Mineral processing: leaching process of chromium and recovery of platinum group elements from Northwestern Saudi Arabian Ophiolitic chromite

Abstract

The current strategy reports the recovery of precious group metals (PGMs) from Na 2 CO 3 roast of Saudi Arabian ophiolitic chromite ore at 1160 °C under atmospheric O 2 . The influence of roasting temperature (960-1200 °C) and leaching agents (H 2 O, HCl, H 2 SO 4 ) and their concentrations on the recovery of PGMs was studied. Chromite roast concentrates a reasonable percentage of approximately 45% with an overall 43% Cr 2 O 3 . PGMs in the original ore was petitioned and ends up in Na 2 CrO 4 liquor whereas the liquor and a solid roast residues contained the rest of chromite components (Fe 2 O 3 , Al 2 O 3 , others). Na 2 CrO 4 in the water or H 2 SO 4 leachate was reduced with SO 2 gas to give crystalline basic chrome sulfate with excellent yield (> 99%) and purity (Fe < 0.1%). PGMs in the Na 2 CrO 4 liquor were extracted into methylisobutylketone (MIBK) after shaking with ammonium pyrrolidine dithiocarbamate (APDC). In MIBK extract, the PGMs species was then stripped by shaking with HgCl 2 -HNO 3 (1.0 mol L −1 ). Ir and Pt in the produced PGEs cake were found up to 4.0 and 0.5 µg/g, respectively whereas the majority of Ni (0.5% as NiO) was retained in the solid roast residues. The proposed method offers a simple approach with good cost-effectiveness for PGEs recovery and production of basic chrome sulfate with Fe content less than 0.1%. Leaching with water offers a simple, an eco-friendly and cost-effectiveness approach for the production of a basic chromium sulfate product with high quality yield of PGEs as a byproduct with minimum Fe content (< 0.1% m/m) required for the tanning industry compared to the method reported.