Kinetics, statics and thermodynamics of ampicillin adsorption on microporous carbon sorbents

Adsorption is one of the processes that effectively removes many organic contaminants. The study analyzes the influence of activated carbon type and of process conditions (pH and temperature) on the efficiency of ampicillin adsorption. Six commercial microporous activated carbons were used and it turned out that ampicillin is best removed by the WG-12 carbon featuring the largest specific surface area. Based on the value of the Pearson correlation coefficient, it was found that there is a very strong positive correlation between the specific surface area and the ampicillin adsorption efficiency. The following models were used to describe the adsorption kinetics: pseudo-first order; pseudo-second order; Elovich and intraparticle diffusion model; the models of Freundlich, Langmuir, Temkin, Javanovic and Halsey; and three-parameter models of Redlich-Peterson and Thot. The highest values of the correlation coefficient R2 were obtained for the Eloch kinetics model and the Thot, Jovanovic and Tempkin isotherms. The free energy of adsorption, entropy and enthalpy were also determined. It was found that ampicillin adsorption occurs mainly due to physical interactions, it is single-layered, beneficial, spontaneous, exothermic. The highest values of adsorption capacity were obtained for the pH 6, 293 K solution.