方铅矿表面的电子结构、氧化及浮选机理研究

用量子化学CNDO/2方法计算了清洁的和氧化的方铅矿表面以及它们对黄药(黄原酸盐)的吸附体系。结果表明:方铅矿表面态在与外来吸附质相互作用时,不仅有轨道重迭而且发生电子转移。吸附氧时,表面HOMO的电子向氧转移;吸附黄药时,表面LUMO接受黄原酸的电荷。由于氧的作用使表面正电性增强,有利于黄药吸附和方铅矿的浮游。而且表面氧化产物(SO_n)~(2-)易进入溶液与矿浆中的黄药离子交换。结果表面生成黄原酸铅而浮游,构成一种离子交换机理。支持了Sutherland K.L.等的假说。

ELECTRONIC STRUCTURE OF GALENA SURFACE OXIDATION AND FLOTATION MECHANISM

Original and oxidized galena surfaces and their xanthate adsorption system are calculated respectively by means of CNDO/2 method in quantum chemistry. The charge distribution and bonding character of those surfaces, the flotation mechanism of galena and the influence of oxygen on galena flotation are discussed. The result showed that galena surface state interacted with adsorbates not only in overlap of orbitals,but in electron transfer between them. When oxygen adsorpted, the HOMO of surface, which is mainly composed of P-orbitals of sulphur atoms, acts as an electron donor, while the LUMO,which is mainly composed of P-orbitals of lead atoms, acts as an electron acceptor when xanthate anions are adsorpted. The role of oxygen, which enhanced electron-positivity of surface and weakened Pb-S bonds, is favourable for adsorption of xanthate and flotation of galena. In addition, it was demonstrated that oxidation products (SO)tended to escape from surface toward solution to exchange with xanthate anions in solution. As a result, galena could be flotated due to forming lead xanthate. The flotation of oxidized galena follows an ion-exchange mechanism, and the hypothesis proposed by Sutherland K.L. and Wark J.W. is supported.