Note: Descriptions are shown in the official language in which they were submitted.
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REGENERATABLE SYSTEM FOR CONTAMINANT REMOVAL
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. utility application no.
16/904,706, filed June
18, 2020, and U.S. provisional application no. 63/110,952 filed November 6,
2020, the entire
contents of each of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to systems and methods for removing ionic
contaminants
from an aqueous mixture using a capture bed and for regenerating the capture
bed for further use.
BACKGROUND
[0003] This section provides background information related to the present
disclosure and is not
necessarily prior art.
[0004] Water purification technologies are fundamentally important to everyday
life.
Contaminants must be removed to purify water to an acceptable level in order
for the water to be
used as drinking water or for other purposes. Per- and polyfluoroalkyl
substances (PFAS) are of
particular concern and of particular importance to remove from water. Existing
technologies for
water purification by removal of contaminants, including PFAS, suffer from
issues of efficiency
and environmental sustainability. For example, technologies that trap
contaminants, such as
PFAS, in an ion exchange resin or carbon bed currently require replacement of
the bed and
disposal of the spent bed to a landfill.
[0005] Therefore, while there are existing technologies for removing
contaminants such as PFAS
(and other similar polyfluorinated hydrocarbons) from water, a need continues
to exist for
improved technologies that provide more effective removal of contaminants and
that are
regeneratable for continued use without the need for expensive and inefficient
replacement of,
and environmentally harmful disposal of, system components.
SUMMARY OF THE INVENTION
[0006] In one aspect, disclosed herein is a method of removing a contaminant
from an aqueous
mixture. The method includes flowing a contaminated aqueous mixture comprising
one or more
ionic contaminants through a vessel that houses a capture bed and optionally
an electrode in
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electrical contact with the capture bed. The method also optionally includes
applying a voltage
to the electrode that is in electrical contact with the capture bed, such that
the one or more ionic
contaminants is bound to the capture bed. The method further includes flowing
an aqueous wash
liquid through the vessel. The method further optionally includes modulating
the voltage applied
to the electrode, such that the one or more ionic contaminants bound to the
capture bed is
released from the capture bed and is washed from the capture bed via the
aqueous wash liquid.
The aqueous wash liquid may contain a counter ion that binds to the ionic
contaminant forming
an aggregate contaminant phase that can be removed from the aqueous wash
liquid.
[0007] In another aspect, disclosed herein is a system for removing a
contaminant from water.
The system includes a separation vessel and disposed therein a capture bed,
and optionally
further includes: an electrode in electrical contact with the capture bed, and
a power source
electrically coupled to, and configured to apply a voltage to, the electrode
that is in electrical
contact with the capture bed. The system also optionally includes a controller
configured to
control and modulate the voltage applied from the power source to the
electrode. The system
further includes an intake line fluidly coupled to the vessel and configured
to introduce a flow of
a contaminated aqueous mixture to the vessel such that one or more ionic
contaminants in the
contaminated aqueous mixture binds to the capture bed, and a regeneration line
fluidly coupled
to the vessel and configured to introduce a flow of aqueous wash liquid to the
vessel to wash
ionic contaminant from the capture bed.
[0008] In another aspect, disclosed herein is a method of regenerating a
capture bed. The
method includes providing a vessel that houses a capture bed having one or
more ionic
contaminants bound to the capture bed, and optionally an electrode in
electrical contact with the
capture bed, and flowing an aqueous wash liquid through the vessel. The method
optionally
further includes applying a voltage to the electrode, such that the one or
more ionic contaminants
bound to the capture bed is released from the capture bed and is washed from
the capture bed via
the aqueous wash liquid. The aqueous wash liquid may contain a counter ion
that binds to the
ionic contaminant forming an aggregate contaminant phase that can be removed
from the
aqueous wash liquid.
[0009] In another aspect, disclosed herein is a system for regenerating a
capture bed. The system
includes a capture bed housed within a separation vessel, and optionally
further includes: an
electrode in electrical contact with the capture bed and a power source
electrically coupled to,
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and configured to apply a voltage to the electrode. The system also optionally
includes a
controller configured to control and modulate the voltage applied from the
power source to the
electrode. The system further includes a regeneration line fluidly coupled to
the separation
vessel and configured to introduce a flow of aqueous wash liquid to the
separation vessel to wash
ionic contaminant from the capture bed.
[0010] Other features and advantages of the invention will be apparent from
the following
detailed description, figures, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The following figures are provided by way of example and are not
intended to limit the
scope of the claimed invention.
[0012] FIG. 1 is an illustration of a capture system for removing contaminants
from water
according to an embodiment of the invention.
[0013] FIGs. 2A and 2B are a schematic of a capture system (2A) and
regeneration system (2B)
according to another embodiment of the invention.
[0014] FIG. 3 is a process diagram of an integrated capture and regeneration
system according to
another embodiment of the invention.
[0015] FIG. 4 is a flow chart showing the steps of Example 1.
[0016] FIG. 5 shows the visual appearance of the carbon substrate of Example
1.
[0017] FIG. 6 is a chart showing PFNA absorption by a fresh carbon bed from a
mixed
contaminant sample.
[0018] FIG. 7 is a chart showing PFNA absorption by a regenerated carbon bed
from a mixed
contaminant sample.
[0019] FIG. 8 is a chart showing PFOA absorption by a fresh carbon bed from a
mixed
contaminant sample.
[0020] FIG. 9 is a chart showing PFOA absorption by a regenerated carbon bed
from a mixed
contaminant sample.
[0021] FIG. 10 is a chart showing PFOS absorption by a fresh carbon bed from a
mixed
contaminant sample.
[0022] FIG. 11 is a chart showing PFOS absorption by a regenerated carbon bed
from a mixed
contaminant sample.
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[0023] FIG. 12 is a chart showing the concentration of PFOA in filtrate
collected after flow
through a carbon bed in a column.
DETAILED DESCRIPTION
[0024] I. DEFINITIONS
[0025] The terminology used herein is for the purpose of describing particular
exemplary
configurations only and is not intended to be limiting. As used herein, the
singular articles "a,"
"an," and "the" may be intended to include the plural forms as well, unless
the context clearly
indicates otherwise. The terms "comprises," "comprising," "including," and
"having," are
inclusive and therefore specify the presence of features, steps, operations,
elements, and/or
components, but do not preclude the presence or addition of one or more other
features, steps,
operations, elements, components, and/or groups thereof. The method steps,
processes, and
operations described herein are not to be construed as necessarily requiring
their performance in
the particular order discussed or illustrated, unless specifically identified
as an order of
performance. Additional or alternative steps may be employed.
[0026] The terms first, second, third, etc. may be used herein to describe
various elements,
components, regions, layers and/or sections. These elements, components,
regions, layers and/or
sections should not be limited by these terms. These terms may be only used to
distinguish one
element, component, region, layer or section from another region, layer or
section. Terms such
as "first," "second," and other numerical terms do not imply a sequence or
order unless clearly
indicated by the context. Thus, a first element, component, region, layer or
section discussed
below could be termed a second element, component, region, layer or section
without departing
from the teachings of the example configurations.
[0027] The terms, upper, lower, above, beneath, right, left, etc. may be used
herein to describe
the position of various elements with relation to other elements. These terms
represent the
position of elements in an example configuration. However, it will be apparent
to one skilled in
the art that the elements may be rotated in space without departing from the
present disclosure
and thus, these terms should not be used to limit the scope of the present
disclosure.
[0028] As used herein, when an element is referred to as being "on," "engaged
to," "connected
to," "attached to," or "coupled to" another element, it may be directly on,
engaged, connected,
attached, or coupled to the other element, or intervening elements may be
present. In contrast,
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when an element is referred to as being "directly on," "directly engaged to,"
"directly connected
to," "directly attached to," or "directly coupled to" another element, there
may be no intervening
elements or layers present. Other words used to describe the relationship
between elements
should be interpreted in a like fashion (e.g., "between" versus "directly
between," "adjacent"
versus "directly adjacent," etc.). As used herein, the term "and/or" includes
any and all
combinations of one or more of the associated listed items.
[0029] As used herein, the term "electrode" refers to a solid electric
conductor that carries
electric current to another element, such as a capture bed.
[0030] As used herein, the term "activated carbon" refers to a form of carbon
processed to have
small pores that increase the available surface area.
[0031] As used herein "polyfluoroalkyl ion" refers an ionic compound
comprising an alkyl chain
with multiple fluoro substitutions, which is optionally further substituted,
such as with ether,
alcohol, amine (including substituted amine), and carboxylic acid groups.
[0032] "Per- and polyfluoroalkyl substance" or "PFAS" includes but is not
limited to the
following substances: perfluorobutanoic acid, perfluoropentanoic acid,
perfluorohexanoic acid,
perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid,
perfluorodecanoic acid,
perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid,
perfluorotetradecanoic acid, perfluorohexadecanoic acid, perfluorooctadecanoic
acid,
perfluorobutanesulfonic acid, perfluoropentanesulfonic acid,
perfluorohexanesulfonic acid,
perfluorooctanesulfonic acid, perfluorononanesulfonic acid,
perfluorodecanesulfonic acid,
perfluorododecanesulfonic acid, perfluorooctanesulfonamide,
N-methylperfluoro-l-octanesulfonamide, N-ethylperfluoro-l-octanesulfonamide,
1H,1H,2H,2H-perfluorohexanesulfonic acid (4:2), 1H,1H,2H,2H-
perfluorooctanesulfonic acid
(6:2), 1H,1H,2H,2H-perfluorodecanesulfonic acid (8:2),
1H,1H,2H,2H-perfluorododecanesulfonic acid (10:2), N-methyl
perfluorooctanesulfonamidoacetic acid, N-ethyl
perfluorooctanesulfonamidoacetic acid,
2-(N-methylperfluoro-1-octanesulfonamido)-ethanol,
2-(N-ethylperfluoro-1-octanesulfonamido)-ethanol, tetraluoro-2-
(heptafluoropropoxy)propanoic
acid ("GenX"), 4,8-dioxa-3H-perfluorononanoic acid,
11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid, or
9-chlorohexadecafluoro-2-oxanone-1-sulfonic acid. PFAS also includes partial
fluorinations.
