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Characterizations of a hollow needle-to-plate discharge
dedicated to the drug residues treatment in water
Hervé RABAT, Yasmine BALOUL, Dunpin HONG and Olivier AUBRY GREMI, UMR7344 CNRS / Université d’Orléans, France
Abstract
High paracetamol conversion rates, up to 99%, using non thermal plasma can be reached in function of the inlet gas : air, 10% air + Ar, 10% O2 + Ar [1]. Plasma reactor used to treat paracetamol
solutions was a needle-to-plate reactor with 12 needles. In function of the High Voltage parameters, various discharge regimes (corona, DBD, spark) can be obtained. The discharge regime plays an
important role on the produced species in the plasma and on the efficiency of the process. To characterize the discharge, an elementary reactor using a single needle was used. The effects of the
High Voltage supply on the morphologies of the discharge and on the produced species. Three waveforms HV were used: sine, square and pulsed (ns) waves.
Conclusions and perspectives
The discharge regime is an important parameter on the produced species and so on the efficiency of the liquids treatment. The discharge morphology and the emitted lights highly depend on the HV wave. For
the next, it will be necessary to measure the drug degradation after treatment by the three types of discharges.
References
[1] Y. Baloul, H. Rabat, D. Hong, S. Chuon, O. Aubry. International Journal of Plasma Environmental Science & Technology:IJ-PEST, Volume 10(2), 2016.
[2] Y. Baloul, O. Aubry, H. Rabat, C. Colas, B. Maunit, D. Hong. Proc. 11th Int. Symp. on High Pressure, Low Temperature Plasma Chemistry (HAKONE XV), Brno (Czech Rep.)
Acknowledgements
The authors thank Région Centre-Val de Loire for their financial support in frame of TREMEMAP project.
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High Voltage
Gas Inlet
Needle
Plasma
Water
UV Glass
Gas Outlet
gas: air (10 sccm)pressure: 1 barwater: 10 cm3
dneedle/water: 5 mm
dielectric: Mylar®
Spark regimeStreamer regime
9.4 kVpp 14 kVpp5.6 kVpp
Corona regime
Discharge regimes = f(Upp) (exposure times = 200 µs)
Effects of the discharge regime has been studied with an elementary reactor
Effects of the HV supplies on the discharge
In Streamer regime
HV power supplies
- frequency = 500 Hz
- voltage = 13.6 kV (peak to peak)
Trek® 30/20A : sine and square waveforms
Power supply Active Power (mW)
sine wave 24 ± 3
square wave 17 ± 3
pulsed wave 83 ± 3
Spark regime oxidizing species production is enhanced
BUT Streamer regime is used for paracetamol treatment because:
- A large area of the liquid surface is in contact with the discharge
- The discharge is more stable
- The lifetime of needles is enhanced in comparison to the spark regime
spark U = 14.0 kVpp
streamer U = 9.4 kVpp
corona U = 5.6 kVpp
Positive parts:
- Branched discharges for AC waves and more intense channels for the pulsed wave.
- Contacts between discharge and liquide during one period are more numerous with AC
waves (6-8) against 2 for the pulsed wave.
- Pulsed HV: Potential and electric field at the needle is higher than for AC waves where
the voltage reaches 6.75 kV at maximum Differences in morphology and intensity of the
discharges are observed.
Positive/Negative parts: variations of morphology
- In negative, the discharges are more diffuse with intense spotlights at the needle tip.
- For the pulsed wave, the spotlights are difficult to observe due to return to zero potential
and then null electric field around the needle.
Spectrometer Acton®
SP2750 / Camera PiMax 4
grating: 600 gr/mm – blazed at 300 nm – resolution: 0.3 nm 500 accumulations
OH bands are very low compared to N2 bands
Positive/negative parts:
- N2 lines in negative part are greater than those in positive part for the sine and square waves. But
it’s the opposite behavior for the pulsed wave with a very low line emission for the negative part as due
to the return to zero potential.
No difference between sine and square waves spectra.
Pulsed HV: lines are the most intense (in positive and negative parts).
OES measurments
Treatment reactor: a 12 needles-to plate reactor
Paracetamol treatment (25 mg/L) by using a square HV (13.6 kVpp), f=500 Hz
Effects of the inlet gas composition on conversion rates and energy yield
The presence of O2 is necessary in the process to remove paracetamol [2].
The energy yield is highly dependent on the experimental condition.
The best energy yield of 12 g/kWh was obtained for a gas mixture of air-Ar.
High conversion rate close to 99% was obtained for a gas mixture of O2-Ar
Morphologies
OH
N2 (
2-1
)
N2 (
1-0
)
N2 (
0-0
)
1
Inte
nsi
ty(a
.u.) 0.8
0
0.2
0.4
0.6
310 320 330330 340
Wavelength (nm)
Inte
nsi
ty(a
.u.) 0.8
0.2
0.4
0.6
310 320 330 340
Wavelength (nm)
1
0
Inte
nsi
ty(a
.u.) 0.8
0.2
0.4
0.6
310 320 330 340
Wavelength (nm)
1
0
negative part
Inte
nsi
ty(a
.u.)
0.2
0.4
0.6
310 320 330 340
Wavelength (nm)
1
300290 3500
positive part
Inte
nsi
ty(a
.u.)
0.2
0.4
0.6
310 320 330 340
Wavelength (nm)
1
300290 3500
Optical Emission Spectrocopy measurments
