Extraction and recovery of Au, Sb and Sn from electrorefined solid waste

Abstract

Acid leaching of gold, antimony, and tin from the electrorefined solid waste was investigated. The parameters affecting the leaching process such as, acid concentration, shaking time, temperature, chlorine gas and pulp density were evaluated. Quantitative extraction of Au from the leaching liquor containing Sb and Sn species in HCl (2 M) employing Aliquat-336 in kerosene (10% (v/v)) was achieved. Maximum recovery (99.2±3.4%) of Au from the organic phase was obtained quantitatively using thiourea–hydrochloric acid (2% (w/v), 0.2 M) stripping system. Quinol solution at 6% (w/v) concentration was found able to reduce Au(III) in the striped aqueous solution to Au. Extraction of Sb species from the leachant liquor at HCl (6 M) was quantitatively obtained using Aliquat-336 (10% (v/v)) in kerosene after oxidation with 8% (w/v) sodium periodate. The Sb(V)-Aliquat-336 ion associate in the organic phase was then stripped as Sb(III) by reduction with oxalic acid (1 M), precipitated as Sb 2S 3 by sodium sulfide (2% (w/v)) and finally reduced to Sb with hydrogen. Sn(IV) species in the leachant liquor containing HCl (6 M) was reduced to Sn(II) with zinc granules (6.5% (w/v)) and extracted with Aliquat-336 (10% (v/v)) in kerosene as an ion associate. The produced complex ion associate was then stripped from the organic phase using sodium hydroxide (1 M), precipitated as Sn(II) oxide and finally reduced to Sn with hydrogen.