Selective dissolution of copper from copper-chromium spent catalyst by baking–leaching process

Abstract

The selective leaching of copper from the spent Cu-Cr catalyst was carried out with H2SO4. The effect of different parameters such as acid concentration, pulp density, temperature and particle size on leaching was investigated. The maximum extraction of copper and chromium was 67.25 and 2.3%, respectively at particle size 45–53μm, pulp density 2.5%, temperature 90°C, time 180min. Therefore, baking followed by leaching approach was adopted for dissolution of spent copper-chromium catalyst using H2SO4 to enhance the metal leaching efficiency. At the optimum baking–leaching condition i.e. baking time 2h, baking temperature 300°C, baking acid concentration 0.5M, leaching temperature 35°C, time 60min, [H2SO4] 4%, P.D. 2.5%, the extraction of copper and chromium was 99.9% and 1.2%, respectively, ensuring the selective dissolution of copper. The XRD and Fe-SEM-Edax characterization analysis of typical samples (original, baked mass and typical residue) were compared and reported. The XRD and Fe-SEM-Edax analysis of the baked mass indicated the complete sulfation of copper and chromium by H2SO4 yielding CuSO4 (H2O) and (Cr)2(SO4)3, respectively in solid phase. The absence of XRD peaks corresponding to CuSO4·H2O in the final typical leach residue (obtained at optimum baking–leaching condition) confirmed the complete dissolution of copper from Cu-Cr catalyst.