982) .
1 3 . I .M.Kolthof and R.Belcher , 'Volumetric A n a l y s i s ' , V o l . I l l ,
I n t e r s c l e n c e P u b l i s h e r s , I n c . , N.Y, , page 524 (1957) .
14 . A . I .Voge l , ' Q u a n t i t a t i v e Inorganic A n a l y s i s ' , I I e d n , ,
Longmans, London, page 276 (1951) .
151
15 . I b i d , page 277.
16. - I .M.Kol thof and R.Belcher , 'Volumetric A n a l y s i s ' V o l , T i l ,
i n t e r s c i e n c e p u b l i s h e r s , Inc .N.Y, page 340 (1957) ,
17 . I b i d , page 367.
1 8 . I b i d , page 319.
19 . I b i d , page 239.
J. Indian Chem. SQC. Vol. 1.X, No. 10. Pp. 911—1008 ISSN 0019-4522
October 1983
CODEN i JICSAH LX. (10) (1983). 911—1008
JOURNAL
OF THE
NDIAN
HEMICAL
UOC lETY
Published by The Indian Chemical Society
92, Acharya Prafulla Chandra Road»
Calcutta.700 009
3. iDdlu Chem. Boc. Vol. LX. October 1983, pp. 993-994
Redox Studies on Hydrazine Sulphate Sorbed Zinc Silicate
J. P. RAWAT», M. IQBAL and H. M. A. ABDUL AZIZ
Department of Chemistry, Aligarh Muslim University, Aligarh-202 001
Manuscript received 20 September 1982, revised 27 April 1983, accepted 3 August 1983
INORGANIC ion-exchangers have found many important applications. They are being extensively used for redox purposes in modern laboratories.
The definite advantage of redox ion-exchangers over the conventional methods of oxidation or reduction is their insolubility in the medium of reaction, thus the interferences caused by the unreacted redox substances are avoided. The oxidizing or reducing substances can be easily separated from the substances with which they have reacted.
The few inorganic ion-exchangers to have been used for redox studies are zirconium molybdate^, zirconium metatungstate^, zirconium phosphoiodate" and a few others*"*. A new class of ion-exchangers have recently been prepared by immobilizing some complexing agents on the common ion-exchan-Kcis The studies on such products, however, have been made only towards achieving separations of analytical importance*-i°. In the present studies, we have prepared a new redox material by the sorption of a reducing agent, hydrazine sulphate, on zinc silicate, a strong adsorbent. The successful r e d S o n of Fe(III), Mo(Vl). V(V). CeCV) Sb(V) and Cr(Vl) has been achieved quantitatively using the above redox material.
Experimental Zinc nitrate (M. Merck), sodium silicate (Riedel)
and hydrazine sulphate (Merck) were used. All other reagents were of analytical grade. Zinc silicate was prepared by mixing a 0.1 M solution of zinc nitrate and a 0.1 M solution of sodium silicate The white precipitate so obtained was kept standing for 24 hr at room temp. The precipitate was then filtered, washed and dried at 40° The dried product was kept immersed in a solution of hydrazine sulphate for another 24 hr. Excess of hydrazine sulphate was washed out with demineralized water and the product dried in an oven at 40°.
The capacity of zinc silicate to take up hydrazine sulphate from its aqueous solution was estimated by shaking a predetermined quantity of hydrazine sulphate solution with 1.0 g of untreated zinc silicate for 6hr , estimating the amount of hydrazine sulphate remaining in the supernate (0.05A/ KBrOg solution using indigo as indicatori^), and calculating the difference.
Chemical stability : 500 mg of the hydrazine sulphate sorbed zinc silicate was shaken with .the
appropriate solvent for 6 hr at room temp. The amount of hydrazine released into the solution was determined in the supernatant liquid in the manner mentioned above.
Redox studies : Reductions of Fe(IlI), Mo(VI), V(V), Ce(lV). Cr(VI) and Sb(V) to their respective lower oxidation states were performed by passing their solutions through a column containing 0.5, I or 2 g of hydrazine sulphate sorbed zinc silicate on a glass wool support. The effluent was collected in dil. HaSO^ solution to avoid uir-oxidation of the reduced products. The dissolved oxygen in the HjSO^ solution was driven out by adding a small quantity of sodium carbonate. Fe(II) and Mo(III) obtained as effluent, were determined by titrating with a standard solution of KMnO^^^'^*. V(V)^*, Ce(VI)i», sb(V)i« and Criyiy were determined iodometrically before and after the passage through the exchanger column. The amount initially taken minus the amount finally found gave the total amount reduced by the exchanger.
