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One of the major environmental problems is the entry of colored pollutants into the oceans and seas. Adsorption is one of the effective methods to eliminate colorant polluting materials from wastewater streams. In this study, nanocomposite hydrogels of poly(methacrylic acid-co-acrylamide) (Poly(MAA-co-AAm)) containing different weight percent bentonite clay nanoparticles (0, 5, 10, and 15 wt. %) were used to remove methyl violet (MV) dye. FTIR, SEM, TGA, and XRD were used to analyze the properties of adsorbents. Results showed that bentonite nanoparticles were successfully distributed in the hydrogel system. Bentonite nanoparticles at 10 wt. % gave the maximum MV dye adsorption efficiency. The highest adsorption was obtained at a pH of 5, an adsorbent dosage of 1.5 g/L, a temperature of 25°C, a contact time of 60 min, and a pollutant concentration of 10 mg/L. In thermodynamics studies, a negative values of Gibbs free energy (ΔG°) indicating that the adsorption process was spontaneous. In addition, Poly(MAA-co-AAm) hydrogels and Poly(MAA-co-AAm)/bentonite nanocomposite hydrogels gave the adsorption enthalpy (ΔH°) of 22.2 and 47.4 KJ/mol. Langmuir isotherm model was successfully applied in describing the equilibrium behavior of the adsorption process. To investigate the adsorption kinetics, we used pseudofirst-order, pseudo-second-order, and Elovich models. The kinetic study showed that the pseudo-secondorder model was more successful in describing the kinetic behavior of the adsorption process than pseudofirst-order and Elovich models. Incorporating bentonite clay nanoparticles in Poly(MAA-co-AAm) nanocomposite hydrogels significantly improved the adsorption and swelling efficiencies of these hydrogels.

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