THE AMERICAN MINERA]-OGIST, VOL. 48, JULY-AUGUST, 1963

MASS ACTION RELATIONSHIPS OF SOME ZEOLITESIN THE REGION OF HIGH COMPETING CATION

CONCENTRATIONSI

L. L. Anes, J*.., General Electric Co., Richland, Washi,ngton.

Ansrnacr

Mass action quotients for the synthetic zeolites Linde 4AXW, 13X, AW-300, AW-400,AW-500, Norton Zeolon and the natural zeolites clinoptilolite and erionite were determinedfor low cesium or strontium concentrations in the binary systems cesium-sodium, cesium-potassium, cesium-rubidium, strontium-calcium and strontium-sodium. The equilibriumsystems cesium-hydrogen and strontium-hydrogen were determined for the zeolites LindeAW-300, Norton Zeolon and clinoptilolite. A portion of the ternary system hydrogen-so-dium-cesium was determined for clinoptilolite.

Cesium mass action quotients generally declined in going from cesium-sodium tocesium-rubidium systems. Structural difierences between two members of the same zeolitespecies often resulted in cation exchange equilibria differences as great as those betweendifferent species.

The binary curves may be used to determirie column loading of the above zeoiites.

hqrnooucuow

Considerable interest in the zeolites as cation exchange media has beengenerated in the atomic energy industry. Several processes using zeoliteshave been proposed or are in operation. I{ercer (1960) studied the use ofclinopti lolite for decontamination of condensate wastes containing traceamounts of cesium and strontium radioisotopes. Nlathers and Watson(1962) described the disposal of 8200 liters of an intermediate-levelwaste through an 1800 kg clinopti lolite column. The use of clinopti lolitecolumns for cesium extraction from Hanford high-level wastes is underconsideration (Tomlinson, 1962, and Nelson, et al., 1960). The othercations on the clinopti lolite column, such as sodium, can be preferen-tially eluted with dilute acid while less than one per cent of the adsorbedcesium is eluted. The cesium remaining on the column is removed at55' C. with ammonium carbonate. The cesium-ammonium carbonateeluate is then disti l led, leaving concentrated, high-purity cesium carbonate. Tuthil l , Weth and Abriss at Brookhaven National Laboratory havestudied and developed a process for treatment of high-level wastes usingclinopti lolite ion exchange columns to remove cesium and strontium(I,Iorgan, et al., 7961).

Several commerciaily-available, synthetic zeolites are being consideredas storage media for f ission products such as the above cesium (Tomlin-son, 1962). Knoll has shown that synthetic zeolites or clinopti loliteloaded with radioactive cesium or strontium can be heated to 600" C.

1 Work performed under contract No. AT(4.5-1)-1350 for the U. S. Atomic Energy

Commission.

868

MASS ACTION OF ZEOLITES 869

for two hours to remove all zeolit ic water before storage, and the radio-active cesium or strontium can be eluted with several agents (Ames andKnoll, 1962).

Despite the interest in the uti l ization of zeolites for waste decontami-nation and fission product storage, there are l itt le quantitative dataavailable in the l iterature on zeolite strontium and cesium exchangeequil ibria, especially in the region of very high concentrations of compet-ing cations. Process applications involving zeolites cannot be init iateduntil cesium or strontium exchange equil ibria with other cations ofinterest are known. Consequently, the present study was undertaken toprovide the necessary data. Portions of the data from this study, ofpossible interest to earth scientists, are presented here.

MBrnoos oF INVESTTGATToN

The clinoptilolite used in this study was obtained from the Hector,California, deposits of the Baroid Division of National Lead. The as-received clinopti lolite ore consisted of 85 to 95 per cent by weight pureclinopti lolite, and 5 to 15 per cent by weight unaltered volcanic glassplus quartz and feldspar along with lesser amounts of calcite and mont-moril ionitic clays (Ames, 1960). carbonates and ciays in the clinopti lo-lite were removed or destroyed by a ten per cent nitric acid wash priorto use.