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The conjugate bases of these acids are examples of polyfluoroalkyl ions.
Capturing PFAS
includes capturing a conjugate base of a PFAS.
[0033] "PFOS" refers to perfluorooctanesulfonic acid. Capturing/releasing PFOS
includes
capturing/releasing its conjugate base, perfluorooctanesulfonate.
[0034] "PFOA" refers to perfluorooctanoic acid. Capturing/releasing PFOA
includes
capturing/releasing its conjugate base, perfluorooctanoate.
[0035] Systems and methods are described herein. It will be understood that
embodiments of the
invention described with reference to a system may be applicable to the
methods described
herein, and vice versa. For example, from a description of a particular carbon
bed, such as an
activated carbon bed, in a system, it will be understood that the activated
carbon bed may be
used in a method. Likewise, as another example, from a description of
application of a particular
voltage in a method, it will be understood that the system may be configured
to apply the
particular voltage.
[0036] II. SYSTEM FOR REGENERATING A CAPTURE BED
[0037] In one aspect, provided herein is a system for regenerating a capture
bed, or a
"regeneration system." Regenerating refers to removing ionic contaminant from
the capture bed,
i.e., contaminant that was bound to the capture bed during a water
purification process. Systems
and methods for capturing ionic contaminants on a capture bed, and thereby
removing them from
an aqueous mixture are described herein. As more ionic contaminants are bound
to the capture
bed the bed becomes less effective at removing the ionic contaminants.
Eventually, the
contaminants must be released from the capture bed or the capture bed itself
must be replaced.
Regenerating the capture bed in situ by releasing the bound ionic contaminants
allows for
continued use of the capture bed without costly replacement and
environmentally harmful
disposal of the spent capture bed.
[0038] The system for regenerating a capture bed includes a capture bed that
is housed within a
separation vessel. Optionally, the system may be an electrified system with an
electrode in
electrical contact with a capture bed that is housed within a separation
vessel; a power source
electrically coupled to, and configured to apply a voltage to the electrode;
and a controller
configured to control and modulate the voltage applied from the power source
to the electrode.
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By enabling a voltage to be applied to an electrode in electrical
communication with the capture
bed, the regeneration system is able to apply voltage to the capture bed that
drives the release of
ionic contaminant from the capture bed.
[0039] In some embodiments, the electrode comprises graphite, titanium,
stainless steel, cast
iron, a conductive metal oxide, a conductive diamond, a titanium suboxide,
titanium nitride,
titanium carbide, titanium boride, a doped manganese oxide, or mixtures or
composites thereof.
[0040] The system for regenerating a capture bed also includes a regeneration
line fluidly
coupled to the separation vessel and configured to introduce a flow of aqueous
wash liquid to the
separation vessel to wash ionic contaminant from the capture bed. The
application of voltage to
the electrode together with flow of wash liquid to the capture bed via the
regeneration line drives
the release of ionic contaminant from the capture bed, resulting in
regeneration of the capture
bed for further use. In some embodiments, the regeneration line is fluidly
coupled to a
regeneration line pump and/or a regeneration line valve to control the flow of
wash liquid
supplied to the separation vessel. In some embodiments, the regeneration
system includes a flow
controller (e.g., a PLC controller) to control the regeneration line pump
and/or regeneration line
valve.
[0041] In some embodiments, the regeneration system is a sub-system of an
integrated capture
and regeneration system. Such integrated systems are described below.
Integrated systems can
be installed at a site as a stand-alone system for providing purified water.
Alternatively, the
regeneration system may be an add-on system to an existing capture system. For
example, there
are existing systems for water purification with capture beds, e.g., carbon
beds or ion exchange
resin beds; the regeneration systems described herein may be installed as an
add-on system to
provide for in situ regeneration of an existing water purification system. In
some embodiments,
the regeneration system allows for continued use of the capture bed in the
existing system by
release, sequestration, and removal of the ionic contaminants in the capture
bed.
[0042] The following embodiments describe an exemplary installation of an
electrified
regeneration system onto an existing capture system. In order to apply voltage
to an existing
capture system, the electrodes are installed by insertion into the existing
capture bed, and hooked
up to the power source controlled by the controller. A regeneration line is
fitted onto the existing
piping of the capture system (or directly onto the separation vessel) to add
separate inlet and
outlet flow of wash liquid into the separation vessel. Valves, e.g., control
valves, are installed to
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control and switch the source of flow into the separation vessel between (1)
an aqueous mixture
to be purified (during a capture cycle) and (2) a wash liquid to regenerate
the capture bed.
[0043] In some embodiments, the regeneration system includes concentration and
removal of the
ionic contaminant released from the capture bed. In some embodiments, a
contaminant
sequestration agent is employed that can more efficiently be removed from the
system than
removal of the capture bed. In some embodiments, the sequestration agent is
more
environmentally friendly to dispose of than disposal of a spent carbon bed or
spent ion exchange
resin bed (i.e., with bound contaminant).
[0044] In some embodiments, the sequestration agent is a counter ion in the
wash liquid
configured to bind to the ionic contaminant to form an aggregate contaminant
phase. Suitable
sequestration agents and counter ions are described below. In some
embodiments, the system
further includes a filter configured to remove the aggregate contaminant phase
from the wash
liquid. Since the aggregate contaminant phase is sparingly soluble to
insoluble in the water
phase, the precipitate tends to form a distinct solid or liquid phase that is
large enough to either
float or sink or be captured in a particulate filter. In some embodiments, a
skimmer can be used
to capture the aggregate contaminant phase.
[0045] In some embodiments, the regeneration system further comprises a
regeneration vessel
that houses a stationary ion source configured to bind the one or more ionic
contaminants in the
aqueous wash liquid, wherein the regeneration vessel is fluidly coupled to the
separation vessel.
In some embodiments, the stationary ion source comprises lime, e.g., a
plurality of slaked lime
pellets. In some embodiments, the stationary ion source is an alkaline metal
coated surface
where the surface electrostatically or by dispersion forces reversibly holds
the alkaline element
until a contaminant can form a precipitate. The contaminant is held at the
surface until the
surface binding is reversed (e.g., reversing polarity of electrodes).
[0046] In some embodiments, the regeneration system further comprises a
sequestration agent
vessel comprising a sequestration agent in a liquid media. In some
embodiments, the
regeneration system further comprises a mixing tank for mixing the
sequestration agent with the
wash liquid and optionally a settler apparatus for collecting solids
precipitated from the liquid in
the mixing tank. In some embodiments a filter is fluidly coupled to the mixing
tank for filtering
solids from the mixing tank, for example, solids that were not separated in
the settler apparatus.
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[0047] In some embodiments, the aqueous wash liquid comprises untreated
contaminated
aqueous mixture. In some embodiments, the aqueous wash liquid comprises a C1-5
alcohol. In
some embodiments, the aqueous wash liquid further comprises an antifreeze
agent that lowers
the freezing point of the aqueous wash liquid. In some embodiments, the
antifreeze agent is
selected from the group consisting of propylene glycol, polypropylene glycol,
polyethylene
glycol, glycerol, polyvinyl alcohol, carboxymethylcellulose, ribose, sucrose,
glucose, rhamnose,
xylose, fructose, raffinose, stachyose, low molecular weight hydroxyethyl
starches, maltodextrin,
cellodextrins, and any mixture thereof In some embodiments, the aqueous wash
liquid
comprises from about 0.1 wt% to about 20 wt% of the antifreeze agent (e.g.,
about 1 to about 10
wt% of the antifreeze agent). In some embodiments, the freezing point of the
aqueous wash
liquid is below about -0.3 C. In some embodiments, the antifreeze agent
encourages slush
formation of the aqueous wash liquid at freezing temperatures.
[0048] In some embodiments, the aqueous wash liquid further comprises one
or more
additives for cleaning the capture bed of scale and/or inorganic precipitate.
Inorganic precipitate
may comprise, for example, iron or manganese. In some embodiments, the one or
more
additives are selected from the group consisting of acetic acid, propanoic
acid, octanoic acid,
glycolic acid, citric acid, ethylenediaminetetraacetic acid (EDTA), a water-
soluble fatty acid, a
salt of the aforementioned acids (e.g., a sodium or potassium salt), and any
mixture thereof. In
some embodiments, the acid is configured to solubilize inorganic precipitates
or scale on the
capture bed, e.g., at or near the leading edge of the capture bed. In some
embodiments, the pH of
the aqueous wash liquid with the additive(s) is from about 0 to about 6. In
some embodiments,
the pH of the aqueous wash liquid with the additive(s) is from about 3 to
about 6. In some
embodiments, the concentration of the additive(s) in the aqueous wash liquid
is from about 0.1
wt% to about 15 wt%, or up to the limit of solubility of the acid in the wash
liquid.
[0049] In some embodiments, the system further comprises a second wash
liquid that can be
used to rinse the capture bed before, after, or simultaneously with the
aqueous wash liquid; the
second wash liquid may be referred to as a "rinse liquid." The rinse liquid
may be introduced to
the vessel via a rinse liquid line. The rinse liquid is an aqueous liquid
comprising one or more
additives for cleaning the capture bed of scale and/or inorganic precipitate.
In some
embodiments, the one or more additives are selected from the group consisting
of acetic acid,
propanoic acid, octanoic acid, glycolic acid, citric acid,
ethylenediaminetetraacetic acid (EDTA),
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a water-soluble fatty acid, a salt of the aforementioned acids (e.g., a sodium
or potassium salt),
and any mixture thereof. In some embodiments, the pH of the rinse liquid is
from about 3 to
about 6. In some embodiments, the concentration of the additive(s) in the
rinse liquid is from
about 0.1 wt% to about 15 wt%, or up to the limit of solubility of the acid in
the rinse liquid.
