Effects of reactor configurations on photosonolysis of PCE and TCE

TCE and PCE are two of the most frequently reported volatile organic compounds (VOCs) in groundwater. A photosonolysis process categorized as the Advanced Oxidation Processes (AOPs) has been studied as an innovative groundwater reclamation technology. In this research, the photosonolysis technology was employed for the decomposition of tetrachloroethylene (PCE) and trichloroethylene (TCE). The specific objectives of the study were: (1) to determine if the concurrent irradiation with ultraviolet light (UV) and ultrasound (US) is needed for the enhanced photosonolysis observed by Sato et al. (2001); (2) to determine the effect of compartmentalization of the reactor on photosonolysis of TCE and PCE; (3) to determine the effect of flow schemes (UV → US or US → UV) on photosonolysis of TCE and PCE; (4) to determine the effect of partition materials (stainless steel vs. aluminum) on photosonolysis of TCE and PCE; and (5) to quantify the effect of hydroxyl radical (•OH) on the reactor efficiency.; In this study, a series of experiments were conducted, including the UV, US, and combination of the UV and US (UVUS) using the one-compartment reactor (without a partition) and the three-compartment reactor (with an aluminum partition or stainless-steel partition). Two mathematical models (i.e., an one-compartment CSTR model and a three-compartment CSTR model) were developed and used to determine the reaction rate constants (k) and reactor efficiencies (E) for photolysis, sonolysis, and photosonolysis of PCE and TCE. The experimental variables were: partition (with a partition vs. without a partition), flow scheme (upflow vs. downflow), and partition material (aluminum vs. stainless steel). Iodine experiments were conducted to determine concentrations of hydroxyl radical (•OH) generated by the UV, US, and UVUS under selected experimental conditions.; From the results obtained, the following conclusions were reached: (1) the synergetic effect of the UV and US on the decomposition of PCE and TCE was confirmed in the one-compartment reactor; (2) the synergetic effect of the UV and US was also confirmed based on the •OH concentration generated; (3) the installation of the partition (either aluminum or stainless steel) resulted in small increases of the reactor efficiencies for photosonolysis of PCE and TCE; (4) the synergistic effect on photosonolysis of PCE and TCE was observed in the three-compartment reactor with either aluminum or stainless-steel partition, in the upflow scheme; and (5) the effects of partition material (either aluminum or stainless steel) on photosonolysis of PCE and TCE were very small.