doktorska disertacija
Boštjan Žener (Author), Romana Cerc Korošec (Mentor), Urška Lavrenčič Štangar (Thesis defence commission member), Marija Bešter-Rogač (Thesis defence commission member), Andrijana Sever Škapin (Thesis defence commission member)

Abstract

V zadnjih desetletjih postaja dostop do čiste vode vse večja težava, ki jo lahko pripišemo eksponentni rasti prebivalstva in industrializaciji, zaradi česar se je pojavila potreba po ponovni uporabi očiščenih vod. V ta namen je bilo razvitih veliko metod za čiščenje odpadnih voda, ki pa so lahko pri odstranjevanju težje odstranljivih organskih onesnažil manj učinkovite ali celo neučinkovite. Enega največjih problemov predstavljajo odpadne vode v tekstilni industriji, saj so se konvencionalne metode čiščenja izkazale kot zelo neučinkovite pri odstranjevanju tekstilnih barvil, zaradi česar odpadne vode ostanejo obarvane. To lahko vodi do sprememb v bioloških ciklih vodnih organizmov, saj obarvanost preprečuje dostop sončne svetlobe in s tem zmožnost poteka fotosinteze v takem deležu, kot le-ta poteka v prosojni vodi. Zaradi tega se je pojavila potreba po razvoju tehnologije, ki bi lahko učinkovito odstranila onesnažila, prisotna v odpadnih vodah. Fotokataliza se je zaradi svoje zmožnosti popolne mineralizacije organskih onesnažil (razgradnja do CO2 in H2O) na tem področju izkazala za zelo obetavno metodo. Proces fotokatalize temelji na osvetljevanju fotokatalizatorja s svetlobo določene valovne dolžine, ki vzbudi elektrone iz valenčnega v prevodni pas, pri čemer v valenčnem pasu nastanejo elektronske vrzeli. Generirani nosilci naboja nato potujejo do površine fotokatalizatorja, kjer preko nastalih močno reaktivnih specij reagirajo z adsorbiranim onesnažilom in posledično katalizirajo njegovo razgradnjo. Pri fotokatalizi se kot fotokatalizator najpogosteje uporablja TiO2. Zaradi širine njegovega prepovedanega pasu med (3,2 eV za anatas) lahko fotokatalitske reakcije potekajo predvsem pri osvetljevanju s svetlobo z valovno dolžino, nižjo od 390 nm (UV območje). Zaradi tega je bilo v zadnjih desetletjih veliko raziskav posvečenih zoževanju prepovedanega pasu TiO2, s čimer bi se povečala njegova fotokatalitska aktivnost pri osvetljevanju z vidno svetlobo. V dokrorskem delu delu sem se ukvarjal s sintezo TiO2, ki bi imel čim višjo fotokatalitsko aktivnost pri osvetljevanju z vidno svetlobo, kar sem dosegel z dopiranjem z nekovinami in kovinami. Vzorci TiO2 so bili pripravljeni s sol-gel sintezo, z uporabo TiCl4 kot prekurzorja (anorganska pot). Stabilnost solov sem dosegel z ustrezno nizko vrednostjo pH, kar sem dosegel z nakisanjem z uporabo različnih kislin (HCl in H2SO4). V vzorce sem dodal še različne dopante, ki so delovali kot vir dopiranega dušika (sečnina, NH4NO3), žvepla (tiosečnina) in platine (H2PtCl6). Pripravljene raztopine sola sem nato z uporabo tehnike potapljanja (dip-coating) nanesel na objektna stekelca in silicijeve rezine, kristalizacijo amorfnega TiO2 pa sem dosegel s termično obdelavo v komorni peči. Prahove sem pripravil s sušenjem raztopine sola do kserogela in nadaljnjo termično obdelavo v komorni peči. Fotokatalitska učinkovitost tankih plasti pri osvetljevanju z UV in vidno svetlobo sem določil z meritvami hitrosti razgradnje organskega barvila Plasmocorinth B, ki se veliko uporablja v tekstilni industriji. Fotokatalitsko aktivnost prahov je bila določena z merjenjem hitrosti oksidacije izopropanola v aceton. Strukturne in morfološke lastnosti tankih plasti in ustreznih prahov so bile določene z uporabo različnih karakterizacijskih metod. Prav tako sem z uporabo različnih tehnik (kromatografija, meritve pH in prevodnosti) določil mehanizem razgradnje Plasmocorinth B. Ugotovil sem, da so strukturne in morfološke lastnosti tankih plasti in prahov odvisne od vrste in količine dodane kisline, dopanta in temperature termične obdelave. Vsi omenjeni parametri imajo velik vpliv na fotokatalitsko aktivnost tankih plasti in prahov. Vzorci, dopirani in ko-dopirani s kovinami in nekovinami imajo veliko višjo aktivnost pri osvetljevanju z UV in vidno svetlobo. Najbolj aktivni so bili vzorci, kodopirani z dušikom in žveplom, modificirani s platino.

