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Deprotonation and Loss of the Conductivity of PPy/TiO2 Nanocomposite Photocatalyst under Alkaline Conditions for Photocatalytic Application

By in-situ chemical oxidation polymerization polypyrrole/titanium dioxide (PPy/TiO2) nanocomposite photocatalysts were prepared for photocatalytic wastewater purification under simulated solar irradiation. To enhance TiO2 photoactivity under visible light and to reduce economic expenses during wastewater treatment PPy conductive polymer was applied. Conductive PPy polymers with extending conjugated electron systems act as stable photosensitizers injecting electrons into the conduction band of TiO2 (due to their π conjugated electrons). This study aimed to elucidate the stability and loss of conductivity under alkaline conditions during photocatalysis. The deprotonation, which is responsible for conductivity reduction, is discussed on the bases of salt–base transition in polypyrrole due to treatment of nanocomposite by ammonium hydroxide (NH4OH). The stability towards the loss of conductivity by deprotonation was validated by measuring the electrical conductivity and photocatalytic activity. Further, studied PPy/TiO2 nanocomposite photocatalysts were characterized by FTIR and UV/Vis spectroscopy, TG analysis and SEM microscopy. Photocatalytic activity of PPy/TiO2 nanocomposite photocatalysts was estimated by monitoring the discoloration of Reactive Red (RR45) azo dye in wastewater by UV/Vis spectrophotometer at the maximum wavelength (λmax=542 nm). The kinetics of photocatalytic degradation rate of RR45 was studied as well. The mineralization process was followed by determination of total organic carbon (TOC). From the results it was concluded that deprotonation process significantly decreased the conductivity of PPy/TiO2 nanocomposite photocatalysts since the conductivity of 17.6 S/cm was observed after in-situ synthesis and 7.1 x 10-5 S/cm was notified after the deprotonation. The consequence of deprotonation was also lower photocatalytic degradation rate of RR45 dye in wastewater purification.

PPy/TiO2, nanocomposite, deprotonation, conductivity, photocatalysis,

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