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Abstract Vapor phase infiltration (VPI) has emerged as a promising tool for fabrication of novel hybrid materials. In the field of polymeric gas separation membranes, a beneficial impact on stability and membrane performance is known for several polymers with differing functional groups. This study for the first time investigates VPI of trimethylaluminum (TMA) into poly(1‐trimethylsilyl‐1‐propyne) (PTMSP), featuring a carbon–carbon double bond as functional group. Saturation of the precursor inside the polymer is already attained after 60 s infiltration time leading to significant densification of the material. Depth profiling proves accumulation of aluminum in the polymer itself, but a significantly increased accumulation is visible in the gradient layer between polymer and SiO2 substrate. A reaction pathway is proposed and supplemented by density‐functional theory (DFT) calculations. Infrared spectra derived from both experiments and simulation support the presented reaction pathway. In terms of permeance, a favorable impact on selectivity is observed for infiltration times up to 1 s. Longer infiltration times yield greatly reduced permeance values close or even below the detection limit of the measurement device. The present results of this study set a strong basis for the application of VPI on polymers for gas‐barrier and membrane applications in the future.

Abstract Foam formation is a massive challenge in submerged aerated bioprocesses, e.g., in beer fermentation. While the use of antifoam may easily overcome foaming at laboratory scale, it is often an unattractive solution since the challenge remains in future upscaling, as reduced mass transfer and extra steps in product purification and analytics result in increased costs. Interestingly, the number of studies tackling this challenge is relatively low, although literature suggests a range of alternatives, from avoiding foaming to means of controlling or even using foaming as an in situ product removal. Here we give an overview of the topic in five subsections. (1) We argue that a sound understanding of the molecular origin of foaming can facilitate solutions for overcoming the challenge while introducing some long-known challenges (i.e., in beer fermentation). We then review in (2) the apparent avoidance of foam formation before we in (3) summarize possibilities to reduce and control foam after its formation. Subsequently, in (4), we discuss possible solutions that take advantage of foam formation, for example, via foam fractionation for in situ product removal. Finally, in (5), we provide an overview of microbial strain engineering approaches to cope with some aspects of foaming in fermentations. With this review, we would like to sensitize and inform the interested reader while offering an overview of the current literature for the expert, particularly with regard to the foam special issue in Discover Chemical Engineering.

Photocatalytic water treatment is considered a promising technique to prevent micropollutants from entering the environment. However, no off-the-shelf UV reactors on lab scale are available to study new processes and photocatalysts. In this study, we present a tubular UV reactor equipped with 30 UV-LEDs, emitting UV light at 367 nm and a total radiant flux of 42W. The UV reactor has an irradiated length of 300 mm and can host any transparent chemical reactor on the inside with a maximum diameter of 28 mm. The device is optimized for lab experiments with total dimensions of just 334 mm x 193 mm x 172 mm. Besides water treatment, a broad range of other photochemical and photocatalytic experiments can be performed with the reactor. Two identical UV reactors have been built and are successfully used for photocatalytic water treatment experiments. The degradation of methylene blue with TiO2 as photocatalyst was studied to validate the UV reactor. Furthermore, photocatalytic and hybrid processes were conducted in the UV reactor to degrade a broad range of pharmaceutical micropollutants.

The conventional anodic oxygen evolution (OER) in electrochemical CO2 reduction (CO2R) needs to be replaced as it accounts for a major share in energy consumption while being a product of little to no value. In this work, we replace OER by glycerol oxidation reaction (GOR) to synthesize products such as formate, lactate and glycolate. Hereby, for the first time, GOR was successfully paired with cathodic CO2R to formate in a flow reactor at a significant current density of 50 mA/cm2 producing value added anode products with a simultaneously reduced cell voltage. Using a porous platinum anode, GOR reduced the anode potential as well as cell potential by ∼1 V compared to OER. We report an anodic Faraday efficiency (FE) of 30% to ∼53% for liquid products, of which lactate dominates. The structure of the electrode has a significant impact on the dominant product as mainly formate is synthesized on a planar electrode, where the cummulated FE for all liquid products is up to 76%. The concurrent FE to formate at cathode and anode reached a values of up to 74% and 30% respectively and 66% and 76%, respectively, considering all value-added products. By successfully pairing GOR with CO2R in a flow cell reactor, this work marks an important step towards energy-efficient and economically viable processes.

