A Review on Use of Biochar for Remediation of Heavy Metal Polluted Soils

Abstract

Heavy metal contamination of soils and its control has become a challenging issue globally. Remediation of heavy metals is essential because it causes serious health issues on living organisms due to its harmful effects on the soil biota, crop yield, and pollution of ground water table. It is also found that heavy metals mineralization into more stable form does not occur easily. High concentration of heavy metals like copper, zinc, cadmium, lead, nickel, arsenic, and mercury are most toxic and carcinogenic in nature. Biochar, a carbon-rich organic material has established its position for heavy metal remediation in soil and aqueous solutions. It is produced by thermal decomposition of different biomass feedstock under anaerobic condition at a specified temperature ranging from 250° to 900 °C. pH, cation exchange capacity, functional groups, porosity, and surface area are the main factors influencing the performance of biochar as heavy metal adsorbent. Analysis from SEM, FTIR, and XRD techniques has built enough proof that biochar acquires more potency for the immobilization of heavy metals. Recently, it is seen that activation of biochar has also helped in immobilizing specific contaminants in soil. Biochar activation process can be fulfilled by various physical and chemical methods. Activation improves physicochemical properties of b iochar thus enhancing its use as adsorbent. This review article summarizes the efficiency of biochar for remediating harmful inorganic polluted soils. It also shows comparison of the performance of pristine biochar with activated biochar for the heavy metal adsorption in soils.KeywordsBiochar; ImmobilizationHeavy metalsActivation