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Krebs T.,Institute for Sustainable Process Technology | Krebs T.,Wageningen University | Krebs T.,Delta Systems | Ershov D.,Wageningen University | And 2 more authors.
Soft Matter | Year: 2013

We report an experimental method to investigate droplet dynamics in centrifuged emulsions and its application to study droplet compression and coalescence. The experimental setup permits in situ monitoring of an ensemble of droplets in a centrifuged monolayer of monodisperse emulsion droplets using optical microscopy. We studied a hexadecane-in-water emulsion stabilized by the ionic surfactant sodium-n-dodecyl sulfate as a model system. With a microfluidic T-junction emulsion droplets of 97 μm diameter are produced which are subsequently inserted into a rectangular glass chamber of 100 μm height. Using an emulsion which is stable against coalescence, we measured the steady-state oil volume fraction in the compressed layer as a function of the compressive force induced by centrifugation, and quantified the deformation of droplets upon compression. To induce coalescence, we decreased the SDS bulk concentration by dilution of the continuous phase with water before the start of centrifugation. The growth rate of the separated oil phase, which forms on top of the emulsion, and the extent of drop-drop coalescence in the droplet layer upon centrifugation were evaluated as a function of the radial acceleration. The potential of the method for studies in emulsion science and possible improvements of the experimental setup are discussed. This journal is © The Royal Society of Chemistry 2013.

Scientists at the University of Twente research institute MESA+ have developed an electrode in the form of a hollow porous copper fibre which is able to convert carbon dioxide (CO2) into carbon monoxide (CO) extremely efficiently. In principle the invention enables a wide variety of industrial processes, for example in the steel industry, to be made more sustainable. The researchers have applied for a patent on their invention, and their research results have been published in the scientific journal Nature Communications. Researchers at the University of Twente have developed a hollow copper fibre which can be used to convert CO2 into CO with a very high efficiency. The fibre, which serves as an electrode, is provided with countless minute pores. If the fibre is placed in a bath of water, a voltage potential applied, and CO2 pumped in, the CO2 is converted into CO as it passes out through these pores. The principle is straightforward but the efficiency and selectivity of the reaction are surprisingly high, in part because the electrode provides a huge surface area on which the reaction can take place. An important innovation is the optimized interface between gas, fluid and copper particles, allowing the very efficient supply of CO2 and removal of the product, CO. Conversion takes place at about ten times the rate when using the most advanced copper electrodes currently available, while the selectivity (expressed as the percentage of electrons that actually convert CO2 into CO) is 85%, compared to 35% in current copper electrodes. The newly developed electrode also performs better than electrodes made of expensive precious metals such as gold or silver. The fibres are manufactured in the following way. Small copper particles are added to a polymer solution. This solution is guided through a small, ring-shaped slit in a water bath, in which the polymer solution solidifies into the form of a thin hollow fibre. A thermal treatment is then employed to remove the polymer and partially fuse the copper particles. The result is a copper oxide fibre. Reacting this with hydrogen at a high temperature yields the final product: a hollow, porous copper fibre with a diameter of 1.5mm and a wall thickness of 0.1mm. Because this manufacturing technique is based on the way polymeric hollow-fibre membranes are currently constructed on a very large scale, e.g. for kidney dialysis equipment, the researchers involved believe it will be relatively easy to produce the new electrode on a commercial scale. The method can be used for a wide variety of chemical processes requiring gas conversion, in particular because the method used to manufacture the fibres is also suited to materials other than copper; it could apply, for instance, to oxygen conversion in a fuel cell, or hydrogen conversion in the electrochemical production of ammonia. The researchers particularly envisage an important area of application for these copper electrodes to be in the steel industry, where large volumes of CO2 are produced and CO is needed to convert iron ore into iron. The application of these fibres could lead to a step increase in sustainability in this area. The operation of the fibre has been demonstrated in the laboratory; working together with the Institute for Sustainable Process Technology the researchers now plan to optimize the design and develop the methods to suit industrial applications. More information: Recep Kas et al. Three-dimensional porous hollow fibre copper electrodes for efficient and high-rate electrochemical carbon dioxide reduction, Nature Communications (2016). DOI: 10.1038/ncomms10748

Silva V.,Institute for Sustainable Process Technology | Poiesz E.,Cosun Food Technology Center | Van Der Heijden P.,Paques BV
Journal of Applied Electrochemistry | Year: 2013

Industrial processes usually generate streams enriched with high organic and inorganic components. Due to the complexity of these streams sometimes it is not quite straightforward to predict the performance of desalination technologies. Some technologies are available for the selective removal of salts from aqueous stream, but in general these technologies are applied in high value applications where salts are either the product or limit further purification of the final product is required. These technologies are, however, not widely used in low value applications like wastewater treatment. The aim of this article is to review, improve and perform the design of electrodialysis processes for relevant industrial wastewater applications. It is focused on the determination of the critical design parameters like membrane resistance, current efficiency and limiting current density through lab scale experiments and its further use for industrial scale first approximation design. In this article, the basic equations for design are reviewed and a practical approach to obtain the number of stacks required for a certain separation is introduced. An industrial wastewater stream has been used for lab batch experiment and its following continuous plant design. The results show that it is possible to separate monovalent ions in a high rate (more than 70 %) and divalent ions were less separated (less than 50 %). The energy required for the particular case was evaluated in a range from 6 to 11 kWh/m3 of feed stream depending on the water reclamation rate. © 2013 Springer Science+Business Media Dordrecht.

Milosevic M.,TU Eindhoven | Staal K.J.J.,Institute for Sustainable Process Technology | Schuur B.,University of Twente | de Haan A.B.,TU Eindhoven
Desalination | Year: 2013

Concentration of aqueous salt solutions is among the most energy intensive processes in the chemical industry. We here report on extractive concentration as an alternative for the traditional technologies based on water evaporation or reverse osmosis. Extractive technologies are potentially energy-efficient, key is avoiding evaporation of (co-)extracted water during the recovery of the solvent. Polymers have been applied as solvents, because recovery may be done through mild temperature swing. For in total 53 commercially available polymers, the phase behavior of ternary systems containing water, salt (NaCl, Na2SO4, and FeCl3) and polymer was studied at room temperature (294K) and atmospheric pressure. Formation of aqueous two phase systems (ATPS) was studied for various solvent/feed ratios (mass) of (0.25

Patil N.V.,Institute for Sustainable Process Technology | Patil N.V.,Wageningen University | Janssen A.E.M.,Wageningen University | Boom R.M.,Wageningen University
Separation Science and Technology (Philadelphia) | Year: 2014

Whey protein isolate, containing α-Lactalbumin and β-Lactoglobulin, was separated by using a continuous three-stage ultrafiltration cascade system. Single-stage experiments were optimized to enable good and stable cascade operation. Three different cascade configurations, a non-constrained ideal system (Configuration A), and adapted version (Configuration B), and a countercurrent cascade (Configuration C) were experimentally tested and compared. The countercurrent cascade system showed the traditional trade-off between yield and purity. Both the adapted cascade system and the non-constrained ideal cascade gave better performance in terms of recovery and purity and show potential for application, albeit for different purposes. © Taylor & Francis Group, LLC.

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