Applications and challenges of modified algal biochar in environmental remediation

Algal biochar has demonstrated substantial potential in environmental remediation, attributed to its porous architecture, diverse functional groups, and eco-friendly characteristics. However, its unmodified form has certain limitations regarding adsorption capacity, pollutant selectivity, and stability. Advanced modification strategies—including acid/base activation, metal impregnation, and functional group engineering—have been proven to significantly improve its adsorption performance for pollutants such as heavy metals, persistent organic pollutants, or nutrients through mechanisms involving surface complexation, ion exchange, and chemical precipitation. These engineered modifications also improve mechanical strength and chemical resistance, effectively reducing the risks of biochar fragmentation and secondary contamination. Despite the recent advancements in modified algal biochar, challenges remain in large-scale production, long-term stability, and cost-effectiveness. This review systematically examines (1) state-of-the-art modification methodologies, (2) contaminant removal mechanisms under varying environmental conditions, and (3) the technological obstacles hindering practical implementation. These insights contribute to a deeper understanding of the structure-function relationships in engineered biochar systems and offer practical guidelines for optimizing remediation technologies.