NO Oxidation and Capture with Wet and Dry Scrubbers

The Science of Persulfate
Activation
Philip Block, PhD
Director of Technology
FMC’s Environmental Solutions Division
Brant Smith, PhD
Sr. Project Manager
XDD
April 24, 2013
Bios
Philip Block is the director of technology for FMC's Environmental
Solutions Division. The Environmental Solutions Division provides
integrated products and solutions in three major focus areas: soil and
groundwater remediation, wastewater and industrial water treatment,
and air pollution. He holds a PhD in physical chemistry and a BS in
Philip Block, Ph.D
chemical engineering.
FMC Environmental Solutions
philip.block@fmc.com
(215) 299-6645
Dr. Smith specializes in water chemistry and hazardous waste
remediation with a particular emphasis on in situ chemical oxidation and
reduction technologies. He is the Director of XDD's treatability laboratory
in Stratham, NH and has over 12 years experience with remedial
technologies. He holds a PhD in civil engineering.
Brant Smith, P.E., Ph.D
XDD, LLC
smith@xdd-llc.com
(603) 778-1100
April 24, 2013
Introduction to
Klozur® Persulfate
• Klozur® Persulfate is a strong oxidant used for in situ and ex
situ destruction of contaminants in soil and groundwater
• Provides the strength of “Fenton’s Chemistry” but with
extended subsurface lifetime (3 – 4 months) and little to no heat
or gas evolution
• Applicable across a broad range of organic contaminants
April 24, 2013
Introduction to
Klozur® Persulfate
Examples of Contaminants Destroyed by Klozur Persulfate
Chlorinated Solvents
PCE, TCE, DCE
TCA, DCA
Vinyl chloride
Carbon tetrachloride
Chloroform
Chloroethane
Chloromethane
Dichloropropane
Trichloropropane
Methylene chloride
TPH
BTEX
GRO
DRO
ORO
creosote
Others
Carbon disulfide
PFOS / PFOA
Aniline
PVA/ TNT / DNT
Freons
April 24, 2013
Oxygenates
MTBE
TBA
Chlorobenzenes
Chlorobenzene
Dichlorobenzene
trichlorobenzene
Phenols
phenol
Pentachlorophenol
nitrophenol
PAHs
Anthracene
Benzopyrene
Styrene
Naphthalene
Pyrene
Chrysene
trimethylbenzene
Pesticides
DDT
Chlordane
Heptachlor
Lindane
Toxaphene
MCPA
Bromoxynil
Chemistry and Stoichiometry
Persulfate Oxidation Principles:
S2O8-2 + 2H+ + 2e-  2HSO4-1
persulfate anion
Examples
15 S2O8-2 + C6H6 + 12 H2O  6 CO2 + 30 HSO4-1
45 lb / lb
benzene
2 S2O8-2 + C2Cl4 + 4 H2O  2 CO2 + 4 Cl- + 4 H+ + 4 HSO4-1
PCE
April 24, 2013
3 lb / lb
Chemistry and Stoichiometry
However, persulfate anion kinetics are generally too slow for most contaminants.
As a result, you must activate persulfate to form the sulfate radical.
Activated Persulfate
produces a radical which is more powerful and kinetically fast
FMC always recommends using an activator
proper activation method is based on contaminant, site lithology, and
hydrogeology
2.6 eV
S2O8-2 + activator  SO4•- + (SO4•- or SO4-2)
Heat
Iron
H2O2
High pH
One of
strongest
oxidants
available.
Purchase of FMC’s Klozur® Persulfate includes rights to practice
the inventions covered by global patents in the purchase price of the product.
April 24, 2013
Presentation Overview
• Activation Methods of Activated Persulfate
– Overview
– Chemistry
– Discussion
• Bench testing activated persulfate
• Case study
– Industrial site with chlorinated ethanes,
ethenes and 1,4-dioxane
April 24, 2013
Activation Methods of Persulfate
• Persulfate is a peroxygen, and similar to hydrogen
peroxide, it can be split at the O-O bond:
-O S-O-O-SO 3
3
 -O3S-O• •O-SO3-
• Reaction is facilitated by activation methods,
which include:
–
–
–
–
–
Reduced metals (Iron and Iron-Chelate)
Alkaline/high pH
Heat
Hydrogen peroxide
Others (photolysis)
8
Iron/Iron Chelate Activation:
Overview
• Sodium persulfate (2.05 V) is activated by the a
reduced iron, Fe(II) is most common, to form the
sulfate radical (SO4•; 2.6 V)
• Has been shown to be reactive with:
–
–
–
–
Reduced organics (PAHs, BTEX, TPH, etc)
Chlorinated ethenes (PCE, TCE, DCE, and VC)
Oxygenates (MTBE, 1,4-Dioxane, etc)
Perfluorinated acids (PFOA, PFBA, etc)
• FMC guidance of 150 mg/L Fe to 600 mg/L Fe
April 24, 2013
Iron/Iron Chelate Activation:
Chemistry
• Iron/Iron Chelate
S2O82- + Fe(II)  Fe(III) + SO4- + SO4•
• Chelate or not to chelate:
– At pH >~2.7 Fe (III) will precipitate
– EDTA, citrate, or other chelates help keep iron in
solution
• How does Fe(III) cycle back to Fe(II)?
