Implementation of Electro-Fenton technology for environmental remediation:
application for soil and water restoration Marta Pazos and M. Ángeles Sanromán
2nd Summer School on Environmental Applications of AOPsPorto
July 10-14, 2017
• Green Chemistry
• Applied Biotechnology
• Environmental Technology
Research lines
1. Introduction
2. Electro-Fenton for effluent treatment
3. Electro-Fenton for soil remediation
4. Conclusions
Implementation of Electro-Fenton technology for environmental remediation:
application for soil and water restoration
I
EMERGING POLLUTANTS
PESTICIDES
DRUGS PCP
INDUSTRIALADDITIVES
FLAME RETARDANT
IONIC LIQUIDS
FOOD ADDITIVES
SURFACTANTS/ DISINFECTANT
STEROLS/ HORMONES
New chemicals without regulatory status and which impact on environment and human health are poorly understood
·OHFenton based process
I
Environmental problem
TREATMENT REQUIRED
PROBLEM OF GREAT ENVIRONMENTAL IMPACT
Fe2+ + H2O2 → Fe3+ + •OH + HO-
Constant addition of Fe2+
Constant addition of H2O2 Generation of Fe-complexes
Fe-sludge formation
Fenton’s Reaction
CO2 + H2O …
Organic compounds
H+
HYBRID PROCESSES
(1894) Henry John Horstman Fenton
CathodeAnode
Power supply
ElectrochemicalProcess
Fe2+
H2O2
Fe2+H2O2
HO•
FentonProcess
HYBRID PROCESSES
Fe2+
H2O2
Fe2+H2O2
HO•
CathodeAnode
Powersupply
FentonProcess
ElectrochemicalProcess Electro-Fenton
Process
O2 + 2 H+ + 2 e‐ → H2O2Fe3+ + e‐ → Fe2+In situ generation H2O2
Fe2+ regeneration
No Fe-sludge
CathodeAnode
Fe3+
Fe2+
O2
H2O2
Fe2+
Powersupply
Air
HYBRID PROCESSES
Fe-complexes
Fe2+
H2O2
Fe2+H2O2
HO•
CathodeAnode
Powersupply
Cathode Anode
Fe3+
Fe2+
O2
H2O2
Fe2+
Powersupply
Aeration
Photo-electro Fenton
O2 + 2 H+ + 2 e‐ → H2O2Fe3+ + e‐ → Fe2+
H2O2 + hv→ 2 ⦁OHFe3+ + hv→ Fe2+
FentonProcess
ElectrochemicalProcess
Photolysis
HYBRID PROCESSES
In situ generation H2O2Fe2+ regeneration
No Fe-sludge
No Fe-complex
1. Introduction
2. Electro-Fenton for effluent treatment
3. Electro-Fenton for soil remediation
4. Conclusions
Implementation of Electro-Fenton technology for environmental remediation:
application for soil and water restoration
Scarce reactor designs suitable for industrial scaleContinuous treatment of high volumes ( Fe release)
·OHFenton
DRAWBACKS
INDUSTRIALUSE
POA
GOOD RESULTSLAB SCALE
HETEROGENEOUSCATALYST
REACTOR DESIGN
Fe3+Fe2+
O2H2O2
Fe2+
STIRRED TANK REACTOR
REACTOR DESIGN
ActivedCarbon
Nickel
GraphitePTFE
Boron‐DopedDiamond(BDD)
ANODIC MATERIAL
CATHODIC MATERIAL
0
20
40
60
80
100
0 50 100 150 200
Deg
rada
tion (%
)
Time (minutes)
Fe3+Fe3+
Fe2+Fe2+
O2O2
H2O2
Air
+ →OH●Graphite sheet
cathode BDD anodeO2O2
H2O2
Power supply
Fe3+Fe3+
Fe2+Fe2++ →OH●
100 mg/L Pirimicarb82% removal 3h
PESTICIDES
Pirimicarb
GraphiteBDD
ENHANCEMENTSARE NECESSARY
STIRRED TANK REACTOR FLUIDIZED REACTORREACTOR DESIGN
Diez, Sanromán, Pazos (2017) Environ Sci Pollut Res (2017) 24:1137–1151
Graphite+PTFE
PESTICIDESSequential fluidized reactor
New electrodes Graphite-PTFE
UV LED radiation
ENHANCEMENTS
Diez, Sanromán, Pazos (2017) Environ Sci Pollut Res (2017) 24:1137–1151
c
PESTICIDES
Graphite+PTFE
80% removal 1.5 h
98% removal 1.5 h
Huge amount of effluents is generated
Request to design processes that permit their remediation in
continuous mode
H2O2
Fe
HETEROGENEOUSCATALYST
How to avoid Fe release due to the flow system?
