Experimental Investigation of On-Line Methods for ... - CDC stacks

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P L E A S E DO N O T R E M O V E F R O M L I B R A R Y

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B y E. G. Noble, D. E. S h a n k s , a n d D. J. B a u e r

R e p o r t of I nvestigations 8 9 9 1

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DEPARTMENT

D o n a l d Paul Hodel, Secretary BUREAU

OF MINES

R o b e r t C. H o r t o n , Director

n

C h l o r i d e

B y E. G. Noble, D. E. S h a n k s , a n d D. J. B a u e r

UNITED STATES

A l k a l i

O F T H E INTERIOR

Library of Congress Cataloging in Publication Data:

Noble, E. G. (Elaine G.) Solubilities of chloride salts of alkali and alkaline-earth metals when sparged with hydrogen chloride, (Report of investigations / Bureau of Mines ; 8991) Bibliography: p. 14, Supt, of Docs, no,: I 28.23: 8991, 1, Alkali metal chlorides—Solubility, 2. Alkaline earth chlorides — Solubility, 3» Hydrochloric acid. I, Shanks, D. E. (Donald E.). II. Bauer, D, J, (Donald J,), III, Title, IV, Series: Report of investi­ gations (United States, Bureau of Mines) ; 8991,

T N 23.U 43

[ T P 245.CS]

622 s [669% 028’ 3] 85-600179

CONTENTS Page A b s t r a c t « I n t r o d u c t i o n . ...................... ............................................................ M a t e r i a l s a n d e q u i p m e n t . ................................. ............ ...................... P r o c e d u r e ........ .............................................................................. P r e c i s i o n a n d a c c u r a c y ......... ................. .......................................... . R e s u l t s a n d d i s c u s s i o n . .......... ........................................................... C a l c i u m c h l o r i d e . . . . .................................................... .................. L i t h i u m c h l o r i d e . .................................................. .............. ......... M a g n e s i u m c h l o r i d e . ..... ............................................ ........ . P o t a s s i u m c h l o r i d e ........................................... .............................. S o d i u m c h l o r i d e . ..................... ................. Summary and c o n c l usions........................................................ R e f e r e n c e s ....................................... .............................................. A p p e n d i x A ....................................... ........ ............................ . A p p e n d i x B .......................................................... ...........................

1 2 3 3 4 5 5 6 9 9 12 13 14 15 16

ILLUSTRATIONS 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

S p a r g i n g a p p a r a t u s ......................... ........ ................................. S o l u b i l i t y of C a C l 2 as f u n c t i o n of H C 1 c o n c e n t r a t i o n a n d t e m p e r a t u r e i n th e C a C l 2- H C l - H 20 s y s t e m . ..... .................................................... T i e l i n e p l o t of d a t a f o r t h e C a C l 2- H C l - H 20 s y s t e m at 20° C ......... T i e l i n e p l o t of d a t a f o r the C a C l 2- H C l - H 2 0 s y s t e m at 40° C .... S o l u b i l i t y of L 1 C 1 as f u n c t i o n of H C l c o n c e n t r a t i o n a n d t e m p e r a t u r e i n t h e L i C l - H C l —H 20 s y s t e m ........... ......................... ............ T i e l i n e p l o t of th e d a t a f o r t h e L i C l - H C l - H 2 0 s y s t e m at 20° C .......... . T i e l i n e p l o t of the d a t a f o r th e L i C l - H C l - H 2 0 s y s t e m at 40° C ......... S o l u b i l i t y of M g C l 2 as f u n c t i o n of H C l c o n c e n t r a t i o n a n d t e m p e r a t u r e i n t he M g C l 2- H C l - H 20 s y s t e m ............................................... .. T i e l i n e p l o t of the d a t a f o r th e M g C l 2- H C l - H 2 0 s y s t e m a t 20° C . . . ......... T i e l i n e p l o t of the d a t a f o r the M g C l 2 - H C l - H 20 s y s t e m at 40° C ............ T i e l i n e p l o t of t h e d a t a f o r t h e M g C l 2 - H C l - H 2 0 s y s t e m at 60° C ............ S o l u b i l i t y of K C 1 as f u n c t i o n of H C l c o n c e n t r a t i o n a n d t e m p e r a t u r e i n the K C 1 - H C 1 - H 20 s y s t e m . .................................................................. S o l u b i l i t y of N a C l as f u n c t i o n of H C l c o n c e n t r a t i o n a n d t e m p e r a t u r e in t h e N a C l - H C l - H 2 0 s y s t e m . . . . . . . . . . . . . . . . ........................................

3 7 7 7 8 8 8 10 10 10 11 11 12

TABLES B —1. B-2. B-3. B-4. B-5.

C a C l 2- H C l - H 20 s y s t e m ..................................................... ... 16 L i C l - H C l - H 2 0 s y s t e m . .................................... ................ ... 16 M g C l 2- H C l - H 2 0 s y s t e m ........................................................ ....... ....... ....... 16 K.GI-HCI-H2O s y s t e m ( s o l u t i o n ) ......................................... ... ........ 17 N a C l - H C l - H 20 s y s t e m ( s o l u t i o n ) .............................. ......... ............ 17

U N I T OF M E A S U R E A B B R E V I A T I O N S U S E D IN T H I S R E P O R T atm

atmosphere

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SOLUBILITIES O F

CHLORIDE SALTS OF W H E N S P A R G E D WITH

ALKALI A N D ALKALINE-EARTH HYDROGEN CHLORIDE

METALS

By E. G. Noble, 1 D. E. Shanks, 2 and D. J. Bauer3

ABSTRACT The effects of h y d r o g e n c h l o r i d e (HC1) c o n c e n t r a t i o n and t e m p e r a t u r e o n the s o l u b i l i t y a n d h y d r a t i o n s t a t e of t h e a l k a l i c h l o r i d e s L i C l , N a C l , an d K C 1 a n d the a l k a l i n e - e a r t h c h l o r i d e s , M g C l 2 , and C a C l 2 w e r e i n v e s t i g a t e d by the B u r e a u of M i n e s . S a t u r a t e d a q u e o u s s o l u t i o n s of the chlorides were s p a r g e d w i t h HC1 gas at t e m p e r a t u r e s of 20°, 40°, and 60° C. I n c r e a s e d ICI c o n c e n t r a t i o n c a u s e d d e c r e a s e d salt s o l u b i l i t y be­ c a u s e of the c o m m o n ion e f f e c t . A q u e o u s s o l u b i l i t i e s for the chlo r i d e s of Ca, Li, Mg, K, and Na r a n g e d f r o m 42.6, 45.2, 35.2, 25.5, a n d 26.1 pet, r e s p e c t i v e l y , at 20° C to 56.9, 49.4, 37.6, 31.0, a n d 27.0 pet, r e ­ s p e c t i v e l y , at 60° C. In s o l u t i o n s s p a r g e d to HC1 s a t u r a t i o n , s o l u b i l i ­ ties f o r these c h l o r i d e s r a n g e d f r o m 22.4, 26.5, 3.0, 1.3, and 0.05 pet, r e s p e c t i v e l y , at 20° C to 53.2, 48.8, 28.3, 2.6, and 0.8 pet, r e s p e c ­ tively, at 60° C. T h e s o l u b i l i t i e s of L i C l and C a C l 2 in HCl s o l u t i o n w e r e h i g h b e c a u s e HCl s o l u b i l i t y is l o w in t h e s e s o l u t i o n s . The chlo­ r i d e s a l t s of Ca, Li, a n d Mg f o r m e d h y d r a t e s , w h i c h d e p e n d e d o n t e m p e r a ­ t u r e a nd HCl c o n c e n t r a t i o n . M o n o h y d r a t e s for LiCl, t e t r a h y d r a t e s and hexahydrates for M g C l 2 , and dihydrates, tetrahydrates, and hexahydrates for C a C l2 were obtained.

’ ' R e s e a r c h c h e m i st, S u p e r v i s o r y r e s e a r c h chem i s t . ■^Supervisory c h e m i c a l e n g i n e e r (retired). R e n o R e s e a r c h Center, B u r e a u of Mines, Reno, NV.

