Preparation of carboxymethyl cellulose-based silica hydrogel nanocomposite for methylene blue and malachite green dyes adsorption from aqueous solution
Edwin Makhado
Abstract
In this study, carboxymethyl cellulose/acrylic acid/acrylamide/SiO 2 nanospheres (CMC/AA/AAm/SiO 2 ) hydrogel nanocomposite was synthesised using the free radical polymerization technique. The morphological and structural characteristics of the prepared hydrogel nanocomposites were studied and analysed using various techniques, including FTIR, XRD, TGA, BET, SEM, and TEM. The prepared materials' mechanical properties were assessed using DMA, while their ability to expand in an aqueous environment was tested using gravimetric measurements. The CMC/AA/AAm/SiO 2 hydrogel nanocomposites were employed as an adsorbent in batch experiments to remove methylene blue (MB) and malachite green (MG) dyes from aqueous solutions. The investigation evaluated and enhanced the influence of several parameters on the adsorption of dye pollutants, such as the pH of the solution (2 to 10), the contact time (15 to 90 min), the initial concentration (100 to 600 mg/L), and the temperature (298.15 to 318.15 K). The pseudo-second-order model best described the experimental data, whereas the Dubinin-Radushkevich model was the best fit for isotherm models. According to the Langmuir isotherm model the hydrogel nanocomposites have shown a maximum adsorption capacity of 752.9 mg/g for MB and 906.3 mg/g for MG. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic between the adsorbent and both MB and MG dye molecules. Furthermore, the investigations on reusability demonstrated that the adsorbent maintained its high adsorption capability for both MG and MB dyes even after six cycles. Therefore, the hydrogel nanocomposites that have been created may be regarded as efficient adsorbents for removing organic dyes from wastewater.