Optimization of pomegranate peel-enriched chitosan oligosaccharide nanocrystalline cellulose grafted polyacrylamide hydrogel for heavy metal copper and chromium removal: a sustainable solution for wastewater treatment

Abstract

This study optimises a pomegranate peel-enriched chitosan oligosaccharide nanocrystalline cellulose grafted polyacrylamide hydrogel (CS-NCC-g-AM/PP-MBA) for the removal of wastewater containing the heavy metals copper and chromium. The hydrogel was synthesised through grafting and characterised for its adsorption capacity. Batch adsorption studies evaluated the removal efficiency, achieving over 80% removal for both Cu(II) and Cr(VI) ions. The significant adsorption capacity was ascribed to the functional groups from the pomegranate peel, chitosan oligosaccharide, and nanocrystalline cellulose in the hydrogel matrix. The hydrogel demonstrated excellent hydrophilicity, viscoelasticity, and reusability, making it a viable, economical, and environmentally friendly adsorbent for the removal of heavy metals. The study highlights the potential of utilising agricultural waste products in developing sustainable solutions for addressing heavy metal contamination in water. The prepared hydrogel proved the maximum adsorption capacity, C_max- 229.37 mg/g for copper and 206.33 mg/g for chromium following Freundlich isotherm. The adsorption followed pseudo-second order kinetics with R²—0.9993 for copper and R²—0.9982 for chromium. The best results were obtained when the pH of the medium was maintained at 5 and adsorbent dose 4gm.The findings contribute to the advancement of green technologies for wastewater treatment, as the hydrogel’s unique three-dimensional porous architecture, hydrophilicity, and functional groups (− COOH, − NH₂, − SO₃H, and − OH) enable effective adsorption of metal ions. The optimization of this pomegranate peel-based hydrogel offers a novel approach to tackling the global challenge of heavy metal pollution in water resources.

Graphical abstract