Biochar Derived from Agricultural Residues for Wastewater Contaminant Removal

The valorization of agricultural residues helps improve crop economic efficiency and alleviate environmental pressures. Owing to the merits of simplicity, high efficiency, low costs, and scalability, adsorption removal of contaminants using biochar has been widely investigated. The adsorption removal of organic and inorganic contaminants from wastewater using biochar derived from agricultural residue follows the principles of the circular economy and green chemistry, facilitating both environmental remediation and agricultural development. Due to the distinctive precursors—agricultural residues—biochar exhibits unique physicochemical properties, enabling it to interact differently with contaminants in real wastewater. Herein, this review addresses the knowledge gap in wastewater remediation using agricultural residue-based biochar. It compiles the principles of adsorption with agricultural waste-derived biochar, including general concepts, interactions between biochar and wastewater contaminants, and selective adsorption. The preparation, activation, modification, functionalization, and regeneration of such biochar, as well as their application to wastewater remediation, are comprehensively outlined. Furthermore, the economic evaluation and environmental impacts, as well as the future directions and challenges in this field, have also been presented.