Ces dernières années, les problèmes d’environnement et de dépollution sont devenus cruciaux. En particulier, les industries textiles sont une source très importante de pollution des milieux aquatiques. De 60 à 70 % des colorants de l’industrie textiles contiennent une ou plusieurs fonctions azoïques et sont pour la plupart d’entre eux toxiques, mutagènes et cancérigènes. L’objectif de la thèse a été d’évaluer l’efficacité du procédé photocatalytique pour éliminer des colorants anioniques et cationiques seuls ou en mélange en présence de dioxyde de titane et d’argile pontée au titane, synthétisé au laboratoire. Trois colorants sont étudiés comme modèle le bleu de Méthylène (BM), le noir Rémazol 5 (NR5) et le réactif rouge 2 (RR2). La première partie du travail est une étude cinétique de l’adsorption, de la dégradation et de la minéralisation de ces colorants à différents pH. Plusieurs conclusions émergent (1) l’isotherme d’adsorption n’est pas une isotherme de Langmuir (2) aucune corrélation n’est observée entre les quantités adsorbées et les vitesses de dégradation et (3) à forte concentration en colorants, une partie de la lumière est absorbée et la vitesse de dégradation diminue. La seconde partie du travail concerne l’étude du mélange des deux colorants anioniques. L’influence du rapport molaire, du pH et de la concentration initiale sur l’isotherme d’adsorption, la cinétique de décoloration et de minéralisation des deux colorants dans le mélange sont étudiés et comparés à celle obtenues pour les colorants pris individuellement. Aucun complexe n’est formé. Des compétitions entre les deux colorants sont observées après saturation de la surface de TiO2. Au-delà de la saturation du catalyseur un ralentissement de la minéralisation du COT et des hétéroatomes est observé. La troisième partie de l’étude est dédiée à l’étude de la préparation, caractérisation et propriétés photocatalytique de l’argile pontée au TiO2 (MMT-TiO2) et du matériau composite : argile pontée au TiO2 dopée avec de l’argent (MMT-TiO2/Ag). Cette étude est réalisée sur le colorant cationique (BM) et le colorant anionique (NR5). Une adsorption totale du colorant BM est observée, contrairement au NR5 qui ne s’adsorbe pratiquement pas, suggérant une adsorption par liaison ionique. L’argile pontée dopée ou non ne présente pas des propriétés photocatalytiques plus importantes que celle de TiO2 mais joue un rôle important sur l’adsorption des colorants cationiques, ce qui favorise leur élimination de la solution aqueuse. La présence d’Ag diminue les propriétés d’adsorption et de photocatalyse de l’argile pontée. / The problems of environment become crucial. In particular, textile industries are important sources of pollution of the aquatic system. 60% to 70% of dyes used in these textiles industries are azo dyes containing one or more; some of them are toxic, mutagenic and carcinogenic compounds. The aim was to evaluate the efficiency of photocatalytic processed for the elimination of anionic and cationic dyes alone or in combination with titanium dioxide and clay pillared with titanium, synthesized in the laboratory. The photocatalytic processing is interesting because solar flux can be used. Three dyes were studied as model: methylene blue (BM), black Remazol 5 (NR5) and reactive red 2 (RR2). The first part of this work is a kinetic study of adsorption, degradation and mineralization of these dyes at different pH. Several conclusions emerge (1) the adsorption isotherm is not of Langmuir type(2) no correlation exists between the quantities adsorbed and the degradation rates and (3) at high concentration, a part of UV is absorbed by the dye and the degradation rate decreases. The second part of the work involves the study of the mixture of two anionic dyes. The concentration of both dyes in the mixture, the influence of molar ratios, pH and initial concentration on the adsorption isotherm, kinetics of decolorization and mineralization of the two dyes in the mixture are compared to that obtained for the individual dyes. No complex is formed and competition between the two dyes occurs only after saturation of the photocatalyst surface. Beyond the saturation of the catalyst a slower mineralization of TOC and heteroatoms are observed. The third part deals with the preparation, characterization and photocatalytic properties of TiO2 pillared clay (MMT-TiO2) and of a composite material: TiO2 pillared clay doped with silver (MMT -TiO2/Ag), performed on the cationic dye (MB) and the anionic dye (NR5). A total adsorption of the BM dye is observed. Constrasting with the NR5 adsorption suggesting an adsorption by ionic bond. The pillared clay doped or not with silver but favors the elimination of dyes from the aqueous solution by adsorption. The presence of silver reduces the adsorption properties and photocatalysis properties of the pillared clay.

