Institut für Chemie und Bioanalytik
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Publikation Continuous in situ lactic acid extraction from sweet whey fermentation broth using a tubular membrane contactor(2022) Demmelmayer, Paul; Pérez, Alan; Riedl, Wolfgang; Kienberger, MarleneBackground Whey, as the major dairy by-product, has become a severe problem for the dairy industry because its demand has decreased, while its production has increased in the past years. Since the high demand for dairy products tends to further increase, suitable routes for whey valorization are required. Whey contains valuables like lactate, but due its composition matrix, processing is challenging. The high sugar content in whey makes it a potential feedstock to produce lactic acid (LA) via microbial fermentation. Still, the known drawbacks of biotechnological LA production, such as growth inhibition by the product, the use of neutralizers, low productivity, and high overall costs of the process must be overcome. In situ LA recovering using a suitable separation technology is a potential strategy to overcome the mentioned drawbacks. In this work, the in situ LA extraction from a whey fermentation broth was evaluated. Sweet whey was used as feedstock for lactic acid production via microbial fermentation, while LA was recovered by reactive liquid-liquid extraction using a tubular membrane contactor. Method The feed material used in this work is a fermentation broth from sweet whey, which was filtered prior to extraction experiments using microfiltration. In a first series of experiments, two-phase extraction experiments were conducted in temperature controlled separation funnels, to investigate different solvent phase combinations for the lactic acid extraction. Special attention was paid to replace commonly applied fossil-based solvents with green alternatives, such as deep eutectic solvents (DES). After extraction, the extract was treated in a back-extraction step to recover LA from the solvent phase. Here, an anti-solvent, e.g. heptane or p-cymene, was used to transfer LA to the receiving phase, which was water. Afterwards the performance of reactive liquid-liquid extraction of LA using a PTFE membrane contactor was evaluated by using two potential solvent phases, namely tri-n-octyl amine (TOA) with n-decanol and a DES formed from thymol and menthol. From the experimental results the overall mass transfer coefficient was calculated based on a rigorous mass transfer model to predict the LA concentration in both phases. Finally, performance of the in situ LA recovery from sweet whey by using membrane contactor was investigated from both, experimentally and theoretically points of view. Results & Conclusion In the two-phase extraction experiments, the reactive extractants Aliquat336, TOA, trioctylphosphinoxid (TOPO), and the mixture Aliquat336/TOA were found to be most efficient with the diluents 1-decanol, limonene, and a deep eutectic solvent consisting of thymol and menthol. Especially, the DES and limonene are promising as they can be produced from renewable resources. With respect to back-extraction, heptane and p-cymene showed the highest efficiencies for transferring lactic acid into the receiving phase water. In the next step, the selected solvents were used to perform LA recovery in the tubular membrane contactor from a model aqueous solution of LA and a fermentation broth of sweet whey. The proposed technology for valorizing dairy waste through LA biotechnological production shows the feasibility to scaling it up.06 - PräsentationPublikation Using membrane-supported liquid–liquid extraction for the measurement of extraction kinetics(Swiss Chemical Society, 2011) Riedl, Wolfgang; Mollet, Daniel; Grundler, GerhardMembrane-supported liquid–liquid extraction uses artificial membranes for the generation of a phase interface between the two liquid phases involved in extraction. Additional equipment for the generation of droplets as well as phase separation afterwards is no longer necessary. Since the membranes used for this special type of extraction are quite well described concerning thickness, porosity, tortuosity and material it is possible to generate information about the diffusion coefficient of the component to be extracted within the preferred solvent from extraction trails easily. This article describes an experimental set-up for both the proof of principle of membrane-supported liquid–liquid extraction and, using a dedicated computer-aided data treatment, how to calculate the overall mass transfer coefficient as well as the diffusion coefficient for a given system within moderate testing duration.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Energy-related chemical research at the universities of applied sciences(Swiss Chemical Society, 2013) Riedl, Wolfgang; Fischer, Fabian; Marti, Roger; Brühwiler, DominikAn overview of current activities in the field of energy-related chemical research at the Swiss Universities of Applied Sciences is presented.