Elimination performance of Nile blue from wastewater using by carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide)/kaolin nanocomposite hydrogel

In this study, we synthesized carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide) copolymer hydrogels and carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide)/kaolin nanocomposite with a free radical mechanism to adsorb pollutants of Nile blue dye. Nanocomposite hydrogels performed best at pH = 11, a temperature of 25 °C, a contact time of 90 min, a concentration of pollutant 10 ppm, and an adsorbent dose of 1.5 mg. The increased adsorption rate of NB dye pollutants after adding kaolin-type clay nanoparticles from 96.49 to 98.91% showed the successful addition of nanoparticles to hydrogel copolymer structures. The best isotherm performance was the Langmuir isotherm model, and maximum adsorption capacity for carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide) copolymer hydrogels and for carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide) nanocomposite hydrogel was 138.49 and 149.82, respectively. In the analysis of kinetic models, Elovich's kinetic model had the best performance, where the α value for carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide) copolymer hydrogels are 0.783 and for carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide)/kaolin nanocomposite hydrogel obtained a value of 9.58, which indicates a high adsorption value. On the other hand, the enthalpy parameters (ΔH°) for adsorption process using carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide) and carboxymethyl cellulose-graft-poly(methacrylic acid-co-acrylamide)/kaolin nanocomposite hydrogels were − 61.512 kJ/mol and − 77.281 kJ/mol, respectively. The negativity of ΔH° indicates that the process is exothermic at 5–50 °C using both adsorbers. Furthermore, this process could be spontaneous because the Gibbs free energy (ΔG°) for adsorption processes was negative in experiment temperature range.