Study of the insitu synthesis conditions of PEDOT/TiO2 composite catalyst; validation of photocatalytic activity during wastewater treatment

Organska sintetska bojila predstavljaju onečišćenje okoliša koje potječe iz tekstilne industrije i industrije boja te se smatraju nerazgradivima. Konvencionalni procesi razgradnje ne mogu ukloniti bojila iz otpadnih voda no napredni oksidacijski procesi (engl. Advanced oxidation processes, AOPs), uključujući fotokatalizu, predstavljaju metode obrade vode koje mogu obezbojiti otpadne vode i potpuno razgraditi organske spojeve. Titanijev dioksid često se koristi kao fotokatalizator, ali njegova široka zabranjena zona (3,2 eV) ograničava njegovu fotokatalitičku aktivnost na UV dio spektra. Vodljivi polimeri, kao na primjer poli(3,4– etilendioksitiofen) (PEDOT), služe kao aktivatori TiO2 proširujući njegovu fotokatalitičku aktivnost u vidljivi dio spektra Sunčeva zračenja. U ovom radu, kemijskom oksidacijskom polimerizacijskom metodom sintetiziran je nanokompozitni fotokatalizator PEDOT/TiO2. Ispitan je utjecaj različitih oksidansa, amonijevog persulfata (APS) i željezovog (III) klorida (FeCl3) na strukturu nanokompozitnog fotokatalizatora, što je rezultiralo različitom fotokatalitičkom aktivnošću. Provedena je karakterizacija sintetiziranih nanokompozitnih fotokatalizatora. FT–IR spektroskopijom određen je kemijski sastav sintetiziranih nanokompozita, rendgenskom difrakcijskom analizom određena je kristalna struktura, pretražnom elektronskom mikroskopijom morfološka struktura te termogravimetrijskom analizom udio polimera u nanokompozitima. Fotokatalitička aktivnost proučavana je praćenjem uklanjanja bojila Reactive Red 45 (RR45) i Acid Blue 43 (AB43) pod UV–A zračenjem. Uklanjanje bojila i promjena obojenja u vodi praćeni su mjerenjem apsorbancije UV/Vis spektrofotometrom. Karakterizacijom je potvrđeno da su uspješno sintetizirani PEDOT/TiO2(APS) i PEDOT/TiO2(FeCl3) nanokompozitni fotokatalizatori. Sintetizirani fotokatalizatori su pokazali dobru učinkovitost uklanjanja bojila, ali putem adsorpcije te zbog toga nije bilo moguće odrediti fotokatalitičku aktivnost.Organic synthetic dyes represent environmental pollution coming from textile and dye industry and are considered non–degradable. Common degradation processes are not able to remove dyes from the wastewaters but advanced oxidation processes (AOPs), as photocatalysis, represent water treatment methods that are able to decolourize and to fully degrade organic compounds. Titanium dioxide is widely used as photocatalyst but its wide band gap of 3,2 eV restricts its photocatalytic activity so it is active only under UV light. Conducting polymers, as poly(3,4–ethylenedioxythiophene) (PEDOT), can act as activators of TiO2 under solar light irradiation. In this paper, a nanocomposite photocatalyst PEDOT/TiO2 was synthesized by chemical oxidative polymerization method. The effect of the various oxidants, ammonium persulfate (APS) and iron (III) chloride (FeCl3), on the structure of nanocomposite photocatalyst was studied, resulting in different photocatalytic activity. Characterization of synthesized nanocomposite photocatalysts was performed. FT–IR spectroscopy was used to determine the chemical composition of the synthesized nanocomposites, X–ray diffraction analysis was used to analyse the crystal structure, scanning electron microscopy was used for morphological structure and thermogravimetric analysis was used to determine the polymer content of the nanocomposites. Photocatalytic activity was studied by monitoring the removal of dyes, Reactive Red 45 (RR45) and Acid Blue 43 (AB43) under the UV–A irradiation. Removal of dyes and their change of discoloration in the water were monitored by measuring the absorbance with UV/Vis spectrophotometer. Characterization confirmed that PEDOT/TiO2(APS) and PEDOT/TiO2(FeCl3) nanocomposite photocatalysts were successfully synthesized. The synthesized photocatalysts showed high dye removal efficiency, mainly through adsorption therefore it was not possible to determine the photocatalytic activity