Pulsed corona-induced degradation of organic materials in water

171 Pages·2000·2.69 MB·English

Pulsed corona-induced degradation of organic materials in
water
Citation for published version (APA):
Hoeben, W. F. L. M. (2000). Pulsed corona-induced degradation of organic materials in water. [Phd Thesis 1
(Research TU/e / Graduation TU/e), Applied Physics and Science Education]. Technische Universiteit
Eindhoven. https://doi.org/10.6100/IR535691
DOI:
10.6100/IR535691
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Published: 01/01/2000
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Pulsed corona-induced degradation of
organic materials in water
PROEFSCHRIFT
ter verkrijging van de graad van doctor
aan de Technische Universiteit Eindhoven,
op gezag van de Rector Magnificus, prof.dr. M. Rem,
voor een commissie aangewezen door het College
voor Promoties in het openbaar te verdedigen
op donderdag 15 juni 2000 om 16.00 uur
door
Wilhelmus Frederik Laurens Maria Hoeben
geboren te Geldrop
Dit proefschrift is goedgekeurd door de promotoren:
prof.dr. W.R. Rutgers
en
prof.dr.ir. C.A.M.G. Cramers
Copromotor:
dr.ir. E.M. van Veldhuizen
CIP-DATA LIBRARY TECHNISCHE UNIVERSITEIT EINDHOVEN
Hoeben, Wilhelmus Frederik Laurens Maria
Pulsed corona-induced degradation of organic materials in water / by
Wilhelmus Frederik Laurens Maria Hoeben
Eindhoven: Technische Universiteit Eindhoven, 2000. -Proefschrift.-
ISBN 90-386-1549-3
NUGI 812
Trefw: gepulste corona / elektrische ontladingen / AOP / fenol / afbraak /
oxidatie / conversie / efficiëntie / vloeistofchromatografie
Subject headings: pulsed corona / electrical discharges / AOP / phenol / degradation /
oxidation / conversion / efficiency / liquid chromatography
This project has been financially supported by “Technologie voor Duurzame
Ontwikkeling (TDO)”, Technische Universiteit Eindhoven.
Ontwerp omslag: B. Mobach / TUE
Drukwerk: Universiteitsdrukkerij Technische Universiteit Eindhoven
“A company has control of its production only if
it also knows the make-up of its waste water”
[Ullmann, Encyclopedia of Industrial Chemistry 1994, 5th edn.
Vol. B6, Weinheim: Verlag Chemie, ISBN 3-527-20136-X, 474]
Aan mijn ouders, broer en zus

Contents
1. Introduction.......................................................................................... 1
1.1 Advanced oxidation processes..................................................................... 2
1.2 Electrical discharges................................................................................... 6
1.3 Model compounds...................................................................................... 7
1.4 Thesis scope............................................................................................. 9
2. Theory..................................................................................................11
2.1 Corona discharges.....................................................................................11
2.2 Oxidizers..................................................................................................13
2.3 Degradation of organic compounds..............................................................15
2.4 Oxidation of model compounds...................................................................20
2.4.1 Phenol..........................................................................................20
2.4.2 Atrazine........................................................................................23
2.4.3 Malachite green..............................................................................23
2.4.4 Dimethyl sulfide.............................................................................24
2.5 Diagnostics..............................................................................................24
2.5.1 Chemical diagnostics ......................................................................25
2.5.2 Electrical diagnostics.......................................................................31
2.5.3 Optical diagnostics.........................................................................32
3. Experimental setup.............................................................................37
3.1 Reagents and reactors ...............................................................................37
3.2 Chemical diagnostics.................................................................................40
3.3 Electrical diagnostics.................................................................................45
3.4 Optical diagnostics....................................................................................46
4. Results .................................................................................................49
4.1 Pulsed corona discharges...........................................................................49
4.1.1 Hydroxyl radicals............................................................................49
4.1.2 Ozone...........................................................................................55
4.1.3 Corona pulse energy.......................................................................59
4.1.4 Corona treatment of deionized water.................................................63
4.2 Oxidation of phenol...................................................................................65
4.2.1 Chromatography.............................................................................65
4.2.2 Mass spectrometry.........................................................................87
4.2.3 Spectroscopy.................................................................................92
4.2.4 Electrical conductometry ...............................................................102
4.2.5 Microtox ecotoxicity.....................................................................105
4.2.6 Total organic carbon.....................................................................108
4.3 Oxidation of other model compounds.........................................................109
4.3.1 Atrazine......................................................................................109
4.3.2 Malachite green............................................................................110
4.3.3 Dimethyl sulfide...........................................................................112
5. Discussion............................................................................................113
5.1 Pulsed corona discharges.........................................................................113
5.2 Corona-induced phenol oxidation...............................................................116
5.3 Phenol oxidation pathways.......................................................................122
5.4 Analysis techniques.................................................................................137
5.5 AOP comparison.....................................................................................141
6. Conclusions..........................................................................................145
6.1 Pulsed corona discharges.........................................................................145
6.2 Oxidation of model compounds.................................................................146
6.3 Analytical techniques...............................................................................147
6.4 Outlook.................................................................................................148
7. References ...........................................................................................149
Summary...................................................................................................159
Samenvatting............................................................................................161
Dankwoord / Acknowledgements .........................................................163
Curriculum Vitae ......................................................................................164
1. Introduction
Since a long time, natural processes have not been able anymore, to rectify the
environmental load caused by the ever-increasing world population. Our water reserves
are a main issue of interest, because pollution from both the atmosphere and soil will
eventually enter the aqueous phase by deposition and percolation respectively.