2

INTRODUCTION S e p a r a t i o n s a n d p u r i f i c a t i o n s c a n be enhanced in chloride hydrometallurgical systems by sparging crystallization with h y d r o g e n c h l o r i d e gas. F o r example, in t h e B u r e a u ’s h y d r o c h l o r i c a c i d p r o c e s s f o r p r o d u c i n g a l u m i n a f r o m clay, c r y s t a l ­ l i n e a l u m i n u m c h l o r i d e h e x a h y d r a t e of s u f f i c i e n t p u r i t y to m e e t a l u m i n u m i n d u s ­ t r y s t a n d a r d s is r e c o v e r e d f r o m i m p u r e p r e g n a n t l i q u o r b y the d e c r e a s e i n s o l u ­ b i l i t y c a u s e d b y h y d r o g e n c h l o r i d e gas addition. I m p l e m e n t a t i o n of s p a r g i n g c r y s t a l l i z a t i o n t e c h n o l o g y Is h a m p e r e d by a l a c k of s o l u b i l i t y and k i n e t i c d a t a on metal chloride-hydrogen chloride-water systems. T h e B u r e a u of M i n e s is e s p e c i a l l y in­ t e r e s t e d i n p r o m o t i n g r e s e a r c h i n the m e t a l l u r g y of e l e m e n t s of s t r a t e g i c a n d critical economic Importance. A recent p a p e r b y S h a nks and N o b l e (1_)4 p r e s e n t e d t h e r e s u l t s of s o l u b i l i t y and c r y s t a l c o m p o s i t i o n s t u d i e s of the c h l o r i d e s of cobalt, m a n g a n e s e , a n d nickel. In this s t u d y a n d the c l a y - H C l p r o c e s s for p r o ­ ducing alumina, there was insufficient information on the solubility and crystal c h a r a c t e r i s t i c s of a s s o c i a t e d e l e m e n t s t h a t m u s t b e s e p a r a t e d f r o m the e l e m e n t s of interest in the leach-purification sc h e m e . F i v e s u c h e l e m e n t s of c o n c e r n a r e l i t h i u m , sodium, pota s s i u m , m a g n e s i ­ um, and c a l cium. T h e g o a l s of this r e s e a r c h w e r e to e x ­ p a n d t h e d a t a b a s e for s p a r g i n g c r y s t a l ­ l i z a t i o n of c h l o r i d e s of the a l k a l i and a l k a l i n e - e a r t h elem e n t s , to d e t e r m i n e t h e s o l u b i l i t y of HC1 and the c h l o r i d e s in aqueous s o l u t i o n s , and to c o n f i r m that sparging crystallization p r o d u c e d the s a m e r e s u l t s as e q u i l i b r i u m d a t a I n the literature. C o n s i d e r a b l e d a t a are a v a i l a b l e o n the aqueous s o l u b i l i t i e s of the a l k a l i and alkaline-earth chlorides, and s o m e d a t a a r e a v a i l a b l e o n the s o l u b i l i t i e s i n ^ U n d e r l i n e d n u m b e r s in p a r e n t h e s e s r e ­ fer to th e i t e m s in t h e list of r e f e r ­ e n c e s p r e c e d i n g the a p p e n d i x e s .

m e t a l c h l o r l d e - H C l - H 20 systems. However, these data were gathered in l o n g - t e r m e q u i l i b r i u m tests u s i n g c l o s e d c o n t a i n e r s a n d p r e d e t e r m i n e d a m o u n t s of c o n s t i t u ­ ents. P u b l i c a t i o n s p r i o r to 1 9 5 6 - 5 7 a r e s u m m a r i z e d i n L i n k e - S e i d e l l (2). In m o r e recent publications, P o t t e r and C l y n n e reported the aqueous solubilities fo r NaCl, KC1, and C a C l 2 (3) a n d the s o l u b i l ­ i t i e s of NaCl and KC1 i n a q u e o u s HC1 (4_). The MgCl2-HCl-H20 system was studied by Dahne (_5) at t e m p e r a t u r e s of -55° to 80° C and b y B e r e c z and B a d e r (_6_) at 15° to 50° C. T h e s e d a t a s h o w that th e a l ­ k a l i and a l k a l i n e - e a r t h c h l o r i d e s de­ c r e a s e in s o l u b i l i t y w i t h i n c r e a s i n g HC1 c o n c e n t r a t i o n , but o n l y l i m i t e d d a t a w e r e c o l l e c t e d at 20° to 60° C and no k i n e t i c d a t a a r e avai l a b l e . In this s t u d y , the metal chloride-hydrogen chloride-water s y s t e m s w e r e s t u d i e d at 20°, 40°, an d 60° C. These temperatures uniformly cov­ er t h e e x p e c t e d o p e r a t i n g r a n g e of m e t a l chloride separations. At temperatures a b o v e 60° C, a p r e s s u r e s y s t e m w o u l d be n e c e s s a r y for the m e t a l c h l o r i d e s o l u ­ t ions to a b s o r b s u f f i c i e n t HC1. In m e t a l l u r g i c a l a p p l i c a t i o n s , k i n e t i c and c r y s t a l c h a r a c t e r i s t i c d a t a a r e im­ port a n t . K i n e t i c i n f o r m a t i o n is n e e d e d to d e t e r m i n e h o w r a p i d l y e q u i l i b r i u m is a chi e v e d . Crystallization schemes in­ v o l v e s p a r g i n g w i t h HC1 gas, and t h e f i n a l c r y s t a l f o r m is i m p o r t a n t for s o l i d ­ liquid separation and purification. Re­ p o r t s b y Shan k s and N o b l e (1) a n d S hanks, E l s ele, and B a u e r (7) s h o w e d th a t e q u i ­ l i b r i u m is r a p i d l y a c h i e v e d i n t h e C o C l 2 H C 1 - H 2 0, M n C l 2 - H C 1 - H 2 0 , N i C l 2 - H C l ~ H 2 0, and A 1 C 1 3 - H C 1 - H 2 0 systems, an d that s p a r g i n g and e q u i l i b r i u m s t u d i e s g a v e c o m p a r a b l e r e s u l t s (8- 1 0 ), thus a l l o w i n g e x i s t i n g s o l u b i l i t y d a t a to be u s e d to p r e d i c t s p a r g i n g r e s u l t s a n d v i c e versa. U n f o r t u n a t e l y , this is not u n i v e r s a l l y true. O n g o i n g r e s e a r c h b y the B u r e a u of M i n e s s hows that some systems, s u c h as C r C l 3- H C l - H 2 0 and F e C l 3- H C l - H 20, d o n ot e q u i l i b r a t e r a p i d l y and m u s t b e s t u d i e d w i t h time as a n a d d e d p a rameter.

MATERIALS AND EQUIPMENT S p a r g i n g w a s p e r f o r m e d i n a 3-L w a t e r jacketed borosilicate glass resin reac­ tion kettle with a four-port lid (fig. 1). Temperature was monitored with a m e r c u r y t h e r m o m e t e r m a r k e d i n 0.1° C in ­ crements. The circulator bath, pressure r e g u l a t o r s , f l o w m e t e r s , and s t i r r i n g a p ­ p a r a t u s w e r e d e s c r i b e d p r e v i o u s l y (V). Each experiment started with a satu­ rated s o l u t i o n of the m e t a l c h l o r i d e ( r e a g e n t g r a d e). R e a g e n t s u s e d to m a k e saturated solutions i n c l u d e d C a C l 2 * 2 H 20, LiCl, M g C l 2 * 6H2 0, KC1, a n d NaCl. The sparging gas was technical-grade hydro­ g e n c h l o r i d e , > 9 9 pet HC 1 (impurities: hydrocarbons, wa t e r , c a r b o n di o x i d e , and inert materials). R e a g e n t s u s e d for analytical purposes were O.lOOOfI HC1 [ s t a n d a r d i z e d at 25° C a g a i n s t 2 - a m i n o 2 ( h y d r o x y m e t h y l ) - l ,3 - p r o p a n e d i o l ( T R I S ) ], G . 1 Q Q 0 N c a r b o n a t e - f r e e NaOH, and s i l v e r n i t r a t e , A g N O j , A C S r e a g e n t grade. C r y s t a l - f r e e s a m p l e s of s o l u t i o n w e r e r e m o v e d f r o m the c r y s t a l l i z e r through a coarse-porosity, fritted-glass gas­ d i s p e r s i o n tube, 250 m m long, w i t h an 8m m - diam stem and a 12- m m - d i a m c y l i n d r i ­ c a l disk. V o l u m e t r i c f l a s k s u s e d for a n a l y s i s of c h l o r i d e salt s a m p l e s w e r e l O O - m L c a p a c i t y ±0.08 m L at 20° C. Hy­ d r o g e n and total chloride ion concentra­ tions were determined using an automatic titrating apparatus w ith a motor-driven burette, u t i l i z i n g a s t a n d a r d pH e l e c ­ t r o d e f or h y d r o g e n i o n t i t r a t i o n s and a

HCI

chloride ion-specific electrode f or chloride titrations. Reference elec­ tr o d e s were sleeve, double-junction, c a l o m e l - i n t e r n a l , w i t h salt b r i d g e f i l l ­ ing s o l u t i o n of s o d i u m a c e t a t e - s o d i u m n i trate.

