Abstract
In this study, methylene blue (MB) dye was removed by adsorption onto dimethyglyoxime modified amberlite IRA-420 (DMG-AMB) beads from aqueous medium. The adsorption data fitted well to kinetic, equilibrium, and thermodynamic models. Equilibrium was reached after only 8 h. The removal percentage increased from around 13.3% to 22.5% with increasing MB concentrations from 2.0 to 8.0 (mg/L), where the adsorbent capacity increased linearly. The analysis of the kinetic data indicated that the adsorption was a second-order process. The Freundlich isotherm model described well the adsorption process. The maximum adsorption capacity, determined from the Langmuir isotherm, was 0.161 mg/g. Moreover, the diffusion mechanism of MB was described by different removal-diffusion models. The film diffusion was found as the rate-limiting process. The pH of the adsorption process was studied; it indicated a determined effect with an exponential increase in the adsorption capacity and removal percentage due to increase in pH from 8.0 to 11.5. A positive impact of the increment in the adsorption temperature was observed for temperature range between 25 degrees C and 60 degrees C. The thermodynamic nature of the process was extracted using Van't Hoff plot. The positive value for the Delta H degrees (29.69 kJ/mol) indicates the endothermic nature of the process, which explains the increase of the MB cations adsorption efficiency as the temperature increased.