Adsorption of Methylene Blue by a Carboxymethyl Cellulose-Guar Gum Adsorbent: Freundlich and Langmuir Isotherm Analysis

Abstract

A carboxymethyl cellulose-guar gum (CMC-GG) adsorbent cross-linked with aluminum sulfate octadecahydrate and boric acid was evaluated for methylene blue (MB) adsorption. The study determined the adsorption equilibrium time, adsorption capacity at different MB concentrations, and the isotherm model that best described the adsorption process. The adsorbent was characterized by water absorption capacity (WAC), degree of cross-linking, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Contact times of 15, 30, 45, 60, and 75 min were examined, and equilibrium was reached at 45 min. Adsorption experiments were then conducted at initial MB concentrations of 20, 40, 60, 80, and 100 mg/L. The corresponding adsorption capacities were 3.7017, 7.4113, 10.9718, 14.9653, and 18.6531 mg/g. The adsorption capacity increased with the initial MB concentration. Isotherm analysis showed that the Langmuir model provided the best fit, with R² = 0.9912 and a calculated maximum adsorption capacity of 158.73 mg/g. These results indicate that the CMC-GG-Al-BA adsorbent has potential for the adsorption of cationic methylene blue from aqueous solution.