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16-07-2017
1
TREATMENT OF AGRO-INDUSTRIAL AND TEXTILE WASTEWATERS BY FENTON BASED
PROCESSES
José Alcides PeresUniversidade de Trás-os-Montes e Alto Douro (UTAD)
Vila Real, Portugal
2nd Summer School on Environmental Applications of Advanced Oxidation ProcessesPorto, Portugal, July 10-14, 2017
• Agro-industries are one of the main sources of waterpollution in the industrial sector.
• Some agro-industrial wastewaters cannot be effectivelytreated by conventional biological processes due to their hightoxicity, low biodegradability and seasonal production.
1. INTRODUCTION
2
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2
• Advanced oxidation processes (AOPs), a chemical approach,can be used to oxidize organic compounds found inwastewaters which are difficult to handle biologically intosimpler end products.
• AOPs involve the generation of free hydroxyl radical (HO˙), apowerful, non-selective chemical oxidant.
• Hydroxyl radical is one of the most active oxidizing agentsknown. It acts very rapidly with most organic molecules withrate constants in the order of 108 – 1011 M-1 s-1.
1. Introduction
3
Standard reduction potential of some oxidizing agents
Oxidising agent Eº (V, 25ºC)Fluor 3.03
Hydroxyl radical 2.80Atomic oxygen 2.42
Ozone 2.07Hydrogen peroxide 1.78
Hydroperoxil radical 1.70Permanganate 1.68
Hipobromure acid 1.59Chlorine dioxide 1.57
Hypochlorous acid 1.49Hypoiodide acid 1.45
Chlorine 1.36Bromide 1.09Iode 0.54
1. Introduction
4
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Depending upon the nature of the organic species, generatedhydroxyl radicals can attack organic structures by four mainmechanisms :
(a) hydrogen abstraction RH + HO R + H2O
(b) radical additionHO + X2C=CX2 X2C(OH)-CX2
(c) electron transfer RX + HO RX+ + HO-
(d) radical combinationHO + HO H2O2H2O2 + HO HO2 + H2O
1. Introduction
5
2. FENTON PROCESSES
2.1. Fenton reagent
For over a century (1894) it was first described by Henry Fenton (England)the catalytic oxidation of tartaric acid in the presence of Fe2+ andhydrogen peroxide.The oxidation mechanism of this system is due to the reactivity ofhydroxyl radicals generated in acid medium, by the catalyticdecomposition of hydrogen peroxide in the presence of Fe2+:
Fe2+ + H2O2 Fe3+ + HO- + HO. k = 76 M-1s-1
6
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OH Fe HO Fe 32 2222 HO OH HO OH
HO Fe HO Fe 23
22
H O Fe HO Fe 22
23
.2
222
3 HO H Fe OH Fe
The catalytic action is enhanced by the reduction of Fe3+ to Fe2+ .
In Fenton's reagent, in addition to the basic reaction (initiation step), it ispossible to provide various competitive reactions involving Fe2+, Fe3+,H2O2 and HO radicals:
2.1. Fenton reagent
7
Agro-industrial wastewater treatment – North of Portugal
Olive mill wastewater (OMW) Winery wastewater (WW) Candied fruit wastewater
and also:
Textile industry wastewater
1. Introduction
8
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9Douro Valley
10Douro Valley
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6
pHBOD5 COD TSS VSS Oil and fatsTotal polyphenolsN KjeldahlBOD5/COD
4.832 00092 50067 07039 920
6272 095
3900.346
6.0 – 9.040
15060-
150.515-
Parameter Olive mill wastewater(batch process)
Limit value(DL 236/98) Units
-mg O2/L
mg O2/L
mg/L
mg/Lmg/L
mg/L
mg/L-
Characteristics of olive mill wastewater (OMW)
1. Introduction
11
COOH
OH
CH=CHCOOH
OH
CH=CHCOOH
OH
OH
CH=CHCOOH
OCH 3
OH
COOH
OCH 3
OH
COOH
OH
OH
COOH
OH
OH
COOH
OCH 3
COOH
OCH 3H3CO
OCH 3
COOH
OH
OCH 3H3COOCH 3
ácido p-hidroxibenzóico
ácido p-cumárico ácido cafeico ácido ferúlico
ácido -resorcílico ácido protocatéquico ácido vanílico
ácido verátrico ácido 3,4,5-trimetoxibenzóico ácido siríngico
Phenolic acids- Present in OMW
12
In our study of OMW treatment we thought it would be important to begin by understanding the effect of the FR on phenolic acids.
