Surface activation of malachite by ammonium acetate for improved flotation separation of malachite from calcite

Abstract

Flotation separation of malachite from calcite is hampered by the surface homogenization of the two mineral surfaces. Therefore, in this study, ammonium acetate (CH3COONH4) was used to improve the flotation separation of malachite from calcite. The results of micro-flotation experiments revealed that, in the presence of CH3COONH4, the recoveries of malachite and calcite were, respectively, 85.91 % and 23.73 %, which was an improvement over the experiment conducted without CH3COONH4. Analyses of the surface morphology showed that CH3COONH4 prevented the adsorption of Cu–S on calcite, leading to a significant decrease in the calcite surface roughness. CH3COONH4 also prevented the oxidation of sulfides, which facilitated the formation of highly crystalline Cu–S on malachite. Additionally, CH3COO− prevented the formation of a dense sulfide layer on calcite. The adsorption of HS− on the surface of malachite was more energetically advantageous with NH3 than without NH3. In addition, adsorbed CH3COO− sterically hindered the adsorption of Cu–S on the O site of calcite. Bonding between the carboxyl group and Cu–S adsorbed decreased calcite activation. Therefore, CH3COONH4 catalyzed the sulfidation of malachite and inhibited calcite activation by adsorbed Cu–S, leading to improved flotation separation of malachite from calcite.