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

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