Green synthesis of lignocellulosic adsorbents for anionic dye removal from aqueous solution: characterization, optimization and kinetics studies

This study aimed to explore the potential of garlic peel as a precursor for producing green adsorbents. Two types of adsorbents from garlic peel (carbonized garlic peel (GP-C) and carbonized garlic peel treated with sodium hydroxide (GP-C-NaOH), were synthesized and evaluated for the removal of anionic dyes from aqueous solutions. Effects of various operational parameters on the adsorption performance, including adsorbent dosage, contact time, initial pH, and dye concentration. Surface morphology analysis revealed that GP-C-NaOH possesses mesoporous characteristics, with a larger average pore volume, pore diameter, and surface area than GP-C. The adsorption experiments demonstrated that GP-C-NaOH has a higher adsorption capacity (72.3 mg/g compared than GP-C (45.7 mg/g) under the optimized conditions. The reusability of GP-C-NaOH was 15% higher than that of GP-C across four adsorption–desorption cycles. This enhanced reusability is attributed to the improved surface morphology, mesoporous structure, and surface chemistry resulting from the NaOH activation. These findings highlight the potential of garlic peel as an eco-friendly precursor to produce effective adsorbents. This study also highlights the feasibility of applying garlic peel-based adsorbents in industrial settings, contributing valuable knowledge to the field.