1. 20th European Meeting on Supercritical Fluids : Book of Abstracts2024 Abstract: The 20th European Meeting on Supercritical Fluids (EMSF 2024) was hosted by the Faculty of Chemistry and Chemical Engineering of the University of Maribor from 26 May to 29 May 2024 in Maribor, Slovenia. The EMSF 2024 was a joint event of the International Society for the Advancement of Supercritical Fluids (ISASF) and the European Federation of Chemical Engineering (EFCE) Working Party on High Pressure Technology (WP HPT) Event No. 807. This symposium provided an excellent opportunity for engineers, chemists, physicists, food technologists, and biologists to meet and discuss new ideas, review ongoing challenges, present potential solutions, and identify future issues related to high pressure technologies and supercritical fluids. The aim of the meeting was to deepen connections between researchers, establish new contacts, and promote synergies and partnerships between researchers. The symposium presented the latest advances in high-pressure process technologies that can contribute to the further development of the field.
Keywords: supercritical fluids, fundamental data, novel materials, industrial applications, research and development
Published in DKUM: 24.07.2024; Views: 161; Downloads: 24
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2. Extraction of active compounds from mixtures of hemp (Cannabis sativa) with Pants of the Zingiberaceae familyVesna Postružnik, Taja Žitek Makoter, Darko Goričanec, Petra Kotnik, Željko Knez, Maša Knez Marevci, 2023, original scientific article Keywords: supercritical fluid extraction, ultrasound-assisted extraction, hemp, ginger, turmeric, cardamom
Published in DKUM: 08.05.2024; Views: 234; Downloads: 11
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3. Evaluation of ethanol-induced chitosan aerogels with human osteoblast cellsMilica Pantić, Uroš Maver, Jan Rožanc, Boštjan Vihar, Darija Cör Andrejč, Željko Knez, Zoran Novak, 2023, original scientific article Keywords: chitosan, aerogels, supercritical drying, bone tissue engineering, osteoblasts
Published in DKUM: 06.05.2024; Views: 209; Downloads: 17
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4. Influence of supercritical carbon dioxide on the activity and conformational changes of α-amylase, lipase, and peroxidase in the solid state using white wheat flour as an exampleMilena Ivanović, Željko Knez, Maja Leitgeb, 2023, original scientific article Keywords: enzyme inactivation, supercritical carbon dioxide, a-amilaze, lipase, antioxidants, horseradish peroxidase, structural changes, CD spectroscopy
Published in DKUM: 22.04.2024; Views: 183; Downloads: 8
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7. Degradation of polyvinyl chloride (PVC) waste with supercritical waterMaja Čolnik, Petra Kotnik, Željko Knez, Mojca Škerget, 2022, original scientific article Abstract: The chemical degradation of PVC waste in SCW between 400 and 425 °C and reaction times from 30 to 60 min was studied. The PVC waste in SCW decomposed into the gas, oil, water soluble, and solid phases. The highest yield of the gas and oil phases was achieved at the temperature of 425 °C after 60 min. By increasing the reaction time at 400 °C, the yield of chloride ions in the aqueous phase increased and reached the maximum at 60 min. The gas and oil phases contained many valuable compounds similar to crude oil. Alkanes and chloroalkanes; alkenes, alicyclic, and aromatic hydrocarbons; as well as alcohols were the main groups of hydrocarbons in the oil phase, while the gas phase contained only light hydrocarbons (C1–C6), CO2, and small amounts of H2. This confirmed that the largest chlorine content remains in the aqueous phase and does not pass into the gas phase. It can be concluded that SCW presents effective decomposition media for plastic waste.
Keywords: polyvinyl chloride, supercritical water, chemical recycling, plastic waste
Published in DKUM: 18.09.2023; Views: 513; Downloads: 28
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8. Chemical recycling of polyolefins waste materials using supercritical waterMaja Čolnik, Petra Kotnik, Željko Knez, Mojca Škerget, 2022, original scientific article Abstract: In the following work, the hydrothermal degradation of polypropylene waste (PP) using supercritical water (SCW) has been studied. The procedure was carried out in a high-pressure, high-temperature batch reactor at 425 °C and 450 °C from 15 to 240 min. The results show a high yield of the oil (up to 95%) and gas (up to 20%) phases. The gained oil phase was composed of alkanes, alkenes, cycloalkanes, aromatic hydrocarbons, and alcohols. Alkanes and alcohols predominated at 425 °C and shorter reaction times, while the content of aromatic hydrocarbons sharply increased at higher temperatures and times. The higher heating values (HHVs) of oil phases were in the range of liquid fuel (diesel, gasoline, crude and fuel oil), and they were between 48 and 42 MJ/kg. The gas phase contained light hydrocarbons (C1–C6), where propane was the most represented component. The results for PP degradation obtained in the present work were compared to the results of SCW degradation of colored PE waste, and the potential degradation mechanism of polyolefins waste in SCW is proposed. The results allowed to conclude that SCW processing technology represents a promising and eco-friendly tool for the liquefaction of polyolefin (PE and PP) waste into oil with a high conversion rate.
