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Item type:Publication, Access status: with files , High-pressure reactor technology for aerated biotransformationsUtilizing pressure as a process parameter can make biotechnological processes more efficient and attractive compared to established ones. This paper presents a high-pressure reactor setup for enzymatically catalyzed gas–liquid reactions, which can be operated up to 15.0 MPa. The reactor is equipped with optical measurement technology for inline and in situ monitoring of the oxygen concentration under high-pressure conditions. The setup is characterized by assessing the influence of the process parameter pressure on the conversion of the glucose oxidation to d-glucono-δ-lactone by immobilized glucose oxidase. The study demonstrates that the increased oxygen availability due to higher solubility reduces the reaction time in a batch reactor from 270 to 90 min.Publicationtype: Journal Article65 14 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Adsorptive dead-end filtration for removal of Cr(vi) using novel amine modified polyacrylonitrile ultrafiltration membranes(Royal Society of Chemistry (RSC), 2022-10-18); ; ; ; The present study investigates the concept of combining the processes of ultrafiltration (UF) and ion exchange into one single filtration step. By this, particulate matter and dissolved toxic hexavalent chromium (Cr(vi)) ions are removed by adsorptive dead-end filtration. For this purpose, we modified a conventional polyacrylonitrile (PAN) UF membrane with two methods to generate weak-base and strong-base anion exchanger functional groups on the membrane surface and in its pore structure. The pristine PAN membranes were chemically modified to generate primary (PAN-NH) and quaternary (PAN-Q) amine groups. Pristine PAN, PAN-NH and PAN-Q membranes were characterized and compared regarding their chemical and mechanical properties. The modified PAN membranes were tested in chromium filtration experiments at pH 5.5, pH 7 and pH 8.5. The fully loaded membranes were regenerated by caustic solution for desorption of the chromium. The effect of the membrane modifications on the pure water permeability, contact angle and BET surface was negligible. However, the charge of the membrane was affected significantly seen by the reversal of zeta potential from negative to positive values after modification. The filtration experiments revealed that the total adsorption capacities of PAN-NH and PAN-Q membranes are 151 mg and 145 mg Cr(vi) per m2 membrane surface after complete membrane saturation (cfeed = cpermeate), respectively. When compared with pristine PAN and PAN-Q membrane, the PAN-NH membrane has demonstrated high removal rates (>90%) for Cr(vi) in the first ten hours of filtration and thus more relevant for application-orientated membrane water treatment systems. Desorption of previously adsorbed Cr(vi) was achieved by filtering a regeneration solution (1 M NaCl and 0.01 M NaOH) through the loaded membranes. After regeneration, the adsorption capacity was almost completely recovered. The findings of this study verify that low-pressure amine-modified PAN membranes provide an effective and energy-efficient way to process Cr(vi) contaminated water for possible drinking water purposes.Publicationtype: Journal Article47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , SMART-Reactors : tailoring gas holdup distribution by additively manufactured lattice structures(Wiley-VCH, 2020-07-21); ; ; ; © 2020 The Authors. Published by Wiley-VCH GmbH In chemical process engineering, fast gas-liquid reactions often suffer from an inefficient distribution of gas and therefore mixing and mass transfer performance. This study deals with the possibility of influencing the local gas holdup and bubble size distribution in a gas-liquid process using additively manufactured lattice structures (AMLS). The used measuring technique to study bubble size, velocity, and the local gas holdup is a photo-optical needle probe. By using AMLS, a significant radial homogenization of the local gas holdup and the mean bubble size is achieved. Furthermore, it can be demonstrated that the bubble size can be tailored by the geometry of the inserted structure. It is illustrated that the mean bubble velocities are lowered within the lattice resulting in a higher residence time of the dispersed phase with an impact on the mass transfer performance within the AMLS.Publicationtype: Journal ArticleScopus© Citations 5 248 280