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S povečevanjem količine farmacevtikov v odpadnih vodah so se pojavile skrbi zaradi vplivov na okolje. Ker se je klasično biološko čiščenje izkazalo kot neuspešno za njihovo odstranjevanje, so se raziskave osredotočile na sklopitev biološkega čiščenja z naprednimi oksidacijskimi metodami, med katere spada tudi fotokatalitska razgradnja. Eden od procesov, ki fotorazgradnjo spremlja, je adsorpcija. Z namenom boljšega vpogleda v fotodegradacijo sem se v svoji diplomi osredotočil na razumevanje procesa adsorpcije. Za adsorbata sem izbral fenitoin in oksitetraciklin, ki se v odpadnih vodah pogosto pojavljata v relativno visokih količinah in hkrati nista zelo raziskana. Kot fotokatalizator sem raziskoval nanodelce ZnO, ki kažejo obete zaradi primerne energije prepovedanega pasu in relativno majhne škodljivosti za okolje. Diplomsko delo obsega karakterizacijo ZnO, študij kinetike in termodinamike adsorpcije obeh farmacevtikov na ZnO ter računalniške simulacije elektronske gostote po površini molekul. Ugotovil sem, da so v suspenziji nanodelci prisotni v obliki poroznih 500 nm aglomeratov z nekoliko pozitivno nabito površino. Adsorpcija obeh farmacevtikov spada v fizisorpcijo, ki je verjetno osnovana na elektrostatskih interakcijah. Ugotovil sem, da je adsorpcija na površino aglomeratov zelo hiter proces, medtem ko je difuzija in adsorpcija v pore veliko počasnejša. Fenitoin se adsorbira le na površino aglomeratov, medtem ko oksitetraciklin lahko vstopa tudi v pore ZnO. With the increase in the amount of pharmaceuticals in wastewater, concerns have arisen about the impact on the environment. As traditional biological treatment proves unsuccessful for their removal, research has focused on combining biological treatment with advanced oxidation methods, including photocatalytic degradation. One of the processes that accompanies photodegradation is adsorption. To gain better insight into photodegradation, the research was focused on understanding the adsorption process. Phenytoin and oxytetracycline were chosen as adsorbates because they are found in relatively high amounts in wastewater and at the same time are not very well researched. ZnO nanoparticles were explored as photocatalyst as they are promising due to sufficient band gap energy and relatively low environmental toxicity. The work was based on the experiments on the characterization of ZnO, the study of the kinetics and thermodynamics of adsorption of both pharmaceuticals on ZnO, and computer simulations of the electron surface potential of molecules. It was found that the nanoparticles in suspension are in the form of porous 500 nm agglomerates with a slightly positively charged surface. The adsorption of the two pharmaceuticals belongs to physisorption, which is probably due to electrostatic interactions. It was found that adsorption on the surface of the agglomerates is a very fast process, while diffusion and adsorption into the pores are much slower. Phenytoin is adsorbed only on the surface of the agglomerates, while oxytetracycline can also penetrate into the pores of ZnO.

With the increasing focus on the use of lithium-ion (Li-ion) batteries in automotive applications, the need for simulating or mimicking the electrochemical and thermal performance of the battery is of great interest. In this master's thesis, the detailed description of electrochemistry and electrochemical modelling is presented, with the importance of many parameters used in electrochemical modelling along with investigating its sensitivity.\ In thesis, the general description and analysis of electrochemical models are done, where the evaluation is based on their ability to simulate a complex electrochemical behaviour inside the cell. The base of electrochemical modelling is open-source code named Dualfoil. It was carefully studied in order to understand electrochemical modelling and how it can be manipulated to achieve desired goals. Dualfoil, last updated in 2014, was used to evaluate the models' accuracy and assessment of which parameters or inputs are the most sensitive ones for a specific type of battery. \ The thesis aims to understand the detailed chemical structure and properties of Li-ion battery cell such as type of battery cell, active materials used for cathode and anode, battery housing, main or side reactions, etc. Aside from simulation work, various measurements were performed in order to characterize the commercially available battery cells chemically. \ Leta 1991 se je na področju baterij zgodila revolucija, Sony je predstavil prvo litij-ionsko baterijo, ki je dosegla neprimerljivo višjo kapaciteto v primerjavi s klasičnim svinčevim ali nikelj-metal hidridnim akumulatorjem. Po 30 letih je jasno, da je del prihodnosti cestnega prometa električni pogon, saj zagotavlja ničelni operativni ogljični odtis. Baterije so postale ključna komponenta prenosnih elektronskih naprav (pametni telefoni, tablični računalniki ipd.), medicinskih naprav (srčni spodbujevalniki, inzulinske črpalke ipd.), shranjevalnikov električne energije ("off-grid" sistemi) in prevoznih sredstev (e-avtomobili, e-tovornjaki, e-skiroji, e-kolesa ipd.). Razvoj novih ali izboljšanje že obstoječih baterij združuje znanstvenike različnih strok mikropogled na baterijo pojasnjuje kemija in fizika, medtem ko makropogled elekrotehnologija in strojništvo. Poleg baterij vir električne energije predstavljajo tudi gorivne celice in superkondenzatorji, ki šele v zadnjih letih pridobivajo veliko pozornosti s strani energetike za pridobivanje in shranjevanje električne energije. Da lahko baterije postanejo resnično aplikativne in uporabne v prevoznih sredstvih, je potrebno znati napovedati njihovo življenjsko dobo in uporabnost. Prav ena izmed nalog elektrokemijskega modeliranja litij-ionskih baterij je napoved življenjske dobe baterije glede na njeno kemijsko sestavo. \ Trenutno so baterije, natančneje sekundarne litij-ionske baterije, najpogostejši prenosni vir energije. Trend uporabe litij-ionskih ali litij-polimernih baterij v avtomobilski industriji je povzročil veliko zanimanja za razumevanje in izboljšanje tega alternativnega sistema. S simuliranjem elektrokemijskega in termičnega delovanja baterij je omogočen razvoj že obstoječih in novih baterij za dosege večje kapacitete, daljše življenjske dobe, manjše porabe, manjše upornosti itd. V predstavljeni magistrski nalogi je podroben opis elektrokemije in elektrokemijskega modeliranja litij-ionskih baterij, kjer evalvacija temelji na njihovi sposobnosti simuliranja kompleksnega elektrokemijskega obnašanja znotraj baterijske celice s fizikalno-kemijskimi enačbami. Komercialno dostopni elektrokemijski modeli običajno temeljijo na splošno dostopni kodi Dualfoil, predstavljeni leta 1995 cite{Doyle1993}. Na spletni stani enega izmed izumiteljev elektrokemijskega modela Johna Newmana je bila zadnja posodobitev kode izvedena v letu 2014. Uporabnik lahko kodo uporabi, preuči in manipulira za doseganje svojega cilja. \ textbf{Namen in zasnova magistrskega dela} Cilj dela je razumeti podrobno kemijsko strukturo, lastnosti in procese v litij-ionskih baterijah, s pridobljenim znanjem analizirati elektrokemijski model Dualfoil, preučiti številne parametre in njihov vpliv na elektrokemijsko modeliranje ter na podlagi osnovnega elektrokemijskega modela analizirati komercialne elektrokemijske modele. Za izboljšanje modelskih napovedi za baterijske procese je bil izveden eksperimentalni del, katerega namen je bil opraviti in oceniti težavnost meritev nekaterih ključnih parametrov za točnost modelov.