Research Progress on the Role of Biochar in COD Degradation in Wastewater

Biochar has emerged as a promising eco-friendly material for addressing chemical oxygen demand (COD) in wastewater treatment, offering sustainable alternatives to conventional purification methods. This review systematically examines its multifunctional roles through physicochemical characteristics including developed surface area, porous structure, and surface functional groups that collectively enable effective COD removal via adsorption, catalytic degradation, and microbial interactions. The oxidation-reduction reactions facilitated by persistent free radicals and oxygen-containing functional groups demonstrate particular effectiveness in decomposing complex organic pollutants. Recent advances highlight optimization strategies through precursor selection, pyrolysis condition modification, and hybrid systems combining biochar with advanced oxidation processes or biological treatments, which synergistically enhance treatment efficiency and operational stability. Practical applications reveal biochar's adaptability across various wastewater types, though performance variations depend on feedstock sources, activation methods, and reactor configurations. Environmental sustainability assessments indicate reduced secondary pollution risks compared to traditional chemical treatments, with potential for resource recovery through spent biochar utilization in soil amendment. Current challenges center on long-term stability in continuous flow systems, cost-effective regeneration techniques, and standardized evaluation protocols for industrial-scale implementation. Future research directions emphasize biochar-based composite material development, artificial intelligence-assisted process optimization, and life-cycle assessment frameworks to advance circular economy applications in water pollution control.