Role of ammonium sulfate in sulfurization flotation of azurite: Inhibiting the formation of copper sulfide colloid and its mechanism

In this study, the role of (NH4)2SO4 during the sulfurization of azurite and its response to flotation were investigated. The flotation results showed that adding (NH4)2SO4 prior to sulfurization decreased the formation of colloid in flotation pulp, and the floatability of the suppressed azurite caused by excess sodium sulfide was restored. After adding (NH4)2SO4 prior to sulfurization, the formation of Cu(NH3)n2+ intermediate products changed the path of the sulfurization reaction, which slowed the direct impact of HS− on the azurite surface. The nucleation rate was reduced, and the growth of copper sulfide crystal was improved. Covellite (syn, CuS) with larger crystal grains was formed on the azurite surface, thereby enhancing the mechanical stability of copper sulfide products onto the mineral surface. Therefore, the generated copper sulfide colloid significantly reduced, ultimately promoting the effective adsorption of xanthate on the azurite surface.