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) ktakahashi@mmm.muroran-it.ac.jp Contents Background & objective Experimental apparatus & conditions Results Conclusions MURORAN INSTITUTE OF TECHNOLOGY

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. MURORAN INSTITUTE OF TECHNOLOGY [1] S. Hamaguchi: J. Plasma Fusion Res., 87, 10 (2011) 963 [2] K. Takaki: HTSJ, 51, 216 (2012) 64

Background & objective Experimental apparatus & conditions Results Conclusions MURORAN INSTITUTE OF TECHNOLOGY

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 MURORAN INSTITUTE OF TECHNOLOGY

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 MURORAN INSTITUTE OF TECHNOLOGY

Experimental apparatus & conditions – pulsed discharge Gap length (4 mm) Charged voltage: 14.14 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 MURORAN INSTITUTE OF TECHNOLOGY

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 8 - 26 kVp-p frequency: 12 kHz Input power : 6 - 15 W MURORAN INSTITUTE OF TECHNOLOGY

Background & objective Experimental apparatus & conditions Results Conclusions MURORAN INSTITUTE OF TECHNOLOGY

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. MURORAN INSTITUTE OF TECHNOLOGY

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. MURORAN INSTITUTE OF TECHNOLOGY

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 MURORAN INSTITUTE OF TECHNOLOGY

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 MURORAN INSTITUTE OF TECHNOLOGY

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