Engineering functional carbon materials via algae–plastic co-pyrolysis for wastewater treatment: Mechanisms, adsorption performance, and design strategies

The present review critically analyses the thermochemical platform of algae–plastic co-pyrolysis to produce high-performance functional carbon materials for environmental applications. Co-pyrolysis takes advantage of synergistic effects, such as hydrogen transfer, radical stabilization, and mineral catalysis, to achieve higher carbon yield, heteroatom doping, pore development, and structural stability than single-feed pyrolysis. The reported surface area of co-pyrolysis-derived carbon materials are about 300–800 m² g^−1, and adsorption capacities are 100–500 mg g⁻¹, which are superior to several chars made from algae and plastic. The effects of feedstock composition, blending ratio, heating rate, and reactor configuration on material properties and performance are systematically investigated. Special attention is given to the relationships between structure–property–performance, surface functionality, hierarchical porosity, graphitization degree, and adsorption behavior. Heavy metal, dye, pharmaceutical, and emerging contaminants adsorption mechanisms such as physical adsorption, ion exchange, electrostatic interactions, and surface complexation are discussed. Issues of the variability of feedstocks, emission control, regeneration, scale-up, and life-cycle sustainability are also brought into critical focus. Algae–plastic co-pyrolysis is a potential circular economy technology for converting waste streams into value-added carbon materials that can be utilized for advanced wastewater treatment, as well as for other environmental applications.