Distribution Coefficients and Cation Exchange Behavior of Elements in Hydrochloric A,cid-Acetone F. W. E. Strelow, A. H. Victor, C. R. van Z y l , and Cynthia Eloff National Chemical Research Laboratory, Pretoria, South Africa Cation exchange distribution coefficients with Bio-Rad AG 50W-X8, a sulfonated polystyrene cross-linked with divinyl benzene are presented for 54 cations in hydrochloric acid-acetone media, covering the acid concentration range 0.1 to 3.OM and the acetone concentration range 0 to 95%. The elements are arbitrarily arranged in tables according to their coefficients in aqueous hydrochloric acid. A number of the possibilities of this system for separations are pointed out and some aspects of the elution behavior of various elements are discussed. The versatility of hydrochloric acidacetone mixtures as eluting agent for cation exchange separations is demonstrated by sequential elution of the mixtures TI(III), In, Ga, AI, Yb; Cd, Zn, Fe(lll), Cu(ll), Co(ll), Mn(ll); and V(V), Fe(lll), U(VI), Ti(IV), Ca, Ba. THEFIRST ATTEMPT to improve the cation exchange separation of transition metals by addition of a water mixable organic solvent with the aim to promote chloride complex formation in the external phase selectively is probably due to Kember et al. ( I ) . A systematic survey of cation-exchange distribution coefficients for 14 elements in HC1-acetone media has been presented by Fritz et al. (2). More recently Korkisch et al. (3) have determined distribution coefficients for 20 elements in mixtures of aqueous HC1 with 8 different organic solvents. In these two systematic investigations, the concentration of hydrochloric acid has been limited to upper values of 1.O and 1.2M, respectively. As a result, several useful separations of elements with slight or negligible tendency to chloride complex formation did escape attention, because these separations are obtained at higher acid concentrations (4-6). A more complete survey covering the distribution coefficients and elution behavior of 45 elements in hydrochloric acid ranging from 0.1 to 3.OM and ethanol concentrations between 0 and 95 % has been presented by the author and his coworkers recently (7). Acetone promotes chloride complex formation considerably more strongly than ethanol, and therefore provides conditions favorable for separations at considerably lower solvent or hydrochloric acid concentrations. Furthermore, cation exchange separations of elements such as Co(II), Mn(II), and Ni(I1) which are not possible or are difficult in HC1-ethanol mixtures become very easy. This paper therefore presents distribution coefficients for 54 cations in hydrochloric acid and acetone concentrations ranging from 0.1 to 3.OM and 0 to 95%, respectively, and discusses the elution behavior and favorable conditions for some separations selected out of the wealth of possible ones. (1) N. F. Kernber, P. J. MacDonald, and R. A. Wells, J . Chem. SOC.,1955, 2273. (2) J. S. Fritz and T. A. Rettie. ANAL.CHEM.,34. 1562 (1962). (3) J. Korkisch and S. S. Ahlubalia, Talanta, 14,155 (1967). (4) F. W. E. Strelow and C. R. van Zyl, Anaf. Cliim. Acta, 41, 529 (1968). (5) F. W. E. Strelow, ANAL.CHEM., 40,929 (1968). (6) F. W. E. Strelow and Cynthia Baxter, Talanru, 16, 1145 (1969). (7) F. W. E. Strelow, C . R. van Zyl, and C. J. C . Bothma, Anal. Chim. Acta, 45, 81 (1969).