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a) Effect of molar ratio H2O2/pHB acid (4:1)
0 10 20 30 40 50 60
0
20
40
60
80
100
Molar ratioH
2O
2:ác.pHB
8:1 without Fe2+
1:1 2:1 3:1 4:1 5:1 8:1 10:1 20:1
p-hy
drox
yben
zoic
aci
d (m
g/L)
Reaction time (min)
Fenton reagent – (1) p-hydroxybenzoic acid
2.1. Fenton reagent
13
p-hydroxybenzoic acid
We began by studying the pHB acid: taken as compound model.
b) Effect of pH(pH=3.0-3.5)
c) Effect of temperature(T=30oC)
INFLUENCE OF OPERATING VARIABLE
1 2 3 4 5
0
20
40
60
80
100
pHB
aci
d de
grad
atio
n (%
)
pH
0 10 20 30 40 50 60
0
20
40
60
80
100
Temperature 10º C 20º C 30º C 40º C 50º C
p-hy
drox
yben
zoic
aci
d (m
g/L)
Time (min)
2.1. Fenton reagent
14
Fenton reagent – (1) p-hydroxybenzoic acid
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8
0 10 20 30 40 50 60
0
20
40
60
80
100
Razão molar H2O2:Fe2+
30:1 - (20,1 mg Fe2+/L)
15:1 - (40,2 mg Fe2+/L)
3:1 - (201,0 mg Fe2+/L)
Áci
do p
-hid
roxi
benz
óico
(mg/
L)
Tempo de reacção (min)
0 10 20 30 40 50 60
150
200
250
300
350
400
450
500
550
Razão molarH2O2:ác.pHB
R=1 R=2 R=3 R=4 R=5O
RP (m
V)
Tempo de reacção (min)
e) ORP variationd) Effect of Fe2+ concentration([H2O2]/[Fe2+] = 15)
2.1. Fenton reagent
INFLUENCE OF OPERATING VARIABLE
Fenton reagent – (1) p-hydroxybenzoic acid
15
- It is observed a large increase in ORP value immediately after the addition of H2O2
RR
lnkk
BB
ln 0R
B0
Oxidation experiments were performedwith the Fenton reagent using thecompetitive kinetic method (Haag andYao, 1992). We used mixtures of thesephenolic acids, with p-HB acid alwaysbeing present as reference compound.
- This allowed us to calculate the rateconstants (30°C, pH=3.5) of the reactionsbetween the hydroxyl radicals and thedifferent phenolic acids.
Fenton reagent – (2) Phenolic acids
2.1. Fenton reagent
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Phenolic acid kOH (x 109 ) (L/mol.s)
Ferulic acidp-Coumaric acidVeratric acidp-hydroxybenzoic acid-Resorcilic acidCafeic acidSiringic acidVanillic acid3,4,5-Trimetoxybenzoic acidProtocatechuic acid
3.842.532.212.192.171.801.731.471.240.67
Fenton reagent – (2) Phenolic acids
Competitive kinetic method
2.1. Fenton reagent
17
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,48,9
9,0
9,1
9,2
9,3
9,4
9,5
9,6
log
k HO
·
iINDUC
COOH
OCH3OCH3
H3CO
COOH
OCH3OH
H3CO
COOH
OCH3OH
C H C O O H C H
O H
O H
C O O H
O H
O H
COOH
OCH3OCH3
C O O H
O H
O H
C H C H C O O H
C H 2 C H 2 C O O H
O H
COOH
Logarithmic representation of hydroxyl reaction constants versus Hammettconstants of the substituents for the reaction of phenolic acids with HOradicals.
