Enhanced Azo Dye Removal via Alginate-Immobilized Ganoderma lucidum: From Batch Experiments to Continuous Column Studies

In this study, Ganoderma lucidum biomass and alginate-immobilized G. lucidum microbeads were compared for the removal of the azo dye Direct Blue 9 (DB9) from aqueous solutions. While raw fungal biomass has been widely studied as a biosorbent, its practical application is limited by poor mechanical stability and reusability. To overcome these limitations, biomass was immobilized via alginate microencapsulation, and its performance was systematically compared with free biomass. The effects of pH, temperature, initial DB9 concentration, and contact time were optimized for both systems. The immobilized microbeads exhibited a significantly higher removal efficiency (99.54 ± 0.76%) than free biomass (93.31 ± 0.05%), indicating a positive effect of immobilization on biosorption performance. Equilibrium data were best described by the Freundlich isotherm model, suggesting heterogeneous surface interactions, while thermodynamic analysis confirmed that the process was exothermic and occurred spontaneously. Reusability tests were performed, and the microbeads maintained high removal efficiency across multiple cycles with ethanol as the desorption agent, highlighting their operational stability. Furthermore, continuous column studies confirmed the applicability of immobilized biosorbents under dynamic conditions, demonstrating their potential for scale-up. Results indicate that alginate-immobilized G. lucidum microbeads provide an efficient and practical alternative to free biomass for dye removal in wastewater treatment systems.