\ Za dosego cilja magistrske naloge sem delo razdelila na tri glavnine. \ Prvi del naloge je namenjen natančnemu študiju elektrokemije v galvanskem členu in analizi komercialnih elektrokemijskih modelov. Sledi preučitev in primerjava osnovnega elektrokemijskega modela Dualfoil a komercialnimi modeli AVL FIREtextsuperscript{TM} M, Siemens STAR-CCM+ in Siemens Battery Design Studio. Vsi omenjeni komercialni modeli temeljijo na modelu Dualfoil in vsebujejo dodatne modifikacije in nadgradnje. \ Drugi del je namenjen identifikaciji najpomembnejših parametrov v elektrokemijskem modelu Dualfoil za modeliranje LCO (litij kobaltov oksid) baterije in LMO (litij manganov oksid) baterije. Na podlagi rezultatov sledi karakterizacija vplivnosti in občutljivosti parametrov na točnost modela oceni oziroma napove se ključne parametre pri staranju baterije. \ Zadnji del je namenjen določitvi merljivosti parametrov, potrebnih za elektrokemijsko modeliranje. Parametri so bili na podlagi študija literature razdeljeni v tri kategorije: merljivi, preračunljivi ali predvideni parametri. Nekaj merljivih parametrov smo poizkusili določiti tudi z analizo treh komercialnih baterijskih celic. Na vseh celicah je bila opravljena elektrokemijska analiza, medtem ko smo izbrali zgolj cilindrično baterijo za kemijsko karakterizacijo. \ textbf{Litij-ionska baterija} \ Baterija je naprava za shranjevanje elektrokemijske energije, saj shranjuje kemično energijo v aktivnih materialih in jo pretvori v električno z elektrokemijsko redoks reakcijo. Poznamo dve kvalifikaciji baterij, primarno in sekundarno. V primarni sistem baterij spadajo baterije, ki se jih lahko izprazni zgolj enkrat gre za ireverzibilni proces (npr. alkalne suhe baterije). Za sekundarne baterije so značilni reverzibilni procesi, v okviru katerih lahko z zunanjim virom ponovno napolnimo baterijo (npr. Li-ion baterije). Sekundarne baterije, ki imajo trdni elektrodi ter tekoč elektrolit, so sestavljene iz: begin{itemize} item negativne elektrode ali anode tu poteka spontana reakcija oksidacije, item pozitivne elektrode ali katode tu poteka spontana reakcija redukcije, item separatorja, ki fizično loči katodo od anode in s tem prepreči nastanek kratkega stika, item elektrolita, ki deluje kot medij za prenos naboja med anodo in katodo, item različnih dodatkov ali aditivov, ki so namenjeni za izboljšanje prenosa naboja, doseganje večje kapacitete, večje stabilnosti itd. end{itemize} Pri baterijah je izbira materialov in njena zasnova tesno povezana z namenom izpolnitve sistemske zmogljivosti baterije. Prav tako tudi različne standardizirane oblike baterije zahtevajo komponente, prilagodljive tem oblikam (cilindrična, ploščata, prizmatična in gumbna). \ Visokoenergetska baterijska celica je sestavljena iz debelejših materialov tako omogočijo shranjevanje več energije. Debele elektrode zmanjšajo hitrost pretvorbe elektrokemijske energije v električno energijo, na podlagi česar postanejo celice manj odzivne na dinamične obremenitve. Hkrati so te baterije primernejše za uporabo v sistemih BEV (baterijska električna vozila) in PHEV (priključna hibridna električna vozila), ker dosežejo velike kapacitete in imajo boljšo zmogljivost praznjenja. Celica z veliko močjo ima tanjše elektrode z večjo poroznostjo in s tem večjo hitrost pretvorbe energije, zaradi česar je celica odzivna na različne obremenitve kljub nižji energijski gostoti. Uporabljajo se v sistemih HEV (hibridna električna vozila) kot pomožni modeli za moč. \ textbf{Modeliranje baterij z uporabo matematičnih modelov} \ Z leti so raziskovalci razvili različne modele, s katerimi bi lahko napovedali zmogljivost in življenjsko dobo baterije. Večina modelov upošteva pri napovedovanju življenjske dobe zgolj porabo energije, ne pa tudi vzorca uporabe in obremenitve baterije. Baterijski modeli so zasnovani na različnih filozofijah napovedovanja obnašanja v baterijski celici cite{Jongerden2009}: begin{itemize} item elektrokemijski model, item model z električnim vezjem, item analitični model, ki temelji na teoriji Peukerta ali Rakhmatova, item kinetični baterijski model, item stohastični model, ki temelji na teoriji Chiasserinija, item stohastično-kinetični model. end{itemize} Elektrokemijski modeli temeljijo na podrobno opisanih kemijskih procesih znotraj baterijske celice in zahtevajo dobro poznavanje elektrokemije in kinetike v celici. Pionirsko delo na tem področju je bilo opravljeno s strani treh znanstvenikov (Doyle, Fuller in Newman), ki so razvili elektrokemijski model za litijeve in litij-ionske celice cite{Doyle1993, Fuller2006, Doyle1995}, teorijo makrohomogene porozne elektrode pa Newman cite{Newman75}. Njihov model je sestavljen iz šestih glavnih nelinearnih enačb, ki kot rezultat podajo datoteko z naslednjimi spremenljivkami: napetost in tok kot časovno funkcijo, potencial, koncentracijo soli, reakcijsko hitrost in gostoto toka kot funkcijo časa in položaja v celici cite{Albertus2007}. \ Newman-Doyle-Fuller ali Dualfoil model cite{Albertus2007} je zelo natančen, ampak tudi kompleksen, saj je potrebnih okoli 60 parametrov. Veliko teh parametrov, potrebnih za modeliranje je znanih le razvijalcem ali proizvajalcem baterij. Dualfoil spada med pseudo-dvo-dimenzionalne (P2D) elektrokemijske modele, saj model enodimenzionalno (x-os) predstavlja prenos mase in naboja v elektrodah in elektrolitu dvodimenzionalno (r-os in x-os) je opisana difuzija litija v elektrodah. \ V Dualfoil modelu je izvedenih veliko predpostavk za matematično poenostavitev elektrokemijskega obnašanja baterijske celice nekatere izmed teh so: begin{itemize} item med interkalacijo se elektrode ne povečajo (ang. textit{swelling}), item ni konvekcije med masnim transportom v elektrolitu, item elektrolit je razredčen, item enakomerna toplotna in tokovna porazdelitev, item prenos naboja je opisan z Butler-Volmerjevo enačbo, item transport iona znotraj elektrolita je opisan s teorijo koncentrirane raztopine, item elektroda je sestavljena iz monodisperznih sferičnih delcev. end{itemize} Zaradi kompleksnosti meritev je zgolj nekaj raziskav usmerjenih k pridobitvi vseh merljivih parametrov za elektrokemijski model. Med magistrsko nalogo je bilo ugotovljeno, da je večina uporabljenih parametrov v modelih, pridobljenih iz literature, predpostavljenih ali ocenjenih. Zato smo izbrali osnovne parametre za modeliranje zgolj iz študij, kjer so bili ti izmerjeni ali pa ocenjeni na podlagi eksperimentalnih podatkov. \ V nalogi smo se osredotočili predvsem na litij kobaltov oksid (LCO) in litij manganov oksid (LMO), čeprav se današnje litij-ionske tehnologije in avtomobilska industrija izogibajo uporabi kobalta. Razlog je v tem, da je bilo do sedaj največ raziskav in študij izvedenih na LCO ali LMO baterijah ter sta ti dve kemiji izbrani zaradi preverljivosti informacij. Današnje raziskave so usmerjene h katodni tehnologiji nikelj mangan kobalt (NMC) in k povečevanju kapacitete grafitne anode z dodatkom silicija ali silicijevega oksida, ki omogoča interkalacijo več litijevih ionov. Pri vseh omenjenih sistemih je še veliko tehnoloških težav in veliko parametrov ostaja nedoločljivih z eksperimentalnimi metodami.