Utilizing CO2 as a resource for CO production in electrochemical reactors requires gas diffusion electrodes (GDE) that maintain a stable and highly reactive gas/liquid/solid interface. When scaling the process towards industrial application, the pressure difference in the electrolyte channel increases, amplifying instabilities at the multi-phase boundary inside the GDE. To tackle this challenge, a falling film design where the electrolyte is solely driven downwards by gravity is presented in this work. The hydrostatic pressure is then counter weighed by the hydrodynamic pressure drop, leading to a constant pressure between gas and liquid side over the height of the electrode. Three 3D-printed electrolyte frame designs were compared in a flow cell regarding the liquid distribution in the channel. An even distribution could be achieved with 2 mm channel thickness at an electrolyte flow rate of 4000 mL min−1. Electrolysis experiments were carried out using a 100 cm2 silver GDE. Compared to a conventional electrolyte frame design, the falling film design yielded stable process conditions with a Faraday Efficiency to CO of up to 90 % at 100 mA cm−2 and a cell voltage of 5.5 V. The presented design presents a pathway for scaling CO2 electrolyzers in height and sustains a stable long-term process.

Tuning the pore size distribution of hemodialysis membranes is essential for the membrane’s selectivity and significantly affects the quality of the dialysis treatment. Tailoring the membrane’s molecular weight cut-off appropriately balances the removal of middle-molecular-weight uremic toxins while avoiding albumin loss. This undesirable albumin loss is a potential side effect and concern for clinical use when aiming at increased removal of middle molecular weight molecules (middle molecules). It is hypothesized that control of the position of a narrow pore size distribution allows middle molecule removal while simultaneously counteracting the unwanted albumin loss. This study presents a comprehensive ex-vivo methodology and novel data on the balance of the clearance of middle molecules and albumin loss at different blood and dialysate flow rates using novel dialyzers. The outcomes hold significance for dialysis therapy, while the insights acquired have broader implications for the selectivity of ultrafiltration membranes.The Theranova dialyzer shows the largest clearance for small-middle molecules. Phylther stands out with higher removal of the middle molecule YKL-40 than the other dialyzers but exhibits a significant albumin loss. Theranova demonstrates the best compromise between low albumin loss and good clearances of middle molecules.

The modification of membranes with polyelectrolytes via the Layer-by-Layer (LBL) method has become state of the art in recent years. It is used to fabricate nanofiltration hollow fiber membranes or to immobilize biomolecules on a membrane surface. However, it still remains a time consuming process. In contrast, this work explores a single-step membrane modification with coating solutions containing both polyanions and polycations. High salt concentration in the coating solution suppresses the complexation of the polyelectrolytes prior to the coating. Then, the controlled reduction of the salt concentration during the coating triggers the formation of a polyelectrolyte complex layer on the membrane. Three coating methods are proposed: (1) In interfacial complexation (IC), the polyelectrolyte solution coats the membrane and is subsequently precipitated by flushing with water. (2) Diffusive desalination (DDS) uses the concentration difference between the coating solution in the lumen and a water stream in the shell side to remove salt ions continuously. (3) In polyelectrolyte concentration (PC), the polyelectrolyte solution is coated at a constant flux. Here, the membrane retains the polyelectrolyte while ions permeate through. First, we evaluate the coating methods regarding their ability to produce nanofiltration membranes, which varies depending on the coating method used. With PC, membranes with up to 79% MgCl2 rejection and a permeability of 30 LMH/bar are obtained. Moreover, in-situ functionalization of the membranes is investigated by the addition of enzymes. Here, with DDS enzymes are immobilized, mostly achieved through adsorption via electrostatic interactions.

Abstract Membrane lungs consist of thousands of hollow fiber membranes packed together as a bundle. The devices often suffer from complications because of non-uniform flow through the membrane bundle, including regions of both excessively high flow and stagnant flow. Here, we present a proof-of-concept design for a membrane lung containing a membrane module based on triply periodic minimal surfaces (TPMS). By warping the original TPMS geometries, the local permeability within any region of the module could be raised or lowered, allowing for the tailoring of the blood flow distribution through the device. By creating an iterative optimization scheme for determining the distribution of streamwise permeability inside a computational porous domain, the desired form of a lattice of TPMS elements was determined via simulation. This desired form was translated into a computer-aided design (CAD) model for a prototype device. The device was then produced via additive manufacturing in order to test the novel design against an industry-standard predicate device. Flow distribution was verifiably homogenized and residence time reduced, promising a more efficient performance and increased resistance to thrombosis. This work shows the promising extent to which TPMS can serve as a new building block for exchange processes in medical devices.

