Radio Frequency Plasma in Water

Abstract

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000 -4500 K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

A Novel Method for Producing Hydrogen from a Hydrocarbon Liquid Using Microwave In-liquid Plasma

“…The power supplied into the vessel reactor for each experiment was varied from 150 W to 330 W. The microwaves were irradiated through a waveguide in order to prevent loss of energy to the reactor vessel. This method is investigated to accelerate the in-liquid plasma reaction [25][26][27][28]. The chemical reactions of discharge in water are used for purification of polluted water [29][30][31].…”

Optimization and analysis of shape of coaxial electrode for microwave plasma in water

“…7,8 When L b is negative, P I is constant at 70 W as shown in Fig. 4, and the plasma is stable and efficiently generated by low electric power.…”

“…[1][2][3][4] Several applications have already been developed for the use of this plasma as a new reactive space. Utilizing the plasma within a liquid is expected to be effective in the decomposition of environmentally harmful dissolved substances [4][5][6][7][8] or for medical purposes such as sterilization or even a surgical plasma scalpel. 9 New plasma chemistry using liquids as a raw material enables the synthesis of some nanomaterials [10][11][12] and the production of fuel gas.…”

“…7,8 The plasma is generated at the tip of the electrode, which is a metallic rod surrounded by a cylinder made of dielectric substance. The power required for ignition is related to the diameter of the electrode, and it is reported that the ignition power becomes 600 W for an electrode with a diameter of 2.8 mm and 150 W for one of 0.7 mm.…”

“…The power required for ignition is related to the diameter of the electrode, and it is reported that the ignition power becomes 600 W for an electrode with a diameter of 2.8 mm and 150 W for one of 0.7 mm. 7 Maehara et al 8 have reported on the OH spectral line from the plasma and the decomposition of water containing methylene blue. In addition, considerable research has been conducted into plasma generation in pure water using high-voltage pulsed excitation.…”