Study on the mechanism of calcium lignosulfonate in chromium-free flotation separation of chalcopyrite and galena

Chalcopyrite and galena are significant sulfide minerals found in copper-lead (Cu-Pb) ores, drawing attention to environmentally friendly separation techniques in mineral processing . This research explored the use of calcium lignosulfonate (CLS) as a depressant to achieve efficient separation of chalcopyrite from galena under weakly alkaline conditions (pH=8–10). The adsorption behavior of CLS was analyzed using Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV–vis), zeta potential measurements, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The findings revealed that CLS selectively adsorbed onto the galena surface, inhibiting the interaction between xanthate and galena. Furthermore, the results of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations indicated that CLS chemisorbed onto the galena surface through bonding between oxygen atoms in the sulfonic acid group and lead atoms, and the process occurred spontaneously. This selective adsorption significantly increased the hydrophobicity of the galena surface, enabling chromium-free separation of chalcopyrite and galena.