| The oxidative pressure leaching process for nickel sulphide concentrates employs autoclave reactors operating in a mixed sulphate-chloride acidic solution under oxygen overpressure at around 150°C. During the process liquid elemental sulphur is produced minimising the oxygen reagent costs. Surfactant additions in the form of ligin sulphonates are needed to disperse the sulphur and prevent particle occlusion/agglomeration, which may inhibit the diffusion of dissolved oxygen to the mineral surface, halting the reaction. In this study interfacial tensions between molten sulphur and the aqueous solution were measured along with the contact angles of molten sulphur on pentlandite, (Ni, Fe)9S 8 surfaces. A prototype titanium autoclave with quartz windows was set-up equipped with a visualisation system to observe and measure under actual process conditions. The effects of solution chemistry and surfactant addition on the molten sulphur-mineral work of adhesion were elucidated. It was found that both chloride ions and ligninsulphonates significantly reduce the work of adhesion, suggesting that they will both be effective in case the process is commercialized. |
