Flotation studies of galena (PbS), cerussite (PbCO3) and anglesite (PbSO4) with hydroxamic acids as collectors

Abstract

Currently, the mineral processing industry faces major challenges in the development and implementation of strategies and new processes for the recovery of lead from low-grade oxidized minerals, such as cerussite (PbCO3) and anglesite (PbSO4). In this study, the behavior of the individual flotation of galena (PbS), cerussite (PbCO3) and anglesite (PbSO4), without sulfidation, was investigated using benzohydroxamic acid (BHA) and octanohydroxamic acid (OHA) as collectors. Spectroscopy UV/Vis measurements were carried out to investigate the effect of pH on the adsorption of both collectors on the surface of these minerals. Likewise, contact angle measurements were conducted to evaluate the hydrophobicity imparted to the minerals. Furthermore, the selectivity of both collectors towards quartz (SiO2) and pyrite (FeS2), mineral species commonly found as gangue, was evaluated. Overall, microflotation tests showed higher recoveries of galena, cerussite and anglesite using OHA. Anglesite proved to be the most challenging mineral to float, probably because it is the most soluble of the three lead minerals tested. It requires higher dosages of OHA and the presence of sulfate (e.g., to reduce its solubility) to show good recoveries under slightly acidic conditions. Also, the recoveries of cerussite and anglesite were affected under alkaline conditions. Thermodynamic modeling suggests that the observed behavior is due to the presence of hydrocerussite (Pb3(CO3)2(OH)2), of hydrophilic nature, on the mineral surfaces. OHA proved to be the most effective collector; nevertheless, it also showed significant loss of selectivity against pyrite, although not against quartz, so its use will depend on the nature of the gangue present in the ore to be treated. BHA neither floats quartz nor pyrite. Therefore, BHA could be considered a potential candidate for the flotation of galena and cerussite due to its high selectivity. In summary, the use of hydroxamates would mitigate the impact on health and the environment that results from the use of xanthates.