부산대학교 도서관

• Subsequent MW sulfation roasting and MW leaching recovers PGMs from spent catalysts. • Roasting and leaching parameters were optimized for optimal Pd, Pt and Rh leaching. • A low amount of oxidation agent during roasting is required and only 1 M HCl for leaching. • The occurring reactions during MW sulfation roasting are studied in detail. A microwave assisted two-step platinum group metal (PGM) extraction process for spent automotive ceramic catalysts was developed. The first step consists of a microwave (MW) sulfation roasting process of spent catalyst in the presence of NaHSO 4 ·H 2 O or KHSO 4 and NaClO 3 , for which the roasting parameters (i.e. MW power, roasting time, ClO 3 −:HSO 4 − molar ratio, salt:catalyst weight ratio) were studied and optimized. During roasting a solid salt mixture and spent catalyst (weight ratio salt:spent catalyst = 5, molar ratio NaClO 3 :NaHSO 4 ·H 2 O = 0.05) was volumetric heated (750 W, 30 min) through absorption of MWs without the use of any other heat source. Whereas for the subsequent step, a short (30 min, 105 °C) MW acidic leaching process in 1 M HCl solution at a liquid to salt ratio of 10 was evaluated to give the best PGM leachabilities (i.e. Pd 96 ± 1%, Pt 85 ± 5% and Rh > 96%). An in depth experimental study of the roasting process showed that sulfation roasting attacks both the cordierite (Mg 2 Al 4 Si 5 O 18) honeycomb material and rare earth oxides of the wash coat, to form sulfate salts. During roasting metallic Pd oxidized. Mass loss during roasting was ascribed to evaporation of NaHSO 4 ·H 2 O hydration water and subsequent decomposition of NaHSO 4. [ABSTRACT FROM AUTHOR]