Adsorption of cationic dye methylene blue onto activated carbon obtained from horse chestnut kernel

Abstract

Horse chestnut kernel was used as the precursor for the preparation of powdered activated carbon using phosphoric acid as the activating agent. Batch adsorption experiments for the adsorption of cationic dye methylene blue from aqueous solutions were carried out using the obtained carbon as adsorbent. Equilibrium and kinetic experiments were conducted. The equilibrium data were fitted with the Langmuir, Freundlich and Temkin theoretical isotherm models. The best results was obtained in the case of Langmuir model, which indicates that monolayer adsorption occurs on finite number of the active adsorption sites on the carbon surface. The kinetic data were fitted with pseudo-first, pseudo-second, Elovich and interparticle diffusion model. Pseudo-second order model and Elovich model showed the best results of the kinetic data. The increasing of the solution pH led to a higher uptake of methylene blue due to the fact that competitive adsorption of methylene blue cation and proton exists in acidic solutions. The adsorption capacity for methylene blue in equilibrium study was significant (168.93 mg g-1). Comparison of the adsorption capacities of methylene blue onto activated carbons derived from various alternative precursors proves chestnut kernel to be efficient and low-cost material which could be substantially deployed in the future.nema