Upcycling olive and crab wastes into biochar for histamine treatment in fishery wastewater

This study investigates a hybrid adsorption–solar photocatalysis process for the treatment of real fishery wastewater using biochars derived from olive pomace (OP) and blue crab shells (BC). The biochars were synthesized and characterized using SEM, TGA–dTG, and XRD analyses. Adsorption experiments were conducted under dark and solar irradiation conditions, and the process was optimized using a Box–Behnken Design statistically validated by ANOVA (p < 0.05). Under optimal conditions (natural pH 8.6, contact time of 80 min, and initial histamine concentration of 60 mg/L), histamine removal efficiencies reached approximately 88% for OP biochar and up to 99% for BC biochar under solar irradiation, highlighting the synergistic effect of adsorption and photocatalysis. Kinetic and isotherm analyses revealed adsorption governed mainly by physisorption for OP, while BC exhibited enhanced chemisorption and photo-assisted degradation. The optimized process was further adapted to continuous operation and simulated using Aspen HYSYS, predicting overall pollutant removal efficiencies exceeding 85% for most contaminants. These results confirm the effectiveness and scalability of this low-cost, solar-assisted hybrid treatment strategy for fisheries wastewater. • Process optimized using Box-Behnken Design and ANOVA validation • Hybrid photo-adsorption treats real fishery wastewater effectively • Olive and crab biochars remove histamine up to 94% under sunlight • Langmuir (BC) and Freundlich (OP) models fit isothermal behaviors • Aspen HYSYS model predicts >85% pollutant removal in continuous mode