Highly Reusable Nano Adsorbent Based on Clay-Incorporated Hydrogel Nanocomposite for Cationic Dye Adsorption

In this study, a novel hydrogel nanocomposite based on carboxymethyl cellulose (CMC) polysaccharide was fabricated by graft free radical co-polymerization of Itaconic acid and acrylamide monomers in the presence of Palygorskite clay. The nanocomposite, known as CMC-g-poly(AM-co-ITA)/Clay, was synthesized using potassium persulfate (KPS) as the initiator and N, N′-methylene bisacrylamide (MBA) as the cross-linker. The goal was to create nano adsorbents with excellent adsorption capacity, easy separation, selectivity, and superior reusability for eliminating dyes from aqueous solutions. The nanocomposite’s structure was analyzed using various techniques including FTIR, XRD, HRTEM, FESEM, TGA, and BET. The study of the nanocomposite’s thermal stability revealed that the one with 15% clay exhibited the best thermal stability. FESEM images showed a high cross-linking density and a porous surface, facilitating water diffusion and affecting the swelling behavior. The nanocomposites’ gel content and swelling behavior were compared with those of a hydrogel without clay when placed in water. The results indicated that as the clay content increased, the swelling ratio decreased while the gel content increased. The CMC-g-poly (AM-co-ITA)/Clay nanocomposite was found to have high stability in an aqueous solution and a negatively charged surface at a pH higher than 3.1. The findings indicated that adding clay to the hydrogel improved its ability to remove Brilliant Green from water. Introducing 15% clay into the hydrogel raised its maximum adsorption capacity for BG dye removal from 199.67 to 1513.55 mg/g. Various models were used to analyze the experimental results, with the pseudo-second-order demonstrating the best fit for the kinetic model. Equilibrium data were assessed using Langmuir, Freundlich, and Temkin isotherm models. The Freundlich model was found to best describe the uptake of BG dye, suggesting heterogeneous multilayer adsorption onto the nanocomposite. Thermodynamic parameters indicated that the adsorption of BG dye onto the nanocomposite was endothermic (ΔH > 0) and spontaneous (ΔG < 0). Additionally, the nanocomposite showed high reusability and easy separation, maintaining an 88.23% removal capacity for BG dye after 6 cycles.