Biochar-based adsorption of polycyclic aromatic hydrocarbons in contaminated soils: Advances, mechanisms, and bibliometric analysis

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose significant environmental and health risks due to their toxicity, mutagenicity, and resistance to degradation. Concern over PAHs contamination of soil is on the rise, especially in regions impacted by petrochemical accidents, industrial operations, and the burning of fossil fuels. Adsorption with biochar has become one of the most promising, economical, and environmentally friendly remediation techniques for removing PAHs from polluted soils. This review provides a comprehensive analysis of biochar as an adsorbent for PAHs, focusing on its physicochemical properties, production methods, and adsorption mechanisms. The impact of critical elements on PAH adsorption efficiency is examined, including biochar surface area, functional groups, pyrolysis temperatures, and environmental factors. To improve adsorption efficiency, recent developments in biochar modification techniques, such as functionalisation and the creation of composite materials are also emphasised. The review also examines biochars field-scale applications, contrasts it with other adsorbents, and highlights issues with long-term stability, large-scale deployment, and regulatory concerns. By addressing current knowledge gaps and future research directions, this study aims to support the development of improved biochar-based remediation strategies for PAH-contaminated soils. A bibliometric analysis was conducted to assess research trends on the use of biochar for the adsorption of PAHs in polluted soil. The results revealed a limited number of studies in this area, highlighting the need for further research and innovation.