Impact Of Adsorbates Research Articles

Fate of trimethoprim, sulfamethoxazole and caffeine after hydrothermal regeneration of activated carbon

Emerging contaminants are found in all parts of our environment. Adsorption of these contaminants by activated carbon in water treatment plants is well-known; however, a problem resides in the handling of the spent adsorbents. As current regenerative technologies are expensive, the adsorbents are often destructed or landfilled. Here, we examine a novel regeneration method for the used adsorbents with subcritical water – i.e., hydrothermal treatment. The degradation of three well-known emerging contaminants – caffeine, trimethoprim and sulfamethoxazole – was studied with regard to processing temperature (160–280 °C), concentration (2 and 20 mg/L), and the impact of adsorbents. In addition to trimethoprim in the mix at 20 mg/L, the other contaminants were entirely degraded at 280 °C. To obtain insight into transformation products formed during hydrothermal regeneration, we performed non-target and targeted analyses with LC-MS-QTOF using two types of columns, C18 and ZIC-HILIC. This approach ensured a wide range of hydrophilicities. Results showed more transformation products for trimethoprim (20) compared to sulfamethoxazole and caffeine (4). To assess the regeneration efficiencies of the activated carbons, we conducted three cycles of regeneration at 280 °C and between 61 and 120 % degradation was achieved. Moreover, only two transformation products were detected and readsorbed on the adsorbent after regeneration. Hydrothermal regeneration efficiently degraded the target emerging contaminants, suggesting a potential approach for enabling alternative, sequential uses for regenerated activated carbon.

Elucidation of the Active Site for the Oxygen Evolution Reaction on a Single Pt Atom Supported on Indium Tin Oxide.

Single-atom catalysts (SACs) have attracted attention for their high catalytic activity and selectivity, but the nature of their active sites under realistic reaction conditions, involving various ligands, is not well-understood. In this study, we use density functional theory calculations and grand canonical basin hopping to theoretically investigate the active site for the oxygen evolution reaction (OER) on a single Pt atom supported on indium tin oxide, including the influence of the electrochemical potential. We show that the ligands on the Pt atom change from Pt-OH in the absence of electrochemical potential to PtO(OH)4 in electrochemical conditions. This change of the chemical state of Pt is associated with a decrease of 0.3 V for the OER overpotential. This highlights the importance of accurately identifying the nature of the active site under reaction conditions and the impact of adsorbates on the electrocatalytic activity. This theoretical investigation enhances our understanding of SACs for the OER.

Autocorrected off-axis holography of two-dimensional materials

The reduced dimensionality in two-dimensional materials leads a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high resolution microscopy techniques are indispensible. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are the gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the 2D material. We demonstrate these features at the example of h-BN, at which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges.

Sustaining the Oxidation Stability of Biodiesel and Its Blends in Plug-in Hybrid Vehicles Using Adsorbents

This study investigates the impact of adsorbents on the oxidation stability of biodiesel and its blends. Biodiesel fuels contain significant amounts of unsaturated fatty acid esters and therefore, ...

The Impact of Adsorbates on Metal Deposition through the Curvature Enhanced Accelerator Coverage Mechanism

Superconformal electrodeposition utilizing deposition accelerating additives enabled the implementation of damascene interconnects in microelectronics using copper “superfill” in the late 1990’s. The underlying Curvature Enhanced Accelerator Coverage (CEAC) mechanism was defined in 2001. Since then, superconformal deposition of copper, silver and gold in fine features as well as the formation of optically smooth, soft deposits has been successfully predicted by CEAC-based models that capture the interplay of deposition-rate accelerating adsorbate coverage and metal deposition through area change on nonplanar surfaces. Void-free filling of high aspect ratio, submicrometer trenches and vias with silver and gold has been quantitatively predicted and demonstrated using additives selected from the literature on catalysis of metal deposition by additive adsorption. These additives also provide, through the same CEAC mechanism, a means of obtaining optically smooth deposits without relying on deposit-hardening grain refinement through additive incorporation. I will summarize results to date, including what we believe we understand as well as what we don’t.

The Impact of Adsorbates on Metal Deposition through the Curvature Enhanced Accelerator Coverage Mechanism and Beyond

Superconformal electrodeposition utilizing additives that adsorb on the deposit surface and either enhance or suppress metal deposition enabled the implementation of Cu damascene interconnects in microelectronics. The filling process is a consequence of the Curvature Enhanced Accelerator Coverage (CEAC) mechanism, which captures the interplay between adsorbate coverage and the metal deposition rate during area change that necessarily accompanies growth on nonplanar surfaces. CEAC-based models have successfully predicted superconformal deposition using a variety of different chemistries that yield void-free filling of fine features, as well as optically smooth, surfaces of metals such as Cu, Ag and Au. Herein a brief review of advances in the superconformal Au deposition will be detailed. Of particular interest are additives whose behavior is non-monotonic with adsorbate coverage that present new challenges for understanding as well as interesting opportunities for application.

Surface-interface coupling in an oxide heterostructure: Impact of adsorbates onLaAlO3/SrTiO3

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