Keywords

titan;tanke plasti;sinteza tankih plasti;sol-gel postopek;karakterizacija tankih plasti;fotokatalizatorji;fotokatalitska aktivnost;čiščenje odpadnih voda;doktorske disertacije;

Data

Language: Slovenian
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher: [B. Žener]
UDC: 544.526.5(043.3)
COBISS: 302135552 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Optimization of the preparation and structural properties of doped nanosized titanium dioxide
Secondary abstract: Access to clean water has become a major problem in the last decades. This is due to the exponential growth of human population and industrialization. Because of this, the need for reuse of treated waste waters has arisen. A lot of methods for waste water treatment have been developed, but they can be inefficient for the degradation of persistent organic pollutants. A major environmental problem are textile industry effluents since conventional treatment methods are not able to remove textile dyes from waste waters. Because of that, waste waters remain colored, which can alter biological cycles of water organisms, by blocking access of sunlight and consequentially blocking photosynthesis. There is therefore a need for the development of a method, which could efficiently degrade pollutants present in textile industry waste waters. Because of its ability to completely oxidize organic pollutants to CO2 and H2O, photocatalysis has emerged as a promising technique for waste water treatment. The term photocatalysis is used to describe a process during which light of a certain wavelength excites an electron from the valence band onto the conductive band of a photocatalyst. The resulting charge carriers (electron and hole) then travel to the surface of the photocatalyst, where they can catalyze the degradation of adsorbed organic pollutants. Because of its advantageous properties, titanium dioxide (TiO2) has been one of the most widely used photocatalysts. One of the main drawbacks of TiO2 is the width of its band gap (3.2 eV for anatase), which means that an electron can only be excited onto the conduction band when illuminated with UV light with a wavelength lower than 390 nm. A lot of studies have focused on narrowing the width of the band gap of TiO2, which would increase its photocatalytic activity under visible light illumination. In my research work, I focused on preparing TiO2 with high photocatalytic activity under visible light illumination. This was achieved by non-metal and metal doping. Samples were synthesized using a sol-gel synthesis with titanium tetrachloride as a precursor (inorganic path). During the synthesis, solutions were acidified with two different acids (HCl and H2SO4). To increase the activity of TiO2 under visible light illumination, diferent dopants, acting as a source of doped nitrogen (NH4NO3, urea), sulfur (thiourea) and platinum (H2PtCl6), were added. Afterward, the prepared sols were deposited onto object glasses using dip-coating and thermally treated in a muffle furnace to promote crystallization. Corresponding powders were prepared by drying the prepared sols, followed by thermal treatement in a muffle furnace. Photocatalytic activity of the prepared thin films was tested by observing the degradation rate of Plasmocorinth B textile dye. The photocatalytic activity of powders was determined by observing the rate of isopropanol to acetone oxidation. Thin films and corresponding powders were characterized by various techniques. Moreover, the degradation mechanism of Plasmocorinth B was determined using various techniques (chromatography, pH and conductivity). Results of these characterization techniques have shown that the type and amount of acid and dopant used and also the temperature of thermal treatment have a large effect on the structural, surface and morphological properties and consequentially the photocatalytic activity of thin films and corresponding powders. Results have shown a significant increase in activity in samples, doped and co-doped with metals and non-metals, under UV and visible light illumination. The highest activity was observed in samples, co-doped with nitrogen and sulfur and modified with platinum.
Secondary keywords: Titanov dioksid;Disertacije;Sinteza;Fotokataliza;
Type (COBISS): Doctoral dissertation
Study programme: 1000381
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo
Pages: XXIII, 136 str.
ID: 11236757