Analysis of fixation effect and mechanism of phosphorus in phosphogypsum by multiple substances combination

Two phospho-accumulating bacteria were enriched and screened in the soil of the slag field by the harmless treatment method of phosphogypsum by microbial-plant combination, and the bacteria were identified as Pseudomonas sp. and Pseudomonas putida, respectively. The phosphogypsum modified by quicklime was mixed with a small amount of soil according to the mass ratio, and was evenly mixed with the already allocated organic fertilizer and microbial liquid bacteria agent. The mixture was put into the infiltration soil column device according to different mixing ratios, tall fescue was planted on the surface, and the leachate was collected at the bottom. The change of total phosphorus concentration in the liquid was measured by ammonium molybdate spectrophotometry. With phosphogypsum: soil: organic fertilizer: microorganism: grass seeds mass ratio of 7∶3∶0.2∶0.2∶0.03∶0.03, the phosphorus leaching concentration in the liquid was below 1 mg/L. The concentration of total phosphorus in the leaching solution of group 8∶2∶0.2∶0.2∶0.03∶0.03 was no more than 4 mg/L, and the concentration of total phosphorus in the leaching solution of fresh phosphogypsum was 633.9 mg/L. The fixation rate of phosphorus in the combined multi-substance treatment of phosphogypsum was more than 99%. The survival rate of the selected strains in the mixed soil was up to 6.4×10⁶ cfu/mL, and the number of viable strains maintained stable or slow growth trend over time. This experiment successfully solved the problem of excessive phosphorus leaching concentration in the phosphogypsum accumulation area, and provided effective support for harmless treatment of phosphogypsum.