Preparation of Battery-Grade FePO4·2H2O Using the Stripping Solution Generated from Resource Recycling of Bauxite Residue

A novel process for the high-value-use of iron from bauxite residue was proposed in this work. The process was trying to use the iron-containing stripping solution generated during resource recycling of bauxite residue to produce battery-grade FePO4·2H2O product. Thermodynamics calculation indicates that Fe and P in the stripping solution mainly existed in the form of FeHPO4+, and the theoretical pH for the conversion reaction from FePO4·2H2O to Fe(OH)3 was 1.72. The optimal condition for the synthesis of FePO4·2H2O using the stripping solution was determined as: reaction pH of 0.8, reaction temperature of 90°C, Fe/P ratio of 1, and reaction time of 24 h. XRD result showed that the synthesized FePO4·2H2O was well-crystallized and perfectly matched with the characteristic peaks of FePO4·2H2O. Moreover, all the parameters of the synthesized iron phosphate meet the quality requirements of battery precursor.