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Opis: Ananas je trajnica družine Bromeliaceae, katere plodove konzumirajo po vsem svetu. Velja za eksotično sadje prijetnega okusa in arome, ki se uživa samostojno ali pa se uporablja v različnih produktih. Vendar pa s predelavo ananasa pridelamo tudi velike količine odpadkov, od 25 do 35 % teže sadja, ki lahko povzročajo veliko obremenitev za okolje in onesnaženje. Konvencionalne in nekonvencionalne ekstrakcije so se izkazale kot učinkovite metode za procesiranje odpadkov ananasa. Med nekonvencionalnimi ekstrakcijskimi tehnikami največ zanimanja vzbujajo hidrotermični postopki za procesiranje biomase, saj pri teh postopkih sočasno potekajo reakcije razgradnje odpadne biomase s podkritično vodo in separacijo razgradnih produktov. Podkritična voda se nanaša na tekočo vodo pri temperaturi in tlaku pod kritično točko (Tc = 374,15 ºC, Pc = 22,1 Mpa). Glavni namen magistrske naloge je bil načrtovanje in optimizacija postopka izolacije vrednih spojin iz ananasovih olupkov z uporabo metode odzivinih površin z zasnovo Box-Behnkenovega načrtovanja. Hidrotermično razgradnjo olupkov ananasa smo izvedli pri različnih pogojih, kjer smo spreminjali tri parametre: temperaturo (180, 200, in 220 ºC), čas (15, 30 in 45 min) in razmerje topilo-material (10:1, 20:1 in 30:1 mL/g). Ugotovili smo, da so optimalni pogoji za ekstrakcijo sladkorjev, derivatov sladkorjev, celokupnih ogljikovih hidratov in totalnih fenolov pri temperaturi: 200 ºC, času 30 min in razmerju topilo-material 20:1 mL/g. Največji vpliv na ekstrakcijo vrednih spojin s subkritično vodo imata temperatura in čas, saj se z višanjem temperature ekstrahira večja količina vrednih spojin. Večinoma smo v razgradnih produktih iz odpadnih olupkov ananasa, zaznali visoke vrednosti antioksidativne aktivnosti (od 54,5 do 78 %) ter vsebnosti fruktoze (od 15,10 do 18,20 mg/ g ekstrakta), glukoze (od 14,40 do 18,31 mg/ g ekstrakta) in totalnih fenolov (od 90,50 do 156,90 mg/ g ekstrakta).
Ključne besede: ekstrakcija s subkritično vodo, ananas (Ananas comosus), analiza razgradnih produktov, HPLC, antioksidativnost, derivati sladkorja
Objavljeno v DKUM: 03.03.2025; Ogledov: 0; Prenosov: 9
Celotno besedilo (7,93 MB)

Opis: Corncobs are a widespread and renewable by-product of corn cultivation that are typically considered waste or low-value material. Corncobs contain hemicellulose, cellulose, and lignin, which can be converted into valuable products using suitable techniques. Subcritical water is increasingly used as a green medium for the extraction of valuable components from biomass, as it has many advantageous properties (high yield, pure extracts, shorter times) compared to other organic solvents. For this reason, subcritical water was used in this study to extract valuable components from corncobs at different temperatures (150–250 °C) and reaction times (10–60 min). During the decomposition of corncobs, numerous valuable products are formed in the aqueous phase depending on the temperature and reaction time. In addition to sugars and their derivatives, phenolic compounds were also formed, which are of great importance in numerous applications. It was found that at low temperatures (150–170 °C) the hemicellulose in the corncobs begins to decompose and, in particular, the sugars (glucose, xylose, arabinose, and galactose) are initially formed in the aqueous phase. Higher temperatures (200 and 250 °C) are more favorable for the decomposition of corncobs into valuable components. The yield of sugars increases with temperature due to the degradation of the cellulose content of the lignocellulosic biomass. At the same time, several new valuable products (furfural, 5-hydroxymethylfurfural (5-HMF), 1,3-dihydroxyacetone, levulinic acid, and formic acid as well as phenolic components) are formed through the degradation of lignin and the further degradation of sugars. The most important products are certainly the furfurals, which are central platform compounds. The highest furfural content was reached at 200 °C and 60 min and accounted for almost half of all components in the aqueous phase (472.01 ± 5.64 mg/g dry extract). These biomass-derived sugars and derivatives can be used in the production of fuels, pharmaceuticals, biodegradable polymers, and surfactants.
Ključne besede: corncobs, subcritical water, biomass, valuable compounds, sugar derivates
Objavljeno v DKUM: 07.02.2025; Ogledov: 0; Prenosov: 5
Celotno besedilo (2,41 MB)

