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Optimizing the production of biohydrogen with immobilized enriched microbial communities in the plug-flow reactor
Full text linkV zadnjem času se kot procesu z nizko ogljično bilanco posebno pozornost
posveča fermentativni produkciji vodika, s tem, da nizka učinkovitost
pretvorbe substrata v vodik in nezadovoljiva stabilnost procesa v kontinuirnem
režimu obratovanja omejujeta prenos procesa na komercialno raven.
Doktorsko delo je bilo zato usmerjeno predvsem v preučevanje postopkov za
povečanje učinkovitosti procesa anaerobne razgradnje pri razgradnji hitro
razgradljivih organskih substratov. Ugotovili smo, da imajo na produkcijo
vodika velik vpliv številni procesni dejavniki, kot tudi različni načini priprave
inokuluma. Najvišji donos vodika (2,04±0,11 mol H2/mol glukoze) smo
dosegli z izpostavitvijo inokuluma 80 °C za 2 h, pri starosti inokuluma 1 dan,
procesni temperaturi 37 °C, organski obremenitvi 5 g OSglukoze/L in intenziteti
mešanja z Reynoldsovim številom 500. Dosedanje raziskave so usmerjene
predvsem na obratovanje pri pH vrednosti 5,0-7,0, medtem ko so študije
izvedene pri nizkih pH vrednostih zelo redke, čeprav bi bilo obratovanje pri
le-teh tehnološko in ekonomsko ugodnejše. Tako smo pri pH vrednosti
4,0±0,2 z uporabo glukoze kot substrata v reaktorju s čepastim tokom z
različnimi nosilnimi materiali (Mutag BioChipTM, ekspandirana glina in
aktivno oglje) dosegli dolgoročno stabilnost procesa. V reaktorjih z Mutag
BioChipTM, ekspandirano glino in aktivnim ogljem smo dosegli 1,80±0,07,
1,74±0,10 in 1,46±0,09 mol H2/mol glukoze. Visok donos ter stabilno
produkcijo vodika smo pri nizki pH vrednosti ter aktivnem oglju za
imobilizacijo mikroorganizmov dosegli tudi z uporabo odpadne hrane (168,5
NmL H2/g OS). Dolgoročna stabilnost procesa fermentativne produkcije
vodika pri nizki pH vrednosti tako predstavlja pomembno novost v
optimizaciji procesa, saj je obratovanje pri nizki pH vrednosti povezano z
nižjimi stroški obratovanja in manjšimi negativnimi vplivi procesa na okolje.Biohydrogen produced through dark fermentation is currently gaining
importance as biofuel of the future and a potential replacement of fossil fuels.
However, low conversion efficiency of substrate into hydrogen and unstable
hydrogen production during continuous operation mode are limiting largescale
industrial production. Doctoral dissertation was therefore assessing
different techniques in order to enhance the efficiency of fermentative
hydrogen production with degradation of readily biodegradable organic
substrates. We have found out, that numerous environmental factors are
influencing hydrogen production, as well as different inoculum pretreatment
methods. Highest hydrogen yield (2.04±0.11 mol H2/mol glucose) was
achieved in case of thermal pretreatment on 80 °C for 2 h, at inoculum age of
1 day, incubation temperature of 37 °C, organic loading of 5 g OMglucose/L and
mixing intensity with Reynolds number of 500. Previous studies have focused
primarily on the operation in the pH range of 5.0-7.0, while there are less
studies for low pH conditions, which would be however technical and
economic advantage. Our results successfully demonstrated stable dark
fermentation process in plug flow reactor filled with different support
materials (Mutag BioChipTM, expanded clay and activated carbon) at acidic
pH value (4.0±0.2) and glucose as substrate. Obtained hydrogen yields in
reactors filled with Mutag BioChipTM, expanded clay and activated carbon
were 1.80±0.07, 1.74±0.10 and 1.46±0.09 mol H2/mol glucose, respectively.
