Doped Biopolymer Composites for Engineered Water Purification: Mechanistic Insights into Multi-Ion Adsorption

The presence of heavy metals and fluorides (F^-) in wastewater poses serious environmental and public health challenges. Therefore, in this study, curcumin-doped chitosan-activated carbon (CsAC) biopolymer composites were synthesized and evaluated for the removal of As-(III), Cr-(VI), and F^- ions. The composite containing 5% curcumin (CsACCur5%) exhibited superior adsorption performance, while comprehensive characterization using BET, SEM, FT-IR, XPS, and XRD confirmed successful curcumin incorporation and effective contaminant adsorption. Moreover, CsACCur5% exhibited >95% removal of Cr-(VI) across a wide pH range and 75.8% and 71.8% removal of As-(III) and F^-, respectively, using 0.5 g/L at pH 5. This composite can remove up to 21.81 mg/g Cr-(VI), 0.88 mg/g As-(III), and 44.8 mg/g F^- under optimal conditions. Profound adsorption analyses through three kinetic models and ten isotherm models indicated endothermic and spontaneous adsorption mechanisms. Furthermore, swelling and stability assessments demonstrated reduced hydrophilicity and high reusability, maintaining performance through ten regeneration cycles. Overall, the use of olive-stone-derived AC combined with chitosan and curcumin biomaterials promotes sustainability, resulting in enhanced adsorption efficiency and structural stability of CsACCur, underscoring its potential for sustainable wastewater treatment.