An innovative sulfidation roasting method for the efficient flotation recovery of malachite

Malachite, a typical copper oxide ore, exhibits strong hydrophilicity; therefore, it also exhibits poor flotation recovery. In this study, sulfidation roasting was applied as a pretreatment strategy to improve the flotation efficiency of malachite. Pyrite was used as the sulfidation agent during roasting, the feasibility of which was verified using thermodynamic calculations. Microflotation experiments demonstrate that the flotation recovery of malachite increased by nearly 70% compared with that of the untreated sample. X-ray diffraction analysis indicates that the malachite decomposed into CuO during roasting and mainly formed CuS and Cu₂S after sulfidation. This result was further supported by X-ray photoelectron spectroscopic analysis, which revealed the presence of S (S²⁻, \mathrmS_2^2- , and \textS_n^2- ) and Cu (Cu⁺ and Cu²⁺) species in different oxidation states on the surfaces of the roasted sample, as well as a notable decrease in oxygen content. In addition, the formation of copper sulfides disrupted the original porous structure, which led to a decrease in internal pore size. The contact angle increased from 43.71° to 89.29° after sulfidation roasting, indicating that the hydrophobicity of malachite improved markedly. Zeta potential results further indicate that the surface electronegativity increased owing to the adsorption of S species. Overall, sulfidation roasting using pyrite improved the floatability of malachite by generating hydrophobic copper sulfides on the mineral surfaces, thereby demonstrating its potential as an effective pretreatment for copper oxide ores.