Recent advances in biochar technology for aquatic pollution control: a critical review of applications, barriers, and future opportunities

Abstract Biochar has emerged as a promising, low-cost, and eco-friendly material for wastewater treatment due to its high surface area, porosity, and functional group diversity, which enable efficient adsorption of a wide range of contaminants. While several studies have explored the use of biochar in pollutant removal, a comprehensive synthesis that integrates its multifunctional roles, recent technological advancements, and future scalability challenges remains limited. This review uniquely addresses this gap by providing a critical and up-to-date assessment of biochar’s application for removing pharmaceuticals, microplastics, heavy metals, organic pollutants, and nutrients from aquatic systems. In contrast to previous reviews, this study emphasizes the innovative modification techniques—such as activation, functionalization, and composite synthesis—that enhances biochar's performance, and evaluates its integration with emerging technologies, including nanomaterials and hybrid filtration systems. Furthermore, we incorporate a bibliometric analysis of Scopus-indexed literature (2010–2025) to identify evolving research trends, leading contributors, and existing knowledge gaps in the field. Current findings indicate that biochar can achieve pollutant removal efficiencies of up to 80%, with notable performance in nutrient removal (71% for ammonium-nitrogen and 57% for phosphate-phosphorus) and pathogen reduction (2.4 log 10 units). However, its large-scale application is still constrained by limitations in regeneration efficiency, cost-effectiveness, and scalability. By offering an integrated review of scientific innovations, field applicability, and sustainability considerations, this paper provides new insights and a forward-looking perspective on transforming biochar into a practical, scalable solution for wastewater remediation. Graphical abstract