Degradation of Methylene Blue by RF Plasma in Water

Abstract

Radio frequency (RF) plasma in water was used for the degradation of methylene blue. The fraction of decomposition of methylene blue and the intensity of the spectral line from OH radical increased with RF power. RF plasma in water also produced hydrogen peroxide. The density of hydrogen peroxide increased with RF power and exposure time. When pure water (300 mL) is exposed to plasma at 310 W for 15 min, density of hydrogen peroxide reaches to 120 mg/L. Methylene blue after exposed to plasma degraded gradually for three weeks. This degradation may be due to chemical processes via hydrogen peroxide and tungsten. The comparison between the experimental and calculated spectral lines of OH radical (A-X) shows that the temperature of the radical is around 3,500 K. Electron density is evaluated to be^3.5 9 10 20 m -3 from the stark broadening of the H b line.

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.…”

Excitation temperature of a solution plasma during nanoparticle synthesis

“…[6][7][8][9] To establish the technologies for plasma in liquid, plasma diagnosis has become much more important. Many methods for plasma diagnosis, such as electrical measurement, optical emission spectroscopy (OES) containing the broadening of a spectral line, Langmuir probes, and laser irradiation have been proposed in a past.…”