1. Upcycling wool and feather waste into nanofibers via eco-friendly hydrothermally assisted isolation of keratin : a promising approach to tunable functionalitiesSimona Strnad, Miša Žnidarič, Mojca Škerget, Maja Čolnik, Lidija Gradišnik, Uroš Maver, Lidija Fras Zemljič, 2025, original scientific article Abstract: Hydrothermal degradation processes are a particularly promising eco-friendly approach to keratin isolation from biomass. They, however, result in products with a broad molecular weight distribution, which can be particularly unfavorable for fiber production. In this study, we aimed to determine whether hydrothermally degraded feather and wool waste is suitable to produce nanofibers that retain the key functional properties of keratin, such as antioxidant activity and biocompatibility. Keratin/PEO blends were used for needleless electrospinning of nanofibers cross-linked with two different cross-linkers, ethylene glycol diglycidyl ether (EGDE) and pentaerythritol triacrylate (PETA), to improve their stability to water. The surface tension, pH, turbidity, zeta potential, and protein concentration of the keratin extract solutions were analyzed. The morphology of the produced nanofibers was analyzed using a scanning electron microscope, the surface chemical structure by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR analysis), and the cross-linking success by water contact angle measurements. The antioxidant capacity and the biocompatibility of the nanofiber mats with skin cells were investigated using a 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) vitality test, respectively. The results showed that despite the unfavorable starting materials with a wide molecular mass range from 3 to 15 kDa and low average molecular weights keratin products obtained by a green hydrothermal extraction process can be used to produce nanofibers with excellent antioxidant properties and skin cell biocompatibility. The cross-linking of the nanofibers resulted in hydrophobic nanofiber surfaces; however, it impaired their biocompatibility with skin cells compared to noncross-linked nanofibers.
Keywords: waste chicken feathers, wool, keratin nanofibers, greene xtraction process, subcritical water, hydrothermal isolation process, electrospinning, cross-linking
Published in DKUM: 28.11.2025; Views: 0; Downloads: 2
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2. The conversion of pistachio and walnut shell waste into valuable components with subcritical waterMaja Čolnik, Mihael Irgolič, Amra Perva, Mojca Škerget, 2024, original scientific article Abstract: Pistachio and walnut shells accumulate in large quantities as waste during food processing and represent a promising lignocellulosic biomass for the extraction of valuable components. Subcritical water technology was used as an environmentally friendly technique to study the extraction of active ingredients and other valuable degradation products from walnut and pistachio waste. Subcritical water extraction (SWE) was carried out under different process conditions (temperature (150–300 ◦C) and short reaction times (15–60 min)) and compared with conventional extraction using different organic solvents (acetone, 50% acetone and ethanol). The extracts obtained from pistachio and walnut shell waste are rich in various bioactive and valuable components. The highest contents of total phenols (127.08 mg GA/g extract at 300 ◦C for 15 min, from walnut shells), total flavonoids (10.18 mg QU/g extract at 200 ◦C for 60 min, from pistachio shells), total carbohydrates (602.14 mg TCH/g extract at 200 ◦C for 60 min, from walnut shells) and antioxidant activity (91% at 300 ◦C, for 60 min, from pistachio shells) were determined when the extracts were obtained via subcritical water. High contents of total phenols (up to 86.17 mg GA/g extract) were also determined in the conventional extracts obtained with ethanol. Using the HPLC method, sugars and their valuable derivatives were determined in the extracts, with glucose, fructose, furfurals (5-hydroxymethylfurfural (5-HMF) and furfural) and levulinic acid being the most abundant in the extracts obtained by subcritical water. The results show that subcritical water technology enables better exploitation of biowaste materials than conventional extraction methods with organic solvents, as it provides a higher yields of bioactive components such as phenolic compounds and thus extracts with high antioxidant activity, while at the same time producing degradation products that are valuable secondary raw materials.
Keywords: pistachio shells, walnut shells, subcritical water extraction, conventional extraction, waste biomass, valuable compounds, sugars, furfurals
Published in DKUM: 01.07.2025; Views: 0; Downloads: 8
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3. Degradation of waste tetra pak packaging with hydrothermal treatment in sub-/supercritical waterMihael Irgolič, Maja Čolnik, Petra Kotnik, Mojca Škerget, 2024, original scientific article Keywords: hydrothermal degradation, waste packing, tetra pak, subcritical water, subcritical waste, chemical recycling, one-stage process, two-stage process, product analysis
Published in DKUM: 16.07.2024; Views: 88; Downloads: 31
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4. Improving decentralized economic growth and reducing energy consumption in the European Union with the application of ecologically oriented innovationsNiko Natek, Boštjan Krajnc, 2020, professional article Abstract: This article presents applicable approaches for supporting the transition towards sustainable decentralized economic development within the European Union, based on the concept of supporting the development and market uptake of eco-innovations. The main topic addressed is achieving a more effective market uptake of ecologically oriented innovations facilitated through matchmaking, as well as knowledge and technology transfer between key actors of the innovation process.
Keywords: Energy efficiency, Ecology, Innovation, Economy, waste-water treatment, constructed wetlands, green-house gas emissions, EU
Published in DKUM: 15.11.2023; Views: 450; Downloads: 268
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5. Kinetics study of hydrothermal degradation of PET waste into useful productsMaja Čolnik, Darja Pečar, Željko Knez, Andreja Goršek, Mojca Škerget, 2022, original scientific article Abstract: Kinetics of hydrothermal degradation of colorless polyethylene terephthalate (PET) waste was studied at two temperatures (300 °C and 350 °C) and reaction times from 1 to 240 min. PET waste was decomposed in subcritical water (SubCW) by hydrolysis to terephthalic acid (TPA) and ethylene glycol (EG) as the main products. This was followed by further degradation of TPA to benzoic acid by decarboxylation and degradation of EG to acetaldehyde by a dehydration reaction. Furthermore, by-products such as isophthalic acid (IPA) and 1,4-dioxane were also detected in the reaction mixture. Taking into account these most represented products, a simplified kinetic model describing the degradation of PET has been developed, considering irreversible consecutive reactions that take place as parallel in reaction mixture. The reaction rate constants (k1–k6) for the individual reactions were calculated and it was observed that all reactions follow first-order kinetics.
Keywords: PET waste, subcritical water, kinetics, degradation, TPA
Published in DKUM: 18.09.2023; Views: 645; Downloads: 237
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6. 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: 124
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7. 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: 164
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8. Kinetic studies of catalytic ozonation of atrazineBrigita Tepuš, Marjana Simonič, 2008, original scientific article Abstract: The aim of our work was to degrade atrazine by the ozone treatment of both a model and the original drinking water samples, using Pt-catalyst, and to evaluate the performance of this catalyst. The rate constant for the reaction of atrazine with ozone was determined in the model water sample. The activation energies and the reaction orders of ozone decomposition were determined in both the model and the drinking water samples. Ozone treatment using Pt-catalyst has some influence on the loss of atrazine in the sources of drinking water. The concentration of some metabolites in the model and drinking water was observed during ozone treatment. The toxicity of atrazine to crustacean Daphnia magna in the original drinking water and in the ozone treated water samples was also assessed.
Keywords: ozone, Pt-catalyst, atrazine, water treatment, waste water, kinetics
Published in DKUM: 05.07.2017; Views: 1352; Downloads: 88
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