Synthesis and Performance Evaluation of Crosslinked CGN-CMC Blended Hydrogels for Heavy Metal Removal from Aqueous Media

This study reports on a novel carrageenan-carboxymethyl cellulose (CGN-CMC) blended hydrogel synthesized using epichlorohydrin (ECH) as a biodegradable crosslinker. This represents the first reported instance of using ECH as a crosslinker for CGN-CMC blends. The hydrogels were characterized using FTIR, SEM, TGA, DSC, and AFM. Swelling and absorbance under load (AUL) measurements were conducted to evaluate water absorption characteristics. Characterization results revealed that CGN-CMC-ECH hydrogels exhibited a 5% increase in thermal stability, 40% enhancement in surface smoothness, and 45% improvement in water retention capacity compared to the precursor materials. This indicated that ECH led to a more stable and structurally enhanced hydrogel formation. The efficiency of the best-performing CGN-CMC-8ECH blend in removing heavy metal ions from aqueous solutions was evaluated. The influence of initial solution pH and metal ion concentration on adsorption was also investigated. The hydrogel achieved maximum removal efficiencies of 90% for Cu (II), 80% for Pb (II), and 78% for Ni (II). Isotherm analysis indicated multilayer sorption of all metal ions onto the hydrogel surface, aligning with the Freundlich model. The hydrogels showed significant potential as an effective and sustainable adsorbent for heavy metal remediation wastewater treatment applications.