Selective depression mechanism of konjac glucomannan on sphalerite: Interfacial insights from hydrophilicity and hard-soft acid-base theory

Abstract

This study pioneers the development of bio-based polysaccharide konjac glucomannan (KG), as an environmentally friendly depressant to replace conventional reagents in chalcopyrite and sphalerite flotation separation, addressing critical environmental challenges in sulfide mineral processing. An integrated approach combining micro-flotation tests, interfacial characterization (contact angle and AFM tests) and multi-scale spectroscopic measurements (FT-IR、XPS analysis and DFT calculations) was used to reveal the selective depression mechanism of KG. Micro-flotation performance metrics demonstrated that 10 mg/L KG dosage induced a remarkable floatability divergence, sustaining 89.7 % chalcopyrite recovery while depressing sphalerite to 22.5 %. Rheological tests reveal that the viscosity of sphalerite pulp decreased with increasing shear rate, and the shear force exhibited a nonlinear relationship with shear rate in the presence of KG. Conversely, chalcopyrite pulp maintains near constant viscosity and shear force across varying shear rate. Contact angle tests and AFM analyses revealed that KG addition increased the surface roughness of sphalerite, notably reduced the contact angle, and hindered the subsequent adsorption of Sodium butyl xanthate (NaBX). FT-IR and XPS analyses showed that KG exhibited stronger adsorption on sphalerite than on chalcopyrite, achieving selective depression through the synergistic effect of surface coordination bonds and hydrogen bonds, thereby enabling effective separation of chalcopyrite and sphalerite. Additionally, DFT calculations quantified the difference in adsorption energies of KG on chalcopyrite and sphalerite surfaces. In conclusion, this study confirms that KG is a highly selective green depressant. More importantly, it reveals a novel pathway by KG molecules synergistically modulate the mineral interfaces through hydrophilicity and HSAB theory, thus elucidating the critical role of rheological behavior in the depression process. This work provides a theoretical foundation for developing polysaccharide based flotation reagents and promotes the environmentally friendly upgrading of high efficiency separation technology for copper and zinc resources.