Rice Straw-Derived Activated Carbon/PNIPAM Nanocomposite Hydrogel for Efficient Adsorptive Removal of Synthetic Dyes

The persistent discharge of synthetic dyes into water bodies presents a critical environmental challenge due to their toxicity, nonbiodegradability, and persistent pollution. This study explores an eco-friendly approach to dye remediation using a nanocomposite hydrogel synthesized from rice straw-derived activated carbon (AC) embedded within a poly(N-isopropylacrylamide) (PNIPAM) matrix. Rice straw, an abundant agricultural waste, is converted into AC through pyrolysis followed by KOH activation, yielding a porous, graphitic-like structure with high surface functionality and characterized using FT-IR, powder X-ray diffraction analysis, Raman spectroscopy, FESEM, and HRTEM. The PNIPAM/AC nanocomposite hydrogel is synthesized via free-radical polymerization. The nanocomposite demonstrates high adsorption efficiency for congo red (anionic) is 94% and for rhodamine B (cationic) it is 71%, attributed to strong π–π interactions, electrostatic attraction, and enhanced diffusion through the hydrogel network. The material is a sustainable and cost-effective solution for industrial wastewater treatment.