[0050] FIG. 2 is a schematic for an exemplary system 200 according to another
embodiment of
the present invention. FIG. 2A shows a capture system 200a in use for
capturing contaminants,
specifically PFOA and/or PFOS, from a water source, which is described in
detail below. FIG.
2B shows a regeneration system 200b. The regeneration system as schematically
shown in FIG.
2B may be part of an integrated capture and regeneration system or may be an
add-on
regeneration system. A regeneration vessel 220 comprising wash liquid
("container of waste
solution") is fluidly coupled via a regeneration line 222 to the separation
vessel 202 that houses
the capture bed, specifically a capture bed stack 204 ("cell stack") and is
configured to flow wash
liquid through the separation vessel 202. A regeneration outlet line 224 is
fluidly coupled to the
opposite end of the separation vessel. A valve 218b controls flow out of the
separation vessel via
the regeneration outlet line 224. The regeneration outlet line 224 is fluidly
coupled to the
regeneration vessel 220 thus completing the circulation loop. The system 200b
is configured to
recirculate the wash liquid through the separation vessel 202 multiple times
resulting in a wash
liquid with high concentration of contaminant (e.g., PFOA/PFOS). The
regeneration vessel 220
contains a stationary ion source 226, which are slaked lime pellets as shown
in this embodiment.
The slaked lime pellets 226 are configured to bind to the PFOA/PFOS in the
regeneration vessel
220. Slaked lime pellets 226 can easily be removed from the system for
disposal. Disposal of
slaked lime pellets is more economical and environmentally friendly than
disposal of an
activated carbon bed or ion exchange resin bed.
[0051] III. METHOD FOR REGENERATING A CAPTURE BED
[0052] Another aspect provided herein is a method for regenerating a capture
bed, or a
"regeneration method." The method of regenerating a capture bed includes
providing a vessel
that houses a capture bed having one or more ionic contaminants bound to the
capture bed, and
optionally an electrode in electrical contact with the capture bed. The vessel
may be part of an
integrated capture and regeneration system that includes a system for
capturing a contaminant, as
described below. Alternatively, the vessel may be part of an existing
contaminant capture
system (water purification system), wherein the regeneration method is
performed on the
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existing vessel/capture system by installing a regeneration system (as
described above) onto the
existing vessel/capture system.
[0053] The method of regenerating a capture bed further includes flowing an
aqueous wash
liquid through the vessel and optionally applying a voltage to the electrode,
such that the one or
more ionic contaminants bound to the capture bed is released from the capture
bed and washed
from the bed via the aqueous wash liquid.
[0054] In some embodiments, the aqueous wash liquid is flowed into the
separation vessel at a
rate of from about 5 to about 400 liters per minute per square meter of
capture bed to release
bound ionic contaminant from the capture bed and wash the release ionic
contaminant out of the
capture bed.
[0055] In some embodiments, a voltage is applied to the electrode. In some
embodiments, a
voltage having a positive polarity of from about 0.01 V to about 1.5 V (e.g.,
about 0.01 V to
about 1.2 V) is applied to the electrode in order to drive the release of the
ionic contaminant from
the capture bed to be washed away by the wash liquid. In some embodiments, a
voltage having a
negative polarity of from about -0.01 V to about -1.6 V is applied to the
electrode in order to
drive the release of the ionic contaminant. In some embodiments, an AC voltage
is applied,
optionally with a DC offset, to drive release of the ionic contaminant. In
some embodiments, no
voltage is applied.
[0056] In some embodiments, the wash liquid comprises a sequestration agent.
In some
embodiments, the sequestration agent is a counter ion. In some embodiments,
the counter ion is
a cation selected from Ca', Mg', Zn', Sr', Al', B", Al', or Fe'. Cations are
suitable for
use in regenerating a capture bed with a bound anionic contaminant, such as
perfluoroalkyl
anions, or phosphate or borate contaminants. In some embodiments, the counter
ion is Ca2+. In
some embodiments, the counter ion is Al'. In some embodiments, the counter ion
is supplied to
the wash liquid by addition of calcium hydroxide, calcium oxide, or calcium
chloride to the wash
liquid. In some embodiments, the wash liquid is basic and the source of Ca2+
is calcium
hydroxide. In some embodiments, the wash liquid is acidic and the source of
Ca2+ is calcium
chloride. In some embodiments, the counter ion is supplied to the wash liquid
by addition of
aluminum hydroxide. In some embodiments, the counter ion is supplied to the
wash liquid by
addition of a mixture of aluminum hydroxide and sodium hydroxide. In some
embodiments, the
counter ion is supplied to the wash liquid by addition of NaAl(OH)4 sodium
aluminate.
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[0057] In some embodiments, the pH of the aqueous wash liquid is modulated to
cause the
aggregate contaminant phase to precipitate from the aqueous wash liquid. For
example, lime or
other hydroxide can be added to the aqueous wash liquid to change the pH.
Sodium hydroxide,
carbon dioxide, bicarbonate, phosphoric acid, and sulfuric acid may also be
used as pH
modulating agents. In some embodiments, the pH is modulated distal to (i.e.,
downstream of)
the capture bed. pH modulation may be accomplished with a lime wash of the
column by
bubbling carbon dioxide or adding bicarbonate in another tank upstream of the
capture bed; this
lowers the pH from the Ca(OH)2 solution to a neutral or near neutral pH and
improves the
aggregate size of the precipitate by co-precipitating calcium carbonate with
the perfluoroalkyl
compounds. Alternatively, phosphoric acid and sulfuric acid may also be
introduced to form
salts with calcium and act as neutralizing agents. In some embodiments, the
wash liquid
comprises sodium hydroxide.
[0058] In some embodiments, the counter ion is an anion selected from a
phosphate, a sulfate, or
a borate. Anions are suitable for use in regenerating a capture bed with a
bound cationic
contaminant, such as perfluoroalkyl cations. In some embodiments the counter
ion is supplied to
the wash liquid by addition of calcium phosphate, calcium borate, calcium
sulphate, magnesium
phosphate, magnesium borate, or magnesium sulphate to the wash liquid.
[0059] In some cases, perfluoroalkyl compounds may be nonionic and must first
be partially
decomposed before they can be released using the counter ion. In such
instances, the
regeneration method further comprises partially decomposing the nonionic
perfluoroalkyl
compound(s), such as by chemical, photochemical, electrochemical decomposition
or by
application of DC or AC electrical discharge.
[0060] In some embodiments, upon flowing the wash liquid comprising the
sequestration agent
through the separation vessel, the sequestration agent and the released ionic
contaminant form an
aggregate contaminant phase. In some embodiments, the aggregate contaminant
phase separates
from the aqueous wash liquid by precipitation. In other embodiments, the
aggregate contaminant
phase forms a foam. In other embodiments, the aggregate contaminant phase
forms a dispersed
phase within the aqueous wash liquid.
[0061] In some embodiments, the aqueous wash liquid is at least substantially
saturated with the
ionic contaminant upon exiting the capture bed.
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[0062] In some embodiments, the regeneration method comprises adding a
sequestration agent to
the wash liquid. In some embodiments, a sequestration agent vessel is provided
containing the
sequestration agent in liquid media (e.g., aqueous media) and the
sequestration agent is flowed
from the sequestration agent vessel to be added to the wash liquid. The flow
may be controlled
by a pump and/or valve. In some embodiments, the sequestration agent is mixed
with the wash
liquid, for example in a mixing tank. In some embodiments, the wash liquid
mixed with the
sequestration agent is wash liquid that is substantially saturated with the
ionic contaminant.
[0063] In some embodiments, a rinse liquid comprising additive(s), as
described above, is
flowed through the vessel and the capture bed. The rinse liquid may be used
before, after, or
simultaneously with the aqueous wash liquid. In some embodiments, the method
further
comprises removing, and optionally solubilizing, inorganic precipitates or
scale on the capture
bed, e.g., at or near the leading edge of the capture bed.
[0064] In some embodiments, the regeneration method further comprises
contacting the released
ionic contaminant in the aqueous wash liquid with a stationary ion source,
such that the ionic
contaminant is bound to the stationary ion source forming an aggregate
contaminant phase.
[0065] In some embodiments, the regeneration method further comprises removal
of the
aggregate contaminant phase. In some embodiments, removal of the aggregate
contaminant
phase comprises filtering the aggregate contaminant phase from the wash
liquid.
[0066] In some embodiments, the regeneration method further comprises disposal
of the
removed aggregate contaminant phase, e.g., to a landfill. The aggregate
contaminant phase may
also be destroyed, e.g., by calcination, thermal decomposition, or
vitrification. In some
embodiments, the regeneration method further comprises electrochemical
oxidation of the wash
liquid.
[0067] In some embodiments, the regeneration method further comprises pre-
oxidizing the ionic
contaminant comprising converting alcohol groups of the ionic contaminant to
carboxylic acid
groups by chemical or electrochemical means.
[0068] In some embodiments, the ionic contaminant comprises an organic end
with an ionic
moiety. In some embodiments, the ionic contaminant is selected from the group
consisting of a
polyfluoroalkyl ion, a borate, a phosphate, a polyphosphate, a sulfate, an
organic acid, a fatty
acid, a humic substance, a shortchain PFAS, a water-soluble medication, a
detergent, a water-
soluble insecticide, a water-soluble fungicide, a water-soluble germicide, and
any combination
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thereof. In some embodiments, the ionic contaminant is a polyfluoroalkyl ion.
In some
embodiments, the polyfluoroalkyl ion is perfluorooctanesulfonate or
perfluorooctanoate.
Perfluorooctanesulfonate is the conjugate base of perfluorooctanesulfonic acid
(PFOS).
Perfluorooctanoate is the conjugate base of perfluorooctanoic acid (PFOA). In
some
embodiments, the polyfluoroalkyl ion is perfluorobutanesulfonate or
perfluorobutanoate.
Perfluorobutanesulfonate is the conjugate base of perfluorobutanesulfonic acid
(PFBS).
