Techniques and applications of advanced oxidation processes for degrading pollutants in wastewater using biochar-based catalysts: a critical review

Proper waste disposal is crucial for sustainable development. However, human activities have contributed to environmental pollution, particularly in water, through the discharge of untreated wastewater. An effective and environmentally friendly wastewater treatment solution is the use of biochar derived from carbonaceous materials or biomass. This review critically examines the synthesis of biochar-based (BC-based) catalysts, the mechanisms underlying their catalytic performance, the synergistic effects of combined BC-based systems, and their applications in wastewater treatment using advanced oxidation processes (AOPs). Reports from various studies indicate that combining biochar with graphitic carbon nitride (g-C3N4) enhances water splitting, hydrogen production, and pollutant degradation. Findings also reveal that under visible-light irradiation, numerous reactive oxygen species are generated for the photocatalytic degradation of organic pollutants in wastewater. Fe-Cu-doped hollow biochar sphere-supported TiO2 exhibited remarkable removal of rhodamine B (99.2%), thereby revealing the significance of reactive radicals and the high surface area of the functionalized biochar. Additionally, findings reveal that little attention has been given to microbial inactivation in wastewater, with most research focusing on Escherichia coli among other microorganisms. Future studies should focus on developing multifunctional and eco-friendly BC-based composites with validated performance in real-world wastewater treatment to ensure scalability, practical applicability, and environmental safety.