The impact of water quality on flotation performance

Water represents 80-85% of the volume of mineral pulp processed in flotatio n circuits. Imperatives for a more detailed focus on circuit water quality and its control have come from increasing requirements to use relatively im pure primary water supplies (e.g. high salinity, treated sewage) and high p roportions of recycle from tailings dams, thickener overflows, dewatered an d filter products. An integrated methodology for examining process water qu ality and its effect on minerals separation has been developed coupled with minerals surface chemistry across the complete processing circuit. Unrecog nised factors, including varying proportions of water streams (daily or hou rly), colloidal precipitation, highly variable pH and Eh, reaction and diss olution of minerals, minerals surface layer coatings, residual reagents and their reaction products, and microbiological activity have been studied in eight mineral processing circuits. The methodology combines: solution surv ey and modelling; microbiological surveys; minerals surface analysis and mo delling; and process response. It has been possible to match the predicted (model) pulp chemistry with that measured from surveys of the solution and mineral surfaces. Treatment methods have included: monitored and balanced s tream combinations; organic species removal; flocculation and aggregation; induced precipitation; dissolved air flotation; ageing (oxidation, UV expos ure); and chemical surface conditioning of minerals. Some specific achievem ents from the methodology applied in plant and laboratory testing, with exa mples from case studies, will be described.