<p>Ispitana je direktna i indirektna razgradnja odabranih&nbsp; &beta;-blokatora (metoprolol- tartarata, MET i propranolol-hidrohlorida, PRO) kao i diuretika (hidrohlortiazida, HCTZ) i njegovog stabilnog intermedijera hidrolize 4-amino-6-hlor-1,3-benzendisulfonamida (ABSA). Praćena je i kinetika razgradnje direktnom i indirektnom fotolizom uz primenu UVA, UVC, sunčevog i simuliranog sunčevog zračenja (SSZ). Najpre je ispitana&nbsp; stabilnost MET pod dejstvom SSZ, UVA, UVC, UVA/H₂O_{2 ,} i UVA/&nbsp; BrO₃^-. Dalje je ispitana efikasnost razgradnje MET pod dejstvom O₃i UVC/O_3. Identifikovano je deset intermedijera tokom UVC, O_3&nbsp;i UVC/O₃ razgradnje, pri&nbsp; čemu samo jedan ima značajno vi&scaron;u toksičnost prema algama i bakterijama u odnosu na ostale. Efikasnost fotokatalitičke razgradnje MET je ispitana u TiO₂ suspenzijama sa komercijalnim katalizatorima (Wackherr i Degussa P25). Mehanizam fotokatalitičke razgradnje je detaljno ispitan, pri&nbsp; čemu je identifikovano&nbsp; četrnaest intermedijera. EC₅₀ vrednost MET i njegovih sme&scaron;a nastalih pri fotokatalitičkoj razgradnji su određene na tri ćelijske linije sisara (H-4-II-E, HT-29 i MRC-5). Kako bi se povećala efikasnost&nbsp; rocesa fotokatalitičke razgradnje primenom komercijalnih katalizatora, ispitan je&nbsp; uticaj prisustva elektron-akceptora u suspenziji, pri čemu je upoređen uticaj O₂/H₂O₂, i O₂/ BrO₃^-&nbsp;na mehanizam razgradnje. Na osnovu teorije funkcionala gustine stekao se uvid u promene unutar molekula MET u prisustvu reaktivnih radikala. Takođe, ispitana je efikasnost nedopiranih TiO₂ , kao i dopiranih La(III) nanoprahova sintetisanih sol&minus;gel postupkom, u razgradnji MET. Uticaj temperature &nbsp;kalcinacije na fotokatalitičku efikasnost TiO 2 nanoprahova dopiranih pomoću La(III) &nbsp;ispitana je na supstratima MET i PRO, pri čemu je analiziran i uticaj strukture&nbsp; polaznog jedinjenja na&nbsp; informacija efikasnost fotokatalitičke razgradnje. Rezultati su upoređeni sa nedopiranim TiO₂nanoprahom i TiO₂Degussa P25 (pri pH-vrednosti 9). Pored toga, ispitana je kinetika i toksičnost PRO i njegovih intermedijera nastalih tokom razgradnje sa TiO₂Degussa P25. Ispitan je i uticaj strukture polaznog jedinjenja (MET, HCTZ i ABSA) na fotorazgradnju pod dejstvom&nbsp;UVA, sunčevog i simuliranog sunčevog zračenja, u odsustvu/prisustvu TiO₂ Degussa P25. Takođe, ispitan je i sinergistički efekat MET i ABSA na proces hidrolize, direktne fotolize i fotokatalize sa SSZ/TiO₂Degussa P25. Kako bi se stekao uvid u toksičnost proučavanih sistema, ispitan je njihov uticaj na rast odabranih ćelijskih linija sisara.</p> / <p>Direct and indirect degradation of selected&nbsp; &beta;-blockers (metoprolol tartrate, MET and&nbsp;propranolol hydrochloride, PRO) and also diuretic (hydrochlorothiazide, HCTZ) in &nbsp;addition to its stable hydrolysis intermediate 4-amino-6-chloro-&nbsp;&nbsp; 1,3-benzenedisulfonamide (ABSA) were investigated. The kinetics of their degradation obtained by direct and indirect photolysis under UVA, UVC, sunlight and simulated sunlight irradiation (SSI) have been followed. Firstly, the stability of MET under influence of SSI, UVA, UVC, UVA/H₂O₂ , and UVA/&nbsp; BrO₃^- has been investigated. Further, the efficiency of MET degradation under influence of O₃, and UVC/O₃ has been explored. Ten intermediates have been identified during the UVC, O₃, and UVC/O₃ treatments, while only one intermediate had significantly higher toxicity towards the algae and bacteria in respect to the others. Efficiency of&nbsp; photocatalytic degradation of MET was investigated in TiO₂ suspensions with&nbsp;commercial catalysts (Wackherr and Degussa P25). Mechanism of photocatalytic degradation was investigated in detail according to which fourteen intermediates were identified. EC 50 &nbsp;value of MET and its mixtures formed during the photocatalytic degradation has been determined at three mammalian cell lines (H-4-II-E, HT-29, and MRC-5). In order to improve the efficiency of photocatalytic degradation process applying commercial catalysts, the