Removal of Pemetrexed from aqueous phase using activated carbons in static mode

Abstract

Three activated carbons (ACs) obtained from wood and activated either by steam (AC1) or phosphoric acid (AC2, AC3) were characterized via nitrogen adsorption–desorption isotherms, zeta potentials, infrared and Raman spectroscopy, as well as their chemical analysis was determined. Adsorption experiments with Pemetrexed (PEME), a pharmaceutical used for the treatment of tumors, were carried out in which adsorbent doses, contact times, temperatures, and solution pH were investigated. Correlation between the physicochemical properties of ACs and the adsorption capacity was proposed. According to the results, it was found that AC1 and AC3 were better described by the Freundlich and Langmuir models, respectively, whereas both models could be used to fit the adsorptive isotherm of AC2. The higher the initial PEME concentration or the temperature, the higher the adsorption capacity was. The adsorption capacities of the adsorbents were in the following order, AC3 > AC2 > AC1, in agreement with their specific surface areas. A coexistence process of physical and chemical adsorption existed in all ACs as predicted by the best fitting obtained with the Dubinin–Radushkevich, pseudo–second–order kinetic and Elovich models. The adsorption mechanisms were researched using the Conductor–like Screening Model methodology to determine the proton donor and acceptor centres in PEME. As main conclusion, supported by DRIFTS analysis and O/C ratios, AC3 and AC2 containing more oxygenated groups, must adsorb PEME onto their surface according to a monolayer adsorption mechanism. Fitting procedure demonstrated that the equilibrium data obtained with these two materials can be fitted to the Langmuir isotherm.