Abstract The reduction of CO2${ m CO}_{2}$ in an electrochemical reactor using electrical energy is a promising approach to implement a more sustainable carbon economy and to replace fossil fuels with renewable carbon sources. Conventionally used solid plate electrodes are limited by poor mass transport of the reactants. Gas diffusion electrodes (GDEs) can overcome this limitation and have gained industrial relevance during the last decades. A comprehensive understanding of transport and conversion phenomena within such porous electrodes is not yet well developed. Here, we report a one‐dimensional steady state model of the GDE to investigate the influence of relevant operational parameters and GDE properties on CO2${ m CO}_{2}$ reduction. The results indicate the importance of controlling the local reaction environment, that is, the reactant concentration and the pH value, by tuning the electrolyte and gas composition, and flow rate as well as the catalyst layer properties.

Abstract During the first wave of Covid-19 infections in Germany in April 2020, clinics reported a shortage of filtering face masks with aerosol retention> 94% (FFP2 & 3, KN95, N95). Companies all over the world increased their production capacities, but quality control of once-certified materials and masks came up short. To help identify falsely labeled masks and ensure safe protection equipment, we tested 101 different batches of masks in 993 measurements with a self-made setup based on DIN standards. An aerosol generator provided a NaCl test aerosol which was applied to the mask. A laser aerosol spectrometer measured the aerosol concentration in a range from 90 to 500 nm to quantify the masks’ retention. Of 101 tested mask batches, only 31 batches kept what their label promised. Especially in the initial phase of the pandemic in Germany, we observed fluctuating mask qualities. Many batches show very high variability in aerosol retention. In addition, by measuring with a laser aerosol spectrometer, we were able to show that not all masks filter small and large particles equally well. In this study we demonstrate how important internal and independent quality controls are, especially in times of need and shortage of personal protection equipment.

In preparative chromatography, a uniform flow distribution through the chromatography device is essential to get an effective ligand utilization and a breakthrough curve that is as steep as possible. Membrane adsorbers usually have a smaller aspect ratio (bed height to diameter ratio) than conventional columns. Upscaling devices with low aspect ratios is challenging due to the trade-off between easy-to-handle flow distribution and the pressure drop over the chromatographic membrane bed. This study aims to investigate the impact of membrane parameters (such as porosity and permeability) and device parameters (such as bed height, incident flow area, and dead volume) on the flow distribution by quantifying simulative and experimental residence time distributions (RTDs). In order to understand and develop a methodology to quantify the impact of the device geometry, the hydrodynamics of axial and radial devices are investigated using CFD simulations. The results show that the device configuration strongly influences the flow distribution. In contrast, the impact of the membrane characteristics on the flow distribution in the investigated small-scale devices with a cross-sectional area of up to 70mm2 is minor. However, membrane characteristics have a significant effect on the pressure drop over the stack. Experimental RTD data allow for evaluating only the impact of the whole device on signal responses. In this study, a purely model-based method was set up according to CFD simulations with the aim of separating the impact of membrane and membrane housing on the flow distribution. It has been shown that the investigated radial-flow devices have favorable hydrodynamic properties due to an optimized housing design and beneficial similar flow path lengths. Furthermore, an equivalent circuit of a CSTR and a DPFR was developed to predict the housing’s RTDs and, in the future, a model-based scale-up of devices.

In a single-step spinning process, we create a thin-walled, robust hollow fiber support made of Torlon® polyamide-imide featuring an intermediate polyethyleneimine (PEI) lumen layer to facilitate the integration and covalent attachment of a dense selective layer. Subsequently, interfacial polymerization of m-phenylenediamine and trimesoyl chloride forms a dense selective polyamide (PA) layer on the inside of the hollow fiber. The resulting thin-film composite hollow fiber membranes show high NaCl rejections of around 96% with a pure water permeability of 1.2 LMH/bar. The high success rate of fabricating the thin-film composite hollow fiber membrane proves our hypothesis of a supporting effect of the intermediate PEI layer on separation layer formation. This work marks a step towards the development of a robust method for the large-scale manufacturing of thin-film composite hollow fiber membranes for reverse osmosis and nanofiltration.

Abstract During soft matter filtration, colloids accumulate in a compressible porous cake layer on top of the membrane surface. The void size between the colloids predominantly defines the cake-specific permeation resistance and the corresponding filtration efficiency. While higher fluxes are beneficial for the process efficiency, they compress the cake and increase permeation resistance. However, it is not fully understood how soft particles behave during cake formation and how their compression influences the overall cake properties. This study visualizes the formation and compression process of soft filter cakes in microfluidic model systems. During cake formation, we analyze single-particle movements inside the filter cake voids and how they interact with the whole filter cake morphology. During cake compression, we visualize reversible and irreversible compression and distinguish the two phenomena. Finally, we confirm the compression phenomena by modeling the soft particle filter cake using a CFD-DEM approach. The results underline the importance of considering the compression history when describing the filter cake morphology and its related properties. Thus, this study links single colloid movements and filter cake compression to the overall cake behavior and narrows the gap between single colloid events and the filtration process.