Perfluorobutanoate is the conjugate base of perfluorobutanoic acid (PFBA).
[0069] The system of FIG. 2B can also be described in terms of a regeneration
method of which
it illustrates. Wash liquid ("waste solution") is flowed to a separation
vessel that houses a
capture bed ("cell stack") and flows through the vessel. Ionic contaminants
bound to the cell
stack are released as wash liquid flows through the vessel and voltage is
applied (not shown) to
the cell stack. A valve ("waste water valve") is opened to direct flow of wash
liquid with
released ionic contaminant (PFOA and/or PFOS) to a regeneration vessel
("container of waste
solution") via a regeneration outlet line. A stationary ion source (slaked
lime pellets in this
embodiment) binds the PFOA/PFOS. The slaked lime pellets with bound PFOA/PFOS
can be
removed from the system and disposed of.
[0070] IV. SYSTEM FOR CAPTURING A CONTAMINANT
[0071] Another aspect provided herein is a system for capturing an ionic
contaminant, or a
"capture system." The capture system includes a separation vessel that houses
a capture bed
configured to capture ionic contaminants in an aqueous mixture flowed through
the separation
vessel. In some embodiments, the system also provides for regeneration of the
capture bed as an
integrated capture and regeneration system, or an "integrated system." The
integrated system
may include any of the features of a regeneration system and/or capture system
as described
herein.
[0072] The capture system includes: a separation vessel and disposed therein a
capture bed; and
an intake line fluidly coupled to the vessel and configured to introduce a
flow of a contaminated
aqueous mixture to the vessel such that one or more ionic contaminants in the
contaminated
aqueous mixture binds to the capture bed; and optionally further includes an
electrode in
electrical contact with the capture bed, a power source electrically coupled
to, and configured to
apply a voltage to, the electrode that is in electrical contact with the
capture bed, and a controller
configured to control and modulate the voltage applied from the power source
to the electrode.
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[0073] The integrated capture and regeneration system includes a capture
system and further
includes a regeneration line fluidly coupled to the vessel and configured to
introduce a flow of
aqueous wash liquid to the vessel to wash ionic contaminant from the capture
bed.
[0074] In some embodiments, the capture system further includes a pump fluidly
coupled to the
intake line and configured to pump the contaminated aqueous mixture into the
separation vessel.
In some embodiments, the capture system further includes a valve fluidly
coupled to the intake
line and configured to control the flow of the contaminated aqueous mixture
into the separation
vessel.
[0075] In some embodiments, the system is a non-electrified system.
[0076] In some embodiments, the system is an electrified system with an
electrode, power
source, and controller as described herein. In some embodiments, the
controller is configured to
reduce or reverse the current applied from the power source. In some
embodiments, the
controller is further configured to reduce the voltage applied to the
electrode, reverse the polarity
of the voltage applied to the electrode, terminate the voltage applied to the
electrode, or any
combination thereof As described in the methods below, the power source is
configured to
apply a first voltage to the electrode during flow of contaminated aqueous
mixture to capture bed
(during a capture cycle). During flow of wash liquid to the capture bed
(during a regeneration
cycle), terminating, reducing or reversing the current helps to drive the
release of the bound
contaminant from the capture bed.
[0077] In some embodiments, the capture bed (e.g., activated carbon bed) is
surface-modified
with functional groups selected from the group consisting of an acid, a
hydroxide, a chloride, a
bromide, a fluoride, an ether, an epoxide, a quinone, a ketone, an aldehyde, a
pyrrole, a
thiophene, and any combination thereof.
[0078] In some embodiments, the capture bed is at least partially conductive.
In some
embodiments, the capture bed is porous. In some embodiments, the capture bed
is an activated
carbon bed. In some embodiments, the capture bed is an ion exchange resin bed.
In some
embodiments, the capture bed is a composite of activated carbon and ion
exchange resin. In
some embodiments, the capture bed is an activated carbon metal oxide
composite. In some
embodiments, the capture bed is a FILTRASORB activated carbon bed from Calgon
Carbon.
In some embodiments, the capture bed comprises black pearls 200 (activated
graphite) from
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Cabot corporation. In some embodiments, the capture bed comprises PBX51
(activated graphite)
from Cabot corporation.
[0079] In some embodiments, the capture bed comprises powder, granules, beads,
pellets, cloths,
felts, nonwoven fabrics, or composites comprising a material selected from
carbon, nitrogen-
doped carbon, boron-doped carbon, charcoal, graphite, biochar, coke, carbon
black, or any
combination thereof In some embodiments, the capture bed comprises activated
charcoal
powder, granules, pellets, beads, or any combination thereof
[0080] In some embodiments, the capture bed comprises activated carbon having
an average
surface area of from about 100 m2/g to about 2000 m2/g. In some embodiments,
the capture bed
has a conductivity of from about 0.01 S/cm to about 100 S/cm. In some
embodiments, the
capture bed has a porosity of from about 30% to about 95%.
[0081] In some embodiments, the capture bed is surface-modified with
functional groups
selected from the group consisting of an acid, a hydroxide, a chloride, a
bromide, a fluoride, an
ether, an epoxide, a quinone, a ketone, an aldehyde, a pyrrole, a thiophene,
and any combination
thereof. In some embodiments, the capture bed has an ionic complexing species
bound to it. In
some embodiments, the ionic complexing species is Ca', Mg', Al', phosphate,
borate, or
silicate. In some embodiments, the ionic complexing species is an alkaline ion
mixed with fatty
acid or wax.
[0082] In some embodiments, the capture bed further comprises a binder
dispersed in the capture
bed. In some embodiments, the binder comprises a wax, a starch, a sugar, a
polysaccharide, or
any combination thereof In some embodiments, the wax is a polyethylene wax. In
some
embodiments, the wax is carnauba wax.
[0083] In some embodiments, the capture bed is disposed longitudinally along
the flow axis of
the separation vessel such that the contaminated aqueous mixture flows by the
capture bed. In
other embodiments, the capture bed is disposed laterally across the separation
vessel such that
the water flows through the capture bed.
[0084] In some embodiments, the capture bed is adjacent to a separator. In
some embodiments,
the capture bed is wrapped in a separator, enclosed within a separator, or
sandwiched between
two separators.
[0085] In some embodiments, the capture system further comprises a second
separation vessel
that houses a second capture bed and a second electrode in electrical contact
with the second
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capture bed. In some embodiments, the power source or a second power source is
configured to
apply a voltage to the second electrode that is in electrical contact with the
second capture bed.
[0086] In some embodiments, the separation vessel further houses a second
capture bed and a
second electrode in electrical contact with the second capture bed. In some
embodiments, the
second capture bed is adjacent to the first capture bed with a separator
disposed between the first
and second capture beds. In some embodiments, the separator is disposed around
the first and
second capture beds in a Z-fold, S-fold, or C-fold arrangement. In some
embodiments, the
separator is disposed around one or more capture beds in a spiral wound or
jelly roll
configuration. In some embodiments, the power source is configured to apply a
positive voltage
to one of the first and second capture beds, and a negative voltage to the
other of the first and
second capture beds.
[0087] In some embodiments, the separation vessel comprises a stack comprising
a plurality of
capture beds. In some embodiments, the plurality of capture beds in the stack
are separated from
each other by one or more separators. In some embodiments, the plurality of
capture beds are in
electrical contact with the first or second electrode.
[0088] In some embodiments, the power source is configured to apply a positive
voltage to the
first electrode, wherein the first electrode is in electrical contact with a
first plurality of capture
beds, and wherein the power source is configured to apply a negative voltage
to the second
electrode, wherein the second electrode is in electrical contact with a second
plurality of capture
beds.
[0089] In some embodiments, the first plurality of capture beds are stacked in
an alternating
fashion with the second plurality of capture beds.
[0090] In some embodiments, the vessel is a pipe, column, or tank.
[0091] In some embodiments, the separator comprises a porous plastic. In some
embodiments,
the porous plastic is a plastic mesh. In some embodiments, the separator
comprises an inert
material. Suitable materials for the separator include nylon, polyamide,
polypropylene, and
HDPE.
[0092] FIG. 1 illustrates an exemplary capture system according to an
embodiment of the present
invention. In this embodiment, a separation vessel or column 102 (e.g., PVC
pipe) houses a
stack 104 of carbon powder capture beds 104a-d. The stack 104 is arranged with
each carbon
powder capture bed 104a-d wrapped in a non-woven separator 106a-d. Stacks can
be added, and
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the column 102 lengthened, to fit the desired amount of carbon. The stack 104
is configured
with the wrapped carbon power capture beds 104a-d disposed laterally across
the vessel 102 such
that flow through the vessel 102 will flow through each capture bed 104a-d of
the stack 104.
Electrodes 108 (or "current collectors") made of graphite filled polymer are
in electrical contact
with the carbon powder capture beds 104a-d. The electrodes 108 are
electrically coupled to a
power source 150 A first electrode 108a is inserted longitudinally through the
stack 104 and is in
electrical contact with a first 104a and third 104c capture bed of the stack,
but is electrically
insulated from a second 104b and fourth 104d capture bed of the stack. Non-
conductive tape
110 is wrapped around a portion of the first electrode 108a in its
electrically insulated areas in
the second and fourth capture bed. A second electrode 108b is inserted
longitudinally (and
separated from the first electrode 108a) through the stack 104 and is in
electrical contact with the
second 104b and fourth 104d capture bed of the stack, but is electrically
insulated from the first
104a and third 104c capture bed. Non-conductive tape 110 is wrapped around a
portion of the
second electrode 108b in its electrically insulated areas in the first 104a
and third 104c capture
bed. An intake line 112 is fluidly coupled to a first end of the separation
vessel 102 and an outlet
line 116 is fluidly coupled to a second end of the separation vessel 102. The
inlet line 112
includes an inlet valve 114. The outlet line 116 includes an outlet valve 118.
