Jin-Oh Jo

Degradation of Organic Contaminant by Using Dielectric Barrier Discharge Reactor Immersed in Wastewater

Dielectric barrier discharge (DBD) was applied to the degradation of an organic contaminant in wastewater. When electrical discharge occurs, the DBD reactor produces oxidative species (ozone) and emits ultraviolet light. For the purpose of using both ozone and ultraviolet light for the degradation of the organic contaminant, the DBD reactor was immersed in the wastewater. The DBD reactor for this paper consisted of a quartz cylinder and a coaxial ceramic tube inside of which a steel rod was placed. High voltage was connected to the steel rod inside of the ceramic tube, and the wastewater was grounded. In this case, the wastewater acted not only as an electrode but also as the cooling medium for the DBD reactor. The performance of this DBD reactor system was evaluated with a simulated wastewater formed with distilled water and an azo dye (Acid Red 27) as the organic contaminant. The experimental results showed that this system was able to completely degrade the organic contaminant within 20 min at typical experimental condition. The energy requirement for the degradation of the organic contaminant was found to be 0.654 kJ/mg

Plasma–Catalytic Ceramic Membrane Reactor for Volatile Organic Compound Control

Decomposition of a volatile organic compound (ethylene) was carried out using nonthermal plasma created in a multihole porous ceramic membrane. The ceramic membrane employed as a low pressure drop catalyst support was loaded with manganese oxide capable of removing unreacted ozone. AC-driven discharge plasma was created inside the porous ceramic membrane to produce radicals, ozone, ions, and excited molecules available for the decomposition of ethylene. As the voltage applied to the plasma reactor was increased, the electrical discharge plasma gradually developed in the radial direction, and uniform plasma was produced in the entire ceramic membrane. The effects of specific energy input, initial ethylene concentration, and manganese oxide loading on the decomposition efficiency and the formation of byproducts were examined. It was found that the use of the manganese oxide-loaded ceramic membrane efficiently removed unreacted ozone while keeping the ethylene decomposition efficiency as high as the bare ceramic membrane case achieved. In addition, partially oxidized products such as formaldehyde, acetaldehyde, and formic acid greatly decreased by manganese loading.

Gaseous Electrical Discharge-Induced Degradation of Organic Compound in Wastewater: UV Irradiation and Ozonation Effect

Abstract This study investigated the degradation of an organic compound (an azo dye, Acid Red 4) in a synthetic wastewater by using dielectric barrier discharge (DBD) tube comprised of a hollow quartz cylinder and a coaxial copper rod. The DBD tube was immersed in the wastewater that was connected to the ground electrode. When AC high voltage was applied to the copper electrode, the electrical discharge occurred inside the quartz cylinder to produce ultraviolet (UV) light and reactive species such as ozone. The photocatalytic degradation of the organic compound with the UV emitted from the DBD tube was carried out in the presence of aluminum meshes coated with titanium oxide. The system further comprised a gas diffuser that distributed the ozone-containing gas produced in the DBD tube into the wastewater, such that the organic compound were degraded by reacting with ozone. The contributions of the photocatalysis and the ozonation to the degradation were separately assessed, and then combined effect on the degradation was examined. The results clearly revealed that the present system capable of degrading the organic compound in two ways (DBD-induced photocatalysis and ozonation) was very effective for the treatment of the wastewater.

Decomposition of Ethylene using a Hybrid Catalyst-packed Bed Plasma Reactor System

A series of experiments using atmospheric-pressure non-thermal plasma coupled with transition metal catalysts were performed to remove ethylene from agricultural storage facilities. The non-thermal plasma was created by dielectric barrier discharge, which was in direct contact with the catalyst pellets. The transition metals such as Ag and V2O5 were supported on γ-Al2O3. The effect of catalyst type, specific input energy (SIE) and oxygen content on the removal of ethylene was examined to understand the behavior of the hybrid plasma-catalytic reactor system. With the other parameters kept constant, the plasma-catalytic activity for the removal of ethylene was in order of V2O5/γ-Al2O3¤Ag/γ-Al2O3¤γ-Al2O3 from high to low. Interestingly, the rate of plasma-catalytic ozone generation was in order of V2O5/γ-Al2O3¤γ-Al2O3¤Ag/γ-Al2O3, implying that the catalyst activation mechanisms by plasma are different for different catalysts. The results obtained by varying the oxygen content indicated that nitrogen-derived reactive species dominated the removal of ethylene under oxygen-lean condition, while ozone and oxygen atoms were mainly involved in the removal under oxygen-rich condition. When the plasma was coupled with V2O5/γ-Al2O3, nearly complete removal of ethylene was achieved at oxygen contents higher than 5% by volume (inlet ethylene: 250 ppm; gas flow rate: 1.0 L min; SIE: ~355 J L).