Abstract Filter cake formation is the predominant phenomenon limiting the filtration performance of membrane separation processes. However, the filter cake’s behavior at the particle scale, which determines its overall cake behavior, has only recently come into the focus of scientists, leaving open questions about its formation and filtration behavior. The present study contributes to the fundamental understanding of soft filter cakes by analyzing the influence of the porous membrane’s morphology on crystal formation and the compaction behavior of soft filter cakes under filtration conditions. Microfluidic chips with nanolithographic imprinted filter templates were used to trigger the formation of crystalline colloidal filter cakes formed by soft microgels. The soft filter cakes were observed via confocal laser scanning microscopy (CLSM) under dead-end filtration conditions. Colloidal crystal formation in the cake, as well as their compaction behavior, were analyzed by optical visualization and pressure data. For the first time, we show that exposing the soft cake to a crystalline filter template promotes the formation of colloidal crystallites and that soft cakes experience gradient compression during filtration.

We provide a direct comparison of two distinct methods of Ti felt surface treatment and Pt/Ir electrocatalyst deposition for the positive electrode of regenerative fuel cells and vanadium–air redox flow batteries. Each method is well documented in the literature, and this paper provides a direct comparison under identical experimental conditions of electrochemical measurements and in identical units. In the first method, based on classical engineering, the bimetallic catalyst is deposited by dip-coating in a precursor solution of the salts followed by their thermal decomposition. In the alternative method, more academic in nature, atomic layer deposition (ALD) is applied to the felts after anodization. ALD allows for a controlled coating with ultralow noble-metal loadings in narrow pores. In acidic electrolyte, the ALD approach yields improved mass activity (557 A·g−1 as compared to 80 A·g−1 at 0.39 V overpotential) on the basis of the noble-metal loading, as well as improved stability.

Provision of large electrode surface areas is key to achieve process intensification in electrochemical processes. While commonly used porous electrode materials such as metal foams can provide increased surface areas, the 3D design is limited to flat electrodes which are prone to mass transport limitations. Here, we show a novel fabrication method for mechanically stable porous nickel electrodes from metal-polymer dispersions. These dispersions enable 3D shaping of the electrodes and therefore the control of the mass transport inside the reactor. The demonstrated addition of pore forming agents to the polymer solution facilitates the targeted hierarchical design of the pore size distribution to yield maximum porosity while maintaining mechanical stability. To compare the specific surface area of the different materials, planar electrodes were produced from nickel-polymer dispersions and their electrochemical surface area (ECSA) was deduced from cyclic voltammetry (CV) measurements. Finally, we demonstrate that our hierarchically porous nickel electrodes with two levels of porosity show an ECSA of 2.4 × 106 m2/m3, which is a 125-fold increase with respect to a commercial nickel foam (19.2 × 103 m2/m3). These metal-polymer dispersions facilitate the fabrication of novel 3D-structured free-form fabricated electrodes for well defined fluid flow conditions, enabling mass transfer control inside the reactor’s flow channel.

Electrochemical reactors present a viable means to unleash the full potential of renewable energies. With maximized surface areas, and thus increased reaction rates, the elimination of diffusion boundary layers on the electrode surface becomes increasingly important, calling for 3D structured electrodes that provide mass transport control inside the reactor. We produce 3D structured stainless steel mixer electrodes with high surface areas from selective laser sintering. By global control of the laser power, electrodes are rendered intrinsically porous without the need to define micro-features. The result is a composite porosity electrode (CPE) with a highly porous skin, a rigid porous support and a dense current collector core. The CPE shows increasing reaction rate of the porous surface with intensifying passive mixing at rising Reynolds numbers. This is explained by a large electrochemical surface area of the porous electrode that is made accessible through the mixer electrode’s mass transport enhancement. With its excellent scalability, this method promises great potential for the process intensification of a wide range of electrochemical applications.

