Supported ionic liquids as efficient materials to remove non-steroidal anti-inflammatory drugs from aqueous media

Non-steroidal anti-inflammatory drugs (NSAIDs) are largely consumed worldwide. As a result, NSAIDs were already found in a variety of environmental aqueous samples, in concentrations ranging from ng/L to μg/L. This is due to the inability of the currently used technologies in sewage treatment plants (STPs) and wastewater treatment plants (WWTPs) to completely remove such pollutants/contaminants, thus leading to serious environmental and public health concerns. This work addresses the preparation and application of materials based on silica chemically modified with ionic liquids (SILs) as alternative adsorbents to remove NSAIDs from aqueous media. Modified silica-based materials comprising the 1-methyl-3-propylimidazolium cation combined with six anions were prepared, and chemically and morphologically characterized. Adsorption kinetics, diffusion models and isotherms of sodium diclofenac – as one of the most worldwide consumed NSAIDs – were determined at 298 K. The Boyd’s film diffusion and Webber’s pore diffusion models were used to disclose the rate controlling step affecting the adsorption process. A maximum equilibrium concentration of sodium diclofenac of 0.74 mmol (0.235 g) per g of adsorbent was obtained. Several solvents were tested to remove diclofenac and to regenerate SILs, being the mixture composed of 1-butanol and water (85:15, v:v) identified as the most promising and ecofriendly. After 3 regeneration steps, the material is able to keep up to 75% of its initial adsorption efficiency. Considering the maximum values reported for sodium diclofenac in effluents from WWTPs/STPs, 1 g of the most efficient material is “ideally” able to treat ca. 50,000 L of water. These materials can thus be envisioned as efficient filters to be implemented at domestic environment in countries where the levels of pharmaceuticals are particularly high in drinking water.publishe

The effect of n vs. iso isomerization on the thermophysical properties of aromatic and non-aromatic ionic liquids

This work explores the n vs. iso isomerization effects on the physicochemical properties of different families of ionic liquids (ILs) with variable aromaticity and ring size. This study comprises the experimental measurements, in a wide temperature range, of the ILs' thermal behaviour, heat capacities, densities, refractive indices, surface tensions, and viscosities. The results here reported show that the presence of the iso-alkyl group leads to an increase of the temperature of the glass transition, T-g. The isopyrrolidinium (5 atoms ring cation core) and iso-piperidinium (6 atoms ring cation core) ILs present a strong differentiation in the enthalpy and entropy of melting. Non-aromatic ILs have higher molar heat capacities due to the increase of the atomic contribution, whereas it was not found any significant differentiation between then and iso-alkyl isomers. A small increase of the surface tension was observed for the non-aromatic Its, which could be related to their higher cohesive energy of the bulk, while the lower surface entropy observed for the iso isomers indicates a structural resemblance between the IL bulk and surface. The significant differentiation between ILs with a 5 and 6 atoms ring cation in the n-alkyl series (where 5 atoms ring cations have higher surface entropy) is an indication of a more efficient arrangement of the non-polar region at the surface in ILs with smaller cation cores. The ILs constituted by non aromatic piperidinium cation, and iso-alkyl isomers were found to be the most viscous among the studied Its due to their higher energy barriers for shear stress. (C) 2016 Published by Elsevier B.V