influence of presence of electron acceptors in suspension has been investigated and the influence of O₂/H₂O_2&nbsp;and O₂/BrO₃^- to the mechanism of degradation has been compared. Based on the density&nbsp; functional theory an insight to the changes within MET molecule in the presence of reactive radicals has been made. Also, the efficiency of bare TiO₂, as well as&nbsp;doped La(III) nanopowders synthesized by sol-gel procedure, in the degradation of&nbsp; MET has been investigated. The influence of calcination temperature on&nbsp; hotocatalytic efficiency of TiO_2&nbsp;nanopowders doped with La(III) has been studied on the MET and&nbsp; PRO substrates, and the influence of structure of the starting compound on the&nbsp; efficiency of &nbsp;photocatalytic degradation had been analyzed. Results have been&nbsp; compared with bare TiO_2&nbsp;nanopowder and TiO₂ Degussa P25 (at pH value of 9). Besides, kinetics and toxicity of PRO and its intermediates formed during the degradation with TiO₂ Degussa P25 have been investigated. The influences of starting compound&rsquo;s structure (MET, HCTZ, and ABSA) to photodegradation under UVA, sunlight and SSI, in the absence/presence of TiO₂ Degussa P25, have been investigated. Also, the synergistic effects of MET and ABSA to the process of&nbsp; hydrolysis, direct photolysis, and photocatalysis with SSI/TiO₂ Degussa P25 have been investigated. In order to get &nbsp;an insight into the toxicity of the studied systems, their influence on the growth of selected mammalian cell lines has been investigated as well.</p>

<p>Ispitana je kinetika i mehanizam fotokatalitičke&nbsp;razgradnje herbicida kvinmeraka i klomazona u prisustvu&nbsp;UV/TiO₂&nbsp; Degussa P25, odnosno piklorama i&nbsp; klopiralida&nbsp;<br />primenom UV/TiO₂&nbsp; Wackherr pri različitim&nbsp;eksperimentalnim uslovima. Praćena je i kinetika&nbsp;razgradnje odabranih herbicida direktnom fotolizom uz&nbsp;primenu sunčevog, UV i vidljivog zračenja, kao i u&nbsp;odsustvu svetlosti. Pored toga, upoređena je efikasnost&nbsp;<br />UV/TiO₂&nbsp; Degussa P25, odnosno UV/TiO₂&nbsp; Wackherr sa&nbsp;vidljivim zračenjem, kao i direktnom fotolizom u&nbsp;prisustvu pomenutih izvora svetlosti.&nbsp; U cilju procene&nbsp;<br />citotoksičnosti klomazona i klopiralida, kao i sme&scaron;e&nbsp;klomazona i klopiralida i njihovih intermedijera nastalih&nbsp;tokom fotokatalitičke razgradnje ispitan je&nbsp; in vitro&nbsp; rast&nbsp;<br />ćelijskih linija&nbsp; MRC-5 i H-4-II-E.&nbsp; Nakon ispitivanja&nbsp;fotokatalitičke razgradnje odabranih herbicida u dvaput&nbsp;destilovanoj vodi, praćena je njihova razgradnja i u&nbsp;prirodnim vodama. Takođe, ispitan je uticaj dodatka&nbsp;hidrogenkarbonata i huminske kiseline na efikasnost&nbsp;razgradnje odabranih herbicida. Fotokatalitička razgradnja&nbsp;klomazona, piklorama i mekopropa je ispitivana i u&nbsp;prisustvu UV/TiO₂&nbsp; nanocevi. Aktivnost katalizatora TiO_2&nbsp;Wackherr&nbsp; i TiO₂&nbsp; nanocevi je upoređena sa TiO₂&nbsp; Degussa&nbsp;P25.</p> / <p>The kinetics and mechanism of photocatalytic degradation&nbsp;of the herbicides quinmerac and clomazone in the&nbsp;presence of UV/TiO₂&nbsp; Degussa P25, and of picloram and&nbsp;clopyralid using UV/TiO₂&nbsp; Wackherr under different&nbsp;experimental conditions were studied. The kinetics of&nbsp;degradation of selected herbicides by direct photolysis&nbsp;using sunlight, UV and visible radiation, and in the&nbsp;absence of light were followed. In addition, the&nbsp;efficiencies of UV/TiO₂&nbsp; Degussa P25 and UV/TiO_2&nbsp;Wackherr &nbsp;were compared with visible radiation and direct&nbsp;photolysis in the presence of the above mentioned light&nbsp;sources. In order to evaluate the cytotoxicity of clomazone&nbsp;<br />and clopyralid alone and in their mixture with&nbsp;intermediates formed during the photocatalytic&nbsp;degradation, in vitro growth of cell lines, MRC-5 and H-4-II-E was followed. After examining&nbsp; the photocatalytic&nbsp;degradation of selected herbicides in double distilled&nbsp;water, their decomposition in natural waters was also&nbsp;followed. Also, the influence of hydrogencarbonate and&nbsp;humic acid addition on the efficiency of degradation of&nbsp;selected herbicides was studied. Photocatalytic&nbsp;degradations of clomazone, picloram and mecoprop were&nbsp;investigated in the presence of UV/TiO_2&nbsp;nanotubes. Activities of the catalysts TiO₂&nbsp; Wackherr and TiO_2&nbsp;nanotubes were compared to TiO₂ Degussa P25.</p>

