Comparison of discharge characteristics and methylene blue degradation through a direct-current excited plasma jet with air and oxygen used as working gases

Abstract

Through using a direct-current driven plasma jet operated underwater, degradation of methylene blue (MB) is investigated with air and oxygen used as working gases. With a low power voltage, a plasma plume extends from the needle electrode, which is purple in air. It turns pink after it bridges the two electrodes. During the process, oxygen plasma remains white. Discharge operates in a pulsed mode or a continuous one, which depends on the magnitude of power voltage. For the pulsed mode, oxygen discharge has a shorter plume and a higher pulse frequency than air discharge under the same power voltage. For the same current of the continuous mode, both power and gap voltages of oxygen discharge are higher than those of air discharge. Moreover, MB degradation efficiency increases with increasing power voltage or initial concentration of MB solution. Compared with air discharge, oxygen discharge has a higher degradation efficiency with the same power voltage and treatment time. The pulsed oxygen discharge with power voltage of about 6.5 kV has the highest efficiency in degrading MB dye, reaching approximately 85.8% after 10 min treatment. As a comparison, after 10 min treatment in air discharge, the highest degradation efficiency is 63.7%, which appears in the continuous mode at a power voltage of 10.6 kV. Besides, optical spectra from the discharges are also compared for the two types of working gases.

The effect of modulated electric field on characteristic of SDBD‐like plasma jet for surface modification

“…This process is attributed to the increase of functional groups such as OH on the surface, because surface treatment is done in the air. [39,40] The nitrogen molecules, OH, argon, and oxygen atoms spectral lines are observed in Figure 11. Although the increase in the intensity of the hydroxyl spectral lines, which can make our system more hydrophilic, can be caused by the increased cross-section of the plasma jet with the metal substrate surface.…”

Discharge aspects of a snake‐like plasma plume generated by an atmospheric pressure plasma jet with variable argon flow rate

“…[7] Due to its flexibility and low cost, plasma jet has become a promising tool for the applications in biomedicine, [8,9] material synthesis, [10][11][12] surface modification, [13][14][15] light source, [16] and water purification. [17][18][19] Plasma jet is normally fed with inert gas, such as helium, [20][21][22] argon, [23][24][25][26] neon, [27][28][29] and so on. When helium is used, the plasma plume is diffuse, [30] which means that no filament can be found in the plume.…”

Complicated streamer dynamics in petal‐like patterns formed on the substrate downstream of an argon plasma jet

“…[ 1,2 ] Due to these advantages, the plasma jet has great potential for applications spanning from biomedicine, [ 3,4 ] biocatalyst, [ 5 ] nano‐material synthesis, [ 6 ] surface modification, [ 7,8 ] to many other fields. [ 9,10 ]…”

“…[1,2] Due to these advantages, the plasma jet has great potential for applications spanning from biomedicine, [3,4] biocatalyst, [5] nano-material synthesis, [6] surface modification, [7,8] to many other fields. [9,10] Plasma jet fed with inert gas normally operates in a streamer regime, [11] which is not the same as traditional positive streamer discharges, but features as composed of a plasma bullet propagating with a velocity of 10 3 -10 6 m/s. [12] Streamer behaviors determine the distribution of active species, hence play an important role in plasma jet applications.…”