Study on the Recycling of P in Phosphogypsum Leachate

After washing and curing, P is transported from the phosphogypsum to the leachate during the phosphogypsum detoxification process, providing two ideas for phosphorus recovery from phosphogypsum leachate: 1) preparation of calcium hydrogen phosphate for feed; 2) preparation of calcium phosphate. A ready-to-use calcium oxide slurry was used to recover P from phosphogypsum leachate at a slurry concentration of 20% and a quantitative link between calcium to phosphorus ratio and fixation rate was fitted by mixed use batch experiments, reaction kinetics and thermodynamics, and theoretical calculations were used to demonstrate that phosphorus cannot be completely reused in the preparation of calcium hydrogen phosphate. The findings demonstrated that: a) the residual phosphorus concentration was in the range of 1300 - 1500 mg/L for the preparation of type I feed grade calcium hydrogen phosphate from phosphogypsum leachate; b) the P removal effect could reach 99.99% for the preparation of calcium phosphate from phosphogypsum using the theoretical equation: fixation rate = 87.91 - 10.96(Ca/P) + 3.22(Ca/P)2 (R2 = 0.9954); c) The procedure follows the suggested secondary kinetics, and according to the Freundlich isothermal model, the reaction process is under the control of the chemical reaction, with a reaction index of 0.7605. This study can be used as a theoretical guide for the recovery of P from phosphogypsum leachate, the preparation of products to bring about economic by-products, and the purification of wastewater for reuse.