Unveiling the adsorption mechanism of xanthate on the pentlandite/pyrrhotite heterostructure from first principles calculations

[Display omitted] •Surface activity and galvanic interactions control the selective adsorption of xanthate and dixanthogen on Pn/Po.•Xanthate shows stronger activity than dixanthogen to interact with sulfides.•Xanthate and dixanthogen adsorption on the Pn surface are prior to pyrrhotite.•The mixed or contacted system of Pn and Po plays as a diode. Pentlandite is the main resource to extract nickel which is a key ingredient for batteries, catalysts, and alloys. Flotation is applied to purify pentlandite from its gangue minerals (i.e., pyrrhotite). However, the adsorption mechanism of flotation collectors with the mixed system is unclear. Herein, first-principles calculations were used to reveal the interfacial bonding mechanisms of xanthate and dixanthogen with pentlandite, pyrrhotite, and their heterostructure. The obtained adsorption configurations and adsorption energy showed that xanthate could interact more strongly with the pentlandite surface due to the strong binding interactions. The adsorption energy and electron localization function showed that the adsorption of collectors on the pentlandite surface had higher priority than pyrrhotite due to the high activity of pentlandite and the existence of galvanic interactions. As verified by the work function results, the heterostructure of pentlandite and pyrrhotite could be seen as a diode where pentlandite played as cathodes permitting the passing of electrons to anode pyrrhotite. This diode model made the selective adsorption of dixanthogen on pentlandite surfaces. This work gives novel research ideas to consider galvanic interactions between the mixed sulfides system. The obtained findings may benefit the development of new purification techniques for pentlandite.