Developing Steam Bubble Cavitation for Pollutant Degradation: Determining Hydroxyl Radical Production Under Selective Conditions

Current wastewater treatment processes in the U.S. are not designed to remove pharmaceuticals and personal care products (PPCPs). Effects of long term, low exposure of PPCPs on humans and ecosystems are largely unknown, resulting in a growing concern over exposure to these pollutants. Advanced oxidation processes (AOPs) using highly reactive hydroxyl radicals (•OH) are promising technologies to remove these contaminants. •OH reacts with inorganic and organic compounds in water to produce less harmful products. The formation and collapse of microbubbles to generate •OH is the advanced oxidation technique known as cavitation. The energy efficiency of current cavitation techniques, such as acoustic and hydrodynamic cavitation, is limiting their use in environmental engineering. A recent study proposed steam cavitation as a considerably more energy efficient cavitation process. Steam cavitation is the method of injecting steam into sub-cooled water to produce cavitation. Because only one study has been conducted on this process, this research project aimed to further investigate the use of steam cavitation to efficiently generate •OH. The objectives of this research were: (1) to design a reactor to successfully create steam cavitation, and (2) to vary temperatures and nozzle diameters in steam cavitation to determine optimum parameters for the greatest •OH generation. After iterative experimentation and calculation, a temperature-constant reactor was constructed to produce steam cavitation. Steam was injected through a nozzle into the pool-water reactor containing terephthalate. Generated •OH from the bubble collapse reacted with terephthalate to form hydroxyterephthalate. Therefore, concentrations of hydroxyterephthalate corresponded to •OH formation. Results indicate that •OH production is dependent on the pool-water temperature and the nozzle diameter. Of the conditions tested, 45°C and a nozzle diameter of 0.61 mm produced the most •OH. Therefore, steam cavitation produces •OH, warranting further study of this process as a novel water treatment technology.College of Engineering Undergraduate Research Scholarship FundNo embarg