Influence of Peroxynitrite in Gliding Arc Discharge Treatment of

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Influence of peroxynitrite in Gliding Arc Discharge treatment of Alizarin Red S and post-discharge effects Djillali Redha merouani, Fatiha Abdelmalek, Mouffok redouane Ghezzar, Ahmed Semmoud, Ahmed Addou, and Jean-Louis Brisset Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie302964a • Publication Date (Web): 24 Dec 2012 Downloaded from http://pubs.acs.org on January 9, 2013

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Industrial & Engineering Chemistry Research

Influence of peroxynitrite in Gliding Arc Discharge treatment of Alizarin Red S and post-discharge effects

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1

1

1

2

1

D.R. Merouani , F. Abdelmalek , M.R Ghezzar , A. Semmoud , A. Addou , J.L Brisset 1

3

Laboratoire des Sciences et Techniques de l’Environnement et de la Valorisation (STEVA), Faculté des sciences et de la technologie, Université de Mostaganem, 27000, Mostaganem, Algérie 2 Laboratoire de Spectrochimie Infrarouge et Raman (LASIR), Université des Sciences et Technologies de Lille, 59650 Villeneuve d’Ascq, France 3 Faculté des Sciences, Université de Rouen, Mont-Saint-Aignan, France

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Corresponding author: F. Abdelmalek : [email protected]

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Address: BP 188, university of Mostaganem, Algeria

ACS Paragon Plus Environment


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Abstract

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The gliding arc discharge is a cheap and efficient non-thermal plasma technique able

21

to degrade organic compounds dispersed in water at atmospheric pressure. Alizarin Red

22

Sulfonate (ARS) is selected as a stable quinonic dye. Exposure of the dye solution to the

23

discharge in a batch reactor induces two successive reaction steps according to the

24

treatment conditions. Direct exposure of the solution to the discharge induces simultaneous

25

bleaching and COD evolution. In post-discharge conditions, i.e., after the discharge is

26

switched off, the reactions keep on developing. This study thus underlines two key features,

27

i.e., the ability of glidarc discharges to degrade recalcitrant molecules and the low cost of the

28

process which requires short exposure times. A model mechanism involves peroxynitrite as a

29

likely active species formed in the discharge and involved in post-discharge phenomena in

30

aqueous solutions and suggests short exposure times and much longer post-discharge times

31

for optimized pollutant abatement.

32 33

Key words:

Non-thermal plasma; gliding arc discharge; peroxynitrite; Alizarin Red S;

34

Temporal Post-Discharge Reactions.

35


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36 37

I- Introduction

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Aqueous effluents from textile industries carry away numerous molecules belonging

39

to various families of dyes (e.g., azo, quinonic,…) which may be difficult and expensive to

40

degrade.1 Anthraquinonic dyes are involved in polyamide, leather and wool dyeing

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therefore the most important ones after azo dyes for commercial reasons. They are classified

42

as recalcitrant compounds which remain in aquatic ecosystems,4,5 and their degradation is

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considered in several papers.6-8 Alizarin Red Sulphonate (ARS) is an anthracene-like

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synthetic dye. It has three ring aromatic structure in the central part of it molecule

45

plus various substituents.9 It is widely used in textile industry and for histochemical

46

analyses 10,11 so that new techniques have to be proposed for its degradation.

47

The usual techniques

48

adsorption and biodegradation, activated carbon, reverse osmosis, ultrafiltration, etc, are not

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well adapted to this family of dyes, because of the high number of benzene ring which

50

stabilize the molecule.13,14 More efficient and less energy consuming processes must be

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settled to eliminate these pollutants or lower their harmful character. Newly developed

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Advanced Oxidation Processes (AOP) generate active hydroxyl radicals •OH which are

53

claimed to degrade numerous organic compounds.15-17 Some non-thermal plasma

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techniques, such as corona,18,19 dielectric barrier discharge (DBD) 20 or gliding arc discharges

55

(GAD) belong to these AOPs: they burn at atmospheric pressure in conditions half way from

56

thermal and non-thermal plasmas, since electrons and heavy particles are not fully

57

thermalized as they are in thermal plasmas. Thus the macroscopic temperature remains

58

close to room. The GAD is actually “quenched” plasma with a composition close to a thermal

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plasma and therefore a thermal effect of only few degrees. Compared with other plasma

