Separation of several oxoanions with a special chelating resin containing methylamino-glucitol groups

181

Reactive Polymers, 20 (1993) 181-188 Elsevier Science Publishers B.V., Amsterdam

Separation of several oxoanions with a special chelating resin containing methylamino-glucitol groups U. Schilde and E. Uhlemann

Universitiit Potsdam, Institut fiir Anorganische Chemie, 0-1571 Potsdam, Germany (Received October 11, 1992; accepted in revised form March 27, 1993)

Abstract

Certain oxoanions form complexes with polyols if the hydroxy groups have a sterically favoured position. Similar properties were found for the chelating resin Wofatit MK 51 which contains methylamino-glucitol groups. The sorption and desorption behaviour of this resin for aluminate, gallate, germanate, plumbate, vanadate, chromate, and molybdate was studied. In all cases, except chromium, the selective separation of these oxoanions is possible, even from strongly mineralized solutions. The elution was performed by means of hydrochloric acid because the complexes are not stable in acidic environment. In the case of molybdate, alkali hydroxide solutions were suitable for stripping. The breakthrough and elution curves will be discussed and the breakthrough capacities were calculated. Keywords: chelating resin; methylamino-glucitol group; ion exchange; oxoanions; aluminate;

gallate; germanate; plumbate; vanadate; chromate; molybdate

Introduction

Recently, the extraction of boric acid from brines by the chelating resin Wofatit MK 51 was reported [1,2]. Wofatit MK 51, a commercially available reagent (Chemie AG Bitterfeld/Wolfen), has a polymeric styrenedivinylbenzene matrix with 1-deoxy-l-(methylamino)-glucitol groups. _

CF~

CH 2 . -

OH

CH 2

N-

CH 2 - -

H

OH

i

i

i

OH

I

C

C---

C--

C--

I

I

]

I

H

OH

H

H

CH2OH

The hydroxy groups in the cis position proved to be able to form borate diol complexes; by this means, the selective separation of boric acid/borate was managed. On this basis, it seems interesting to study the sorption of other oxoanions from brines by Wofatit MK 51. Beside the extraction of boric acid, the chelating resin was used to separate silver from cyanide solutions [3]. In this work, the sorption and desorption behaviour of Wofatit MK 51 towards aluminate, gallate, germanate, plumbate, vanadate, chromate and molybdate in the presence of higher salt concentrations was studied.

0923-1137/93/$06.00 © 1993 - Elsevier Science Publishers B.V. All rights reserved

182 Weak acids, such as boric acid, are known to form complexes with diols. The complex formation goes along with an increase of acid strength. The latter effect was observed previously [4,5] during the reaction of arsenic acid with mannitol and sorbitol, but only to a minor degree compared with boric acid. Analogously, molybdic acid forms complexes with mannitol [6] and other hexitols [7], which are stable in acidic solution, but will be destroyed by addition of some alkali. The reaction of molybdate with cyclic and acyclic polyols proved to be identical [8]. If the hydroxy groups are in a favourable position, even two molybdenum atoms could be coordinated to the same ligand molecule [9]. Germanate is also known to react with polyols [10,11], and therefore it becomes possible to determine germanic acid by titration. The existence of a c o m p o u n d Hz[GezOsRn] (R = polyol) is supposed [12]. The complexes formed are stable even if ammonia or magnesium chloride are added. The expected precipitations do not occur. Borate and germanate are very similar in reaction with polyols, but the stabilities of germanium polyol complexes are higher than those of the borate complexes [13]. A chelating resin named Diaion CRB 0 2 (Mitsubishi Chem.) which contains 1-deoxy1-(methylamino)-glucitol groups was used for the separation of germanium from natural water [14], from zinc sulfate solution [15] and from catalysts [16]. Using this resin, some other oxoanions could also be separated [14]; however, only pure solutions without any salt content were studied. A similar resin, Amberlite XE-243 ( R o h m and Haas Co.), was r e c o m m e n d e d for the determination of germanium in Ge/Si-alloys. In this case, germanium is sorbed from 1 M N a O H solution whereas silicon is not bound to the resin [17]. A chelating resin with sorbitol groups is patented by Dow Chemical Co. for the separation of stannate, plumbate and gallate from alkaline solution [18]. It can be used also for