p r o c : DURE

Saturated chloride solutions were pre­ p a r e d b y h e a t i n g 1 to 2 L of w a t e r to s l i g h t l y g r e a t e r t h a n the d e s i r e d t e m p e r ­ ature, slowly stirring in the chloride u n t i l e x c e s s s o l i d s r e m a i n e d for at l e a s t 24 h a f t e r the last ad d i t i o n , and c o o l i n g to the d e s i r e d temperature. The solu­ t i o n s w e r e m a i n t a i n e d at t e m p e r a t u r e s of 20°, 40°, or 60° C and s p a r g e d w i t h a m i x t u r e of HC1 and c a r r i e r g a s e s u n t i l s a t u r a t e d w i t h HC1. The HC1 passing t hrough the flowmeter was r e g u l a t e d at 10 ps l g a n d a d j u s t e d to a f l o w r a t e of 8 50 m L / m i n . T h e c a r r i e r gas, ai r or nitrogen, was r e g u l a t e d at 10 psig and

d e l i v e r e d at a fl o w r a t e of 200 m L / m i n t h r o u g h th e flowmeter. P r e v i o u s w o r k (7) h a d s h o w n that the u s e of a c a r r i e r g a s r e s u l t e d i n larger, p u r e r c r y s t a l s a nd f e w e r p r o b l e m s w i t h s p a r g e r tip p l u g g i n g . T h e s t i r r e r sp e e d wa s a d j u s t e d to t h e m i n i m u m sp e e d that w o u l d k e e p the s o l i d s in suspension. Th e HCI f l o w r a t e of 850 m L / m i n w a s the f a s t e s t f l o w that c o u l d be utilized without e x c e e d i n g the c o o l i n g c a p a c i t y of the c i r c u l a t o r (HCI a b s o r p ­ t i o n is e x o t h e r m i c ) and g a v e a r e a s o n a b l e s a m p l i n g fre q u e n c y . The c h l o r i d e salt s o l u t i o n w a s s a m p l e d p r i o r to spa r g i n g , an d h o u r l y u n t i l th e c o n c l u s i o n of the

4

experiment. A p p r o x i m a t e l y 5-mL s a m p l e s w e r e drawn from the slurry through a f r i t t e d - g l a s s g a s - d i s p e r s i o n t u b e to in­ s u r e t h a t no s o l i d s w e r e removed. The s o l u t i o n w a s a d d e d to a v o l u m e t r i c f l a s k ( 100±0.08 m L at 20° C) a p p r o x i m a t e l y h a l f f u l l of a w e i g h e d a m o u n t of water. The volumetric f l a s k w a s w e i g h e d a f t e r the sample was a d d e d a n d a g a i n a f t e r the f l a s k w a s f i l l e d to the 100 m L m a r k . T h i s p r o c e d u r e m i n i m i z e d loss of HG1 and a l l o w e d f or c a l c u l a t i o n of the w e i g h t of t h e s a m p l e a nd the d e n s i t y of the d i l u t e d sample. The specific gravity was deter­ m i n e d directly on solutions separated f r o m 20° C s l u r r i e s w i t h a M e t t l e r - P a a r S D M A 35 density meter, ±0.001 a c c u r a c y . S i n c e this i n s t r u m e n t c a n o n l y be u s e d in the 10° to 30° C range, the s p e c i f i c g r a v i t y of the 40° a n d 60° G s o l u t i o n s was determined by weighing a 5-mL s a m p l e o f the s o l u t i o n . To o b t a i n r e s i d u e s a m ­ ples, a p p r o x i m a t e l y 5 m L of s l u r r y w a s c o l l e c t e d w i t h a ladle. The solids were partially dried by blotting on glassf i b e r f i l t e r paper, a d d e d to t ared v o l u ­ m e t r i c f l a s k s h a l f full of w a t e r , and h a n d l e d i n t he s a m e m a n n e r as the l i q u i d samples. One-milliliter aliquots were withdrawn f r o m t h e v o l u m e t r i c flasks, w e i g h e d , a n d t h e w e i g h t w a s d i v i d e d b y the d e n s i t y of the solution. T h e HC1 c o n c e n t r a t i o n w a s d e t e r m i n e d b y d i l u t i n g a 1-mL a l i q u o t to

50 m L w i t h w a t e r a n d t i t r a t i n g w i t h s t a n ­ d a r d i z e d 0.1000ÎJ NaOH, The automatic t i t r a t o r d e t e r m i n e d the end p o i n t as the i n f l e c t i o n p o i n t of the t i t r a t i o n c u r v e and p r i n t e d o u t the v o l u m e of t i t r a n t c o n s u m e d i n r e a c h i n g t h e end point. Hy­ drogen chloride concentration was calcu­ l a t e d f r o m e q u a t i o n A-l in A p p e n d i x A, Metal chloride concentration was de­ termined by titrating a 1-mL aliquot w i t h s t a n d a r d i z e d 0 .1 00IJ s i l v e r n i t r a t e (AgNOj) and d e t e c t i n g the c h a n g e i n c h l o ­ ride concentration with a chloride spe­ cific ion electrode. The end-point vol­ u m e w a s c o n v e r t e d to m e t a l c h l o r i d e c o n ­ c e n t r a t i o n by e q u a t i o n A-2. Metal chloride concentration was checked by a gravimetric technique in w h i c h 2 5-mL a l i q u o t s w e r e d r i e d u n d e r h e a t lamps, h e a t e d to 2 0 0 ° C i n a m u f f l e furnace, cooled in a vacuum desiccator, an d w e i g h e d as the a n h y d r o u s c h l o r i d e . A t o m i c a b s o r p t i o n s p e c t r o s c o p y o n l ow m e t a l c h l o r i d e c o n c e n t r a t i o n s w a s u s e d to s u p p l e m e n t the g r a v i m e t r i c results. The experiments were terminated when HC1 s p a r g i n g c e a s e d to i n f l u e n c e the HC1 and c h l o r i d e salt c o n c e n t r a t i o n s . T h e w e t r e s i d u e and s o l u t i o n c o m p o s i ­ tions w e r e p l o t t e d on t r i a n g u l a r c o o r d i ­ n a t e paper, and tiel i n e s w e r e c o n s t r u c t ­ ed to d e t e r m i n e c r y s t a l c o m p o s i t i o n b y S c h r e i n e m a k e r s ’ w e t r e s i d u e m e t h o d (11).

PRECISION AND ACCURACY A potential accuracy problem was chemi­ c a l n o n e q u i l i b r i u m of t h e a n a l y z e d s o l u ­ tions. In c o n v e n t i o n a l e q u i l i b r i u m s t u d ­ ies, p r e m e a s u r e d q u a n t i t i e s of r e a g e n t s a r e s h a k e n i n c l o s e d c o n t a i n e r s for ex­ t e n d e d p e r i o d s at c o n s t a n t tem p e r a t u r e . Periodic readings determine w h e n the sys­ t e m s a r e i n e q u i l i b r i u m . W i t h the s p a r g ­ i n g t e c h n i q u e , c o n c e n t r a t i o n s of r e a g e n t s a r e c o n s t a n t l y c h a n g i n g , and HC1 c a n b e l o s t f r o m s o l u t i o n u n l e s s e q u i l i b r i u m is rap i d . However, measurements made after s p a r g e d s l u r r i e s w e r e a l l o w e d to s t a n d overnight remained unchanged from those —

f

.......

.......... ......-

................— —

---------------

^ R e f e r e n c e to s p e c i f i c m a n u f a c t u r e r s or b r a n d n a m e s d oes n o t i m p l y e n d o r s e m e n t by t he B u r e a u of M i nes.

t a k e n at the c e s s a t i o n of s parging , s h o w ­ ing t h a t the r e a c t i o n k i n e t i c s a r e f a s t and HC1 is n o t e a s i l y lost f r o m so l u t i o n . M e t a l c h l o r i d e and HC1 c o n c e n t r a t i o n s c h a n g e d b y less t h a n 0.1 pet. Bottle tests of 2- w e e k d u r a t i o n g a v e r e s u l t s a l ­ m o s t i d e n t i c a l to t h o s e of s pargi n g , an d both compared favorably with equilibrium d a t a f r o m p r e v i o u s work. T h e A g N O j t i t r a t i o n of c h l o r i d e c o n ­ tent r e p r e s e n t e d the p r e c i s i o n - l i m i t i n g step i n the s o l u b i l i t y d e t e r m i n a t i o n s . Se v e r a l h u n d r e d t i t r a t i o n s of 0.1000ÎÎ HC1 w i t h A g N 0 3 and N a O H w e r e m a d e d u r ­ ing this r e s e a r c h to d e t e r m i n e c h l o ­ r i d e and HC1 c o n c e n t r a t i o n s . Average v a l u e s of the titrant concentrations w e r e 0.09 9 1 ± 0.0010N for the A g N 0 3 and

