Research On Mineral Processing And Leaching Kinetics For Coal Series Kaolin Yichang

Kaolin is one important nonmetallic mineral resource and is widely used in many industries.With the development of society and technology,the storage of the kaolin with high quality is gradually decreasing,as a result,more and more attention are being paid to the development and applications of low grade kaolin.Our country is rich of coal resources,and the coal rock series contain a large amount of coal-series kaolin which possess great value in exploitation and utilization,Therefore,it is significant to make effective use of the coal-series kaolin.Mineralogical analysis of coal-series kaolin of Hubei yichang showed that the major mineral of coal-series kaolin ore is kaolin,of which the content of SiO₂ is47.3%and the content of Al₂O₃ 32.89%.Besides,the gangue minerals are quartz,boehmite,feldspar and some other silicate minerals;and iron impurity mainly exists in the form of pyrite of which the particle size is 50³00?m;As for titanium impurity mainly in the form of anatase.The total concent of iron and titanium impurity is 3.93%,while the content of carbon is about 5%.Coal-series kaolin crystals are stacked together by single irregular crystal,of which the size is nonuniform and loose and the crystallization degree is not high.The reverse flotation-wet high gradient magnetic method was used to separate the iron impurity from the coal-series kaolin.When the grinding fineness for the content of-74?m is 83.4%,the dosage of dispersant is 200 g/t,pH is 6,the dosage of kerosene,frother,butyl xanthate and frother are 250 g/t,23.81 g/t,250 g/t and 17.86g/t,respectively.The magnetic field strength is 1.2T,pulp flow velocity is 1.5 m/s,pulsating speed is 200 r/min.the iron impurity removal rate of coal-series kaolin is74.89%.The roasting whiteness of kaolin rose from 51.32%to 68.75%when they were calcinated at 1000?for 120 min.As the dissemination size of iron impurity in the coal-series kaolin is extremely fine,so the traditional processing method is not easy to remove,chemical leaching method was used to separate the iron impurity.The optimal reaction conditions are as follows:the concentration of oxalic acid is 0.4 mol/L,pulp solid-liquid rate is 1:3,leaching time is 120 min,stirring intensity is 200 r/min.the iron removal rate of coal-series kaolin is 27.45%,and the iron content have reduced to 0.39%,The roasting whiteness of kaolin rose from 68.75%to 80.27%when they were calcinated at 1000?for 120min.Under the standard atmospheric pressure,comparing with acid leaching at room temperature,heating is beneficial to the leaching of iron impurity,however,it also has greater influence on the dissolution of aluminum.According to the fitting analysis of macroscopic kinetics model of hydrochloric acid,sulfuric acid,and oxalic acid leaching,it can be found that iron impurities in leaching process is controlled by internal diffusion,and belong to the internal diffusion control model.The apparent activation energy of Fe are 12.30kJ·mol^-1,9.89kJ·mol^-1and 12.27kJ·mol^-1.