Sources of pollution are both nature and mankind. Examples of natural pollution are
volcanic activity, forest fires and decomposition of vegetation. Pollution by mankind is
caused by e.g. nutrition, transportation, accommodation, synthesis and energy
exploitation. Although probably not always acknowledged, chemical activity is
indispensable to sustain life; also it is needed to comply with a high standard of living.
Examples are medicaments, cleaning and disinfecting products, cosmetics, stabilizers,
artificial fertilizers, pesticides, fuel, batteries, polymers (thermoplastics, thermosetting
resins, elastomers, fibers), paint and dyes.
Both synthesis and application of these product classes inevitably yield pollution. In
addition to biological waste like carbohydrates, proteins, urea, fats, food & vegetation
residues and carbon dioxide, we also encounter priority compounds. These materials
exhibit carcinogenic, mutagenic and/or teratogenic properties, which implies that a no-
effect-level in fact does not apply for these compounds. In addition, priority compounds
can be highly persistent.
Some organic priority compounds are for instance [1]: halogenated dioxins/
benzofurans/xanthenes from the incineration of halogenated phenols, polychlorinated
biphenyls (PCB’s) used as dielectric media, fire retardants; polycyclic aromatic
hydrocarbons (benzo[a]pyrene, dibenzo[a:h]anthracene) in soot and coal tar/pitch from
the incomplete combustion of hydrocarbons and from coal gasification; simple aromatic
hydrocarbons (benzene, nitrobenzene, p-dichlorobenzene, o-phenylenediamine) used as
precursors in organic chemical synthesis; chlorinated aliphatics (chloroform,
tetrachloromethane, trichloroethylene) applied as solvent and/or stain remover;
pesticides (DDT, kepone, lindane) for crop protection and pest control; ammunition
(TNT, picric acid, nitroanilines); monomers (acrylonitrile, vinylchloride, urethane) from
the synthesis, processing and incomplete combustion of polymers, dyes (benzidine-
based) for the colorization of e.g. textile, leather and polymers.
Inorganic priority compounds are for instance heavy metals & salts (Cd, Ni, Cr),
asbestos, arsenic/compounds, beryllium/compounds and radioactive materials.
Although we left the ages of unscrupulous operation long ago, we inherit innumerous
highly polluted waste sites of former gasworks, ammunition and pesticide plants, oil/gas
drill and refinery locations, mining sites, fuel stations, dry-cleaning facilities, waste
dump and incineration sites. Conventional microbiological degradation desperately needs
the assistance of new technologies, like for instance advanced oxidation processes, to
degrade hazardous persistent materials by chemical oxidation.
2 Chapter 1.
1.1. Advanced oxidation processes
Advanced Oxidation Processes (AOP’s) aim at the in-situ production of strong oxidizers.
The oxidizing power is reflected by the standard reduction potential E0. Table 1.1 shows
some oxidizers in decreasing power order and E0 values, expressed for reduction half-
cell reactions [2,3]. The potential is defined relative to the standard hydrogen electrode
potential [4]. The Gibbs free energy change ∆G of the redox-reaction is calculated from
the resulting electromotive force of both half-cell reactions corrected for activity
dependence (E), the number of electrons involved (n) and the Faraday constant
(F=96485 C/mol), see Equation 1.1.
Table 1.1 Standard reduction potential values for some oxidizers at T=298.15 K,
for acidic conditions pH=0 applies.
