Sustainable dye removal from textile wastewater using modified agricultural waste: sugarcane bagasse as an adsorbent

This study explores the sustainable valorization of sugarcane bagasse (Saccharum officinarum), an abundant lignocellulosic agro-waste, as an eco-friendly adsorbent for the removal of synthetic azo dyes from aqueous environments. Both raw and acetic acid-modified bagasse were prepared using varying concentrations (5%, 10%, 15%, and 20%) to enhance surface functionality. Comprehensive characterization using FTIR, SEM, XRD, and point of zero charge analysis elucidated the physicochemical changes induced by acid treatment. Adsorption studies targeting reactive blue, a representative anionic dye commonly found in textile effluents, were conducted under varying operational parameters, including dye concentration, adsorbent dose, contact time, pH, and temperature. The 15% acetic acid-modified bagasse demonstrated superior adsorption efficiency, achieving 75.80% dye removal at neutral pH and 98.45% under acidic conditions (pH 2) for an initial dye concentration of 5 mg L−1. Kinetic data followed a pseudo-second-order model, suggesting chemisorption as the dominant mechanism, while equilibrium data were best described by the Freundlich isotherm, indicating multilayer adsorption on a heterogeneous surface. The process was found to be more effective at lower temperatures, highlighting its feasibility for low-energy wastewater treatment applications. This work supports the circular use of agricultural residues in green remediation strategies for industrial dye pollution.