A DFT-D+U study on comparative adsorption of s-triazine with xanthate and dithiocarbamate collectors on dry and hydrated cooperite (1 0 1) surface

Abstract

The high demand of platinum has drawn much attention on the recovery of the platinum group minerals (PGMs). Cooperite (PtS) is one of the major sources of platinum which is found in high concentration as sulphide minerals in the Platreef. This current study used the density functional theory with dispersion correction method and applying the U-parameters (DFT-D + U) to understand the interaction of the well-known collectors, sodium normal butyl xanthate (SNBX) and sodium normal butyl dithiocarbamate (SNBDTC) which are utilised in industry in comparison with the green novel sodium 2,6-dithio-4-butylamino-1,3,5-triazine (SDTBAT) collectors on dry and hydrated cooperite (101) surface. In the adsorptions, different adsorption sites were initially tested on dry surface, to identify the most preferred active and exothermic site of the colletors on the surface. The SNBX and SNBDTC collectors preferred to form a binuclear-bidentate, while the SDTBAT formed trinuclear-tridentate bonding on the 3-coordinated Pt atoms of the PtS (101) surface. The adsorption energies on dry surface were in the order as: SDTBAT > SNBDTC > SNBX. The adsorption energies of collectors on hydrated PtS (101) surface also followed similar adsorption trend (SDTBAT > SNBDTC > SNBX). This suggested that SDTBAT had strong affinity with the surface. Most importantly it was found that the hydrated condition adsorption energies were significantly reduced compared to the dry condition adsorption energies. It was apparent that the SDTBAT collector displayed an ability to improve the recovery of the cooperite mineral and therefore a potential replacement of the well-known dithiocarbamate and xanthate collectors for use in PGMs.