High yield and stable hydrogen production at low pH value and activated
carbon as support material for immobilization was achieved also with the use
of food waste (168.5 NmL H2/g OM). With achieved stable hydrogen
production process throughout the operation period at low pH values, we
proposed a novel strategy that could contribute to the reduction of financial as
well as environmental costs
Development of nanoplasmonic materials for use in heterogeneous photocatalytic processes
Full text linkTitanov dioksid (TiO2) je dobro uveljavljen fotokatalitski material, zlasti na področju čiščenja vode in zraka. V doktorski disertaciji smo se zato osredotočili na razvoj in optimizacijo plazmonskih fotokatalizatorjev na TiO2 nosilnem fotokatalizatorju, za učinkovito fotokatalitsko razgradnjo onesnažil. Posebno pozornost smo namenili vplivu sinteznih parametrov, morfologiji nosilnega katalizatorja TiO2 ter velikosti, obliki in vrsti plazmonskih kovin na fotokatalitsko aktivnost materialov. Cilj obsežne in sistematične raziskave je bil prispevati k boljšemu razumevanju ključnih dejavnikov, ki vplivajo na lastnosti katalizatorjev ter tako pospešiti razvoj naprednih fotokatalizatorjev za okoljske aplikacije.
V prvem delu raziskav smo se osredotočili na znane Au+TiO2 katalizatorje s tehniko mokre impregnacije, pri čemer smo spreminjali medij (voda ali etanol), čas mešanja in končno temperaturo sinteze. Rezultati so pokazali, da ti parametri močno vplivajo na velikost Au nanodelcev ter posledično na fotokatalitsko aktivnost materialov. Zlati nanodelci so imeli najmanjši premer, ko je mešanje v etanolu potekalo dalj časa, s končnim korakom kalcinacije. Ta vzorec je imel tudi najvišjo generacijo nosilcev naboja in najučinkovitejšo razgradnjo bisfenola A (BPA), kar potrjuje pomemben vpliv sinteznih parametrov na končne lastnosti katalizatorja.
Nadalje smo raziskali vpliv morfologije nosilnega materiala na fotokatalitske lastnosti. Pripravili smo TiO2 v obliki nanopalic (TNR) in nanodelcev (TNP) ter nanje nanesli Au nanodelce. Rezultati so pokazali, da različne morfologije vplivajo na optoelektronske lastnosti materiala. Katalizator TNP+Au je izkazoval večjo sposobnost generacije O2•- radikalov kot TNR+Au, kar je posledica različnih višin Schottkyjeve bariere. Ugotovili smo, da pri razgradnji BPA s TNR+Au ne sodelujejo O2•- radikali, temveč se proces odvija preko interakcije elektronov z molekulami BPA, kar poudarja pomembnost optimizacije Schottkyjeve bariere pri načrtovanju katalizatorjev ter poznavanje mehanizma degradacije onesnažil.
Za raziskavo vpliva morfologije kovine smo preučevali sintezo in karakterizacijo katalizatorjev z morfološko bogatimi delci Au na površini TiO2. Z uravnavanjem količine Na-citrata smo uspeli optimizirati tvorbo pravilno oblikovanih Au nanocvetov. Vzorce smo uporabili za testiranje fotokatalitske aktivnosti pri zmanjšanju NO2 pod vidno svetlobo. Vzorec TNR+NF(0.7) z najbolj definiranimi nanocvetovi se je izkazal z visoko fotokatalitsko aktivnostjo, kar je posledica izrazitega plazmonskega efekta na robovih nanocvetov. Katalizator TNR+NF(1.4) ni pokazal te aktivnosti, kar je pripisano deformiranim nanocvetom in ogljikovim specijam iz Na-citrata. Pri segrevanju na 300 °C so se nanocvetovi spremenili v sferične delce Au, ki niso pokazali fotokatalitske aktivnosti, kar poudarja pomen oblike plazmonske kovine.
V zaključnem delu smo se osredotočili na raziskavo vpliva različnih plazmonskih kovin (Au, Ag, Pt) na lastnosti katalizatorja. Raziskava je pokazala, da izbira plazmonske kovine močno vpliva na učinkovitost prenosa naboja in posledično na aktivnost katalizatorja. Največjo fotokatalitsko aktivnost je izkazoval katalizator TNR-Pt, ki je imel najmanjše nanodelce in najbolj ugodno porazdelitev energijskih pasov. Poskusi razgradnje BPA so potrdili, da so O2•- radikali ključni pri oksidacijskih reakcijah, kjer je bil vzorec TNR-Pt najučinkovitejši.