Opis: Uporaba plastike v vsakdanjem življenju drastično raste. Z večanjem količine plastičnih izdelkov se sorazmerno povečuje tudi število plastičnih odpadkov, kar predstavlja velik problem z vidika varovanja okolja. Razgradnja plastike v naravnem okolju je zelo počasen proces, zato raziskovalci iščejo metode za razgradnjo plastičnih mas, z namenom pridobitve dragocenih surovin, ki so primerne za nadaljnjo uporabo. Ena izmed pogosteje uporabljenih plastik je tudi polikarbonat (PC), ki se uporablja za proizvodnjo raznih izdelkov. Namen in cilj diplomskega dela je bil raziskati razgradnjo plastike iz PC v podkritični vodi in ugotoviti, katere uporabne produkte lahko pridobimo iz nje. Za proces razgradnje PC smo uporabili visokotlačni in visokotemperaturni šaržni reaktor. Eksperimente smo izvajali pri temperaturi 250 °C in reakcijskih časih 60 in 120 min, medtem ko smo pri temperaturah 300 in 350 °C reakcije izvajali pri 5, 15, 30, 60 in 120 min. Kot produkte hidrotermične razgradnje smo dobili oljno, plinsko, vodno in trdno fazo. Največji izkoristek oljne faze smo dosegli pri 350 °C po 15 min in je znašal 97,7 %. Pri 250 °C je najvišje izkoristke dosegla trdna faza, ki je predstavljala nerazgrajeno plastiko iz PC, zato se je izkazalo, da je temperatura 250 °C prenizka za uspešno razgradnjo. Analize oljne in plinske faze smo izvedli z metodo plinske kromatografije s plamensko ionizacijskim detektorjem (GC-FID), vodnim fazam smo določili totalni ogljik (TC) s TOC analizatorijem medtem ko smo trdne faze analizirali s Fourierjevo transformacijo z infrardečo spektroskopijo (FTIR). V oljni fazi smo določili tri glavne razgradne produkte: bisfenol A (BPA), 4-izopropilfenol in fenol. Maksimalni izkoristek BPA (40,9 %) smo dosegli pri 250 °C in 120 min, kar lahko pripišemo začetni razgradnji PC v glavni monomer BPA. S podaljševanjem reakcijskega časa in z naraščajočo temperaturo je izkoristek BPA upadal, zaradi pretvorbe v nadaljnje komponente (fenol in 4-izopropilfenol). V plinski fazi so bili poleg CO2 prisotni večinoma alkani in alkeni. Z naraščajočo temperaturo in podaljševanjem reakcijskega časa je naraščalo število prisotnih komponent v plinski mešanici, kot posledica razpada daljših ogljikovodikov na krajše. Ugotovili smo, da je hidrotermična razgradnja PC uspešna metoda in predstavlja alternativni pristop recikliranja plastike iz PC, s katerim lahko pridobimo vredne razgradne produkte, ki so primerni za nadaljnjo uporabo.
Ključne besede: hidrotermična razgradnja, polikarbonat, podkritična voda, kemijsko recikliranje, BPA
Objavljeno v DKUM: 18.09.2024; Ogledov: 0; Prenosov: 39
Celotno besedilo (2,70 MB)

Opis: This research showcases the use of hydrothermally extracted solutions from poultry feathers and wool as ecofriendly and versatile textile finishes. These solutions, derived from waste biomass containing the keratin biopolymer, were obtained through environmentally conscious hydrothermal degradation processes. Initially, the study focused on analysing the chemical parameters and properties of both dialysed and non-dialysed solutions extracted from feathers and wool. The investigation tracked primarily the presence of keratin within these solutions. Upon application to polyester textiles as the reference material, the presence of these solutions on the fabric surface was confirmed successfully. A thorough physicochemical analysis of the treated textiles involved various analytical techniques. These encompassed surface composition analysis via X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), assessment of wettability through Contact Angle measurements, determination of surface charge using surface zeta potential, and examination of the thermal and flame-retardant properties via Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and calorimetric tests. In addition, the colour, UV radiation transmission and antioxidant activity were evaluated using standard tests. The remarkable effects of the treatment have been observed in the exceptional antioxidative action, fire resistance, UV protection and enhanced hydrophilicity of these innovative multifunctional textiles. This approach holds significant implications across research, economics and society, enriching Material Science by deepening the understanding of materials and their multifaceted properties. Moreover, it promotes resource efficiency, opens new sustainable textile market prospects, and contributes to social impact by supporting environmental sustainability, engaging communities and ensuring health and safety benefits.
Ključne besede: poultry feathers and wool, hydrothermal extraction, polyester, finishing, green, multifunctionality
Objavljeno v DKUM: 03.09.2024; Ogledov: 43; Prenosov: 18
Celotno besedilo (1,87 MB)
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Opis: Plastics are widely used due to their versatile properties and numerous applications. However, the proper management of plastic waste is a major challenge, even though it is recyclable. The process of repeated recycling can cause the quality of the material to decrease as unwanted contaminants and pollutants increase. This can affect the chemical recycling of plastics at the end of their life and the recovery of secondary products that can be used in other applications. In this study, the chemical degradation of virgin polypropylene (vPP) and recycled polypropylene (rPP) was investigated in supercritical water at a temperature of 450 °C and a reaction time of 15 to 240 min. The oil phase was the primary decomposition product and was obtained in high yield, which reached a maximum after 30 min of reaction time and was 96.9 % for vPP and 94.5 % for rPP. The results of our study show that there are some differences in the product composition depending on which material (vPP or rPP) is chemically recycled.
Ključne besede: virgin polypropylene, plastics, chemical degradation, chemical recycled
Objavljeno v DKUM: 18.04.2024; Ogledov: 235; Prenosov: 5
Celotno besedilo (1,65 MB)
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