Comparative Study between Locally Synthesized Activated Carbon and Commercial Activated Carbon and their Adsorption Isotherms on Methylene Blue

Abstract

Adsorption using activated carbon (AC) has been proven to be effective in the treatment of wastewater. In this study, Carica papaya seeds were utilized for activated carbon (AC) preparation using zinc chloride as the activating agent. Experiment was carried out to explore the methylene blue uptake by both the Carica papaya seeds activated carbon (CPSAC) and commercial activated carbon (CAC). The physicochemical characteristics, Iodine number and adsorption isotherms of CPSAC were also compared with those of CAC. The adsorption equilibrium was represented with Langmuir and Freundlich isotherm models. The Langmuir isotherm was found to be the best fit for both CPSAC and CAC with the coefficient correlation (R²) values of 0.9922 and 0.9964, respectively. Going by the good fitting of the Langmuir isotherm, MB adsorption on both CPSAC and CAC can be ascribed to be of monolayer adsorption process, and is associated with the chemical functional groups inherent on carbon surface. The optimum adsorption capacities of CPSAC and CAC according to the Langmuir isotherm at approximately 25^◦C were 238.78mg/g and 241.14mg/g, respectively. This implies that CPSAC demonstrated similar outstanding adsorption properties to CAC for MB.