– Likely reaction with destabilized organics
April 24, 2013
10
Iron/Iron-Chelate Activation:
Discussion
• Reactivity due to sulfate
radical
• Field application is well
established
• Minimized health and safety
concerns
April 24, 2013
• Does not react with
chlorinated ethanes or
methanes such as 1,1,1TCA or carbon tetrachloride
• Does not typically include
anything to neutralize the
acid that is formed during
the decomposition of
persulfate (more of a
concern as concentrations
increase)
• Formation of halomethanes
has been observed if
halides are present
Alkaline Activation:
Overview
• Sodium persulfate is activated when the solution is raised to pH >
10.5
• Has been shown to be reactive with:
– Reduced organics (PAHs, BTEX, TPH, etc)
– Chlorinated ethenes (PCE, TCE, DCE, and VC)
– Chlorinated methanes or ethanes (CT, 1,1,1-TCA, etc)
– Oxygenates (MTBE, 1,4-Dioxane, etc)
– Perfluorinated acids (PFOA, PFBA, etc)
• Sufficient base needs to be added to account for buffering
capacity of the soil plus the acid that is generated during the
decomposition of sodium persulfate
April 24, 2013
Alkaline Activation:
Chemistry
• Alkaline Activation-simple version:
pH >10.5
S2O82-  2SO4•
• Alkaline Activation-complex version (Furman et al., 2010):
OH-
S2O8
2H2O  HO2- + 2SO42- + 3 H+
HO2- + S2O82-  SO4- + SO42- + H++ O2SO4- + OH-  OH + SO422- +
(note: H2O2  HO2- + H+ pKa = 11.7)
• Complex version of the reaction results in the transient
oxygen species of SO4- , OH , O2- , and HO2• Analogous to the chemistry that has been studied with
catalyzed hydrogen peroxide (CHP)
April 24, 2013
13
Alkaline Activation:
Discussion
• Generates reductive
(O2-), nucleophilic
(HO2-), and oxidative
(SO4-; OH) species
to react with broad
suite of contaminants
• As a result AAP can
treat CT, and 1,1,1TCA
• Ease of
implementation
April 24, 2013
• Health and safety risk
of NaOH or other
base.
• Additional cost of
NaOH
• Typically has
increased non-target
demand from soils
• Site pH following
application
Heat Activation:
Overview
• Heat activated
persulfate used in
certain TOC analyses
• Subsurface heated to
desired temperature
• Persulfate degrades
to form different
compounds as the
temperature
increases
Block et al, 2004
April 24, 2013
Activation with Heat:
Chemistry
• Heat (>35°C sulfate radical; >80°C multiple oxidants)
S2O82-  2SO4•
• Two schools of thought:
– Different oxidants formed at elevated
temperatures
– Kinetics (ie. Arrhenius equation)
April 24, 2013
16
Heat Activation:
Discussion
• Arguably the most
effective activation
method, especially in
the lab setting
• Reacts with wide
variety of compounds
depending upon the
temperature
• Can be used as part of
a combined remedy
with thermal treatments
April 24, 2013
• Soils/silica are good
insulators
• Typically requires dual
system to heat the
subsurface
• Introduces unique
failure mechanisms
such as thermal
sinks/losses/distribution
• Health and safety
associated with heat
source
Hydrogen Peroxide Activation:
Overview
• “Activation”
– Addition of hydrogen peroxide to react with
(donate an electron) sodium persulfate
– Heat
• Combination of two proven ISCO
technologies
• Ratio between the two reagents determines
application characteristics
April 24, 2013
Hydrogen Peroxide Activation:
Catalyzed Hydrogen Peroxide Chemistry
Fundamental Fenton’s reaction (hydroxyl radical)
Fe2+ + H2O2  Fe3+ + OH. + OHPerhydroxyl Radical
OH• + H2O2 HO2• + H2O
Fe3+ + H2O2 HO2• + Fe2+ + H+
Superoxide
HO2• O2•-+ H+ pKa 4.8
OH• + HO2- O2•-+ H2O
Hydroperoxide
April 24, 2013
HO2• + Fe2+  Fe3+ + HO2HO2• + O2•- O2+ HO2-
19
Hydrogen Peroxide Activation:
Chemistry
• Hydrogen peroxide can donate electrons going
to oxygen or accept electrons to become water
e-
e-
2e-
O2  O2  H2O2  H2O
•-
• If hydrogen peroxide is present in sufficient
quantities, the reaction should result in the
transient species of SO4- , OH , O2- , and HO2-
April 24, 2013
Hydrogen Peroxide Activation:
Discussion
• Various reactive
species should allow
for the destruction of
a wide variety of site
COCs
• Thermodynamic
energy could be used
to generate heat
activated persulfate
April 24, 2013
• Design engineers
needs to be
concerned with
overlapping ROIs
• Issues associated
with the application of
hydrogen peroxide
Summary of Activation Methods
Several commonly used activation methods
allows the activation method to be selected by
the design engineer on a site specific basis
– Iron/Iron chelate: Less expensive, effective on
petroleum compounds and chlorinated ethenes
– Alkaline: Effective in treating most chlorinated
and petroleum compounds. Proper alkaline dose
should return site to near neutral pH.
