Mechanisms of removal of three widespread pharmaceuticals by two clay materials

Abstract

Pharmaceutical residues presence in the environment is among nowadays top emergent environmentalissues. For removal of such pollutants, adsorption is a generally efficient process that can be complemen-tary to conventional treatment. Research of cheap, widely available adsorbents may make this processeconomically attractive. The aim of the present work was to evaluate the capacity of two clay materi-als (exfoliated vermiculite, LECA) to adsorb gemfibrozil, mefenamic acid and naproxen in lab-scale batchassays. Results show that both adsorbents are able to remove the pharmaceuticals from aqueous medium.Although vermiculite exhibited higher adsorption capacities per unit mass of adsorbent, LECA yieldedhigher absolute removals of the pharmaceuticals due to the larger mass of adsorbent. Quantum chem-istry calculations predicted that the forms of binding of the three molecules to the vermiculite surface areessentially identical, but the adsorption isotherm of naproxen differs substantially from the other two’s.The linear forms of the latter impose limits at lower concentrations to the removal efficiencies of thesepharmaceuticals by vermiculite, thereby electing LECA as more efficient. Notwithstanding, vermiculite’shigh specific adsorption capacity and also its much faster adsorption kinetics suggest that there may besome benefits in combining both materials as a composite adsorbent solution.