To explore the remediation mechanism and effect of biochar and KH₂PO₄ on soils contaminated with heavy metal ions Hg²⁺, Cd²⁺ and Pb²

In this study, wheat straw-derived biochar was prepared by setting a temperature of 400 °C under an oxygen-limited environment using the technique of "programmed temperature increase control". The results showed that the biochar had a strong adsorption capacity for Hg²⁺, Cd²⁺ and Pb²⁺ ions, and the adsorption pattern was Hg²⁺>Cd²⁺>Pb²⁺. There was a competitive adsorption effect during the coexistence of the ions. The results of the soil remediation tests showed that the effects of biochar on soil physicochemical properties and heavy metal distribution was generally greater than those of KH₂PO₄ in single or combined contaminated soil. The adsorption effect of heavy metal ions in soil was the best in the case of mixed additions. The results can provide a scientific basis for the treatment of heavy metal contaminated soil with wheat straw biochar in the future.