Attenuation of Phosphate and Fluoride fromPhosphogypsum Leachate by Rice Husk Biochar

The massive accumulation of phosphogypsum (PG) in the open air can produce a large quantity of phosphorus-(P) and fluoride-(F) rich acidic solution, which is environmentally and ecologically dangerous.However, very few studies have focused on this serious issue.In this regard, batch experiments were conducted to test the adsorption characteristics and capacity of rice husk biochar (RHB) pyrolyzed at 600 C for P and F from real PG leachate.The results indicated good adsorption capacity (3838 mg-P/kg and 2500 mg-F/kg), which was mainly controlled by electrostatic attraction and precipitation mechanisms.The column-packed RHB at a dosage of 93 g and an influent flow rate of 0.5 ml/min was the best for the P and F removal from real PG leachate.Various breakthrough curve models were used to simulate the experimental data, and the model fitting results revealed that all models except the Adams-Bohart model well simulated the dynamic adsorption behaviors of P and F. The BDST model results show that RHB can be a low-cost, safe, reliable adsorbent in real-world applications to remove P and F from PG leachate.