Rate of reduction : The rate of reduction was determined by taking a weighed amount of exchanger in stoppered conical fiasks and shaking thoroughly with the solution concerned in u shaking machine. After appropriate intervals of time, the contents of the flasks were -filtered and the reduced species formed determined (Fig. 1).
Fig. 1. Rati; of reduction of V(V). V(V) taken = 4.5 nig
Results anil Discuss!un The product zinc silicate shows a remarkable
property to sorb oxidising or reducing agents when kept immersed in their aqueous solutions. Immobilization of such subblanccs in the layers of zinc silicate makes them lose their ion-exchange capacity and acquire redox properties instead. We have utilized this property for the reduction of some reducible species whose redox potentials are higher than that of the hydrazine/NH3 couple.
993
J. INDIAN CHEM. SOC, VOL. LX, OCTOBER 1983
The uptake of hydrazine sulphate by zinc silicate was found to be 0.28 meq/g. The maximum amounts of Fe(III), V(V), Mo(VI). Ce(IV), Cr(VI) and Sb(V) which can be reduced by 1.0 g of the exchanger were found to be 12.6. 14.1, S.'J, 20, 3.8 and 15.2 mg, respectively. (0.22,- 0 27, 0.27, 0.12. 0 22. 0 25 meq/g). For the reduction of larger amounts a bigger column should be used. This shows that the total capacity of the column is utilized for every reduction reaction except for Ce**. This probably is because of the tendency of aqueous solution of eerie ammonium sulphate to undergo hydrolysis in absence of cone. H^SO^ bolution. And. the use of a solution having HsSO^ concentration iV > 1 causes release of hydrazine sulphate into the eluate.
' The results of the redox studies show that the reduction of only such substances are possible, whose redox potentials are less than that of the reducing agent incorporated with the exchanger. Attempts at reducing As(V) to Asdll) on these columns failed since As(V)/As(III) couple has a lower redox potential than hydrazine/NHg couple.
The columns can be regenerated by putting the exchanger in the hydrazine sulphate solution.
'Bleeding' of hydrazine sulphate has been studied in different aqueous and non-aqueous media. It has been found that the leakage of hydrazine occurs only in concentrated solutions of strong acids and strong bases. Dilute acidic, dilute basic and neutral solutions can safely be used for the reduction processes.
Fig. 1 shows the result of the rate of reduction of V(V) to V(IV). It can be seen that only 20 min are required for complete conversion of V(V) to V(IV). This fast rate of reduction is not found with the exchangers having Fe(III), tungsten or molyb-denum(VI) as oxidizing groups.
Acknowledgement The authors thank Prof. W. Rahman, Head,
Department of Chemistry, for facilities. (M.I.) is thankful to C.S I.R.. New Delhi and (H.M.A.A.) to Mmistry of Education, Government of India, for financial assistance.
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Zhur.Priklad. Klum., 1971, 44, 2337. 2. E. S. BoiCHiNovA and N. O. OSIPORA, Zhur. Pnklad.
Khim., 1912, 49, nii. 3. J. P. RAWAT and M. IQUAL, Ann. Chim., 1979 69, 241. 4. E. S. BoiCHiNovA, R. G. SAFINA, V. V. BCLOVA and
L. G. KARITONOVA, Zhur. Pnklad. Khim., 1976, 49, 1385.
5. V. V. VOLKHIN, S. A. KOLESOVA, M. V. ZlBBERMAN, L. I. PYKHTINA, V . V . TETENOV and A. V. KALYU-ZHNVi, Zhur. Priklad. Khim., 1976, 49, 1728.
6. B. D. FLOCKHART, M . C . MEOAHRY and R. C. PINK, Adv. Chem. Ser., 1973,121, 509 (Molecular Sieves, 3rd Internal. Conference).
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1980, 3, 591. 10. J. P. RAWAT and M. IQBAL, / . Liquid Chromatogr.,
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994
