The Study On Preparation Of Battery Grade Iron Phosphate With Titanium Dioxide Byproduct Ferrous Sulfate

In the production of titanium dioxide by sulfuric acid method,a large amount of by-product ferrous sulfate is produced,because they contain Ti?Mn?Al and other impurities can not be directly utilized,most of them are disposed of as waste products,stacked anywhere,causing serious pollution to the environment.Some of these by-products are used for feed additives,water purifying agents,agricultural fertilizers,and some are used to produce iron oxide pigment.The recycling of byproduct ferrous sulfate has received extensive attention.The use of ferrous sulfate as a raw material for the synthesis of iron phosphate not only reduces the cost of synthesizing iron phosphate,but also opens up a new way for the utilization of titanium white by-product ferrous sulfate.The purification of ferrous sulfate from titanium dioxide by-product and the preparation of battery grade iron phosphate were studied.Firstly,the purification and impurity removal experiment of ferrous sulfate was carried out.Compared with the effects of colloidal precipitation adsorption method,chemical precipitation method and hydrolysis method on impurity removal rate,the effects of sodium sulfide content,hydrolysis temperature,hydrolysis time and hydrolysis p H value on impurity removal rate were studied by chemical precipitation method and hydrolysis method.The optimum experimental conditions were obtained as follows:sodium sulfide content is 4.0%,hydrolysis temperature is 90?,hydrolysis time is 2 h.The p H value of hydrolysis is 4.0.The results show that the removal rate of Mn?Ti?Al can reach more than 97%.Then iron phosphate was synthesized from ferrous sulfate after impurity removal.Iron phosphate was synthesized by controlled crystallization method.The effects of reaction temperature,molar ratio of phosphorus to iron,dosage of surfactants CTAB and p H value on the particle size and the ratio of Fe/P were studied.The orthogonal test was carried out with the particle size of iron phosphate as the parameter.Through the analysis of the experimental results,the optimum technological conditions for the synthesis of iron phosphate with small particle size were obtained:the molar ratio of phosphorus to iron was1.5:1,and the reaction temperature was 85?.The dosage of CTAB was 1.5%and the p H value was 1.8.The sample was characterized by SEM,XRD,particle size distribution.The results of particle size distribution test showed that the average particle size of the sample was about 1000nm,and the particle size distribution was narrow,the scanning electron microscope diagram showed that the morphology of the prepared iron phosphate product was regular,the particles were spherical and the dispersion property was good,the XRD test results showed that the sample had good crystallinity and belonged to monoclinic system.Elemental analysis showed that the synthesized iron phosphate meets the technical specifications of battery grade iron phosphate.LiFePO₄was prepared by carbothermal reduction method using self-made iron phosphate as iron source,lithium hydroxide as lithium source and glucose as reducing agent and carbon source.The phase of the material was analyzed by XRD.