Mehmet A. OTURANLaboratoire Géomatériaux et Environnement (LGE)Université Paris-Est Marne-la-Vallée - France

Procédés électrochimiques d'oxydation avancée:

Application au traitement des eaux contaminés

par les polluants organiques persistants.

Journée Sci. ICMPE, 15 novembre 2011

ELECTROCHEMISTRY FOR A CLEAN WORLD

Wastewater treatment process

Use of a strong oxidizing agent (.OH)

Conventional processes :- microbiological- physical (decantation, filtration, adsorption)- physicochemical (coagulation, flocculation)- chemical (chemical oxidation)

Toxic and persistent organic pollutants (POPs)

Necessity to use Advanced oxidation processes (AOPs) :

Advanced Oxidation Processes (AOPs)

Processes based on the in situ generation and oxidizing power of hydroxyl radicals •OH

•OH : a powerful oxidizing agentOxidizing agent Oxidizing power, E0 (V/NHE)

F2 3.03.OH 2.80.O 2.42O3 2.07H2O2 (acidic media) 1.78

HO2. 1.70

Cl2 1.36O2 1.23

Ar + .OH Ar(OH). kadd = 109 - 1010 M-1 s-1

RH + .OH R. + H2O kabst. H = 107 - 109 M-1 s-1

.OH + e- + H+ H2O E0 = 2,80 V / NHE

Advanced oxidation processes (AOPs)

•OH reaction modes:

.OH : very reactive species

Chemical •OH production

H2O2 + Fe2+ Fe3+ + OH- + ●OH

Fenton’s reaction:

Fenton’s reaction

H2O2 + Fe2+ Fe3+ + OH- + .OH

1) Use of great amount of chemical reagents

(reagent cost)

Disadvantages

Fenton’s reaction

H2O2 + Fe2+ Fe3+ + OH- + .OH

Fe(OH)3

2) Formation of process sludge

Disadvantages

Fenton’s reaction

H2O2 + Fe2+ Fe3+ + OH- + .OH

Fe(OH)3

Fe2 + .OH Fe3+ + OH-

H2O2 + .OH H2O + HO2•

3) Parasitic reactions :

k = 3.5 107 M-1 s-1

k = 3.2 108 M-1 s-1

Disadvantages

How to avoid the drawbacks of the Fenton’s process?

How do it ?

Electrochemistry offers a fantastic means for insitu and catalytic generation of Fenton’s reagent

Answer: In situ, controlled and continue production of the Fenton’s reagent

Fenton’s reaction + electrochemistry

Fenton’s reaction : H2O2 + Fe2+ Fe3+ + OH- + .OH

Electrochemistry : In situ synthesis ofFenton’s reagent

Organicpollutants

CO2

Electro-Fenton

Electro-Fenton process (EFP)

Electrochemical reactor

Reagent : compressed air / O2

Catalyst : Fe3+ , Cu2+ , ... ( ≈ 0.1 mM )

Electrochemistry Chemistry

EF : Fenton’s reaction assisted by electrochemistry

O2 + 2H+ + 2e- H2O2

Fe3+ + e- Fe2+

+ Fe3+ + OH- + •OH

Electro-Fenton process (EFP)Electrocatalysis: Electrocatalytic production of ●OH

Overall reaction:

OH.

Fe2+

Fe3+

e-

2 e-

H2O2

OH-

H+

H2O

2 e-

1/2 O2 + 2 H+

Oturan et al., J. Electroanal. Chem., 507 (2001) 96

O2 + 2 H2O 4 OHelectricalenergy

Electrochemical reactor for EF(Lab scale)

6

3.00 V 0.20 A7

1

2

3

4

5

+ -

Fe3+

Fe2+

H2O2

O2

CompressedAir

300 mL

2 L

Follow-up of degradation/mineralization

To follow up the evolution of chemicalcomposition/mineralization of treated solutions :

HPLC : Concentration decay of starting pollutant and evolution of aromatic intermediates

Ion-Exclusion Chromatography : Evolution of carboxylic acids

IC : Liberated mineral ions

TOC / COD : Mineralization efficiency

EF treatment of herbicide 2,4-D aqueous solution

M.A. Oturan, J. Appl. Electrochem., 30 (2000) 475-483

Evolution of the solution chemical composition (HPLC analysis)