5

0 . 1 0 0 0 ± 0.0005N f o r the NaOH. This r e p ­ resents a v a r i a t i o n of ±0.0 5 m L for the A g N O j and ±0.025 m L for the NaOH, and a n a c c u r a c y of 2 to 0.7 pet for c h l o r i d e and 10 to 0.4 pet for h y d r o g e n c o n c e n t r a ­ tions. S i n c e the c o n t r i b u t i o n of c h l o ­ r i d e f r o m t he HC1 m u s t be s u b t r a c t e d f r o m t h e t o t a l c h l o r i d e c o n c e n t r a t i o n , the two errors are additive. S o m e of the a n c i l l a r y m e a s u r e m e n t s had l a r g e r r e l a t i v e e r r o r s bu t h a d no b e a r ­ i n g o n t he p r e c i s i o n or a c c u r a c y of the solub i l i t y work. P r e v i o u s w o r k ha d s h o w n t h a t t he HC1 f l o w r a t e w a s not a n i m ­ p o r t a n t p a r a m e t e r at f l o w rates less than 1,300 m L / m i n (_7 ). The 850-mL/min f l o w r a t e h a d an e s t i m a t e d p r e c i s i o n of ±5 pet. S p e c i f i c g r a v i t y m e a s u r e m e n t s at 40° a nd 60° C s h o w e d c o n s i d e r a b l e s c a t t e r a n d v a r i e d as m u c h as ±3 pet; t h e r efore, t h e v a l u e s r e p o r t e d for s p e c i f i c g r a v i t y i n t a b l e s B-l to B-5, a p p e n d i x B, w e r e d e t e r m i n e d f r o m s m o o t h e d curves.

O t h e r s o u r c e s of er r o r w e r e minor. Pipetting errors were e l i m i n a t e d by w e i g h i n g the a l i q u o t and the to t a l s a m p l e and d i v i d i n g the w e i g h t of the a l i q u o t by the w e i g h t of on e o n e - h u n d r e d t h of the t o t a l s a m p l e to o b t a i n c o r r e s p o n d i n g l y a c c u r a t e vol u m e s . The volumetric flasks w e r e c e r t i f i e d to c o n t a i n 100 m L ±0.08 m L of s o lution, a m a x i m u m e r r o r of 0.0 8 pet. T h e b a l a n c e u s e d for w e i g h i n g the f l a s k s has an a c c u r a c y of 0.01 g ±0.006 g. T e m ­ peratures were measured with thermometers m a r k e d i n 0.1° C i n c r e m e n t s and e s t i m a t a b l e to 0.02° C. Observed temperature v a r i a t i o n s w e r e w i t h i n 0.05° C. E a c h t h e r m o m e t e r w a s c a l i b r a t e d a g a i n s t a set of N a t i o n a l B u r e a u of St a n d a r d s (NBS) c e r t i f i e d t h e r m o m e t e r s and read w i t h i n ±0.1° C of the c e r t i f i e d t e m p e r a t u r e in the 20° to 60° C range. Temperature var­ i a t i o n s of 0.1° C w o u l d lead to a m a x i m u m m e t a l c h l o r i d e c o n c e n t r a t i o n e r r o r of 0 . 1 pet.

RESULTS AND DISCUSSION T h e f i v e s y s t e m s v a r i e d i n th e i r re ­ s p o n s e to i n c r e a s e d t e m p e r a t u r e an d h y ­ drogen chloride concentration. Although all chlorides showed increased aqueous solubility with increased temperature, th e i n c r e a s e w a s g r e a t e s t for C a C l 2 , 42.6 to 56.9 pet, and l e a s t for s o d i u m c h l o ­ ride, 26.1 to 27.0 pet. HC1 a b s o r p t i o n w a s l o w e s t in the l i t h i u m c h l o r i d e s y s t e m and highest in the p o t a s s i u m a n d s o d i u m c h l o r i d e s y s t e ms. There are few solubil­ i t y d a t a i n the l i t e r a t u r e for t h e s e m e t ­ al chloride-hydrogen chlorlde-water sys­ tems at 20°, 40°, an d 60° C to c o m p a r e w i t h the d a t a f r o m this study. Ho w e v e r , t h e s o l u b i l i t i e s of the p o t a s s i u m and so­ d i u m c h l o r i d e sy s t e m s do n o t v a r y s i g n i f ­ icantly w i t h increased temperature. The 20° C d a t a c o m p a r e c l o s e l y w i t h the l i t ­ e r a t u r e d a t a for t h e s e s y s t e m s at 25° C (2^). The results c o n f i r m e d t h a t rapid e q u i l i b r i u m w a s a t t a i n e d in t h e s e s y stems w i t h HCl-sparging crystallization. D a t a for the fi v e s ystems at the te m ­ p e r a t u r e r a n g e s i n v e s t i g a t e d ar e s u m m a r ­ i z e d i n t a b l e s B-l to B-5. The informa­ tion in each table represents a composite of a n a l y s e s f r o m t h e s e v e r a l a n a l y t i c a l p r o c e d u r e s u s e d and w i l l b e d i s c u s s e d i n

th e f o l l o w i n g section. Fr o m these tabu­ la t i o n s , the s o l u b i l i t y c u r v e s i n f i g u r e s 2, 5, 8 , 12, and 13 and the t i e l i n e d i a ­ gr a m s i n f i g u r e s 3, 4, 6 , 7, and 9-11 w e r e plotted. Since p o t a s s i u m and s o d i u m c h l o r i d e s do n o t f o r m h y d r a t e s , the w e t residues f r o m the s ystems containing th e s e sa l t s w e r e not analyzed. CALCIUM CHLORIDE The published aqueous solubility data o n c a l c i u m c h l o r i d e shows d i s c r e p a n c i e s . P o t t e r a n d C l y n n e (_3) s t a t e that the d a t a reported in Linke-Seidell ( 2 ) ar e too high, e s p e c i a l l y at t e m p e r a t u r e s a b o v e 28° C. Additionally, Linke-Seidell re­ ported several different values for e a c h temperature increment between 30° and 45° C. P o t t e r and C l y n n e p r o p o s e that these differences a r e d u e to the h i g h v i s c o s i t y of the C a C l 2 sol u t i o n s , w h i c h a l l o w s sm a l l c r y s t a l s to r e m a i n s u s p e n d e d a l m o s t i n d e f i n i t e l y and causes d e n s i t y stratification. T h e i r m e t h o d for d e t e r ­ m i n i n g s o l u b i l i t i e s did no t d e p e n d on o b ­ t a i n i n g r e p r e s e n t a t i v e sa m p l e s of the f l u i d f o r a n alysis. Th e s a m p l e s a n a l y z e d i n this r e s e a r c h w e r e o b t a i n e d b y d r a w i n g

6

a r e p r e s e n t a t i v e s a m p l e of the r e a c t i o n s o l u t i o n t h r o u g h a f r i t t e d g l a s s tube. T h e t e c h n i q u e p r e v e n t s t h e i n c l u s i o n of s u s p e n d e d s o l i d s in t h e s a m p l e d solution. To p r e v e n t d e n s i t y s t r a t i f i c a t i o n of the r e a c t i o n s o l u t i o n , it w a s n e c e s s a r y to s t i r t he s a m p l e s v i g o r o u s l y . The data obtained showed solubilities between those reported by Linke-Seidell and P o t ­ t e r a n d C l y nne. E x t r a p o l a t i o n of the d a t a f o r 20°, 40°, a n d 60° C f r o m the s o l u b i l i t y c u r v e s of P o t t e r an d C l y n n e w a s r e q u i r e d for the com p a r i s o n . U n l i k e m o s t h y d r a t e d c h l o r i d e salts, c o m m e r c i a l c a l c i u m c h l o r i d e is n o t i n its m o s t h y d r a t e d form. The CaCl2 crystals i n a saturated aqueous solution are more h y d r a t e d t h a n t h e r e agent. Linke-Seidell a n d P o t t e r a n d C l y n n e a g r e e o n the t r a n ­ s i t i o n t e m p e r a t u r e s for th e c h a n g e of h y ­ d r a t i o n states: C a C l 2 •6H 2 0 «=± C a C l 2 • 4 H 2 0

