Research On Vacuum Purification Of Molybdenum Disulfide

Molybdenum disulfide is an important solid lubrication and semiconductor material.It also shows potential application prospects in some advanced fields such as flexible electronics,transparent transistors,and biology.Molybdenum concentrate is the main raw material for preparing molybdenum disulfide.Sulfides of metal elements such as arsenic,tin,lead,bismuth,zinc,and iron would be selected together with molybdenum disulfide in the flotation process of molybdenite,which need to be removed in the subsequent process.The current process of removing impurity by chemical leaching method has disadvantages such as high cost,long process and serious pollution,etc.In this paper,vacuum distillation and vacuum chlorination were proposed to separate impurities and purify molybdenum disulfide combined with the advantages of vacuum metallurgy.An environmental-friendly,efficient,and simple purification process of molybdenum disulfide was explored combined with the deep impurity removal process by oxidation leaching.Detailed research contents and progress are as follows:(1)Based on the calculation of saturated vapor pressure in vacuum distillation process,and Gibbs free energy and equilibrium pressure in vacuum decomposition process of metal sulfides in molybdenum concentrate,the feasibility of vacuum distillation for impurity removal was analyzed.The results show that the vapor pressures of As₂S₃?SnS₂?PbS?Bi₂S₃ and ZnS are much greater than MoS₂ at same temperature,which can be removed by vacuum distillation.While FeS₂ and CuS are easily decomposed into FeS and Cu₂S when heating which cannot be removed by vacuum distillation.Bi₂S₃ is decomposed into Bi vapor andS vapor when heating,which can be removed easily.(2)Experimental study of vacuum distillation for molybdenum disulfide was carried out.The results show that the removal of impurities is the best under the conditions of P?5-15 Pa,and T=1373 K for t=80 min.The volatiles collected were detected and analyzed.The results show that PbS with ultra-low content in the raw material was further evaporated,while impurity elements Na and Al with relatively high content volatilized in the form of fluorides.The purity of molybdenum disulfide increases from 97.01%to 99.18%.(3)Experimental study of vacuum distillation for molybdenum concentrate was conducted.The results show that the removal of impurities is the best under the conditions of P?5-15 Pa,and T=1373 K for t=80 min.The analysis results of the collected volatiles show that lead,zinc,and bismuth elements are volatilized in the form of sulfide.Moreover,a small amount of molybdenum oxide is volatilized.Molybdenum concentrate's grade increases about 2%.(4)The volatilization characteristic of metal chloride and thermodynamics of reactions between sulfides and calcium chloride under vacuum condition were analyzed.The results show that FeS can be chloridized into Fe Cl₂ and volatilized.Experimental study of chlorination roasting for molybdenum concentrates shows that at 1 Pa the Fe content can be reduced to 0.43%when the mass ratio of calcium chloride to molybdenum concentrate is 1.5:1 and the temperature is 1123 K.(5)Oxidation leaching experiments for distillation residues of molybdenum concentrate were carried out.The results show that iron and copper could be further removed by leaching of distillation residues of molybdenum concentrate in high pressure reactor using hydrogen peroxide.The removal effect is better with the increase of H₂O₂ concentration.When the concentration of H₂O₂ is 30%,Fe and Cu contents decrease to 0.35%and 0.0094%respectively.