Recovery palladium, gold and platinum from hydrochloric acid solution using 2-hydroxy-4-sec-octanoyl diphenyl-ketoxime

Abstract

The selective extraction of Pd(II) over Au(III) and Pt(IV) as well as subsequently selective extraction of Au(III) over Pt(IV) from hydrochloric acid (HCl) solution were achieved by using 2-hydroxy-4-sec-octanoyl diphenyl-ketoxime diluted in kerosene as extractant. The typical composition of solution used for the present study contains Pd: 5.95 g/L, Au: 5.42 g/L and Pt: 10.23 g/L. Pd(II) is extracted into organic phase quantitatively after three-stage counter-current extraction operation with extraction percentage >99.9% at pH 2. At a higher HCl concentration (5 M), Au(III) is effectively extracted into organic phase from the resulting raffinate by four-stage counter-current extraction operation. On the other hand, stripping of Pd(II) from loaded organic phase needs high acid solution while the stripping of Au(III) can be achieved at pH 2. Four-stage stripping with 6 M HCl at O:A = 2:1 yielded >99.9% Pd(II) stripping efficiency and four stages stripping with 0.01 M HCl at O:A phase ratio of 2:1 performed >99.9% Au(III) stripping efficiency. The resulting solutions for each metal, after the corresponding process such as precipitation or reduction, can be used for yielding metal powder with the purity better than 99.99%. A complete process flow sheet for the separation and recovery of Pd(II), Au(III) and Pt(IV) is established based on the present investigation.