Iskanje po katalogu digitalne knjižnice

Opis: The chemical recalcitrance of lignin limits the industrial processing of biomass, which could be addressed by so-called designer lignins. Dehydrogenation polymers (DHPs) formed by artificial lignification of monolignols, enable studies on structure-property relationships independently of genetic information. Thin films of phenolic acid esters of cellulose were prepared and used for quartz crystal microbalance with dissipation monitoring (QCM-D) experiments to investigate surface polymerization in real-time. The phenolic anchor groups significantly influenced lignification speed, deposited mass, and rigidity of resulting DHP layers. Linkage types in the lignin structure were quantified by HSQC NMR spectroscopy. Polymerization efficiency was increased in the order ferulate < p-coumarate < caffeate. Among the tested anchors, protocatechuate groups were excellently performing the reaction, while vanillate and p-hydroxybenzoate led to minimal deposition of DHPs. Lignification behavior could be correlated with radical stability of phenolic anchor groups and the formation of benzodioxane structures of caffeate moieties. The presence of caffeate units that undergo trapping reaction, prevents cross-linking of cell wall components and enhances digestibility. Moreover, the benzodioxane motif increased rigidity and linearity of lignin, which is advantageous for material science applications, e.g. for bio-based carbon fibers.
Ključne besede: artificial lignin, dehydrogenation polymerization, phenolic cellulose esters, QCM-D, thin films
Objavljeno v DKUM: 15.09.2025; Ogledov: 0; Prenosov: 2
Celotno besedilo (1,95 MB)
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Opis: The complex interactions between soil and additives such as lignin, glass powder, and rubber tires were investigated using principles of material and soil mechanics. Previous research has mainly focused on individual additives in clay soils. In contrast, this study investigates soil improvement with two different types of waste materials simultaneously. The improvement of soil properties by hybrid waste materials was evaluated using several laboratory tests, including the standard Proctor test, the unconfined compressive strength test, the California Bearing Ratio (CBR) test, and cyclic triaxial tests. The aim of this research is to identify key parameters for the design and construction of road pavements and to demonstrate that improving the subgrade with hybrid waste materials contributes significantly to the sustainability of road construction. The mechanical and physical properties were evaluated in detail to determine the optimal mixtures. The results show that the most effective mixture for the combination of waste glass powder and rubber tires contains 20% glass powder and 3% rubber tires, based on the dry weight of the soil. For the combination of waste glass powder and lignin, the optimum mixture consists of 15% glass powder and 15% lignin, based on the dry weight of the soil. These results provide valuable insights into the sustainable use of waste materials for soil stabilization in road construction projects.
Ključne besede: soil stabilization, waste glass, tire rubber waste, lignin, hybrid waste usage, mechanical properties, pavement structure
Objavljeno v DKUM: 28.02.2025; Ogledov: 0; Prenosov: 6
Celotno besedilo (5,20 MB)
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Opis: This research focuses on key priorities in the field of sustainable plastic composites that will lead to a reduction in CO2 pollution and support the EU’s goal of becoming carbon neutral by 2050. The main challenge is to develop high-performance polyphenol-reinforced thermoplastic composites, where the use of natural fillers replaces the usual chemical additives with non-toxic ones, not only to improve the final performance but also to increase the desired multifunctionalities (structural, antioxidant, and antibacterial). Therefore, poly (lactic acid) (PLA) composites based on Kraft lignin (KL) and tannin (TANN) were investigated. Two series of PLA composites, PLA-KL and PLA-TANN, which contained natural fillers (0.5%, 1.0%, and 2.5% (w/w)) were prepared by hot melt extrusion. The effects of KL and TANN on the PLA matrices were investigated, especially the surface physicochemical properties, mechanical properties, and antioxidant/antimicrobial activity. The surface physicochemical properties were evaluated by measuring the contact angle (CA), roughness, zeta potential, and nanoindentation. The results of the water contact angle showed that neither KL nor TANN caused a significant change in the wettability, but only a slight increase in the hydrophilicity of the PLA composites. The filler loading, the size of the particles with their available functional groups on the surfaces of the PLA composites, and the interaction between the filler and the PLA polymer depend on the roughness and zeta potential behavior of the PLA-KL and PLA-TANN composites and ultimately improve the surface mechanical properties. The antioxidant properties of the PLA-KL and PLA-TANN composites were determined using the DPPH (2,2′-diphenyl-1-picrylhydrazyl) test. The results show an efficient antioxidant behavior of all PLA-KL and PLA-TANN composites, which increases with the filler content. Finally, the KL- and PLA-based TANN have shown resistance to the Gram-negative bacteria, E. coli, but without a correlation trend between polyphenol filler content and structure.
