| 摘要 |
<p>Zinc is separated from cadmium in aqueous chloride solution by subjecting the aqueous solution to a liquid/liquid extraction with an alkyl ester of phosphoric acid of general formula (CnH2n + 1)H(3- x)PO4 where n/sF3 and x=1, 2 or 3. The ester, preferably tertiary butyl phosphate, may be used undiluted or alternatively as a solution in an inert solvent, e.g. xylene, kerosene or water-insoluble higher ketones. The zinc may be recovered from the organic phase by contacting it with water, dil. H2SO4, HNO3 or dilute aqueous solutions of salts other than chlorides and the recovered liquor recycled. The cadmium may be recovered from the aqueous phase by precipitation as sulphide or hydroxide or alternatively the aqueous liquor may be acidified to a pH <1 and the cadmium extracted with further solvent. The process may be carried out by counterflowing the aqueous and organic phases in a number of mixing and settling stages. Residual cadmium in the organic phase may be removed by contacting it with sodium chloride solution. The aqueous chloride solution containing Cd and Zn should have a pH of 1.5 to 6 and be at a temperature below 30 DEG C. The aqueous chloride solution may be obtained from the regeneration, with NaCl solution, of a cation exchange resin containing adsorbed Zn and Cd ions.</p> |
