title: Advanced oxidation degradation kinetics as a function of ultraviolet LED duty cycle.
abstract: Ultraviolet (UV) light emitting diodes (LEDs) may be a viable option as a UV light source for advanced oxidation processes (AOPs) utilizing photocatalysts or oxidizing agents such as hydrogen peroxide. The effect of UV-LED duty cycle, expressed as the percentage of time the LED is powered, was investigated in an AOP with hydrogen peroxide, using methylene blue (MB) to assess contaminant degradation. The UV-LED AOP degraded the MB at all duty cycles. However, adsorption of MB onto the LED emitting surface caused a linear decline in reactor performance over time. With regard to the effect of duty cycle, the observed rate constant of MB degradation, after being adjusted to account for the duty cycle, was greater for 5 and 10% duty cycles than higher duty cycles, providing a value approximately 160% higher at 5% duty cycle than continuous operation. This increase in adjusted rate constant at low duty cycles, as well as contaminant fouling of the LED surface, may impact design and operational considerations for pulsed UV-LED AOP systems.
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: Kelsey
authors.initials: K
authors.lastname: Duckworth
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Spencer
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: Christopher
authors.initials: C
authors.lastname: Bates
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Miller
authors.affiliation: Chemical Paper and Biomedical Engineering Dept, Miami University, Oxford, OH 45056, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Almquist
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: Michael
authors.initials: M
authors.lastname: Grimaila
authors.affiliation: National Homeland Security Research Center, Water Infrastructure Protection Division, US Environmental Protection Agency, 26 W. Martin Luther King Dr., Mailstop NG-16, Cincinnati, OH 45268, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Magnuson
authors.affiliation: National Homeland Security Research Center, Water Infrastructure Protection Division, US Environmental Protection Agency, 26 W. Martin Luther King Dr., Mailstop NG-16, Cincinnati, OH 45268, USA.
authors.forename: Stuart
authors.initials: S
authors.lastname: Willison
authors.affiliation: Oak Ridge Institute of Science and Education, US Environmental Protection Agency, 26 W. Martin Luther King Dr., Mailstop NG-16, Cincinnati, OH 45268, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Phillips
authors.affiliation: Department of Systems Engineering and Management, Air Force Institute of Technology, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA E-mail: michael.miller@afit.edu.
authors.forename: LeeAnn
authors.initials: L
authors.lastname: Racz
mesh_terms: D006861:Hydrogen Peroxide / Q000737:chemistry*; D007700:Kinetics; D008751:Methylene Blue; D016877:Oxidants; D010084:Oxidation-Reduction; D010782:Photolysis; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D016877:Oxidants; D014874:Water Pollutants, Chemical; D006861:Hydrogen Peroxide; D008751:Methylene Blue