Ključne besede: poly (lactic acid), Kraft lignin, tannin, multifunctionality of PLA composites, surface mechanical properties, antioxidant/antibacterial activity
Objavljeno v DKUM: 18.09.2023; Ogledov: 495; Prenosov: 209
Celotno besedilo (3,87 MB)
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Opis: The growing concern about the environmental impact and human health risk related to the excessive use of synthetic ingredients in cosmetics and topical formulations calls for the exploration of safe and sustainable natural alternatives. Kraft lignin is a polyphenolic compound generated as a by-product from the kraft pulping process in large quantities annually worldwide. In addition to its commercial availability, its structural features and diverse functional properties make it worth to be considered as a bio‐active ingredient for cosmetic and personal care products. The intrinsic limitations of its native form for the development of high-performance products can be overcome by morphology control through particle size reduction to nanoscale. Therefore, in this research lignin nanoparticles were evaluated for the stabilization of Pickering emulsions. First, a screening of conditions and ingredients was carried out to assess the most suitable parameters for the synthesis of emulsions. The synthesis of final Pickering emulsions was performed using a rotor-stator homogenizer followed by ultrasound. The quality of emulsions stabilized with LNPs were assessed in relation to the emulsification process parameters and ingredients used in the formulation. In generenal, higher concentration of LNPs and volume of oil favoured the emulsion stability. Sun protection factor test showed promising values for application of LNPs in the sunscreen field. We compared the SPF of emulsions prepared with orange, coconut, and paraffin oil. The results showed that emulsion with orange oil had the highest SPF at 16.5, with coconut oil it was 8.8, and the lowest for emulsion with paraffin oil which was 1.7.
Ključne besede: lignin, LNPs, oils, Pickering emulsions
Objavljeno v DKUM: 05.09.2022; Ogledov: 941; Prenosov: 0
Celotno besedilo (6,36 MB)

Opis: Mešanica piščančjega gnoja in žagovine je odpadek, ki nastane pri vzreji piščancev. Uporablja se kot substrat pri proizvodnji bioplina. Kompleksna lignocelulozna zgradba lesa vsebuje lignin, ki mikroorganizmom omejuje dostop do celuloze in hemiceluloze, kar se kaže z nižjo presnovo substrata pri anaerobni digestiji. V diplomski nalogi smo piščančji gnoj in žagovino predobdelali z glivami bele trohnobe, ki smo jih predhodno pustili preraščati na ječmenovi slami. Med preraščanjem gob Trametes versicolor in Pleurotus ostreatus so se v slamo izločili ektoencimi, kot so lakaza in peroksidaza. Ti encimi razgradijo kompleksno strukturo lignina in tako omogočijo mikroorganizmom dostop do celuloze. Anaerobno digestijo smo izvedli pri različnih razmerjih mešanic piščančjega gnoja z žagovino in ječmenove slame preraščene z gobami. Za kontrolo smo uporabili ječmenovo slamo, ki ni bila preraščena z glivo. Posamezen poskus smo izvajali v paru. Fermentorje smo 21 dni vzdrževali pri konstantni temperaturi, ϑ = 42 °C. Prostornino plina, ki je nastal med fermentacijo, smo merili z metodo izpodrinjene tekočine. Koncentracijo nastalega bioplina smo določali z analizo na plinskem kromatografu. Rezultati so pokazali, da se največ bioplina proizvede pri mešanici, ki je vsebovala 50 % specifično predobdelane slame. Nepreraščena slama je pri anaerobni digestiji v vseh razmerjih s piščančjim gnojem proizvedla največ bioplina v primerjavi s slamo preraščeno z gobami. Pet dnevna inkubacija mešanice piščančjega gnoja z žagovino in specifične preraščene slame oziroma navadne slame, se je izkazala za časovno najproduktivnejšo. Ugotovili smo, da vrsta mešanice piščančjega gnoja z žagovino in raznih tipov predobdelane slame, nima očitnega vpliva na koncentracijo metana in ogljikovega dioksida.
Ključne besede: anaerobna digestija, bioplin, lignin, piščančji gnoj, Pleurotus ostreatus, Trametes versicolor
Objavljeno v DKUM: 19.09.2017; Ogledov: 1858; Prenosov: 199
Celotno besedilo (2,46 MB)