Lattice defects and surface adsorption properties of gold-bearing chalcopyrite: A theoretical study based on DFT

Chalcopyrite (CuFeS2), as one of the carrier minerals of gold, undergoes significant alterations in lattice and surface properties upon doping with gold impurities. These changes markedly influence its separation and purification techniques, especially flotation. Using Density Functional Theory (DFT) based on first-principles, we analyze the influence of gold impurities on the lattice defects and surface properties of chalcopyrite. We developed an adsorption model using prop-2-yn-1-yl diethylcarbamodithioate (PDEC), a sulfur ester collector with an ethynyl group, on gold-infused chalcopyrite to elucidate the adsorption mechanism. Our findings indicate that the Au atom primarily occupies interstitial sites within the chalcopyrite lattice, resulting in an expanded lattice structure. Despite the doping, the lattice remains a p-type semiconductor with increased conductivity, facilitated by Au 6 s orbitals contributing to impurity levels within the conduction band from 2 to 4 eV. Additionally, there is a marked rise in spin-up electrons, with Integrated |Spin Density| results showing greater electron localization in Cu15Fe16S32Au and Cu16Fe16S32Au compared to ideal chalcopyrite crystal (Cu16Fe16S32). The Au atom exhibits maximum stability when adsorbed onto the S-Fe bonds on chalcopyrite surfaces, primarily forming covalent bonds through electron acceptance from Fe 3d orbitals. The presence of gold impurities decreases the collector's adsorption energy on the chalcopyrite (112) surface. However, PDEC exhibits enhanced adsorption performance relative to Al-DECDT and Z-200, primarily due to the chelation between thiocarbonyl and ethynyl groups of PDEC and the gold-bearing chalcopyrite (112) surface. Electron donation from Fe 4p orbitals of surface to the S 3 s and 3p orbitals of collector forms a sigma bond, while the ethynyl group undergoes hybridization with the Au 5d orbitals from -5 to -2.5 eV, fostering stable electron transfer.