Simultaneous elimination of cationic dyes from water media by carboxymethyl cellulose-graft-poly(acrylamide)/magnetic biochar nanocomposite hydrogel adsorbent

In this work, the grafting of acrylamide onto CMC was performed by a free radical polymerization method to prepare hydrogel for the elimination of single and simultaneous methylene blue (MB) and methyl violet (MV) -as common textural dyes-from water. Biochar (CL) and magnetic biochar of Luffa Cylindrica (CL-Fe₃O₄) were integrated into the hydrogel matrix to promote removal performance. CL was prepared using the pyrolysis method and modified using Fe₃O₄ magnetic nanoparticles by a co-precipitation method. Infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibration sample magnetometry (VSM) analysis were applied to characterize prepared adsorbents. The maximum removal of single MB and MV occurred at a pH of 9, temperature of 25 °C, adsorbent dose of 1.5 g/L, initial concentration of 10 mg/L, and contact time of 60 min. The maximum removal efficiency under the optimal conditions was determined to be 83.11, 92.89 and 95.01% for single adsorption of MB, 76.09, 85.91 and 90.11% for single adsorption of MV, 66.96, 76.48 and 80.02% for simultaneous adsorption of MB and 60.04, 69.91 and 75.28% for simultaneous adsorption of MV by CMC-g-poly(AAm), CMC-g-poly(AAm)/CL, and CMC-g-poly(AAm)/CL-Fe₃O₄, respectively. The kinetic and isotherm studies revealed that the pseudo-second-order kinetic model and the Langmuir isotherm model aligned more with the experimental data. Thermodynamic studies showed that the adsorption of dyes takes place spontaneously and exothermically. Therefore, CMC-g-poly(AAm)/CL-Fe₃O₄ nanocomposite hydrogel could be used for wastewater treatment applications.