[0093] FIG. 2 is a schematic for exemplary system 200 according to another
embodiment of the
present invention. FIG. 2A shows a capture system 200a in use for capturing
contaminants,
specifically PFOA or PFOS, from a water source. An intake line 212 is fluidly
coupled to a
vessel 202 that houses a cell stack 204 and configured to supply water in need
of treatment due
to high concentration of PFOA and/or PFOS (e.g., having levels PFOA and/or
PFOS above the
upper limit as defined by EPA or other regulatory body) into the vessel 202.
The cell stack 204
comprises capture beds in a stack, optionally with separator between the beds.
An outlet has
valves 218a, 218b for a clean water outlet and a waste water (i.e. wash
liquid) outlet. FIG. 2B
shows a regeneration system 200b as described above. The regeneration system
of FIG. 2B may
be installed together with the system of FIG. 2A as part of an integrated
system.
[0094] FIG. 3 is a process diagram for an exemplary integrated system 300
according to another
embodiment of the present invention. In this embodiment, a raw water tank 308
contains the
contaminated aqueous mixture in need of ionic contaminant removal. The raw
water tank 308 is
fluidly coupled to a pump 314 ("pump 1") with an intervening valve 312 to
control flow. Pump
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1 314 is fluidly coupled to the inlet 316 of a separation vessel 302 (e.g., an
activated carbon EDT
filtration column) that houses activated carbon capture beds 304. A
voltage/current source 306 is
electrically coupled to the capture beds 304 of the separation vessel 302. The
outlet 318 of the
column 302 is fluidly coupled to a clean water tank 324 with an intervening
valve 322. The
intervening valve 322 is also fluidly coupled to the raw water tank 308 via
recirculation line 326
providing for optional recirculation of the liquid for one or more additional
cycles of
contaminant removal. The raw water tank 308 is also fluidly coupled to another
pump 330
("pump 2") via the same intervening valve 312 that controls flow into pump 1
314. Pump 2 330
is fluidly coupled to a second separation vessel 332 (an activated graphite
EDT concentrating
column) that houses an activated graphite capture bed 334. A voltage/current
336 source is
electrically coupled to the activated graphite bed 334. The second separation
vessel 332 is
fluidly coupled to the clean water tank 308 and to the recirculation valve
322.
[0095] Still referring to FIG. 3, a regeneration vessel 328 (waste water tank)
containing wash
liquid is fluidly coupled to both Pump 1 314 and Pump 2 330 and both
separation vessels 302,
332. The wash liquid upon flowing through the capture beds 304 and/or 334 can
be referred to
as extract and is fluidly coupled to a precipitator 338. The precipitator 338
is also fluidly
coupled to a regeneration fluid tank 340 via another pump 342 ("Pump 3"). The
regeneration
fluid tank 340 contains a counter ion in a liquid media. The precipitator 338
is fluidly coupled to
a settler 344 for removing precipitated solids from the extract upon mixing
with the counter ion.
The settler 344 is also fluidly coupled to a filter 346 for further removal of
solids from the liquid
phase exiting the settler. The system 300 can be controlled by a PLC
controller 348.
[0096] V. METHOD FOR CAPTURING A CONTAMINANT
[0097] Another aspect provided herein is a method for capturing an ionic
contaminant, or a
"capture method." The capture method includes flowing an aqueous mixture
comprising one or
more ionic contaminants through a separation vessel that houses a capture bed
in order to bind
the one or more ionic contaminants to the capture bed, thereby removing the
one or more ionic
contaminants from the aqueous mixture. In some embodiments, the method
includes
regeneration of the capture bed as part of an integrated capture and
regeneration method, or an
"integrated method."
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[0098] In some embodiments, the capture method further includes applying a
voltage to the
electrode that is in electrical contact with the capture bed, such that the
one or more ionic
contaminants is bound to the capture bed. The applied voltage enhances the
binding of the one
or more ionic contaminants to the capture bed. Methods with application of
voltage are referred
to as electrified methods.
[0099] The integrated method further includes a regeneration cycle comprising
flowing an
aqueous wash liquid through the separation vessel and optionally, in
electrified methods,
modulating the voltage applied to the electrode, such that the one or more
ionic contaminants
bound to the capture bed is released from the capture bed and is washed from
the capture bed via
the aqueous wash liquid. The modulated voltage helps to drive the release of
the bound ionic
contaminant from the capture bed. The integrated method, specifically the
regeneration cycle
thereof, may include any of the steps and features of the regeneration method
described above.
[00100] In some embodiments, applying the voltage to the electrode
comprises running an
electrical current to the electrode, and modulating the voltage comprises
reducing or reversing
the electrical current running to the electrode. In some embodiments, the
voltage applied to the
electrode during capture of contaminants has a positive polarity from about
0.01 V to about
2.2 V. In some embodiments, the voltage applied to the electrode during
capture of
contaminants has a positive polarity from about 0.01 V to about 1.6 V. In some
embodiments,
modulating the voltage to release the ionic contaminant comprises reducing the
electric current
to generate a modulated voltage having a positive polarity of from about 0.01
V to about 1.5 V
(e.g., about 0.01 V to about 1.2 V). In some embodiments, modulating the
voltage to release the
ionic contaminant comprises reversing the electric current to generate a
modulated voltage
having a negative polarity of from about -0.01 V to about -2.2V or from about -
0.01 V to about -
1.6 V. In some embodiments, modulating the voltage to release the ionic
contaminant comprises
applying an AC voltage optionally with a DC offset.
[00101] In some embodiments, the contaminated aqueous mixture is flowed
into the vessel
at a rate from about 5 to about 400 liters per minute per square meter of
capture bed. In some
embodiments, the contaminated aqueous mixture is flowed into the vessel at a
rate from about 80
to about 240 liters per minute per square meter of capture bed. In some
embodiments, the
contaminated aqueous mixture is flowed into the vessel at a rate from about
0.01 to about
liters per minute per kilogram of capture bed. In some embodiments, the
capture bed has a
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mass of from about 4,000 to about 10,000 kilograms. In some embodiments, the
pressure drop
across the capture bed is from about 1 psi to about 200 psi.
[00102] In some embodiments, the aqueous wash liquid is flowed into the
vessel at a rate
from about 5 to about 400 liters per minute per square meter of capture bed.
In some
embodiments, the aqueous wash liquid is flowed into the vessel at a rate from
about 80 to about
240 liters per minute per square meter of capture bed. In some embodiments,
the aqueous wash
liquid is flowed into the vessel at a rate from about 0.01 to about 10 liters
per minute per
kilogram of capture bed.
[00103] In some embodiments, the capture method further comprises binding
an ionic
complexing species to the capture bed prior to flowing the contaminated
aqueous mixture
through the vessel, such that upon flowing the contaminated aqueous mixture
through the vessel,
the ionic contaminant binds to the capture bed by forming a complex with the
ionic complexing
species wherein the complex is bound to the capture bed. In some embodiments,
the ionic
complexing species is Ca', Mg', phosphate, borate, or silicate. In some
embodiments, the ionic
complexing species is an alkaline ion mixed with fatty acid or wax.
[00104] In some embodiments, the capture bed is situated in the vessel
such that the
contaminated aqueous mixture flows by the capture bed. In some embodiments,
the capture bed
is situated in the vessel such that the contaminated aqueous mixture flows
through the capture
bed.
[00105] In some embodiments, the capture method further includes flowing
the
contaminated aqueous mixture through a second vessel that houses a second
capture bed and a
second electrode in electrical contact with the second capture bed and
applying a voltage to the
second electrode that is in electrical contact with the second capture bed.
[00106] In some embodiments, the vessel further houses a second capture
bed and a
second electrode in electrical contact with the second capture bed and the
capture method further
includes applying a voltage to the second electrode that is in electrical
contact with the second
capture bed. In some embodiments, the second capture bed is adjacent to the
first capture bed
with a separator disposed between the first and second capture beds. In some
embodiments, a
positive voltage is applied to one of the first and second capture beds, and a
negative voltage is
applied to the other of the first and second capture beds.
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[00107] In some embodiments, the vessel comprises a capture bed stack
comprising a
plurality of capture beds. In some embodiments, the plurality of capture beds
are separated from
each other by one or more separators. In some embodiments, the plurality of
capture beds are in
electrical contact with the first or second electrode. In some embodiments,
the capture method
further comprises applying a positive voltage to the first electrode, wherein
the first electrode is
in electrical contact with a first plurality of capture beds; and applying a
negative voltage to the
second electrode, wherein the second electrode is in electrical contact with a
second plurality of
capture beds. In some embodiments, the first plurality of capture beds are
stacked in an
alternating fashion with the second plurality of capture beds.
[00108] In some embodiments, the capture method further comprises surface-
modifying
the capture bed with a functional group selected from the group consisting of
an acid, a
hydroxide, a chloride, a bromide, a fluoride, an ether, an epoxide, a quinone,
a ketone, an
aldehyde, a pyrrole, a thiophene, and any combination thereof
[0100] In some embodiments, the ionic contaminant comprises an organic end
with an ionic
moiety. In some embodiments, the ionic contaminant is selected from the group
consisting of a
polyfluoroalkyl ion, a borate, a phosphate, a polyphosphate, a sulfate, an
organic acid, a fatty
acid, a humic substance, a shortchain PFAS, a water-soluble medication, a
detergent, a water-
soluble insecticide, a water-soluble fungicide, a water-soluble germicide, and
any combination
thereof. In some embodiments, the ionic contaminant is a polyfluoroalkyl ion.
In some
embodiments, the polyfluoroalkyl ion is perfluorooctanesulfonate or
perfluorooctanoate.
[0101] In some embodiments, the contaminated aqueous mixture further comprises
inorganic
contaminants. In some embodiments, the inorganic contaminants include iron or
manganese. In
some embodiments, the inorganic contaminants in the contaminated aqueous
mixture result in
scale formation or inorganic precipitate formation on the capture bed; the
scale or inorganic
precipitate can be removed by the use of one or more additives in the wash
liquid or in a separate
rinse liquid. In some embodiments, the use of the additive(s) reduces the
amount of time needed
to regenerate the capture bed and/or reduces the volume of wash liquid needed
to regenerate the
capture bed.
