PVP-assisted synthesis of rod-like ZnO photocatalyst for photodegradation of reactive red (RR141) and Congo red (CR) azo dyes
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A ZnO photocatalyst has been synthesized via a hydrothermal method using polyvinylpyrrolidone (PVP) as a capping agent. The ZnO catalyst shows hexagonal wurtzite structure with a rod-like microstructure (0.58 μm × 2.47 μm, from TEM) due to the assembly of many crystallites. An excitonic peak found in photoluminescence (PL) spectrum at 367 nm indicates a significant improvement of sample crystallinity after calcination. The catalyst showed a remarkable photocatalytic efficiency of 100% toward degradation of two azo dyes. High crystallinity together with low electron–hole recombination rate found in the catalyst promoted its enhanced photodegradation efficiency. The degradation reaction showed first-order kinetics with a rate constant of 0.0186 min−1. Both electron and superoxide anion radical play the most important role involved in photodegradation of the dye. The second majority comes from hydroxyl radical (OH·) which also made a huge contribution toward photodegradation of the dye. The ZnO catalyst remained stable after three cycles of use. The catalyst showed approximately the same efficiency even after the third run. This work demonstrates the promising potential of ZnO photocatalyst for environmental remediation.
Materials Chemistry Research Center, Department of Chemistry and Center of Excellence for Innovation in Chemistry (PERCH-CIC), Faculty of Science, Khon Kaen University is gratefully acknowledged. T. Chankhanittha acknowledges the fund from SAST. J. Watcharakitti would like to thank DPST scholarship from the Royal Thai Government. S. Nanan also wishes to thank partial fund from Research and Academic Affairs Promotion Fund (RAAPF), Faculty of Science, Khon Kaen University, Fiscal year 2019. This study was partially supported by Research and Technology Transfer Affairs of Khon Kaen University (promotion of using Synchrotron radiation in basic research, Fiscal year 2018). The authors would like to thank the Synchrotron Light Research Institute, SIRI (Public Organization), Nakhon Ratchasima, Thailand for generous beamtime (BL5.3, XPS experiment).
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