Experimentation, Modeling, and Optimum Conditions of Pyro-Hydrometallurgical-Precipitation Reaction Technology for Recovery of Copper as Oxide of Nanoparticles from a Copper Dust

Abstract

Conventionally, the leach-solvent extraction-electrowinning technology has been preferred for copper recovery from its primary and secondary sources as cathode slabs even though its recovery as copper oxide nano-particles (CuO NPs) is more preferred. Hence, this paper is aimed at presenting the production of CuO NPs from purified pregnant leach solution (PPLS) of a copper smelter dust (CSD); a by-product of primary copper ore smelting. This aim was achieved in four steps of roasting pretreatment, dissolution, precipitation reaction, and thermal decomposition. The CSD was first roasted in a muffle furnace; after which, its copper value was taken into solution via sulphuric agitation leaching using a magnetic stirrer with heater. The reduction of iron in the resultant pregnant leach solution is followed; it was achieved by optimizing the compositional proportion of H₂SO₄:FeSO₄·7H₂O. Copper precursor was then produced from the PPLS via dropwise addition of Na₂CO₃. The precipitate from reaction between chemical species in the PPLS and Na₂CO₃ served as copper precursor; this copper precursor was thermally decomposed to produce the CuO NPs. The optimum conditions for this process route are as follows: 2 h, 2 M, and 90 °C (agitation leaching); 800 °C for 2 h (oxidative roasting); 25 °C and 740 rpm (precipitation of copper precursor); 750 °C for 2 h (precipitation of copper nanoparticles). A grade of 51.30% CuO NPs was achieved from an initial 18.02% Cu content. The average crystallite size was estimated at 35 nm. The predicted outputs proportions obtained using the models were in good conformance with the experimental outputs with error margins between 0.00 and 0.07%.