Celovita karakterizacija sintetiziranih materialov je zagotovila dragocen vpogled na vpliv sinteznih parametrov, morfologije nosilcev, velikosti nanodelcev in izbire plazmonske kovine na fotokatalitsko aktivnost.Titanium dioxide (TiO2) is a well-established photocatalytic material, especially in the fields of water and air purification. In this dissertation, we focused on the development and optimization of plasmonic photocatalysts based on TiO2-supported systems for the efficient photocatalytic degradation of pollutants. Particular attention was paid to the influence of the synthesis parameters, the morphology of the TiO2 carrier and the size, shape and type of plasmonic metals on the photocatalytic activity of the materials. The aim of this comprehensive and systematic research was to contribute to a deeper understanding of the key factors influencing catalyst properties and thus accelerate the development of advanced photocatalysts for environmental applications.
In the first part of the study, we investigated known Au+TiO2 catalysts prepared by the wet impregnation technique, varying the solvent (water or ethanol), the mixing time and the final temperature of the synthesis. The results showed that these parameters significantly affect the size of the Au nanoparticles and consequently the photocatalytic performance of the materials. The smallest Au nanoparticles and the most efficient degradation of bisphenol A (BPA) were obtained using ethanol as a solvent with prolonged mixing and a final calcination step. This sample also exhibited the highest charge generation, confirming the significant influence of the synthesis parameters on the final catalyst properties.
Next, we investigated the influence of the morphology of the support on the photocatalytic properties. TiO2 was synthesized in the form of nanorods (TNR) and nanoparticles (TNP), followed by the deposition of Au nanoparticles. The results showed that different morphologies influence the optoelectronic properties of the materials. The TNP+Au catalyst showed a greater ability to generate O2•- radicals than TNR+Au, which was attributed to differences in Schottky barrier height. We found that BPA degradation with TNR+Au did not involve O2•- radicalsinstead, the process proceeded through the interaction of electrons with BPA molecules, highlighting the importance of optimizing the Schottky barrier and understanding contaminant degradation mechanisms.
To investigate the influence of metal morphology, we synthesized and characterized catalysts with morphologically rich Au particles (nanoflowers) on the surface of TiO2. By adjusting the amount of sodium citrate, we were able to successfully optimize the formation of well-defined Au nanoflowers. These samples were tested for photocatalytic NO2 reduction under visible light. The TNR+NF(0.7) sample with the most pronounced nanoflowers showed high photocatalytic activity due to strong plasmonic effects at the edges of the nanoflowers. In contrast, the TNR+NF(1.4) catalyst showed no activity, which was attributed to the deformed nanoflowers and the presence of carbon species from sodium citrate. When heated to 300 °C, the nanoflowers turned into spherical Au particles, which showed no photocatalytic activity, emphasizing the importance of the plasmonic metal morphology.