u. Schilde, E. Uhlemann/ React. Polym. 20 (1993) 181-188

the sorption of tellurate and arsenite, as well as of traces of iron from a 50% N a O H solution [19]. 1-Deoxy-l-(methylamino)-D-glucitol (Nmethylglucamin) in solution forms several complexes with lead ions [20]. Ligands of this kind are also suitable for complexing vanadium [21,22]; however, it should be taken into account that reduction of glucose or mannitol can occur at higher metal oxoanion concentrations [23]. In this paper, the sorption of a series of oxoanions by Wofatit NK 51 in column experiments is described, the composition of the complexes formed will be discussed elsehere.

Experimental Reagents and solutions

For the preparation of test solutions the commercially available reagents (Merck) of gallium(III) nitrate, germanium(IV) oxide, vanadium(V) oxide, molybdenum(IV) oxide and sodium chromate, all in analytical purity, were used. Sodium hexahydroxo-plumbate(IV) was synthesized by a standard procedure [24]. The salts were dissolved in a sodium hydroxide solution of the desired concentration (Table 1). The solutions were freshly prepared for each experiment, and the metal concentrations were controlled by comparison with Merck or Aldrich standards. The chelating resin is produced by the reaction of a chlormethylated styrene-divinylbenzene polymer with the amino sugar. It has a macroporous structure and a particle size of 0.3-1.2 mm. The chloride form, exclusively used in this work, shows a loading capacity for sulfate of 0.89 m o l / l . The water regain amounts to 45-55%. Further details are given in a patent of the producer [25]. The resin was allowed to swell for 24 h, and

U. Schilde, E. Uhlemann / React. Polym. 20 (1993) 181-188 TABLE 1 Breakthrough capacities of Wofatit MK 51 for the oxoanions, c = 0.001 mol/l Oxoanion

Medium

Salt

Breakthrough capacity g/1

Borate Aluminate Gallate

Germanate

Plumbate Vanadate Chromate

Molybdate "

1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 1 M NaOH 0.1 M NaOH 0.1 M NaOH 0.01 M NaOH 0.01 M NaOH 10% NaOH 10% NaOH 10% NaOH pH 6.0 10% NaOH pH 5.0 pH 5.0 1 M NaOH pH 4.6

1.54 10% Nacl 0.82 0.81 10% NaC1 0.53 0.98 1.50 10% NaC1 0.80 3.81 10% NaC1 1.96 12.3 10% NaC1 4.50 13.8 10% NaCI 6.72 5.43 10% NaCI 2.29 0 10% NaCI 4.7 0 > 2.3 10% NaCI 0 0 10% NaCI 1.25

mmol/1 142 76 30 19 14 " 2l 11 52 27 169 62 190 92 26 11 0 92 0 > 44 0 0

13

Free amine form.

t h e n it w a s t h r e e t i m e s a l t e r n a t i v e l y l o a d e d w i t h 1 M HC1 a n d 1 M N a O H , r e s p e c t i v e l y . Finally, t h e resin w a s c o n v e r t e d into t h e c h l o r i d e f o r m a n d r i n s e d w i t h w a t e r until a c o n s t a n t p H 2,8 w a s o b t a i n e d . A f t e r loading, t h e r e s i n b e d w a s r i n s e d w i t h 20 ml w a t e r .

183 w e r e c o l l e c t e d by t h e f r a c t i o n c o l l e c t o r R e d i frac (LKB Pharmacia). The pH values were m e a s u r e d using t h e special e q u i p m e n t M V 870 f r o m Pr~icitronic D r e s d e n G m b H . T h e m e t a l s w e r e d e t e r m i n e d q u a n t i t a t i v e l y by the a t o m a b s o r p t i o n p h o t o m e t e r 1100 B ( P e r k i n - E l m e r G m b H ) with a n i t r o u s o x i d e / a c e t y l e n e f l a m e or an a i r / a c e t y l e n e f l a m e (in t h e case o f Mo).