Due to many advantageous physiochemical properties, titanium dioxide (TiO2) is the most widely used photocatalyst in numerous applications, such as wastewater treatment and air purification, self-cleaning surfaces and energy conversion (H2 generation). However, one of its disadvantages is the high electron-hole recombination rate, and coupling with other semiconductors is one of the strategies to improve it. The objective of this dissertation was to investigate how the photocatalytic activity of pure TiO2 can be improved by tin modification and to explain the mechanism of increased or hindered photoactivity in correlation with the structural properties of the modified TiO2 photocatalysts. A new low-temperature sol-gel synthesis route was developed to prepare Sn- or SnO2-modified TiO2 photocatalysts. In both cases, organic tin and titanium precursors were used. Tin in the form of Sn cations was used to prepare Sn-modified TiO2. In this case, the precursors went through the sol-gel reaction together to form a Sn-TiO2 sol. In the case of SnO2 modification, the SnO2 sol was prepared separately and additionally mixed with the TiO2 sol to form a TiO2/SnO2 bicomponent semiconductor system. Different molar ratios of tin to titanium were prepared to investigate the correlation between the tin concentration and the photocatalytic properties of the photocatalysts in the form of thin films. The results were used to optimize the synthesis conditions to obtain an improved activity of the modified TiO2 photocatalysts under UV-irradiation. The photocatalytic activity of the thin films was determined by measuring the degradation rate of an azo dye. An increase of up to 40 % in the photocatalytic activity of the dried samples (at 150 °C) was achieved when the TiO2 was modified with the Sn or SnO2 in a concentration range of 0.1 to 1 mol.%. At higher Sn or SnO2 loadings and after calcination of the samples at 500 °C, the photocatalytic activity of the photocatalyst was reduced compared to the unmodified TiO2. Different characterization techniques (UV-Vis, XRD, nitrogen physisorption, TEM, SEM and XAS) were employed to clarify the mechanism responsible for the enhanced and hindered photocatalytic performance of the Sn- and SnO2-modified TiO2 photocatalysts. The results showed that a nanocrystalline structure is already achieved in the samples by the low-temperature film treatment (drying at 150 °C) and that the photocatalytic efficiency is mainly influenced by the crystalline phase composition: anatase/rutile in the case of Sn-modified and TiO2/SnO2 in the case of SnO2-modified TiO2. The crystal size and specific surface area differ insignificantly between the equally thermally treated samples and partly explain the differences in photoefficiency of the calcined samples compared to the dried samples. The structural study at the atomic level, using the Sn K-edge EXAFS, revealed that Sn cations act as nucleation sites for the anatase to rutile transformation in the Sn-modified TiO2 photocatalysts, while in the SnO2-modified TiO2 samples the nanocrystalline cassiterite SnO2 is bound to the TiO2 nanocrystallites via the Sn-O-Ti bond. In both cases, the advantage of coupling the two semiconductors was achieved by separating the charge carriers and thus prolonging their lifetime for accessibility to participate in the redox reactions. The maximum activity enhancement was achieved in the low concentration range (0.1–1 mol.%), which means that an optimal ratio and contact of the two phases are obtained for the given physical parameters, such as particle size, shape and specific surface area of the catalyst.

Namen diplomskega dela je bil sintetizirati učinkovit katalizator na osnovi cerijevega dioksida z uporabo hidrotermalne metode. Katalitično delovanje sem nameravala preizkusiti pri sintezi propilen karbonata brez topil, z reakcijo cikloadicije propilen oksida in CO2, ki ga je v naravi v obilju in sodi med toplogredne pline. Zaradi pandemije Covid-19, načrtovanega laboratorijskega dela nisem mogla izvesti in sem zato diplomsko delo usmerila v teoretično obravnavo navedene teme. Analizirala sem nekaj že izvedenih in objavljenih okolju prijaznih sintez propilen karbonata. Primerjala sem različne katalizatorje in njihove lastnosti, ki so jih avtorji znanstvenih člankov določili z različnimi analitskimi tehnikami. The aim of this work was the synthesis of an effective catalyst based on cerium dioxide using the hydrothermal method. The catalytic activity would be tested in the synthesis of solvent-free propylene carbonate by the cycloaddition reaction of propylene oxide and CO2, which is abundant in nature and belongs to the greenhouse gases. Due to a pandemic Covid-19, I was not able to carry out the planned laboratory work, so I oriented my thesis on the theoretical treatment of this topic. Thus, I analyzed some already performed and published environmentally friendly syntheses of propylene carbonate. I compared different catalysts and their properties determined by the authors of the scientific articles using various analytical techniques.

Svetovno pomanjkanje vode predstavlja velik izziv sodobni družbi. Potencialen vir vode predstavlja ponovna uporaba odpadne vode, vendar jo moramo pred uporabo prečistiti. Ker so nekatera onesnažila zelo trdovratna, jih je nemogoče odstraniti s konvencionalnimi metodami, zato se je treba obrniti k naprednim oksidacijskim metodam. V tej diplomski nalogi sem raziskala eno izmed njih – polprevodniško fotokatalizo. Sintetizirala sem tri vrste raztopin z nanodelci TiO2 za nanos na milimetrske granule ter testirala njihovo fotokatalitsko aktivnost. Preizkusila sem proces žganja granul z nanosi. Testirala sem vpliv prepihovanja vzorca s kisikom na aktivnost fotokatalizatorja. The global water shortage is a challenge for modern society. Wastewater could be used as a potential source of water, but it must be properly treated before it can be used. Due to the persistence of some pollutants, advanced oxidation processes may be used in parallel with conventional water treatment processes. The aim of this work was to test one of the advanced oxidation processes - semiconductor photocatalysis. I synthesised three types of solutions with titania nanoparticles to coat millimetre-sized granules and test their photocatalytic activity. I also tested the process of thermal treatment of the granules with the coating. The influence of oxygen purging during the photocatalytic measurements was also tested.