(1)

a t 30.1° C , a n d C a C l 2 •4 H 20

C a C l 2 *2 H 2 0

(2)

at 45.1° C. Tieline da t a and visual ob­ servation confirmed that C a C l 2 c r y s t a l s precipitated from saturated aqueous solu­ t i o n i n t h e h e x a h y d r a t e f o r m at 20° C, t h e t e t r a h y d r a t e at 40° C, and the d i h y ­ d r a t e at 60° C. C a l c i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC 1 c o n c e n t r a t i o n at 20° C is t a b u l a t e d i n t a b l e B-l an d p l o t t e d i n f i g u r e s 2 and 3. T h e I n i t i a l s l o p e of t h e s o l u b i l i t y c u r v e (fig. 2) w a s - 1 . 0 p e t C a C l 2 /pe t H C 1 . T h e a q u e o u s s o l u b i l ­ i t y w a s 42. 6 pet C a C l 2 (Lin k e - S e i d e l l , 4 2 . 7 pet, P o t t e r a n d C l y n n e , 42.1 p e t ). M i n i m u m C a C l 2 s o l u b i l i t y of 22.4 pet oc­ c u r r e d at HC1 s a t u r a t i o n , 25.7 pet. The t r a n s i t i o n f r o m t h e h e x a h y d r a t e to the t e t r a h y d r a t e w a s at 34 pet C a C l 2 a n d 12 pet H C 1 . Tieline da t a in figure 3 show a c h a n g e i n h y d r a t e s b e t w e e n 12 and 18 pet HC1 concentration. Th e t r a n s i t i o n po i n t was confirmed by the change fr o m an exo­ t h e r m i c to a n e n d o t h e r m i c r e a ction. When t h e t r a n s i t i o n w a s made, the a b s o r p t i o n reaction was again exothermic. C a l c i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 40° C is

t a b u l a t e d i n t a b l e 1 an d p l o t t e d i n f i g ­ u r e s 2 and 4. Calcium chloride solubil­ i t y i n w a t e r w a s 55.0 pet. Linke-Seidell r e p o r t 53.4, 55.9, and 56.2 pet a n d P o t ­ ter a n d C l y n n e ' s d a t a i n d i c a t e 53.3 pet. M i n i m u m s o l u b i l i t y w a s 44.6 pe t at HC1 s a t u r a t i o n of 9.2 pet. The initial slope of the s o l u b i l i t y c u r v e in f i g u r e 2 was - 1 . 0 pet C a C l 2 /pet HC1. The transition f r o m C a C l 2 *4 H 2 0 to C a C l 2 *2H20 w a s m a r k e d by a sm a l l i n f l e c t i o n p o i n t at 47. 2 pet C a C l 2 , 7.2 pet HC1. B e t w e e n 6 . 8 a nd 7.2 pet H C 1 , t h e s p a r g i n g c r y s t a l l i z a t i o n w a s endothermic. At h i g h e r HC1 c o n c e n t r a ­ t i o n s , the c r y s t a l l i z a t i o n r e a c t i o n w a s e x o t h ermic. T i e l i n e d a t a s h o w t h a t the h y d r a t e c h a n g e o c c u r s b e t w e e n 47 . 4 pet C a C l 2 , 7.0 pet HC1, and 45 . 4 p e t C a C l 2 , 8.5 pet H C 1 . C a l c i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 60° C is t a b u l a t e d i n t a b l e B-l and p l o t t e d in f i g u r e 2. T h e r e s i d u e sam p l e s w e r e n ot analyzed because visual observation indi­ c a t e d that th e c r y s t a l s d i d n o t c h a n g e fro m the dihydrate form on dissolution in w a t e r and t h e y w e r e u n c h a n g e d at m a x i m u m H C 1 a b s o r p t i o n of 3.6 pet. The solubil­ i t y in w a t e r w a s 56.9 pet C a C l 2 ( L i n k e Seidell, 57.8 pet, P o t t e r and C l y n n e , 56.7 p e t ) . M i n i m u m c a l c i u m c h l o r i d e s o l ­ u b i l i t y w a s 53.2 pet at 3.6 pet HC1. T he s l o p e of the s o l u b i l i t y c u r v e w a s - 1 . 0 pet C a C l 2 /pet HC1. LITHIUM CHLORIDE L i t h i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 20° C is t a b u l a t e d i n t a b l e B- 2 and plotted in figures 5 and 6 . T h e L1C1 s o l u b i l i t y c u r v e in f i g u r e 5 is li n e a r w i t h a s l o p e of - 1 . 0 pet L i C l / p c t HC1. Aqueous LiCl s o l u b i l i t y w a s 45.2 pet. Minimum solu­ b i l i t y of 2 6 . 5 pet LiCl wa s o b t a i n e d at 18.6 pe t HC1. The viscous s o l u t i o n at this c o m p o s i t i o n w o u l d a b s o r b n o m o r e HC1. T h e r e is n o i n f l e c t i o n p o i n t i n t he c u r v e of t h e s o l u b i l i t y data, a nd no p h a s e c h a n g e is i n d i c a t e d i n th e t i e l i n e plot; t h e refore, o n l y a s i n g l e h y d r a t e f o r m e x i s t s at 20° C. T h i s r e s e a r c h did n o t i n d i c a t e w h e t h e r the h y d r a t e is the m o n o h y d r a t e or d i h y d r a t e b e c a u s e the tie li n e s d i d no t i n t e r s e c t at e i t h e r of

7

CaCl2, pet

6 0 1—

HCI, pet F I G U R E 2. - Solubility of C a C I 2 as function of HCI concentration and temperature in the CaCI 2-HCI-H20 system.

—

H 20 , pet

F I G U R E 3. - Tie I!ne plot of the data for the C a C I 2-HCI-H20 system at 20° C.

H 20 , pet

F I G U R E 4. - Tieline plot of the data for the C a C I 2-HCI-H20 system at 40° C.

l_iC l, p e t

8

HCI, pet F I G U R E S. - Solubility of LiCI as function of HCI concentration and temperature in the LiCI-HCI-H20 system.

HgO, pot

F I G U R E 6. - Tieline plot of the data for the LiCI-HCI-H20 system at 20° C,

HgO, pot

F I G U R E 7. - Tieline plot of the data for the LiCI-HCI-H20 system at 40° C.

9

those compositions. T h e m o n o h y d r a t e is a s s u m e d b e c a u s e t h e c o m p o s i t i o n of the r e s i d u e is m o r e a n h y d r o u s t h a n is the theoretical composition of L 1 C 1 * 2 H 20. T h e s c a t t e r in the t l e l i n e d a t a r e f l e c t e d t h e p r o b l e m s e x p e r i e n c e d in p r e p a r i n g the r e s i d u e s a m p l es. T h e v i s c o u s n a t u r e of the solution prevented adequate removal f r o m th e r e s i d u e , a n d the l o w H C 1 c o n c e n ­ t r a t i o n in th e s a m p l e s m a g n i f i e d the a n a ­ lytical errors. The U n k e - S e i d e l l data d o n o t s h o w the c o m p o s i t i o n of the s o l i d p h a s e at 20° C. References l i s t e d in Llnke-Seldell show phase changes in the r a n g e of 18.5° to 19.1° C for t h e d i h y ­ d r a t e to m o n o h y d r a t e c h a n g e a n d a r ange o f 93° to 100° C for the m o n o h y d r a t e to a n h y d r o u s change. Lithium c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 40° C is tabulated In table B-2 and plotted in figures 5 and 7. The L1C1 solubility c u r v e f o r 40° C has the s a m e s l o p e as the 20° C curve. T h e s o l u b i l i t y of L1C1 i n w a t e r w a s 4 7 .3 pet, the s a m e v a l u e r e ­ p o r t e d in L i n k e - S e i d e l l . Lithium chlo­ r i d e s o l u b i l i t y d e c r e a s e d to 4 1 . 6 p e t at m a x i m u m HC 1 s o l u b i l i t y of 5 . 5 pet. The t l e l i n e d a t a s h o w that the s o l i d p h a s e was L 1C1 *H2 0 . T h e r e is n o i n f l e c t i o n p o i n t in t h e s o l u b i l i t y c u r v e to i n d i c a t e a p h a s e ch a n g e. Lithium c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of H C1 c o n c e n t r a t i o n at 60° C is t a b u l a t e d in t a b l e B-2 a n d p l o t t e d in figure 6 . Aqueous LiCl s o l u b i l i t y was 4 9 . 4 pet; Linke-Seidell r e p o r t e d 49.6 pet. Extensive sparging r e s u l t e d in a n H C 1 s o l u b i l i t y m a x i m u m of 0.7- p e t at a l i t h i u m c h l o r i d e s o l u b i l i t y m i n i m u m of 4 8 . 8 pet. O n l y one r e s i d u e s a m p l e w a s a n a l y z e d an d its l o w HC1 c o n c e n t r a t i o n g a v e a n I m p r e c i s e tlel i n e . The resulting tleline indicated that l i t h i u m c h l o r i d e w a s p r e s e n t as the m o n o h y d r a t e i n the L i C l - H C l - H 20 s y s t e m at 60° C. Y o d i s u s e d t h e a b i l i t y of l i t h i u m c h l o r i d e to b r e a k the hydrogen chloride azeotropes in de­ veloping a process for producing anhy­ d r o u s h y d r o g e n c h l o r i d e ( 1 2 ). MAGNESIUM CHLORIDE M a g n e s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of H C 1 c o n c e n t r a t i o n at 20° C i s t a b u l a t e d in t able B - 3 a n d p l o t t e d in

