Degradation of model reactants as a chemical probe for cavitation induced hot spots in water treatment devices

Daniel Vallant

Research output: ThesisMaster's Thesis

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Abstract

Cavitation is the formation, growth and implosion of vapor bubbles in a liquid medium (Capocelli et al. 2014, S. 2566) causing localized high temperature (1000 - 10000 K) and pressure (100 - 500 bar) for a few nanoseconds (Kenneth S. Suslick 1990). A number of studies show that these so called “hot spots” lead to the generation of free radicals like( OH) ̇ and H ̇. They are produced through the homolytic dissociation of water and used to oxidize complex contaminants in waste water streams (Advanced Oxidation Process (AOP)). This is the point where in this thesis the term cavitation is strictly differentiated from the damaging event of cavitation. Two different kinds of cavitation are considered: The first, hydrodynamic cavitation (HC) is performed with the patented cavitation unit from Arisdyne systems Inc., which is implemented into a closed loop. The second is ultrasonic cavitation (UC) which is realized through an ultrasonic horn. To investigate the degradation and the existence of cavitation induced hot spots, three different model reactants are used for the experiments: The liberation of iodine (Weissler reaction), the oxidation of sulfite to sulfate and the metabolization of PNP (p-nitrophenol). Samples are prepared for photometric measurement (UV/VIS spectrometer) and the performance of the HC loop is compared with the UC setup. The HC is studied over the pressure range 1000 - 15000 psi and the results of all three model reactants demonstrate that an applied pressure of 1000 psi shows the biggest degradation effect. All HC results are compared with the UC under the same operating parameters like temperature and pH. On the one hand the findings of this study indicate the existence of cavitation induced hot spots through HC and on the other hand it provides a possibility to monitor them quantitatively. Future investigation will be about the scale-up of the used HC system and if it is suitable for different applications like the cracking of long-chained hydrocarbons in the oil industry or the removal of persistent contaminants in waste water streams.
Translated title of the contributionChemischer Nachweis für durch Kavitation erzeugte Hot Spots in Wasserbehandlungsanlagen durch den Abbau von Modellreaktanten
Original languageEnglish
QualificationDipl.-Ing.
Supervisors/Advisors
  • Weiß, Christian, Supervisor (internal)
Award date18 Mar 2016
Publication statusPublished - 2016

Bibliographical note

embargoed until 09-03-2021

Keywords

  • Cavitation
  • Hydrodynamic cavitation
  • Ultrasonic cavitation
  • model reactants
  • model reactions
  • cavitation induced hot spots
  • waste water treatment
  • Advanced Oxidation Process
  • AOP
  • liberation of iodine
  • sulfite oxidation
  • degradation of PNP

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