Calculation T h e b r e a k t h r o u g h c a p a c i t i e s w e r e calcul a t e d a c c o r d i n g t h e following e q u a t i o n : breakthrough capacity = v o l u m e at t h e b r e a k t h r o u g h p o i n t x mass concentration/volume

o f resin

T h e p o i n t w h e r e the c o n c e n t r a t i o n o f t h e o u t f l o w i n g s o l u t i o n r e a c h e d 1 m g / 1 w a s cons i d e r e d as the b r e a k t h r o u g h point.

Results and discussion Aluminate and gallate T h e test s o l u t i o n c o n t a i n e d 1 m M a l u m i n a t e a n d gallate, respectively, in 1 M N a O H a n d with an a d m i x t u r e o f 10% N a C I . Fig. 1 shows t h e b r e a k t h r o u g h curves of a l u m i n a t e .J 30

~-25

Equipment F o r t h e e x p e r i m e n t s , 3 0 - c m l o n g glass c o l u m n s ( t y p e 300-15, T e c h n i s c h e s G l a s I1m e n a u G m b H ) w i t h a n i n n e r d i a m e t e r o f 15 m m w e r e used. T h e c o l u m n s c o n t a i n e d 20 ml s w e l l e d a n d p r e t r e a t e d resin. T h e flow r a t e d u r i n g l o a d i n g (fixed b e d ) , rinsing a n d elution w a s 1 m l / m i n . T h e s o l u t i o n s w e r e m o v e d t h r o u g h t h e c o l u m n by t h e p e r i s t a l t i c p u m p P e r p e x ( L K B P h a r m a c i a ) . F r a c t i o n s o f 10 ml

z 0

20

.. .:

pc

/

bz

w 10 (..) z 0 0 5 03

:; ~/, S'/ ~"

,y;"~" "' t/ i

0

400

800

1200

1600

•

2000

VOLUME, ML

Fig. 1. Breakthrough curves for loading with aluminate. Feed solution concentration, 27.0 mg AI l-l; 1 M NaOH; (zx) 10% NaCI; (o) without salt.

184

U. Schilde, E. Uhlemann /React. Polym. 20 (1993) 181-188

(9 6

Z

0

2,5

n-

Z tu

o

...........................................................

2 1,5

O O

~

tr

......

Z ,,,

0

3 2

z

1

O3 0,5 o3 ,< 0

Z 4

0

O o

I.-.

L 10

20

30

40

1

o3 03 ,< ~ 0

~'-

50 60 70 80 VOLUME, ML

90 100 130 150

10

30

50

60

70 100 150 VOLUME, ML

200

300

400

Fig. 4. Elution of gallate. Eluant, 1 M HC1.

Fig. 2. Elution of aluminate. Eluant, 1 M HC1.

with and without admixtures of NaCI. The salt containing solution breaks through at smaller bed volumes (19.5) than the pure aluminate solution (30 bed volumes). The reason for this behaviour is the blocking of the amine groups in the resin by chloride ions which are then, consequently, not available for aluminate ions. The elution of aluminium is performed with 1 M HCI (Fig. 2). For the loading of the resin with gallate, similar results (Fig. 3) were obtained. The breakthrough capacities of gallate, however, are somewhat smaller than for aluminate. If the resin is used in the free amine form, the

70 r 60

~ so z 40

°E 30I

breakthrough point is earlier than with the chloride-loaded resin. This is in agreement with the general theory of weak base ion-exchangers. In their deprotonated form these resins cannot bind anions from strongly alkaline solution. In this case only the sugar group is available for the sorption of the metalate ions. Indeed, the capacity of the resin is of the same order of magnitude as it was found for high salt-containing solutions (Table 1). The elution of gallium with 1 M HCI is shown in Fig 4. If the concentration of hydroxide ions in the gallate solution is too high [such as in a Bayer process leach solution (WNaOH = 42%)] the complex formation with the resin does not take place and loading of the resin with gallate becomes impossible. At lower hydroxide concentrations, aluminate and gallate are both sorbed by the resin (Fig. 5), but gallate firstly breaks through. A further separation is not possible because the two metals are simultaneously eluted with 1 M HC1 (Fig. 6).

Z iii

o

§ 03 03

3;

20~

Germanate and plumbate

, lO~1 0

400

800

1200

1600

2000

VOLUME, ML

Fig. 3. Breakthrough curves for loading with gallate. Feed solution concentration, 69.72 mg Ga l-a; 1 M NaOH; (zx) 10% NaC1; (*) without salt, free amine form; (o) without salt.