ABSTRACT: Electrokinetic flow phenomena are ubiquitous in electrical systems for desalination, chemical conversion, or mixing at a micro-scale. However, the important features of resulting 3D flow fields are only accessible through cost-intensive numerical simulations. Experimental 2D recording of the chaotic three-dimensional velocity fields developing for example at currents exceeding the limiting current density does not capture the complex 3D structures present in such flow fields. Additionally, numerical 3D studies are limited to dimensions three orders of magnitude smaller as found in real applications and only short run times due to the enormous computational effort. To apply the theoretical knowledge in real-world systems and create the possibility for detailed parameter studies, we present the first experimental method for recording and quantifying the time-resolved velocity field in an electrochemical microfluidic cell in 3D with dimensions found in industrial applications. We utilize this method in a co-submitted paper to record the 3D velocity field of electroconvection at a cation-exchange membrane. • Cell design suitable for simultaneous electrochemical experiments with optical 3D velocity quantification • Method optimized for velocity reconstruction of membrane-to-membrane distances found in industrial cells • Highly adaptable cell design, for optical characterization of electrochemical systems

Abstract Powdery hierarchical porous carbons serve as cost‐effective, functional materials in various fields, namely energy storage, heterogeneous catalysis, electrochemistry, and water/wastewater treatment. Such powdered activated carbons (PAC) limit new module designs and require further preparation steps, for example, adding polymeric binders, to be shaped into a standalone geometry. Polymeric binders, however, can block PACs’ catalytic and active sites and, more importantly, pose the risk of secondary pollution for environmental purposes, especially in the context of clean water supply. This study introduces a novel synthesis method for fabricating freestanding nitrogen‐doped carbons with hierarchical porosity using chitosan and sucrose as green precursors. Chitosan supplies nitrogen and acts as a backbone, giving a freestanding geometry to the final product, and sucrose is a carbon‐rich precursor. The proposed method employs ice‐ and hard‐templating for macropores and mesopores and combines carbonization and activation steps with no required activating agent. Final freestanding carbons function as adsorbents for removing persistent pollutants, as binder‐free electrodes with high specific surface area and capacitive current, and as tubular gas diffusion electrodes for oxygen reduction reactions. These freestanding carbons enable new module designs and can be scaled‐up by numbering‐up, serving as bio‐based functional materials for a wide range of applications involving porous heteroatom‐doped carbons.

Organic neuromorphic devices can accelerate neural networks and integrate with biological systems. Devices based on the biocompatible and conductive polymer PEDOT:PSS are fast, require low amounts of energy and perform well in crossbar simulations. However, parasitic electrochemical reactions lead to self-discharge and the fading of the learned conductance states over time. This limits a neural network’s operating time and requires complex compensation mechanisms. Spiking neural networks (SNNs) take inspiration from biology to implement local and always-on learning. We show that these SNNs can function on organic neuromorphic hardware and compensate for self-discharge by continuously relearning and reinforcing forgotten states. In this work, we use a high-resolution charge transport model to describe the behavior of organic neuromorphic devices and create a computationally efficient surrogate model. By integrating the surrogate model into a Brian 2 simulation, we can describe the behavior of SNNs on organic neuromorphic hardware. A biologically plausible two-layer network for recognizing $28\times28$ pixel MNIST images is trained and observed during self-discharge. The network achieves, for its size, competitive recognition results of up to 82.5%. Building a network with forgetful devices yields superior accuracy during training with 84.5% compared to ideal devices. However, trained networks without active spike-timing-dependent plasticity quickly lose their predictive performance. We show that online learning can keep the performance at a steady level close to the initial accuracy, even for idle rates of up to 90%. This performance is maintained when the output neuron’s labels are not revalidated for up to 24 h. These findings reconfirm the potential of organic neuromorphic devices for brain-inspired computing. Their biocompatibility and the demonstrated adaptability to SNNs open the path towards close integration with multi-electrode arrays, drug-delivery devices, and other bio-interfacing systems as either fully organic or hybrid organic-inorganic systems.

Tangential flow filtration (TFF) is a chemical unit operation used to purify and concentrate liquid suspensions of colloids, proteins, or cells. The solution flows tangentially across a membrane, such that a selective part of the fluid permeates the membrane while the filtrated matter is retained, increasing its concentration. TFF is a mild mechanical purification method that does not interact chemically with the filtrate. It is applied in sensitive separation tasks in protein chemistry, microbiology, or immunology. It is a fast alternative for dialysis applications, also applicable in the field of colloid purification. However, the costs of automated lab-scale devices (30,000 €) and the consumable membrane modules (100–600 €) make TFF currently hardly accessible for lab-scale polymer researchers. Therefore, we built a low-cost TFF system (2400 €) partly automated by an Arduino microcontroller and optimized for diafiltration buffer exchange and concentration processes in soft matter colloid research. We use medical hemodialysis membrane modules that only cost a share (20–50 €) of alternative TFF modules, and we demonstrate the functionality of the system for an exemplary colloidal microgel purification process.