Tekom diplomskega dela sem pripravila sol titanovega dioksida po anorganski sintezni poti iz TiCl4 z dodatkom NH4NO3 in hidroksipropil celuloze. Z dušikom dopirane fotokatalitsko aktivne tanke plasti sem pripravila tako, da sem nastali sol s tehniko potapljanja podlage nanesla na objektna stekla in jih nato termično obdelala pri temperaturi 600 °. Nastale plasti sem uporabila za fotokatalitsko razgradnjo antibiotika oksitetraciklina pod UV svetlobo z valovno dolžino 350 nm. Razgradnjo antibiotika sem spremljala spektrofotometrično na 15 minut celotni čas fotokatalitske razgradnje pa je bil 3 ure. Razgradnjo onesnažila v vodovodni in deionizirani vodi sem spremljala na osnovi meritev absorpcijskih spektrov učinkovine v območju med 200 in 800 nm. Opazovala sem vpliv pH raztopine in začetne koncentracije onesnažila na hitrost razgradnje. Naredila sem tudi umeritvene krivulje oksitetraciklina v deionizirani in vodovodni vodi, iz katerih lahko iz izmerjene absorbance pri valovni dolžini 355 nm (deionizirana voda) oziroma 375 nm (vodovodna voda) določamo koncentracijo oksitetraciklina v raztopini. Iz meritev absorbcijskih spektrov teh raztopin pred in po triurnem osvetljevanju z UV svetlobo sem lahko določila še spontano razgradnjo oksitetraciklina na UV svetlobi. During my diploma work, titanium dioxide sol was prepared by inorganic synthesis route from TiCl4 with addition of NH4NO3 and hydroxypropyl cellulose. The prepared sol was deposited onto object glasses by dip-coating technique. After thermal treatment at 600 °C nitrogen-doped photocatalytically active thin films were prepared. These layers were then used for the photocatalytic degradation of the antibiotic oxytetracycline under UV light irradiation with a wavelength of 350 nm. The antibiotic degradation was measured spectrophotometrically every 15 minutes the total time of photocatalytic degradation was 3 hours. The degradation of the contaminant in tap water and deionized water was monitored, based on the obtained absorption spectra of the active substance in the range between 200 and 800 nm. The influence of the pH of the solution and the initial concentration of the contaminant on the degradation rate was investigated. Calibration curves of oxytetracycline in deionized water and tap water were also constructed, from which the concentration of oxytetracycline in the solution can be determined from the measured absorbance at a wavelength of 355 nm (deionized water) and 375 nm (tap water). From the absorption spectra of these solutions before and after irradiation with UV light for three hours, the spontaneous degradation of oxytetracycline in UV light can also be followed.

Iz titanovega tetraklorida sem sintetizirala tridimenzionalne rožicam podobne mikrodelce TiO2, ki sem jih uporabila za pripravo treh različnih suspenzij. Suspenzije sem v različnem številu slojev nanesla na steklene ploščice in jih termično obdelala. Ploščice sem nato uporabila za fotokatalitsko razgradnjo barvila Plasmocorinth B v šaržnem reaktorju s svetlobo z valovanjem v območju ultravijoličnega spektra pri različnih pogojih. Fotokatalitsko razgradnjo barvila sem preverjala z merjenjem absorbance vzorcev s spektrofotometrom. Z vrstičnim elektronskim mikroskopom smo posneli ploščice z nanosi za podrobnejši vpogled v površino in strukturo nanosov suspenzije. Rezultati so pokazali, da se je za najboljše vezivno sredstvo izkazal polivinilpirolidon, saj je suspenzija s tem dodatkom v obliki plasti po termični obdelavi najhitreje razgrajevala barvilo. Razgradnjo barvila so dodatno pospešili trije nanosi suspenzije in prepihovanje vodne raztopine barvila s kisikom. Titanium tetrachloride was used as a precursor for the synthesis of three-dimensional flower-like TiO2 microparticles, from which three different suspensions were further prepared. The suspensions were deposited in a different number of layers to the glass slides, which were then heat-treated. The prepared plates were used for the photocatalytic degradation of Plasmocorinth B in a batch reactor under UV light and under different conditions. The photocatalytic degradation of the dye was checked by measuring the absorption of the samples with a spectrophotometer. A detailed insight into the morphology and structure of the photocatalyst was obtained with the scanning electron microscope. The results showed that polyvinylpyrrolidone proved to be the best binder as the resulting suspension in the form of layers and after heat treatment degrades the dye the fastest. The degradation of the dye was also accelerated by three layers of the suspension deposited on the glass slides and by purging the aqueous dye solution with oxygen.

Diplomsko delo sodi v širši problem pomanjkanja pitne vode, ki bo z naraščanjem prebivalstva in posledično vedno večjo porabo in osnaženostjo vode postal še večji. V delu je predstavljena rešitev čiščenja vode z uporabo fotokatalizatorja na osnovi bakrovega oksida. Veliko je že obstoječih načinov čiščenja vode, ampak zaradi edinstvenih lastnosti predstavlja bakrov oksid odlično alternativo že uveljavljenim katalizatorjem. V teoretičnem delu sem se osredotočil predvsem na to, kako fotokatalizator izboljšati, da dosega svoj maksimum. V eksperimentalnem delu je opisana priprava učinkovite imobilizacije bakrovega oksida na pelete aluminijevega oksida, ki služijo kot nosilec. Učinkovitost oksidacije sem preveril na organskem barvilu Plasmocorinth B. Opisana sta tudi reaktorja, ki sta bila uporabljena za koriščenje bakrovega oksida pri odstranjevanju tega onesnaževala v vodi. Nanostrukturo bakrovega oksida smo si podrobneje ogledali z vrstičnim elektronskim mikroskopom, ki je pokazal majhne delce in s tem veliko površino. Diploma thesis falls in the area of water shortage problem. This problem will only keep getting worse because of population growth. The solution to the problem can be CuO photocatalyst. There are many already existing processes for water purification, but copper oxide is an excellent alternative to the already established catalysts, because it provides some unique characteristics. In the theoretical part of the thesis, I focused on ways how to make a better photocatalyst and to achieve its maximum. The experimental part contains a description of efficient immobilization of CuO on aluminium oxide pellets. I tested the effect of photooxidation on organic dye Plasmacorinth B contaminant in aqueous solution. Description of both types of reactors used in testing are included. I examined copper oxide nanostructure with the help of scanning electron microscope. The image with high magnification showed small particles and large surface area.

