Electrochemical investigation of the interactions of organic and inorganic depressants on basal and edge planes of molybdenite.

Molybdenite (MoS2) has attracted great attention in the field of advanced materials. MoS2 is normally separated from other minerals by selective flotation, and chemical reagents (so-called depressants) are required to lower the surface hydrophobicity of MoS2. Previous studies had controversial arguments on the adsorption of organic and inorganic depressants, i.e., carboxymethyl cellulose (CMC), Ca2+ and Mg2+ on the anisotropic MoS2 surfaces. Therefore, in this work, the interactions of these depressants on MoS2 basal and edge surfaces in alkaline solutions were investigated using electrochemical techniques. The MoS2 edge surface had higher electrochemical reactivity than the basal surface, and the electrochemical reactivity of both the surfaces reduced after treatment in CMC, Ca2+ and Mg2+ solutions, which suggested that the depressants adsorbed on both basal and edge surfaces. The cyclic voltammetry and scanning electrochemical microscopy results indicated that the coverage of adsorbed inorganic species, i.e., Ca(OH)2, CaCO3 and Mg(OH)2 particles, on MoS2 basal and edge surfaces was lower than that of CMC. The randomly distributed hydrophilic Ca(OH)2, CaCO3 and Mg(OH)2 particles on MoS2 basal surface reduced the possibility of bubble attachment, which was the main reason for the depressed MoS2 floatability reported in the literature.