[0102] The system of FIG. 2A can also be described in terms of a capture
method of which it
illustrates. Water comprising a high concentration of PFOA and/or PFOS
contaminant is flowed
into a separation vessel that houses a plurality of capture beds in a stack
("cell stack"). As the
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water flows through the cell stack the PFOA and/or PFOS ionic contaminant is
bound to the
capture bed. With the bound contaminant removed from the flow of water through
the
separation vessel, water with a low concentration of PFOA and/or PFOS flows
out of the
separation vessel via an outlet line. Flow through the outlet line is
controlled by a valve, which
is open during the capture cycle ("system in use"). A second outlet line for
use during a
regeneration cycle is closed.
[0103] The system of FIG. 3 can also be described in terms of an integrated
capture and
regeneration method. During a capture cycle of the integrated method,
contaminated water from
the raw water tank flows into the two separation vessels (activated carbon EDT
filtration column
and activated graphite EDT concentrating column). This flow is controlled by a
valve and a
pump for each separation vessel as shown. Voltage is applied to the capture
beds in each
separation vessel. The water with contaminant removed by the capture beds is
flowed to a clean
water tank, which flow is controlled by further valves. Optionally the outlet
flow of the
separation vessels may be recirculated, as controlled by a recirculation
valve, to the raw water
tank for additional cycle(s) of purification.
[0104] Still referring to FIG. 3, during a regeneration cycle, wash liquid
from a waste water tank
is flowed through the separation vessels and also controlled using the same
valves and pumps as
during the capture cycle. The voltage is modulated during the regeneration
cycle to drive release
of the bound contaminant from the capture bed as the wash liquid flows through
the separation
vessel. The wash liquid with released contaminant ("extract") is flowed to a
precipitator where it
is mixed with regeneration fluid that is pumped into the precipitator. The
regeneration fluid
comprises a sequestration agent (e.g., a counter ion) that forms an aggregate
contaminant phase
with the released contaminant. The aggregate contaminant phase precipitates
from the wash
liquid in the precipitator and the solids are collected in a settler and
removed. Wash liquid
exiting the precipitator/settler is filtered and returned for continued use in
washing the capture
beds.
[0105] VI. EXAMPLES
[0106] Example 1: Regeneration of Carbon Substrate
[0107] An experiment was carried out to test the regeneration of carbon
substrate using calcium
hydroxide and calcium chloride. The experiment tested the capture,
regeneration, and
sequestration of (i) octanoic acid and (ii) PFOA on carbon substrate using
calcium hydroxide or
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calcium chloride as sequestration agent. Octanoic acid is a simulant of PFAS,
which has similar
behavior in water but not the disposal issues of actual PFAS. Visual
indications and mass
measurements were used to determine the results of the experiment.
[0108] FIG. 4 shows a flowchart of the testing method. A first carbon
substrate was selected,
either granulated activated carbon (GAC) or St Mary's carbon beads. The dry
mass of the
substrate was recorded. The substrate was next soaked in water and the wet
mass mas recorded.
The substrate was then dried in an oven and the mass after drying recorded.
The substrate was
next soaked in water followed by soaking overnight in a mixture of water and a
specified and
recorded mass of contaminant ¨ either octanoic acid (OA) or PFOA. The wet mass
of the
substrate was then recorded to determine capture of 0A/PFOA. The substrate was
next soaked
overnight in a solution of water and a specified and recorded mass of
sequestration agent ¨ either
Ca(OH)2 or CaCl2. NaOH was also added in the case of CaCl2. After soaking and
washing, the
wet mass of the substrate was recorded. The substrate was then dried in oven
and the dry mass
after drying was recorded. The sequestration agent solution was dried and the
mass of
precipitate from the solution was recorded.
[0109] The same basic procedure can then be repeated for a second and
subsequent rounds of
capture, regeneration and sequestration with mass measurements. Second and
third rounds were
completed for the present experiment. The dried substrate from the final step
of Round 1 was
soaked in water and the wet mass of substrate was recorded. Next, the
substrate was soaked
overnight in water and a contaminant ¨ either octanoic acid (OA) or PFOA. The
wet mass of the
substrate was then recorded to determine capture of 0A/PFOA. The substrate was
next soaked
in solution of water and a sequestration agent ¨ either Ca(OH)2 or CaCl2. NaOH
was also added
in the case of CaCl2. After soaking and washing, the wet mass of the substrate
was recorded.
The substrate was then dried in oven and the dry mass after drying was
recorded. The
sequestration agent solution was dried and the mass of precipitate from the
solution was
recorded.
[0110] Tables 1 - 4 show the results of the mass measurements for the
experiment over the
course of the initial wash procedure and three rounds of capture, regeneration
and sequestration.
Table 5 shows the recovered mass of precipitate recovered for each round. FIG.
5 shows visual
observation of St. Mary's Beads (activated carbon beads) over the course of
the first round of
testing.
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[0111] The results demonstrated that the carbon substrates were able to
releasably capture OA
and PFOA, and that the sequestration agent (calcium hydroxide or calcium
chloride) was able to
bind the OA or PFOA, be released from the carbon substrate, and be sequestered
as a precipitate.
The process was repeatable, showing the ability to capture OA and PFOA on the
carbon
substrate and subsequently regenerate the carbon substrate for multiple uses.
[0112] Table 1: Water Wash.
Vial Group Fresh Beads Wet
with Post Water Water wash
Dry Mass (g) water mass Dry mass (g) delta mass
(g) (g)
SM, PFOA, Ca(OH)2 2.5545 3.3140 Not taken NA
SM, OA, Ca(OH)2 2.5425 3.3125 2.5459 0.0034
SM, PFOA, CaC12 2.5320 3.3114 2.5340 0.0020
GAC, PFOA, 0.5209 1.2054 0.4976 -
0.0233
Ca(OH)2
GAC, PFOA, CaCl2 0.5295 1.4055 0.5026 -
0.0269
GAC, OA, CaCl2 0.5220 1.3529 0.4930 -
0.0290
[0113] Table 2: First Round of Capture/Release
Vial Group Mass of Wet mass of Mass of Wet mass
Dry First Bead/GAC
0
contaminant beads after sequestrant after mass regen mass
(0A/PF0A) 0A/PFOA Ca(OH)2/ regen 1 after dry
regeneration
(g) (g) CaCl2 (g) (g) regen 1
delta (%)
(g)
mass
(g)
SM, PFOA, 0.0963 3.3308 0.0075 3.3345
2.5641 0.0096 99.6242
Ca(OH)2
SM, OA, 0.1203 3.3151 0.0344 3.3209
2.5470 0.0011 99.9568
Ca(OH)2
SM, PFOA, 0.0581 3.3319 0.0089 3.3315
2.5419 0.0079 99.6882
CaCl2
GAC, PFOA, 0.0582 1.2376 0.0085 1.2052
0.5272 0.0296 94.0514
Ca(OH)2
GAC, PFOA, 0.0528 1.4704 0.0120 1.4067
0.5391 0.0365 92.7378
CaCl2
GACOACa 0.1258 1.3942 0.0603
1.3618 0.5756 0.0826 83.2454
C12
1-d
[0114] Table 3: Second Round of Capture/Release
Vial Wet mass Mass of Wet mass Mass of Wet
Dry Second Bead/GAC
0
Group after contaminant of beads sequestrant mass mass
regen mass
soaking in (0A/PFOA) after (Ca(OH)2/ after after dry
regeneration
water (g) 0A/PFOA
CaCl2) regen 2 regen 2 delta (%)
(g) (g) (g) (g) (g)
mass (g)
SM, 3.3306 0.0596 3.3390
0.0079 3.3360 2.5548 0.0003 99.9883
PFOA,
Ca(OH)2
SM, OA, 3.2067 0.1204 3.3017 0.0388 3.3209
2.5571 0.0112 99.5601
Ca(OH)2
SM, 3.3194 0.0501 3.3291
0.0231 3.3289 2.5350 0.0010 99.9605
PFOA,
CaCl2
GAC, 1.1961 0.0510 1.2529
0.0133 1.2077 0.5281 0.0305 93.8706
PFOA,
Ca(OH)2
,A1
GAC, 1.3947 0.0514 1.4315
0.0360 1.3988 0.5650 0.0624 87.5846
PFOA,
CaCl2
GAC,OA, 1.3270 0.1202 1.3587
0.0726 1.3762 0.5529 0.0599 87.8499
CaCl2
1-d
[0115] Table 4: Third Round of Capture/Release
Vial Group Wet Mass of Wet mass Mass of Wet
Dry Third Bead/GAC
0
mass contaminant of beads sequestrant mass
mass regen mass
after (0A/PF0A) after (Ca(OH)2/ after after dry regeneration
soaking (g) 0A/PFOA CaCl2) regen 3 regen 3
delta (%)
in water (g) (g) (g) (g) mass (g)
(g)
SM, PFOA, 3.3190 0.0543 3.3317 0.0102 3.3303
2.5559 0.0014 99.9452
Ca(OH)2
SM, OA, 3.2392 0.1116 3.3133 0.0403 3.3130
2.5459 0.0034 99.8665
Ca(OH)2
SM, PFOA, 3.3181 0.0531 3.3310 0.0286 3.3310
2.5376 0.0056 99.7790
CaCl2
GAC, PFOA, 1.1806 0.0511 1.2250 0.0151 1.2189
0.5461 0.0252 94.9357
cio
Ca(OH)2
GAC, PFOA, 1.4195 0.0522 1.4574 0.0391 1.4366
0.5961 0.0666 86.7489
CaCl2
GAC,OA,Ca 1.2767 0.1272 1.3020 0.0811
1.2835 0.5781 0.0561 88.6207
C12
1-d
[0116] Table 5: Recovered Mass of Precipitate
ROUND 1 ROUND 2
ROUND 3
0
Vial Regeneration Expected Actual Recover Expected Actual Recover
Expected Actual Recover
Group Precipitate
mass of mass of ed Yield mass of mass of ed Yield
mass of mass of ed Yield
precipita precipita (%) precipita precipita (%) precipita precipita (%)
te te te te
te te
(g) (g) (g) (g)
(g) (g)
SM, Calcium 0.088 0.073 83.66 0.064 0.053
83.49 0.057 0.050 87.50
PFOA, perfluoro-
Ca(OH)2 octanoate
SM, OA, Calcium 0.136 0.106 77.94 0.136 0.130
95.60 0.126 0.122 96.28
Ca(OH)2 octanoate
SM, Calcium 0.061 0.019 30.43 0.054 0.028
53.08 0.056 0.050 88.29
PFOA, perfluoro-
CaC12 octanoate
GAC, Calcium 0.061 0.052 86.04 0.055 0.035
63.67 0.053 0.038 70.22
PFOA, perfluoro-
Ca(OH)2 octanoate
GAC, Calcium 0.055 0.039 71.38 0.055 0.038
68.31 0.055 0.048 87.36
PFOA, perfluoro-
CaC12 octanoate
GAC, Calcium 0.142 0.072 50.21 0.136 0.128
93.83 0.140 0.106 73.89 od
OA, octanoate
CaCl2
cio
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[0117] Example 2: Carbon Bed Regeneration with Acid Wash
[0118] To assess regeneration capability, the sorption isotherm of fresh
activated carbon (Calgon
F400) was compared to the sorption isotherm of regenerated activated carbon
for a model PFAS
compound, perfluoroctanoic acid (PFOA).
