Mechanisms of Trace Metal Elements Removal from Water using Low-Cost Biochar Adsorbents: A mini review

Trace metal elements are toxic to the environment and human health and can be removed from water through adsorption. Development of low-cost adsorbents would always been a matter of achievement of every adsorption study as usually many adsorbents were found to be expensive in nature. In this regard, biochar adsorbents gained significant attention due to high adsorption capacity, low-cost and environmental sustainability. Pyrolysis is used to produce biochar adsorbents at varying temperature ranged from 300°C-700°C. The adsorption capacities of palm fiber biochar adsorbents are remarkable which was found around ~198 mg/g for cadmium removal. However, bamboo-based biochar had 868 mg/g of adsorption capacity for arsenate removal. This review aims to provide the current discusses the sources and impacts of trace metal elements in water along with properties of biochar including its composition, surface area, pore structure, and surface functional groups. Further, various types of biomasses have also been mentioned for producing biochar such as agricultural wastes, food wastes, forestry residues, etc. The paper also discusses the different types of mechanisms involved in the adsorption of heavy metal biochar adsorbents like electrostatic attraction, ion exchange, surface complexation etc.