Cl O-CH2-COOH

Cl

C0 = 1 mMV0 = 125 mLE = - 0.5 V vs SCE

Aromatic intermediatesI : 2,4-DII : 2,4-dichlorophénolIII : 2,4-dichlororésorcinolIV : 4,6-dichlororésorcinolV : 2-chlorohydroquinoneVI : 2-chlorohydroquinoneVII : 1,2,4-trihydrobenzene

a) 0 Cb) 50 Cc) 150 Cd) 250 Ce) 400 Cf) 700 C

Electro-Fenton Process (EFP)

Applications with

CARBON FELT Cathode

Effect of operating parameters

EFP applications : Degradation kinetics of DIURON

Effect of applied current

[Fe3+] = 0.2 mM

NH

CO

NCH3

CH3

Cl

Cl

DIURON: Chlorophenylurea herbicide

Edelahi M. C., ………Oturan M.A., Environ. Chem. Lett., 1 (2004) 233.

0

0.04

0.08

0.12

0.16

0.2

0 2 4 6 8 10 12 14 16t (min)

[DIU

] (m

M)

y = 0.4835xR2 = 0.9982

y = 0.8071xR2 = 0.9951

y = 0.2944xR2 = 0.9987

0

2

4

6

8

10

12

0 5 10 15t (min)

Ln(C

0/C t

)

I (mA): 100 ( ); 200 ( ); 300 ( )

0 5 10 15 20 25 300,00

0,04

0,08

0,12

0,16 diuron [Fe3+]= 0,5mM

[Fe3+]= 1mM

[Fe3+]= 2mM

[Fe3+]= 4mM

[C] (

mM

)

Temps d'électrolyse (min)Electrolysis time / min

I = 100 mA

EFP : Degradation kinetics of DIURON

Effect of catalyst concentration

Edelahi M. C., ………Oturan M.A., Environ. Chem. Lett., 1 (2004) 233.

0.2 mM

0.5 mM

1.0 mM

2.0 mM

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70

Time (min)

5 min

15 min

0

0.002

0.004

0.006

0 10 20 30 40 50 60 70Time (min)

Con

cent

ratio

n (m

M)

DCPMUDCPUDCA FA

EFP applications : Toxicity evolution during treatment

Inhi

bitio

n (%

)

Evolution of reaction intermediates

Toxicity evolution

Microtox® methodVibrio fischeri bacteria luminescence

[Diuron] = 8.9 mg L-1

I = 50 mA, [Fe3+] = 0.2 mMV = 300 mL

Oturan N., Trajkovska S., Oturan M.A., Chemosphere, 783 (2008) 1550-1556

Degradation vs. MINERALIZATION

EFP applications: Methyl parathion (insecticide) degradation

[MP]0 = 0.12 mM, [Fe3+] = 0.1 mM, I = 60 mA, V = 0.150 L

HClO4 medium, pH = 3

Evolution of MP and its aromatic intermediates

0

0.04

0.08

0.12

0 10 20 30 40

Time (min)

[PM

] (m

M)

ParathionParaoxon4-nitrophenolHydroquinone4-nitrocatecholBenzoquinone

Diagne M., Oturan N., Oturan M.A., Chemosphere, 66 (2007) 841-848

OO2N PS

O CH3

O CH3

EFP applications: Methyl parathion degradation

[MP]0 = 0.1. mM,

[Fe3+] = 0.1 mM,I = 60 mA, V = 0.150 LHClO4 medium, pH = 3

Evolution of:

(a) Carboxylic acids (Ion-Exl Chrom)

(b) Inorganic ions (Ion chrom)

during EF treatment

(b)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0 2 4 6 8 10

Con

cent

atio

n (m

M)

GlycoliqueMaléiqueAcétiqueFormiqueOxalique

(a)GlycolicMaleicAceticFormicOxalic

0.00

0.03

0.06

0.09

0.12

0.15

0 2 4 6 8 10

Time (h)

[Ion

s] (m

M)

Sulphate ionNitrate ionPhosphate ion

(b)

SulphateNitratePhosphate

OO2N PS

O CH3

O CH3

EFP : Mineralization of MP

Mineralization reaction :

Oxidation by OH radicals:

C8H10NOPS + 48 ●OH 8CO2 + 26H2O + NO3- + PO4

3- + SO42-

Equivalent electrochemical oxidation:

C8H10NOPS+22H2O 9CO2 (g) +NO3- + PO4

3- +SO42- + 54H++48e-

48 ●OH / mole MP

48 e- / mole MP

OO2N PS

O CH3

O CH3

•EFP applications: Methyl parathion mineralization

[MP]0 = 0.2 mM [Fe3+] = 0.1 mM I = 150 mAV = 0.150 LpH: 3

Mineralization efficiency (TOC removal)

pH = 3 (HClO4) I = 150 mA

0

4

8

12

16

20

0 100 200 300 400 500 600

Time (min)

TO

C (m

g L-1

)

OO2N PS

O CH3

O CH3

Treatment Time : 1h 3h 9h

% TOC removal : 65 85 100

EFP applications: Methyl parathion degradation pathway

OO2N PS

O CH3

O CH3

OO2N PO

O CH3

O CH3

HO PO

O CH3

O CH3

OHO2N

OHO2N

OH

OHO2N

OH

OHO2N

O2

HO

OHHO

OO

PO43-

NO3-

OH/O2

oxidative ring opening

OH/O2

+

- SO42-

.OH addition electron transf ert

OH

MP mineralization by •OH radicals

HOHOOO

O

OHH

O

OHO

HO

oxidative ring opening

aliphatic compounds

CO2 + H2O

OH/O2

OH/O2

carboxylic acids

O

OHH3C

Diagne M., Oturan N., Oturan M.A., Chemosphere, XX (2007) XXXDiagne M., Oturan N., Oturan M.A., Chemosphere, 66 (2007) 841-848

EFP / ApplicationsEFP / Applications

Pesticides (active ingredients) :- Chlorophenoxy acids (2,4-D, MCPP, 2,4,5-T, ……)- Organophosphorus (marathon, parathion methyl, ace hate, TEPP,…..)- urea (diuron, fenuron, monuron)- Imidazolines (imazapyr, imazaquin)- Triazines (atrazine)

Pesticides (commercial formulations) : Mistel GD, Cuprofix CD, Lannate 20L

Pesticides (raw effluent) : Cocktail of viticulture’s pesticides

Industrial pollutants : - BPA (Bisphenol A), - Chlorophenols, - Nitrophenols

Synthetic dyes :- Azo dyes (azobenzene, p-methyl red, methyl orange….)- Triphenylmethanes dyes (malachite green, crystal violet, methyl green, …)

Landfill LeachatesReverse osmosis concentratesMargins (Olive Oil Mill Wastewater)Pharmaceutical and personal care products: Antibiotics, antimicrobials, β-blockers

Type (family) of POPs studied

EFP / Applications

Determination of the rate constants

Absolute rate constants (kabs) between organics and OH

Competition kinetics with astandard substrate:

kabs(P) = kabs(S) × [kapp(P) / kapp(S)]0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25Time / min

[4-C

P] /

mM

0

1

2

3

4

5

6

7

0 5 10 15 20Time / min

Ln (C

0/C)