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ANALYTICAL CHEMISTRY, VOL. 43, NO. 7, JUNE 1971
While this work was in progress, a study of distribution coefficients of 27 elements in HC1-acetone solutions has been published by Peterson et al. (a), but coefficients were determined only at a single concentration of HCl [0.3M] for all elements except cobalt, for which the range 0.1 to 0.5M HC1 was covered. Since they were determined at a different acid concentration, Peterson's coefficients cannot be compared to ours directly, except those for Co(I1) which show quite reasonable agreement. Good agreement is obtained for most other elements by plotting our results and reading results at the concentrations used by Peterson from the curves. EXPERIMENTAL Reagents and Apparatus. The resin used was the AG 50W-X8 sulfonated polystyrene cation exchanger supplied by Bio-Rad Laboratories, Richmond, Calif. Resin of 100 to 200 mesh particle size was used for batch equilibrations and of 200 to 400 mesh for column work. Borosilicate glass tubes of 20 mm i.d., with fused-in glass sinters of No. 2 porosity and a buret tap at the bottom and a B19 ground-glass joint at the top were used as columns. Analytical-reagent grade chemicals were used whenever possible. Chlorides of the platinum metals, and of gold, germanium, gallium, indium, ytterbium, scandium, and niobium were obtained from Fluka A.G., Buchs, Switzerland. Standard solutions were prepared in 0.1, 1.0, and 10M HCl. Those of V(V), Mo(VI), W(VI), As(III), As(V), Sb(III), Se(IV), and Te(1V) were prepared by passing aqueous or 1M hydrochloric acid [in the case of Sb(III), Se(IV), and Te(1V)I solutions of the ammonium or sodium salts through a cation exchange column, and adding the required amount of standard hydrochloric acid to the eluate. The solutions of V(V), Mo(VI), W(VI), and Nb(V) also contained 1 hydrogen peroxide. Spectrophotometric and atomic absorption measurements were carried out with a Zeiss PMQ I1 and a Perkin-Elmer 303 instrument, respectively. Distribution Coefficients. The coefficients were determined by equilibrating 250 ml of a solution containing 5 meq amounts of the elements with 2.500 grams of AG 50W-X8 resin in the hydrogen form, which had been dried at 60 OC in a vacuum pistol with phosphorus pentoxide as drying agent. In the cases of W(VI), Mo(VI), Nb(V), and V(V), the equilibrium mixtures also contained 2.5 ml of 30% hydrogen peroxide. As given, 1M HCI containing 80% acetone means 25 ml of 10M HCl mixed with 25 ml of distilled water and 200 ml of acetone. Volume changes on mixing were disregarded. After equilibration for 24 hours in a mechanical shaker at 25 "C,the resin was separated from the aqueous phase by filtration, and the amounts of the elements in both phases were determined by appropriate analytical methods. From the results, weight equilibrium distribution coefficients
D =
amount of element in resin amount of element in solution
ml of solution grams dry resin
were calculated. ~
(8) S. F. Peterson, F. Tera, and G. H. Morrison, J . Radioatzal. Chem., 2, 115 (1969).
Table I. Distribution Coefficients in 0.10M HCl with Various Amounts of Acetone Element 0% 20% 40% 60% 80% 90% 95% Element 0% 20% 40% 60% 80% 90% 95% Ga >io4 > i o 4 >io4 >io4 1610 6.6 5.0 27.2 30.8 prec. prec. prec. prec. prec. Fe(1II) > l o 4 >lo4 >IO4 >IO4 28.6 2.4 0.5 V(V).lc 15.0 5.4 5.3 5 . 3 11.7 11.2 10.1 Ca 1940 2890 5020 >io4 > i o 4 > i o 4 >io4 Rh(II1) 4.2 4.9 4.8 5.1 5.4 5.0 4.7 Mn(I1) 1090 1670 3190 5700 6070 1490 67 w(vI)a 1.7 1.6 1.8 1.9 1.7 1.6 1.3 Co(I1) 1080 1500 2800 6500 > l o 4 720 15 Pd(I1) 1.6 2.0 1.8 1.9 1.7 1.6 1.5 Zn 1010 939 848 380 7.6 2.4 1.2 Hg(I1) 1.6 1.7 1.4 1.2 1.1 0.9 0.9 Cu(I1) 990 1510 2450 3210 578 16.7 0.9 Pt(1V) 1.4 1.6 1.4 1.7 1.6 1.4 1.3 985 40.2 2.4 As(V) 1.4 2.3 3.0 4.0 5.4 7.2 9.1 Fe(I1) 904 1440 3740 -lo4 826 1100 2180 4450 5900 5900 5900 As(II1) 1.4 1.4 1.5 1.4 1.7 1.4 1.6 Mg In(II1) 815 795 452 106 2.6 0 . 5 io4 >io4 >io4 >io4 >io4 >io4 Sn(1V) 99 6070 10.9 0.8 22.9 5.3 4.2 Ga 3040 > l o 4 >lo4 > l o 4 98 131 183 308 3.0 1 . 5 0.9 cs Fe(II1) 2700 3300 4650 2130 84 75 56 7.1 Cd 810 1037 1838 4210 > l o 4 > l o 4 > I O 4 Sr Rb 71 95 162 334 Ca 852 1340 2880 7300 > l o 4 > l o 4 631 64 85 287 10.9 K 154 349 474 875 1550 1510 Mn(I1) 342 10.6 9.7 100 2.3 V(V)Q.C 8.5 5.5 860 1480 1830 Co(I1) 340 456 29.9 42.2 76 160 Na 423 798 1720 1780 1430 1260 Ni(I1) 340 17.1 24.5 38.0 68 49.8 2.7 2.1 1.4 Li Zn 336 396 384 320 3.2 1.2 Te(IV) 17.0 28.1 54.2 51.2 467 788 1840 Fe(I1) 328 Nb(V)a 10.8 12.6 prec. prec. 406 638 708 103 3.9 0.9 Cu(I1) 317 V(V)..b 61 69 94 135 620 1190 1430 1600 1600 356 Mg 281 1.8 2.0 1.9 1.7 346 571 796 372 7.8 3.4 W(VIp U(VI) 252 742 750 420 219 Bi(II1) prec. prec. prec. 354 498 1 .O Cr(II1) 242 756 770 248 58 Mo(VI)= 0.8 0.9 1.3 1.1 244 398 197 V(W prec. prec. prec. prec. Tl(II1) 0.2 0.2 0.2 0.2 164 238 129 TKI) Be 117 307 621 1740 1860 1630 Au(II1) 0.2 0.2 0.2 0.2 For footnotes, see Table I. .
