Refractory Organic Solute Decomposition in Water using Microwave Plasma

Abstract

Microwave excited plasma source with slot antenna in water is a novel plasma applicable to materials processing in liquid. In order to apply this microwave plasma source to a practical use for solute decomposition, it is necessary to evaluate the decomposition efficiency for refractory organic solutes and understand the decomposition process of solution as well. In this paper, the microwave plasma treatment was demonstrated through decomposition of refractory organic solutes such as acetic acid, polyvinyl alcohol (PVA), and 4-chloro-2-methylphenoxy acetic acid (MCPA) in aqueous solutions. Total organic carbon concentration and high-performance liquid chromatography measurements revealed that the refractory organic substances such as acetic acid, PVA, and MCPA were decomposed by microwave plasma. Intermediate products of MCPA were investigated by gas chromatography coupled to a mass spectrometry and ion chromatograph during MCPA degradation using microwave excited plasma.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometric analysis of degradation products after treatment of methylene blue aqueous solution with three-dimensionally integrated microsolution plasma

“…In a plasma of water vapor (or with inert gases), possible primary oxidation agents that may be fed into aqueous solution are OH and O radicals produced through the dissociation of H 2 O. 10,26,[33][34][35][36][37][38][39][40][41] In 3D IMSP, we have observed a strong optical emission of OH (A 2 Σ + → X 2 Π) at 309 nm. The emission intensity of O (3p 5 P → 3s 5 S 0 ) at 777 nm was negligible compared with that of OH.…”

Time-resolved optical emission spectroscopy on three-dimensionally integrated micro-solution plasma

“…We have focused on the behavior of OH(A) because it is believed to be the important reactant in water purification processes. [23][24][25]32,35,46,47) Figure 4 shows time-resolved OES spectra in the range of 300-325 nm, which correspond to the OH(A) emission band and are acquired after triggering the pulse voltage of the power source. The variation in their intensity as a function of time delay shows rather strange behavior.…”

“…[1][2][3][4][5][6][7][8][9] Various types of plasma are used for these purposes, which include pulsed streamer discharge in water, [9][10][11] dielectric barrier discharge, [12][13][14] atmospheric direct-current (DC), low-frequency, and RF glow discharge, 15,16) low-pressure DC glow discharge, [17][18][19][20] RF (13.56 MHz) discharge, 21) arc discharge, 22) and microwave discharge. [23][24][25] In their previous works, Takai and coworkers of Nagoya University have successfully obtained glow discharge in an aqueous solution, which has been named "solution plasma (SP)", and applied this to nanoparticle synthesis and the modification of the surface of nanomaterials. [26][27][28][29] The original SP, however, is ignited in a small bubble generated by Joule heating of the aqueous solution between two stylus electrodes.…”

Review of plasma-based water treatment technologies for the decomposition of persistent organic compounds

“…24) In addition to •OH, other reactive species, such as O 3, and energetic species, such as electrons and ions, contribute to the decomposition of various organic compounds. Several types of plasma reactors have been proposed, including pulsed corona discharge in water, 25) DC or pulsed corona discharge over water, [26][27][28] pulsed discharge over water, [29][30][31][32] DC or pulsed discharge in bubbles, [33][34][35][36][37] dielectric-barrier discharge (DBD) in a gas-liquid two-phase flow, 19,38) microwave plasma in water, 39) DBD in a mist flow, 40) DBD with a falling water film, 41,42) and pulsed plasma with droplets. 43,44) Because these plasma methods can operate without the addition of chemicals, they have significant advantages over AOPs that use chemicals for the treatment of wastewater at offshore plants and environmental water in remote areas.…”