Selective depression of pyrite by glutathione for molybdenite–pyrite flotation separation under neutral pH conditions: Experimental evidence and DFT insights

Glutathione (GSH) was first introduced for efficient pyrite depression under neutral pH conditions. • GSH enabled efficient flotation separation of molybdenite from pyrite, maintaining high selectivity. • GSH interacted with pyrite through dominant Fe–S coordination and markedly enhanced surface hydrophilicity. The selective separation of molybdenite from pyrite remains a longstanding challenge in sulfide flotation, while conventional lime-based alkaline depression is often associated with high reagent consumption, environmental concerns, and reduced molybdenite recovery. In this study, glutathione (GSH) was employed as a selective organic depressant for pyrite in a molybdenite–pyrite flotation system. At pH 7.0 and 40.0 mg/L GSH, micro-flotation tests showed excellent selectivity, reducing pyrite recovery to 2.75% while maintaining molybdenite recovery above 95%. Bench-scale flotation of an actual molybdenum ore confirmed the practical applicability of GSH, producing a Mo concentrate with 49.67% Mo grade and 81.28% recovery. The selective depression mechanism was clarified by integrating adsorption measurements, zeta-potential analysis, wettability measurements, XPS, and DFT calculations. The results revealed stronger interfacial affinity of GSH for pyrite than for molybdenite, enhancing pyrite hydrophilicity. XPS analysis indicated that –SH, –C=O, and –NH 2 groups participated in interactions with surface Fe sites, while DFT identified Fe–S coordination between –SH and surface Fe atoms as the dominant adsorption mode responsible for selective surface regulation and effective pyrite depression. These findings clarify the interfacial mechanism underlying GSH-mediated selective pyrite depression and provide a promising strategy for efficient molybdenite–pyrite flotation separation under neutral conditions. Download: Download high-res image (248KB) Download: Download full-size image