Adsorption of pharmaceuticals and personal care products in hydrophobic zeolites

• Applicant: Dr. Michael Fischer
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 492604837

Pharmaceuticals and personal care products (PPCPs) are a group of emerging contaminants of particular concern due to their widespread occurrence and potential negative effects on health and environment. PPCPs have been detected in various natural environments, including urban and industrial wastewaters, surface waters, groundwater, and sediments. As conventional wastewater treatment plants were not designed for the removal of PPCPs, several other options have been explored for this purpose, one of them being adsorption-based processes. Although carbon-based adsorbents have been most intensively investigated, hydrophobic zeolites (with high Si/Al ratios up to all-silica composition) also present some important advantages, most prominently high stability and negligible co-adsorption of natural organic matter. While a number of groups have investigated the adsorption of PPCPs in high-silica zeolites experimentally, most studies focused on one or a few zeolite-PPCP combinations. Due to a lack of systematic investigations, there are few guidelines for a rational choice of a suitable zeolite adsorbent for a PPCP (or group of PPCPs) of interest. The capabilities of computational modelling techniques, which can deliver insights into the relationships between pore topology and adsorption properties, have hardly been exploited in this area.The project will use a hierarchical, combined computational-experimental approach to study the adsorption of PPCPs in hydrophobic zeolites. In the first part, force-field-based calculations are used for a “screening” of many zeolite-PPCP combinations, considering about 30 to 40 PPCPs and 10 to 15 different zeolites. Direct simulations of liquid-phase adsorption will be performed for a subset of combinations. In the second part, dispersion-corrected density functional theory calculations (DFT-D) will be used to study zeolite-PPCP combinations of interest in more depth, e.g., in terms of dominant interactions and adsorption-induced deformations. Finally, two or three combinations will be selected for experimental study. These experimental investigations will comprise liquid-phase adsorption experiments as well as a multi-method characterisation of PPCP-loaded zeolite samples using diffraction, thermogravimetry, and different spectroscopic techniques.The screening part of this project aims to show how relatively inexpensive simulations can permit the identification of promising zeolite-PPCP combinations without the need for laborious experiments. The demonstration of the capabilities such a modelling-based approach, validated through experiments for selected cases, should have a significant impact on future application-related studies of zeolites for PPCP removal. The DFT-D calculations and the thorough experimental characterisation of PPCP-loaded samples will contribute to the fundamental understanding of the adsorption of complex organic molecules in zeolites, which is relevant in various fields.

• DFG Programme: Research Grants