Expansible Mineral Having High Rehydration Ability
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Transcript of Expansible Mineral Having High Rehydration Ability
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7/24/2019 Expansible Mineral Having High Rehydration Ability
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Clays and Clay M inerals
Vol. 22 pp. 309-310. Pergamon Press 1974. Printe d in Great Britain
R E P L Y T O : C O M M E N T S O N A N E X P A N S I B L E M I N E R A L
H A V I N G H I G H R E H Y D R A T I O N A B IL IT Y
R e c e i v e d 6 F e b r u a r y 1974)
I n h i s C o m m e n t s , C o l e h a s p o i n t e d o u t t h a t h e a t i n g t i m e o f
1 h r w as s ho r t . I n th i s r ega rd , t he in f luence o f pa r t i c l e s iz e
s h o u l d b e c o n s id e r e d . O u r e x p e r i m e n t s u s ed a s a m p l e p a r -
t ic le s iz e < 2 /~m and the hea t ing was d one on a ve ry th in
f i lm on the g la ss sl ide . W e tho ugh t tha t I h r was long enou gh
to expe l a l l i n t e r l aye r wa te r . We have reexamined the
s ample and have found tha t i t ha s h igh capac i ty fo r
rehy dra t ion even a f te r hea t ing to a t l e a s t 830~ fo r 5 h r .
C o le s t a t e s tha t c e r t a in ve rm icu l i t es have a h igh capac i ty
to rehydra te s o long a s they con ta in s ome hydroxy l wa te r .
I ag ree w i th h im, bu t c e r t a in o the r ve rmicu l i t e s w i l l no t
rehydra te . I won de r i f i t is c e r t a in tha t t he re i s a r e l a t ion
be tween ex i s t ence o f hydroxy l wa te r and rehydra t ion .
R ecen t s tud ie s have conf i rmed tha t c e r t a in regu la r ly in t e r -
s t ra t i f i ed mine ra l s have h igh rehydra t ion ab i l i t y . Howeve r ,
de s p i t e th i s h igh rehydra t ion capac i ty the dehydroxy la t ion
p e a k s i n t h ei r D T A c u r v e s d o n o t o c c u r a t h i g h t e m p e r a t u r e
(C o le and Hos k ing , 1957 ; B r ind ley and Sanda lak i , 1963 ;
T o m i t a
e t a l . ,
1969 ; To mi ta an d Do zono , 1973 ; To mi ta
e t
a l . , 1 97 4) . M a n y m o n t m o r i l l o n i t e s a n d a l l h y d r a t e d h a l lo y -
s i te s do no t r ehydra te a f t e r hea t ing to c e r t a in t emp e ra tu re s
des p i t e r e t a in ing s ome hydroxy l wa te r . I s ve rmicu l i t e the
on ly m ine ra l wh ich wi ll r ehydra te a f t e r hea t ing un t i l a l l hy -
dro xyl wa ter is lost ?.
Wa lke r and C o le (1957) and Wa lke r (1961) repor t ed tha t
B a tav i t e does no t lo s e the l a s t t r a ce o f in t e r l aye r wa te r un t i l
abou t 800~C . In h i s C omments , C o le exp la ins tha t i t migh t
be expec ted tha t B a tav i t e wou ld rehydra te a f t e r hea t ing to
800~ Al th oug h in the i r fo rmer pub l i c a t io ns i t was no t
c l ea r ly me n t ione d tha t B a tav i t e pos s e s s ed s uch capac i ty , i n
the C om me nts i t is s t a t ed tha t B a tav i t e does pos s e ss a h igh
r e h y d r a t i o n c a p a c i t y . W h e n t h e m i n e r a l w a s a l l o w e d t o
rehyd ra te in a i r af t e r hea t ing to 800~ a 14 .2A re f l e c tion
typ ica l o f the un hea te d min e ra l was pa r t i a lly recove red . An
in te r s t ra t if i ed mine ra l f rom Iw a to inves t iga ted by Tom i ta
and Dozono (1973) comple te ly rehydra ted a f t e r hea t ing to
800~
S o m e r e a s o n s a r e c o n s i d e r e d f o r h i g h r e h y d r a t i o n c a p a -
c ity. As po in ted ou t by Gr anq u i s t an d Ken nedy (1967) , f luo r -
ide in hydroxy l s i t e s enhances the wa te r s o rp t ion capac i ty .
W r i g h t
e t a l .
(1972) sugges ted, for the same c lay s tudied by
G r a n q u i s t a n d K e n n e d y , t h a t t h e t h e r m a l l y a c t i v a te d s u b -
s t ance had p ro tons in the t e t rahe dra l vacanc ie s o f the oc ta -
hed ra l l aye r . In h i s C omm ents , C o le conc luded th a t t he
g r e a t e r r e h y d r a t i o n c a p a c i t y o f B a t a v it e a n d L l a n o v e r m i c u -
l i te ove r the ma te r i a l f rom Wes t C hes te r m igh t be due to the
fac t t ha t t he fo rm er con ta in no i ron in the oc tahedra l l aye r.
I t h ink th i s l a ck o f i ron i s one o f the rea s ons . Fo r example ,
t h e d e h y d r o x y l a t i o n p e a k o f n o n t r o n i t e o c c u r s a t a l o w e r
temp e ra tu re t han in the ca s e o f i ron - f ree ana logs .