This diploma thesis aims to optimalization the process of magnetron sputtering and creating of thin layers for use in advanced oxidation processes. During the work was created range of TiOx layers. For this process was used physical method of sputtering called PVD. The photocatalytic activity of the deposited films was tested by degradation of organic dyes Acid Orange 7. Furthermore, the layer was analyzed on surface morphology (SEM) and the layer thickness (profilometry). Study of created layers was focused on the link between the characteristics of each layer, deposition parameters and photocatalysis properties. Based on these results, the layers were applied in a system using AOP for the decomposition of organic substances. The first chapter is devoted to a summary of existing knowledge of photocatalysis and its principles. Another chapter is devoted to the theory and methods of applying thin layers and summary of knowledge of the low-pressure discharges. In the exprimental section there are described various components of the apparatus. Furthermore, the experimental part of the work focuses on the analysis of the optimization process of applying thin layers on titanium oxide. The last chapter of the thesis contains the results of the experiments on the basis of is designed another research progress of this issue.

Composite materials formed from two or more functionally different materials offer a versatile avenue to create a tailored material with well defined traits. Within this dissertation research, multi-functional composites were synthesized based on organic and inorganic materials. The functionally of these composites was experimentally tested and a semi-empirical model describing the sedimentation behavior of these particles was developed. This first objective involved the fabrication of microcomposites consisting of titanium dioxide (TiO2) nanoparticles confined within porous, microgels of a thermo-responsive polymer for use in the photocatalytic treatment of wastewater. TiO2 has been shown to be an excellent photocatalyst with potential applications in advanced oxidative processes such as wastewater remediation. Upon UV irradiation, short-lived electron-hole pairs are generated, which produce oxidative species that degrade simple organic contaminants. The rapid sedimentation of these microcomposites provided an easy gravimetric separation after remediation. Methyl orange was used as a model organic contaminant to investigate the kinetics of photodegradation under a range of concentrations and pH conditions. Although after prolonged periods of UV irradiation (~8-13 hrs), the titania-microgels also degrade, regeneration of the microcomposites was straightforward via the addition of polymer microgels with no loss in photocatalytic activity of the reformed microcomposites. The second objective within this dissertation involved the systematic development of abrasive microcomposite particles containing well dispersed nanoparticles of ceria in an organic/inorganic hybrid polymeric particle for use in chemical mechanical polishing/planarization (CMP). A challenge in IC fabrication involves the defect-free planarization of silicon oxide films for successful multi-layer deposition. Planarization studies conducted with the microcomposites prepared in this research, yield very smooth, planar surfaces with removal rates that rival those of inorganic oxides slurries typically used in industry. The density and size of these ceria-microgel particles could be controlled by varying the temperature or composition during synthesis, leading to softer or harder polishing when desired.

No description available.

