High-Silica Zeolites as Sorbent Media for Adsorption and Pre-Concentration of Pharmaceuticals in Aqueous Solutions

The present work focused on the use of high-silica commercial zeolites as sorbent media for pharmaceuticals in an aqueous matrix. As drug probes, ketoprofen, hydrochlorothiazide, and atenolol were selected, because of their occurrence in surface waters and effluents from wastewater treatment plants. Pharmaceuticals adsorption was evaluated for two Faujasite topology zeolites with Silica/Alumina Ratio 30 and 200. The selected zeolites were demonstrated to be efficient sorbents towards all investigated pharmaceuticals, thanks to their high saturation capacities (from 12 to 32% w/w) and binding constants. These results were corroborated by thermal and structural analyses, which revealed that adsorption occurred inside zeolite’s porosities, causing lattice modifications. Finally, zeolites have been tested as a pre-concentration media in the dispersive-solid phase extraction procedure. Recoveries higher than 95% were gained for ketoprofen and hydrochlorothiazide and approximately 85% for atenolol, at conditions that promoted the dissolution of the neutral solute into a phase mainly organic. The results were obtained by using a short contact time (5 min) and reduced volume of extraction (500 µL), without halogenated solvents. These appealing features make the proposed procedure a cost and time saving method for sample enrichment as well as for the regeneration of exhausted sorbent, rather than the more energetically expensive thermal treatment.

Simulation-Based Evaluation of Zeolite Adsorbents for the Removal of Emerging Contaminants

<p>A number of experimental studies have evaluated the potential of hydrophobic high-silica zeolites for the adsorptive removal of emerging organic contaminants, such as pharmaceuticals and personal care products, from water. Despite the widespread use of molecular modelling techniques in various other fields of zeolite science, the adsorption of pharmaceuticals and related pollutants has hardly been studied computationally. In this work, inexpensive molecular simulations using a literature force field (DREIDING) were performed to study the interaction of 21 emerging contaminants with two all-silica zeolites, mordenite (MOR topology) and zeolite Y (FAU topology). The selection of adsorbents and adsorbates was based on a previous experimental investigation of organic contaminant removal using high-silica zeolites (Rossner et al., <i>Water Res.</i> <b>2009</b>, <i>43</i>, 3787–3796). An analysis of the lowest-energy configurations revealed a good correspondence between calculated interaction energies and experimentally measured removal efficiencies (strong interaction – high removal), despite a number of inherent simplifications. This indicates that such simulations could be used as a screening tool to identify promising zeolites for adsorption-based pollutant removal prior to experimental investigations. To illustrate the predictive capabilities of the method, additional calculations were performed for acetaminophen adsorption in 11 other zeolite frameworks, as neither mordenite nor zeolite Y remove this pharmaceutical efficiently. Furthermore, the lowest-energy configurations were analysed for selected adsorbent-adsorbate combinations in order to explain the observed differences in affinity.</p>

Simulation-Based Evaluation of Zeolite Adsorbents for the Removal of Emerging Contaminants

<p>A number of experimental studies have evaluated the potential of hydrophobic high-silica zeolites for the adsorptive removal of emerging organic contaminants, such as pharmaceuticals and personal care products, from water. Despite the widespread use of molecular modelling techniques in various other fields of zeolite science, the adsorption of pharmaceuticals and related pollutants has hardly been studied computationally. In this work, inexpensive molecular simulations using a literature force field (DREIDING) were performed to study the interaction of 21 emerging contaminants with two all-silica zeolites, mordenite (MOR topology) and zeolite Y (FAU topology). The selection of adsorbents and adsorbates was based on a previous experimental investigation of organic contaminant removal using high-silica zeolites (Rossner et al., <i>Water Res.</i> <b>2009</b>, <i>43</i>, 3787–3796). An analysis of the lowest-energy configurations revealed a good correspondence between calculated interaction energies and experimentally measured removal efficiencies (strong interaction – high removal), despite a number of inherent simplifications. This indicates that such simulations could be used as a screening tool to identify promising zeolites for adsorption-based pollutant removal prior to experimental investigations. To illustrate the predictive capabilities of the method, additional calculations were performed for acetaminophen adsorption in 11 other zeolite frameworks, as neither mordenite nor zeolite Y remove this pharmaceutical efficiently. Furthermore, the lowest-energy configurations were analysed for selected adsorbent-adsorbate combinations in order to explain the observed differences in affinity.</p>