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techniques, the GAD is considered as a promising technique well adapted to the pollutant

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abatement of aqueous effluents and several examples relevant to the elimination of bio-

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recalcitrant organic compounds found in domestic and industrial wastewaters illustrate this

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assertion:

12

2,3

and

for treating liquid wastewaters, e.g., coagulation/ flocculation,

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(i) Degradation of various dyes, e.g., azo dyes: Orange II, yellow supranol 4 GL, Red

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Nylosane F3 GL, Eryochrome Black T , Orange G, Methylorange* ; triphenylmethane

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dyes: Malachite green, Crystal violet, Bromothymol Blue **; anthraquinonic dyes: Acid

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green 25, ARS;5, 21-26

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(ii) Degradation of polymers rejected by industry,27 degradation of two polluted textile

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wastewaters 28 eliminating organic waste solutes,29 destruction of nicotine;30

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(iii) Mineralization of the tributylphosphate present in the nuclear industry rejects;31

71

Trilaurylamine for nuclear industry processes

32

degradation of phenol,33 Bisphenol A in



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solution.34

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The gliding arc discharge involves higher quantities of energy than other cold discharges at

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atmospheric pressure and thus presents several advantages: for example, it generates a

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larger population of active species, without need of incorporated reagent and mainly favors

76

the occurrence of post-discharge phenomena (i.e., a self-development of the chemical

77

reactions in the solution after the discharge is switched off) which are of significant interest

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for industrial applications by lowering the running cost of the process.

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The GAD treatment of aqueous solutions consists in exposing the target solution to the

80

discharge burning in air over the liquid in a batch or a circulating reactor. The discharge

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generates active oxidizing species, some of them are long life water soluble moieties and are

82

responsible for Temporal Post-Discharge Reactions (TPDR) which develop in the liquid

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phase.35

84

Several examples of TPDR are reported in the literature, e.g:

85

(i) The gliding arc oxidation of ferrous to ferric ions develops in two steps. The first step

86

is rapid, associated with the exposure time to the discharge and would be attributed

87

to

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dissolved species;36

89

•

OH at the liquid surface; the second step is a slow TPDR, due to H 2 O 2 and other

(ii) TPDR was also evidenced for nucleophilic substitutions by corona discharges treatment in CO ;37

90 91

(iii) Bacterial inactivation in post-discharge conditions.38 The authors underline the

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economical advantage of the plasmachemical bacterial inactivation without extra

93

energy or reagent input;

94

(iv) Moussa et al.

35

evidenced TPDR in the plasmachemical treatment of methyl orange

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and attribute the degradation to the species H 2 O 2 and HNO 2 formed in the

96

discharge;

97

(v)

Brisset et al

39

− considered the influence of peroxynitrite ONOO and its matching

98

acid which are soluble in water, able to dissociate into • OH and ONO− and to induce

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oxidizing, nitrating and nitrosing post-discharge effects on solutes;

100

(vi) The GAD treatment of surface waters

40

induced an increase in the BOD abatement

101

after switching off the discharge, and this feature was attributed to the oxidizing

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power of peroxynitrous acid ONOOH . The formation of transient nitrite ions was

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evidenced which is the source of peroxynitrite ONOO− , i.e., a transient precursor to

104

nitrate, 41 according to the following sequence:

105 106

N 2 → NO-2 → ONOO- → [NO3- + H + ]

(1)

The GAD (or glidarc) was first proposed by Lesueur et al.


42

and developed by

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Czernichowski 43 for the decontamination of gases. The technique is based on the production

108

of quenched non-thermal plasma generated by an electrical arc often burning in air. The

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efficacy of the treatment results from the presence in the plasma cloud of active chemical

110

species, radicals, excited molecules and ions, such as

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H 2 O 2 , O 3 , O +2 , N +2 , O + , N + , etc. The most reactive species are the hydroxyl radicals •OH

112

due to their high standard oxidation potential E°(•OH/H2O) = 2.8 V/SHE which is among the

113

strongest known oxidizing potentials. Emission spectra analysis •

•

OH ,

•

NO , O • , O 2 , HO •2 , H • ,

44

of the gliding arc

•

114

discharge in humid air shows the occurrence of OH and NO, and allows quantifying the

115

population of the formed species. •OH results from the dissociation of water molecules by

116

electron (or/and photon) impact, while the endothermal formation of •NO (according to the

117

Birkeland process) requires the occurrence of an electric arc. The main relevant reactions

118

are given below (reactions 2-7):

119

H 2O + e (or hν) → H • + • OH + e

(2)

120

2H 2 O + e → H 2 O 2 + H 2 + e

(3)

O 2 + e (+M) → 2 O • + e (+M)

(4)

121 122

N 2 + O • → • NO + N •

(5)

123

N • + O • → • NO

(6)

124

N • ( 2 D) + O 2 → • NO + O•

(7)

125

Hydroxyl radical and nitric oxide are the precursors of derivatives that react at the liquid

126

surface and/or in the solution provided they are soluble.