The erionite used in this study was from Nevada and contained tenper cent, or less, impurit ies. Clinoptilolite and erionite purit ies wereestimated by examination of thin-sections and comparison of r-raydiffraction patterns, and average*5 per cent of the purity range givenfor the selected samples used in this study.

Several synthetic zeolites were supplied, as one-sixteenth-inch diametersodium-based pellets, by the Linde Company of Tonawanda, New york,including 13X, 4AXW, AW-300, AW-400 and AW-500. The NortonCompany of Worcester, Massachusetts, supplied one-eighth-inch, hydro-gen-based Zeolon pellets.

Table 1 gives the sil ica-to-alumina ratio of the above zeolites alongwith their structural types and weight per cent binder for the sodiumform.

Zeolites used in the equilibrium experiments were based with satu-rated chloride solutions of the desired cations. Nitric acid was used inten per cent solution to hydrogen-base clinoptilolite, Zeolonand AW-300.Fifty-gram portions were placed in 400 ml beakers and appropriatechloride solutions were added. The contacting chloride solutions werechanged six times at 45-minute intervals. A seventh and final solutionwas contacted for two days. Previously-obtained kinetic data indicated

870 L, L. AMES, TR.

that the above base exchange procedure was adequate (Ames, 1961).

Kinetics of coarsely-crystalline, natural zeolites such as stilbite or

heulandite are very poor when compared to the synthetic zeolites or

those derived from altered tuffs. The equil ibrium times involved in the

above base exchange procedure would be wholly inadequate for many

of the coarsely-crystall ine, natural zeolites. Synthetic zeolites and

zeolit ic altered tuffs are cemented aggregates of crystall i tes that rarely

exceed five microns in size, and for that reason, require a much shorter

equil ibration time.Af ter completing the base exchange procedure, the zeolites were

thoroughly washed with disti l led water unti l chloride could not be de-

SiOz/AlzOa Wt. per cent binder Structural Type

4AXW4A13XAW-300AW-400AW-500ZeolonClinoptiloliteErionite

82020252525

unknown.)-l J

5

AA

FaujasiteMordeniteErioniteChabaziteMordeniteClinoptiloliteErionite

za

2 . 89-10o-/,t-s

108-106

tected in the wash water with AgNOr solution. All zeolites were checked

by r-ray difiraction to assure that no major structural changes had

taken place during the exchange.Cation exchange capacities were determined by a double tracing

technique. Weighed, sodium-based samples were contacted with a solu-

tion containing 0.1I/ CsCl plus 0.1N NaCl plus Csl3a to determine

cesium removal at 25" c. cesium-based zeolites were corrected for the

cesium-sodium weight differential, then contacted with a solution con-

taining 0.1I[ CsCl plus 0.11/ NaCl plus Na22 to determine sodium re-

moval onto the same zeolite. Total exchange capacity was assumed to

be the sum of sodium plus cesium loading. The solution to zeolite ratios

were adjusted to yield statistically reliable Cs134 and Na22 counting rates

between original and final contacting solutions. Cation exchange

capacities for ciinopti lolite, AW-300 and Zeolon, determined in the

above manner, were substantiated by titration of H+-based samples

with a standard NaOH solution. Since the exchange capacities as deter-

mined by titration were within 5 per cent of the exchange capacity as

Teslr 1. Znotrrn Pnopnnrrps

MASS ACTION OF ZEOLITES 87I

determined by the double tracing technique, we must assume thatAW-300, Zeolon and clinopti lolite were in fact H+-based.

All zeolites were weighed after being water-saturated and oven-driedat 55o C. Cation exchange capacity determinations were based on theweight of the cooled zeolite after removal from the oven. The weighedzeolites contained the rn'eight per cent HzO shown in Table 2. At leasttwo days of contact t ime with shaking were allowed to attain zeolite-solution equil ibrium. Other results were obtained in a similar manner.

