An evaluation of hydroxamate collectors for malachite flotation

•The effect of seven hydroxamate collectors on malachite flotation was investigated.•Separation of malachite from quartz in a synthetic ore was obtained.•All seven collectors investigated selectively adsorb onto the surface of malachite.•Benzo- and two C8 alkyl hydroxamates resulted in the best flotation response.

Copper oxide minerals, such as malachite, do not often respond well to traditional copper sulphide collectors, and require alternative flotation schemes. Hydroxamic acid collectors have been suggested as a means to directly float malachite; however, there is limited information on the effect of reagent structure on the performance of these collectors. This paper investigated the effect of five alkyl hydroxamates and two aromatic hydroxamates on the flotation of a synthetic ore composed of pure, fully liberated, malachite and quartz. Zeta potential measurements were used to aid in understanding reagent adsorption onto the surface of the two minerals. The collectors were then evaluated using bench scale flotation results. While zeta potential measurements suggested that all the collectors investigated selectively adsorb onto the surface of malachite, only benzohydroxamic acid and C8 alkyl hydroxamates were effective collectors in the flotation of malachite. Benzohydroxamic acid was the most selective; however, significantly lower dosages of C8 alkyl hydroxamates were required to obtain similar malachite recoveries, with minimal increases in quartz recovery. Benzo- and octylhydroxamic acid were further examined for the flotation of fine (−38 μm) particles. For fine particle flotation experiments the effect of temperature was also investigated as a means to improve the flotation performance.