18
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Fenton reagent – (3) Olive mill wastewater
Stage 1:COD + H2O2 + Fe2+ species partially oxidized (1)
Stage 2:species partially oxidized + H2O2 + Fe2+ CO2 + H2O + inorganic salts (2)
In this case, we took as reference a global parameter: the COD value.
The reduction of COD by the Fenton reagent can be summarized as follows:
2.1. Fenton reagent
19
0 5 10 15 20 25 30 35
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
5,5
Temperature 10ºC 20ºC 30ºC 40ºC 50ºC
ln[(
COD
0-CO
Din
f)/(C
OD
-CO
Din
f)]
Time (min)
.tk)COD (COD)COD(CODln D0
b) Kinetic model
0 10 20 30 40 50 600
10
20
30
40
50
60
70
H2O2/COD=1.75 H2O2/COD=1.05 H2O2/COD=0.35
CO
D re
mov
al (%
)
Reaction time (min)
a) Influence of operating variables
Experiments with Fenton's reagent toassess the effect: concentration of H2O2 Fe2+ concentration temperature initial pH
Numerator and denominator aresubtracted by the COD valuesremaining after a long time period.
Fenton reagent – (3) Olive mill wastewater
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Ponderal ratio R=H2O2/COD effect in COD reduction of OMW and
sludge percentage reduction. (Conditions: temperature=30ºC, pHinitial = 3,5 e molar ratio H2O2/Fe2+ = 15:1).
A. Fenton reagent + B. Coagulation/Floculation/Decantation with Ca(OH)2
0,0 0,5 1,0 1,5 2,0 2,5 3,0
0
5000
10000
15000
20000
25000
30000
35000
CODfinal
CO
Dfin
al (m
g O
2/L)
R=H2O
2/COD
8
12
16
20
24
28
32
Slud
ge (%
v/v
)
Sludge
2.1. Fenton reagent
21
Fenton reagent – (3) Olive mill wastewater
2.2. Photo-Fenton process
In aqueous solution, the ferric ion (Fe3+) tends to form several complexes.
Fe(OH)2+ complex is the dominant for the pH range 2.5-5.0 and absorbsradiation in the UV range with larger absorption coefficient than Fe3+ (aq).
Its photolysis leads to the formation of Fe2+ ions and HO :
Fe(OH)2+ + h Fe2+ + HO
The Fe2+ generated during irradiation, in the presence of H2O2, reacts with thisgiving sequence to the Fenton reaction. In this context, the reaction is catalytic andis established a cycle in which Fe2+ is regenerated.
2.2. Photo-Fenton process
22
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End products
CO2+ H2O
Fenton’s reagent
UV
UV
The high efficiency of photo-Fenton process is due to the formation of more hydroxyl radical than the Fenton reagent.
Photo-Fenton process
2.2. Photo-Fenton process
23
Dye degradation Reactive Black 5 by photo-Fenton process
Reactive Black 5 (RB5)
• Azo dye (N=N) reactive type
N NNaO3SOCH2CH2O2S SO3Na
HO
H2N
SO3NaN NNaO3SOCH2CH2O2S
2.2. Photo-Fenton process
24RB5 as a representative dye pollutant of textile wastewaters
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13
0 50 100 150 200 2500
20
40
60
80
100
H2O2 UV UV and Fe H2O2 and UV Fenton Photo-Fenton
Perc
enta
ge o
f rem
aini
ng
Time (min)
- Comparison between different oxidantsRB5 degradation
CRB5 =1,0x10-4 mol/L; CFe2+=1,5x10-4 mol/L; CH2O2 = 7,3x10-4 mol/L;
Temperature = 20oC; UV lamp = Heraeus TNN 15/32
2.2. Photo-Fenton process
25
After 15 min we have 99% of RB5degraded
200 300 400 500 600 700 800
0
1
2
3
4
5
A..K
Abs
orba
nce
Wavelength (nm)
Spectrum UV/VIS: evolution over time - photo-Fenton process
0 min
.
.
