PROTECTION
OF THE ENVIRONMENT
CRYSTALLIZATION PRECIPITATION
OF BATH
SODIUM
SULFATE
CONTAINING
FROM
AMMONIUM
I. Z. l~ifer, G. A. Rudova, and L. M. Chernyak
A SULFATE UDC 677.463.021.125.261.014.2+ 677.463.021.125.261.004.8
O v e r the s t r e t c h of a n u m b e r of y e a r s a t t e m p t s have been m a d e to e l i m i n a t e zinc sulfate f r o m the m a k e up of the p r e c i p i t a t i o n bath which is u s e d in the m a n u f a c t u r e of v i s c o s e fibres; it is a r e a g e n t which is in v e r y s h o r t supply and is v e r y e x p e n s i v e . In r e c e n t y e a r s , in connection with the s t r i c t r e q u i r e m e n t s of p r o t e c t i o n of the w a t e r basin, the p r o b l e m of r e p l a c i n g zinc by a l e s s toxic p r o d u c t has b e c o m e still m o r e u r g e n t . Technology* which, t o g e t h e r with an i m p r o v e m e n t in the qualitative and o p e r a t i o n a l c h a r a c t e r i s t i c s of m a n u f a c t u r i n g , does not r e q u i r e additionally i m p o r t a n t capital outlays p r e s e n t s much i n t e r e s t in its solution. This r e l a t e s p r i m a r i l y to p r o c e s s e s and equipment for the r e g e n e r a t i o n of the technological solutions, p a r t i c u l a r l y the c r y s t a l l i z a t i o n of sodium sulfate. It is known that a change in the component composition of the p r e c i p i t a t i o n bath leads to a s h a r p change in the e q u i l i b r i u m c u r v e s for sodium sulfate, and consequently, in the specific yield of the c r y s t a l l i n e p r o d u c t and the c o m p o s i t i o n of its solid p h a s e in c r y s t a l l i z a t i o n . T h e r e f o r e each s p e c i f i c c a s e r e q u i r e s new s y s t e m a t i c studies, which is v e r y lengthy and l a b o r i o u s . On the b a s i s of a p r e v i o u s l y t conducted a n a l y s i s of the s y s t e m Na2SO4-H2SO4-ZnSO 4 - H 2 0 and calculational r e l a t i o n s h i p s for the solubility of Na2SO 4 and the specific yield of c r y s t a l l i n e product, an attempt was m a d e to extend the methodological a p p r o a c h to the s y s t e m Na2SO 3 H2SO 4 - M e S O 4 --H20 , w h e r e a l u m i n u m , which p r e s e n t s v e r y m u c h p r a c t i c a l i n t e r e s t s was used as the m e t a l . To do this, by a s e r i e s of refining e x p e r i m e n t s we d e t e r m i n e d the coefficients D O and 5 in the calculational equation for the solubility of Na2SO 4. The data obtained w e r e t r e a t e d by the c o r r e l a t i o n method. A high value of the c o r r e l a t i o n coefficient indicates a close connection between the solubility of Na2SO 4 and the A12(SO4)3 content of the solution. The r e g r e s s i o n equation has the following f o r m : AK 1 = 0.6K 3 at 5°C; AK1 = 0.7K 3 at 10°C, w h e r e AK 1 is the r i s e in solubility of Na2SO4, in g/100 g of solvent; and K 3 is the A12(SO4)3 content, in g/100 g of solvent. A s follows f r o m the r e g r e s s i o n equation, in the p r e s e n c e of H2SO4, A12(SO4)a r a i s e s the solubility of Na2SO4 as a function of t e m p e r a t u r e . A p p a r e n t l y this is explained by the fact that the dependence of both c o m ponents on H2SO4 content is a function of t e m p e r a t u r e . Allowing for the t e m p e r a t u r e f a c t o r , the r e g r e s s i o n equation will take the f o r m ~K1 = (D0 ÷ 00 K3
(1)
w h e r e D O is a coefficient which is n u m e r i c a l l y equal to 0.5; 5, coefficient which is n u m e r i c a l l y equal to 0.02; and t, t e m p e r a t u r e , in the r a n g e 0.20°C. The e x p e r i m e n t a l v a l u e s of Na2SO 4 solubility w e r e c o m p a r e d with the calculated f i g u r e s . did not exceed ~5%.