<p>Kao &scaron;to je poznato, RS-2-(4-hlor-o-toliloksi)propionska kiselina (MCPP),&nbsp;(4-hlor-2-metilfenoksi)sirćetna kiselina (MCPA) i 3,6-dihlorpiridin-2-karboksilna kiselina &nbsp;(klopiralid) su herbicidi sa veoma &scaron;irokim spektrom dejstva, a pored toga su rastvorljivi u&nbsp;vodi, te&scaron;ko biorazgradljivi i prema literaturnim podacima su, nažalost, veoma često prisutni&nbsp;herbicidi u pijaćoj vodi. Proces heterogene fotokatalize uz primenu TiO₂i UV zračenja se&nbsp;pokazao kao veoma pogodan način za njihovo uklanjanje iz vode. Međutim, zbog velikog&nbsp;energetskog procepa od 3,2 eV (anataze-oblik), odnosno, 3,0 eV (rutil-oblik), veoma mali&nbsp;udeo bliskih UV zraka iz sunčeve svetlosti (oko 3&minus;4%) biva iskori&scaron;ćen u toku&nbsp;fotokatalitičkog procesa, &scaron;to ukazuje na to da je TiO_2&nbsp;praktično neaktivan u prisustvu&nbsp;sunčeve svetlosti. Na osnovu literaturnih podataka je zapaženo da postoji mogućnost&nbsp;fotorazgradnje pojedinih supstrata u prisustvu TiO_2&nbsp;primenom vidljive svetlosti. Na&nbsp;primeru MCPP je ispitana aktivnost TiO_2&nbsp;Degussa P25 kao fotokatalizatora u prisustvu&nbsp;vidljive svetlosti. Na osnovu refleksionih spektara je utvrđeno da MCPP adsorbovan na&nbsp;TiO_2&nbsp;Degussa P25 apsorbuje vidljivi deo spektra (&lambda; &ge;400 nm). Nastali prelazni kompleks&nbsp;je potvrđen FTIR merenjima. Efikasnost TiO2Degussa P25 primenom vidljive svetlosti je&nbsp;upoređena sa sunčevim i UV zračenjem, kao i direktnom fotolizom u prisustvu pomenutih&nbsp;izvora zračenja. Brzina fotokatalitičke razgradnje MCPP primenom vidljive svetlosti iznosi&nbsp;0,86 &mu;mol dm^&minus;3min^&minus;1, &scaron;to je oko 4 puta brže u poređenju sa direktnom fotolizom. Nadalje&nbsp;je ustanovljena optimalna masena koncentracija katalizatora od oko 8 mg cm^&minus;3, koja je&nbsp;znatno vi&scaron;a u poređenju sa primenom UV zračenja. Razlog je najverovatnije različit&nbsp;mehanizam fotorazgradnje koji se odvija primenom vidljivog i UV zračenja. Naime,&nbsp;prisustvo 2-metil-2-propanola (poznatog hvatača&nbsp;^&bull;OH-radikala) praktično ne utiče na&nbsp;brzinu fotokatalitičke razgradnje MCPP p rimenom vidljive svetlosti, &scaron;to ukazuje da se&nbsp;mehanizam razgradnje MCPP primenom &nbsp;vidljive svetlosti ne odvija posredstvom&nbsp;^&bull;OH-radikala, za razliku od onog uz primenu UV zračenja.</p><p>S obzirom da se katalizator TiO_2&nbsp;Degussa P25 uz primenu vidljive svetlosti nije&nbsp;<br />pokazao kao naročito efikasan kada je u pitanju razgradnja sva tri herbicida i imajući u&nbsp;vidu da se u poslednje vreme iz razloga praktične primene sve vi&scaron;e pribegava procesu dopovanja TiO_2&nbsp;različitim tipovima metala (alkalnih, zemnoalkalnih, prelaznih i dr.) i nemetala (halogenida, halkogenida i dr.), u okviru ove doktorske disertacije je ispitana aktivnost N-TiO₂(sintetisanih mokrim i suvim putem) i TiO_2&nbsp;(rutil) dopovanog sa različitim količinama Fe³⁺-jona (0,13&minus;1,48 at.%) pri razgradnji herbicida MCPP i MCPA primenom vidljive svetlosti. Pored toga je ispitana efikasnost TiO_2&nbsp;(anataze) takođe dopovanog sa različitim količinama Fe³⁺-jona (0,71&minus;1,80 at.%) na primeru MCPP.&nbsp;</p><p>Poredeći N-TiO_2&nbsp;(sintetisan mokrim putem) i N-TiO_2&nbsp;(sintetisani suvim putem), primećeno&nbsp;je da je u drugom slučaju efikasnost katalizatora veća oko 2 puta. Isto tako je zapažena u&nbsp;slučaju MCPP ne&scaron;to veća fotokatalitička aktivnost N-TiO_2&nbsp;(sintetisani suvim putem) u&nbsp;poređenju sa TiO_2&nbsp;(anataze). Kada je u pitanju MCPA aktivnost sva tri katalizatora je&nbsp;veoma slična. Pored toga je zapažena veća efikasnost N-TiO_2&nbsp;(sintetisan mokrim putem) u&nbsp;poređenju sa TiO_2&nbsp;Degussa P25 (oko 1,5 puta) i oko 5 puta u odnosu na direktnu fotolizu,&nbsp;dok su N-TiO_2&nbsp;(sintetisani suvim putem) oko 3 puta efikasniji u poređenju sa TiO_2&nbsp;Degussa P25 i oko 10 puta u &nbsp;poređenju sa direktnom fotolizom. Brzina solarne razgradnje&nbsp;je preko 100 puta manja nego primenom vidljivog i UV zračenja, &scaron;to je posledica različitih&nbsp;intenziteta pomenutih izvora ozračivanja i različitih uslova pri kojima je vr&scaron;ena razgradnja. &nbsp;Ustanovljena je optimalna masena koncentracija N-TiO_2&nbsp;(sintetisan mokrim putem) od&nbsp;4 mg cm^&minus;3.