[0119] Procedure:
[0120] Table 6: Raw data for each of the 20 flasks tested. All prewash
adsorbances were
measured on the 13 ml method.
PFOA Activated
concentratio Carbon Regen Water Acid Pre Wash Post Wash pH post UV Method
Flask n ([1g/kg) Mass (g) Washes Washes Washes Absorbance Absorbance
Wash Post Wash
1 225834 0.7503 2 3 0 0.53 1.338 6.49 1.5 mL
2 225834 0.7501 2 3 0 0.577 1.47 6.75 Method
3 225834 0.7506 2 3 1 0.502 0.93 4.15 13 mL
4 225834 0.7501 2 3 1 0.374 0.688 4.18 method
225834 0.75 2 2 0 0.881 1.693 7.34
6 225834 0.7507 2 2 0 0.471 1.317 7.29 1.5 mL
7 225834 0.7507 2 2 0 0.743 1.493 7.07 Method
8 225834 0.7508 2 2 1 0.593 0.794 4.02
9 225834 0.7504 2 2 1 0.765 0.888 4.05 13 mL
225834 0.7503 2 2 1 0.708 0.909 4.05 Method
11 225834 0.7501 1 3 0 0.663 1.448 6.82
12 225834 0.7505 1 3 0 0.619 1.407 6.64 1.5 mL
13 225834 0.7506 1 3 0 0.459 1.331 6.58 Method
14 225834 0.7503 1 3 1 0.636 0.912 4.12
225834 0.7503 1 3 1 0.473 0.949 4.1 13 mL
16 225834 0.7504 1 3 1 0.706 0.927 4.11 Method
17 225834 0.7501 1 2 0 0.732 1.516 7.24 1.5 mL
18 225834 0.7507 1 2 0 0.4 1.215 7.25 Method
19 225834 0.7507 1 2 1 0.696 0.72 3.99 13 mL
225834 0.7506 1 2 1 1.147 1.052 3.93 Method
[0121] Calgon F400 activated carbon was rinsed with DI water and dried at 100
C in a vacuum
oven. 0.1 g +/- 0.001 PFOA was weighed and placed into a 2 L clean glass
bottle. 2 L of
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deionized water was added to bottle, via volumetric flask. Actual input
weights and volumes
were recorded. PFOA was stirred until completely dissolved.
[0122] 102.70 g of DI water, +/- lg, was weighed into each of 20 250 ml
Erlenmeyer flasks
according to Table 6. With a micropipette 22.1 mL of PFOA stock was added,
1277345 g/kg.
Calgon F400 activated carbon was measured using a calibrated balance and
placed 0.75, +/-
0.001 g, each in 20 glass 250m1 Erlenmeyer flasks and shaken.
[0123] 2 oz. glass sample vials were prepared by rinsing with DI water and
removing foam seal
from cap. After 18 hours on the shaker, with a pipette (rinsed with DI water),
a 2 oz. sample was
removed from each condition, switching tips between samples, being careful not
to remove
activated carbon, and vials were rinsed with sample prior to filling. The
remaining PFOA
solution was removed from each flask and placed in waste.
[0124] A solution of 1 g/L Ca(OH)2 (regeneration fluid) was prepared, and
mixed on a stir plate
until all Ca(OH)2 was dissolved. 1% acetic acid wash was prepared by diluting
5% vinegar. 125
ml of Ca(OH)2 stock solution was measured into each flask and shaken at 150
rpm for 1 hour.
Regeneration solution was removed by pouring off liquid. Rinses were continued
according to
Table 6. Any following regeneration fluid rinse was shaken at 150 rpm for an
hour, following
acid or water rinses occurred for 30 minutes at 150 rpm. Any acid rinses were
completed after
the regeneration wash(es) and prior to the water washes. The solutions were
poured off before
the next rinse.
[0125] After rinsing, each flask was dosed again with 225834.6572 g/kg PFOA
solution.
102.70 g of DI water, +/- lg, was weighed into each of the 20 250 ml
Erlenmeyer flasks
according to Table 6. 22.1 mL of PFOA stock was added, 1277345.346 g/kg.
Flasks were
tipped slowly to ensure all activated carbon was submerged in water and not
stuck to the side,
and placed on the shaker at 150 rpm for 18 hours.
[0126] All samples were run with the UV-Visible Spectrometry method to measure
equilibrium
PFOA concentrations post regeneration. The pH was checked when samples were
taken.
[0127] UV-Visible Spectrometry Procedure
[0128] Two calibration standards were made at 10 and 11 points each using a
micropipette, DI
water, and PFOA batch solution. The 10 point curve was used for post-
regeneration non-acid
rinsed samples, and used 1.5 mL of standard as follows: 0, 600.36, 1000.59,
2000.33, 4257.84,
10644.60, 14902.44, 19160.28, 25547.03, and 38320.55 g/kg. The 11 point curve
was used for
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fresh carbon and post-regeneration acid rinsed samples, and used 13 mL of the
following
standards: 0, 50.24, 100.48, 200.12, 400.24, 800.47, 1000.59, 1500.46,
2000.33, 2554.70, and
2980.49 [tg/kg. Standards were filtered into DI rinsed vials using 0.22 p.m
PVDF/GF syringe
filters. All calibration samples were prepared with their appropriate quantity
of standard mixed
with 2.5 mL 1-octanol, and 1 mL methylene blue solution. Calibration samples
were ran on UV-
Visible method, to generate calibration curves.
[0129] 0.22 p.m 13 mm PVDF/GF syringe filter was used to filter each of the
samples into new
(DI water rinsed) vials, changing syringes and filters between samples.
Samples were filtered
because residual activated carbon will affect absorbance readings. All samples
were run on
UV-Visible Spectrometry methods to measure equilibrium PFOA concentrations for
fresh
activated carbon.
[0130] The UV Spectrophotometer was set to 664 nm. The organic and aqueous
phases were
separated cleanly in a test tube, and organic phase was removed, and placed
into a cuvette. The
cuvette was placed, with water-saturated octanol, in the UV Spectrophotometer
to zero the
machine, then the cuvette with sample was placed and ran to measure UV
absorbance.
[0131] pH probe was removed from storage solution, rinsed with deionized
water, and gently
wiped with Kimwipe. 4.01, 7.01, and 10.01 solutions were placed in vials.
Probe was calibrated
to 7.01, then to 4.01 and 10.01, then pH was checked for the 7.01 calibration
again. After
calibration, each flask was tested directly (with carbon in the flask),
swirling the flask while
testing and rinsing the probe between standards.
[0132] Results:
[0133] Table 7 shows equilibrium concentrations and percent recovery of
sorptive capacity for
each sample. Percent recovery was calculated by dividing the mass sorbed for
fresh carbon by
the mass sorbed for regenerated carbon and multiplying by 100.
[0134] Table 7:
Regenerated Fresh Regenerate
Fresh Carbon
Activated Regen Water Carbon Carbon d
Carbon Percent
Sample Acid Equilibrium
Carbon Washe Washe ui
. Eqlibrium Mass Mass Recovery of
Number Washes Concentration
Mass (g) s 5
( itg/kg) Concentratio Sorbed Sorbed Capacity
n (jig/kg)
1 0.7503 2 3 0 313 91134 37496
22396 59.73%
2 0.7501 2 3 0 354 104204 37499
20228 53.94%
3 0.7506 2 3 1 289 741 37485
37410 99.80%
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4 0.7501 2 3 1 192 462 37526 37481
99.88%
0.7500 2 2 0 680 129296 37450 16057 42.88%
6 0.7507 2 2 0 264 89169 37484 22710
60.59%
7 0.7507 2 2 0 520 106613 37442 19812
52.91%
8 0.7508 2 2 1 369 576 37462 37427
99.91%
9 0.7504 2 2 1 544 688 37453 37429
99.94%
0.7503 2 2 1 482 715 37468 37429 99.90%
11 0.7501 1 3 0 436 101938 37486 20605
54.97%
12 0.7505 1 3 0 393 97809 37473 21280
56.79%
13 0.7506 1 3 0 255 90475 37491 22496
60.00%
14 0.7503 1 3 1 410 718 37480 37429
99.86%
0.7503 1 3 1 266 766 37504 37421 99.78%
16 0.7504 1 3 1 480 737 37463 37421
99.89%
17 0.7501 1 2 0 508 109061 37474 19420
51.82%
18 0.7507 1 2 0 210 80049 37493 24226
64.61%
19 0.7507 1 2 1 470 495 37450 37446
99.99%
0.7506 1 2 1 1045 906 37360 37383 100.06%
[0135] Table 8 is a summary table showing the average percent recovery of
sorptive capacity for
the high number and low number of rinses for each process step. The difference
between the
percent recovery for the high and low number of rinses for each demonstrates
the level of
importance of each washing step (regeneration fluid, wash water, acetic acid
rinse) on the
percent recovery.
