Surface reactions in aqueous metal sulfide systems

Sammanfattning: Surface reactions in aqueous metal sulfide systems have been studied. The composition and stability of various complexes at the PbS-H20 the PbS/H20 and ZnS/H20 interface were evaluated. Experimental techniques widely used in solution chemistry such as potentiometric titrations and solubility measurements were applied in studying surface reactions in these systems, in conjunction with zeta potential and spectrophotometric determinations. Computer assisted analysis, using advanced computer programs like FITEQL and SOLGASWATER was used as a main method to treat data and to establish speciation models. Experimental data and theoretical values were compared and good agreement was achieved. Acid-base and ion exchange properties at the metal sulfide/water interface were discovered, which form basic reactions in metal sulfide suspensions. The complexation of sulfide and xanthate ions at the sulfide mineral surface was also quantitatively studied and a series of equilibrium constants for surface reactions are presented. The correlation between surface complexation by protons, hydroxide and crystal component ions, like metal and sulfide ions, and surface charge was qualitatively investigated, and furthermore the potential determining ions at the sulfide surface were identified. Special attention is paid to the applications of the surface reactions in flotation systems and some flotation mechanisms are discussed based on these surface reactions.