1 Hora
15 seg
0 min
30 seg
N NNaO3SOCH2CH2O2S SO3Na
HO
H2N
SO3NaN NNaO3SOCH2CH2O2S
310 nm – aromatic fraction595 nm – color
2.2. Photo-Fenton process
RB5 degradation
26
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14
2.3. Iron complexes in Fenton and photo-Fenton reactions
The use of iron complexes in the degradation of organic contaminants inphoto-Fenton reaction allows the stabilization of iron in a wider range ofpH values.
• The iron complex also contributes to increasing the light absorptionefficiency by extending the range of absorption of the reaction mediumfor the visible region.
– Its photolysis is sensitive to radiation with wavelengths between 200 and 500 nm.
• Potassium ferrioxalate is a Fe3+ complex used in photochemicalapplications and photo-Fenton processes.
2.3. Ferrioxalate
27
• The photolysis of Fe3+-oxalate (ferrioxalate) complex generates Fe2+ ionsin acid solution, with a quantum yield () known ( = 1.0-1.2).
• Can be expressed by the following reactions:
4224223342 OCO2CFehν)OFe(C
22422334242 2COO3CFe)OFe(COC
22242 2COOOOC
Adding H2O2 photochemical reduction of Fe3+ complex combines with theFenton reaction generating hydroxyl radicals:
OHHO)OFe(ChνOH)OC(Fe 422242
2.3. Ferrioxalate
28
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200 300 400 500 600 700 800
0
1
2
3
t=60 mint=0 min
Abs
orvâ
ncia
Comprimento de onda (nm)
0 10 20 30 40 50 600
20
40
60
80
100
Time Evolution: Ferrioxalate/H2O2/Solar light Fenton/UV-C
RB5
Dec
olor
izat
ion
(%)
Time (min)
Discolouration high and very similar:
• Photo-Fenton = 98.7%• Ferrioxalate/H2O2/sunlight = 96.1%
Photo-Fenton
Fe2+ + H2O2 Fe3+ +OH- + HO•
H2O2 + h (UV) 2HO
Fe3+ + H2O + h (UV) Fe2+ + H+ + HO•
Ferrioxalate
[Fe(C2O4)3]3- + h (solar) Fe2+ + 2C2O42- + C2O4-•
C2O4-• + [Fe(C2O4)3]3- Fe2+ + 3C2O42- + 2CO2
C2O4-• + O2 O2-• + 2CO2
Comparison between ferrioxalateprocess/H2O2/sunlight and photo-Fenton
Reactive Black 5 (RB5)
2.3. Ferrioxalate
29RB5 can be effectively decolorized using Fenton/UV-C and ferrioxalate/H2O2/solar radiation processes with a small difference between the two processes.
2.4. Photo-Fenton with solar radiation
The efficiency in the degradation of different classes of compounds hassuggested the photo-Fenton process activated by solar radiation as veryattractive.
Different designs of solar photocatalytic reactors:(a) no concentrating system(b) PTC - Parabolic concentrating reactor(c) CPC – Compound Parabolic Collector
2.4. Photo-Fenton with solar radiation
30
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CPC
Tank
Pump
CPC
Tank
Pump
20 l·min-1
CPCs (Vi = 22 l) 3 x 1.03 m2
Picture and schematic representation of the CPC reactor
Compound Parabolic Collector:- 3.1 m2 irradiated surface- fixed platform tilted 37º (local latitude)
Photochemical solar winery wastewater treatment in a CPC reactor
Normalized illumination time (t30W)
t30w,n = t30w,n-1 + Δtn T
i
VVUV
30, Δtn = tn - tn-1
Constant solar UV power of 30 W/m2 (typical solar UV power on a perfectly sunny day around noon).UV is the average solar ultraviolet radiation measured during Δtn.
