RECOVERY OF PALLADIUM FROM SPENT Pd/Al_2O_3 CATALYST BY HYDROCHLORIC ACID LEACHING

摘要

Spent Pd/Al_2O_3 catalyst is an important secondary resource of palladium metals. The highly efficient recovery of palladium was hard to implement due to the wrapping of catalyst carriers, accumulating carbon on surface and existing as stable palladium oxide. An effective process for recovery of palladium was investigated. Samples were initially roasted to eliminate carbon. Then, the roasted mass was reduced with reductive agent for the purpose of transferring palladium oxide to palladium. The reduced residue was further leached using hydrochloric acid with -uitable oxidizing agent to recover palladium. The results showed that the palladium extraction only reached tol6.24% by direct leaching process and 43.51% by roasting-leaching process. However, it achieved 98.71% by roasting-reduction-leaching process under the appropriate teaching conditions of HCl 5M, NaClO_3 2.5g/L at 95° C for 2h.Additionally, the feasible conditions involved in roasting and reduction steps were also investigated.