On the diffusion of carbamazepine, acetaminophen and atenolol in water: An experimental and theoretical approach

Abstract

Due to their intensive use, pharmaceuticals are now considered emerging pollutants which are able to contaminate both surface and groundwater resources. The design of most processes used to remove pharmaceuticals from wastewater requires the knowledge of some key properties, such as the diffusion coefficients of these solutes in water. In this work, the mutual diffusion coefficients of three pharmaceuticals (carbamazepine, acetaminophen and atenolol) in water were measured, as a function of temperature, using the Taylor dispersion method. Intra-diffusion coefficients of the same solutes in water in the same temperature range were also calculated by molecular dynamics simulations. The analysis of the simulation trajectories allowed the study of the structure of the solvent molecules around the solute and their mutual interaction, which was also addressed by quantum mechanical (DFT) calculations. Carbamazepine presents values of diffusion coefficient higher than it would be expected given its molecular weight and size, while atenolol exhibits the opposite behavior, these facts being critically influenced by the different solute-solvent interactions involving each solute. Carbamazepine seems to have a particularly weak interaction with water whereas atenolol is able to interact strongly with the solvent. Both molecular dynamics simulation and DFT results confirm this hypothesis.