Synthesis of granular algal-biomass-based catalysts for enhanced ozonation of wastewater

Catalysts are crucial for the catalytic ozonation treatment of refractory industrial wastewater. While carbon-based catalysts are considered as promising alternatives to metal-based ones, their practical application is severely hindered by costly heteroatom doping (e.g., N, P) and difficulty in separating and reusing their predominant powder forms. Algal biomass is a promising raw material for carbon-based catalyst, given its inherent nitrogen and phosphorus content, and wide availability from diverse sources such as algal bloom waste or industrial algal residues. Here, we report a novel strategy to synthesize granular carbon-alumina composite catalysts directly from algal biomass. The granular catalysts were fabricated via a single-step process involving mixing algae biomass with alumina, granulation, and thermal treatment in an inert atmosphere, which simultaneously induced the pyrolysis of algae and the sintering of alumina. The resulting granular catalyst exhibited excellent performance in catalytic ozonation, achieving removal rate of 97.3% for oxalic acid in synthetic wastewater, and 63.9% for COD in actual hypersaline industrial wastewater. This study provides a feasible technical pathway for fabricating granular algal-biomass-based catalysts, advancing the research and application of novel green algal-derived materials in catalytic ozonation. • Granular catalysts are synthesized directly from algal biomass. • Algal biomass serves as cost-effectiveness carbon source with high reactivity and carbon efficiency. • Simultaneously biomass pyrolysis and alumina sintering are achieved in a single thermal treatment. • The catalyst exhibited high efficiency in catalytic ozonation of synthetic and real wastewater. • This strategy offers a sustainable route to valorize algal biomass into functional materials.