Study on the effects of new developed biochar and sludge composite materials on copper and lead contaminated soil and its remediation mechanism

In this study, composite repair material was obtained by composting and fermentation of straw biochar and sludge according to the mass ratio of 1:4. The remediation effect of its composite remediation materials on heavy metals copper (Cu) and lead (Pb) in soil was investigated. The characterization results of the composite remediation material showed that the material had rich pore structure, high specific surface area and rich functional groups such as hydroxyl, carbonyl and carboxyl groups, and had high adsorption capacity for heavy metals in contaminated soil. The passivation effect of Cu and Pb in contaminated soil was investigated under different application amount (3%, 5%) and passivation time (15d, 60d). The changes of Cu and Pb content, availability and morphology distribution in the soil before and after the addition of remediation materials were analyzed. The results showed that the passivation effect of Cu and Pb in soil was significantly enhanced with increasing passivation time and application amount. In conclusion, the addition of remediation materials effectively reduced the content and effectiveness of heavy metals in the soil and promoted the change of Cu and Pb morphology in the heavy metal-contaminated soil, thus realizing the remediation of the heavy metal-contaminated soil.