1. ROS/RNS generation by various discharge plasma
The 62nd JSAP Spring Meeting
March 12, 2015, Shonan Campus, Tokai University
12a-D14-4
ROS/RNS generation by various discharge plasma
Kazuhiro Takahashi*, Kohki Satoh, Hidenori Itoh and Hideki Kawaguchi (Muroran I. T.)
Igor Timoshkin, Martin Given and Scott MacGregor (Univ. of Strathclyde)
Contents
Background & objective
Experimental apparatus & conditions
Results
Conclusions
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2. Background & Objective
Plasma treated water
Plasma treated water is produced by dissolution of some active species in plasma into water.
Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are produced in the plasma treated water.
ROS/RNS play important roles in the fields of medicine[1] and agriculture[2].
To use the plasma treated water effectively and efficiently, it is important to control the ROS/RNS concentration.
Objective
To investigate and control the kinds and quantities of ROS/RNS in plasma treated water.
We used a plasma jet, a corona discharge, a pulsed discharge, and a packed-bed dielectric barrier discharge (PB-DBD) to produce plasma treated water.
We investigated ROS/RNS concentration in the water.
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[1] S. Hamaguchi: J. Plasma Fusion Res., 87, 10 (2011) 963 [2] K. Takaki: HTSJ, 51, 216 (2012) 64

3. Background & objective Experimental apparatus & conditions Results
Conclusions
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4. Experimental apparatus & conditions – plasma jet
Power supply
Ar (10 L/min)
Applied voltage: AC 13 kVp-p
Frequency: 17 kHz
Input power : 4 W
copper tube (f 3 x 2 mm)
aluminium
sheet
10 mm
N2/O2 (0 or 0.1 L/min)
N2/O2 mixture ratio:
100/0, 80/20, 60/40, 40/60, 20/80, 0/100
glass tube
(f 6 x 3 mm)
Photograph
w/o plasma
w/ plasma
deionised water
(200 mL)
65 mm
Autosampler
15 mm
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5. Experimental apparatus & conditions – corona discharge
15 mm
Applied voltage: +15 kV
Discharge current: 0.4 mA
Input power: 6 W
Cluster
(13 x 2)
40 mm
20 mm
aluminium foil
deionised water
(100 mL)
Background Gas
Ar/O2 = 80/20, 60/40, 40/60 %
N2/O2 = 60/40, 40/60 %
flow rate：2.0 L/min
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6. Experimental apparatus & conditions – pulsed discharge
Gap length
(4 mm)
Charged voltage: kV
Pulse repetition rate: 20 pps
25 kV
140 A
in Ar
deionised water
(100 mL)
0.23 J/pulse
in Ar
Ar, O2, N2
Ar/O2 = 80/20, 60/40, 40/60, 20/80 %
N2/O2 = 80/20, 60/40, 40/60, 20/80 %
N2/Ar = 80/20, 60/40, 40/60, 20/80 %
flow rate: 5.0 L/min
Background gas
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7. Experimental apparatus & conditions – PB-DBD
glass ball(f 3.0 mm)
mesh
rod(f 2 mm)
glass tube
(100 mL)
Ar, O2, N2
Ar/O2 = 80/20, 60/40, 40/60, 20/80 %
N2/O2 = 80/20, 60/40, 40/60, 20/80 %
N2/Ar = 80/20, 60/40, 40/60, 20/80 %
flow rate: 2.0 L/min
Background gas
Applied voltage: AC kVp-p
frequency: 12 kHz
Input power : W
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8. Background & objective Experimental apparatus & conditions Results
Conclusions
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9. Comparison of H2O2 concentration
Plasma jet
Corona
3800 mg/Wh
Pulse
w/o N2
PB-DBD
No H2O2 is detected in the case of PB-DBD, but O3 is detected in the off-gas of the PB-DBD.
O3 does not contribute to produce H2O2, though O3 + H2O → H2O2 + O2 is reported.
H2O2 is mainly produced from the reaction;
　H2O + e(fast) → OH + H + e(slow),
　OH + OH → H2O2.
Pulsed discharge without N2 gas can effectively produce H2O2.
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10. Comparison of NO2- concentration
Plasma jet
Corona
Pulse
400 mg/Wh
w/o N2
PB-DBD
No NO2- is produced in the case of PB-DBD.
To produce NO2- is required for generation plasma in the vicinity of water.
NO2- is effectively produced in pulsed discharge with N2 gas.
NO2- production may prohibit H2O2 production.
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11. Comparison of NO3- concentration
Plasma jet
Corona
Pulse
w/o N2
PB-DBD
PB-DBD off-gas sparging can produce only NO3-.
Pulsed discharge with N2 gas and PB-DBD off-gas sparging with N2-O2 mixture can effectively produce NO3-.
NO3- production may also prohibit H2O2 production.
2500 mg/Wh
N2-O2
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12. Conclusions
We generated an Ar plasma jet, a positive DC corona discharge and a positive pulsed discharge above water, sparged PB-DBD off-gas into water, and then investigated ROS/RNS in the water using HPLC.
H2O2 can be produced from the following reaction:
H2O + e(fast) → OH + H + e(slow),　OH + OH → H2O2.
O3 does not contribute to produce H2O2.
Generating plasma in the vicinity of water is necessary to produce H2O2 and NO2- into water.
NOx- production may prohibit H2O2 production.
Pulsed discharge plasma is effective to produce H2O2 (3800 mg/Wh) and NO2- (400 mg/Wh).
PB-DBD off-gas sparging can only and effectively produce NO3- (2500 mg/Wh).
Detailed presentation
　Corona: “Generation of ROS in water by DC corona discharge exposure”, 11p-A28-13 (finished)
　Pulse : “Production of ROS/RNS in water by pulsed discharge exposure”, 13p-P11-3
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13. Thank you for your attention.
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