Direct Valorization of Recycled Palladium as Heterogeneous Catalysts for Total Oxidation of Methane

Abstract

Electronic waste as an alternative source of palladium is used for the preparation of heterogeneous catalysts for methane oxidation. The strategy developed in this paper involves two steps: optimization of the leaching protocol to recover the Pd from the waste, and development of a suitable impregnation protocol directly from the leachate, which is a strongly acidic solution. The precipitation-deposition technique is particularly suitable for the preparation of catalysts from acidic media. The impact of Ba, Bi, and Ag impurities on the catalytic performance is studied on model catalysts. The presence of these elements and their impact on the catalytic properties are analyzed and discussed using X-ray diffraction, nitrogen physisorption, scanning and transmission electron microscopy. Through variation of the pH, the impurities co-deposited with Pd can be limited and the catalytic performance of catalysts derived from real waste can be greatly enhanced.