T h e r e h y d r a t i o n o f m o n t m o r i l l o n i t e a f t e r h e a t i n g t o
t emp e ra tu re s up to 1000~ has been inves t iga ted by Gr im
and B rad ley (1948) and by Hi l l (1953) . They conc lud ed tha t
a f t e r p rehe a t ing to 800~ d ioe tahed ra l s mec t it e s do n o t
s how apprec iab le rehydra t ion . DTA curves o f s ome t r ioc ta -
hed ra l s mec t i t e s g ive dehyd roxy la t ion peaks a t h igh t em-
pe ra tu re s . Sapon i t e f rom Kruge rs dorp , Trans vaa l , Sou th
Afr i ca dehydroxy la t e s be tween 800 and 900~ and C a l i fo r-
n ia hec to r i t e a t abo u t 800~ (Schm id t and H eys tek , 1953).
S o m e s m e c t i t e s h a v i n g h i g h a m o u n t s o f M g i o n s i n t h e
oc tahedra l l aye r migh t be expec ted the re fo re to have h igh
rehydra t ion capac i ty . Unfo r tuna te ly , I cou ld no t ob ta in
pure s pec imens o f such k inds , and cou ld n o t inves t iga te
the i r c apac i ty to rehydra te . The p rob lem s a re l e ft fo r fu tu re
s tudy.
I s uppos e tha t one o f the m a in rea s ons fo r h igh
rehydra t ion capac i ty may be due to the mine ra l s t ruc tu re .
B a tav i t e ha s an AI :S i r a t io o f 1 :3 in i t s t e t rahedra l l aye r
(We is s and Hofmann , 1951) ; L lano ve rmicu l i t e a co r re -
s pond ing AI : S i r a t io o f 1 :2 (va n O lphen , 1965). C e r t a in in -
t e r s t ra t i f i ed mine ra l s w i th h igh rehydra t ion ab i l i t y have
fa i rly h igh s ubs t i tu t ion o f AI fo r S i t e t rahedra l ly (Tom i ta
e t
a l . ,
1 96 9; T o m i t a a n d D o z o n o , 1 97 3; T o m i t a a n d D 6 z o n o ,
1974) . I have found tha t a Tos ud i t e inves t iga ted by
Kanaoka (1968) ha s a h igh rehydra t ion capac i ty and a l s o
has a fa i rly h igh s ubs t i tu t ion o f A l fo r S i. Thus , s pec imens
hav ing h igh t e t rahedra l s ubs t i tu t ion o f AI fo r S i s eem to
have th i s r ehyd ra t ion ab i l i t y .
According to Tomita and Sudo (1968a, b) , a 2Mr ser ic i te ,
w h i c h h a d b e e n h e a t e d t o d e h y d r o x y l a t i o n te m p e r a t u r e s
(650-950~ was con verte d in to a regular ly in ters t ra t i f ied
s t ruc tu re by bo i l ing in a c id s o lu t ion fo r a f ew minu te s .
R e h y d r a t i o n a n d r e h y d o x y l a t io n t h e r e f o re o c c u r r e d i n t h e
hea ted s e r i c i t e unde r re l a t ive ly mi ld cond i t ions . Why i s i t
t h a t r e h y d r a t i o n a n d r e h y d r o x y l a t i o n o c c u r s o e a s i l y i n
hea ted s e r i c i t e ? Tomi ta and Dozono (1972) s ucceeded in
fo rming a regu la r ly in t e r s t ra t i f i ed mine ra l f rom dehydroxy -
l a t ed 2M t s e r ic i te by ex t rac t ion o f K ion w i th s od ium
t e t r a p h e n y l b o r o n a t r o o m t e m p e r a t u r e a n d p r e ss u r e. H e r e ,
r e h y d r a t i o n a n d r e h y d r o x y l a t i o n a g a i n o c c u r r e d i n t h e
dehydrox y la t ed s e ri ci te , t h i s t ime d u r ing ex t rac t ion o f K
ion f rom in te r laye rs .
We is s enbe rg pho to g rap hs o f s ome ve rm icu l i t es g ive d i f-
fus e s po t s , wh ich can be cons ide red ev idence tha t t he s e ve r -
micu l i t e s have d i s to r t ed s t ruc tu re s . Th i s d i s to r t ion may be
due pa r t ly to t e t rahedra l s ubs t i tu t ion o f AI fo r S i . Hea ted
s e r i c i t e s a l s o have d i s to r t ed s t ruc tu re s (Tomi ta and Sudo ,
1968b). Thes e d i s to r t ed s t ruc tu re s s eem to p lay an impor -
t a n t r o l e i n r e h y d r a t i o n a n d r e h y d r o x y l at i o n .
R ecen t ly , Tomi ta (1974) repor t ed tha t t he rehydra t ion
and rehydroxy la t ion p rope r t i e s o f r e c to r i t e a re s imi l a r to
thos e o f 2M s er ic it es . W hy a re the s e p rope r t i e s o f 2M s e r i-
c i tes d ifferent f rom lM seric ites? W e repo rted an in ters t ra t i -
f led mine ra l hav ing h igh rehydra t io n ab i li t y . We thou gh t the
p h e n o m e n o n w o u l d b e h e l p fu l f o r i n t e rp r e t a t i o n o f t h e o r i -
g in o f in t e r s t ra t i f i ed mine ra l s ; i t s e ems to be equa l ly pe r -
t i n e n t t o d i s c u s s i o n o f t h e p r o b l e m s o f h i g h r e h y d r a t i o n
capaci ty .
P u r e s p e c im e n s h a v i n g h i g h r e h y d r a t i o n a b i l it y s h o u l d b e
found in the near future . Studies on such specif iaens should
309
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310 Notes
establ i sh the reasons for the observed high rehydra t ion and
rehydroxyla t ion capaci ty .
The wri te r expresses his apprec ia t ion to Dr . W. F. Cole
for his Comments.
Institute of Earth Sciences
Kagoshima University
Kagoshima Japan
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