ABSTRACT
Mining, wastewater irrigation, sludge applications, and vehicular emission are some of major sources of heavy metal contamination in soil. Remediation of contaminated soil is essential to minimize the transfer of toxic metals to the ecological food chain. Conventional approaches for remediation, such as soil flushing, washing, electrokinetics, chemical reduction/oxidation, etc., are often costly and cause secondary pollution. As a multidimensional amendment technique, biochar has the potential to improve the soil’s physicochemical (water retention capacity, pore size, aggregate stability, pH, cation exchange capacity, etc.) and biological properties (enzymatic activity, microbial biomass carbon (MBC), etc.), increase the bioavailability of essential elements (C, N, K, etc.), and remediate heavy metal toxicity (As, Cd, Cu, Hg, Pb, etc.). Biochar is a porous, fine-grained, carbon-rich product of thermal decomposition of biomass in the absence of oxygen. Various mechanisms by which biochar remediates heavy metals include ion exchange, electrostatic interaction, physical adsorption, complexation, and precipitation. The current chapter primarily focuses on the present scenario of biochar production, its characteristics, the mechanisms of biochar and soil-heavy metals interaction, and its application for the remediation of heavy-metals-contaminated soil. The future aspects and knowledge gaps associated with biochar application has also been discussed for an environmentally and economically feasible approach.