This work entitled «Zr/Cu-TiO2 catalysts for photocatalytic water treatment» tackles a problem of tons of dyes discharged everyday mainly from textile industries. This is a huge concern because of dyes persistence, toxicity and potential to the bioaccumulation in living organisms. Here, a small contribution to overall problem is presented. The research work consists of three main parts: Theoretical background, Experimental and Results and discussion. In the Theoretical background chapter the overall problem is identified and discussed. The main water treatment techniques are presented briefly with their advantages and drawbacks. Photocatalysis assisted with TiO2 is shown as an alternative additional technique with its own pros and cons. Further, a cursory overview of TiO2 modification techniques is made and advantages in using copper and zirconium oxides for TiO2 modification are presented. The reason and possible positive effect of using of two oxides simultaneously for TiO2 modification is indicated. Additionally, a positive impact of solar light for overall rate of dyes degradation assisted with TiO2 is discussed. Within the framework of photosensitization effect, the problem of using dyes for assessment of photocatalytic properties of materials under the visible light is touched on. Photothermal methods as possible beneficial techniques for this purpose are proposed. In the Experimental chapter, all experimental techniques used in current research work with the technical details specific for the research work are presented. There are methods of materials preparation, photocatalytic tests under different conditions and varying model pollutants, and physico-chemical characterization techniques. The Results and discussion chapter is divided by three subchapters. Each chapter is dedicated to one hypothesis, which was checked and confirmed or disproved. The first hypothesis is about beneficial loading of copper and zirconium oxides to TiO2. After numerous experiments held, it was concluded that the pair of copper and zirconium oxides is beneficial for simultaneous application on TiO2 surface to promote its performance. The second subchapter is about zirconium distribution and its impact on the activity of studied materials towards the antraquinone dye Reactive Blue 19. Different techniques such as XRD, TEM, EXAFS and many others were used in order to characterize the materials and to understand the details of the processes taking place. The existence of upper limit of copper oxide loading for its beneficial effect on TiO2 performance was demonstrated. It was observed that zirconium species loading leads to improvement in performance of materials with higher copper loading, which otherwise lowers activity of TiO2 – this is in case when copper only above its optimal level is present. It was concluded that zirconium oxide containing species occupy rutile surface sites in mixed phase TiO2 and this way beneficially influence the material performance towards the dye removal. The third subchapter is about the visible light TiO2 assisted dye degradation. It is well known that photosensitization mechanism of dye degradation appears under the visible and as a consequence under the solar light irradiation. This leads to the overall enhancement of dyes degradation, which is positive and may be used as a benefit for faster pollutant destruction. However, this fact leads to mishmash in the determination of real photocatalytic activity of materials towards the dye. It was hypothesized that the impact of photosensitization mechanism on the overall material performance against Reactive blue 19 dye (RB19) descends with the dye concentration lowering. Thermal lens spectrometry (TLS) which is sensitive to chemicals at low concentrations was used for hypothesis evaluation. To summarize the research work achievements, the conclusions of the thesis are given at the end.

Photocatalysis is a well-known process for the last few decades it is predominantly used for water and air purification, but also for self-cleaning and antibacterial surfaces. The photocatalytic process is one of the advanced oxidation processes, where semiconductors are mainly used as photocatalysts. The most known and used semiconductor is nanosized titania, which can non-selectively decompose organic matters. One of the side effects of nano TiO2 under UV irradiation is photoinduced hydrophilicity, which furthermore improves the self-cleaning effect. The main drawback of TiO2 is that for its activation UV light is needed, which represents only 5 percent of the solar spectrum. Consequently, actinic irradiance power is low and the response of photocatalyst is limited. Novel approaches are being introduced to improve TiO2 response to visible light such as doping, coupling, modification of surface morphology and others. The thesis consists of five principal chapters. The first chapter is focused on a short literature review and explanation of some basic terms and principles that are related to this thesis. The aim of the research was to prepare transparent photocatalytically active thin films on glass and thermosensitive substrates. Four thermosensitive substrates were used: polyvinyl chloride (PVC) foil, polymethyl methacrylate (PMMA) sheet and polyester (PES) fabric coated with a polyvinyl and acrylic coating, with (D1) or without (D2) an additional polyvinylidene fluoride topcoat. The synthesis of films was modified with the introduction of zirconium aiming at improving the photocatalytic activity of the TiO2 films, and the final films had a SiO2 phase present for increased mechanical robustness. The third chapter is dedicated to the experimental part of the thesis. The detailed process of synthesis is described. The sol-gel process was used to prepare initial Ti-Zr sols, colloidal aqueous solutions with TiO2 and ZrO2 nanoparticles derived from titanium and zirconium alkoxides. The four different Ti-Zr sols were prepared with 0, 5, 10 and 20 molar % of Zr according to Ti. The depositing solution was prepared by mixing Ti-Zr sol, SiO2 sol binder, 1-propanol and 2-propoxyethanol, and then thin films were deposited by dip-coating technique. After the deposition, samples did not require high-temperature calcination since the photocatalytic anatase phase was present already after drying the deposited layers. Coated glass slides were put into a furnace at 150 °C, while samples on thermosensitive substrates were just treated by a heat gun. Samples in powder and thin film form were characterized by UV-Vis, FTIR-ATR and laser beam deflection spectroscopy, X-ray diffraction, scanning electron microscopy and thermal analysis. One of the main aspects of the photocatalyst is its activity. Photocatalytic activity of the thin films was determined, either quantitatively by the formation of fluorescent hydroxyterephthalic acid, one of the first degradation products of terephthalic acid deposit, or qualitatively by a visual-based method where degradation of resazurin ink was observed. Two additional methods were used on glass samples, electron paramagnetic resonance, and degradation of methyl stearate by observing the change in water contact angle