Fe
Fe Fe
Fe Fe
Immobilisation on different supports
HETEROGENEOUSCATALYST
Adequate support
Environ‐mentally friendly
Inexpensive
Fe Retention
ALGINATE
SEPIOLITE
KAOLINITE ACRYLAMIDE
ACTIVATEDCARBON
Fe-Alginate
Fe-Sepiolite
Fe entrapment
Fe adsorption
Iglesias, Rosales, Pazos, Sanromán Environ Sci Pollut Res (2013) 20:2252–2261Iglesias, Fernández de Dios, Pazos, Sanromán Environ Sci Pollut Res Int (2013) 20:5983‐93
Homogenous Electro‐Fenton
Heterogeneous Electro‐Fenton
Fe2+
Fe‐AlginateFe‐Sepiolite
Iglesias, Fernández de Dios, Pazos, Sanromán Environ Sci Pollut Res Int (2013) 20:5983‐93Iglesias, Rosales, Pazos, Sanromán Environ Sci Pollut Res (2013) 20:2252–2261
• Fast removal in heterogeneous• Two stage process ads‐degradation
REACTIVE BLACK 5 DYE
REACTIVE BLACK 5 DYE
Homogenous Electro‐Fenton
Heterogeneous Electro‐Fenton
Fe2+
Fe‐AlginateFe‐Sepiolite
No adsorption after the process
Initial Final
Iglesias, Fernández de Dios, Pazos, Sanromán Environ Sci Pollut Res Int (2013) 20:5983‐93Iglesias, Rosales, Pazos, Sanromán Environ Sci Pollut Res (2013) 20:2252–2261
Time(h)
0 20 40 60 80 100 120 140
Dec
olou
risat
ion
(%)
0
20
40
60
80
100
=2.5 h =4 h =12.5 h=6 h
Airlift reactor 1.5 L Graphite electrodes
Reactor design equation
Kinetic model: First orderHydrodynamic model: Stirred flow reactor
Applicability of these catalysts to operate in continuous mode
Iglesias, Rosales, Pazos, Sanromán Environ Sci Pollut Res (2013) 20:2252–2261
1. Introduction
2. Electro-Fenton for effluent treatment
3. Electro-Fenton for soil remediation
4. Conclusions
Implementation of Electro-Fenton technology for environmental remediation:
application for soil and water restoration
Cathode(-)
Anode(+)
V/A+ _
+
+
+ +
+
+
+
++
+
+
+ +
+
+
+
+
+
--
-
--
-
-
-+
+
+
+--
-
+
-
+
+
++
+
+
+
+ +
+
+
++
+
+
+
+
+
--
-
--
-
-
-+
+
+
+ --
-
+
-+
+
+
++
+ +
++
-----
-
-
POSITIVE SPECIES
NEGATIVE SPECIES
ELECTROMIGRATION
The principle of Electro‐Remediation relies upon the application of a low‐intensity direct current through the soil
between a couple of inert electrodes
Cathode(-)
Anode(+)
V/A+ _
ELECTRO-OSMOSIS
IN SITU SOIL REMEDIATION
Transport of charged and uncharged species
to the cathode chamber
+
+-
-
+ +
+
+
+
+
+
--
+
-+
+
+
-Ø
Ø ØØ
ØØ
Ø
Inorganic cations: heavy metals
Inorganic anions: sulphate, nitrates…
VALIDATED
Low solubility
Strongly attached to soil
POOR RESULTS ORGANICS
Electrokinetic remediation
IN SITU degradation by Fenton reagentSOLUTION
Cathode(-)
Anode(+)
V+ _
Fe
FeFe
Fe Fe
Fe
Fe
Fe
Fe
Fe+2 + H2O2 → Fe+3 + OH∙ + OH‐
R + OH∙ → CO2+ H2O
H2O2
H2O2
H2O2
Electrokinetic-Fenton Organic polllutant
• 0.1 M Na2SO4• pH 3• 10 % H2O2
Experimental conditions
Electrodes Graphite bars
Electrochemical Field 30 V
Time 3 days
Fe contaminated clay 3000 ppm
Electrokinetic-Fenton
FLUXING SOLUTION
Popescu, Rosales, …, Pazos, Lazar, Sanromán Process Saf Environ Protec (2017) 108:99‐107
RHODAMINE B DYE
t = 0 d
t = 1.5 d
t = 1 d
t = 2.5 d
• Transportation of the H2O2through the soil
• In situ degradation of pollutant
H2O2
∙OH
∙OH
∙OH
Electro Kinetic cells (EK)
Electrokinetic-Fenton
Popescu, Rosales, …, Pazos, Lazar, Sanromán Process Saf Environ Protec (2017) 108:99‐107
Cathodic chamber
• 0.1 M Na2SO4• pH 3• 10 % H2O2
¿ citric acid ?
Experimental conditions
Electrodes Graphite bars
Electrochemical Field 30 V
Time 27 days
Fe naturally 33594 ppm• Pyrimetanil• Phenanthrene• Anthracene• Fluoranthene• Benzo[a] anthracene• Pyrene
Electrokinetic-Fenton
Bocos, Fernández, Pazos, Sanromán Chemosphere (2015) 125:168‐174
FLUXING SOLUTION
Pollutant
PY PH AN FL PYRE BZ[A]
Deg
rada
tion
(%)
0
20
40
60
80
100
Treatment without complexing agentTreatment with citric acid
Electrokinetic-Fenton
Bocos, Fernández, Pazos, Sanromán Chemosphere (2015) 125:168‐174
50%
80%
GI (%)
0 20 40 60 80 100
Polluted Soil
Decontaminated Soil enhanced by pH control at 5
Commercial substrate
Decontaminated Soil
• Phytotoxicity assays withLolium perenne
Electrokinetic-Fenton
Bocos, Fernández, Pazos, Sanromán Chemosphere (2015) 125:168‐174
GERMINATION INDEX
A
B
C
The electrokinetic phenomenon can be used to produce in situ Fenton reactionThe presence of complexing agents enhances the treatment
Electro-Fenton in soils
The optimization of operational conditions and reactor design are necessaryHeterogeneous catalyst useful for the treatment of continuous flow
Electro-Fenton in aquatic environment
Thank to PhD student Aida DíezPhD student Marius Popespu
Thank to my former studentsPhD BocosPhD IglesiasPhD Rosales
