Removal of Caffeine and Diclofenac from Aqueous Solution by Adsorption on Multiwalled Carbon Nanotubes

A commercial multiwalled carbon nanotube has been used to adsorb caffeine and diclofenac, which are representative anthropogenic markers for wastewater contamination of surface waters. The effect that several parameters, such as the initial concentration of organic molecules, the mass of adsorbent and the contact time, may have on the adsorption behavior of the solid has also been studied. In addition, the adsorption kinetics were studied and found to best fit pseudo-second-order and intraparticle-diffusion models. Equilibrium, which was usually achieved after a contact time of 30 min, is described using various isotherm equation models. After treatment with HCl, the adsorbent was found to maintain its adsorption capacity after one cycle of reuse.