With the binary cesium-sodium system, for example, two grams ofsodium-based zeoiite were contacted with 80 ml of solution at 25" C.The ratios of cesium to cesium plus sodium in the contacting solutionswere varied from 1X 10-1 to 5 X 10-5, while total solution normality

TAsr,n 2. Ztot-tln CarroN Excnnrcr Clpecrrrns

Zeolite Sio:/Alzoa Capacity, meq/g wt. 7a HrO

4AXW4A13XAW-500AW-400AW-300ZeolonErioniteClinoptilolite

z

2 . 84-.)

G - /

9-1010

o

8-10

3 . 93 . 53 . 62 . 22 . 01 . 61 . 92 . 1r . 7

28222515129

1 2I J

12

was held constant at 1.0. Four to six zeolite samples with dif ierentcesium to cesium plus sodium ratios, in duplicate, were shaken for threedays, centrifuged and counted to determine the amount of cesium re-maining in the equil ibrium solution. Using the exchange capacity, theequivalent fraction of cesium on the zeolite could then be computed byassuming that the cesium removed from the equil ibrium solution wasadsorbed on the zeolite.

Binary results were plotted as equivalent fraction of strontium orcesium on the zeolite vs. the equivalent fraction of strontium or cesiumin the equil ibrium solution. The latter scale also represents strontium orcesium normality in the equil ibrium solution because total solutionnormality was held constant at 1.0. This type of plot allows the readerto determine zeolite column loading directly in univalent-univalent ordivalent-divalent systems if the cesium or strontium normality ratioin the influent solution is known. Zeolite loading from an influentsolution in a column system is synonymous with zeolite loading from

872 L. L. AMES, JR.

the same composition of equil ibrium solution in an equil ibrium system.

Zeolite loads in univalent-divalent systems cannot be directly deter-mined from the equil ibrium data. The use of a k value, or mass actionquotient is required (Walton, et al., 1961). A definit ion of k in the 1.0

normal strontium-sodium svstem is.

f "To,s'..

,)("normalitv Na)'o:ffirr,\meq (Na f Sr),r

'

where z is the zeolite and s is the equil ibrium solution. The assumption

is made in using concentration terms for the solution, uncorrected for

activity, that the activity terms cancel, as do activity coefficients of the

cations on the zeolite. This is a first approximation (Kitchener, 1955;

Amphlett and McDonald, 1956), but k obviously is not a true thermo-

dynamic equii ibrium constant. The thermodynamics of zeolite cation

exchange equil ibria wil l be the subject of a forthcoming paper.

An example of the computation required to determine zeolite loading

in the strontium-sodium system will i l lustrate the use of k values. Given

that the zeolite is 13X and the influent solution composition is 0.011/

Na+ olus 0.0021y' Sr2+:

normality of Sr _ 0.002

o.012: 0.167.

normality of Sr plus Na

From F ig . 7 , k f o r 13X a t 0 .167 :8 .5 .Now

. (Sr,)(NaJ'tt :

(\Tul(stJ '

where fractions of strontium and sodium on the zeolite are Sr, and Na,,

respectively, and Nau and Sru are sodium and strontium equil ibrium

solution normalit ies. Thus,(0.01)2 (Sr")

8.s: (x) f f i and X:r70: f f i or (SrJ: (Na) ' (170) '

By definition,

Rearranging,

( N a , ) , * * r * u , l - * : 0 .l7O I r0

Solving with the quadratic equation,

(Na) * 170(Na,) '9: L

-h' +/ (ia)' * h: (Na)

MASS ACTION OF ZEOLITES 873

Only the positive root is real, so (Na,) :0.0738 and (Sr,) :0.9262. Thetotal capacity of 13X is 3.6 meq Sr/g. Thus (0.9262) (3.6):3.33 meqSr/g 13X. If the column weight was one kg, column capacity would be3333 meq Sr or 1667 liters of the above 0.002N Sr influent.

