Adsorptive Removal of Methylene Blue from Aqueous Solution by the Activated Carbon Obtained from the Fruit of Catalpa bignonioides

Abstract

In this study, the fruit of Catalpa bignonioides was used as the raw material to obtain low-cost activated carbon. The activation process was carried out by using chemical activation method with zinc chloride. Catalpa activated carbon (CAC) was characterized using elemental analyzer, Brunauer-Emmet-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectra (FTIR), and the point of zero charge (pHZPC). The BET surface area of CAC prepared by the impregnation ratio of 30% ZnCl2 (w/w) was found to be 896.02 m(2)/g. The efficiency in the process of the removal of methylene blue (MB) from aqueous solution by CAC was searched with different factors, such as temperature, pH, adsorbent concentration, dye concentration, and contact time. From the experimental data obtained, the studies related to adsorption isotherm, kinetics, and thermodynamics were performed. Langmuir model provided the best fit, and the adsorption capacity for the removal of methylene blue from aqueous solution by CAC was calculated to be 271.00 mg/g at 25 degrees C. The adsorption follows a pseudo-second-order kinetic model. Moreover, the thermodynamic parameters such as Delta G degrees, Delta H degrees, and Delta S degrees presented that the adsorption was spontaneous and endothermic.