127

This work is devoted to the systematic investigation of the behavior of an anthraquinonic dye

128

(ARS) under discharge and, for the first time, post-discharge conditions. Peroxynitrite

129

(ONOO-), i.e., oxoperoxonitrate(-1) according to the official quoting, is a derivative of NO and

130

NO2 formed at the liquid surface, soluble in water, and the precursor of isomer forming

131

reaction yielding nitric acid. This active specie formed in the discharge is involved in post-

132

discharge phenomena in aqueous solutions.

133

The matching acid ONOOH is weak (pKa= 6.8) but granted with strong oxidizing properties

134

(Eº(ONO2H/NO2)) = 2.02 V/SHE. The acid -base system is involved in discharge and post-

135

discharge reactions.35, 45

136

2. Materials and methods

137

2.1. Reagents and plasma-reactor



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Alizarine Red Sulphonate, ARS (C14H7NaO7S, also referred to as 1,2- dihydroxy-

139

9,10- anthraquinonesulfonic acid sodium salt or Mordant Red 3; C.I. 58005; molecular

140

weight: 342.28g ) is a commercial dye (Analytical grade) purchased from Acro Organics.

141

Distilled water was used to prepare dye solutions of suitable concentration. ARS is a triacid

142

of H3I type: the first acidity is strong; the two others are medium or weak pKa (H2I-/HI2-) = 5.5

143

and pKa(HI2- / I3-) = 10.8. The relevant colours are colorless (H3I), yellow (H2I-), red (HI2-) and

144

purple (I3-). Natural ASR solutions absorb at 430 nm and their pH is 6.5.

145

The experimental apparatus of the GAD used is shown in Fig.1. Compressed gas is led

146

through a bubbling water flask to get water-saturated. The gas flow then passes between two

147

semi elliptic electrodes connected to a 220 V/9 kV high voltage Aupem Sefli transformer. It

148

produces an alternative potential difference of 9000 V and a current intensity of 100 mA in

149

open (and 600V/160 mA in working) conditions. The delivered power is close to 100 W,

150

which considerably lowers the running cost of the process.

151

An electrical arc forms between two diverging electrodes raised to a convenient voltage

152

difference at the minimum gap. The arc is pushed away from the ignition point by the feeding

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gas flow and sweeps along the electrodes to the maximum electrode gap where it breaks

154

into a large plasma plume. A new arc then appears and develops according to the same

155

procedure. The length of the electric channel increases so that the plasma temperature falls

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before breaking. The resulting plasma is actually quenched plasma at atmospheric pressure

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and quasi-ambient temperature. The diffusion process in the liquid is improved by conversion

158

in the liquid phase due to the airflow and magnetic stirring.

159

The treatment is performed in batch mode with the working parameters: the gas flow is fixed

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at Q = 700 L h-1, the electrode gap e = 2 mm, the nozzle diameter 1mm and the distance

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between the electrodes and the liquid surface d = 3 cm. The solution temperature is

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thermostated at 20 ± 2°C by circulating water in a jacket.

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2.2. Plasma treatments of ARS samples

164

2.2.1. Direct exposure of ARS solutions to the discharge

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ARS aqueous samples (100 and 335 µM) were poured in the 500 mL pyrex vessel. The

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evolution of the treatment of the dye solution under plasma treatment in batch mode was

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followed for various exposure times t* (0, 10, 20, 30, 60 min) and analyzed immediately after

168

sampling (“snapshot analys”).

