Growth of covellite crystal onto azurite surface during sulfurization and its response to flotation behavior

In this work,the growth of copper sulfide crystal onto azurite surfaces during sulfurization and its response to flotation are investigated.Filed emission scanning electron microscopy-energy dispersive X-ray spectroscopy(FESEM) and X-ray diffraction(XRD) studies confirmed that the sulfurization of azurite is not limited to the mineral surface,but rather penetrates into the bulk to form covellite crystal(synCuS),creating favorable conditions for the stable adsorption of xanthate and greatly promoting the azurite flotation.Additionally,as demonstrated by X-ray photoelectron spectroscopy(XPS) and time of flight secondary ion mass spectrometry(TOF-SIMS) analyses,a redox reaction occurred during this process,and Cu(Ⅱ) onto the mineral surface was reduced to Cu(Ⅰ).Correspondingly,reduced S^(2-) was oxidized to(S_(2))^(2-),(S_n)^(-2),and even to deeper oxidation state S~0,(S_(x)O_(y))^(n-) and SO_(4)^(2-).Excess sodium sulfide strengthens copper sulfide to form onto the azurite surface,and provides enough raw material for crystal copper sulfide to grow,resulting in the formation of "flake-like" covellite with a better crystallinity.However,the floatability of azurite decreased dramatically under this condition,because the generated massive colloidal copper sulfide in flotation pulp deteriorates the flotation environment,resulting in a decreased effective adsorption of collector onto azurite surfaces.

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(NH_(4))_(2)SO_(4)during the sulfurization of azurite and its response to flotation were investigated.The flotation results showed that adding(NH_(4))_(2)SO_(4)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(NH_(4))_(2)SO_(4)prior to sulfurization,the formation of Cu(NH_(3))_(n) ^(2+)intermediate products changed the path of the sulfurization reaction,which slowed the direct impact of HSon 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.