Elimination of the adverse effects of humic substances on molybdenite flotation: Pre-removal of humic substances using polyferric sulfate coagulation

Abstract

Humic substances, which are the predominant components of natural organic matter in water bodies, have been found to be detrimental to molybdenite flotation. In this study, we attempted to eliminate their adverse effects on molybdenite flotation via the pre-removal of humic substances from process water using polyferric sulfate (PFS) coagulation. The flotation tests demonstrated that the humic substances contained in process water can cause a reduction in the flotation recovery of molybdenite over a wide pH range. The results obtained using atomic force microscopy (AFM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) showed that humic substances can be adsorbed onto the molybdenite surface with a high density, which is responsible for the decline in the flotation recovery of molybdenite. The PFS coagulation followed by flotation tests proved that the pre-removal of humic substances using PFS coagulation can eliminate the adverse effects of humic substances on molybdenite flotation. Furthermore, the AFM and ToF-SIMS results showed that the pre-removal of humic substances from process water can reduce the adsorption of humic substances onto the molybdenite surfaces. Interestingly, the improvement in the flotation recovery of molybdenite is roughly related to the removal rate of humic substances. This indicates that achieving a high removal rate of humic substances is critical for improving the flotation recovery of molybdenite. This study provides a feasible method for eliminating the adverse effects of humic substances contained in process water on the flotation recovery of molybdenite.