The deviations
Analytioal dependences for the calculation of o t h e r a c i d - s a l t s y s t e m s of the type Na2SO 4-H2SO 4 - M e S O 4 H20 can be obtained s i m i l a r l y . The l a s t t e r m of the solubility equation a s d e t e r m i n e d by the c o r r e l a t i o n method h a s a plus sign w h e n a n i n t e r a c t i o n of the s a l t s with each other is detected [Na2SO4-ZnSO ¢.4H20; Na2SO 4. A12(SO4) 3 • 24H20], and a negative sign if t h e r e is no such i n t e r a c t i o n , that is, only a s a l t i n g - o u t effect is d i s played. F u r t h e r t r e a t m e n t of the calculated and e x p e r i m e n t a l data made it p o s s i b l e to obtain s i m p l i f i e d e m p i r i c a l f o r m u l a s for calculating the specific yield of c r y s t a l l i n e Na2SO 4 (Gcr) f r o m technological solutions f r o m the *Work on f i b r e spinning in the Mogilev a r t i f i c i a l f i b r e plant was c a r r i e d out by V. I. M a i b o r o d a and c o - w o r k e r s . cG. A. Rudova and I. Z. l~ifer, Second International S y m p o s i u m on M a n - M a d e F i b r e s [in l ~ s s i a n ] Kalinin (1977), P r e p r i n t s , Vol. 3, p. 111. $ The u s e of NH 4 ions and other polyvalent m e t a l s , Mg o r Fe for e x a m p l e , is p o s s i b l e . T r a n s l a t e d f r o m K h i m i c h e s k i e Volokna, No. 4, pp. 51-53, J u l y - A u g u s t , 1981. Original a r t i c l e s u b m i t t e d July 8, 1980. 0015-0541/81/1304-0271507.50
© 1982 Plenum Publishing C o r p o r a t i o n
271
m a n u f a c t u r e of v i s c o s e fibre: for precipitation baths containing ZnSO4, 12 -< K3 -~ 20 when 290 ~ Ki -< 340; and 2.2 -~ KI/K 2 ~ 2,8; 4 --~ t --10 Gcr =(41.5~-~T~--5.5t--O,25Ks)A-(0.324-- 0.01 ~K~--0.00St) Kx
(2)
for precipitation baths containing A12(SO4)3, 20 ~ K3 ---
OF THE ENVIRONMENT
CRYSTALLIZATION PRECIPITATION
OF BATH
SODIUM
SULFATE
CONTAINING
FROM
AMMONIUM
I. Z. l~ifer, G. A. Rudova, and L. M. Chernyak
A SULFATE UDC 677.463.021.125.261.014.2+ 677.463.021.125.261.004.8
O v e r the s t r e t c h of a n u m b e r of y e a r s a t t e m p t s have been m a d e to e l i m i n a t e zinc sulfate f r o m the m a k e up of the p r e c i p i t a t i o n bath which is u s e d in the m a n u f a c t u r e of v i s c o s e fibres; it is a r e a g e n t which is in v e r y s h o r t supply and is v e r y e x p e n s i v e . In r e c e n t y e a r s , in connection with the s t r i c t r e q u i r e m e n t s of p r o t e c t i o n of the w a t e r basin, the p r o b l e m of r e p l a c i n g zinc by a l e s s toxic p r o d u c t has b e c o m e still m o r e u r g e n t . Technology* which, t o g e t h e r with an i m p r o v e m e n t in the qualitative and o p e r a t i o n a l c h a r a c t e r i s t i c s of m a n u f a c t u r i n g , does not r e q u i r e additionally i m p o r t a n t capital outlays p r e s e n t s much i n t e r e s t in its solution. This r e l a t e s p r i m a r i l y to p r o c e s s e s and equipment for the r e g e n e r a t i o n of the technological solutions, p a r t i c u l a r l y the c r y s t a l l i z a t i o n of sodium sulfate. It is known that a change in the component composition of the p r e c i p i t a t i o n bath leads to a s h a r p change in the e q u i l i b r i u m c u r v e s for sodium sulfate, and consequently, in the specific yield of the c r y s t a l l i n e p r o d u c t and the c o m p o s i t i o n of its solid p h a s e in c r y s t a l l i z a t i o n . T h e r e f o r e each s p e c i f i c c a s e r e q u i r e s new s y s t e m a t i c studies, which is v e r y lengthy and l a b o r i o u s . On the b a s i s of a p r e v i o u s l y t conducted a n a