Abstract: Computational fluid dynamics (CFD) applies numerical methods to solve transport phenomena problems. These include, for example, problems related to fluid flow comprising the Navier--Stokes transport equations for either compressible or incompressible fluids together with turbulence models and continuity equations for single and multi-component (reacting and inert) systems. The design space is first segmented into discrete volume elements (meshing). The finite volume method, the subject of this article, discretizes the equations in time and space to produce a set of non-linear algebraic expressions that are assigned to each volume element-cell. The system of equations is solved iteratively with algorithms like the semi-implicit method for pressure-linked equations (SIMPLE) and the pressure implicit splitting of operators (PISO). CFD is especially useful for testing multiple design elements because it is often faster and cheaper than experiments. The downside is that this numerical method is based on models that require validation to check their accuracy. According to a bibliometric analysis, the broad research domains in chemical engineering include: (1) dynamics and CFD-DEM (2) fluid flow, heat transfer and turbulence, (3) mass transfer and combustion, (4) ventilation and environment, and (5) design and optimization. Here, we review the basic theoretical concepts of CFD and illustrate how to set up a problem in the open-source software OpenFOAM to isomerize n-butane to i-butane in a notched reactor under turbulent conditions. We simulated the problem with 1000, 4000, and 16000 cells. According to the Richardson extrapolation, the simulation underestimates the adiabatic temperature rise by 7% with 16000 cells.

Abstract: In this work we present an assay to probe the oxygen activation rate on plasmonic nanoparticles under visible light. Using a superoxide-specific XTT molecular probe, the oxygen activation rate on bimetallic gold-silver “rainbow” nanoparticles with a broadband visible light (> 420 nm) response, is determined at different light intensities by measuring its conversion into the colored XTT-formazan derivate. A kinetic model is applied to enable a quantitative estimation of the rate constant, and is shown to match almost perfectly with the experimental data. Next, the broadband visible light driven oxygen activation capacity of this plasmonic rainbow system, supported on nano-sized SiO 2 , is demonstrated towards the oxidation of aniline to azobenzene in DMSO. To conclude, a brief theoretical discussion is devoted to the possible mechanisms behind such plasmon-driven reactions.

Abstract: In the last few years, governments all around the world have agreed upon migrating towards carbon-neutral economies as a strategy for restraining the effects of climate change. A major obstacle limiting this achievement is greenhouse gases emissions, for which the aviation sector is a key contributor because of its dependence on fossil fuels. As an alternative, biofuels with similar characteristics to current fossil-fuels and fully compatible with the existing petroleum infrastructure (i.e., drop-in biofuels) are being developed. In this regard, microalgae are a promising feedstock thanks to, among other aspects, their potential for lipid accumulation. This review outlines the development status, opportunities, and challenges of different technologies that are capable of or applicable to transform microalgae into aviation fuels. To this effect, a baseline of the existing jet fuels and the requirements for potential aviation biofuels is initially presented. Then, microalgae production and valorization techniques are discussed with an emphasis on the thermochemical pathways. Finally, an assessment of the present techno-economic feasibility of microalgae-derived aviation fuels is discussed, along with the authors’ point of view on the suitability of these techniques. Further developments are needed to reduce the costs of cultivation and harvesting of microalgae, and a biorefinery approach might improve the economics of the overall process. In addition, while each of the conversion routes described has its advantages and drawbacks, they converge upon the need of optimizing the deoxygenation techniques and the proportion of the suitable type of hydrocarbons that match fuel requirements.

