Activation mechanism of zinc ions in cassiterite flotation with benzohydroxamic acid as a collector

Abstract

The presence of Pb2+ can activate cassiterite flotation, however, its biotoxicity may lead to environmental issues. Therefore, the feasibility of using Zn2+ instead of Pb2+ in cassiterite flotation was investigated in this study. The effects and mechanism of Zn2+ on the floatability of cassiterite were analyzed using benzohydroxamic acid (BHA) as the collector. The results indicated there was a higher recovery of cassiterite in the presence of Zn2+ than in the presence of Pb2+. The maximum recovery of cassiterite in the presence of Zn2+ was 90.54%. This was attributed to an increase in the adsorption quantity of BHA on the cassiterite surface with Zn2+. The maximum growth range was 4.47 × 10-6 mol/g. Further chemistry analysis of the solution indicated that BHA and Zn2+ were mainly present in the form of BHA molecules and Zn(OH)+ at pH 7.5–8.0. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) confirmed that Zn(OH)+ reacted with OH– on the cassiterite surface to form a Zn-O bond. Then, this metallic bonding combined with BHA molecules to generate a new type of chelate ring (-Sn-O-Zn-BHA). This structure made BHA attach more firmly on the cassiterite surface, causing a rise in the recovery of cassiterite.