Cationic flotation of smithsonite and dolomite from Brazilian Ambrósia Norte deposit.

Abstract

The flotation of low-grade oxidized zinc ores has been commonly used to produce marketable concentrates for many years. Several flotation routes are being successfully used: cationic, anionic and a mixture of anionic and cationic. The choice of the route taken is dependent on the major zinc-bearing minerals in the deposit of interest and its associated gangue. Since both the mineralogical composition of zinc ores and the chemical composition of smithsonite and dolomite vary between deposits, the physico-chemical conditions under which selective flotation processes are determined must be established for each unique case. In this study, cationic flotation tests were performed using smithsonite and dolomite samples from an unstudied oxidized zinc deposit in Brazil, using Na2S as the sulfidizing agent, sodium silicate as the depressant and amine as the collector. The surface charges of both minerals were investigated with and without reagents. These tests showed that the optimum conditions of flotation were reached at pH 11. Na2S allowed a significant increase in the recovery of smithsonite, which implies lower amine consumption. Sodium silicate functioned as a dolomite depressant at concentrations up to 6.0 mg/L. The results for both flotation and the zeta potential of the minerals were analyzed using specimen diagrams of the reagents and compared with studies published in previous literature.