At low concentrations and in strongly alkaline solutions germanate and plumbate proved to exist as [Ge(OH)6] 2- and [Pb(OH)6] 2-, respectively. As expected from the literature [16], Wofatit MK 51 has an excellent binding capacity for germanium (Fig. 7).

U. Schilde, E. Uhlemann / React. Polym. 20 (1993) 181-188

185 .J 80 W 70: (.9 lJ_ 6 0 : 0 z 50 o 40 ,'r 30

0,8 i z- 0 , 6 -

0

/ O,4r

/

/,i

f

V

z

0

s

!

/

8 (.3

-,/

~'i

20

200

400

600 800 VOLUME, ML

1000

1200

1400

Fig. 5. Breakthrough curves for loading with gallate and aluminate. Feed solution concentration, 1 mmol AI or Ga 1 1: (o) gallate; ([3) aluminate.

The breakthrough points correspond to 52.5 (without salt) and 27 (with salt) bed volumes. Because of the favourable solubility, germanate could also be used in diluted sodium hydroxide solutions (0.1 and 0.01 M). In these cases the capacity increases still more. A remarkable enrichment of germanium was obtained by elution with hydrochloric acid (Fig. 8). Wofatit MK 51 is also suitable for the sorption of plumbate (Fig. 9). To avoid hydrolysis, NaOH of higher concentration (w = 10%) was used as solvent. The breakthrough points correspond to 28.5 (pure solution) and 12 (admixture of NaCI) bed volumes. Fig. 10

~

/"'

l(~e. ~ 0

p

"

S ~ O ~ q ~

0

400

" ~ -

800

1200

VOLUME,

1600

2000

ML

Fig. 7. Breakthrough curves for loading with germanate. Feed solution concentration, 72.6 mg Ge I l; 1 M NaOH; (A) 10% NaC1; (o) without salt.

8(

(.~

~z

g_ 6' I z ,,, 0

3

g2 0

~

0 10

20

30

40

50

60

70

80

90

1 5 0 200 6 0 0

VOLUME, ML

Fig. 8. Elution of germanate. Eluant, 1 M HCI.

200 (5 caw

~

3(

i

i

t

2,5 I

Iz w 1 o z 00 0,5 (o 09 0 ,<

160r z

0 cr' t.Z ILl 0 Z 0 0 03 03 .< ~; 10

20

30

40

50 60 70 80 VOLUME, ML

90 150 200

Fig. 6. Elution of gallate/aluminate; eluant: 1 M HCI; front: gallate; back: aluminate.

I i

8 120

,;, '2>

,~'

80

,/ 40

2,

0

400

800 1200 VOLUME, ML

1600

2000

Fig. 9. Breakthrough curves for loading with plumbate. Feed solution concentration, 190.5 mg Pb l-i; 10% NaOH, ( a ) 10% NaCI, (o) without salt.

U. Schilde, E. Uhlemann / React. Polym. 20 (1993) 181-188

186

>" 1 2

a. 2 , LI. 0 Z ; 0

0 z 0

.

.

.

.

.

.

.

.

.

.

.

.

[

0,9

m

n;

i.

'

1,~

Z IJA 0 Z 0 0 0,~ O3 < 2~ b

10

20

30

40

~ 0,6 O z O O 0,a co < N 0

70 100 3 0 0 4 0 0 5 0 0 700 9 0 0 VOLUME, ML

30

100 2 0 0 4 0 0 4 5 0 6 0 0 7 0 0 8 0 0 900

50

VOLUME, ML

Fig. 10. Elution of plumbate. Eluant, 1 M HCI.

Fig. 11. Elution of vanadate. Eluant, 5 M HCI.

shows the elution with 1 M HCI. In comparison with germanate larger volumes of the eluent are necessary for the complete elution of lead.

from solutions of medium pH but not from strongly alkaline solution. Moreover, the sorption and desorption of chromate are accompanied by changes of the colour, apparently caused by redox reactions. The elution with HC1 is slow. The colour of the resin at the beginning is yellow or orange, depending on the HC1 concentration, and then changes to colourless. Attempts to separate molybdate from 1 M N a O H were not successful. Batch experiments (Fig. 12) show that molydenum can be bound only at low pH values. But the kinetics of the complex formation is remarkably slow. This result was confirmed by experiments with the resin in a column (Fig. 13). The loaded resin exhibits a blue-green colour.

