Study on selective depression of pullulan on specularite/chlorite flotation

The inherent similarities in the physicochemical properties and floatability of specularite and chlorite pose challenges in their effective flotation separation. Exploration and utilization of efficient depressants is vital to improve the flotation separation performance. In this study, pullulan gum (PG) was employed as a depressant in the flotation separation of specularite and chlorite, employing dodecylamine (DDA) as a collector. PG’s inhibitory impact on the flotation performances of these minerals was evaluated through extensive flotation tests and systematically explored its inhibiting mechanism via various surface analytical measurements. Flotation experiments revealed that PG significantly depressed the floatability of specularite while exerting minimal effect on chlorite. Zeta potential tests and surface wettability analyses illustrated strong adherence of PG to specularite, hindering subsequent DDA adsorption, while its impact on DDA adsorption onto chlorite was negligible. Additionally, adsorption capacity measurements confirmed markedly higher PG adsorption onto specularite than chlorite. Further analyses via Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations indicated weak adsorption of PG on chlorite, contrasting with strong chemical adhesion observed between PG and specularite. This disparity resulted in distinct flotation behaviors of these minerals. Consequently, selective depression of specularite flotation and effective flotation separation from chlorite were achieved. Thus, PG emerges as an efficient and eco-friendly depressant, showcasing promise in enabling the flotation-based separation of specularite and chlorite.