f i g u r e s 8 a n d 9. M a g n e s i u m c h l o r i d e s o l ­ u b i l i t y i n w a t e r w a s 35.2 pet. (LinkeS e i d e l l r e p o r t e d 35.3 pet.) Sparging w i t h HC1 d e c r e a s e d the s o l u b i l i t y of M g C l 2 to 3.0 p e t at H C 1 s a t u r a t i o n of 36.3 pet. T h e M g C l 2 s o l u b i l i t y c u r v e in f i g u r e 8 is l i n e a r w i t h a s l o p e of - 1 . 0 pet M g C l 2/ p c t HC1 u p to a H C 1 c o n c e n ­ t r a t i o n of 16.6 pet. A small Inflection p o i n t o c c u r s at 25.5 pet HC1 a n d 11.9 p e t M g C l 2 a n d c o r r e s p o n d s to the t r a n s i ­ t i o n f r o m M g C l 2 *6H 20 to M g C l 2 *4H 20 in the s a l t e d - o u t c r y s t a l s . T i e l l n e d a t a in f i g u r e 9 s h o w the b r e a k p o i n t at th e same place. T a b l e B-3 c o n t a i n s the t a b u l a t e d d a t a of m a g n e s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of H C 1 c o n c e n t r a t i o n at 40° C. T h e d a t a a r e p l o t t e d i n f i g u r e s 8 a n d 10. The m a g n e s i u m c h l o r i d e s o l u b i l i t y i n w a ­ ter w a s 36.0 pet c o m p a r e d w i t h 36.5 pet In L i n k e - S e i d e l l . M i n i m u m s o l u b i l i t y wa s 15.3 p e t at H C 1 s a t u r a t i o n of 23.6 pet. T h e s o l u b i l i t y c u r v e In f i g u r e 8 w a s a l ­ m o s t linear, a n d the i n i t i a l s l o p e wa s -0.9 pet M g C l 2/pct HC1. The solubility c u r v e d i d n o t i n d i c a t e a c h a n g e i n the cr y s t a l s t a t e d u r i n g HC1 s p a r g i n g , and the t i e l l n e d a t a in f i g u r e 10 c o n f i r m that a l l c r y s t a l s w e r e i n the h e x a h y d r a t e form. M a g n e s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 60° C is t a b u l a t e d in t a ble B - 3 a n d p l o t t e d in f i g u r e s 8 a n d 11. The M g C l 2 solubil­ ity c u r v e i n f i g u r e 8 was l i n e a r w i t h a s l o p e of -0.9 p e t M g C l 2/pct HC1. Magne­ sium chloride solubility ranged from 37.6 p e t in w a t e r to 28.3 pet at HC1 s a t ­ u r a t i o n of 10.4 pet. Llnke-Seldell re­ p o r t e d M g C l 2 s o l u b i l i t y in w a t e r at 60° C as 37.9 p e t a n d D a h n e (5) r e p o r t e d 37.7 pet. T h e s o l u b i l i t y c u r v e f r o m D a h n e 's d a t a m a t c h e d the c u r v e f r o m the s o l u b i l ­ i t y d a t a f r o m this study. Tiellne data In figure 11 s h o w that c r y s t a l s s a l t e d out at 60° C w i t h HC1 s p a r g i n g are in t h e h e x a h y d r a t e form. POTASSIUM CHLORIDE P o t a s s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 20° C is t a b u l a t e d In t a b l e B-4 and p l o t t e d in f i g u r e 12. T h e Init i a l s l o p e of the s o l ­ u b i l i t y c u rve Is - 1 . 6 pet K C l / p c t HC1.

10

MgCle, pet

4 0 1—

F I G U R E 8. - Solubility of M g C I 2 as function of HCI concentration and temperature in the M g C I 2-HCI-H20 system.

H 2O, pet F I G U R E 9. - Tieline plot of the data for the MgCI 2-HCI-H20 system at 20° C.

H 20 , pet

F I G U R E 10.- Tieline plot of the data for the MgCI 2-HCI-H20 system at 40° C,

11

—

H 20 , pet

F I G U R E 11. - Tieline plot of the data for the MgCI 2-HCI-H20 system at 60° C.

35

F I G U R E 12. - Solubility of KCI as function of HCI concentration and tem­ perature in the K C I - H C I - H 20 system. T h e s o l u b i l i t y of the KC I In w a t e r w a s 2 5 . 5 pet (Llnke-Seidell also reported 2 5 . 5 pet) a n d o b t a i n e d a m i n i m u m of 1.1 p e t at 29.7 p et HCI. The KCI solubility increased slightly to 1.3 pet at HCI s a t u r a t i o n of 39.1 pet. Linke-Seidell

reported data for the system KC1-HC1-H2 0 at 25° C; the c u r v e p l o t t e d f r o m t h e d a t a is p a r a l l e l to the 2 0 ° C c u r v e a n d s h o w s a s l i g h t I n c r e a s e i n KCI s o l u b i l i t y at HC I sat u r a t i o n .

12

P o t a s s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of H C 1 c o n c e n t r a t i o n at 40° C is t a b u l a t e d i n t a b l e B - 4 and plotted in figure 12. T h e s o l u b i l i t y c u r v e is s i m i l a r to the 20° C curve, a n d the i n i t i a l s l o p e is - 1 . 5 pet K C l / p c t HC1. A q u e o u s s o l u b i l i t y w a s 28.4 p e t KC1 (com­ p a r e d to 28.6 p e t i n L i n k e - S e i d e l l ) . M i n i m u m KC 1 s o l u b i l i t y of 1.5 pet w a s at 3 5 . 0 pe t HC1. There was a slight in­ c r e a s e i n s o l u b i l i t y to 1.7 p e t at H C 1 s a t u r a t i o n of 3 6 . 5 pet. P o t a s s i u m c h l o r i d e c o n c e n t r a t i o n as a f u n c t i o n of HC1 c o n c e n t r a t i o n at 60° C is tabulated in table B-4 and plotted in figure 12. T h e s l o p e of the c u r v e Is - 1 . 5 pe t K C l / p c t H C 1 a n d is a p p r o x i m a t e l y p a r a l l e l to the 20° a n d 40° C curves. Potassium chloride solubility ranged from 3 1 . 0 pe t i n w a t e r to 2.6 pet at H C 1 s a t ­ u r a t i o n of 3 0 . 4 pet. Linke-Seidell re­ p o r t e d a q u e o u s s o l u b i l i t y at 60° C as 3 1 . 4 pet. SODIUM CHLORIDE Sodium function

chloride concentration as a of H C 1 c o n c e n t r a t i o n at 20° C

is t a b u l a t e d i n t a b l e B - 5 a n d p l o t t e d in f i g u r e 13. The aqueous solubility d a t a for N a C l r e p o r t e d i n L i n k e - S e i d e l l r a n g e s f r o m 26.3 pet to 28.2 p e t b e t w e e n 0° a n d 100° C. T h e s o l u b i l i t y c u r v e s f o r t h e N a C l - H C l - ^ O s y s t e m at 20° , 40° , a n d 60° C a r e p a r a l l e l a n d s h o w l i t t l e difference in solubility. When the tem­ p e r a t u r e of t h e s y s t e m i n crease d , HC1 c o n c e n t r a t i o n at s a t u r a t i o n was low­ ered. A t 20° C, t h e i n i t i a l s l o p e of th e s o l u b i l i t y c u r v e w a s - 1 . 4 pet N a C l / p c t HC1. The NaCl solubility ranged from 26.1 pet in w a t e r to 0 . 0 5 pet at 39.1 pe t H C 1 . Linke-Seidell reported NaCl solu­ b i l i t y in w a t e r as 26.4 pet. Sodium chloride concentration as a f u n c t i o n of H C 1 c o n c e n t r a t i o n at 40° C is t a b u l a t e d i n t a b l e B - 5 a n d p l o t t e d in f i g u r e 13. T h e i n i t i a l s l o p e of t h e s o l ­ u b i l i t y c u r v e w a s - 1 . 4 p e t N a C l / p c t HC1. Linke-Seidell reported aqueous solubility at 40° C as 26.7 pet. The aqueous solu­ b i l i t y w a s 26.6 p e t a n d t h e s o l u b i l i t y at 37.0 pet HC1 w a s 0.1 pet. Sodium chloride concentration as a function of HC1 c o n c e n t r a t i o n at 60° C

30

F I G U R E 13.. - Solubility of NaCl as function of HCI concentration and tem­ perature in the NaCI-HCI-H 20 system.