</p><p>Prilikom razgradnje MCPP i MCPA je nađeno da je brzina veća kada se kao&nbsp;katalizator &nbsp;koristi TiO_2&nbsp;(rutil) u poređenju sa Fe-TiO_2&nbsp;i da sa povećanjem količine Fe³⁺-jona fotokatalitička aktivnost uglavnom opada. Kada je kao fotokatalizator kori&scaron;ćen TiO_{2 &nbsp;}<br />(anataze) dopovan različitim količinama Fe³⁺-jona (od 0,71 do 1,80 at.%), razgradnja&nbsp;<br />MCPP je u svim slučajevima znatno sporija u odnosu na TiO_2&nbsp;(anataze).</p><p>S obzirom da su prema literaturnim podacima kinetika i mehanizam fotokatalitičke&nbsp;<br />razgradnje klopiralida nepoznati, ispitana je njegova stabilnost pri različitim&nbsp;eksperimentalnim uslovima. Tokom ispitivanja uticaja pH kako u prisustvu, tako i u&nbsp;odsustvu dnevne svetlosti u intervalu pH od 1,0&minus;9,0, nađeno je da ni u jednom slučaju ne&nbsp;dolazi do razgradnje supstrata u periodu od sedam meseci koliko je proces praćen. Takođe&nbsp;je ispitana kinetika fotokatalitičke razgradnje klopiralida primenom UV i vidljivog&nbsp;zračenja u prisustvu TiO_2&nbsp;Degussa P25, kao i direktna fotoliza primenom oba izvora&nbsp;zračenja. Nađeno je da je brzina fotokatalitičke razgradnje primenom UV zračenja veća&nbsp;oko 5 puta u odnosu na direktnu fotolizu. Za praćenje toka fotokatalitičke razgradnje&nbsp;klopiralida je izabrana pH-vrednost od 3,2. Nadalje je zapaženo da se u ispitivanom opsegu početnih koncentracija supstrata (0,5&ndash;3,0 mmol dm^&minus;3) kinetika fotokatalitičke razgradnje klopiralida može opisati pseudo-prvim redom. Pri ispitivanju uticaja masene koncentracije katalizatora (0,5&ndash;8 mg cm^&minus;3) na brzinu razgradnje klopiralida, ustanovljena je optimalna masena koncentracija primenjenog fotokatalizatora od oko 4 mg cm^&minus;3. Izračunata ukupna &nbsp;prividna energija aktivacije iznosi 7,74 kJ mol^&minus;1. Pored toga, prisustvo kiseonika ubrzava reakciju 2 puta, dok dodatak elektron-akceptora kao &scaron;to su (NH₄)₂S₂O₈, H₂O_2&nbsp;i KBrO_3&nbsp;pokazuje značajan i različit efekat na kinetiku fotokatalitičke razgradnje klopiralida. Pri ispitivanju uticaja etanola, kao hvatača slobodnih radikala, nađeno je da se heterogena fotokataliza odvija uglavnom preko ^&bull;OH-radikala.</p><p>Na osnovu LC&ndash;MS/MS (ESI+) merenja ustanovljeno je prisustvo nekoliko&nbsp;intermedijera: 3,6-dihlor-piridin-2-ol, 3,6-dihlor hidroksipiridin-2-karboksilna kiselina i&nbsp;3,3&#39;,6,6&#39;-tetrahlor-2,4&#39;-bipiridin-2&#39;-karboksilna kiselina. Na osnovu identifikovanih&nbsp;intermedijera, kao i kinetičkih rezultata, predložen je mogućput mehanizma fotokatalitičke&nbsp;razgradnje klopiralida.</p><p>Prilikom ispitivanja uticaja strukture molekula na brzinu razgradnje, konstatovano&nbsp;<br />je da u slučaju klopiralida praktično ne dolazi do fotokatalitičke razgradnje u prisustvu&nbsp;TiO_2&nbsp;(anataze) i N-TiO_2&nbsp;(sintetisani suvim putem) uz primenu vidljive svetlosti, kao i u&nbsp;slučaju TiO_2&nbsp;Degussa P25. Pored toga, primenom TiO_2&nbsp;(rutil) i Fe-TiO_2&nbsp;kao&nbsp;fotokatalizatora, sa povećanjem količine Fe³⁺-jona od 0,13 do 1,27 at.% raste brzina&nbsp;razgradnje klopiralida, ukazujući da strukturne osobine supstrata utiču na brzinu njihove&nbsp;razgradnje.