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Sustainable Chemistry at the Universities of Applied Sciences(Swiss Chemical Society, 2012) Sanglard, Pauline; Rogano, Frank; Naef, Olivier; Riedl, Wolfgang; Crelier, Simon; Fischer, Fabian; Morganti, Franziska; Hinderling, ChristianAn overview of activities in the field of sustainable or 'green' chemistry at the Universities of Applied Sciences in Switzerland is presented.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Limestone nanoparticles as nanopore templates in polymer membranes. Narrow pore size distribution and use as self-wetting dialysis membranes(Royal Society of Chemistry, 2014) Kellenberger, Christoph R.; Pfleiderer, Florian C.; Raso, Renzo; Burri, Cornelia H.; Schumacher, Christoph M.; Grass, Robert N.; Stark, Wendelin J.Limestone nanoparticles can be used as nanopore templates to prepare porous polymeric films. Their application as membranes is so far strongly limited by the fact that these films are highly hydrophobic. In this study, a simple method is reported to directly produce self-wetting membranes by the template removal method. Triethyl citrate modified polyethersulfone and cellulose acetate membranes were produced using dissolvable limestone nanoparticles as pore templates. The nanoporous polymer films were used as dialysis membranes and characterized by means of buffer exchange rate, molecular weight cut-off, protein adsorption, pore size distribution and water contact angle. The herein prepared membranes were further benchmarked against commercially available dialysis membranes with comparable average pore size. They showed narrow pore size distributions, fast dialysis rates at low protein adsorption and molecular weight cut-off of around 12 kDa. Interestingly, the triethyl citrate modified polyethersulfone membranes displayed only moderate change in pore size distribution as a result of the plasticizer additive compared to pure polyethersulfone membranes. This is a matter of substantial interest considering the fact that additive modifications of membranes produced by the predominant phase inversion process typically show alterations in morphology that lead to undesired changes in membrane performance. Furthermore, dextran recovery analysis proved to meet the specific requirements for dialysis membrane characterization and benchmarking.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Template-particle stabilized bicontinuous emulsion yielding controlled assembly of hierarchical high-flux filtration membranes(American Chemical Society, 2015) Hess, Samuel C.; Kohll, A. Xavier; Raso, Renzo; Schumacher, Christoph M.; Grass, Robert N.; Stark, Wendelin J.A novel solvent-evaporation-based process that exploits template-particle stabilized bicontinuous emulsions for the formation of previously unreached membrane morphologies is reported in this article. Porous membranes have a wide range of applications spanning from water filtration, pharmaceutical purification, and battery separators to scaffolds for tissue engineering. Different situations require different membrane morphologies including various pore sizes and pore gradients. However, most of the previously reported membrane preparation procedures are restricted to specific morphologies and morphology alterations require an extensive optimization process. The tertiary system presented in this article, which consists of a poly(ether sulfone)/dimethylacetamide (PES/DMAc) solution, glycerol, and ZnO-nanoparticles, allows simple and exact tuning of pore diameters ranging from sub-20 nm, up to 100 nm. At the same time, the pore size gradient is controlled from 0 up to 840%/μm yielding extreme asymmetry. In addition to structural analysis, water flux rates of over 5600 L m–2 h–1 are measured for membranes retaining 45 nm silica beads.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Regenerable cerium oxide based odor adsorber for indoor air purification from acidic volatile organic compounds(Elsevier, 2014) Raso, Renzo; Stepuk, A.; Mohn, D.; Paunescu, D.; Koehler, F.M.; Stark, W.J.Indoor odor management currently relies on energy-intensive high air exchange rates, or, more sustainable, on single use volatile organic compounds (VOC) adsorbers or ozonisation. This study investigates a more sustainable, multi-cycle use of an odor adsorber system that combines concepts from catalytic oxidation and air cleaning. Both pure and sodium doped, nanostructured CeO2 were tested as adsorber material for high volume removal of odorous compounds from air. As a representative compound for unpleasant odors, hexanoic acid (HA) was used. After air cleaning on fixed beds of CeO2 or Na/CeO2, both hexanoic acid loaded adsorber materials were heated under air and displayed considerable oxidation activity at 191 °C and 263 °C, respectively. Mass spectroscopy was used to confirm that no hexanoic acid desorbed during combustion. Cerium oxide showed an adsorber efficiency of ≥96.5% over a period of 60 h (Cin = 0.044 mg/L, gas hourly space velocity, GHSV = 440 h−1) and sodium doped cerium oxide adsorbed ≥97% for over 90 h (Cin = 0.056 mg/L, GHSV = 1100 h−1). CeO2 was regenerated at 220 °C in air and could be successfully re-used as adsorber without noticeable loss in performance. The study demonstrates that CeO2 has most promising properties for application as re-usable air cleaner due to its very good ability for adsorption even at highly dilute conditions (ppm-level) using a representative acidic test compound with rancid and sweaty odor. Sodium as a basic dopant further improved the adsorption of hexanoic acid but requires a higher regeneration temperature.