Water Purification by Using Microplasma Discharge
Naoto Masamura, Marius Blajan and Kazuo Shimizu
Organization for Innovation and Social Collaboration, Shizuoka University,Jyouhoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp

Table.1 Experimental parameters.

Introduction
In recent years, associated with industrial
development, water pollution became
aserious problem. Plasma could be used aswater treatment technology such as
decomposition of organic compound andsterilization of bacteria.
Conventional
technologies
requiresexpensive processes or the usage ofchemicals for water treatment. Microplasmais an ecological and economical technology
to be applied for water treatment due tothe low cost and low discharge voltage.

Methods
Microplasma Electrode and Mechanism
GASPower supply

ACCarrier gas

Air

Flow rate [L/min. ]10TargetIndigo carmine

Concentration [mg/L]

10Treatment volume [ml]200

A neon transformer was used as the AChigh voltage power supply, Carrier gas wassupplied from the air pump regulated byflow meter. It flows above the reactor andpass through the holes of electrodes.
Indigo carmine was used as the target tobe decomposed. The treated sample wasanalyzed by UV-VIS, ozone monitor andESR(Electron Spin Resonance).

(3)Decomposition rate of indigo
carmineFig. 7 Ozone concentration in gas phase.
The decomposition rate was higher than
40% at discharge voltages 1.0-1.3 kV.

(4)ozone concentration

Results(1) Color of indigo carmine solution

OH*O*20 min.
Beforetreatment treatment

O3Fig. 1Mechanism of water treatment bymicroplasma.
Microplasma electrodes are perforated
metallic plates covered with a dielectric
layer and faced together with a spacer of
100 μm as shown in Fig. 1.
Microplasma electrodes were placed at small
distance above the water thus gas is flown
towards the water surface to react withthe target to be decomposed. Various active
species such as ozone, OH radical etc. weregenerated by microplasma[1].

Fig. 4 Indigo carmine solution samples
taken during microplasma treatment
process(Vd=1.0 kV).
The
treatedsamplelooks
almosttransparent compared with non treatedsample. Thus, indigo carmine solution wasdecomposed by microplasma treatment.

Fig. 8 Ozone concentration versus
discharge voltage measured in gas phaseand liquid phase by microplasma.
The ozone concentration increased withthe increase of the discharge voltage. 0.52.2% of the total ozone generated in gas
phase was dissolved in water.

(5)ESR analysis(2) Observation of indigo carmine
absorbanceFig. 9 OH signal detected by an ESR
measurement

Fig. 2 The emission during discharge(Vd=1 kV).

Microplasma is a typical dielectric barrierdischarge. The image of microplasma
discharge is shown in Fig. 2.

Experimental Setup

Fig. 5 The analysis of absorbance using
spectrum photometer(Vd=1.0 kV).
The decrease of 610 nm and 300 nm
peaks suggest that organic compounds
contained in indigo carmine solution wasdecomposed during microplasma treatment.

Current

HV

Flow meterAir pump

HV probe

UV-VISElectrodes

Fig. 6 Chemical reaction of indigo carmine
by microplasma treatment.
ESR
mg/L

Indigo carminesolutionppm

Water pump

Conclusions

Microplasma could be used as an ecologicalandeconomicaltechnology.
Watertreatment using microplasma was carriedout.
1. Indigo carmine was decomposed after
microplasma
treatment
anddecomposition rate increased with thetreatment time and discharge voltage.

Oscilloscopeprobe

Spin trap agent 5,5-dimethyl-1-pyrroline
N-oxide was used to perform ESR analysis.
Generated OH radical by microplasma wereobserved at 3480, 3490, 3460, 3510
gauss.

Ozone monitor

Fig. 3 An experimental setup.

Indigocarmine
hastheH
type
chromophoric group which gives the bluecolor. Double bond (C=C) was cut thus OH
radicals and ozone presence lead to theformation of a new bond 2(C=O). As aresult, Indigo carmine was decomposed toisatin sulfonic acid.

2. OH radical was one of the causes ofindigo carmine decomposition. It wasdissolved in the water as confirmed byusing ESR.
3. 0.5-2.2% of the ozone generated in gas
phase was dissolved in water.

Reference[1] K. Takahashi, Y. Sasaki, S. Mukaigawa, K.
Takaki, IEEE, Trans. on Plasma Sci. Vol.
38, pp. 2694-2699(2010).