Optimization of chitosan/polyvinyl alcohol/lemongrass hydrochar composite beads for the removal of azo dyes in water

Abstract

This study explores the potential of chitosan (CS)/polyvinyl alcohol (PVA)/lemongrass hydrochar (LGHC) composite beads as efficient adsorbents for azo dye removal for the first time, demonstrating their high efficacy and sustainability. Unlike conventional adsorbents, these composite beads incorporate LGHC, a low-cost, renewable biomass-derived material, and sustainable polymers (CS and PVA), offering an eco-friendly and cost-effective alternative for industrial dye removal. The optimal composition of the composite beads was determined to be 2.00 wt% CS, 862.70 ppm LGHC, and 0.50 wt% PVA, achieving impressive sorption capacities of 22.30 mg/g for methyl orange, 57.73 mg/g for congo red, and 74.20 mg/g for methyl red. The composite beads featured a porous structure, and a composition enriched with carbon, oxygen, and nitrogen, facilitating dye removal through electrostatic interactions, hydrogen bonding, and π-π stacking. While their sorption capacities are comparable to conventional adsorbents, the incorporation of biomass-derived hydrochar and sustainable polymers enhances their environmental viability. This study underscores the potential of CS/PVA/LGHC composite beads as a scalable, eco-friendly solution for mitigating industrial dye pollution, contributing to cleaner water systems and greater environmental sustainability.