Biochar-Based Environmental Carbon Materials for Water Pollution Control: Modification Methods, Mechanisms, and Environmental Impacts – A Comprehensive Review

Abstract

Water pollution from heavy metals, nutrients, dyes, pharmaceuticals, Per- and PolyFluoroAlkyl Substances (PFAS), and pesticides poses serious global challenges, as conventional treatments often fail to remove trace contaminants effectively and produce secondary waste. Biochar, produced by biomass pyrolysis, offers a sustainable environmental carbon material with tunable surface chemistry, porosity, and carbon sequestration potential, making it a promising low-cost alternative to activated carbon. However, pristine biochar requires modification to overcome low surface area, limited functional groups, and poor selectivity for emerging pollutants. This review examines modification methods, adsorption mechanisms (ion exchange, surface complexation, π-π interactions, hydrophobic partitioning), and environmental impacts, including ecotoxicity, leaching risks, and long-term stability. Key findings highlight biochar's versatility across fixed-bed systems, permeable reactive barriers, constructed wetlands, and decentralized treatment, with regeneration strategies enabling reusability. Current challenges include inconsistent preparation standards, limited real wastewater studies, aging mechanisms, performance-safety trade-offs, and scale-up barriers. Future directions emphasize green modifications, multifunctional composites, AI-optimized design, and Advanced Oxidation Processes (AOP) membrane integration for sustainable water management.