[0136] Table 8:
Average Average Average Average Average Average
Percent Percent Percent Percent Percent
Percent
Recovery for Recovery Recovery for Recovery for Recovery
Recovery
all Low for all High all Low all High
for all for all
Number of Number of Number of Number of Low High
Regen Rinses Regen Water Rinses Water Rinses Number Number of
Rinses of Acid Acid
Rinses Rinses
Average Percent
Recovery for each
rinse condition 78.78% 76.95% 77.26% 78.46%
55.82% 99.90%
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Difference in Average
Percent Recovery
from High Number of
Rinses to Low
Number of Rinses -1.83% 1.20% 44.08%
[0137] Table 9 shows the average mass sorbed and percent standard deviation
for all duplicates
in each condition.
[0138] Table 9:
Percent Standard Percent
Number of
Regen Water Acid Average Mass
Condition Deviation in Mass Recovery of Samples in
Washes Washes Washes Sorbed (ug/g)
Sorbed Capacity Subset
Fresh - - - 37472 0.0903% 20
Regenerated 2 3 0 21312 0.0001% 56.84% 2
Regenerated 2 3 1 37446 0.1348% 99.84% 2
Regenerated 2 2 0 19526 17.0833% 52.13% 3
Regenerated 2 2 1 37429 0.0027% 99.91% 3
Regenerated 1 3 0 21460 4.4660% 57.25% 3
Regenerated 1 3 1 37423 0.0123% 99.84% 3
Regenerated 1 2 0 21823 15.5709% 58.22% 2
Regenerated 1 2 1 37414 0.1196% 100.03% 2
[0139] Table 10 is a summary table showing the average pH for the high number
and low
number of rinses for each process step. The difference between the pH for the
high and low
number of rinses for each demonstrates the level of importance of each washing
step
(regeneration fluid, wash water, acetic acid rinse) in changing the pH of the
process.
[0140] Table 10:
Average
Average pH Average pH Average pH Average pH Average pH
pH for all for all High
for all Low for all High for all Low for all High
Low
Number of Number of Number of Number of Number of
Number of Regen Water Water
Acid Rinses Acid Rinses
Regen Rinses Rinses Rinses
Rinses
Average pH for each rinse
condition 5.478 5.539 5.623 5.394 6.947 4.07
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Difference in
Average pH from
High Number of
Rinses to Low
Number of Rinses 0.061 -0.229 -2.877
[0141] Conclusions:
[0142] The study demonstrated successful regeneration of the carbon to capture
PFOA. Percent
recovery along all conditions ranged from 42.88% to 100.06%. The average
percent recovery for
samples seemed to be the most affected by acid washing. Increasing the number
of regeneration
rinses from 1 to 2 decreased the average percent recovery by 1.83%, while
increasing the water
washes from 2 to 3 increased percent recovery by 1.20% (Table 8). Increasing
the number of
acid washes from 0 to 1, however, increased percent recovery by 44.08%,
bringing the average
percent recovery for all acid washed samples to 99.90% (Table 8). This
indicates that a decrease
in both the number of regeneration washes and the number of water washes has
little effect on
the process.
[0143] The pH was also most greatly affected by the acid washing step,
dropping by 2.877 on
average for acid washed samples (Table 10). Increasing water rinses also
decreased the pH
(Table 10), likely due to rinsing off excess regeneration fluid. Increasing
the regeneration rinses
slightly increased the pH on average, likely because regeneration fluid is
basic.
[0144] Low percent standard deviation for fresh samples demonstrated high
repeatability for
fresh carbon (Table 9). For regenerated samples, percent standard deviation
remained below 1%
for all samples except for 3 samples: 2 Regen Washes/2 Water Washes/0 Acid
Washes, 1 Regen
Wash/3 Water Washes/0 Acid Washes, and 1 Regen Wash/2 Water Washes/0 Acid
Washes.
[0145] Example 3: Regeneration of Samples with Mixed Contaminant
[0146] Experiments were performed to evaluate the performance of a
regeneration system for
capturing contaminants from complex samples more closely resembling
groundwater. Complex
samples were modeled using a mixture of PFOA, PFNA, and PFOS, with and without
humic
acid.
[0147] Calgon F400 activated carbon was rinsed with DI water and dried. PFOA,
K-PFOS, and
PFNA stock solutions were prepared. A humic acid solution was also prepared.
Fresh carbon
samples were prepared and tested as shown in Table 11. Regenerated samples
were also
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prepared and tested. For the regenerated samples, carbon samples were exposed
to contaminant
solutions as shown in Table 11 and allowed to reach equilibrium, then samples
were regenerated
with Ca(OH)2 solution, regeneration solution was poured off, carbon bed
samples were rinsed
again with regeneration solution, and then finally carbon samples were treated
a second time
with same contaminant solutions as shown in Table 11. Absorption of
contaminant was tested in
fresh and regenerated carbon bed samples with and without humic acid as shown
in Table 11.
[0148] Table 11 - Experimental setup for testing
Volume Volume Volume Calgon F400 Regeneration Humic
Acid
38451.0 g/kg 43131.6 g/kg 46461.5 g/kg Mass (g) Condition
Concentration
PFOA stock PFNA stock PFOS stock (mg/1)
added (m1) added (m1) added (ml)
0 0 0 0.7502 Fresh and 0
Loaded
0.01 0.01 0.01 0.7508 Fresh and 0
Loaded
0.1 0.1 0.1 0.7501 Fresh and 0
Loaded
1 1 1 0.7504 Fresh and 0
Loaded
10 10 0.7502 Fresh and 0
Loaded
0 0 0 0.7502 Regenerated 0
Reloaded
0.01 0.01 0.01 0.7506 Regenerated 0
Reloaded
0.1 0.1 0.1 0.7508 Regenerated 0
Reloaded
1 1 1 0.7501 Regenerated 0
Reloaded
10 10 10 0.7502 Regenerated 0
Reloaded
0 0 0 0.7506 Fresh and 0
Loaded
0.01 0.01 0.01 0.7508 Fresh and 10
Loaded
0.1 0.1 0.1 0.7503 Fresh and 10
Loaded
1 1 1 0.7504 Fresh and 10
Loaded
10 10 10 0.7302 Fresh and 10
Loaded
0 0 0 0.7507 Regenerated 10
Reloaded
0.01 0.01 0.01 0.7506 Regenerated 10
Reloaded
0.1 0.1 0.1 0.7503 Regenerated 10
Reloaded
1 1 1 0.7508 Regenerated 10
Reloaded
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10 10 0.75 Regenerated 10
Reloaded
0 0 0 0 N/A 10
10 10 10 0 N/A 0
[0149] Results of absorption testing are shown in Figures 6-11. The carbon bed
effectively
captured PFOA, PFNA, and PFOS from the mixed contaminant solution both for
fresh carbon
samples and regenerated carbon samples. Capture was effective both in the
presence and
absence of humic acid. Thus, the regenerated system was effective for
capturing mixed
contaminants.
[0150] Example 4: Column Testing
[0151] In view of the successful regeneration in Examples 1-3, column testing
was performed to
investigate a model column system with flow of contaminated solution and
regeneration solution
through the column.
[0152] A small column (10 cm tall x 1.5 cm diameter) was loaded with freshly
rinsed and dried
GAC (14-15 g Calgon F400) as a capture bed. The capture bed was rinsed with DI
water and
then dosed with a 100 ppm PFOA solution. The filtrate was sampled every 3000s
until 31
samples were collected for producing a first curve of PFOA concentration in
the filtrate. The
dosing solution was pumped at a rate where the contact time was approximately
160s and the
column filtered 12-14L until sampling was complete. Regeneration fluids were
pumped through
the column in order, with volumes chosen to be 50x or more of the free volume
of the column.
The first regeneration solution was a detergent solution of octanoic acid
(0.2g in 1L DI water).
The second regeneration solution was an aluminum hydroxide solution (320g NaOH
and 480g
Al(OH)3 in 16L DI water). The third regeneration solution was a calcium
hydroxide solution (4g
Ca(OH)2 in 2L DI water). The fourth regeneration solution was a sodium
hydroxide solution (4g
NaOH in 1L DI water). Finally, the fifth regeneration solution was an acid
wash solution
(250mL 12.39M HC1 solution in 15.75L DI water). Regeneration DI water was then
pumped
through the column until filtrate was pH > 5. To produce the second curve for
regenerated
capture bed, the same procedure was followed for dosing with 100 ppm PFOA
solution.
[0153] Figure 12 shows the initial and regenerated breakthrough curves for the
column filtering
the 100 ppm PFOA feed solution. The feed concentration is shown as the dashed
line. Early
sample vials had low PFOA concentration, showing capture of PFOA on the carbon
bed,
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although some PFOA is able to pass through the column even for early vials.
The regeneration
curve shows that the regenerated bed captured PFOA and closely followed the
performance of
the fresh bed with a slight decrease in capture rate.
[0154] A second separate experiment did not show the same regeneration
effectiveness. It is
hypothesized that the second experiment did not provide enough regeneration
fluid to regenerate
the column.
[0155] Thus, it is shown that the regeneration process can be effectively used
in a column setup
with flow of contaminated liquid through the column.
OTHER EMBODIMENTS
[0156] It is to be understood that while the invention has been described in
conjunction with the
detailed description thereof, the foregoing description is intended to
illustrate and not limit the
scope of the invention, which is defined by the scope of the appended claims.
Other aspects,
advantages, and modifications are within the scope of the following claims.
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