Acta Petrologica et Mineralogica

The phosphorus in phosphogypsum leaches out under the eluviation of rainwater and will pollute the waters near the storage site. In this study, biochar was used to solidify the phosphorus in phosphogypsum to reduce its impact on the surrounding waters. The experiment mainly included simulating solidification experiment and leaching out experiment, analyzed the effects of biochar dosage, reaction time and temperature, initial pH value on solidification effect. The products after solidification were analyzed by XRD and SEM-EDS. The results showed that the biochar had an obvious solidification effect on phosphorus in phosphogypsum, the maximum solidifying capacity per unit reached 13.20 mg/g; under the condition of T=293 K and initial pH=7, the reaction equilibrium time was 72 h, and the equilibrium phosphorus concentration of the leaching solution C_e=1.40 mg/L; the temperature increase was helpful to improve the solidifying effect of biochar, when the reaction temperature T=308 K, the equilibrium phosphorus concentration of the leaching solution C_e=0.167 mg/L; the alkaline condition was conducive to the continuous solidification reaction, under the condition of pH=11, the equilibrium phosphorus concentration of the leaching solution C_e=0.153 mg/L.The CaSO₄·2 H₂O in phosphogypsum was dissolved, Ca²⁺ was combined with the surface of biochar which is electronegative, chemical adsorbing phosphate radical in the solution, formed flocculent, clustered hydroxyapatite(HAP), the leaching phosphorus can be effectively controlled.

phosphogypsum; biochar; solidification; hydroxyapatite