2.4. Photo-Fenton with solar radiation
31
Simulated winery wastewater performed from:- Wine- Grape juice- Wine + grape juice- Enologic additives
Winery wastewater characteristics
2.4. Photo-Fenton with solar radiation
Effluent Synthetic sample pH Conductivity(S/cm)
TOC(mg C/L)
COD(mg O2/L)
Total polyphenols(mgGallic acid/L)
WV Wine 3.8 152 1155 4440 93
WG Grape juice 4.3 107 1185 4500 112
WWWine + Grape
juice(50:50)
4.1 124 1165 4474 103
32
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-50 0 50 100 150 200 250 300 350 400 450 500 550
0,0
0,2
0,4
0,6
0,8
1,0
TOC
/TO
C0
t30W
■ wine with 55 mg/L Fe2+○ grape juice with 55 mg/L Fe2+▲ wine + grape juice with 55 mg/L Fe2+● wine + grape juice with 20 mg/L Fe2+
For t30W equal to 400 minutes:- wine: reduction of 54% TOC- grape juice: reduction 93% TOC
Wine + grape juice (50:50): - reduction 90% TOC (55 mg/L Fe2+)- reduction 86% TOC (20 mg/L Fe2+)
Solar photo-Fenton system
Photo-Fenton removes 98% of the COD load in the winerywastewater after a t30W of 82 min.
2.4. Photo-Fenton with solar radiation
33
- Toxicity decreases during the photo-Fenton reaction very significantly from 48% to 28%. At the same time,TP decrease 92%, improving wastewater biodegradability.
• Experimental – Physicochemical characterization
(candied fruit wastewater)– UV-A LED photo-Fenton
• H2O2 (mg/L)• Fe3+ (mg/L) • Reaction time (min)
• Radiation source
• pH adjustment to 3;• Iron addition;• H2O2 addition and
simultaneously UV LED ON.
UV LED sytem I96 InGaN Roithner RLS-
UV370E LEDs(23 W/m2) – 370 nm
UV LED sytem II12 InGaN RoithnerAPG2C1-365E LEDS
(70 - 85 W/m2) – 365 nm
2.5. Photo-Fenton with LEDs
2.5. Photo-Fenton with LEDs
LED = Light Emitting Diode
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ParameterValues
Sample A Sample B Sample C
pH (escala Sorensen) 9.78 3.50 6.95
Eo (mV) -140 212 17
Conductivity (µS/cm) 3 820 8 304 8 578
Turbidity (NTU) 410 359 633
Total Suspended Solids
(mg/L)1100 1420 1850
Volatile Suspended Solids
(mg/L)125 265 -
COD (mg O2/L) 22 932 20 902 35 369
BOD5 (mg O2/L) 1 400 3 300 6 600
Toatal Polyphenols
(mg galic acid/L)142 403 384
Biodegradability Index = BOD5/COD
BI < 0.4 Non biodegradable
0.4
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Biological treatment
0.19
0.56
2.5. Photo-Fenton with LEDs
Improvement in the biodegradability index
37
Subsequent biodegradability of treated effluents increased, allowing the application of a biological treatment step after the photochemical/CFD with 85 W/m2.
In this work we presented different case studies involving the Fenton process:
Fenton classic p-HB acid, phenolic acids, OMW Photo-Fenton process RB5, textile wastewater Iron complexes (ferrioxalate) RB5 Photo-Fenton with solar radiation winery wastewater Photo-Fenton with LEDs candied fruit wastewater
Homogeneous Fenton processes are relatively simple, environmentallyfriendly, versatile and economically competitive.
In photo-Fenton processes solar radiation and UV-A LED radiation arealternatives to conventional UV lamps in terms of ecofriendliness, operationalcost and energy efficiency.
3. CONCLUSION
37
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Acknowledgements
• Marco Lucas (U. Loughborough)• Javier Benitez (UEx)• Jesus Beltrán-Heredia (UEx)• Juan Garcia (UCM)• Joaquín Dominguez (UEx)• Sixto Malato (PSA)• Manuel Maldonado (PSA)• Gianluca Li Puma (U. Loughborough)• Jorge Rodriguez-Chueca (U. Rey Juan Carlos)• Pedro Tavares (UTAD)• Rui Boaventura (FEUP)
Thank you very much for your attention
Muchas gracias
Merci bien
Dziękuję
Grazie mille
Muito obrigadoJosé Alcides Peres (UTAD)
Vila Real, Douro region