Statistical analysis of equilibrium and kinetic data for ascorbic acid removal from aqueous solution by activated carbon

Abstract

The adsorption of ascorbic acid from aqueous solution onto activated carbon was investigated at different concentrations and temperatures. Equilibrium data were analysed using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), Temkin and Frumkin isotherms. All of the isotherm parameters were calculated and showed that they were well explained by the Langmuir, Temkin and Frumkin isotherms models, as compared with the D–R and Freundlich isotherms. Maximum adsorption capacity was determined to be 520.80 mg g⁻¹ according to the Langmuir isotherm. The mean free energy values (E) according to the D–R isotherm were estimated to be 12.50 kJ mol⁻¹. In order to clarify the adsorption kinetics, the fits of pseudo-first-order kinetics second-order kinetics, and Elovich models were compared. It was determined that the ascorbic acid adsorption process followed pseudo-second-order rate kinetics. Kinetic and equilibrium data were evaluated according to standard deviation and correlation coefficients. The external mass transfer coefficient, as well as the film and pore diffusion coefficients were also evaluated at various temperatures.

Keywords:

• Ascorbic acid
• Adsorption
• Activated carbon
• Mass transfer