Anal. Chem. 1984, 56,2069-2073 (3) Bohn, H. L.; McNeal, E. L., O'Connor, 0. A. "Soil Chemistry"; John Wiley and Sons: New York, Chichester, Brisbane, Toronto, 1979. (4) Dubach, P.; Metha, N. C.; Jakab, T.; Martin, F.; Roulet, N. Geochim. Cosmochim. Acta 1984, 28, 1567-1578. (5) Buffle, J.; Deladoey, P.; Haerdi, W. Anal. Chim. Acta 1978, 701, 339-357. (6) Chian, E. S. K.; DeWalle, F. E. Environ. Sci. Technoi. 1977, 7 1 , 158- 163. (7) Miles, C. J.; Brezonik, P. L. J. Chromatogr. 1983, 259, 499-503. (8) Mantoura, R. F. C.; Riley, J. P. Anal. Chim. Acta 1975, 7 6 , 97-106. (9) Wolf, F.; Laqua, E. \/om Wasser 1977, 4 8 , 273-281.
2089
(IO) Miles, C. J.; Tuschall, J. R.; Brezonik, P. L. Anal. Chem. 1983, 55, 410-41 1. (11) Helfferich, F. "Ion Exchange"; McGraw-HIII: New York, 1962; Chapter 5. (12) Berge, D. G.; Going, J. E. Anal. Chim. Acta 1981, 723, 19-24. (13) Shaw, D. J. "Introduction to Colloid and Surface Chemistry", 3rd ed.; Butterwofths: London, 1980; Chapter 7. (14) Stevens, T. S. I n d . Res. Dev. 1983, 25(9), 96.
RECEIVED for review January 26,1984. Accepted May 14,1984.
Separation of Tellurium from Gold(1I I), Indium, Cadmium, and Other Elements by Cation Exchange Chromatography in Hydrochloric Acid-Acetone F. W.E. Strelow National Chemical Research Laboratory, CSIR, P.O. Box 395, Pretoria 0001, Republic of South Africa
Trace amounts and up to 120 mg of tellurium can be separated from 1.3 g amounts of gold and 0.6 g amounts of Indium and cadmlum by absorptlon from 0.2 M HCI containing 60 % acetone and elutlng these elements with the same reagent from a column of AG 50W-X8 cation exchange resin of 200-400 mesh partlcie slze. The retalned teilurlum Is effectively eluted wlth 1 M aqueous HCI. Separatlons are sharp and quantltatlve. Only between 1.3 and 3.0 pg of gold was found in the tellurlum fraction when 1.3 g was present origlnally. Bl( 111), Sn( IV), Se( IV), As( I I I ) , Pt( IV), Pd( I I), and Rh( I I I ) are also separated together wlth gold, though some of these elements show extended low level talllng of concentratlons of about 1 ppm or less. Relevant elutlon curves and results for the analysls of synthetic mixtures are presented.
The separation of tellurium from other elements by ion exchange chromatography has received relatively little attention so far. It has been shown by Aoki that water will elute selenium from a strongly acid cation exchanger after adsorption from less than 0.05 M acid solution. Most of the tellurium then can be eluted with aqueous 0.3 M HC1 ( I ) . The tellurium is retained not very strongly and only microgram amounts can be separated because of the very limited solubility of tellurium(1V) oxide in very dilute hydrochloric acid or water. Other methods include anion exchange in oxalate media for separation from antimony and tin (2), anion exchange in acetate for separation from selenium (3), cation exchange in 0.1 M HC1 for separation from platinum metals ( 4 ) ,elution with NHIOH from a cation exchange column for separation from copper, nickel, iron, and lead ( 4 ) , cation exchange in 12 M HBr for separation from selenium ( 5 ) ,and anion exchange in LiCl for separation from lead and gold (6). Probably the most generally useful of the methods described is anion exchange in aqueous HC1 (7,8). Selenium can be eluted with 3 M HC1 followed by tellurium with between 0.2 and 0.5 M HC1. Many other elements should be eluted together with selenium, some should accompany tellurium partially, while others should still be retained according to available information on distribution coefficients.
No method seems to have been described for the separation of traces as well as larger amounts of tellurium from large amounts of gold(II1) and many other elements forming stable chloride complexes such as indium, bismuth(III), cadmium, and the platinum metals. In the anion exchange method in HC1 (7,8) mentioned above gold(II1) would still be retained when tellurium(1V) is eluted with 0.2 M aqueous HC1. Yet gold(II1) absorbed as chloride complex on a strongly basic resin is notorious for the difficulties encountered when its quantitative recovery is attempted using an elution procedure. Furthermore, it would be much more attractive to retain tellurium and elute gold when traces of tellurium have to be separated from large amounts of gold. One possibility would be to elute gold(II1) from a cation exchange resin with very dilute aqueous hydrochloric acid, about 0.1 M or less. Unfortunately the solubility of tellurium(1V) is rather limited in this medium and the distribution coefficient in 0.1 M HC1 also is not very large with a value of about 39 (9). In addition a small but significant part of the gold(II1) is retained by the resin (9-11). Beamish and co-workers found losses of a few tenths of a percent even under the most favorable conditions (11). Though it is believed that a reduction of gold(II1) is involved, the actual mechanism of the adsorption is unknown. I t has been shown that the amount of gold retained by the resin becomes negligible when 90 or 60% acetone is present in the eluting agent (9,12). A procedure has been described for the separation of gold(II1) from cadmium, indium, and other elements which are retained by the column (12). In order to elute cadmium and indium together with gold(III), the acetone concentration or the concentration of HC1 or both will have to be increased. In addition tellurium still must be retained relatively strongly. Available data on distribution coefficients (9) show that coefficients for teUurium(1V) increase significantly with acetone concentration at low concentration of HC1, reach a maximum, and then decrease again. The most favorable conditions for separating tellurium(1V) from gold(1111,indium, cadmium, bismuth, tin(IV), the platinum metals, selenium(IV), and some other elements seem to be a t about 0.2 M HC1 containing 60% acetone. The distribution coefficient of tellurium(1V) is about 51 under these conditions as compared with a coefficient of 17 in aqueous 0.2 M HCl. The possibility for using this eluting agent to separate tellurium
0003-2700/84/0356-2069$0 1.50/0 -. . . 0 1984 American Chemical Society
2070
ANALYTICAL CHEMISTRY, VOL. 56, NO. 12, OCTOBER 1984
Table I. Cation Exchange Distribution Coefficients for Some Elements in 0.20 M HC1 and 60% Acetone element Li Te(1V) Zn In Cd Rh(II1)" Ir (III/ IV)" Pd(I1)
coefficient 90
63 62 13.3
7.5 5.1 3.2 1.6
element
IO
coefficient
Pt(1V) Bi(II1) Sn(1V) Hg(I1) Se(1V) As(II1) Tl(II1) Au(II1)
1.1 1.0 0.8
* t Au (rn)
Te(M
2 mmol
f
I mmol
l i
6
0.5
