Microalgae-derived biochar for microplastic removal from aquatic systems: A comprehensive review and future perspectives

Microplastics (MPs) have emerged as a prevailing contaminant in aquatic environments, posing ecological risks and potential threats to human health due to their persistence and toxicity. Conventional remediation approaches are often constrained by high costs, limited efficiency and risk of secondary pollution. Recently, microalgae-derived (MD) biochar has gained attention as a sustainable and effective adsorbent for MP removal, with studies reporting removal efficiencies ranging from 60 % to 99 %, depending on MP type, size, surface chemistry, and operational conditions. Its high surface reactivity, cost-effectiveness and environmental compatibility make MD-biochar a promising alternative to conventional adsorbents. This review evaluates the potential of MD biochar in MP remediation, emphasizing how physicochemical properties such as porosity, functional groups and surface charge govern adsorption performance. Various microalgal species, such as Chlorella and Spirulina , have been explored as biochar precursors, offering unique structural and chemical properties that enhance MP removal. Production conditions, particularly pyrolysis temperature (450–750℃) and activation strategies, strongly influence biochar functionality. The mechanisms of MP adsorption, involving electrostatic attraction, hydrophobic partitioning and π-π interactions, are thoroughly discussed. Additionally, the review emphasizes the benefits of utilizing MD-biochar compared to conventional adsorbents, its ability to be regenerated and its ecological sustainability. Issues such as scalability, variations in MP composition are also discussed. Further studies should concentrate on defining common parameters, run pilot trials in diverse water matrices, integrating emerging tools such as AI-ML, carry out cost-benefit studies and stakeholder engagement.