Computational modelling of interactions between gold complexes and silicates

The interactions of gold complexes including gold chloro-hydroxy species, gold thiosulphate and gold thiourea, with protonated and deprotonated silicate monomers, are studied using density functional theory (DFT) methods. The previously published optimal geometry of gold complexes is used here, together with the geometry of silica monomers that is optimised and compared with experimental and available theoretical data. COSMO (COnductor like Screening Model) solvation simulation of different systems (for different pH and gold complexes) is also used to represent the surrounding aqueous environments. The interaction energy of gold complexes with silica species based on theoretical studies has been shown to correlate well with the extent of silica preg-robbing (sorption) per surface area of quartz determined experimentally. The ability of DFT to compute the interactions of different gold complexes involving significant relativistic effects, with other species, has been demonstrated in this study. This work allows us to explain and control the chemical processes which result in loss of gold from solution in hydrometallurgical extraction.