Abstract: High-rate activated sludge (HRAS) relies on good bioflocculation and subsequent solid-liquid separation to maximize the capture of organics. However, full-scale applications often suffer from poor and unpredictable effluent suspended solids (ESS). While the biological aspects of bioflocculation are thoroughly investigated, the effects of fines (settling velocity < 0.6 m3/m2/h), shear and surface overflow rate (SOR) are unclear. This work tackled the impact of fines, shear, and SOR on the ESS in absence of settleable influent solids. This was assessed on a full-scale HRAS step-feed (SF) and pilot-scale HRAS contact-stabilization (CS) configuration using batch settling tests, controlled clarifier experiments, and continuous operation of reactors. Fines contributed up to 25% of the ESS in the full-scale SF configuration. ESS decreased up to 30 mg TSS/L when bioflocculation was enhanced with the CS configuration. The feast-famine regime applied in CS promoted the production of high-quality extracellular polymeric substances (EPS). However, this resulted in a narrow and unfavorable settling velocity distribution, with 50% ± 5% of the sludge mass settling between 0.6 and 1.5 m3/m2/h, thus increasing sensitivity towards SOR changes. A low shear environment (20 s−1) before the clarifier for at least one min was enough to ensure the best possible settling velocity distribution, regardless of prior shear conditions. Overall, this paper provides a more complete view on the drivers of ESS in HRAS systems, creating the foundation for the design of effective HRAS clarifiers. Tangible recommendations are given on how to manage fines and establish the optimal settling velocity of the sludge.

Abstract: Plasma-catalytic ammonia decomposition as a method for producing hydrogen was studied in a packed-bed dielectric barrier discharge (DBD) reactor at ambient pressure and a fixed plasma power. The influence of packing the plasma zone with various dielectric materials, typically used as catalyst supports, was examined. At conditions (21 W, 75 Nml/min NH3) where an NH3 conversion of 5% was achieved with plasma alone, an improved decomposition was found when introducing dielectric materials with dielectric constants between 4 and 30. Of the tested materials, MgAl2O4 yielded the highest conversion (15.1%). The particle size (0.3-1.4 mm) of the MgAl2O4 packing was found to have a modest influence on the conversion, which dropped from 15.1% to 12.6% with increasing particle size. Impregnation of MgAl2O4 with different metals was found to decrease the NH3 conversion, with the Ni impregnation still showing an improved conversion (7%) compared to plasma-only. The plasma-assisted ammonia decomposition occurs in the gas phase due to micro-discharges, as evident from a linear correlation between the conversion and the frequency of micro-discharges for both plasma alone and with the various solid packing materials. The primary function of the solid is thus to facilitate the gas phase reaction by assisting the creation of micro-discharges. Lastly, insulation of the reactor to raise the temperature to 230 degrees C in the plasma zone was found to have a negative effect on the conversion, as a change from volume discharges to surface discharges occurred. The study shows that NH3 can be decomposed to provide hydrogen by exposure to a non-thermal plasma, but further developments are needed for it to become an energy efficient technology. (C)2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Abstract: We developed a novel in situ (i.e. inside plasma and during operation) IR dielectric barrier discharge cell allowing investigation of plasma catalysis in transmission mode, atmospheric pressure, flow conditions (WHSV similar to 0-50 000 mL g(-1) h(-1)), at relevant discharge voltages (similar to 0-50 kV) and frequencies (similar to 0-5 kHz). We applied it to study the IR-active surface species formed on a SiO2 support and on a 3 wt% Ru/SiO2 catalyst, which can help to reveal the important surface reaction mechanisms during the plasma-catalytic dry reforming of methane (DRM). Moreover, we present a technique for the challenging task of estimating the temperature of a catalyst sample in a plasma-catalytic system in situ and during plasma operation. We found that during the reaction, water is immediately formed at the SiO2 surface, and physisorbed formic acid is formed with a delay. As Ru/SiO2 is subject to greater plasma-induced heating than SiO2 (with a surface temperature increase in the range of 70-120 degrees C, with peaks up to 150 degrees C), we observe lower amounts of physisorbed water on Ru/SiO2, and less physisorbed formic acid formation. Importantly, the formation of surface species on the catalyst sample in our plasma-catalytic setup, as well as the observed conversions and selectivities in plasma conditions, can not be explained by plasma-induced heating of the catalyst surface, but must be attributed to other plasma effects, such as the adsorption of plasma-generated radicals and molecules, or the occurrence of Eley-Rideal reactions.