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Indoor air purification using activated carbon adsorbers: Regeneration using catalytic combustion of intermediately stored VOC(American Chemical Society, 2014) Raso, Renzo; Zeltner, Martin; Stark, Wendelin J.In this study, we demonstrate a two-step process where activated carbon based air purifier systems can be regenerated in situ and eliminate volatile organic compounds (VOCs) from indoor air in an energy efficient way. A carbon based adsorber was combined in series with a CeO2/TiO2 oxidative catalyst for total oxidation of the previously adsorbed and periodically released volatile organic compounds during regeneration runs. We investigated the adsorption and desorption behavior of five different VOCs (diethyl ether, limonene, linalool, hexanoic acid, triethylamine and n-decane) with thermogravimetric measurements, mass spectrometry and elemental analysis. Cyclic loading and regeneration experiments were carried out with selected VOCs (limonene, linalool and n-decane) for testing regeneration at elevated temperature. We showed that in situ thermal regeneration and subsequent oxidation of released VOC is a sustainable and easy applicable technology for indoor air purification. This two-step approach allows energy saving as the VOCs are eliminated discontinuously (enriching VOCs; periodic catalytic combustion), and is of high environmental and economic interest, as much less maintenance services are required.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Physical mixtures of CeO2 and zeolites as regenerable indoor air purifiers. Adsorption and temperature dependent oxidation of VOC(Royal Society of Chemistry, 2014) Raso, Renzo; Stoessel, P. R.; Stark, W. J.Removal of volatile organic compounds (VOC) and indoor air quality regulation through adsorbers required exchange or maintenance of active materials. In this work, we combine well known VOC adsorbers with oxidation catalysts as intimate particulate mixtures. We demonstrate how typical VOC can subsequently adsorb on such mixed material fixed beds (usually days to weeks; the common state of the system, adsorption phase) using small organic compounds (diethyl ether, triethylamine), monoterpenes such as linalool and limonene, and hexanoic acid. Occasional regeneration runs through heat up of the fixed bed results in simultaneous desorption and oxidation of the accumulated VOC, thus regenerating full adsorption capacity for a next adsorption phase. We investigated both small pore zeolites (H-ZSM-5) and larger pore zeolites (13X) and found a distinct interplay between the pore size and the type of VOC. Thermogravimetry coupled with mass spectroscopy was used to quantitatively study the effects of mixing composition and temperature on adsorber performance and regeneration. The here investigated bi-functional systems combine very low maintenance costs and materials requirement with low air flow and exchange costs, thus suggesting mixed (two-functional) bed adsorbers with catalytic function as sustainable alternatives to currently used single use systems based on granulated zeolites or activated carbon. In this work we show the ability of zeolite/cerium oxide physical mixtures to adsorb and capture different classes of VOC at room temperature and release them for oxidation at higher temperatures in a regenerative and sustainable process.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Fibers mechanically similar to sheep wool obtained by wet spinning of gelatin and optional plasticizers(Wiley, 2014) Stoessel, Philipp R.; Raso, Renzo; Kaufmann, Tim; Grass, Robert N.; Stark, Wendelin J.AbstractGelatin is an exceptional and versatile biopolymer with applications in various industries. As the most abundant structural protein in vertebrates it is available in megaton quantities. On these grounds, it would be a plausible substitute for synthetic polymers. Gelatin processing into fibers seems promising as continuous protein filaments do not have the limitation of natural fibers, i.e., small staple fiber length. Instead of spinning an aqueous gelatin solution, a protein precipitate from a phase‐separated system is used. Robust wet spinning with subsequent fiber drawing allows production of a gelatin filament with similar mechanical properties as sheep wool. Different degrees of fiber drawing and addition of plasticizers enable to tailor the mechanical and thermal fiber properties and demonstrate the versatility of the proposed spinning process.01A - Beitrag in wissenschaftlicher Zeitschrift