The reader should take care when using the curves to determinezeolite loading with solutions of greater than 1.0 total system normality.Activity coefficients of the various cations tend to diverge above 1.0normal (Harned and Owen, 1950). Due to the tendency of the binarycurves to flatten as the load on the zeolite increases, errors on the upperregion of the curves can amount to plus or minus five per cent of theindicated values.

Several sactions in the ternary system hydrogen-sodium-cesium weredetermined for clinopti lolite by another technique. Small, two ml (1.5 g)columns of clinopti lolite were placed in 15 ml lusteroid tubes. Two orthree pin holes were made in the bottom of the lusteroid tubes and 250ml of contacting solution was added, requiring eight to ten hours to passthrough the two ml column. The loaded clinopti lolite column was washedwith distilled water, the holes in the tube base sealed, and the wholecolumn counted in a NaI well crystal. A comparison of the activity on thetwo ml column with the activity in two ml of influent solution cotaininga known amount of non-radioactive cesium, hydrogen and sodium yieldedthe load of the traced constituent on the column. The capacity of theclinoptilolite was known, requiring that only the cesium and sodiumIoading be determined. The sum of cesium plus sodium subiracted fromthe total exchange capacity of the clinoptilolite was assum.ed to repre-sent hydrogen loading. Results in the hydrogen-sodium-cesium systemwere plotted on a standard ternary diagram. Composition of the equi-l ibrium solution (the influent solution in this instance) and compositionof the equilibrium loading on the zeolite are related in a manner similarto a ternary salt-solution diagram.

RBsulrs AND DrscussroN

Table 2 gives the total exchange capacities of each zeolite used in thestudy. It is necessary to know the total zeolite capacity to be able tocompute the fraction of zeolite loading, which is the ordinate in thefollowing figures.

Table 2 shows a general trend of decreasing cation exchange capacitywith increasing sil ica to alumina ratio. The greater the number of(AIO4)6- substitutions for (SiOa)a-, the greater the number of anionic sitesper unit weight. The net result, everything else being equal, is a largerexchange capacity/unit weight of zeolite.

Figures 1 through 4 show binary equilibrium in the systems cesium-

874 L. L. AMES, JR.

Equivalent Fraclion In [quilibrium Solullon

Frc. 1. The efiect of sodium on the equilibrium cesium loading of 4AXW,

13X, AW-300, AW-400, AW-500, Zeolon, erionite and clinoptilolite.

0dmr 0m0t oml 00I 0l

me cs- m ( c s r n

Equivalent Fr@tion in tquilibriun solution

Frc. 2. The efiect of potassium on the equilibrium cesium loading of 4AXW'13X, AW-300, AW-4100, AW-500, Zeolon, erionite and clinoptilolite.

Ere! :-{

; , -

II

€Be

" 001

0(Dl

mq csmE {Cs + Na)

MASS ACTION OF ZEOLITES 6 / 5

t 3lat - l a

- 001

? "-.lt

a t {

I

001mq cs

meq tcs + Rbl

[quival0nl Fraction in [aulllbriun Solothn

Frc. 3. The efiect of rubidium on the equilibrium cesium loading of 4AXW,13X, AW-300, AW-400, AW-500, Zeolon, erionite and clinoptilolite.

l 0

0 l

omr omt 0m o0l

dfl*.itquivalent Fradion ln tqullikium Sddion

Frc. 4. The effect of hydrogen on the equilibrium cesium loading

of AW-300 Zeolon and clinoptilolite.

