Abstract:In the process to produce FePO4 which uses recycled resources such as spent LiFePO4 and Fe2SO4 (byproduct in producing TiO2), the mother liquor will concentrate cationic impurities such as Li+, Na+, Ca2+, Mg2+, Mn2+, Ni2+, and Al3+. The impurity ions of mother liquor should be removed so that the phosphoric acid can be reused. Impurities were removed from FePO4 mother liquor by electrodialysis method. Effect of current density on purification efficiency was explored. The results show that removal rate of impure ions is Li+ 41.18%, Na+ 54.55%, Ca2+ 64.29%, Mg2+ 54.02%, Mn2+ 35.71%, Ni2+ 46.38%, and Al3+ 16.67% under the condition of long-term operation with reasonable process parameters. After removing the impurities, the mother liquor can be used in producing FePO4 which prevents the loss of phosphorus resources. When the current density rises, the power consumption rises and the current efficiency drops. At the same time, the impurity removal rate drops under the same ratio of replacement amount of flow of electrolyte to current flow. The optimal operating current density is 2 A/dm2. By using the electrodialysis device with cationic membrane area of 1 dm2, the impurity removal capacity of FePO4 mother liquor is 52.14 mL/h and the consumption of cathode liquid (150 g/L sulfuric acid solution) is 10.41 mL/h.