Stabilization and Remediation of Arsenic-Contaminated Soil: Fly Ash-Based Technology for Industrial Site Restoration

Arsenic contamination of various environmental components poses a serious threat to human and animal health. Soil As contamination is particularly hazardous, as soil is a vital pathway to the food chain. We conducted experiments on soil from a typical pharmaceutical and chemical industry relocation site in Hubei Province, focusing on modification using fly ash through mechanical and chemical mechanisms. We subjected varying proportions of lime, ferrous sulfate, and fly ash to mechanical ball milling and used these mixtures to perform remediation of arsenic-contaminated soil and site restoration. Our findings are as follows: in soil culture experiments, the As stabilization efficiency reached 90% within 90 days with ferrous salt-modified fly ash. In actual site restoration, As-stabilization efficiency exceeded 95% across different soil depths within 30 days, demonstrating significant stabilization effects. Optimal modified dosages were determined as 2% ferrous sulfate and 2% fly ash. After stabilization, As in the soil primarily existed in amorphous iron-aluminum oxide-bound (F3) and crystalline iron-aluminum oxide-bound (F3 + F4) and residual (F5) states. Fluctuations in the moisture content and pH mainly activated F3 and F4, transitioning them into exchangeable (F1) and surface-adsorbed (F2) states. Arsenic leaching was predominantly associated with the F1 form. Fly ash-based restoration technology demonstrates promising capabilities in waste treatment and pollution control, offering significant potential for widespread application.