0 l

876 L. L. AMES, JR.

sodium, cesium-potassium, cesium-rubidium and cesium-hydrogen, re-spectively. Only the zeolites AW-300, Zeolon and clinoptilolite weresufficiently acid-resistant, as indicated by acid-base titrations, to insurethat the necessary hydrogen-basing was feasible. Figure 5 shows thestrontium-calcium system. All of the above are univalent-univalent ordivalent-divalent systems and system equil ibrium distributions can beread directly from these figures. If the solution composition is known,the zeolite cation composition may be read directly, or vice versa. Ifow-ever, solution-zeolite equil ibrium relationships cannot be taken directlyfrom Fig. 5, the strontium-sodium system. A computation such as that

o m l o m l 0 0 I 0 l l 0

meq Sr

"'.*" r*,."'.,lii*n,t"] *,*-Frc. 5. The effect of calcium on the equilibrium strontium loading of 4AXW,

13X, AW-300, AW-400, AW-500, Zeolon, erionite and clinoptilolite.

given in a previous example is necessary, using the strontium-sodiumk values of Fig. 7. Figure 8 presents k values for the system strontium-hydrogen.

As shown in Figs. 5 and 6, all of the binary systems should terminateat full loading with the 1.01[ cesium or strontium equil ibrium solution.Since traced cation to competing cation ratios of less than 0.1 were ofprimary interest, no points above that ratio were determined except infhe case of Figs. 5 and 6.

Data from the ternary system hydrogen-sodium-cesium are given inFig. 9. The same cesium content of the equil ibrium solutions are con-

I

> 1 3

P ;1.F gIT

-:-

J2-

- t?gt=E l r

N-

a

t g -

d l +

E l9t {

s-

Eq0hdenl Frdlon In Equllifr ium Solutlon

Fro. 6. The efiect of sodium on the equilibrium strontium loading of 4AXW'13X, AW-300, AW-400, AW-500, Zeolon, erionite and clinoptilolite.

N S rN { S . + M l

l0

O Ioml

kmal Fracllon d Sfontlum In lne Inlluenl Solotion

Frc. 7. The efiect of sodium on the strontium mass action quotient k, of 4AXW'

13X, AW-300, AW-400, AW-500, Zeolon, erionite and clinoptilolite.

-4qlr-mq{Sr I Nd

878 L. L. AMES, IR,

nected with a solid l ine. Related equil ibrium zeolite loadings are con-nected with dotted l ines. Some of the equil ibrium solution compositionswere deleted from the cesium-sodium and cesium-hydrogen binary joinsto avoid further cluttering of the diagram. The complex nature of theternary equil ibria is apparent from Fig. 9. It is evident also that thenumber of experiments required to understand thoroughly ternaryequlibria can be quite large.

In general, the mass action quotient is not a constant for a given cationas the zeolite approaches full loading with that cation (Samuelson, 1953).Rather, k for a given cation is a function of the activity of that cationon the zeolite and in the equilibrium solution. Consequently, only verygeneral conclusions may be drawn from the mass action quotients per se.Table 3, as an example, gives the cesium mass action quotients, defined as

lcs,llxa"l[Na,][cs"]

for several zeolites. The z and s refer to zeolite and equilibrium solutioncation concentrations. The 13X and 4AXW are cesium-selective at oneper cent loading, but rapidly become scdium-selective as cesium loadingprogresses. Note that clinopti lolite tends to maintain a relativeiy highcesium selectivity at 50 per cent cesium loading. The fact that the 13X

ilormat Fradion of Stonliun in the Influent Sotution

Frc 8. The efiect of hydrogen on the strontium mass actionquotient k, of AW-300, Zeolon and clinoptilolite.

MASS ACTION OF ZEOLITES

T,tern 3. Znor;lrn Crsruu Mnss Acrrox QuorrnNrs rN A CEsruM-Sonruu SvsrBu,q.r Or.rr .e.No Frltv /p ot Znourn Crsruu Lo,qornc

Zeolite 1/6 cesium loading 50/6 cesium loading

879

4AXW13XAW-300AW-400AW-500ZeolonClinoptiloliteErionite

5 0 42 . 5 2

126.3288.62 0 2 . 1170. 5149.0246.6

0 . 1 3 40 . 1 7 60 . 3 4

5 0 . 63 9 . 01 9 . 068 .344.7

and 4AXW curves cross between 10 and 50 per cent cesium loading is not

readily apparent from Fig. 1.The comparison of natural and synthetic zeolite species is of interest

in the cesium-sodium system. Zeolon and AW-300 are both mordenites'