In vanadium redox flow battery systems porous carbon felts are commonly employed as electrodes inside the flow channel. Recently, slurry electrodes (or flow suspension electrodes) were introduced as a potentially viable electrode system. Such electrode systems are little understood so far. Mass, momentum and charge transfer phenomena co-occur, interactions with each other are nearly impossible to capture experimentally. We present a novel discrete model of the particulate phase combining theories from fluid dynamics, colloidal physics, and electrochemistry with a coupled CFD-DEM approach. The methodology allows to visualize local phenomena occurring during the charging of the battery and to compute the net current of the slurry electrode system. We demonstrate that an increasing particle volume fraction enables the formation of conducting networks in the flow electrode until a threshold is reached. Our study concludes, that the assumption of all particles participating in the charge transfer as assumed in pure CFD investigations is not necessarily valid. Keywords: Vanadium redox flow battery, Flow suspension electrode, Slurry electrodes, CFD-DEM simulation, Particle charge transfer phenomena

Selective, nanometer-thin organosilica layers created by plasma-enhanced chemical vapor deposition (PECVD) exhibit selective gas permeation behavior. Despite their promising pure gas performance, published data with regard to mixed gas behavior are still severely lacking. This study endeavors to close this gap by investigating the pure and mixed gas behavior depending on temperatures from 0 °C to 60 °C for four gases (helium, methane, carbon dioxide, and nitrogen) and water vapor. For the two permanent gases, helium and methane, the studied organosilica membrane shows a substantial increase in selectivity from αHe/CH4 = 9 at 0 °C to αHe/CH4 = 40 at 60 °C for pure as well as mixed gases with helium permeance of up to 300 GPU. In contrast, a condensable gas such as CO2 leads to a decrease in selectivity and an increase in permeance compared to its pure gas performance. When water vapor is present in the feed gas, the organosilica membrane shows even stronger deviations from pure gas behavior with a permeance loss of about 60 % accompanied by an increase in ideal selectivity αHe/CO2 from 8 to 13. All in all, the studied organosilica membrane shows very promising results for mixed gases. Especially for elevated temperatures, there is a high potential for separation by size exclusion.

Electrochemical reduction of CO2 to higher-order hydrocarbon products offers a significant contribution to the challenge of a circular economy. In the pursuit of better copper metal catalyst, it was early on realized that increasing productivity of copper catalysts systems is reliant on high surface area per volume. Tubular gas diffusion electrodes offer such properties. In this work, we present a methodology to fabricate tubular hollow fibre copper electrodes with drastically increased intrinsic porosity. Our described method utilizes a standard dealloying process of copper aluminium particles to induce an intra-particle nanoporosity. The specific surface area increases from 0.126 m2 g−1 before dealloying to 6.194 m2 g−1 after dealloying. In comparison to conventional planar copper electrodes and literature data from conventional copper hollow fibres, the intra-particle porosity leads to a drastically increase in electrochemical activity. Electrochemical measurements reveal increased current densities at low over-potentials in comparison to conventional copper electrodes under identical experimental conditions emphasizing the significant impact of the porosity on the electrode performance. The presented method can be easily transferred to other alloy particles, highlighting its versatility for electrode fabrication. Keywords: CO2 reduction, Porous metals, Gas diffusion electrode, Tubular hollow fibre, Copper aluminum alloy

Abstract Renewable raw materials in sustainable biorefinery processes pose new challenges to the manufacturing routes of platform chemicals. Beside the investigations of individual unit operations, the research on process chains, leading from plant biomass to the final products like lactic acid, succinic acid, and itaconic acid is increasing. This article presents a complete process chain from wooden biomass to the platform chemical itaconic acid. The process starts with the mechanical pretreatment of beech wood, which subsequently is subjected to chemo-catalytic biomass fractionation (OrganoCat) into three phases, which comprise cellulose pulp, aqueous hydrolyzed hemicellulose, and organic lignin solutions. Lignin is transferred to further chemical valorization. The aqueous phase containing oxalic acid as well as hemi-cellulosic sugars is treated by nanofiltration to recycle the acid catalyst back to the chemo-catalytic pretreatment and to concentrate the sugar hydrolysate. In a parallel step, the cellulose pulp is enzymatically hydrolyzed to yield glucose, which—together with the pentose-rich stream—can be used as a carbon source in the fermentation. The fermentation of the sugar fraction into itaconic acid can either be performed with the established fungi Aspergillus terreus or with Ustilago maydis. Both fermentation concepts were realized and evaluated. For purification, (in situ) filtration, (in situ) extraction, and crystallization were investigated. The presented comprehensive examination and discussion of the itaconate synthesis process—as a case study—demonstrates the impact of realistic process conditions on product yield, choice of whole cell catalyst, chemocatalysts and organic solvent system, operation mode, and, finally, the selection of a downstream concept.

