Abstract:
Biochar (BC) exhibits a great potential as an adsorbent in decontamination of water. To improve the adsorption
capabilities and impart the particular functionalities of BC, various methods (chemical modification, physical
modification, impregnation with different materials, and magnetic modification) have been developed. As
compared to surface modifications, BC-based composites provide various technical and environmental benefits
because they require fewer chemicals, lesser energy, and confer enhanced contaminant removal capacity.
Therefore, this review focuses on BC composites prepared by the combination of BC with different additives
including metals, metal oxides, clay minerals, and carbonaceous materials, which greatly alter the physicochemical
properties of BC and broaden its adsorption potential for a wide range of aquatic contaminants.
Techniques for the preparation of BC composites, their adsorption potentials for a variety of inorganic and
organic environmental contaminants, factors affecting BC properties and the adsorption process, and the mechanisms
involved in adsorption are also discussed. Modification typically alters the surface properties and
functionalities of BC composites including surface area, pore volume, pore size, surface charge, and surface
functional groups. Hence, modification enhances the adsorption capacity of BC for most organic and inorganic
compounds and ions. Nevertheless, some modifications negatively affect the adsorption of certain contaminants
because of various factors including obstruction of pores due to over coating and development of same charge as contaminant on the surface of BC. However, the use of BC composites in environmental remediation is still in its
infancy, and further research and development is needed to reach scalability and commercialization of the new
technology.