</p> / <p>It is well known that RS-2-(4-chloro-o-tolyloxy)propionic acid (MCPP), (4-chloro-2- methyl-phenoxy)acetic acid (MCPA) and 3,6-dichloropyridine-2-carboxylic &nbsp;acid&nbsp;(clopyralid) are herbicides of wide activity spectrum. They are soluble in water, hardly&nbsp;biodegradable and, unfortunately, often present in drinking water.</p><p>Heterogeneous photocatalysis by application of TiO_2&nbsp;and UV radiation proved to&nbsp;be very suitable for their removal from water. However, due toits large energy gap, i.e.&nbsp;3.2 &nbsp;eV (anatase-form) and 3.0 eV (rutile-form), a very small fraction of sunlight in the near&nbsp;UV range (about 3&ndash;4%) is used during photocatalytic process, which is an indication of&nbsp;TiO_2&nbsp;inactivity in the presence of this light source. Some literature data report on the&nbsp;possibility of photodegradation of certain substrates by visible light in the presence of&nbsp;TiO₂. MCPP served as substrate for testing TiO_2&nbsp;Degussa P25 &nbsp;photocatalytic activity in the&nbsp;presence of visible light. On the basis of reflection spectra it was established that MCPP&nbsp;adsorbed on TiO_2&nbsp;Degussa P25 was absorbing visible spectrum radiation (&lambda; &ge;400 nm).&nbsp;The existence of thus formed &nbsp;charge-transfer complex was confirmed with FTIR analysis.&nbsp;The efficiency of &nbsp;TiO_2&nbsp;Degussa P25 with application of visible light was compared to&nbsp;sunlight and UV radiation, as well to directphotolysis in the presence of these light&nbsp;sources. The rate of MCPP photocatalytic degradation by means of visible light is&nbsp;0.86 &mu;mol dm^{&minus;3&nbsp;}min^&minus;1, which is about 4 times faster than direct photolysis. In addition, the&nbsp;optimal &nbsp;catalyst concentration of about 8 mg cm^&minus;3, much higher than using UV radiation,&nbsp;<br />was established. The reason is, probably, a different mechanism of &nbsp;hotodegradation &nbsp;in the&nbsp;presence of visible and UV irradiation. Namely, the presence of 2-methyl-2-propanol&nbsp;(well-known&nbsp;^&bull;OH radical scavenger) has practicallyno effect on the rate of &nbsp;MCPP&nbsp;photocatalytic degradation using visible light, which points that this degradation&nbsp;mechanism does not involve&nbsp;^&bull;OH radicals, in contrast to that established &nbsp;for UV radiation.</p><p>Since the catalyst TiO_2&nbsp;Degussa P25 with application of visible light was not very&nbsp;<br />efficient in degradation of all three herbicidesand in view that nowadays is very &nbsp;popular&nbsp;doping process of TiO₂ with different types of metals (alkali, alkaline-earth, transition, etc.)&nbsp;and non-metals (halogen, chalcogen, etc.), in the scope of this Ph.D. &nbsp;thesis activities of N-TiO_2&nbsp;(synthesized by wet and dry procedure) and TiO_2&nbsp;(rutile) doped with various amounts&nbsp;of Fe^3+&nbsp;(0.13&ndash;1.48 at.%) in degradation processes of &nbsp;herbicides MCPP and MCPA using&nbsp;visible light were studied. In addition, the efficiency of TiO_2&nbsp;(anatase) doped with various&nbsp;amounts of Fe^3+&nbsp;(0.71&ndash;1.80 at.%) was also tested for MCPP degradation. When comparing&nbsp;N-TiO_2&nbsp;(synthesized by wet procedure) and N-TiO₂ (dry procedure), it was observed that&nbsp;in the latter case the catalyst efficiency was about two times higher. In this case for MCPP&nbsp;was also observed somewhat higher photocatalytic activity of N-TiO₂ (synthesized by dry&nbsp;procedure) in comparison with TiO₂. When activities of all three catalysts towards MCPA&nbsp;are compared, the results are very alike. In addition, higher efficiency of N-TiO_{2 &nbsp;}(wet&nbsp;procedure) comparing to TiO_2&nbsp;Degussa P25 (about 1.5 times) and about 5 times in&nbsp;comparison to direct photolysis were recorded, while N-TiO₂ (dry procedure) was about 3&nbsp;times more efficient than TiO_2&nbsp;Degussa P25 and about 10 times in comparison with direct&nbsp;photolysis. The rate of solar degradation is about 100 times lower than by application of&nbsp;UV and visible radiation, as a consequence of various intensities of the mentioned light&nbsp;sources and different conditions of photodegradation. An optimal concentration of N-TiO₂&nbsp;(wet procedure) of 4 mg cm^&minus;3<br />&nbsp;was established.