Anto Tri Sugiarto

Oxidative decoloration of dyes by pulsed discharge plasma in water

Abstract Degradation of organic dyes by the pulsed discharge plasma between needle-to-plane electrodes in contaminated water has been investigated in three discharge modes: (i) streamer, (ii) spark, (iii) spark–streamer mixed mode. The process of the decoloration has been found to be most effective if the discharge operates in the spark–streamer mixed mode in dye solutions. The decoloration rate during the pulsed discharge plasma treatment was dependent on the initial pH values. The decoloration rate was increased when more acidic condition was used, especially in the case of streamer discharge mode. The decoloration rate at the pH value of 3.5 was found to be approximately three times higher than that at a pH value of 10.3. A small effect of initial pH during the decoloration process by spark and spark–streamer discharge mode means that the physical effects, such as shock-wave and ultraviolet radiation, may play an important role in the oxidation process. It was found that the decoloration rates in the case of spark and spark–streamer mixed discharge modes, which are characterized by high intensity ultraviolet radiation, were found to be much higher than that in the case of streamer discharge that is characterized by low intensity ultraviolet radiation. In addition, the considerable increase in the decoloration efficiency of H 2 O 2 containing solutions can be attributed to the increase in hydroxyl radicals’ concentration. These are produced by ultraviolet light photo-dissociation of H 2 O 2 molecules in water surrounding the plasma channel.

Pulsed plasma processing of organic compounds in aqueous solution

Non-thermal plasma processing using a pulsed electrical discharge has been investigated as an alternative method for the degradation of organic compounds contained in water. The active species produced by the electrical discharge may play an important role in degrading organic compounds in water. Three types of electrical discharge formed by the needle-plate electrode system were used in this investigation. The degradation of phenol by electrical discharge with the effects of the addition of gas bubbling and chemicals on degradation efficiency was investigated. The results showed that the degradation rate of phenol was affected by electrical discharge types and oxygen gas bubbling. The addition of a small amount of hydrogen peroxide greatly increased the degradation rate of phenol, in which the ultraviolet light from discharge plasma was considered to be a cause of effective degradation.

Advanced oxidation processes using pulsed streamer corona discharge in water

Degradation of complex organic dyes by pulsed streamer corona discharge in water has been investigated using a ring-to-cylinder electrode geometry system. The obtained result shows that the efficiency of the decoloration depended on the initial pH of solution and the decoloration rate was higher at lower initial pH value. In the case of hydrogen peroxide addition, the decoloration rate increased due to the reactions of dye with hydroxyl radicals formed by photo-dissociation of hydrogen peroxide in the plasma discharge channels. However, the reactor with two rings was more effective than that of one ring for the decoloration due to a larger volume occupied by the streamer plasma channels in water.

Aqueous Phenol Decomposition by Pulsed Discharges on the Water Surface

Decomposition of environmental contaminants such as phenol contained in water was investigated using a pulsed high-voltage gas-phase discharge on the water surface (water surface plasma). The discharge consists of streamer channels that spread out over the water surface. Discharge characteristics were dependent upon the distance between the needle-tip electrode and the water surface, the shape of the submerged ground electrode, and the composition of the gas enveloping the electrode. When the electrode-water distance was decreased, the discharge mode changed from corona to streamer, and then, finally, to a water surface discharge when the distance was small. Argon gas was the most effective enveloping gas for decomposing phenol in water (compared to oxygen or air). When the gas flow rate was increased to carry away the active species formed in the gas phase; the decomposition rate did not change in argon, but decreased in oxygen. The shape of the submerged ground electrode influenced the discharge state and the phenol decomposition rate. A ring-shaped ground electrode was more effective for decomposition of phenol than straight or semicircular shapes. Experiments were performed to identify the mechanism(s) responsible for the decomposition of organic materials in water.

High efficiency sterilizer by high voltage pulse using concentrated field electrode system

The serilization method of microoganisms in liquid food using pulsed electric field has been reported by some researchers. Considering application to the food industry, energy efficiency of the method becomes important. The authors developed a new electrode system for concentrating the electric field in liquid food medium. The new electrode configuration made it possible to raise the energy efficiency for the pulsed sterilization process than that for conventional parallel plane or concentric cylinder electrode systems.

Decoloration of Organic Dye in Water by Pulsed Discharge Plasma Generated Simultaneously in Gas and Liquid Media

Abstract A new process for decomposing organic contaminants in water was proposed. Pulsed discharge plasma was generated in the gas phase, and the produced plasma was permeated through a pinhole into the water phase. Water (upper) and gas (lower) were separated by an insulating plate, where a pinhole was perforated at the center of the plate. Gas was bubbled into the water phase through the pinhole. In the gas phase, the high voltage pulse was applied between the needle electrode and the ground electrode (immersed in the water phase). The high voltage pulsed discharge plasma was generated in the gas phase, simultaneously the plasma channel was permeated into the water phase accompanying by the gas bubbles. The water phase plasma produced a lot of active species, UV light, and high-energy electrons. Porous ceramic tube was tried to use for producing water phase plasma, instead of the insulating plate in a pinhole reactor. It was observed that the gas phase plasma also permeated through many small pores into the water and generated streamer discharge in water. Chicago sky blue aqueous solution was effectively decolored with oxygen gas bubbling than the cases of argon gas and air. With applying pulsed voltage of 20 kV and pulse frequency of 25 Hz with 500 mL/min oxygen bubbling, the dye aqueous solution with 10 ppm initial concentration was decolored about 95% in 10 min treatment. The decoloration rate increased with increasing electrical conductivity of the solution. This type of simultaneous discharge plasma reactor is expected to have high-energy efficiency degradation rate.

Aqueous phenol decomposition by pulsed discharge on water surface

Decomposition of environmental contaminants such as phenol containing in water was investigated using a pulsed high voltage gas phase discharge on the water surface. Discharge characteristics varied with varying electrode distance between needle tip and water surface, and composition of the surrounding gas. When the electrode distance was decreased, the discharge modes changed from corona to streamer, and then spark discharge in the case of very close to the water surface. The streamer discharge channels spread over the water surface. Argon gas was most effective to decompose phenol in water than the case using oxygen or air for the surrounding gas.

Characteristics of Ring-to-Cylinder Type Electrode System on Pulsed Discharge in Water

Abstract The pulsed streamer corona discharge in water has been investigated for oxidation of organic contaminants in water solution. The reactor with ring-to-cylinder electrode system has been designed and tested in this investigation. It was found that the insulation method of the ring electrode was the most important factor to lower streamer initiation voltage. A large volume of streamer corona discharge was generated around the ring electrode and the streamer corona discharge formations are greatly dependent on the electrode geometry, polarity and the water conductivity. The degradation of phenol was also tested by this electrode system. It was found that the degradation rate of phenol was higher for the positive pulse than that of negative pulse, and the intermediate products were removed when the treatment time increased.