Sustainable water remediation with algae-derived adsorbents: from synthesis strategies to adsorption performance and mechanisms

Human-driven activities related to diverse industries such as textiles, pharmaceuticals, plastics, leather, and agriculture contribute significantly to the discharge of pollutants into aquatic environments, thereby threatening the ecological balance and posing a risk to living organisms. Over the past few years, algae have been acknowledged as a cost-effective and sustainable resource for the detoxification of harmful pollutants, primarily through mechanisms such as intracellular biodegradation, bioaccumulation, and biosorption. Besides the direct involvement of algae in the removal of pollutants, they can be converted into carbon-rich materials such as hydrochar, biochar, and activated carbon. These materials possess high specific surface areas and different functional groups, which make them quite effective for the adsorption of organic pollutants in wastewater treatment. Algal-derived adsorbents exhibit high adsorption efficiency because of the synergistic effects of various interactions, including electrostatic forces, hydrogen bonding, π-π interactions, and pore filling effects, all of which depend on the engineered surface functional groups and porous structure of algae-derived carbon-rich materials. This review uniquely explores various algal species for the preparation of adsorbents and also examines the modification methods used to convert algae into adsorbents. It examines their effectiveness in the removal of organic contaminants from water systems. Future research needs to bridge the gap between laboratory-scale and real-world applications, especially through pilot-scale studies in real wastewater and comprehensive life-cycle assessments.