白铅矿(PbCO_(3))和菱锌矿(ZnCO_(3))硫化机理的DFT研究

DFT study of sulfidization mechanism of cerussite(PbCO_(3))and smithsonite(ZnCO_(3))

采用密度泛函理论(DFT)比较研究白铅矿(PbCO_(3))和菱锌矿(ZnCO_(3))硫化机理的差异。通过在PbCO_(3)/ZnCO_(3)表面构建Pb-S/Zn-S层来模拟硫化结构。层距和Mulliken电荷的结果表明,PbCO_(3)上形成稳定的Pb-S层,而ZnCO_(3)上形成的Zn-S层不稳定。由于Pb-S层具有高的共价性,而Zn-S层具有高的离子性,因此,硫化-黄药法对PbCO_(3)浮选有效,对ZnCO_(3)浮选无效。为了回收ZnCO_(3),需要强离子性捕收剂,因此,硫化-胺法在ZnCO_(3)浮选中应用较广。PbCO_(3)和ZnCO_(3)表面硫化层结构和浮选行为差异主要是由于金属离子(Pb^(2+)和Zn^(2+))和配体(O配体和S配体)极化率的不同以及Zn^(2+)3d^(10)轨道的惰性造成的。

The differences in the sulfidization mechanism of cerussite(PbCO_(3))and smithsonite(ZnCO_(3))were comparatively studied by the density functional theory(DFT)method.Pb−S/Zn−S layers over PbCO_(3)/ZnCO_(3)surfaces are constructed to simulate the sulfidization structure.The results of layer distance and Mulliken charge suggest that Pb−S layer formed over PbCO_(3)is stable but Zn−S layer formed over ZnCO_(3)is unstable.Because of the high covalency of Pb−S layer and the high ionicity of Zn−S layer,the sulfidization−xanthate method is effective for cerussite but ineffective for smithsonite flotation.To recover smithsonite,strong ionicity collectors are required,and hence the sulfidization−amine method is applied more to smithsonite flotation.These differences in the sulfide layer structure and flotation behavior of PbCO_(3)and ZnCO_(3)surfaces are mainly attributed to the different polarizabilities of the metal ions(Pb^(2+)and Zn^(2+))and the ligands(O ligand and S ligand)and the inertness of Zn^(2+)3d^(10) orbital.