A DFT study of the adsorption of O2 and [Fe(H2O)2(OH)3] on the (001) and (112) surfaces of chalcopyrite.

The oxidation of chalcopyrite, CuFeS2, is still not well understood and relevant in the context of the hydrometallurgical extraction of copper. Herein, we used DFT calculations within the periodic boundary conditions formalism to study the adsorption of O2 and [Fe(H2O)2(OH)3] molecules on the (001) and (112) surfaces of CuFeS2. The O2 molecule adsorbs strongly by a dissociative pathway at sulfur atoms on the (001) surface with an adsorption energy of - 76.5 kcal mol-1. The surface is chemically modified forming SO2 groups, in which the S-O bond length is calculated to be 1.47 and 1.54 Å. PDOS and Löwdin charges analyses indicate the oxidation of the sulfur atoms on the surface. We tested different adsorption modes of [Fe(H2O)2(OH)3], and a bidantade coordination with the Oads-Fesur and Feads-Ssur bond lengths of 2.02 and 2.47 Å is the most favorable with an adsorption energy of - 18.8 kcal mol-1 on the (001) surface. Adsorptions of each species are also observed on the (112) surface, but they are weaker than those observed on the (001) surface.