Structural differences between the two mordenites include the absence

of "stacking faults" in the Zeolon, resulting in an efiective pore diameter

Eouilibriun Solution' cition composition

^ zeolite Equilibriu$" Exchangeable cation

7o conposition

1 0 2 0 3 0 4 0 5 0 6 0 7 0 m 9 0

Frc. 9. A portion of the ternary equilibrium system hydrogen-sodium-cesium on clinoptilolite.

880 L. L. AMES, rR.

of about 10 A (Anon., 1962). The AW-300, on the other hand has aneffective pore diameter of about + A. lltre effect of the structural differ-ences on the cesium mass action coefficient can be seen in Table 3.Not only are the AW-300 one and fifty per cent cesium loading valueslower than those of Zeolon, but the relative distance between the twovalues is greater for AW-300. However, AW-300 with its stacking faultsis the better media for the separation of cesium from potassium andrubidium.

Erionite and AW-400 also are the same zeolite species. Except for the

T,q.sln 4. Pnrorcrno eNo Acrunr CoruuN Cepecrrrns

Influent solution

0.002]rr' Sr2++5186+0.0Uy' Na+0.0021[ Srr++Srsf 0. 01.N Na+0.07 Sr2++Srs+o. t1[ Na+0.07N Srr++Sr85+0 tiy' Na+0.01,N Ns+fCstaf 1.01f Na+0.011[ Cs+f C5rufO.51[ Na+0.001N Cs++Cs l?4+1.01V NH40.001try' Cs+f Csra+1.0M NH{0.001N Cs+f C5ta+1 Otrr' K+0. 011y' Cs+{Csru+1. 01f K+0.001ir' Cs+f Cetu+1.1/tr Na+

Columnwt., g.

Grain sizerange, mm.

Predictedload, meq/g

3 3 (Sr)3. s (Sr)J . J ( D f '

3 s (Sr)0 7s (Cs)1 02 (Cs)0 .037 (Cs)0 . 0 1 1 ( C s )0 040 (Cs)0 143 (Cs)0 .2a0 (Cs)

Actualload, meq/g

3.2 (Sr)s.4 (Sr),. ) (Jr_l0 I (Sr)0 73 (Cs)1 . 0 1 ( C s )0 .03e (Cs)0 . 0 1 1 ( C s )0,0s0 (Cs)0 .14s (Cs)0 .2a1 (Cs)

13X4A4A4AClinoptiloliteClinoptiloliteAW-5004AXWAW-500ClinoptiloliteAW-400

5 . 55 5

5050505050505050

o 4 4 7o .4-o.7o .4-o.7

1 . 60. 25-1 .000 .25 -1 00

1 . 6t . o1 . 6

0 25-1 001 . 6

slightly lower cesium mass action quotients of natural erionite, AW-400and erionite values are comparable.

Mass action quotients for cesium generally decline as the size of thecompeting cation approaches that of cesium. Sodium, for example,furnishes less competit ion for cesium than does rubidium when presentin equal concentrations.

The large selectivity differences between stontium-hydrogen andcesium-hydrogen (see Figs. 4 and 8) suggest that a chromatographicseparation of alkali and alkaline earth metal cations could be easilyaccomplished in an acidic system. Note also from Fig. 5 that AW-500, achabazite, is effective for the separation of strontium and calcium, asreported previously by Noll (1933).