kapp : Apparent rate constant followingpseudo-first-order kinetics

Oturan N., Panizza M.,Oturan M.A., J. Phys. Chem. A., 113 (2009) 10988-10993

Chlorophenol kabs (109) M-1 s-1

4-CP 7.75±0.07

2,6-DCP 6.13±0.05

2,4,5-TCP 5.72±0.05

2,3,5,6-TeCP 4.95±0.07

PCP 3.56±0.06

EFP / ApplicationsDetermination of the rate constants

Brillas E., Sirés I., Oturan M.A., Chemical Reviews, 109 (2009) 6570-6631

Organic compound C0a

/ mMOperation conditions Current

/ mAEcat

b

/ V vs. SCEk2,P×10-9

/ M-1 s-1

PesticidesDivided cell

2,4-D121

Imazapyr193

Undivided cellMethyl parathion186

Picloram190

Propham191

Pentachlorophenol192

Diuron194

Chlortoluron197

Carbofuran197

Bentazone197

Imazapyr198

Imazaquin198

DyesUndivided cells

Basic Blue 9195,d

Direct Red 28195,e

Reactive Orange 70195,f

Direct Orange 61196,g

Basic Blue 20199,h

Basic Green 4199,i

Basic Violet 3199,j

Food Green 3199,k

1.00.10

0.130.1250.500.030/170.050.050.050.100.10

0.250.250.250.050.050.050.050.05

150 ml, 0.01 M H2SO4, 1 mM Fe3+

125 ml, pH 3, 0.5 mM Fe2+

150 ml, pH 3, 0.1 mM Fe3+

150 ml, 0.05 M Na2SO4, pH 3, 0.2 mM Fe3+

150 ml, 0.05 M Na2SO4, pH 3, 0.5 mM Fe3+

125 ml, pH 3, 1 mM Fe2+

125 ml, pH 3, 0.5 mM Fe3+

150 ml, 0.05 M Na2SO4, pH 3, 0.1 mM Fe3+

150 ml, 0.05 M Na2SO4, pH 3, 0.1 mM Fe3+

150 ml, 0.05 M Na2SO4, pH 3, 0.1 mM Fe3+

125 ml, pH 3, 0.1 mM Fe3+

125 ml, pH 3, 0.1 mM Fe3+

125 ml, pH 3, 0.5 mM Fe3+

125 ml, pH 3, 0.5 mM Fe3+125 ml, pH 3, 0.5 mM Fe3+500 ml, pH 3, 0.05 M Na2SO4, 0.1 mM Fe2+

250 ml, pH 3, 0.05 M Na2SO4, 0.2 mM Fe3+

250 ml, pH 3, 0.05 M Na2SO4, 0.2 mM Fe3+

250 ml, pH 3, 0.05 M Na2SO4, 0.2 mM Fe3+

250 ml, pH 3, 0.05 M Na2SO4, 0.2 mM Fe3+

1006060501006060606060

6040404040

−0.50−0.50

−0.50−0.50−0.50

355.4

4.22.72.23.64.84.93.22.64.55.4

2.45.514211.32.72.52.2

0

5

10

15

20

25

30

0 120 240 360 480 600 720

Durée d'électrolyse / min

CO

T / m

g C

L-1

30 mA60 mA120 mA200 mA300 mA350 mA400 mA450 mA

Sulfamethoxazole (SMX): Antibiotic

Application to the removal of pharmaceuticals

0

0.05

0.1

0.15

0.2

0.25

0 10 20 30 40 50 60 70

(b)( ) 60

( ) 120

(Δ) 300

(◊) 400

( ) 450

Effect of the applied current on the destruction of SMX

Effect of the applied current on the destruction and mineralization of SMX

[SMX]0 = 0.208 mM, [Fe2+] = 0.2 mM.

Treatment time / minTreatment time / min

[SMX

] / mM

A. Dirany, I. Sirés, Oturan N., M.A. Oturan, Chemosphere, 81 (2010) 594-602

H2N

SNH

N O

O O

Sulfamethoxazole (SMX)

Application to the removal of pharmaceuticals

Toxicity evolution of SMX (0.208 mM) during EF treatment

Evolution of Toxicity of the SMX aqueous solution during EF treatment (Pt anode, I = 300 mA)

0.00

30.00

60.00

90.00

120.00

0 30 60 90 120 150 180

time (min)

% in

hibi

tion

inh 5min

inh 15min

-30,00

0,00

30,00

60,00

90,00

120,00

0 30 60 90 120 150 180 210 240 270

Time / min%

Inh

15 m

in

AMIBZQ

Method: Microtox (luminescence inhibition of marine bacteria Vibrio fischeri)

Toxicity evolution of 2 main metabolites of SMX: BZQ and AMI (3-Amino-5-methylisoxazole) at C0 = 0.016 mM

H2N

N OOO

BZQ

AMI

A. Dirany, ……M.A. Oturan, Anal. Bioanal. Chem., 400 (2011) 353–360

H2N

SNH

N O

O O

SMX

kSMX = 1.6 x 109 M-1 s-1 kBZQ = 6.1 x 109 M-1 s-1

kAMI = 1.1 x 1010 M-1 s-1

Coupling between EF and other AOPs

To enhance the efficiency of EF:

Association of EF with anodic oxidation

Association of EF with other AOPs● Sono-electro-Fenton● Photo-electro-Fenton● Peroxycoagulation

COMBINED ELECTRO-FENTON

Electro-Fenton with BDD anode

Anodic oxidation process

Production of heterogeneous hydroxyl radicals M(●OH) by oxidation of water

Necessity to use a high O2-overvoltage anode: (SnO2, PbO2, IrO2) to favour ●OH generation

BDD + H2O → BDD(●OH) + H+ + e-

M + H2O → M(●OH) + H+ + e-

Principle: •OH production by direct electrochemistry

BDD anode: High •OH production efficiency

BDD + H2O → BDD(●OH) + H+ + e-

Anode: HeterogeneousBDD(•OH)

