The Reasearch Of Surface Complexation With α-PbO And ZnO Fine Particles

With the wide application of lead oxide and oxide in industry, there are higher demand for the exploration and utilization of their mineral resources. With the depletion of mineral resources, we are facing a challenge to recover the disseminated metal oxide minerals fine particle. Compared with sulfide minerals, the flotation efficiency of metal oxide ore is much lower. It is a feasible flotation process by using sulfidizing reagents to change the surfaces of the metal oxides, and then adding the appropriate collector for their flotation.However, our knowledge on the mineral surface sulphidization is lacking. As we know with the decrease of particle size and the increase of specific surface area, the surface properties of metal oxides gradually play an important role. Mineral surface chemical reactions play an important role on its applications in various fields such as flotation.This is the first time to introduce surface complexation theories to the surface sulfide complexation system. Using computer software, we studied the surface acid-base properties and the sulfidization of lead oxide and zinc oxide and with the aim to provide a theoretical basis for understanding the distribution and the adsorption of xanthate in order to effectively separate and recovery oxide materials.In this paper,α-PbO and ZnO were prepared by a hydrothermal method and characterized using a series of advanced techniques such as XRD, FT-IR analysis, and N2 adsorption/desorption method (BET). We conducted potentiometric titrations and computer calculations using software FITEQL to obtain the equilibrium constants for the surface acid–base reactions. The experimental results showed that there is a sharp "jump" in titration curves using different concentrations of lead oxide solid particles. An unusual pH increasing was observed with adding acid to the mineral suspension. The possible mechanism may be that when the pH value of lead oxide is reduced to the iso-electric point i.e. pHiep, the repulsions are smaller than the attractions between the particles. So the particles form aggregates which blocsome OH- ions. When the particle surfaces re-charged, the aggregates break and the OH- is released, resulting in the pH increases.The surface sulphidization of synthesizedα-PbO and ZnO samples was obtained by thermolysising xanthate adsorbedα-PbO and ZnO particles. IR and EDS determination results showed that the surface sulfide were formed after calcination the xanthate adsorbed lead and zinc oxide samples, which prove that the thermolysising the xanthate adsorbed metal oxide is an effective method to obtain the surface sulfidized metal oxide samples. UV - visible absorption spectra were used to study the adsorption of xanthate with varying carbon chain length at the surfaces ofα-PbO and ZnO before and after sulphidization. The results showed that the adsorption of xanthate on mineral surface is based on an ion exchange mechanism; OH- ion in solution can replace adsorbed xanthate by a competitive adsorption. Therefore, pH value is an important factor for xanthate adsorption. For the same absorbent, the adsorption capacity of xanthate increases with increasing the solid concentration; it suggests that the surface area is also an important factor. Compared with the oxide minerals, the hydrated surfaces after the sulphidization have two types, i.e.≡MeOH and≡MeSH. Xanthate ions can easily bind with metal ion to form surface metal xanthate. Due to the hydroxyl group formed at the surface metal site after hydration, xanthate adsorption can take place only through a competitive adsorption with the surface hydroxyl groups. Thereforefor the same kind of xanthate and the same solids concentration, under the same pH value, the adsorption capacity ofα-PbO particles with sulfide surface is higher than that ofα-PbO. This rule also applies to the xanthate adsorption those of ZnOn. Comparison of the adsorption capacity of four solid samples, the adsorption capacity order is:α-PbO/PbS >α-PbO > ZnO/ZnS > ZnOIt can significantly improve the flotation efficiency and broad the effective xanthate adsorption pH range by surface sulphidization. In addition, for the same adsorbent, the adsorption capacity of butyl xanthate was higher than that of ethyl xanthate.