Hybrid Gas−Liquid Electrical Discharge Reactors for Organic Compound Degradation

A gas−liquid hybrid pulsed corona discharge reactor that utilizes high voltage needle-point electrodes submerged in the aqueous phase coupled with planar ground electrode suspended in the gas phase above the water surface has been developed and analyzed for the removal of low concentrations of phenol. Two types of ground electrodes were evaluated. One type consisted of a solid disk made of stainless steel, and the second type consisted of a disk made of high porosity reticulated vitreous carbon (RVC). The liquid-phase discharge leads to the formation of hydrogen peroxide and hydroxyl radicals, and the gas-phase discharge leads to the formation of ozone. The reticulated carbon electrode produced a higher number and more uniform distribution of plasma channels in the gas phase above the liquid surface. This case also led to the largest amount of ozone dissolved in the liquid phase. The combined action of the reactive species formed in the gas and the liquid phases on the degradation of phenol, the formation of primary byproducts, and the removal of total organic carbon was evaluated for a variety of system conditions, including the addition of ferrous sulfate (for Fenton's reactions), activated carbon (for adsorption and reaction), and various electrode gap spacing. A mathematical model, including sensitivity analysis, has been developed to illustrate the major reaction pathways.