Ammonia modification for enhancing adsorption of sulfide species onto malachite surfaces and implications for flotation

In this study, the surface modification of malachite with ammonia was developed as a promising method to enhance the adsorption of sulfide species onto the mineral surface. The flotation recovery of the ammonia-modified malachite was significantly improved under the same flotation condition compared with that of bare malachite. This result can be ascribed to the fact that the adsorbed amount of S species on the mineral surface increased because of the considerable affinity of the ammonia-modified malachite for sulfide ion species in the pulp solution. The negativity of the zeta potential of malachite increased, which implied that more S species was adsorbed onto the surface of the ammonia-modified mineral. This phenomenon facilitated the attachment of the collector. XPS analysis confirmed the enhancement of sulfide ion species adsorption onto the ammonia-modified malachite surface. In addition, the amount of cuprous sulfide species on the modified surface increased. The mechanism by which ammonia modification enhances the sulfidization of malachite was further studied by solution chemistry calculation. The hydrophilic Cu(OH) 2 coated on the malachite surface was detrimental to the adsorption of sulfide ion species, whereas the involvement of Cu ( NH 3 ) 2 2 + changed the surface species distribution and improved the sulfidization of malachite, thereby facilitating its flotation recovery.