Cathode: Homogeneous •OH

O2 + 2H+ + 2e- → H2O2

Fe3+ + e- → Fe2+

H2O2 + Fe2+ → Fe(OH)2+ + •OH

More •OH production

Coupled EF-AO (BDD anode) process

Mineralization of ATRAZINE by AOPs

Mineralization degree already reached by chemical and photochemical AOPs: 60%

Mineralization by AOPs: until cyanuric acid (as end-product)

N

N

N

Cl

NH

CH(CH3)2

HN

C2H5

N

N

N

OH

OHHO

ATRAZINE CYANURIC ACID

OH

Mineralization of ATRAZINE by different EAOPs

0

2

4

6

8

10

0 2 4 6 8

TOC / mg  L‐1

Electrolysis time / h

EF‐Pt

EF‐BDD

OA

Oturan N., Brillas E., Oturan M.A., Environ Chem. Lett. (in press)

Process Mineralization %

EF Pt 80AO (BDD) 93EF-BDD >97

N

N

N

Cl

NH

CH(CH3)2

HN

C2H5

N

N

N

OH

OHHO

OH+ CO2 + HNH4 + HNO3 + H2O

Mineralization of CYANURIC ACID by different EAOPs

0

2

4

6

8

0 2 4 6 8 10

TOC / mg  L‐1

Electrolysis time / h

EF‐Pt

EF‐BDD

AO (BDD)

Oturan N., Brillas E., Oturan M.A., Environ Chem. Lett. (in press)

Process Mineralization %

EF Pt 4.2AO (BDD) 80EF-BDD 90

N

N

N

OH

OHHO

CO2 (g) + NH4+ + NO3

- + H+ + H2OOH

EFP / Applications

Chemical industry (CHEDITE)

REAL WASTEWATER TREATMENNT

Mineralization degree: 87%BDD anode, I = 1 A

Before After treatmentBefore After treatment

Landfill Leachates

Mineralization degree: 96%BDD anode, I = 1 A

COMBINED ELECTRO-FENTON

Coupling with other AOPs

Sono-electro-Fenton

Electro-Fenton

Ultrasons POA OH

ultrasounds

Sono-electro-Fenton : EF + US

Electro-Fenton (EF) : Production of OH by Fenton’s reactionH2O2 + Fe2+ → Fe(OH)2+ + •OH

Ultrasounds (US) : Degradation of organics by:- pyrolysis (in cavitation bubble)- •OH formed during water sonolysis

H2O H• + •OH

Sono-electro-Fenton

0

0.2

0.4

0.6

0.8

1

0 500 1000 1500 2000Charge / C

Con

cent

ratio

n / m

M

EF + US (60W)EF + US (20W)EF + US (80W)Electro-Fenton seule

Degradation of 2,4-D

O-CH2-COOH

Cl

Cl

Oturan M.A et al., J. Electroanal Chem., 624 (2008) 329

EF : H2O2 + Fe2+ Fe(OH)2+ + ●OH

PF : irradiation by UVA : Fe(OH)2+ + hν → Fe2+ + •OH

Photoelectro-Fenton : EF + PF

Advantages:1) More •OH formation2) Improvement of mineralization efficiency (photo-decomposition

of Fe(III)-carboxylic acid complexes).

Photo-electro-Fenton

0

20

40

60

80

100

120

0 60 120 180 240 300 360 420

TO

C

t

ab

c

d

/ ppm

/ min

(a) Anodic oxidation with Pt/graphite(b) Anodic oxidation in presence of electrogenerated H2O2 with Pt/O2(c) electro-Fenton with Fe2+ (1 mM)(d) photoelectro-Fenton with Fe2+ (1 mM) and UV irradiation (λmax = 360 nm)

Photoelectro-FentonTOC abatement (mineralization) of 4-CPA solution

C0 = 194 ppm

Na2SO4 = 0.05 M

V = 100 ml

pH = 3,0

I = 100 mA

T = 35 ºC

B. Boye, …… E. Brillas, Environ. Sci. Technol. 36(2002) 3030

Perspectives

Conception: electrode material / form

Coupling with biotechnology: bio-electro-Fenton

EF - SBREF - MFC

Modeling of the process

Pilot: from lab scale to industrial scale(conception and building of a pilot plant)

CONCLUSIONS

Efficiency : High efficiency in elimination of organic pollutants, particularly in case of the pesticides, dyes, industrial pollutants, ….

Process :

Easy setting up

Environmentally friendly- no chemical reagent used- total mineralization of pollutants reached - no production of process sludge- transport and storage of H2O2 avoided

Economical- low energy consumption