Abstract: Co-digestion of organic waste and wastewater is receiving increased attention as a plausible waste management approach toward energy recovery. However, traditional anaerobic processes for co-digestion are particularly susceptible to severe organic loading rates (OLRs) under long-term treatment. To enhance technological feasi-bility, this work presented a two-stage Anaerobic Membrane Bioreactor (2 S-AnMBR) composed of a hydrolysis reactor (HR) followed by an anaerobic membrane bioreactor (AnMBR) for long-term co-digestion of food waste and kitchen wastewater. The OLRs were expanded from 4.5, 5.6, and 6.9 kg COD m- 3 d-1 to optimize biogas yield, nitrogen recovery, and membrane fouling at ambient temperatures of 25-32 degrees C. Results showed that specific methane production of UASB was 249 +/- 7 L CH4 kg-1 CODremoved at the OLR of 6.9 kg TCOD m- 3 d-1. Total Chemical Oxygen Demand (TCOD) loss by hydrolysis was 21.6% of the input TCOD load at the hydraulic retention time (HRT) of 2 days. However, low total volatile fatty acid concentrations were found in the AnMBR, indicating that a sufficiently high hydrolysis efficiency could be accomplished with a short HRT. Furthermore, using AnMBR structure consisting of an Upflow Anaerobic Sludge Blanket Reactor (UASB) followed by a side -stream ultrafiltration membrane alleviated cake membrane fouling. The wasted digestate from the AnMBR comprised 42-47% Total Kjeldahl Nitrogen (TKN) and 57-68% total phosphorous loading, making it suitable for use in soil amendments or fertilizers. Finally, the predominance of fine particles (D10 = 0.8 mu m) in the ultra -filtration membrane housing (UFMH) could lead to a faster increase in trans-membrane pressure during the filtration process.

Abstract: The COVID-19 pandemic had large repercussions for our economy and organizations. Improved resilience can give organizations the ability to withstand crises and build back better and faster. This article assesses resilience of organizations and sole proprietorships in the context of the COVID-19 pandemic with eight circular strategies as explanatory variables. Furthermore, these eight circular strategies are also used to assess the organizations' and sole proprietorships' resilience outside of the COVID-19 pandemic. This analysis is conducted to explain how circular strategies can help companies and sole proprietorships maintain stability. The analysis was performed by means of a survey conducted between May and June 2020 in Flanders (Belgium), using a sample of 542 respondents. After performing a regression analysis combined with expert opinions collected through interviews, we find that companies and sole proprietorships with a higher circularity score have a significantly higher resilience score during crises and during normal times, compared to less circular companies. Furthermore, we find that the size of the company does not matter during a crisis to adapt and react flexibly, while it is important when there is no crisis. Finally, we argue that it is the combination of different circular strategies which yields to the highest results for the organizations' resilience and we provide policy recommendations based on the most asked support measures.

Abstract: Advances in multi-spectral detectors are causing a paradigm shift in x-ray computed tomography (CT). Spectral information acquired from these detectors can be used to extract volumetric material composition maps of the object of interest. If the materials and their spectral responses are known a priori, the image reconstruction step is rather straightforward. If they are not known, however, the maps as well as the responses need to be estimated jointly. A conventional workflow in spectral CT involves performing volume reconstruction followed by material decomposition, or vice versa. However, these methods inherently suffer from the ill-posedness of the joint reconstruction problem. To resolve this issue, we propose 'A Dictionary-based Joint reconstruction and Unmixing method for Spectral Tomography' (ADJUST). Our formulation relies on forming a dictionary of spectral signatures of materials common in CT and prior knowledge of the number of materials present in an object. In particular, we decompose the spectral volume linearly in terms of spatial material maps, a spectral dictionary, and the indicator of materials for the dictionary elements. We propose a memory-efficient accelerated alternating proximal gradient method to find an approximate solution to the resulting bi-convex problem. From numerical demonstrations on several synthetic phantoms, we observe that ADJUST performs exceedingly well compared to other state-of-the-art methods. Additionally, we address the robustness of ADJUST against limited and noisy measurement patterns. The demonstration of the proposed approach on a spectral micro-CT dataset shows its potential for real-world applications. Code is available at https://github.com/mzeegers/ADJUST.