under UVA irradiation. Mechanical stability of films on various substrates is an essential factor, describing how successful was immobilization of the photocatalytic materials on the substrate. It was determined by the pencil hardness test, i.e., Wolff-Wilborn method. In the fourth chapter, titled “Results and Discussion,” the most important part of the thesis is placed. Materials characterization and associated discussion of the results are divided into three major parts: i) powder samples characterization ii) characterization of thin films on a glass substrate, and iii) characterization of films on thermosensitive substrates. In the conclusions, the main findings of the Ph.D. research work are summarized. One of our initial hypotheses was disapproved, thin films were not more active with a higher content of zirconium. However, they were more durable. All the obtained films were transparent and photoactive, despite the low-temperature synthesis procedure. Besides commonly used glass substrate, immobilization on thermosensitive substrates was also successful. Fotokataliza je postala v zadnjih nekaj desetletjih zelo razširjena uporablja se predvsem za čiščenje vode in zraka, za samočistilne ter protibakterijske površine. Fotokatalitski proces spada med napredne oksidacijske procese in kot fotokatalizatorji so največkrat uporabljeni polprevodniki. Najbolj znan in najpogosteje uporabljen polprevodnik je (nano) titanov dioksid, ki lahko neselektivno razgradi organske snovi ob UV sevanju. Pri obsevanju TiO2 z UV svetlobo se pojavi tudi fotovzbujena hidrofilnost, ki še dodatno izboljša samočistilni učinek. Ena od glavnih pomanjkljivosti TiO2 je, da se za njegovo fotoaktivacijo uporablja UV svetloba, ki predstavlja le pet odstotkov sončnega spektra. Za boljši odziv TiO2 na vidno svetlobo se razvijajo novi postopki, na primer dopiranje, kombiniranje z drugimi polprevodniki, modifikacija morfologije površine itd. Doktorsko delo ima pet glavnih poglavij. Prvo poglavje je osredotočeno na krajši pregled obstoječe literature in razlago nekaterih osnovnih pojmov. V drugem poglavju je predstavljen namen doktorskega dela. Pripravila sem transparentne fotoaktivne tanke plasti na steklu in temperaturno občutljivih podlagah. Izbrala sem štiri različne občutljive podlage: polivinil kloridna (PVC) folija, polimetil metakrilat (PMMA) plošča in poliesterska (PES) tkanina, prevlečena s slojem polivinila in akrila z (D1) ali brez (D2) dodatne poliviniliden fluoridne (PVDF) prevleke. Postopek priprave filmov smo obogatili z vpeljavo cirkonija, tako naj bi izboljšali aktivnost samih TiO2 filmov, končni raztopini je bil dodan tudi SiO2, ki je izboljšal mehanske lastnosti filmov. Tretje poglavje je posvečeno eksperimentalnemu delu. V poglavju je opisan podroben proces sinteze tankih plasti. Sol-gel postopek sem uporabila za pripravo začetnih Ti-Zr solov izhajajoč iz titanovega in cirkonijevega alkoksida. Pripravila sem štiri različne Ti-Zr sole z 0, 5, 10 in 20 množinskimi % cirkonija glede na titan. Raztopine za nanašanje so vsebovale Ti-Zr sol, SiO2 vezivo, 1-propanol in 2-propoksietanol tanke plasti pa so bile nanešene s tehniko potapljanja. Tanke filme po nanosu ni bilo potrebno termično obdelati na visoki temperaturi, ker je fotoaktivna anatazna faza že prisotna po sušenju vzorcev. Tako so bili vzorci na steklu toplotno obdelani v peči pri 150 ° C, vzorce na termično neobstojnih podlagah pa sem utrdila zgolj s toplotno pištolo. Praškaste vzorce in tanke plasti smo karakterizirali z naslednjimi metodami: UV-Vis, FTIR-ATR spektroskopijo in spektroskopijo z odklonom laserskega žarka, rentgensko praškovno difrakcijo, presevno elektronsko mikroskopijo in termično analizo. Najpomembnejša lastnost fotokatalizatorja je fotoaktivnost, ta je bila določena na tankih plasteh z dvema različnima metodama kvantitativno z merjenjem koncentracije hidroksiteraftalne kisline po razgradnji teraftalne kisline in kvalitativno, z opazovanjem razgradnje barvila resazurin. Z dvema dodatnima metodama smo izmerili fotoaktivnost tankih plasti na stekleni podlagi, z elektronsko paramagnetno resonanco in z merjenjem kontaktnega kota po razgradnji metil stearata pri UV obsevanju. Zelo pomembna lastnost tankih plati je mehanska odpornost in z merjenjem le te lahko ocenimo, če je bila imobilizacija na podlago uspešna. Mehansko stabilnost filmov smo določili z Wolff-Wilborn-ovo metodo. V četrtem poglavju je opisana karakterizacija materialov s spremljajočo razpravo o rezultatih, ki je razdeljena na tri glavne dele: i) karakterizacija praškastih vzorcev ii) karakterizacija tankih plasti na stekleni podlagi in iii) karakterizacija tankih plasti na termično neobstojnih podlagah. V zaključku so povzete glavne ugotovitve. Ena od naših začetnih hipotez ni bila potrjena, saj tanke plasti z višjo vsebnostjo cirkonija niso bile aktivnejše, izkazovali pa so večjo mehansko odpornost. Vsi vzorci so bili, kljub nizki temperaturi pripravi, transparentni in fotoaktivni. Imobilizacija fotokatalizatorjev je bila uspešna na steklu kot tudi na termično neobstojnih podlagah.

Pharmaceuticals in aquatic environment are considered as emerging environmental contaminants due to their constant presence, evironmental resistance and toxic effect they could have on aquatic organisms. Studies for Slovenia have shown the presence of pharmaceutical substances in waters to be comparable with published results of pharmaceutical water pollution in Europe. As conventional methods do not reach efficient pharmaceutical removal from water sources, more powerful and effective methods like heterogeneous photocatalysis using TiO2/UV have been implemented. Titanium dioxide coatings in silicate binder were prepared by the sol-gel process and deposited on a glass support with dip-coating technique. The films showed good quality and possibility of multiple use. The characterization of the films was performed with scanning electron microscope (SEM), x-ray diffraction (XRD) and hardness test (Elcometer 501 Pencil Hardness Tester). Effectiveness and quality of prepared TiO2 coatings for photodegradation of pharmaceutical compound paracetamol (PCT) were assessed during photocatalytic treatment and compared to photolysis, a process without presence of a catalyst. Photolysis caused substantial changes in paracetamol concentration between 120 and 180 minutes of irradiation where 92% of degradation was achieved, but with no changes in mineralization. Photocatalytic treatment was much faster and effective where 95% of paracetamol degraded within 90 minutes of UV irradiation and after prolonged irradiation time from 120 to 240 minutes also mineralization of paracetamol solution increased from 59% to 83%. Accordingly, toxicity decreased, but it was still not lower than in the starting PCT solution as it was shown by acute toxicity test on Daphnia magna aquatic organisms. The master thesis represents a step forward in studying photocatalytic removal of paracetamol from water, because to my knowledge all the published investigations on this pharmaceutical up to now include photocatalyst mostly in powder and not in immobilized form, which is more advantageous from application point of view.

