Is cavitation a truly sensible choice for intensifying photocatalytic oxidation processes? – Implications on phenol degradation using ZnO photocatalysts

Varaha P. Sarvothaman, Vijay K. Velisoju, Janardhanraj Subburaj, Mebin S. Panithasan, Shekhar R. Kulkarni, Pedro Castaño, James Turner, Paolo Guida, William L. Roberts, Sanjay Nagarajan

Research output: Contribution to journalArticlepeer-review

6 Citations (SciVal)

Abstract

Phenols are recalcitrant compounds that constitute the majority of organic contaminants in industrial wastewaters. Their removal at large scales require a combination of various processes to reach the desired discharge quality. An extensive body of work has already been published in the area of phenol removal from wastewater, however none of them have focussed on a truly ‘sensible’ approach for coupling advanced oxidation processes (AOPs). Rather, a higher removal efficiency was targeted by unduly complicating the process by combining multiple AOPs. The most influential AOP as the primary method typically driven by the nature of the pollutant should form the basis for a hybrid AOP followed by a complementary AOP to intensify the oxidation process. This strategy is lacking in current literature. We address this knowledge gap directly by systematically identifying the best hybrid process for ZnO mediated photocatalysis of phenol. Either a cavitation mediated pre-treatment of ZnO or cavitation-photocatalysis-peroxide based hybrid AOP was investigated. While the pre-treatment approach led to >25% increase in phenol oxidation compared to bare ZnO photocatalysis, the hydrodynamic cavitation-photocatalysis-peroxide based system was found to have a cavitational yield 5 times higher than its acoustic cavitation counterpart. A new phenomenon known as the ‘pseudo staggered effect’ was also observed and established in hydrodynamic cavitation mediated photocatalysis-peroxide hybrid process for the first time. While we demonstrated that cavitation is a truly ‘sensible’ choice to enhance photocatalysis, the nature of the pollutant under investigation must always be the key driver when designing such hybrid AOPs.
Original languageEnglish
Article number106548
Number of pages11
JournalUltrasonics Sonochemistry
Volume99
Early online date3 Aug 2023
DOIs
Publication statusPublished - 31 Oct 2023

Bibliographical note

Acknowledgements:
The authors gratefully acknowledge the financial support, resources, and facilities provided by the Clean Combustion Research Center (CCRC) of the King Abdullah University of Science and Technology (KAUST) under the research grant URF/1/4079/01/01. This research utilized the resources of the Core Labs at KAUST. The authors thank Gerard Clancy for his work on analytical chemistry.

Data availability:
The authors are unable or have chosen not to specify which data has been used.

Keywords

  • Cavitation
  • Hybrid processes
  • Peroxide
  • Phenol
  • Photocatalysis
  • Wastewater treatment

ASJC Scopus subject areas

  • Chemical Engineering (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Inorganic Chemistry
  • Acoustics and Ultrasonics
  • Environmental Chemistry
  • Organic Chemistry

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