钛白副产硫酸亚铁制备电池级磷酸铁

Preparation of battery-grade iron phosphate using the by-product ferrous sulfate of titanium dioxide

以钛白副产硫酸亚铁净化除杂所得硫酸铁溶液为铁源,采用液相沉淀法合成电池级磷酸铁,研究了铁磷投料比、反应温度、pH、CTAB添加量对磷酸铁Fe/P、粒径及产率的影响,并通过响应面分析得到高产磷酸铁的较优合成条件为:投料比1.33、温度80℃、pH为1.6、CTAB添加量为2%。通过响应面优化实验,在保证90.98%的高产率的同时,降低了原料投料比,节省了用料成本。所得产物为无定形二水磷酸铁,经煅烧后转变为α-石英型。二水磷酸铁的一次颗粒粒径在100nm左右,二次颗粒平均粒径D_(50)为8.4μm。根据晶核形成与晶体生长理论分析了无定形磷酸铁的形成机理:磷酸铁的成核速率远大于其生长速率,体系中形成大量微小晶核,这些微小晶核因半径小于临界晶核半径而发生无规则的聚集,进而形成无定形磷酸铁。所得二水磷酸铁的元素质量分数符合电池级磷酸铁的技术指标。

Battery-grade iron phosphate was synthesized by liquid-phase precipitation using ferric sulphate as the source of iron,which was obtained from purification of by-product ferrous sulfate of titanium dioxide.The effects of iron to phosphorus feed ratio(Fe/P feed ratio),reaction temperature,pH,CTAB addition on Fe/P,grain size and yield of iron phosphate were investigated.The optimal synthesis conditions for high-yield iron phosphate obtained by response surface methodology were Fe/P feed ratio of 1.33,80℃,pH of 1.6 and CTAB addition of 2%.Through the response surface optimization experiment,the feed ratio of raw materials was reduced and the cost of materials decreased while ensuring the high yield of 90.98%.The product obtained was determined to be amorphous iron phosphate dehydrate,which was transformed intoα-quartz type after calcination.The primary particle size of iron phosphate dihydrate was about 100nm and the average particle size D_(50) of secondary particles was 8.4μm.The formation mechanism of amorphous iron phosphate was analyzed according to the theory of crystal nucleus formation and crystal growth.The nucleation rate of iron phosphate was much higher than its growth rate and a large number of micro-nuclei were formed in the system.These micro-nuclei were irregularly aggregated Chemical Industry and Engineering Progress,2024,43(8):4523-4533.because their radius was less than the critical nucleus radius and then amorphous iron phosphate was formed.The element content of the product(FePO_(4)·2H2O)was determined to meet the technical index of battery grade iron phosphate.