Mechanism of metal sorption by biochar

Biochar has received potential interest as a cost-efficient and environmentfriendly sorbent material to remediate metal contamination recently. However, the mechanism of metal sorption capacity by agriculture-based biochar is still lacking. Accordingly, this review chapter demonstrates metal sorption mechanisms by biochar including physical binding, ion exchange, membrane filtration, complexation, precipitation, sorption, and electrostatic interactions and elucidate the role of corresponding biochar characteristics namely biochar preparation methods, surface area or charge, porosity, medium pH, presence of functional groups, mineral components, and pyrolysis temperature. Additionally, this review chapter addresses different techniques,namely steam or acid/base activation, composite impregnation with carbonrich materials, minerals, organic compounds, and so on to improve metal sorption capacity either through functional improvement or providing efficient surface attributes to biochar. Furthermore, this chapter describes different mathematical models to check the metal sorption efficiency by biochar. Finally, this chapter highlights the future prospects of biochar-associated metal sorption in large-scale field application cost-effectively.