169

2.2.2. Post-discharge experiments

170

The sample solutions were exposed to the discharge in the same conditions as for direct

171

exposure experiments, i.e., for t* =1, 2, 5, 10, 15, 30 and 60 min before being abandoned

172

outside the reactor for various post-discharge times tTPDR before the analyses were

173

performed. Preliminary set of experiments was performed on 100 µM ARS solutions and

174

involved tTPDR = 0.25, 0.5,1, 2, 3, 4, 5, 6 and 24 h post-discharge delays. The second set of


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175

experiments concerned 335 µM ARS solutions and longer post-discharge times: tTPDR = 1, 2,

176

3, 5, 10, 24, 48 h, 5, 7 and 30 days.

177

Analyses were performed by measuring absorbance A at 430 nm (with Optizen UV-vis

178

spectrophotometer) and COD by the potassium dichromate standard method.46 COD and

179

bleaching rates were calculated as follows:

180

Degradation (%) =

181

Where COD0 and CODi refer to the COD values before and after treatment, respectively, and

182

Bleaching (%) =

183

Where A is the absorbance value at the absorbance peak in the visible wavelength range; A0

184

and Ai are the absorbance values before and after treatment, respectively.

185

3- Results and Discussion

186

3.1- Preliminary treatment: direct exposure of ARS to the glidarc

187

3.1.1. Diffusion of active species in the solution: effects of pH and conductivity

188

Exposing ARS (100 µM) solutions to the discharge in humid air induces increases in acidity

189

and matching conductivity. pH falls from 6.5 to 3.5 within 1min and trends to 1.55 for 1h

190

exposure time while conductivity increases from 20 µS cm-1 to 5290 µS cm-1 for t* = 1h.

191

Analyses of distilled water exposed to the discharge in the same conditions evidenced the

192

formation of nitrite and nitrate up to 202 and 607 mg L-1 respectively.

193

Humid air plasma treatment of solutions involves that formed active species are water

194

soluble enough to enter the solution and get dissolved. In particular, H3O+, NO2- et NO3–

195

which are involved in the pH lowering process via the formation of nitrous and nitric acids

196

(reactions 12-14).47 A reaction scheme was recently proposed (reactions 8-15).48

(COD0 − CODi ) × 100 COD 0

(A 0 − A i ) × 100 A0

197

NO + • OH → ONOH

(8)

199

NO + O → ONO

(9)

200

ONO + NO + H2O → 2 ONOH

(10)

201

NO• + HO•2 → ONOOH

(11)

202

HNO 2 + H 2O 2 → HNO3 + H 2O

(12)

203

NO2 +• OH → H + + NO3−

(13)

198

•



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204

ONOOH → NO 3- + H +

(14)

205

3 NO -2 + 2H + → NO 3- + 2 NO + H 2O

(15) 49-51

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which consider only protons

206

The charge balance was not observed in most experiments

207

and nitrate ions after direct exposure and must be completed. For example for 1h Post-

208

discharge, pH is measured as 1.55, which means C H + = 10 − pH = 28 .2 mM and the resulting

209

molar conductivity is:

210

λ H + x C H + = 349.8 x 28.2 = 9.86 mS cm

211

i.e., a value higher than the measured conductivity of the solution, 5.23 mS cm, which

212

involves the conductivities of all the identified anions, i.e., nitrite and nitrate, whose molar

213

conductivities are both close to 71.4 mS.

214

3.1.2 Influence of the Reactive Nitrogen Species (RNS) on ARS bleaching

215

This work aims to underline the determining influence of nitrogen containing species (or

216

Reactive Nitrogen Species), such as nitrite ONO-, peroxynitrite ONOO- and nitrate NO3- in the

217

bleaching process of ARS. The structure of peroxynitrite is linear, isomeric of nitrate and a

218

transient intermediate in the oxidation of nitrite to nitrate.35,45

219

Previously published works on ONOO- synthesis gather the reactions involving NO -2 , NO 3

220

and Oxygen donor species, such as O, O3, H2O2... .52 Starting from either NO2 and NO -2 :

-

221

O + NO −2 → ONOO −

(16)

222

O •- + ONO • → ONOO -

(17)

223

ONOOH ↔ ONOO − + H +

(18)

224

O −2 • + • NO → ONOO −

(19)

225 226

or from NO 3 53 -

− e aq + NO 3− → NO •32 −

227

(20)

228 229 230

•

NO •32− + H 2 O → NO 2 + 2OH −

(21)

OH + NO 2 → ONOOH

(22)

231


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ONOOH ↔ H + + ONOO −

232

(23)

233 234

We can incidentally point out that nitrite anions are thermodynamically unstable for pH < 6,