In the last part of the research, we focused on investigating the effects of different plasmonic metals (Au, Ag, Pt) on the catalyst properties. The study showed that the choice of plasmonic metal strongly influences the efficiency of charge transfer and thus the activity of the catalyst. The TNR-Pt catalyst showed the highest photocatalytic activity as it had the smallest nanoparticles and the most favorable energy band alignment. BPA degradation tests confirmed that O2•- radicals play a crucial role in oxidative reactions, with TNR-Pt being the most effective sample. The comprehensive characterization of the synthesized materials provided valuable insights into how the synthesis parameters, the morphology of the support, the size of the nanoparticles and the choice of plasmonic metals influence the photocatalytic activity
Hidrotermalna sinteza in strukturna karakterizacija svežih ter toplotno obdelanih titanatnih nanocevk
Full text linkBiometanski potencial trdnega odpadka iz ekstrakcije plodov šipka (Rosa canina L.) s sočasno razgradnjo dodatnega vira dušika
Full text linkHETEROGENA FOTOKATALITSKA OKSIDACIJA ZA ODSTRANITEV BISFENOLA A IZ VODE NA OSNOVI RAZLIČNIH TiO2/GRAFENOV OKSID (GO) NANOKOMPOZITOV
Full text linkSince water is an essential substance for all life on earth, it is therefore vital to prevent its pollution and to improve wastewater purification processes. There is a vast number of pollutants which can contaminate water, of which bisphenol A (known as an endocrine disruptor) is the pollutant studied herein. In this study, several TiO2/GO based nanocomposites with various GO loadings (2, 4, 10, 20 and 40%) and differently shaped nanocrystalline TiO2 phases (titanate nanotubes (TNTs) and calcined titanate nanotubes (TNTs_500)) were synthesised. All of the nanocomposites were characterised through SEM, UV-vis-DR, TGA, BET, FT-IR and CHNS analyses and were used in the heterogeneous photocatalytic degradation of bisphenol A and compared to the activity of pure TNTs and TNT_500 photocatalysts. All TiO2/GO nanocomposites exhibit much better activity than pure TNTs and TNTs_500 catalysts. The conversion of the BPA was analysed using HPLC and the mineralisation was analysed using a TOC analysis. The best experiment was performed with TNTs_500 + 10% GO composite, which can be attributed to the TiO2 crystalline structure obtained. According to the results obtained, TiO2 + 10% GO was found to exhibit the best degradation ratio, which can be ascribed to the fact that excessive GO can act as a charge carrier recombination centre and promotes the recombination of electron-hole pairs in reduced GO.Voda je osnovni vir življenja, zato si moramo prizadevati za njeno čim manjšo onesnaženost in iskati alternative za izboljšanje čiščenja odpadne vode. Škodljivih spojin, ki onesnažujejo vodo, je vedno več. V naši raziskavi smo uporabili BPA, ki je le eden izmed množice teh spojin, znan predvsem kot hormonski motilec. Z različnimi sinteznimi pogoji smo vplivali na modifikacijo in strukturo TiO2 in tako pripravili TiO2 nanocevke (TNTs) in kalcinirane TiO2 nanocevke (TNTs_500). Te smo nato sintentizirali z različno količino grafenovega oksida (2, 4, 10, 20 in 40%). Vse pripravljene nanokompozite smo karakterizirani s SEM, UV-vis-DR, TGA, BET, FT-IR in CHNS analizami ter uporabili v heterogeni fotokatalitski oksidaciji bisfenola A v vodi. Pridobljene rezultate smo primerjali s TNTs in TNTs_500. Izkazalo se je, da vsi pripravljeni nanokompoziti rezultirajo v boljši in hitrejši razgradnji bisfenola A, v primerjavi s TiO2 strukturama. Razgradnjo BPA smo ovrednotili z uporabo HPLC, mineralizacijo pa s TOC analizo. Najboljši rezultat v razgradnji BPA spojine je bil dobljen z uporabo TNTs_500 + 10% GO nanokompozita, kar pripisujemo strukturni obliki TiO2. Rezultati so tudi pokazali, da so najboljši nanokompoziti pripravljeni z 10% GO. Iz tega lahko sklepamo, da je vsebnost 10% GO optimalna. V večjih količinah GO tvori rekombinacijske centre, ki povzročijo padec fotokatalitske aktivnosti in tako počasnejšo razgradnjo BPA spojine
Validacija metode za določanje bisfenola A v izcedni vodi s tekočinsko kromatografijo visoke zmogljivosti
Full text linkStudy of single and multi-metal catalysts on a silica support in advanced oxidation processes for wastewater treatment
Full text linkEna izmed glavnih onesnaževal v odpadnih vodah so strupene organske spojine, katerih količina se z industrijskim razvojem nenehno povečuje. Najbolj nevarna so tako imenovana zaskrbljujoča onesnaževala (CEC – Contaminants of Emerging Concern), med katerimi so najpogostejših farmacevtski izdelki in izdelki za osebno nego. Za učinkovito odstranjevanje le-teh se raziskave osredotočajo na napredne oksidacijske procese (Advanced Oxidation Processes – AOP), ki s pomočjo katalizatorjev in oksidantov organska onesnaževala oksidirajo v ogljikov dioksid, vodo in mineralne kisline. Magistrska naloga se nanaša na proučevanje eno, dvo in trikovinskih katalizatorjev na silikatnem nosilcu. Kovine, ki smo jih proučevali, so bile baker, mangan in železo.