Z naraščanjem populacije na Zemlji se povečuje potreba po čisti pitni vodi, hkrati pa, zaradi dvigovanja standarda življenja, močno narašča tudi količina odpadnih vod. Za čiščenje odpadnih vod se uporabljajo številni fizikalni, biološki in kemijski procesi, katerih učinkovitost je odvisna od prisotnih onesnaževal. Napredne oksidacijske metode (NOM) se uporabljajo za razgradnjo težje razgradljivih organskih onesnaževal. Pri tem gre za kemično obdelavo odpadnih vod z namenom razgradnje organskih snovi z oksidacijo preko hidroksilnih radikalov. Dve izmed naprednih oksidacijskih metod sta tudi fotokatalitska oksidacija in fotokatalitska ozonacija. Fotokataliza običajno poteka pod UV svetlobo v prisotnosti fotokatalizatorja (npr. TiO2). Fotokatalizator je lahko suspendiran v raztopini ali pa pritrjen na različne nosilce/substrate. Drug način uporabe je sicer manj učinkovit, vendar enostavnejši in zato bolj primeren za prenos tehnologije v prakso. V svoji magistrski nalogi sem se ukvarjal z iskanjem novih nosilcev za fotokatalizator in razvojem metod za nanos TiO2 na izbrane nosilce. Kot fotokatalizator sem po opravljenih poskusih z več katalizatorji uporabil Aeroxide® TiO2 P-90, proizvajalca Evonik. Preizkusil sem dva nosilca, in sicer pletena steklena vlakna in pa mrežico iz nerjavečega jekla. Izbrana sta bila, ker sta kemijsko inertna, poleg tega pa ju je enostavno prilagajati obliki reaktorske celice. Učinkovitost nosilcev sem preverjal z razgradnjo vodnih raztopin fenola in komercialnega tekstilnega barvila, Reactive Blue 19. Razgradnjo sem izvajal v pretočnem fotoreaktorju. Za analizo vzorcev sem uporabil visokotlačno tekočinsko kromatografijo (HPLC), analizo celokupnega ogljika (TOC) in pa UV-VIS spektrofotometer. Oba nosilca sta se izkazala za učinkovita, vendar pri različnih metodah. Steklena vlakna so bila najučinkovitejša pri fotokatalitski oksidaciji, mrežica iz nerjavečega jekla pa pri fotokatalitski ozonaciji. Za oba nosilca sta bili razviti tudi metodi nanašanja TiO2. The need for fresh drinking water is rising because of Earth’s population growth. At the same time the amount of wastewaters produced is higher than ever, due to higher standard of living. Different physical, biological and chemical processes are used for wastewater treatment. Efficiency of these processes is dependent on the type of pollutants found in wastewaters. Advanced oxidation processes (AOPs) are used in degradation of extra-stable organic pollutants. AOPs are chemical processes where organic pollutants are degraded by oxidation through hydroxyl radicals. Two AOPs, commonly used are photocatalytic oxidation and photocatalytic ozonation. Photocatalysis usually occurs under UV light in presence of photocatalyst (such as TiO2). Photocatalyst can be suspended in solution or attached to different supports/substrates. Second method is less efficient, but more economically acceptable. In my master thesis I was searching for new types of support for photocatalyst and methods of applying the catalyst to chosen support. Based on experiments with different catalysts, the chosen catalyst for the experiments was Aeroxide® TiO2 P-90, by Evonik. Two different supports were used hemmed knitted glass fiber stripes and stainless steel mesh. These two supports were used due to inertness and easy handling. Efficiency of supports was tested with degrading aqueous solutions of phenol and commercial textile dye, Reactive Blue 19. Degradation was made in flow-through reactor. Sample analyses were made by high-pressure liquid chromatography (HPLC), total organic carbon analysis (TOC) and UV-VIS spectroscopy. Both supports turned out to be efficient, but in different processes. Hemmed knitted glass fiber stripes were most efficient in photocatalytic oxidation, while stainless steel mesh was most efficient in photocatalytic ozonation. Methods for TiO2 deposition were also developed for both supports.

TiO2 - SiO2 composites were synthesized by low-temperature sol-gel impregnation method, using four different titania sources (P-25 from Degussa, PC500 from Millennium, CCA 100 AS and CCA 100 BS from Cinkarna, later denoted as AS and BS, respectively) and deposited on aluminium and glass carriers. Ordered and disordered mesoporous silicas were impregnated with ce{TiO2} in powder or suspension form in the Ti : Si molar ratio 1 : 1. Structure, size, band gap, chemical composition and specific surface area of nanoparticles were determined by X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DR-UV-vis), Fourier transform infrared spectroscopy (FT-IR) and ce{N2} physisorption. Additionally, quantity of surface hydroxyl groups, surface acidity and mechanical stability of the coatings were determined by temperature programmed Fourier transform infrared spectroscopy (TPD-IR) and Wolff-Wilborn method, respectively. The photocatalytic activity of TiO2 and TiO2 - SiO2 composites was evaluated in the photodegradation of toluene and formaldehyde, as model VOCs, under UVA light irradiation in lab-made photoreactor system with two different regimes batch and plug-flow mode. These two VOCs are being considered as examples of two of the six major classes of indoor air contaminants. Adsorption properties of the samples with toluene, have shown that the addition of mesoporous silica was beneficial. The increase of the adsorption of the bare AS TiO2 (9.5 %) was higher in the case of ordered silica, SBA-15 (2.8 times for AS/SBA15 to 26.8 %) than disordered SiO2 KIL-2 (2.4 times for AS/KIL2 to 22.7 %) although it was significant in both types of mesoporous silica supports (over 20 %). Adsorption was found to be dependent mostly on the quantity of surface Si-OH groups. Regarding the photocatalytic activities towards toluene degradation, the results with pure TiO2 showed the fastest kinetics in case of sample AS followed by PC500 and P25. The observed behaviour was ascribed to smaller particle size, and consequently higher specific surface area. Grafting titania onto silica showed the importance of structural parameters. Most importantly, if the pore structure of bare TiO2 collapsed, this resulted in decreased activity. On the other hand, retainment of the pore structure improved the distribution of nanoparticles, crystallinity and optical properties, which resulted in improved photocatalytic activity. In the degradation of formaldehyde, it was found that adsorption and degradation abilities of the materials were much more dependent on the structural properties of the samples, i.e., the pore structure. This was explained as a consequence of the different degradation mechanisms of both pollutants. Toluene degradation is governed by the oxidation through photogenerated holes - direct oxidation, whereas in the degradation of formaldehyde, the major oxidative species are OH radicals. In addition, the same as in toluene oxidation, the activity was dependent mainly on the number of crystal defects and the band gap values, that is the oxidation and reduction potentials of the catalysts. The degradation efficiency was increased from 88 % in pure AS TiO2 to 97 % when this titania was grafted onto colloidal silica (7C). An important highlight of the thesis is synthesis of a novel photocatalyst, labelled AS7C, which comprises an acidic colloidal suspension AS as TiO2 source and colloidal silica, using a low-temperature sol-gel impregnation method. This sample used all the above mentioned properties that improve photocatalytic activity towards both pollutants. Mechanical stability of the samples was also tested. The tests showed that binder, in the form of colloidal SiO2 (in size of 25 nm) in combination with colloidal titania of appropriate size - 6 nm, produced the highest mechanical stability of the coatings, which also showed excellent photocatalytic activity. Stability of the coatings, using AS as titania source, was greatly improved. The Wolff-Wilborn test on AS coating showed no mechanical resistance, while with the optimal (in terms of photocatalytic performance) addition of 7C SiO2 binder stability was excellent (F, which is in the middle of 6B-6H hardness scale). This sample (AS7C) was also tested for release of aerosols, during operation of the reactor, which could be harmful for human health at longer exposure times. It was found that aerosols are formed, probably as a consequence of detachment of nanoparticles in the first period of photodegradation test. However, their formation in consecutive tests was greatly reduced. Last but not least, a pilot plug-flow reactor was constructed to test the photocatalyst's efficiency in one-pass degradation of toluene. Sample AS7C was able to degrade toluene at conditions applied (v= 400 mL/min, m(catalyst) = 1049 mg, C(0) = 1 ppmv), which means that the out-flow from reactor was clean of the pollutant and any possible intermediates, comprising only of humid air and CO2. Deactivation of the catalyst was found at higher air flow and higher initial concentration of the pollutant. However, the concentrations of pollutants in living conditions are few orders of magnitude lower, hence this is a promising result. Sintetizirani so bili TiO2 − SiO2 kompoziti po nizko-temperaturnem sol-gel postopku impregniranja, z uporabo štirih komercialno dostopnih virov TiO2 (P-25 iz Degusse, PC500 iz Millenniuma ter CCA 100 AS in CCA 100 BS iz Cinkarne, kasneje označena kot AS in BS) ter njihova imobilizacija na aluminij in steklene nosilce. Urejeni in neurejeni mezoporozni SiO2 so bili impregnirani s TiO2 v obliki prahu ali v obliki suspenzije v Ti : Si molskem razmerju 1: 1. Določeni so bili struktura, velikost delcev, energijska vrzel kompozitov, njihova kemična sestava in specifična površina s praškovno rentgensko difrakcijo (XRD), vrstičnim elektronskim mikroskopom (SEM) in transmisijsko elektronsko mikroskopijo (TEM), UV-vis difuzno reflektanco (DR-UVvis), infrardečo spektroskopijo s Fourierjevo transformacijo (FT-IR) in N2 fizisorpcijo. Poleg tega je bila določena količina hidroksilnih skupin na površini, kislost na površini ter mehanske stabilnosti prevlek, določene z uporabo temperaturno programirane infrardeče spektroskopije s Fourierjevo transformacijo (TPD-IR) in Wolff-Wilborn testom trdnosti. Fotokatalitska aktivnost TiO2 in TiO2 − SiO2 kompozitov je bila ocenjena za fotorazgradnjo toluena in formaldehida kot modelnih VOC-ov pod UVA osvetlitvijo v laboratorijsko narejenem fotoreaktorskem sistemu v okviru dveh različnih režimov krožnem in pretočnem. Ta dva VOC-a sta predstavnika dveh od šestih glavnih skupin onesnaževal notranjih prostorov. Absorpcijske lastnosti vzorcev, glede toluena kot onesnaževala, so pokazale, da je dodajanje mezoporoznega SiO2 koristno. Adsorpcija čistega TiO2 vira iz Cinkarne Celje (AS) (9.5 %) se je bolj povišala v primeru dodatka urejenega vira SiO2 – SBA-15 (2,8-krat za AS/SBA15 na 26.8 %) kot neurejenega vira SiO2 – KIL-2 (2,4-krat za AS/KIL2 na 22.7 %). Po drugi strani pa je bilo ugotovljeno, da je adsorpcija odvisna predvsem od količine Si−OH skupin na površini. Še več, impregnacija TiO2 z mezoporozno siliko adsorpcije ne izboljša vedno. Glede fotokatalitskih aktivnosti za razgradnjo toluena, so rezultati z uporabo ˇ cistega TiO2 pokazali najhitrejšo kinetiko v vzorcu AS, ki sta mu sledila PC500 in P25. Opaženo vedenje sem pripisal manjši velikosti delcev in s tem višji specifični površini. Vgradnja TiO2 v/na SiO2 je izpostavila pomen strukturnih parametrov. Kot najpomembnejša se je izkazala porušitev strukture por čistega TiO2, namreč to je povzročilo zmanjšano aktivnost. Po drugi strani pa je ohranitev strukture por pri impregnaciji izboljšala porazdelitev nanodelcev, kristaliničnost in optične lastnosti materiala, kar je povzročilo izboljšano fotokatalitsko aktivnost. Pri razgradnji formaldehida je bilo ugotovljeno, da so adsorpcijske in aktivnostne lastnosti materialov veliko bolj odvisne od strukturnih lastnosti vzorcev, to je strukture por. To si razlagamo kot posledico različnih mehanizmov razgradnje obeh onesnaževal. Razpad toluena poteka z oksidacijo preko fotovzbujenih lukenj - direktno oksidacijo, medtem ko so pri degradaciji formaldehida glavni oksidanti OH radikali. Poleg tega je enako kot pri oksidaciji toluena aktivnost odvisna predvsem od števila napak v kristalni strukturi in velikosti energijske vrzeli, torej redoks potenciala katalizatorjev. Sintetiziral sem nov fotokatalizator, označen z AS7C, ki izhaja iz kisle koloidne suspenzije AS kot vira TiO2 in koloidnega SiO2 kot veziva, z uporabo preproste, nizkotemperaturne sol-gel metode impregnacije. Ta vzorec izkorišča prednosti vseh zgoraj navedenih lastnosti, ki izboljšujejo fotokatalitsko aktivnost pri obeh onesnaževalih. Preizkusil sem tudi mehansko stabilnost vzorcev. Testi so pokazali, da je vezivo v obliki koloidnega SiO2, (velikost SiO2 delcev 25 nm), v kombinaciji s koloidno suspenzijo delcev titanovega dioksida primerne velikosti - 6 nm poveˇ calo mehansko obstojnost premazov. Prav tako so te plasti pokazale odlično fotokatalitsko aktivnost. WolffWilborn-ov test plasti iz čistega AS TiO2 ni pokazal nobene mehanske odpornosti, medtem ko sem z optimalno količino (v smislu fotokatalitske aktivnosti) dodanega 7C SiO2 veziva uspel dobiti plasti, ki so pokazale odlično trdnost (F, kar je na sredini 6b–6H trdnostne lestvice). Vzorec AS7C je bil testiran tudi za nastajanje aerosolov, med delovanjem reaktorja, ki so lahko pri daljših ˇ casih izpostavitve škodljivi za zdravje ljudi. Ugotovil sem, da aerosoli nastajajo, verjetno zaradi odstranjevanja nanodelcev iz plasti v prvem obdobju delovanja reaktorja. Tvorba aerosolov v sledečih testih pa je bila močno zmanjšana, kar kaže na dolgoročno ustreznost uporabe materiala za čiščenje zraka. Nenazadnje je bil izdelan pilotni pretočni reaktor za testiranje učinkovitosti fotokatalizatorja pri razgradnji enkratnega prehoda toluena. Vzorec AS7C je bil sposoben razgraditi začetno koncentracijo toluena, 1 ppmv (pretok zraka = 400 mL/min, m(katalizator) = 1049 mg), kar pomeni, da je bil zrak pri izhodu iz reaktorja čist ter brez vemsnih produktov. Pri višjih pretokih zraka in višji začetni koncentraciji onesnaževala sem zaznal deaktivacijo katalizatorja. Kljub temu pa so koncentracije VOC-ev v bivalnih prostorih nekaj redov velikosti nižje, zato je to obetajoč rezultat.