Reduction half-cell reaction E0 (V)
XeF+ e- → Xe + F- 3.4
2OF (g) + 4H+ + 4e- → O (g) + 4HF 3.29
2 2
OH + H+ + e- → H O 2.56
2
O (g) + 2H+ + 2e- → H O 2.43
2
O + 2H+ + 2e- → O + H O 2.08
3 2 2
H O + 2H+ + 2e- → 2H O 1.76
2 2 2
HClO + 2H+ + 2e- → HClO+H O 1.67
2 2
HO + H+ + e- → H O 1.44
2 2 2
Cl + 2e- → 2 Cl- 1.40
2
∆G = − n⋅F⋅E (1.1)
The strongest oxidizers known are xenonfluoride (XeF) and possibly H RnO , but these
4 6
oxidizers are not commercially attractive for water treatment because of both extreme
reactivity and remaining toxicity in reduced form. Also, halogen-based oxidizers are not
acceptable as oxidizer, because they halogenate organic materials to e.g.
trihalomethanes [5] which are very harmful compounds; in addition their reaction leads
to salt formation. It is obvious, that metal-based oxidizers like permanganate (MnO -)
4
and dichromate (Cr O 2-) also are not desirable. Of interest are thus oxygen-based
2 7
halogen/metal-free oxidizers like the hydroxyl radical (OH), atomic oxygen (O), ozone
(O ) and hydrogen peroxide (H O ).
3 2 2
Next, a concise description is presented for major AOP’s with regard to the generation
of oxygen-based halogen-free oxidizers, particularly hydroxyl radicals. A comparison of
AOP’s is discussed in section 5.5.
Introduction 3
Ozone-UV oxidation
In the ozone-UV technology [6,7], hydroxyl radicals are produced from ozone, water
and UV photons; high-pressure mercury or xenon lamps deliver the photons, see
Equation 1.2.
O + H O + hν → 2OH + O λ≤310 nm (1.2)
3 2 2
Ozone is produced on location by an ozonizer, which converts atmospheric or pure
oxygen into ozone by corona discharges [8,9]. These electrical discharges are produced
in a barrier discharge electrode setup, where the electrodes are separated by a dielectric
material e.g. glass or ceramic at a thickness of about 0.5-3 mm. The applied voltage is
8-30 kV and the frequency range is 60-2000 Hz. The energy efficiency is about 60
g/kWh for air or 120 g/kWh for oxygen [10]. The theoretical maximum efficiency is
calculated from the standard formation enthalpy change ∆H0=144.8 kJ/mol for the
f
reaction 3O →2O and is about G=1193 g O /kWh. Commercial ozone generators are
2 3 3
based on different electrode configurations, e.g. fluid-cooled shell & tube type
generators for generation of large ozone amounts and air-cooled plate type generators
for small amounts. Cooling is very important, to prevent decomposition of ozone.
Hydrogen peroxide-UV and Fenton oxidation
Hydrogen peroxide is decomposed by UV photons into hydroxyl radicals [11], see
Eq.1.3a. Also, the reaction of hydrogen peroxide with iron (II) ions produces hydroxyl
radicals; this reaction is known as the Fenton reaction (Eq.1.3b) [12]. In addition, Fe(III)
ions contribute to hydroxyl radical formation by Eq.1.3c/d (Fenton like reaction) and
indirectly by regeneration of Fe(II).
H O + hν → 2OH 250 nm<λ<300 nm (1.3a)
2 2
Fe2+ + H O → OH + OH- + Fe3+ (1.3b)
2 2
Fe3+ + OH- (cid:22) Fe(OH)2+ (1.3c)
Fe(OH)2+ + hν → OH + Fe2+ λ=350 nm (1.3d)
The advantage of photo-Fenton/Fenton like reactions over hydrogen peroxide-UV is
mainly explained by the efficient use of light quanta, because the absorption of Fe(III)
chelates (hydroxo, carboxyl) extends to the near UV-visible region and their molar
absorption coefficient is relatively high compared to the molar absorption coefficient of
hydrogen peroxide. Synthesis of hydrogen peroxide is mainly performed according to
the following processes [13,14]:
*Anthraquinone (AO) process: Reduction of a 2-alkyl-9,10-anthraquinone to the
corresponding hydroquinone by hydrogen, followed by the oxidation of the
hydroquinone by oxygen to hydrogen peroxide and the anthraquinone.
*2-Propanol process: Oxidation of 2-propanol by oxygen produces 2-propanol-2-
hydroperoxide, which decomposes into hydrogen peroxide and acetone.
*Electrochemical processes: Anodic oxidative coupling of sulfate ions to persulfate ions,
followed by hydrolysis of the persulfate via the peroxomonosulfate to hydrogen
peroxide and bisulfate ions.
The theoretical maximum efficiency, calculated from the standard formation enthalpy
change ∆H0=98.3 kJ/mol for the reaction H O (l) +½O (g) → H O (l) is about
f 2 2 2 2
G=1246 g H O /kWh.
2 2