235

due to the disproportionation of NO -2 into NO 3 and NO:

-

3NO -2 + 2H + → NO -3 + 2 NO + H 2 O

236 237

(24)

as considered elsewhere.45

238

A clear evidence of the essential role of the RNS in ARS bleaching process results

239

from treatments of the dye with and without a reducer of the nitrites,54 such as sulphamic acid

240

NH2SO3H according to:

HNO 2 (l) + NH 2SO 3 H(l) → N 2 (g ) + H 2SO 4 (l) + H 2 O(l) (25)

241 242

Which shows that nitrous acid is reduced into nitrogen. Thus incorporating sulphamic acid

243

(SA) to the reactor prevents nitrite and RNS formation, it remains to check the changes

244

induced in solution by the plasma treatment and to compare the results with and without

245

NH2SO3H.

246

We thus achieved two sets of plasma treatments of ARS with and without SA. The relevant

247

results (Table 1) show bleaching rates of 53.4% and 4.7% with and without sulphamic

248

quencher respectively for t* = 45 min exposure. For longer exposures t* (e.g. 1 h or longer),

249

the bleaching rates are not largely different (67.2% and 73% resp.). Such results are

250

apparently conflicting but they can however be simply explained: incorporating an excess of

251

sulphamic acid at the beginning of the treatment allowed to reduce all the nitrites already

252

formed. For long exposure times the incorporated NH2SO3H molecules are no more in

253

excess, due to their action on nitrite ions; or because they have been degraded by the

254

plasma formed oxidizers.

255

Iya-sou et al.55 recently considered the action of long life species such as nitrogen oxides

256

″formed over the solution by a gliding arc discharge in air in the degradation of model

257

pollutants as phenol in direct exposure mode and in post-discharge conditions″. In case of

258

moderately soluble phenol, the authors assume that the main mechanism for removal

259

involves the action of •NO2 radicals formed in the liquid phase from the dissociation of soluble

260

N2O4. Unfortunately no author has detected •NO2 or its dimmer in the gas phase, •NO readily

261

oxidized to •NO2 by numerous Oxygen donor species, as mentioned above. Also, •NO2 easily

262

fixes an electron E'°(•NO2/NO2-) = 0.99 V/SHE at pH: 7 (i.e., in an acidity range where nitrite

263

ion is thermodynamically unstable). It may be incidentally pointed out that nitronium ion NO2+

264

and nitrosonium NO+ are the oxidized forms of •NO2 and •NO respectively : [E° (NO2+/•NO2) =

265

1.6 V/SHE and E°(NO+/•NO) = 1.21 V/SHE] and are probably present in limited

266

concentrations in the discharge cloud.



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267

However, it is likely that among the RNS, peroxynitrite is among the most efficient ones, due

268

to its ability to react both as a strong oxidizer and as a source of nitrating/nitrosing agent. In

269

case of ARS degradation, the influence of RNS is essential.

270

Direct exposure of organic compounds to humid air plasma in batch conditions usually

271

requires long treatments time. In order to save time and energy, the direct exposure time t*

272

was deliberately shortened in the scope of our investigation of TPDR.

273

3.1.3.

274

SA

275

This part of the study is devoted to show evidence of the determining role of the plasma

276

generated RNS in the degradation of the dye with special emphasize on peroxynitrite35,45

277

since the short lifetime of •OH (few hundred ns) discards them from direct occurrence in the

278

bleaching post-discharge process.56

279

A set of sixteen ARS (100 µM) solutions were prepared and exposed to the glidarc in humid

280

air for t* (1, 2, 5, 10, 15, 30, 45) and 60 min with or without incorporated SA. After each

281

exposure, the samples are disposed outside the plasma reactor and abandoned for various

282

tTPDR times in post-discharge conditions before being analyzed for absorbance and COD. The

283

results for standard post-discharge times tTPDR (0.25, 0.5, 1, 2, 3, 4, 5, 6 and 24h) are

284

gathered in Table 2.

285

Direct exposures to the discharge of samples without SA (e.g., for t* = 1 and 15 min) induce

286

bleaching rates by 3.52 and 22.37%; post-discharge on the same samples largely increases

287

the ratio values bleaching (e.g., 36.7 and 51.75 for tTPDR = 4 h and 81.54 and 88.82% for 24h

288

post-discharge. Conversely, bleaching remained negligible for samples with incorporated SA

289

and exposed to the discharge in the same conditions.

