Research On Flotation Of Pb-Zn Sulphide And Mechanism

The flotation of sulfide minerals is an electrochemical process, and sulfide minerals are easy to be oxidized. The oxidized degree of mineral surfaces and the type of oxidation products have a great influence on their flotation behaviors. In this paper, three kinds of typical sulfide minerals, which are galena (PbS), sphalerite (ZnS) and pyrite (FeS2), have been studied by the flotation tests of pure minerals and real ores. The influence of four oxidants (H2O2, NaCIO, K2Cr2O7and KMnO4) on the flotation behavior of these three minerals also has been investigated. At last, the mechanism of the selectivity of oxidants on these three minerals has been explored by infrared spectrum tests and cyclic voltammetry. These results can provide important guiding significance and academic value for the flotation separation of lead and zinc sulfide minerals.The results of pure mineral tests show that the oxidants of H2O2and NaClO have no obvious depressing effects on galena, but the remarkable depressing effects on sphalerite. These three minerals (galena, sphalerite and pyrite) all can be depressed by K2CrO7, and the effect of sphalerite was remarkable. The oxidants of KMnO4have no distinct depression on galena; however, it can depress sphalerite and pyrite effectively.The results of infrared spectrum tests demonstrate that the oxidants of NaClO, H2O2, K2Cr2O7and KMnO4can all depress the flotation of sphalerite by destroying zinc-xanthate on the surface. However, they cannot depress the flotation of galena with no destruction of lead-xanthate on the surface under this experimental condition. Additionally, the lead-xanthate can be damaged by K2Cr2O7, which could lead to the depression of galena.The analyzed results of electrochemical mechanism suggest that the lead-xanthate on the galena surface is slightly oxidized by NaClO and H2O2, whereas the zinc-xanthate on the sphalerite surface is strongly oxidized. Moreover, the products of xanthate reacting with the galena, sphalerite and pyrite surfaces could be damaged by K2Cr2O7. In addition, the dixanthogen of pyrite surface and the zinc-xanthate of sphalerite surface can be obviously oxidized by KMnO4, while the oxidation of zinc-xanthate on the galena surface using KMnO4as oxidant is weak.The results of flotation tests indicate that the grade and recovery of lead concentrate can achieve40.3%and68.7%, respectively; the grade and recovery of zinc in the lead concentrate can reach10.59%and6.30%, respectively using the combination of KMnO4and Z230as depressant. Thus, the good flotation-separation of lead and zinc minerals can be obtained.