April 24, 2013
Summary of Activation Methods
Continued
– Heat: Effective in treating most chlorinated,
petroleum compounds and perfluorinated
acids. Cost and issues with subsurface
heating need to be addressed.
– Hydrogen peroxide: Effective in treating most
chlorinated and petroleum compounds. May
work via subsurface heating or direct reaction.
Design engineer should evaluate overlap in
subsurface distribution of each oxidant
April 24, 2013
Bench Scale Tests
• Bench Scale Tests can be used to:
– Determine interactions of site specific
geochemistry with the chemistry of activated
persulfate
– Generate critical design parameters
• Choosing to not bench test:
– Field application design will be based on
assumptions or a “standard approach” without the
development of site specific design parameters
– Moves risk to the field
April 24, 2013
Bench Scale Design Parameters
• Each activation method:
– Non-target demand
– Degradation ratio/Persulfate efficiency number
• Additional Design Parameters:
– Iron/Iron chelate
• Iron:chelate loading or ratios
– Alkaline
• Base buffering capacity
– Heat
• Treatment temperature
• Soil heat capacity
– Hydrogen peroxide
• Stability of hydrogen peroxide
April 24, 2013
Case Study:
AAP at an Active Facility
• Key Points
– Closure goal – 1 mg/L for each compound (1,1,1TCA, PCE, 1,4-dioxane)
– Active, high security facility – 3rd shift/evening
applications
– Bench tested iron activated persulfate, alkaline
activated persulfate, ZVI, calcium peroxide, RegenOx
as alternatives.
– Focus on safety - recommended alkaline persulfate
for indoor application
• Eliminate degassing/vapor issues and pressure concerns
April 24, 2013
Site Overview
• Former Vapor Degreaser
• COCs – TCA (101 mg/L), PCE (20 mg/L) and 1,4 Dioxane (3 mg/L)
• Fill underlying concrete floor and overlying sands and
silts – till layer below – high oxidant demand
XDD identified “transition zone”
between upper and lower zones
contained majority of COC
mass
April 24, 2013
Injection Well Layout
• Well Network: 9 shallow and
9 deep 2” PVC injection
wells to 20 feet bgs
April 24, 2013
Operational Overview
• Two injection
events in 2007
• 100 to 200 g/L
Persulfate
• 1st event:
33,000 lbs
persulfate
• 2nd event:
36,000 lbs
persulfate
April 24, 2013
Long Term COC Monitoring Results
Primary ISCO
Primary ISCO
Polish ISCO
Polish ISCO
• 2-3 Orders
Magnitude Reduction
• Target compounds
remain below 1 mg/L
Primary ISCO
Polish ISCO
(3 yrs post application monitoring)
30
April 24, 2013
Long Term Contaminant Monitoring
Primary ISCO
Primary ISCO
Polish ISCO
Polish ISCO
Primary ISCO
Polish ISCO
• 2-3 Orders Magnitude
Reduction
• Target compounds
remain below 1 mg/L
(3 yr post application sampling
round)
April 24, 2013
Metals Mobilization-3 years post
• Monitoring wells in
the source zone
• Data from 3 years
post application
• Metals have
attenuated, typically
in 1 year
April 24, 2013
Downgradient Metals Mobilization
ISCO Area
Downgradient
As still at
Baseline
levels
Downgradient
• As and Cr were not
observed to migrate
downgradient in
events 1 yr and 3 yr
post (shown)
application
Downgradie
nt
ISCO
Area
Cr still at
Baseline
levels
All Concentrations in ug/L
April 24, 2013
Summary
• Several successful methods to activate
sodium persulfate
• Characteristics of each method lend
themselves to site specific engineered
designs
• Activated sodium persulfate is a proven
technology that has been successfully
applied in the field for several years
April 24, 2013
Questions???
Philip Block, Ph.D
FMC Environmental Solutions
philip.block@fmc.com
(215) 299-6645
April 24, 2013
Brant Smith, P.E., Ph.D
XDD, LLC
smith@xdd-llc.com
(603) 778-1100