I
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Table 111. Distribution Coefficients in 0.50MHCI with Various Amounts of Acetone 20% 40% 60% 80% 90% 95% Element 0% 2 0 z 40% 60% >io4 >io4 >io4 Be 42.1 56 86 132 1880 2810 6100 -104 431 674 1411 3950 prec. prec. prec. Ti(1V) 39.1 108 206 538 AI 278 464 751 1120 1180 1250 1310 TU) 37.7 51 43.9 prec. Ga 245 1110 1770 168 7.2 1.9 1.1 Rb 32.2 44.0 76 153 Fe(1II) 205 215 240 43.2 1.6 1.3 1.0 K 29.5 41.1 73 176 Sr 188 248 498 1050 2720 6180 , .. V( V)a ' b 25.1 28.3 37.3 62 Ca 131 178 283 632 1310 2140 , . . Na 13.9 20.1 33.2 76 Cr(II1) 102 128 186 260 214 150 , . . Li 7.6 10.7 16.4 30.4 Mn(l1) 74 92 151 243 233 14.3 2.8 In(II1) 7.6 4.7 2.7 1.4 Co(I1) 72 89 145 256 127 4.0 1.2 Cd 6.5 4.6 1.4 0.6 Fe(I1) 71 88 149 243 12.4 1.9 1.2 Sn(IV) 6.3 3.6 2.0 1.3 Ni(I1) 70 85 149 257 304 249 ,.. Te(1V) 4.7 13.3 10.4 6.7 Mg 67 71 112 173 381 399 432 Nb(V)a 3.8 5.4 prec. prec. Cu(I1) 64 77 104 92 6.0 0.8 0.6 V(V)53c 3.8 3.4 2.6 3.8 Zn 64 75 29.9 3.7 1.5 1.3 1.1 Bi(III), Pb(II)d 62 71 27.4 14.1 7.6 4.7 2.9 Au(III), 1 UVI) 58 77 117 138 15.1 1.4 0.9 } 104 A1 4.7 5.6 8.8 Th 97 150 393 850 4.7 A1 4.7 5.6 8.8 Zr 85 145 239 1230 ,.. Mg 3.6 4.1 5.0 24.0 47.1 Hfe 73 349 > 103 Be 3.0 3.3 4.6 23.8 34.7 La 65 288 -103 Na 2.8 4.2 7.4 20.0 30.5 Ce(II1) 130 prec. prec. Fe(I1) 2.8 2.9 3.9 Ba 18.5 40.0 51 111 ... CO(I1) 2.7 3.1 4.3 12.4 24.5 sc/ 35.2 117 ... Mn(I1) 2.6 3.0 4.1 Y 11.9 15.7 27.8 98 ... Ni(I1) 2.4 3.5 4.9 11.5 13.6 Yb ... Li 2.2 2.7 3.3 30.3 151 10.0 13.0 Sr 18.4 78 ... Cu(I1) 1.6 1.4 1.2 7.4 8.8 Ca 10.4 19.1 ... Cr(111) 0.7 1.7 4.0 cs 6.0 7.1 24.6 .,. Au(II1) 0.6 0.5