Abstract: Particulate matter is one of the most persistent global air pollutants that is causing health problems, climate disturbance and building deterioration. A sustainable technique that is able to degrade soot using (sun)light is photocatalysis. Currently, research on photocatalytic soot oxidation focusses on large band gap TiO2-based photocatalysts and thus requires the use of UV light. It would prove useful if visible light, and thus a larger fraction of the (freely available) solar spectrum, could additionally be utilised to drive this process. In this work, a visible light-active photocatalyst, WO3, is benchmarked to TiO2 under both UV and visible light. At the same time, the versatility and drastic improvement of a recently introduced digital image-based soot degradation detection method are demonstrated. An additional step correcting for non-soot related catalyst colour changes is applied, resulting in accurate detection and quantification of soot degradation for all studied photocatalysts, even for materials such as WO3 that are inherently coloured. With this study, we aim to broaden the scope of photocatalytic soot oxidation technology to visible light-active photocatalyst. Along with this study, we provide a versatile soot degradation detection methodology based on digital image analysis that is made widely applicable.

Abstract: Using a particle-based model, we examine the collective dynamics of skyrmions interacting with a funnel potential under dc driving as the skyrmion density and relative strength of the Magnus and damping terms are varied. For driving in the easy direction, we find that increasing the skyrmion density reduces the average skyrmion velocity due to jamming of skyrmions near the funnel opening, while the Magnus force causes skyrmions to accumulate on one side of the funnel array. For driving in the hard direction, there is a critical skyrmion density below which the skyrmions become trapped. Above this critical value, a clogging effect appears with multiple depinning and repinning states where the skyrmions can rearrange into different clogged configurations, while at higher drives, the velocity-force curves become continuous. When skyrmions pile up near the funnel opening, the effective size of the opening is reduced and the passage of other skyrmions is blocked by the repulsive skyrmion-skyrmion interactions. We observe a strong diode effect in which the critical depinning force is higher and the velocity response is smaller for hard direction driving. As the ratio of Magnus force to dissipative term is varied, the skyrmion velocity varies in a non-linear and non-monotonic way due to the pile up of skyrmions on one side of the funnels. At high Magnus forces, the clogging effect for hard direction driving is diminished.

Abstract: All-inorganic lead-free halide double perovskites offer a promising avenue toward non-toxic, stable optoelec-tronic materials, properties that are missing in their prominent lead-containing counterparts. Their large ther-mopowers and high carrier mobilities also make them promising for thermoelectric applications. Here, we present a first-principles study of the lattice vibrations and thermal transport behaviors of Cs2SnI6 and gamma-CsSnI3, two prototypical compounds in this materials class. We show that conventional static zero temperature density functional theory (DFT) calculations severely underestimate the lattice thermal conductivities (kappa l) of these compounds, indicating the importance of dynamical effects. By calculating anharmonic renormalized phonon dispersions, we show that some optic phonons significantly harden with increasing temperature (T), which reduces the scattering of heat carrying phonons and enhances calculated kappa l values when compared with standard zero temperature DFT. Furthermore, we demonstrate that coherence contributions to kappa l, arising from wave like phonon tunneling, are important in both compounds. Overall, calculated kappa l with temperature-dependent inter-atomic force constants, built from particle and coherence contributions, are in good agreement with available measured data, for both magnitude and temperature dependence. Large anharmonicity combined with low phonon group velocities yield ultralow kappa l values, with room temperature values of 0.26 W/m-K and 0.72 W/m-K predicted for Cs2SnI6 and gamma-CsSnI3, respectively. We further show that the lattice dynamics of these compounds are highly anharmonic, largely mediated by rotation of the SnI6 octahedra and localized modes originating from Cs rattling motion. These thermal characteristics combined with their previously computed excellent electronic properties make these perovskites promising candidates for optoelectronic and room temperature thermoelectric applications.

