Stability and Synergistic Effect of Polyaniline/TiO₂ Photocatalysts in Degradation of Azo Dye in Wastewater.

Mark Žic,Jadranka Travas-Sejdic,Katarina Novaković,Zlata Hrnjak-Murgić,Marijana Kraljić Roković,Vanja Gilja

doi:10.3390/nano7120412

Mark Žic, Jadranka Travas-Sejdic + Show 4 more

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https://doi.org/10.3390/nano7120412

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Abstract

The polyaniline/TiO2 (PANI/TiO2) composite photocatalysts were prepared by the in situ chemical oxidation of aniline (An) in the presence of TiO2 particles. For this purpose, photocatalysts with different amounts of PANI polymer were prepared and analysed. Fourier-transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis indicated successful synthesis of the PANI polymer and its conductivity was also determined. The micrographs of field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to explain the impact of the aniline amount on the aggregation process during the synthesis of the composites. The smallest size of aggregates was obtained for the photocatalysts with 15% of PANI (15PANI/TiO2) due to the formation of homogenous PANI. The photocatalytic activity of studied PANI/TiO2 photocatalysts was validated by monitoring the discoloration and mineralization of Reactive Red azo dye (RR45) in wastewater. The 15PANI/TiO2 sample presented the highest photocatalytic efficiency under ultraviolet A (UVA) irradiation, in comparison to pure TiO2. This was explained by the formation of uniformly dispersed PANI on the TiO2 particles, which was responsible for the synergistic PANI-TiO2 effect.

Highlights

Organic synthetic dyes (e.g., Reactive Red (RR45)), originating from textile and dye industries, are among prominent environmental pollution factors
The effect of aggregation processes were enlightened while studding the sample morphology by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images
It was concluded that the optimal aniline amount omitted the production of imperfections, and at the same time, it provided an effective barrier to TiO2 nanoparticle aggregation

Summary

Introduction

Organic synthetic dyes (e.g., Reactive Red (RR45)), originating from textile and dye industries, are among prominent environmental pollution factors. One of the most efficient approaches to degrading organic dye is to apply advanced oxidation processes (AOPs), with the aim of converting dyes to non-toxic and non-hazardous species that can be released in the environment [2]. Photocatalysis is a widely studied process, which utilizes light to activate semiconductor metal oxide catalysts. The relatively high band gap (3.2 eV) of TiO2 [6] restricts its photocatalytic activity under visible light (Vis), whereas its poor quantum efficiency, due to recombination of electrons (eCB−) and holes (hVB+) [7], is another disadvantage

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