Sustainable dye removal from industrial wastewater using marine algae-derived biosorbents and MOF-based hybrid composites

This study presents a comparative investigation of marine algal biomasses (fresh and dried) and a zirconium-based metal-organic framework (UiO-66-NH₂) for the removal of reactive dyes from industrial wastewater. Three widely used textile dyes Reactive Yellow 2 (RY2), Reactive Red 195 (RR195), and Reactive Blue 19 (RB19) were selected as model pollutants. Adsorption experiments were conducted under unified experimental conditions to evaluate the effects of initial dye concentration, solution pH, adsorbent dosage, and contact time. Control experiments at acidic pH confirmed that dye removal occurred predominantly via adsorption rather than precipitation. Adsorption kinetics and equilibrium behaviour were analysed using kinetic models and Langmuir and Freundlich isotherms. The results demonstrated that dried algal biomass exhibited significantly higher removal efficiencies compared to fresh biomass, reaching up to 96% dye removal, due to enhanced surface area and availability of active functional groups. UiO-66-NH₂ showed high adsorption capacity and stability, particularly under acidic conditions, owing to strong electrostatic interactions, hydrogen bonding, and π-π stacking. Comparative analysis highlights the advantages and limitations of low-cost marine algal biosorbents relative to advance MOF materials. Overall, the findings provide valuable insight into sustainable, efficient, and scalable strategies for the treatment of dye-contaminated industrial wastewater.