Two step treatment of phosphogypsum: Targeted solidification/stabilization and soil utilization

Phosphogypsum (PG) is a typical acidic bulk solid waste generated in the phosphate chemical industry. Due to the harm of PG to the environment, the resource utilization path is hindered, and the utilization of building materials, roadbeds, and other directions is limited. This study proposed a two-step treatment process of PG solidification/stabilization and soil utilization. Firstly, quicklime was used to target and solidify acid soluble impurities in PG. Secondly, the solidified and stabilized PG and biomass were subjected to co-pyrolysis treatment to investigated the leaching toxicity and available plant elements release of co-pyrolysis residues under different co-pyrolysis temperature, biomass content, and co-pyrolysis time conditions. The chemical properties of healthy soil in forest land were compared to determine the feasibility of PG soil chemical utilization. This study found that adding 5 % quicklime to PG can significantly solidify and stabilize toxic and harmful substances, with a solidification efficiency greater than 90 %. At the same time, under the conditions of co-pyrolysis temperature of 900 ℃, biomass content of 20 %, and co-pyrolysis time of 5 h, the leaching toxicity of co-pyrolysis residues showed extremely low concentrations, with leaching concentrations of P and F reduced to below 0.5 mg/L and 1.2 mg/L, respectively. The release of available elements in plants has been enhanced, with release concentrations of N, P, and K at 72 mg/L, 15 mg/L, and 20 mg/L. This study provides a new treatment pathway for the large-scale application of PG in forest soil utilization. • Proposed a two-step treatment technology of targeted solidification and soil utilization of phosphogypsum. • It was found that quicklime can significantly reduce environmental risks in the treatment of phosphogypsum. • Co-pyrolysis treatment of phosphogypsum and biomass can achieve soil functionality.