13

is t a b u l a t e d in t a b l e B - 5 i n f i g u r e 13. Th e s o l u b i l i t y a n i n i t i a l s l o p e of -1 . 3 H C 1 . The NaCl solubility

a n d p l o t t e d 27.0 pet in w a t e r cu r v e h a d pet) to 0.5 pet at p e t N a C l / p e t 30.2 pet. ranged from

( L i n k e - S e i d e l l , 27 . 0 HC1 saturation of

SUMMARY AND CONCLUSIONS

C a C l 2 *• L i C l . .. M g C l 2 .. K C 1 ____ NaCl...

20° C 22.4 26.5 3.0 1.3 .05

O

M g C l 2 , KC1, a n d N a C l were, as f o l l o w s , i n percent; Oo

Solubility data fr om hydrogen chloride s p a r g i n g of s a t u r a t e d s o l u t i o n s of a l k a ­ li and alkali n e - e a r t h chlorides agreed w i t h l i t e r a t u r e v a l u e s o b t a i n e d by c o n ­ v e n t i o n a l e q u i l i b r i u m testing. Fo r the s y s t e m s a n d c o n d i t i o n s r e p o r t e d , th e s o l ­ u b i l i t y d a t a f r o m th e s p a r g i n g c r y s t a l ­ l i z a t i o n m e t h o d a r e as v a l i d as the d a t a from the slower bottle-test equilibrium methods. Conventional equilibrium data c a n be u s e d to p r e d i c t the e f f e c t s of HC1 sparging on these aqueous chloride salts. T h e c h l o r i d e s of Ca, Li, Mg, K, and Na decreased in solub i l i t y and crys t a l ­ l i z e d o u t of s o l u t i o n w h e n s p a r g e d w i t h H C 1 gas b e c a u s e of the c o m m o n i o n e f ­ fect. T h e c r y s t a l l i z a t i o n wa s almost total for sodium and potassium chlo­ rides. Lithium chloride was least sus­ ceptible to s a l t i n g o u t b e c a u s e m u c h l e s s H C 1 w a s a b s orbed. Calcium chlo­ r i d e w a s s i m i l a r to l i t h i u m c h l o r i d e i n behavior, and magnesium chloride was s i m i l a r to sodium and potassium chlo­ rides. The e f f e c t of temperature on hy­ drogen chloride solubility was great­ e s t f or l i t h i u m c h l o r i d e an d l e a s t f o r sod i u m chloride. In s a t u r a t e d HCl, the saturation composition of C a C l 2 » LiCl,

44.6 41.6 15.3 1.7 .1

60° C 53.2 48.8 28.3 2.6 .8

Th e s a l t e d - o u t c h l o r i d e s of Na a n d K were anhydrous. Lithium chloride formed m o n o h y d r a t e cry s t a l s . Magnesium chloride f o r m e d the h e x a h y d r a t e i n s a t u r a t e d a q u e ­ ous s o l u t i o n s at 20°, 40°, a n d 60° C. At HCl c o n c e n t r a t i o n s a b o v e 26 . 0 pet at 20° C, th e t e t r a h y d r a t e w a s pre s e n t . Calcium c h l o r i d e f o r m e d th e h e x a h y d r a t e i n s a t u ­ r a t e d a q u e o u s s o l u t i o n s at 2 0 ° C a n d l o w c o n c e n t r a t i o n s of h y d r o c h l o r i c acid. T he t e t r a h y d r a t e w a s f o r m e d b e t w e e n HCl b e ­ 18 pet. tween concentrations of 12 and I n c r e a s i n g the t e m p e r a t u r e or the h y d r o ­ chloric acid concentration caused trans­ f o r m a t i o n to l o w e r h y d r a t e s . At 40° C calcium chloride formed the t e t r a h y d r a t e at HCl c o n c e n t r a t i o n s u p to 7.2 p e t a n d f o r m e d th e d i h y d r a t e at h i g h e r c o n c e n t r a ­ tions. On l y the d i h y d r a t e e x i s t e d at 60° C.

REFERENCES 1. Shanks, D. E», a n d E. G. Noble. Hydrogen Chloride Sparging Crystalliza­ t i o n of the C h l o r i d e Salts of Cobalt, M a n g a n e s e , and Nickel. B u M i n e s RI 8930, 1985, 19 pp. 2. Lin k e , W. F. S o l u b i l i t i e s of I n o r ­ g a n i c a n d M e t a l O r g a n i c Com p o u n d s . ACS, 4 t h ed., v. 1, 1957, 1487 pp.; v. 2, 1965, 1914 pp. (This is a r e v i s i o n a n d c o n t i n u a t i o n of the c o m p i l a t i o n o r i g i ­ nated by Atherton S e i de l l . ) 3. Po t t e r , R. W. II, a n d M. A. Clynne. S o l u b i l i t y of H i g h l y Soluble Salts in A q u e o u s M e d i a - Part 1, NaCl, KCl, C a C l 2 , N a 2S 0 4 , an d K 2 S 0 4 S o l u b i l i t i e s to 100° C. J. Res., U.S. Geol. S u r v . , v. 6 , 1978, pp. 701-705. 4. ______ . S o l u b i l i t y of N a C l a n d KCl i n A q u e o u s HC1 F r o m 20 to 85° C. J. Chem. Eng. Data, v. 25, 1980, pp. 50-51. 5. Dah n e , C. B e s t i m m u n g d e r L o s l i e h k e i t s i s o t h e r m e n des Syst e m s H C l - M g C l 2- H 2Q z w i s c h e n -5 5 u n d +80° C ( D e t e r m i n a t i o n of the Solubility Isotherms of the H C 1 M g C l 2- H 20 S y s t e m B e t w e e n -55° a n d 80° C). Z. A n o r g . u n d Allg. C h e m . , v. 371, 1969, pp. 59-73. 6 . B e r e c z , E., a n d I. Bader. Physiochemical S tudy of T e r n a r y A q u e o u s E l e c ­ t r o l y t e S o l u t ions, VII. V i s c o s i t i e s a n d D e n s i t i e s of the M g C l 2 - H C l - H 20 S y s t e m a n d t h e S o l u b i l i t y of M g C l 2 . A c t a Chim. Acad. Sei. H u n g . , v. 77, 1973, pp. 2 8 5 ­ 313.

7. Shanks, D. E., J. A. E i s e l e , and D. J. Bauer. Hydrogen Chloride Sparg­ ing C r y s t a l l i z a t i o n of A l u m i n u m Chlo­ ride H e x a h y d r a t e . B u M i n e s RI 8593, 1981, 15 pp. 8 . M a l q u o r i , G. I Sistemi AlClj-HClH 20, K C 1 - H C 1 - H 2 0 e K N 0 3- H N 0 3 - H 2 0 a 25° (The Systems A 1 C 1 3 - H C 1 - H 20, K C 1 - H C 1 - H 2 0 and K N 0 3 - H N 0 3 - H 2 0 at 25° III). A t tl. A c cad. Linc e i , v. 5, 1927, pp. 576-5 7 8 . 9. Seidell, W., a n d W. Fisc h e r . D ie Löslichkeit Einiger Chloride und Doppel­ chloride in Warrlnger S a l z s a u r e als Grundlage von Trennungen (The S o l u b i l i t y of Some C h l o r i d e s and D o u b l e C h l o r i d e s ln H y d r o c h l o r i c A c i d as a B a s i s of S e p ­ arations). Z. A n o r g . u n d Allg. Che m . , v. 247, 1941, pp. 367-383. 10. Brown, R. G., G. E. Daut, R. V. M r a z e k , a n d N. A. Gokcen. Solubility and A c t i v i t y of A l u m i n u m C h l o r i d e i n A q u e o u s Hydrochloric Acid Solutions. B u M i n e s RI 8379, 1979, 17 pp. 11. Schreinemakers, F. A. H. Graph­ ische Ableitungen aus den Lösungs­ Isothermen eines Doppelsalzes und seiner Komponenten und mögliche Formender Um­ w a n d l u n g s k u r v e ( G r a p h i c D e r i v a t i o n of the S o l u b i l i t y I s o t h e r m of D o u b l e S a l t s an d T h e i r C o m p o n e n t s a n d P o s s i b l e F orms of the T r a n s i t i o n C u r v e ) . Z. Phys. Chem., v. 11, 1893, p. 76. 12. Y o d i s , A. W. P r o c e s s for D e h y d r a ­ ting Acid Halide Azeotropes With Lithium Salts. U.S. Pat. 3,763,019, Oct. 2, 1973.