Abstract: Acid-tolerant ammonia-oxidizing bacteria (AOB) can open the door to new applications, such as partial nitritation at low pH. However, they can also be problematic because chemical nitrite oxidation occurs at low pH, leading to the release of harmful nitrogen oxide gases. In this publication, the role of acid-tolerant AOB in urine treatment was explored. On the one hand, the technical feasibility of ammonia oxidation under acidic conditions for source-separated urine with total nitrogen concentrations up to 3.5 g-N L−1 was investigated. On the other hand, the abundance and growth of acid-tolerant AOB at more neutral pH was explored. Under acidic conditions (pH of 5), ammonia oxidation rates of 500 mg-N L−1 d−1 and 10 g-N g-VSS-1 d-1 were observed, despite high concentrations of 15 mg-N L−1 of the AOB-inhibiting compound nitrous acid and low concentration of 0.04 mg-N L−1 of the substrate ammonia. However, ammonia oxidation under acidic conditions was very sensitive to process disturbances. Even short periods of less than 12 h without oxygen or without influent resulted in a complete cessation of ammonia oxidation with a recovery time of up to two months, which is a problem for low maintenance applications such as decentralized treatment. Furthermore, undesirable nitrogen losses of about 10% were observed. Under acidic conditions, a novel AOB strain was enriched with a relative abundance of up to 80%, for which the name “Candidatus (Ca.) Nitrosacidococcus urinae” is proposed. While Nitrosacidococcus members were present only to a small extent (0.004%) in urine nitrification reactors operated at pH values between 5.8 and 7, acid-tolerant AOB were always enriched during long periods without influent, resulting in an uncontrolled drop in pH to as low as 2.5. Long-term experiments at different pH values showed that the activity of “Ca. Nitrosacidococcus urinae” decreased strongly at a pH of 7, where they were also outcompeted by the acid-sensitive AOB Nitrosomonas halophila. The experiment results showed that the decreased activity of “Ca. Nitrosacidococcus urinae” correlated with the limited availability of dissolved iron at neutral pH.

Abstract: The cation distribution of the negative temperature coefficient (NTC) thermistor spinel NiMn2O4 was studied in the temperature range from 55 to 900 degrees C, using a combined in situ neutron diffraction and thermopower study. Rietveld refinements of in situ neutron diffraction data reveal a temperature dependence of the degree of inversion with an inversion parameter of 0.70(1) at 900 degrees C and 0.87(1) at 55 degrees C. Thermopower measurements were evaluated using a modified Heikes formula, and the [Mn4+]/[Mn3+] ratio on octahedral sites of the spinel structure was calculated considering spin and orbital degeneracy. The inversion degree and disproportionation parameter, determined independently as function of temperature, were used to calculate the cation distribution of NiMn2O4 in the whole temperature range. At high temperature, within the stability range of the spinel, the cation distribution is characterized by a moderate degree of inversion with a concentration of NiB2+${\mathrm{Ni}}_\mathrm{B}<

Abstract: Illicit drugs continue to pose a serious threat to society and public health. Drug (ab)use is linked to organised crime and violence. Therefore, to fight the so-called war on drugs, police and law enforcement agencies need to be equipped with accurate and efficient sensors for the detection of illicit drugs and drug use. Even though colour tests (for powders) and lateral flow immunoassays (for biological samples) lack accuracy, they are relied upon for fast and easy on-site detection. Alternatively, in recent years, there has been an increasing interest in electrochemical sensors as a promising technique for the rapid and accurate on-site detection of illicit drugs. While a myriad of literature exists on the use of electrochemical sensors for drug powder analysis, literature on their use for the detection of drug use in biological samples is scarce. To this end, this review presents an overview of strategies for the electrochemical detection of illicit drugs in oral fluid. First, pharmacokinetics of drugs in oral fluid and the legal limit dilemma regarding the analytical cut-offs for roadside drug detection tests are elaborated to present the reader with the background knowledge required to develop such a test. Subsequently, an overview of electrochemical strategies developed for the detection of illicit drugs in oral fluid is given. Importantly, key challenges to address in the development of roadside tests are highlighted to improve the design of the next electrochemical devices and to bring them to the field. Overall, electrochemical sensors for illicit drugs detection in oral fluid show promise to disrupt current strategies for roadside testing.