Keywords: polypropylene, polyolefins, supercritical water, plastics waste, chemical recycling
Published in DKUM: 18.09.2023; Views: 555; Downloads: 21
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9. Green techniques for preparation of red beetroot extracts with enhanced biological potentialDragana Borjan, Vanja Šeregelj, Darija Cör Andrejč, Lato Pezo, Vesna Tumbas Šaponjac, Željko Knez, Jelena J. Vulić, Maša Knez Marevci, 2022, original scientific article Abstract: Red beetroot is well known for its high proportion of betalains, with great potential as functional food ingredients due to their health-promoting properties. The objective of this study was to investigate the influence of processing techniques such as Soxhlet, cold, ultrasound and supercritical fluid extraction on the betalains content and its antioxidant, anti-inflammatory and antihyperglycemic activities. Whilst Soxhlet extraction with water has provided the highest yield, the highest content of total phenolics was found in an extract prepared using Soxhlet extraction with 50% ethanol. Amongst eight phenolic compounds detected in the extracts, protocatechuic acid was the most abundant. The concentrations of total phenolics ranged from 12.09 mg/g (ultrasound extraction with 30% methanol) to 18.60 mg/g (Soxhlet extraction with 50% ethanol). The highest anti-inflammatory activity was observed for cold extraction with 50% methanol extract. The high radical scavenging activity of supercritical fluid extracts could be a consequence of nonphenolic compounds. The chemometrics approach was further used to analyse the results to find the “greenest” method for further possible application in the processing of beetroot in the food and/or pharmaceutical industry. According to the standard score, the best extraction method was determined to be Soxhlet extraction with 50% ethanol.
Keywords: red beetroot, supercritical fluid extraction, antioxidant activity, anti-inflammatory activity, antihyperglycemic activity, chemometric approach
Published in DKUM: 18.08.2023; Views: 436; Downloads: 31
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10. Sustainable processing of materials using supercritical fluids : doktorska disertacijaDragana Borjan, 2022, doctoral dissertation Abstract: Supercritical fluids (SCFs) are powerful solvents with many unique properties. They have great potential for many processes, from extraction to chemical reactions and recycling. Accordingly, phase equilibrium data and thermodynamic and transport properties measurements in systems with a supercritical phase, as well as reliable and versatile mathematical models of the phase equilibrium thermodynamics, are needed for the process design and economic feasibility studies. The dissertation focuses on the benefits of supercritical fluid technology and consists of three main sections.
The first section includes studies of the phase equilibria of the binary gas-alcohol and gas-urea derivatives. The influence of pressure and temperature on the system behaviour (solubility, viscosity, density, interfacial tension, melting point curve) was investigated. Most of the experiments were carried out with a high-pressure optical view cell, with minor modifications of the apparatus and measurement principle to determine mentioned thermodynamic and transport properties.
The second part of the dissertation deals with the recovery of extracts from natural materials. Special interest is oriented towards supercritical fluid extracts, characterised by strong biological activities, especially antimicrobial and antioxidant properties. Supercritical fluid extraction has been performed on a semi-continuous apparatus (at pressures of 150 bar and 250 bar and temperatures of 313.15 K and 333.15 K for oregano extraction; and at pressures of 100 bar and 300 bar and temperatures of 313.15 K and 333.15 K for red beetroot extraction) and various methods such as the microdilution method and the DPPH method were used to determine antimicrobial and antioxidant activity.
In the third part, an overview of different methods for recycling carbon fibre reinforced composites is given, including chemical recycling with supercritical fluids. This field has not been well explored, and the approach is relatively new but very interesting from a sustainable point of view. For an economically feasible process design, the thermodynamic and mass transfer data have to be determined. The principles of the future lab- and pilot-scale operations demand these supporting data be known.
The results obtained in the frame of this study represent the high added value in the scientific field. They are essential to design and modify processes that yield products that cannot be achieved with conventional production processes.
Keywords: supercritical fluids, alcohols, urea, phase equilibria, viscosity, density, interfacial tension, modified capillary method, isolation methods, supercritical fluid extraction, pharmacological activity, carbon fiber reinforced composites, recycling techniques
Published in DKUM: 11.10.2022; Views: 1029; Downloads: 141
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