Abstract Background Ethylene is an important plant hormone that controls many physiological processes in plants. Conventional methods for detecting ethylene include gas chromatographs or optical mid-infrared sensors, which are expensive and, in the case of gas chromatographs, are hardly suitable for automated parallelized online measurement. Electrochemical ethylene sensors are cheap but often suffer from poor resolution, baseline drifting, and target gas oxidation. Thus, measuring ethylene at extremely low levels is challenging. Results This report demonstrates the integration of electrochemical ethylene sensors into a respiration activity monitoring system (RAMOS) that measures, in addition to the oxygen transfer rate, the ethylene transfer rate in eight parallel shake flasks. A calibration method is presented that is not prone to baseline drifting and considers target gas oxidation at the sensor. In this way, changes in ethylene transfer rate as low as 4 nmol/L/h can be resolved. In confirmatory experiments, the overall accuracy of the method was similar to that of gas chromatography-mass spectrometry (GC/MS) measurements. The RAMOS-based ethylene determination method was exemplified with parsley suspension-cultured cells that were primed for enhanced defense by pretreatment with salicylic acid, methyl jasmonate or 4-chlorosalicylic acid and challenged with the microbial pattern Pep13. Ethylene release into the headspace of the shake flask was observed upon treatment with salicylic acid and methyl jasmonate was further enhanced, in case of salicylic acid and 4-chlorosalicylic acid, upon Pep13 challenge. Conclusion A conventional RAMOS device was modified for simultaneous measurement of the ethylene transfer rate in eight parallel shake flasks at nmol/L/h resolution. For the first time electrochemical sensors are used to provide a medium-throughput method for monitoring ethylene release by plants. Currently, this can only be achieved by costly laser-based detection systems and automated gas chromatographs. The new method is particularly suitable for plant cell suspension cultures. However, the method may also be applicable to intact plants, detached leaves or other plant tissues. In addition, the general principle of the technology is likely extendable to other volatiles or gases as well, such as nitric oxide or hydrogen peroxide.

Active layers of ion separation membranes often consist of charged layers that retain ions based on electrostatic repulsion. Conventional fabrication of these layers, such as polyelectrolyte deposition, can in some cases lead to excess coating to prevent defects in the active layer. This excess deposition increases the overall membrane transport resistance. The study at hand presents a manufacturing procedure for controlled polyelectrolyte complexation in and on porous supports by support wetting control. Pre-wetting of the microfiltration membrane support, or even supports with larger pore sizes, leads to ternary phase boundaries of the support, the coating solution, and the pre-wetting agent. At these phase boundaries, polyelectrolytes can be complexated to form partially freestanding selective structures bridging the pores. This polyelectrolyte complex formation control allows the production of membranes with evenly distributed polyelectrolyte layers, providing (1) fewer coating steps needed for defect-free active layers, (2) larger support diameters that can be bridged, and (3) a precise position control of the formed polyelectrolyte multilayers. We further analyze the formed structures regarding their position, composition, and diffusion dialysis performance.

Abstract Protecting our water resources in terms of quality and quantity is considered one of the big challenges of the twenty-first century, which requires global and multidisciplinary solutions. A specific threat to water resources, in particular, is the increased occurrence and frequency of flood events due to climate change which has significant environmental and socioeconomic impacts. In addition to climate change, flooding (or subsequent erosion and run-off) may be exacerbated by, or result from, land use activities, obstruction of waterways, or urbanization of floodplains, as well as mining and other anthropogenic activities that alter natural flow regimes. Climate change and other anthropogenic induced flood events threaten the quantity of water as well as the quality of ecosystems and associated aquatic life. The quality of water can be significantly reduced through the unintentional distribution of pollutants, damage of infrastructure, and distribution of sediments and suspended materials during flood events. To understand and predict how flood events and associated distribution of pollutants may impact ecosystem and human health, as well as infrastructure, large-scale interdisciplinary collaborative efforts are required, which involve ecotoxicologists, hydrologists, chemists, geoscientists, water engineers, and socioeconomists. The research network “project house water” consists of a number of experts from a wide range of disciplines and was established to improve our current understanding of flood events and associated societal and environmental impacts. The concept of project house and similar seed fund and boost fund projects was established by the RWTH Aachen University within the framework of the German excellence initiative with support of the German research foundation (DFG) to promote and fund interdisciplinary research projects and provide a platform for scientists to collaborate on innovative, challenging research. Project house water consists of six proof-of-concept studies in very diverse and interdisciplinary areas of research (ecotoxicology, water, and chemical process engineering, geography, sociology, economy). The goal is to promote and foster high-quality research in the areas of water research and flood-risk assessments that combine and build off-laboratory experiments with modeling, monitoring, and surveys, as well as the use of applied methods and techniques across a variety of disciplines.

