A novel nanomaterial-oriented and integrated pyrohydrometallurgy of low-grade Nickel–Copper matte.

Combining great targeting and cleaner technology is a potential strategic development in the metallurgy and materials industry. This paper proposed a nanomaterial-oriented and integrated pyrohydrometallurgy of low-grade nickel–copper (Ni–Cu) matte: temperature-programed roasting, followed by water leaching and the direct preparation of Cu@Ni–Co core–shell nanoparticles from its leachate. First, a three-step temperature-programed roasting process was designed, in which the effects of the roasting temperature scheme and NaCl additive on the water leaching rates of valuable metals were systematically investigated. Under optimized conditions, the water leaching rates of Ni, Cu, and Co were 96.8, 98.9, and 99.8%, respectively, while that of Fe was nearly zero. The leachate was a chlorine-free sulfate aqueous solution. The addition of NaCl in this study was 10% (100 mg/g), which was 5–10 times less than that in previous studies. The substantial decrease in the amount of chloride added during roasting greatly reduced the high temperature corrosion of chlorine and pollutant emission. It was confirmed that a small amount of NaCl induced the chlorination–sulfation coupling reactions of low-grade Ni–Cu matte in the appropriate roasting scheme, thereby promoting the selective sulfation of sulfides and obtaining chlorine-free roasting products. In addition, the nanopowder with the Cu@Ni–Co core–shell structure was synthesized by low-temperature hydrazine hydrate reduction from the leachate. Summarily, a novel NaCl roasting water leaching low-temperature reduction successfully realized the integration of a cleaner and efficient extraction of valuable metals and preparation of high-value nanomaterials from the low-grade Ni–Cu matte. This cleaner, material-oriented, and short process design greatly expands the industrial application of traditional mineral resources and their extractive metallurgy. • A three-step temperature-programed roasting process was designed for low-grade Ni–Cu matte. • A small amount of NaCl induced the chlorination–sulfation coupling reactions of Ni–Cu sulfides. • The water leaching rates of Ni, Cu, and Co were 96.8, 98.9, and 99.8%, respectively. • Nanopowder with a Cu@Ni–Co core–shell structure was synthesized from leachate by low-temperature reduction. [ABSTRACT FROM AUTHOR]