Waste-derived zeolite from sugarcane bagasse ash and water treatment plant sludge for sustainable industrial dye removal

This study presents a sustainable route for synthesizing zeolites by valorizing two abundant industrial residues: sugarcane bagasse ash and water treatment plant sludge. The synthesized material, primarily composed of sodalite as confirmed by XRD and SEM, was applied for the removal of Acid Red 27 (AR27), a synthetic dye widely used in the food, cosmetics, and household product industries. The adsorption kinetics followed a pseudo-second-order model, suggesting dependence on active site availability, while isotherm analysis indicated multilayer adsorption consistent with the BET model, with an adsorption capacity reaching 250 mg·g^-1. Experiments conducted with competitive anions suggest the adsorption mechanism in the first layer predominantly involved electrostatic interactions; the dye structure suggests π-π stacking for subsequent layers. Coexisting anions, particularly sulfate and bicarbonate, significantly hindered AR27 uptake due to competitive adsorption. Importantly, the adsorbent maintained its performance over three regeneration cycles using a diluted NaOH solution (0.01 M). Compared to granular and powdered activated carbons, the synthesized zeolite exhibited superior performance, especially at medium to high contaminant loads. These findings highlight the potential of waste-derived zeolites as a low-cost, efficient, and environmentally friendly material for wastewater treatment, contributing to circular economy strategies and sustainable resource management.