Influence of synthesis parameters on photocatalytic activity of ZnO coatings

U ovom radu eksperimentalno je ispitan utjecaj parametara priprave ZnO prevlaka na njihovu fotokatalitičku aktivnost kod razgradnje zagađivala iz vode. Kao modelno zagađivalo korištena je 2,5-dihidroksibenzojeva kiselina koja je metabolički produkt razgradnje acetilsalicilne kiseline. Prevlake ZnO dobivene su metodom kemijskog taloženja iz otopine cinkova acetata dihidrata u metanolu, pri dvije kombinacije parametara priprave (temperatura, koncentracija matične otopine i vrijeme stajanja u sušioniku). Pri tom nastaje slojeviti bazični cinkov acetat (LBZA) koji potom žarenjem u peći prelazi u čisti ZnO, zadržavajući morfologiju LBZA. SEM analiza potvrdila je cvjetićavu strukturu prevlaka. Ispitane su tri temperature žarenja. Kao izvori svjetlosti kod fotokatalitičke reakcije korišteni su UV lampa i sunčeva svjetlost, a promjena koncentracije zagađivala praćena je pomoću UV/Vis spektrofotometrije. Sustavi su pokazali manje ili više pravilno smanjenje koncentracije zagađivala, što potvrđuje fotokatalitičko djelovanje ZnO. Iz rezultata je teško odabrati optimalne uvjete priprave za fotokatalitičku primjenu, odnosno nije uočen utjecaj istih na fotokatalitičku aktivnost. Fotodegradacija zagađivala pod sunčevom svjetlosti pokazala se približno jednako djelotvornom kao i pod UV lampom što pokazuje potencijal ovakvih sustava za pročišćavanje voda na otvorenom.In this thesis, the influence of synthesis parameters of ZnO films on their photocatalytical activity for degradation of water pollutants was experimentally tested. 2,5-dihidroxybenzoic acid, which is a metabolic product of acetylsalicylic acid degradation, was used as a model pollutant. ZnO coatings were prepared by chemical bath deposition method from an alcoholic solution of zinc acetate dihydrate, at two different combinations of preparation parameters (temperature, initial Zn concentration and time). Layered Basic Zinc Acetate (LBZA) is formed and then transformed to pure ZnO by calcining, keeping its LBZA morphology. The obtained films had flower-like structure, which was confirmed by SEM analysis. Three calcining temperatures were examined. UV lamp and sunlight were used as light sources in photocatalytic reaction, and change in pollutant concentration was monitored by UV/Vis spectrophotometry. The result was more or less regular concentration reduction, which confirms the photocatalytic activity of ZnO. It is difficult to choose the optimum preparation conditions for photocatalytic application based on the results. The specific influence of the synthesis parameters on photocatalytic activity was not observed. Photodegradation of the given pollutant was approximately as effective under sunlight as under the UV lamp, showing the potential of such outdoor water purification systems