Katalizatorji so bili sintetizirani na Odseku za anorgansko kemijo in tehnologijo na Kemijskem inštitutu. Katalizatorje smo najprej ovrednotili z osnovnimi karakterizacijskimi metodami, kot so rentgenska difrakcija (XRD – X-Ray Diffraction), dušikova fizisorpcija in vrstična elektronska mikroskopija (SEM – Scanning Electron Microscopy). Ugotovili smo, da imajo višjo vsebnost kovin skoraj vsi kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji, kar lahko pripišemo ekstrakcijskemu postopku, med katerim se najverjetneje odstrani določeno množino kovin iz katalizatorjev. Postopek priprave bistveno ne vpliva na specifično površino, velikost por in volumen por katalizatorjev. Pri kalciniranih katalizatorjih, ki vsebujejo Cu, je le-ta prisoten v obliki CuO.
Katalitske teste sem izvedla na dveh modelnih onesnaževalih iz skupine CEC in sicer na kumarinu (Fenton in foto-Fenton AOP) in glifosatu (Fenton AOP). Ugotovila sem, da so v primeru obeh uporabljenih modelnih onesnaževal najbolj učinkoviti dvokovinski katalizatorji in sicer pri kumarinu katalizator s Cu in Mn ter pri glifosatu katalizator s Cu in Fe. Pri kumarinu katalizator s Cu in Mn kaže tudi na fotokatalitsko aktivnost pri obsevanju z vidno svetlobo. Prav tako sem ugotovila, da so tako kot pri kumarinu tudi pri glifosatu bolj učinkoviti kalcinirani katalizatorji v primerjavi z ekstrahiranimi in kalciniranimi katalizatorji. To lahko pripišemo višji vsebnosti kovin ali/in prisotnosti Cu specij v obliki CuO v kalciniranih katalizatorjih. To ugotovitev bi bilo potrebno v nadaljevanju podrobneje raziskati.One of the most important wastewater pollutants are toxic organic compounds, whose emissions continue to increase with industrial development. The most dangerous are the so-called Contaminants of Emerging Concern (CEC), which mainly include pharmaceuticals and personal care products. To effectivelly eliminate CEC, research focuses on advanced oxidation processes (AOP), which use catalysts and oxidants to oxidize organic pollutants to carbon dioxide, water, and mineral acids. The present master thesis refers to the investigation of single, double, and triple-metal catalysts on a silicate support. The metals studied are copper, manganese and iron.
The catalysts were synthesized in the Department of Inorganic Chemistry and Technology at the National Institute of Chemistry, Ljubljana, Slovenia. The catalysts were first studied using basic characterization methods such as X-ray diffraction (XRD), nitrogen physisorption, and scanning electron microscopy (SEM). We found that almost all calcined catalysts have a higher metal content than extracted and calcined catalysts. This can be attributed to the extraction process which most likely removes a certain amount of metals from the catalysts. The preparation process has no significant influence on the specific surface area, pore size and pore volume of the catalysts. In the calcined catalysts containing copper, copper is present as CuO.
I carried out catalytic tests with two model pollutants from the CEC group: Coumarin (Fenton and photo-Fenton AOP) and Glyphosate (Fenton AOP). I found that for both model pollutants, the most effective catalysts were the two-metal catalysts, namely the Cu-Mn catalyst for coumarin and the Cu-Fe catalyst for glyphosate. For coumarin, the Cu-Mn catalyst also shows photocatalytic activity when irradiated with visible light. As with coumarin, the calcined catalysts are also more effective for glyphosate than the extracted and calcined catalysts. This may be attributed to the higher metal content and/or the presence of Cu species in the form of CuO in the calcined catalysts. This finding should be investigated further
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