Vanadate, chromate and molybdate Vanadate, prepared by dissolving of V 2 0 5 in N a O H (w = 10%), was not bound by the resin. Inversely, at pH 6, 1840 ml (92 bed volumes) of a NaCl-containing solution pass the column before traces of vanadium are found in the outflow. The sorption of vanadium can be observed by the yellow colouring of the resin. If the starting solution has a higher vanadium concentration (c = 0.025 M), the vanadium breaks through after 40 ml solution. The reason for this fact is the formation of polyvanadates which are not complexed to the chelating resin. The elution of vanadium was performed by 5 M HC1 (Fig. 11). The colour of the resin was orange and during the elution it became colourless. The first eluates were of a yellow-green colour. The reduction of vanadium(V), catalyzed by acid, can be unequivocally concluded. Chromate could not be separated from mineralized solutions by Wofatit MK 51 and shows no tendency to form complexes with polyols. The resin only acts as a weak base anion-exchanger which sorbs chromate ions

~_1o o ~

.~

[]

u

[]

, 40~

zW

I,

oz

20~

[

J

o <

0

1

2

3

4

5

6

7

8

9

10

TIME, H

Fig. 12. Batch tests for loading with molybdate. Feed solution concentration, 95.9 mg Mo 1-1; 10% NaCI; (t3) pH 8.5; (o) pH 4.1; ( × ) pH 1.2.

187

U. Schilde, E. Uhlemann / React. Polym. 20 (1993) 181-188 References (.9 100

d 80

z 60 i, _o rr

FZ uJ 0 Z 0

40' i 20

)00

<1:

5:

0

400

800 1200 VOLUME, ML

1600

2000

Fig. 13. Breakthrough curve for loading with molybdate. Feed solution concentration, 95.9 mg Mo 1-1; 10% NaCI; pH 4.6. B e c a u s e t h e c o m p l e x e s a r e s t a b l e in t h e acidic r a n g e , t h e e l u t i o n m u s t b e p e r f o r m e d with NaOH.

Conclusions

T h e c h e l a t i n g r e s i n W o f a t i t M K 51 h a v i n g 1 - d e o x y - l - ( m e t h y l a m i n o ) - g l u c i t o l g r o u p s is s u i t a b l e f o r s e p a r a t i n g a l u m i n a t e , gallate, germanate, plumbate, vanadate, and molybd a t e f r o m b r i n e s w i t h h i g h e r salt c o n t e n t s . Best results were obtained for germanium. A l u m i n a t e , gallate, p l u m b a t e , a n d g e r m a n a t e a r e s o r b e d e v e n f r o m s t r o n g l y a l k a l i n e solutions a n d a r e r e a d i l y e l u t e d w i t h h y d r o c h l o rid acid. Vanadate and molybdate are separated f r o m w e a k acidic solutions. W h e r e a s v a n a d i u m is d e s o r b e d by acid, m o l y b d e n u m n e e d s alkali h y d r o x i d e . I n t h e c a s e o f t h e s e o x o a n ions, t h e e x c h a n g e p r o c e s s e s w i t h t h e r e s i n a r e a c c o m p a n i e d by c o l o u r c h a n g e s w h i c h a r e c a u s e d by r e d o x r e a c t i o n s .

Acknowledgement

The authors gratefully acknowledge f i n a n c i a l s u p p o r t o f this w o r k b y Deutsche Forschungsgemeinschaft.