Organic solvent nanofiltration (OSN) has evolved to an established recycling method for homogeneous catalysts. However, commercial availability has not circumvented the need for classification and the scoping of possible applications for specific solvent mixtures. Therefore, Evonik’s DuraMem® 300 was assessed for the recycling of magnesium triflate at two transmembrane pressures from a mixture of ethanol, ethyl acetate and water. Catalyst retention up to 98% and permeability of up to 4.44·10−1∙L∙bar−1∙m−2∙h−1 were possible when less than 25% ethyl acetate was in the mixture. The retention of some of the components in the ternary mixture was observed while others were enriched, making the membrane also suitable for fractioning thereof.

Nanofiltration (NF) can enable P recovery from waste streams via retaining multivalent impurities from spent pickling acid. However, with the currently available membranes, an economically feasible process is impossible. Layer-by-layer modified NF membranes are a promising solution for the recovery of P from acidic leachate. LbL membranes show a high level of versatility in terms of fine tuning for ion retention, which is necessary to achieve sufficient phosphorus yields. However, the stability of layer-by-layer modified membranes during phosphoric acid (H3PO4) filtration needs to be further investigated. In our study, we show that a polyethersulfone hollow fiber membrane modified with four or eight bi-layers was stable during immersing and filtering of a 15% H3PO4 solution. A sulfonated polyethersulfone (sPES)-based hollow fiber LbL membrane was only stable during filtration. Thus, we show the importance of applying real process conditions to evaluate membranes. Another important aspect is the influence of the high ionic strength of the feed solution on the membrane. We show that a high ionic strength led to a decrease in Mg retention, which could be increased to 85% by adjusting the process parameters.

AbstractThe immobilization of myoglobin in sodium alginate films was investigated with the aim of evaluating the protein stability in an ionic polymeric matrix. Myoglobin was chosen due to the resemblance to each hemoglobin tetramer. Sodium alginate, being a natural polysaccharide, was selected as the polymeric matrix because of its chemical structure and film-forming ability. To improve the mechanical resistance of sodium alginate films, the polymer was deposited over the surface of a cellulose acetate support by means of ultrafiltration. The ionic crosslink of sodium alginate was investigated by calcium ions. Composite membrane characterization comprised water swelling tests, water flux, SEM images and UV-visible spectroscopy. The electrostatic interaction between the protein and the polysaccharide did not damage the UV-visible pattern of native myoglobin. A good affinity between sodium alginate and cellulose acetate was observed. The top layer of the dense composite membrane successfully immobilized Myoglobin, retaining the native UV-visible pattern for two months.

This work seeks to analyze the inter-relationships that exist between innovation, involvement and attitude in the decomposed model of the Theory of Planned Behavior (TPB), as applied in social psychology, and experience of using the Internet in the process of buyingon-line. An integrative model was prepared that made it possible to explain the relationship that exists between these factors and purchasing from the Internet. A field survey was undertaken with a non-probabilistic sample of students. A multivariate structural equation modeling method was used and applied by the Partial Least Squares (PLS) technique for checking, explaining and comparing the relationship between the constructs. The results show that intention to buy via the Internet is directly influenced by attitude and innovativeness, and attitude is influenced by involvement. No relationship was found between experience in using the Internet and buying from it

Carbon hollow fiber membranes have been prepared by pyrolysis of a P84/S-PEEK blend. Proximate analysis of the precursor was performed using thermogravimetry (TGA), and a carbon yield of approximately 40% can be obtained. This study aimed at understanding the influence of pyrolysis parameters—end temperature, quenching effect, and soaking time—on the membrane properties. Permeation experiments were performed with N2, He, and CO2. Scanning electron microscopy (SEM) has been done for all carbon hollow fibers. The highest permeances were obtained for the membrane submitted to an end temperature of 750°C and the highest ideal selectivities for an end temperature of 700°C. In both cases, the membranes were quenched to room temperature.