Comparison of liquid–liquid extraction studies on platinum(IV) from acidic solutions using bis(2,4,4-trimethylpentyl) monothiophosphinic acid

Abstract

Liquid–liquid extraction (LLE) of platinum(IV) from acidic solutions such as chloride, sulphate and nitrate has been investigated using bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302) in kerosene. Increase in acid concentration increases the percentage extraction of metal up to 3 mol L −1 for chloride and sulphate solutions whereas up to 1.0 mol L −1 for nitrate solutions thereafter it decreases. The extraction of platinum(IV) content increases with increase in the extractant concentration in the ascending order of sulphate > chloride > nitrate. Detailed comparative studies were conducted by varying the diluents, alkaline metal salts, temperature, loading capacity of the extractant, recycling of extractant and stripping of metal with three mineral acids and thiourea. The present investigations focused on the mixture of extractants such as Cyanex 302 with organophosphorous extractants such as Cyanex 272, PC 88A, D2EHPA and TBP. The extraction behavior of other associated elements like iron, copper, silver, palladium, aluminum, magnesium and calcium was also studied.