Development and mechanistic study of phosphate tailings based soil heavy metal prophylactic agents with encapsulated...

The development of materials for the remediation of the environment from solid waste represents an effective utilization strategy. This study presents a novel phosphorus-based slow-release soil agent (SLPs) developed through acid activation of phosphorus tailings. SLPs aim to improve soil properties by gradually releasing phosphorus (P), reducing Pb mobility, and preventing heavy metal contamination. SLPs were synthesized by forming an encapsulated structure via calcification of sodium alginate with calcium (Ca²⁺) and magnesium (Mg²⁺) from the tailings, achieving controlled P release. In soil, SLPs increased P content from 0.23 mg/g to 2.53 mg/g and soil organic matter (SOM) from 8.6 g/kg to 40.19 g/kg, significantly enhancing humic acid, fulvic acid, and organic phosphorus (OP) levels. ESP treatment also shifted the soil P pool, increasing apatite inorganic phosphate (AP) from 0.04 mg/g to 0.16 mg/g, non-apatite inorganic phosphate (NAIP) from 0.12 mg/g to 1.48 mg/g, and OP from 0.05 mg/g to 0.67 mg/g, with OP reaching a peak proportion of 28.55%, up from 23.48% in controls. Correlation analysis and microbial pathway data indicate that OP and microbial communities contribute to Pb stabilization in ESP-treated soil, raising soil Pb stabilization capacity from 7.6 to 8.4 mg/g to 36.2 mg/g. This study highlights a sustainable path for phosphorus tailing use, providing theoretical support for SLP development and emphasizing the role of OP in Pb stabilization.