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

Abstract

<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>

Spatial Reuse in IEEE 802.11ax WLANs

“…Notice that the 11ax amendment does not provide any mechanism for setting the OBSS/PD threshold, thus remaining open (see, e.g., the proposal in [32]). Nevertheless, the standard defines a set of rules for limiting the OBSS/PD threshold, 9 which is upper bounded as follows (also illustrated in Figure 9 where OBSS/PD min and OBSS/PD max are set to −82 dBm and −62 dBm, respectively, the reference power TX PWR ref is set to 21 or 25 dBm, based on the capabilities of the device, 10 and TX PWR refers to the transmission power at the antenna connector in dBm of the HE node identifying the SR-based TXOP.…”