iota‐Carrageenan/Psyllium Composite Hydrogel for Cationic and Anionic Dye Removal From Wastewater

ABSTRACT This study presents the in‐air synthesis of a novel hydrogel through chemical crosslinking of iota‐carrageenan (ι‐CG) and psyllium (PSY) using epichlorohydrin (EPH) as the crosslinking agent, aimed at the efficient removal of the dyes Crystal Violet (CV) and Fuchsin Acid (FA). The optimized hydrogel formulation, synthesized at 60°C for 5 h with a 1:1 ι‐CG:PSY ratio, 10 mL solvent volume, 0.6 mL EPH, and an alkaline pH of 9, demonstrated a remarkable swelling ratio of 3851% under the optimized synthesis conditions. Comprehensive physicochemical characterizations were performed using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X‐ray Spectroscopy (EDX), and Powder X‐ray Diffraction (PXRD) to confirm structural integrity and surface morphology. Batch adsorption studies revealed high dye removal efficiencies of 97.6% for CV and 94.5% for FA. Kinetic modelling showed that FA adsorption followed a pseudo‐first‐order model, while CV adsorption followed a pseudo‐second‐order model, suggesting different rate‐limiting mechanisms. Additionally, negative Gibbs free energy (ΔG°) values confirmed the spontaneous and thermodynamically favorable adsorption process. These findings highlight the potential of the ι‐CG/PSY hydrogel as a sustainable and efficient adsorbent for wastewater treatment applications.