Exploring the effects of different process water sources on xanthate adsorption and flotation performance

Abstract

Driven by environmental concerns and restrictions arising from them, the mining industry has instituted an initiative to recycle process waters within plant operations. This has the two-fold advantage of using minimal freshwater for mining, thus freeing the water for other applications, and limiting the release of potentially toxic discharge to the environment. However, in recycling their process water, plant operations alter the chemistries of these waters; and since reagents such as collectors are active at the solid–liquid interface, changes in the aqueous phase are expected to affect the flotation responses of ores. A polymetallic ore was floated in synthetic plant waters of varying ionic strengths and actual onsite plant waters, with aerophine and sodium isopropyl xanthate (SIPX) as collectors. The study showed that water quality has a quantifiable effect on SIPX adsorption. The respective effects of water quality and collector adsorption on ore flotation could not be irrefutably decoupled. However, increased adsorption did not necessarily result in improved grades and recoveries. This study specifically showed that Cu recoveries are reduced in recycled water owing to the presence of residual SIPX. The presence of residual SIPX in recycled water increased Ni recoveries and grades. Tailings water at the end of flotation may be more suited to Ni flotation owing to the presence of residual SIPX. The use of recycled water containing residual SIPX was therefore beneficial for pentlandite flotation but not for chalcopyrite, thus suggesting the importance of the consideration of components in recycled process water and points of addition in circuit configuration and design where closed water circuits are implemented. Retrieving tailings water directly after Cu flotation for recycling to Cu flotation circuit would therefore allow a more suitable water type.