Pulsed Electrical Discharges for the Degradation of Organic Compounds in Wate

Advanced oxidation processes (AOPs) are based on the formation of hydroxyl radicals (OH•) and have been explored to overcome the inability of conventional water treatment methods for removing a wide variety of organic contaminants. However, their operation results in relatively high cost and energy requirements as well as chemical addition. Moreover, the effectiveness of these processes can be limited depending on the type of OH• precursor, catalyst and solution turbidity. Therefore, there is a need for developing more efficient, less expensive and environmentally friendly technologies for the degradation of organic pollutants. Less work has been conducted on an innovative electrical discharge technology that transforms liquid water into highly reactive plasma state with plasma generated reactive species. The main objective of this study is to apply electrical discharge plasma to degrade a more diverse set of organic compounds and investigate the chemical processes during plasma treatment.;The influence of key design elements and essential process conditions on reactor treatment capability was evaluated first. Several plasma reactors were designed by changing the electrode configuration and discharge phase (gas vs. liquid). An efficient plasma reactor was optimized based on the effectiveness in the removal of target organic contaminants. Treatment of organic compounds with different initial concentration showed lower degradation rate constant at higher initial concentration suggesting there may be a competition between parent compound and byproducts for reactive species. It was also found that in the presence of other compounds, the individual compound rate constant was impacted. The influence of treating compounds in a mixture was thus studied. When using a carbon steel electrode in the plasma reactor, iron was released into solution which initiated Fenton's reactions accompanied with plasma treatment and improved contaminant degradation. Identification of byproducts when bisphenol A (BPA) was degraded using plasma/Fenton treatment was utilized to confirm plasma reaction pathways and mechanisms. Conventional water treatment processes and commonly used AOPs are not effective for the removal of perfluoroalkyl acids (PFAAs). However, plasma generated at a gas-liquid interface can decompose PFAAs due to their high surface concentration at the interface. Results revealed that aqueous electrons, high energy free electrons and argon ions may play significant roles in initiating reactions with the fluorocarbon tail of PFAAs. A wide range of different compounds had different degradation rate constants in plasma reactors. A model was constructed to predict the approximate treatability of any compound based on two of compound's physicochemical properties.