Mechanisms and Environmental Applications of Biochar for Heavy Metal Remediation in Contaminated Soils

Abstract

Soil contamination by heavy metals poses significant threats to ecosystems and human health. Biochar, a carbon-rich material produced from biomass pyrolysis, has emerged as a promising and cost-effective amendment for immobilizing heavy metals in polluted soils. This paper provides a critical review of the key mechanisms governing the immobilization of heavy metals (e.g., Pb, Cd, Cu, Zn) by biochar, including electrostatic attraction, ion exchange, surface complexation, and precipitation. Furthermore, this study evaluates the primary factors influencing remediation efficiency, such as pyrolysis temperature, feedstock type, and soil conditions. The results synthesized from existing literature indicate that biochar application can effectively reduce metal bioavailability and leachability, while also improving soil physicochemical properties. In summary, understanding the mechanism-property relationship of biochar is essential for optimizing its field application. This review therefore provides a theoretical basis and practical guidance for using biochar in sustainable soil remediation.