Influence of Polypyrrole Conductivity in Composite Photocatalyst on Decomposition Efficiency of Dyes in Wastewater

Titanijev dioksid (TiO2) pripremljen je sol-gel sintezom, a okarakteriziran je rendgenskom difrakcijskom analizom (XRD) te skenirajućom elektronskom mikroskopijom (SEM). Kompozitni fotokatalizator pripremljen je in-situ sintezom vodljivog polimera polipirola (PPy) uz prisutnost titanijevog dioksida (TiO2). Sinteza polimera provedena je kemijskom oksidacijskom polimerizacijom monomera pirola (Py) uz željezov (III) klorid (FeCl3) kao oksidans. Tako,sintetizirani kompozitni fotokatalizator (PPy/TiO2) modificiran (deprotoniran) je namakanjem različito vrijeme u amonijevom hidroksidu (NH4OH) različitih koncentracija. Proces reprotoniranja proveden je namakanjem u 0,01 M klorovodničnoj kiselini (HCl) različito vrijeme s ciljem oporavka elektrovodljivosti PPy u kompozitu. Karakterizacija kompozitnih fotokatalizatora provedena je infracrvenom spektroskopijom s Fourierovim transformacijama (FTIR), termogravimetrijskom analizom (TGA) te im je određena elektrovodljivost. Fotokatalitička učinkovitost sintetiziranih kompozitnih fotokatalizatora prije i nakon modifikacije ispitana je praćenjem uklanjanja azo bojila Reactive Red 45 (RR45) pod simuliranim Sunčevim zračenjem. Stupanj obezbojenja vodene otopine praćen je mjerenjem promjene apsorbancije UV/Vis spektroskopijom dok je proces mineralizacije (potpune razgradnje) RR45 bojila određivan pomoću ukupnog organskog ugljika (TOC). Rezultati su pokazali da deprotoniranjem dolazi do smanjene elektrovodljivosti PPy u kompozitnom fotokatalizatoru i da se postupkom reprotoniranja ona djelomično oporavlja. Također, pokazali su da promjena vodljivost PPy utječe na fotokatalitičku aktivnost, tj. fotodegradaciju RR45 azo boja.Titanium dioxide (TiO2) was prepared by salt-gel synthesis and characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The composite photocatalyst was prepared by in situ synthesis of a conductive polymer polypyrrole (PPy) with the presence of titanium dioxide (TiO2). Synthesis of the polymer was carried out by chemical oxidation polymerization of pyrrole monomer (Py) with iron (III) chloride (FeCl3) as oxidant. The synthesized composite photocatalyst (PPy / TiO2) was modified (deprotonated) by soaking in ammonium hydroxide (NH4OH) of different concentrations for a different time. The reprotonation process was conducted by soaking in 0.01 M hydrochloric acid (HCl) at different times with the aim to recover the conductivity of PPy in the composite. The characterization of composite photocatalysts was performed by infrared spectroscopy with Fourier transforms (FTIR), thermogravimetric analysis (TGA) and by determination of the conductivity. The photocatalytic efficiency of synthesized composite photocatalysts before and after modification was tested by monitoring the removal of azo dye Reactive Red 45 (RR45) under simulated solar irradiation. The discoloration of water was monitored by measuring the change of absorbance by UV / Vis spectroscopy while the mineralization process (complete degradation) of the RR45 dye was determined by total organic carbon (TOC). The results show that the deprotonation resulted in decrease of PPy conductivity in the composite photocatalyst and is partially recovered by the reprotonation process. They also show that change in PPy conductivity has the influences on the photocatalytic activity, i.e. photodegradation of RR45 azo dye, which was lower