</p><p>During degradation of MCPP and MCPA it was observed that the rate is higher if&nbsp;TiO₂(rutile) was applied comparing to Fe-TiO_2&nbsp;and with increasing amount of Fe^3+&nbsp;photocatalytic activity mostly decreases. When TiO₂ (anatase) doped with various amounts&nbsp;of Fe^3+&nbsp;(0.71 to 1.80 at.%) was applied for MCPP degradation, the process was much&nbsp;slower than with undoped catalyst.</p><p>Since we have not found relevant literature data on kinetics and mechanism of&nbsp;photocatalytic degradation of clopyralid, its stability in different experimental conditions&nbsp;was tested. In investigating of influences of pH (1.0&ndash;9.0) both in presence and in absence&nbsp;of daylight, in no cases decomposition was observed during seven months experiments.&nbsp;Also, the kinetics of photocatalytic degradation of clopyralid using UV and visible&nbsp;irradiation in the presence of TiO_2&nbsp;Degussa P25 and in direct photolysis by application of&nbsp;both irradiation sources was studied. It was found that the &nbsp;rate of photocatalytic&nbsp;decomposition using UV radiation was 5 times higher comparing to direct photolysis. For&nbsp;clopyralid photocatalytic monitoring a pH value of &nbsp;3.2 was chosen. In addition, in the investigated concentration range (0.5&ndash;3.0 mmol &nbsp;dm^&minus;3) the photocatalytic degradation kinetics of clopyralid in the first stage of the reaction follows approximately a pseudo-first kinetic order. In investigation of influence of catalyst concentration (0.5&ndash;8 mg cm^&minus;3) on the rate of clopyralid degradation the highest reaction rate was observed at 4 mg cm^{&minus;3&nbsp;}of catalyst concentration The apparent activation energy of the reaction being 7.74 kJ mol^&minus;1. The absence of molecular oxygen resulted in a significant decrease (about 2 times) in the rate of clopyralid photodegradation. The effect of the presence of (NH₄)₂S₂O₈, H₂O_2&nbsp;and KBrO₃, acting as electron acceptors along with molecular oxygen affects clopyralid photocatalytic degradation considerably and indifferent ways. By studying the effect of ethanol as a hydroxyl radical scavenger it was shown that the heterogeneous catalysis takes place mainly via ^&bull;OH radicals.</p><p>LC&minus;MS/MS (ESI+) monitoring of the process showed that several pyridine-containing intermediates are formed: 3,6-dichloropyridin-2-ol, 3,6-dichloro&nbsp;hydroxypyridine-2-carboxylic acid and 3,3&#39;,6,6&#39;-tetrachloro-2,4&#39;-bipyridine-2-carboxylic&nbsp;acid. Based on the identified intermediates and overall kinetic results, a probable&nbsp;photocatalytic degradation mechanism was proposed.&nbsp;</p><p>Finally, in the case of clopyralid it was established that practically no degradation&nbsp;<br />occurs in the presence of TiO_2&nbsp;(anatase) and N-TiO₂ (dry procedure) with visible light &nbsp;and&nbsp;also with TiO_2&nbsp;Degussa P25. Besides of that, by using TiO_2&nbsp;(rutile) and Fe-TiO_2&nbsp;as&nbsp;photocatalysts it was noted that increasing the concentration of Fe^3+&nbsp;from 0.13 to 1.27 at.%&nbsp;comes to increasing photodegradation rate of clopyralid. Results indicate that differences&nbsp;in molecular structure of chosen compound, influence obtained photocatalytic activity to a&nbsp;great extent.</p>