290

For longer exposure times t* (e.g. 30 and 60 min), the instant R values were 41 and 73%

291

with and without SA respectively. Post-discharge effects lead to respective abatements of

292

60.96 and 79.46% within 4 h and 89 and 91.55% for tTPDR = 24h post-discharge. The

293

bleaching plasma treatment is almost inefficacious for short exposure times t* in the

294

presence of SA.

295

These results underline the efficacy of the TPDR which keep developing after the discharge

296

is switched off, especially for short exposure times t* (t* < 15min). They also evidence that

297

some RNS, such as nitrite (and/or their derivative peroxynitrite) are responsible for post-

298

discharge effects since SA affects the formation of nitrites. Such an assessment confirms

299

previous studies on the glidarc degradation of methylorange, orange G and bisphenol A.26,

300

34,35

301

The occurrence of TPDR reactions is now clearly confirmed. We have now to consider the

302

relevant kinetics by means of Absorbance and COD measurements. The influence of the

Post-discharge degradation of ARS (100 µM) in the presence and absence of sulphamic acid


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303

starting ARS concentration is examined, and C (ARS) was increased up to 335 µM, as well

304

as the post-discharge duration tTPDR to 5,7 and 30 days.

305

3.1.4. Bleaching and degradation kinetics of ARS by direct exposure to the discharge

306

The absorbance spectrum of Alizarin Red S before treatment (Fig.2) is characterized by a

307

band in the visible region with a peak at 430 nm which characterizes the chromophore group

308

and two bands located at 260 nm and 345 nm which are attributed to the benzene rings

309

2substituted by SO3 groups 26 and to the anthraquinonic part.

310

The absorbance at 260 nm decreases rather slowly and illustrates the progressive

311

degradation of the anthracene ring. The spectral changes are probably relevant to the

312

probable formation of intermediates on the benzene rings.1 Direct exposure of 335 mM ARS

313

solutions (Fig.3) to the plasma showed spectral abatements (“bleaching”) of 46.3 and 64.6

314

for t* = 30 and 60 min and the matching COD abatements (“degradation”) are 19.7 and

315

38.7% respectively. The evolution of COD with t* follows a pseudo 1st order kinetic:

316

C d[COD ] = − k[COD ] or the integral form Ln ( 0 ) = k1t * . The relevant kinetic constants for * dt C

317

bleaching and degradation are respectively 0.0146 min-1 (R² = 0.983) and 0.008 min-1 (R² =

318

0.998).

319

According to the work of Jing Xue et al.,20 the degradation process of AR in the hybrid gas–

320

liquid dielectric barrier discharge (DBD) plasma can be divided into three phases: (a) gas-

321

discharge phase; (b) ring-opening phase; (c) mineralization phase. A careless comparison of

322

these results with ours is hazardous because our work was performed with a largely more

323

powerful discharge involving arc which favored NO production. In particular there is probably

324

no NOx generated in DBDs, and hence, no peroxynitrite may be involved. Although this case

325

is out of the scope of this work to examine in details the DBD study. It is likely that kinetic

326

steps mentioned by Jing Xue et al simultaneously develop in case of glidarc discharges, as

327

(31P) NMR studies on the degradation of tributylphosphate suggest the occurrence of

328

intermediates. Anyway we agree with the limited efficacy of DBD process in the present

329

case. Also, TPDR were not yet evidenced in case of DBD. This is a substantial advantage of

330

the glidarc technique, and an indirect argument in favour of the occurrence of peroxynitrite in

331

the glidarc degradation processes.

332

3.2. Bleaching and degradation of ARS in post-discharge conditions.

333

The bleaching and degradation rates resulting from direct exposure of ARS solutions to the

334

discharge for ARS are limited, for example Rbleaching = 5, 7 and 19.3% and Rdegradation = 0, 4.6

335

and 19.3% for t* = 1, 5 and 15 min direct exposure time. These samples were abandoned in

336

post-discharge conditions for 48 h and 7 days. The matching abatements are gathered in

337

table 3 for illustration.



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338

GAD treatment allows to get bleaching and degradation rate that increases in function to t

339

duration. However, in post-discharge, elimination rates give a maximum in 0

Influence of Peroxynitrite in Gliding Arc Discharge Treatment of

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