15

APPENDIX A A-l. - E q u a t i o n f o r c a l c u l a t i n g h y d r o ­ gen chloride concentration

A-2. - E q u a t i o n fo r c a l c u l a t i n g chloride concentration

R| = E j x C j X C 2 / C 3 X C 4 , where

R, = c o n c e n t r a t i o n of HC1, pet,

metal

R 2 = [(E2 x C 6 / C 7 ) - R 3 ](C5 /C4 ), where

R 2 = metal chloride concentration, pet,

1 1 = N a O H volume, mL,

E 2 = A g N 0 3 vo l u m e , mL,

C) = 364.6 = m e q - w t HC1 x volumetric flask volume x conversion f a c t o r w t - f r a c t i o n to wt-pct,

C 5 = meq-wt metal chloride x volumetric flask volume x conversion factor wtf r a c t i o n to w t - p c t . (554.93 fo r C a C l 2 , 4 2 3 . 9 2 f o r LiCl, 4 7 6 . 0 9 f o r M g C l 2 , 74 5 . 5 5 f or KC1, a n d 5 8 4 . 4 3 fo r N a Cl),

C 2 = 0.1000 = NaOH concen­ tration, _N,

C 6 = A g N Q 3 c o n c e n t r a t i o n , _N, C 3 = v o l u m e of a l i q u o t ti t rated, mL, and

C 4 = w e i g h t of s a m p l e t a k e n f r o m e r y s t a l l i z e r , g.

C7

and

v o l u m e of a l i q u o t t i t r a t e d w i t h A g N 0 3 , mL, correction for chloride con­ t r i b u t e d by HC 1 = E , x C 2 / C 3 .

16

APPENDIX B T A B L E B—1, - C a C l 2- H C l - H 20 s y s t e m Solution H C 1 , pet CaCl2 > pet 0.0 1.9 4 .5 6.9 12.0 18.2 22.2 25.1 25.7

42.6 40 .8 38.1 36 .0 34.1 27.5 23.9 22.3 22.4

0.0 2.7 3.8 6.1 6.8 7.0 7.2 8.5 9.2

5 5 .0 52.0 51.0 4 8 .5 47.7 47.4 4 7.2 45.4 4 4 .6

0.0 5 6.9 5 3.2 3.6 N A N ot a n a l y z e d .

sp g r 2Qd C 1.42 1.41 1.40 1.39 1.39 1.35 1.33 1.33 1.33 40° C 1.52 1.51 1.50 1.49 1.48 1.48 1.48 1.47 1.46 60° C 1.57 1.55

T A B L E B-2. - L 1 C 1 - H C 1 - H 20 s y s t e m

We t r e s i d u e H C 1 , pet C a C l 2 , pet NA NA NA NA 2.0 3.4 NA NA 4.3

NA NA NA NA 48.1 51.9 NA NA 52.1

NA NA NA 0.5 .2 .4 NA .5 2.9

NA NA NA 62.2 59.1 62.8 NA 69.4 66.3

NA NA

NA NA

Solution H C 1 , pet L1C1, pet 0.0 2.1 4.3 6.4 9.4 12.1 14.7 15.8 16.6 17.8 18.6

45.2 43.1 40 . 8 38.6 35.6 33.2 30.4 29.4 28.7 27.5 26.5

0.0 2.3 3.7 4.2 5.2 5.5

47.3 44.9 43.4 43.0 41.8 41.6

0.0 49.4 49.2 .3 .5 48.9 .7 48.8 N A Not an a l y z e d .

sp gr 20° C 1.29 1.28 1.28 l. 1.28 1.27 1® 7 1.26 1.26 1.26 1.26 40° C 1.32 1.32 1.31 1.31 1.30 1.30 60° C 1.32 1.32 1.32 1.32

Wet residue H C 1 , pet Liei, p et NA NA NA NA 4.4 4.2 5.0 3.7 5.4 4.9 NA

NA NA NA NA 50.5 54.4 5 4.4 5 7.8 56.4 56.6 NA

NA 0.9 1.5 1.6 1.7 NA

NA 57 . 0 55.1 55.5 55.9 NA

NA NA 0.2 NA

NA NA 60.3 NA

T A B L E B-3. - M g C l 2 -HCl-il20 s y s t e m Solution Wet residue HC1, M g C l 2 , sp SCI, M g C l 2 , pet p et gr DCt V*»lw> pet 2 0 '* € 35.2 NA NA 0.0 1.33 1.2 3 .0 32. 0 1.32 40.9 NA NA 6.4 28.7 1.30 1.29 3.6 37.5 8 .5 26.6 24.1 1.28 NA NA 11.1 13.0 2 2 . 2 3.9 38.6 1.27 NA NA 16.6 18.8 1.26 17.2 18.3 1.25 3.9 39.5 21. 4 14.8 1.24 5.8 36.8 NA 22.5 13.8 1.24 NA 11.9 25.5 1.23 6.4 37.0 11.1 NA NA 26.0 1.23 1 . 2 2 17.9 27.6 28.6 8.7 NA 30.4 7.0 1.22 NA 34.3 1.21 4.1 NA NA 3.0 1 . 2 1 17.4 28.9 36 . 3 N A Not a n a l y z ed.

Solution HC1, M g C l 2 , sp pet pet gr 40° C 0.0 36.0 1.35 2.3 34.0 1.34 5.2 31.2 1.33 6.1 30.3 1.32 9.0 27.4 1.31 11.6 25.2 1.30 12.2 24.7 1.30 14.6 1.29 22.6 17.9 19.7 1.28 21.4 17.1 1.27 22.2 16.4 1.27 23.6 15.3 1.26

W e t r esidue Solution HC1, M g C l 2 , HC1, M g C l 2 , sp pet pet pet gr pet 60° C NA 1.39 NA 0.0 37.6 36.2 1.38 1.1 1.4 39.8 2.3 1.37 38.8 3.4 34.5 1.9 32.0 40.6 1.35 6.1 1.34 2.9 7.4 30.9 39.7 2.8 1.33 40.4 8.5 29.9 1.32 3.8 38.4 10.4 28.3 3.9 38.8 4.2 39.5 4.3 39.3 4.5 39.5 4.0 39.8

We t r e s i d u e HC1, M g C l 2 » pet pet NA 0.5 1.0 1.7 .4 1.1 .8

NA 42.2 4 1. 5 4 1. 8 44.3 43.7 44.4

17

TABLE B - 4 . - K C I-H C I-H 2 O system ( s o lu t io n ) HC1, pe t 0.0 2.8 6.0 9.6 12.8 16.7 21.5 23.8 25.7 27.8 29.7 31.5 33.7 35.7 38.2 39.1

K C l , pet 20° C 25.5 20.8 15.9 11.0 7.1 4.8 2.5 2.0 1.7 1.3 1.1 1.1 1.1 1.1 1.2 1.3

sp gr 1.17 1.15 1.13 1.12 1.11 1.11 1.12 1.13 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20

HC1, pet 0.0 2.9 5.9 9.1 12.2 16.3 20.0 24.4 27.6 30.8 32.4 33.8 35.0 36.0 36.5

KCl, pet 40° C 28.4 23.9 19.2 14.3 10.7 6.7 4.3 2.7 2.2 1.7 1.6 1.6 1.5 1.6 1.7

sp gr 1.18 1.17 1.16 1.14 1.13 1.12 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.18 1.19

H C 1 , pet 0.0 2.5 5.2 8.2 10.9 14.1 16.9 19.5 21.8 24.1 26.5 30.4

K C l , pet 60° C 31.0 26.8 23.0 18.5 14.9 11.1 8.6 6.7 5.3 4.3 3.5 2.6

s p gr 1.20 1.18 1.16 1.15 1.14 1.13 1.12 _ 1.11 1.12 1.13 1.13 1.14

T A B L E B-5. - N a C l - H C l - H 20 s y s t e m (solution) H C l , pet 0.0 4.9 10.0 14.5 19.1 23.5 27.2 35.7 39.1

NaCl, pet 20° C 26.1 18.9 11.7 6.5 2.8 .85 .35 .05 .05

☆U.S. G PO: 1985-605-017/20,122

sp g r 1.20 1.17 1.14 1.12 1.12 1.13 1.14 1.18 1.19

H C 1 , pet 0.0 2.1 4.5 7.2 9.7 14.4 17.8 21.0 23.5 25.6 27.7 29.2 35.8 37.0

NaCl, pet 40° C 26.6 22.7 19.8 16.2 13.0 7.7 4.9 2.6 1.5 1.0 .6 .4 .2 .1

sp gr 1.20 1.19 1.17 1.15 1.14 1.13 1.12 1.12 1.13 1.13 1.14 1.15 1.18 1.18

H C 1 , pet 0.0 2.7 6.1 9.1 11.8 14.9 17.7 20.3 22.7 25.0 28.1 30.2

NaCl, pet 60° C 27.0 23.1 18.6 14.6 11.2 8.1 5.8 3.9 2.6 1.6 1.0 .8

s p gr 1.20 1.18 1.16 1.15 1.13 1.13 1.12 1.12 1.12 1.13 1.14 1.15

IN T . - B U . O F MIN E S , P G H . , P A, 2 8 I 2 3