Kinetic and equilibrium study of methylene blue adsorption using H2SO4-activated rice husk ash

Abstract

The objective of this study is to evaluate the performance of H2SO4-activated rice husk ash (ARHA) (burned at different temperatures (300-550 degrees C) as compared to granular activated carbon (GAC) in the removal of methylene blue (MB) from aqueous solution. Batch studies were performed to evaluate the influences of various experimental parameters like pH (4, 7, 9, and 11), initial concentration (5, 10, 15, 20, 25, and 50 mg/L), and contact time (0, 1, 5, 15, 30, 45, 60, 90, and 120 min). BET surface areas for ARHA300 (burned at 300 degrees C) and ARHA550 (burned at 550 degrees C) were determined as 143 and 68 m(2)/g, respectively. It was observed that the dye uptake by GAC and ARHA300 were not changed significantly when the pH of dye solution was increased from 4 to 11. Uptakes of dye were rapid and the adsorption increased with increasing contact time in all experiments. According to the R-2 values for the adsorption of MB on ARHA300, ARHA500, and GAC, Langmuir model yields fit better than the Freundlich model. The maximum adsorption capacity, q(max) of ARHA300 (44.25 mg/g), had the highest value. The pseudo-second-order kinetic model yields the best fit for adsorption on ARHA300 and ARHA550 and the correlation coefficients R-2 of the model for the linear plots are very close to 1 at various concentrations.