Several column experiments were used to verify that the binary datacould be used to determine zeolite loads or partial capacities in thosesystems. Table 4 compares predicted zeolite loading with actual zeoliteloading values obtained in column experiments with comparable flowrates at 25o C. Column capacities were computed at 50 per cent loadingby the method of Samuelson (1953). Note that the predicted load of 4Ain 1.6 mm (one-sixteenth inch) pellets does not agree with the actual

MASS ACTION OF ZEOLITES

Ioading capacity. Equil ibrium was not attained between contacting

solution and zeolite because the column flow rate was too fast for the

zeolite particle size. Only under the condition of zeolite-solution equi-

l ibrium can the equil ibrium data be used to predict column loads'

CoNcrusroxs

l\,Iass action quotients per se are of l imited value for the basic study

of cation exchange equil ibria on zeolitesf i.e., the determination of mass

action quotients constitutes only a first step in such a study. The quo-

tients are useful by themselves, however, for prediction of zeolite column

Ioading. Cation loading on the zeolite from multicomponent systems also

can be estimated if the approximation that the competing cation effects

are additive is assumed.The cation exchange equil ibria of only a small number of the many

zeolites reported in the l iterature are known. It is evident from the few

data available that the zeolites constitute a potentially highly-usefui

family of cation exchange media, especially when high selectivity is

imperative.

AcrNowlBtGMENTS

The author wishes to acknowledge the aid and helpful suggestions of

\{rs. Olevia C. Sterner in the laboratory. The cooperation of the Linde

and Norton companies in furnishing zeolites for this study is appreciated.

RBrnru.rcus

ANorvuous (1962) Norton has new molecular sieves. Chem. Eng- News, 49, ll, 52'

Auts, L. L., Jn. (1960) The cation sieve properties of clinoptilolite' Am' Minerol' 45,

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Iite. Am. M i.ner al'. 46' tl20-ll3l.--- AND K. C. KNorr, (1962) Loading and elution characteristics of some natural and

synthetic zeolites, fL S. Atomic Energy Comm., Document lfw-74609 (unclassified).

AuenleTT, c. B. aNn L. A. McDomer-o (1956) Equilibrium studies on natural ion exchange

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Hrruao, H. S. ,uro B. B. Ownr.r (1950) The Physicatr chemistry of Electrolyt'ic solutions,

Reinhold Publishing Co., N. Y.,395.

KrrcunNnn, J. A. (1955) Ion exchange equilibria and kinetics. A critique of the present

stateof thetheory.soc. Chem. Ind.Monog.I, Ionexchangeand,itsapplications,24-33.

Mrrunns, W. G. ar.ro L. C. WarsoN (1962) A waste disposal experiment using mineral

exchange on clinoptilolite. Atomic Energy Cana.d'a, Ltd.', Documen' AECL-1521 (un-

classified).Mencnn, B. W. (1960) The removal of cesium and strontium from condensate wastes

with clinoptilolite. I/. .5. Atomic Energy Comm. Documentll\{'-66276 (unclassified).

MonclN, J. M., D. K. JmnsoN ,l,ro J. D. SrnvnNsor* (1961) Fixation of radioactivity in

stable, solid media. I/. S. Atomic Energy Comm., Documen TID-713' 310-388'

881

882 L. L. AMES, JR.

Ntrsou, J.L., B.w. Mnncnn ero w. A. Hnxev (1960) solid fixation of highJevel radio-active waste by sorption on clinoptilolite. t/. S. Atomic Energy Comm., DocumentIfW-66796 (unclassified).

Nor,l, W. (1933) Geochemie des Strontiums, Chemie Erite,8,507-600.Seuunr,sox, O. (1953) Ion Erchangus.in Analyticd Chemistry, John Wiley & Sons, New

York,4G51.Tour.rNsoN, R. E. (1962) The Hartford program for management of highJevel waste,

U. S. Atomic Energy Comm., DocutnentEl\M-SA-25f5 (unclassified).WALroN, H. F., D. E, Joroaw, S. R. Saunov ,u.rp W. W. McKav (1961) Cation exchange

equilibria with divalent ions. J o u.r. P hy s. C hem. 65, 147 7 -1484.

Monuscrdpt ruefued, January 10, 1963; accepted. Jor publication, April Zg, 1963.