the the

1 U. Schilde and E. Uhlemann, Extraction of boric acid from brines by ion exchange, Int. J. Miner. Process., 32 (1991) 295-309. 2 U. Schilde and E. Uhlemann, A simple method for the control of ion exchange processes with boric acid using specific chelating resins, React. Polym. 18 (1992) 155-158. 3 L. Feistel and M. Knothe, Verfahren zur Abtrennung von Silber aus cyanidischer L6sung mittels Ionenaustauscher, Wirtsch.-Pat. DD 294 735 (1991). 4 F. Auerbach, Bors~iure und arsenige S~iure, eine Studie fiber Komplexbildung, Z. Anorg. Chem., 37 (1903) 353-377. 5 B. Englund, Die Acidit~it der arsenigen Sfiure und ihrer Diolverbindungen in w~i6riger L6sung, Rec. TraL,. Chim., 51 (1932) 135-142. 6 E. Darmois, Reactions des molybdates alcalins sur les ethers maliques et tartriques, BulL Soc. Chim. Fr., 43 (1928) 1214-1229. 7 R. Lohmar and R.M. Goepp Jr., The hexitols and some of their derivatives, Adu. Carbohydr. Chem., 4 (1949) 211. 8 E.J. Bourne, D.H. Hutson and H. Weigel, Complexes between molybdate and acyclic polyhydroxycompounds, J. Chem. Soc., (1961) 35-38. 9 H.J.F. Angus and H. Weigel, Complexes between polyhydroxy-compounds and inorganic oxyacids. IV. Dimolybdate and ditungstate ions as complexing agents, J. Chem. Soc., (1964) 3994-4000. 10 J. Bardet and A. Tchakirian, Preparation and properties of some germanous salts, C.R. Acad. Sci., 186 (1928) 637-638. 11 A. Tschakirian, Les acides mannito-germanique, zirconique et ferrique, Bull. Chem. Soc. Fr., l(/ (1943) 98-102. 12 A. Tschakirian, Beitrag zu der Chemie des Germaniums und Versuch einer Einigung der Theorien der organischen und anorganischen Chemie, Ann. Chim. (Paris), 12 (1939) 415-499. 13 P.J. Antikainen, A comparative study of the chelate formation between germanic acid and some glycols and polyalcohols in aqueous solution, Acta Chem. Scand., 13 (1959) 312-322. 14 S. Yasuda and K. Kawazu, Preconcentration of germanium(IV) from natural water by chelating resin with 1-deoxy-l-(methylamino)sorbitol groups, Bunseki Kagaku, 27 (1988) T 67-T 71, Chem. Abstr., 109 (1988) 43237. 15 S. Yasuda and K. Kawazu, Removal of trace germanium from concentrated zinc sulfate solution using N-methyl-glucamine resin, Kyushu Kogyo Gijitsu Shikensho Hokoku, 43 (1989) 2739-2744, Chem. Abstr., 112 (1990) 81476r.

188 16 S. Yasuda and K. Kawazu, Separation of germanium from ethylene glycol distillates by N-methylglucamine resin, Sep. Sci. Technol., 26 (1991) 12731277. 17 F.J. Conrad, R.G. Dosch, R.M. Merrill and D.E. Wanner, The chemical characterization of silicongermanium thermoelectric alloys, Anal, Chim. Acta, 61 (1972) 475-486. 18 Dow Chemical Company, Selektives Adsorbens fiir Metalloxy- und Metalloidoxyanionen, DE-OS 1.495.508 (1964). 19 Dow Chemical Company, Method for removing iron from aqueous concentrated alkali metal hydroxide solutions, US Pat. No 3.197.281 (1965). 20 R.S. Juvet Jr., The N-methylglucamine complexes. I. The lead N-methylglucamine system, J. Am. Chem. Soc., 81 (1959) 1796-1801.

U. Schilde, E. Uhlemann /React. Polym. 20 (1993) 181-188 21 S.C. Furman and C.S. Garner, Absorption spectra of vanadium(III) and vanadium(IV) ions in complexing and noncomplexing media J. Am. Chem. Soc., 72 (1950) 1785-1789. 22 N. Ingri and F. Brito, Equilibrium studies of polyanions. VI. Polyvanadates in alkaline NaCI medium. Acta Chem. Scand., 13 (1959) 1971-1996. 23 J. Magee and E. Richardson, Some studies on vanadic acid, J. Inorg. Nucl. Chem., 15 (1960) 272278. 24 G. Brauer, Handbuch der pr5parativen anorganischen Chemie, Ferdinand Enke Verlag, Stuttgart, 1954, S. 1254-1255. 25 Chemie AG Bitterfeld/Wolfen, DD-WP 279 377 (1990).