l y s i s of the s y s t e m Na2SO4-H2SO4-ZnSO 4 - H 2 0 and calculational r e l a t i o n s h i p s for the solubility of Na2SO 4 and the specific yield of c r y s t a l l i n e product, an attempt was m a d e to extend the methodological a p p r o a c h to the s y s t e m Na2SO 3 H2SO 4 - M e S O 4 --H20 , w h e r e a l u m i n u m , which p r e s e n t s v e r y m u c h p r a c t i c a l i n t e r e s t s was used as the m e t a l . To do this, by a s e r i e s of refining e x p e r i m e n t s we d e t e r m i n e d the coefficients D O and 5 in the calculational equation for the solubility of Na2SO 4. The data obtained w e r e t r e a t e d by the c o r r e l a t i o n method. A high value of the c o r r e l a t i o n coefficient indicates a close connection between the solubility of Na2SO 4 and the A12(SO4)3 content of the solution. The r e g r e s s i o n equation has the following f o r m : AK 1 = 0.6K 3 at 5°C; AK1 = 0.7K 3 at 10°C, w h e r e AK 1 is the r i s e in solubility of Na2SO4, in g/100 g of solvent; and K 3 is the A12(SO4)3 content, in g/100 g of solvent. A s follows f r o m the r e g r e s s i o n equation, in the p r e s e n c e of H2SO4, A12(SO4)a r a i s e s the solubility of Na2SO4 as a function of t e m p e r a t u r e . A p p a r e n t l y this is explained by the fact that the dependence of both c o m ponents on H2SO4 content is a function of t e m p e r a t u r e . Allowing for the t e m p e r a t u r e f a c t o r , the r e g r e s s i o n equation will take the f o r m ~K1 = (D0 ÷ 00 K3
(1)
w h e r e D O is a coefficient which is n u m e r i c a l l y equal to 0.5; 5, coefficient which is n u m e r i c a l l y equal to 0.02; and t, t e m p e r a t u r e , in the r a n g e 0.20°C. The e x p e r i m e n t a l v a l u e s of Na2SO 4 solubility w e r e c o m p a r e d with the calculated f i g u r e s . did not exceed ~5%.
The deviations
Analytioal dependences for the calculation of o t h e r a c i d - s a l t s y s t e m s of the type Na2SO 4-H2SO 4 - M e S O 4 H20 can be obtained s i m i l a r l y . The l a s t t e r m of the solubility equation a s d e t e r m i n e d by the c o r r e l a t i o n method h a s a plus sign w h e n a n i n t e r a c t i o n of the s a l t s with each other is detected [Na2SO4-ZnSO ¢.4H20; Na2SO 4. A12(SO4) 3 • 24H20], and a negative sign if t h e r e is no such i n t e r a c t i o n , that is, only a s a l t i n g - o u t effect is d i s played. F u r t h e r t r e a t m e n t of the calculated and e x p e r i m e n t a l data made it p o s s i b l e to obtain s i m p l i f i e d e m p i r i c a l f o r m u l a s for calculating the specific yield of c r y s t a l l i n e Na2SO 4 (Gcr) f r o m technological solutions f r o m the *Work on f i b r e spinning in the Mogilev a r t i f i c i a l f i b r e plant was c a r r i e d out by V. I. M a i b o r o d a and c o - w o r k e r s . cG. A. Rudova and I. Z. l~ifer, Second International S y m p o s i u m on M a n - M a d e F i b r e s [in l ~ s s i a n ] Kalinin (1977), P r e p r i n t s , Vol. 3, p. 111. $ The u s e of NH 4 ions and other polyvalent m e t a l s , Mg o r Fe for e x a m p l e , is p o s s i b l e . T r a n s l a t e d f r o m K h i m i c h e s k i e Volokna, No. 4, pp. 51-53, J u l y - A u g u s t , 1981. Original a r t i c l e s u b m i t t e d July 8, 1980. 0015-0541/81/1304-0271507.50
© 1982 Plenum Publishing C o r p o r a t i o n
271
m a n u f a c t u r e of v i s c o s e fibre: for precipitation baths containing ZnSO4, 12 -< K3 -~ 20 when 290 ~ Ki -< 340; and 2.2 -~ KI/K 2 ~ 2,8; 4 --~ t --10 Gcr =(41.5~-~T~--5.5t--O,25Ks)A-(0.324-- 0.01 ~K~--0.00St) Kx
(2)
for precipitation baths containing A12(SO4)3, 20 ~ K3 ---
