Efficient adsorption of crystal violet by different temperature pyrolyzed biochar-based sodium alginate microspheres: A green solution for food industry dye removal

This study developed composite microspheres from orange peel biochar pyrolyzed by 300 °C-900 °C and sodium alginate to address the removal of crystal violet (CV). Biochar was pyrolyzed at different temperatures, and biochar pyrolyzed at 800 °C (B800) based‑sodium alginate microspheres (BS800) showed the highest adsorption performance, in which, the specific surface area and pore size of B800 was 387.47 m²/g and 1.66 nm, respectively. Adsorption was primarily driven by chemical mechanisms, as confirmed by kinetic and isothermal models, while thermodynamic analysis revealed the process to be spontaneous and endothermic. BS800 demonstrated excellent stability with a low CV release risk (<0.6 %) and regeneration ability (>85 %) of its adsorption efficiency after five cycles. These findings highlight the application potential of BS800 for the safe and effective removal of CV in food and aquatic product processing, offering a sustainable solution via the utilization of agricultural waste.