Concentrating Pt from a spent alumina carrier catalyst by a roast-leach process

A roast-leach process has been developed for concentrating platinum (Pt) from a spent Pt-Al 2 O 3 catalyst. The effects of (NH 4 ) 2 SO 4 to spent catalyst mass ratio, roasting temperature and roasting time on the Pt enrichment factors were investigated. The results showed that the optimized roasting conditions were (NH 4 ) 2 SO 4 to spent catalyst mass ratio of 7.5, roasting temperature of 350 °C and roasting time of 5 h. The roasted product was mainly comprised of soluble NH 4 Al(SO 4 ) 2 and Al 2 (SO 4 ) 3 according to XRD analysis. The roasted product was leached in sulfuric acid to remove the soluble sulfates, and meanwhile Pt was kept in the residue. Under optimized conditions, a Pt concentrate with Pt content of 73.2% could be obtained from the spent catalyst with 0.27% Pt, and the corresponding Pt enrichment factor was more than 270.