Note: Descriptions are shown in the official language in which they were submitted.
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TTTLE:
DNAPL Geo-Remedial Chemical Compound
BACKGROUND OF THE INVENTION:
Dense non-aqueous phase liquids (DNAPL) are present at numerous commercial and
government sites. Examples of such liquids include chlorinated solvents,
creosotes, and
coal tars. DNAPL have the potential to migrate to great depths below the water
table as
they are denser than water. Two characteristics of common DNAPL components,
low
aqueous solubilities and high interfacial tensions with water, result in the
persistence of a
non-aqueous phase and very irregular distribution of DNAPL in the subsurface.
This in
turn presents significant difficulties for site remediation. Remediation
efforts also may
risk mobilizing DNAPL and hence spreading contamination to previously clean
regions.
Accidental and intentional release of these hazardous wastes threatens
environmental
sustainability and human health. The capacity of soils to detoxify waste has
been well
documented. This capacity is limited however, and natural detoxification
processes often
require years to restore impacted sites.
Remediation of these contaminants has been the interest of the environmental
sector.
These remediation efforts have primarily focused on mechanical and physical
removal of
contaminants, contaminated soils, rocks and backfill materials to approved
landfill sites.
More recently, interest has shifted to in-situ prpcedures to remediate these
sites and avoid
groundwater contamination.
The potential to enhance the recovery of non-aqueous phase liquids (NAPL) from
porous
media using chemical surfactant and co-solvent flushing is widely recognized
and has
been applied in petroleum reservoirs since the mid-1920s (Beckstrom and Van
Tuyl,
1927). Since the late 1970s, a growing interest has developed in the use of
similar
chemical systems to mitigate risk posed by subsurface DNAPL (API, 1979). This
interest
reflects, in large part, the ineffectiveness of currently available remedial
technologies to
restore NAPL zones in aquifers to typical concentration-based drinking water
standards
(NRC, 1994 ; Pankow and Cherry, 1996). Investigation of the potentials for
surfactant
and co-solvent applications of in-situ remediation is well documented by
Jafvert, C. T.
( 1996).
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The use of surfactants and co-solvents will lead to a lowering of DNAPL-water
interfacial tension, which may in turn lead to vertical remobilization of the
DNAPL. The
risk of downward DNAPL mobilization can be reduced and even eliminated through
the
use of upward hydraulic gradients. Through proper surfactant/co-solvent
selection, it is
be possible to reduce the density of the target DNAPL to below that of water,
thereby
eliminating the threat of downward DNAPL mobilization. A surfactant/co-solvent
injection may result in a micro-emulsion that is more dense than water, which
may be
difficult to recover if its density becomes greater than that of water.
Conversely, a
reduced density micro-emulsion of DNAPL may migrate horizontally with
groundwater
flow spreading contaminants laterally and into the groundwater.
PRIOR ART:
Kammeraad (US Patent No. 5634983) describes a process of mixing contaminated
soil
with a blend of non-ionic and anionic surfactants in conjunction with an
amphoteric
surfactant as a chelating agent, in a hopper, to encapsulate the hydrocarbon
contaminants.
This method requires the removal of the contaminated soil from the ground and
does not
address the issues of contaminated groundwater.
From Varadaraj's US Patent No. 5436160, bioremediation of hydrocarbon
contaminated
soil, we learn of an improved method of enhancing bioremediation via the
injection of a
blend of surfactants composed of sorbitan esters and alkyl glucosides to
assist in making
hydrocarbons more available to micro-organisms, followed by the separate
injection of
microbial nutrients, such as nitrogen and phosphorous containing compounds, to
enhance
biodegradation of the contaminated hydrocarbons. Varadaraj's invention does
not address
the need to control downward vertical or horizontal migration of dense non-
aqueous
phase liquids.
Bartlett et al, in United States Patent S,370,478 describes a zone beneath the
water table
which prevents both lateral and down-ward movement of contaminants or
contaminated
water by use of vertical barner walls of low permeability grout. Bartlett's
approach is a
physical barrier concept to maintain contaminated water.
Lessage, in United States Patent S,64S,374, teaches us how to dehalogenate
contaminated ground water or effluents and/or soils that are contaminated with
halogenated organic compounds, by using a titanium carboxylic acid derivative
and a
corrin or porphyrin catalyst. This dehalogenation process of DNAPL does not
address
the horizontal or vertical migration of DNAPL, or the direct solubilization
for
contaminated effluent extraction.
Pugh, in United States Patent 5,976,348, describes an invention relating to
the in situ
decontamination of soils using electric fields to transport strong oxidants,
preferably
peroxymonosulfate or peroxydisulfate, through the soil. Pugh's invention does
not
address migrational controls of in-situ DNAPL.
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Taciuk, Canada Patent 2054122, describes a innovation for dechlorinating soils
contaminated with PCBs andlor chlorinated compounds using rotary kiln, and a
reaction
of alkali metal hydroxide and a glycolate surfactant. Taciuk's innovation
relies on
physical removal of contaminated soils.
Clark, in United States Patent 5,824,162, describes the use of terpenes as an
industrial
solvent and their effectiveness compared to typical chlorinated solvents such
as
trichloroethylene, perchloroethylene, methyl chloroform and methylene
chloride. These
chlorinated solvents are characterized as dense non-aqueous phase liquids when
emitted
into the aquifer.
Shook et al, in United States Patent 5,993,660 teaches us a method for
controlling
vertical migration of contaminants in an aquifer includes introduction of a
solubilizing
solution having a surfactant and an alcohol or other light co-solvent. The
surfactant is
selected to solubilize the contaminant. The alcohol or other solvent is
selected to provide
the micro-emulsion with a substantially neutral buoyancy with respect to
groundwater.
The neutral buoyancy of the micro-emulsion prevents the normal downward
movement
which is typical of the solubilized dense non-aqueous phase liquid in
surfactant-enhanced
aquifer remediation. Shook's method relies on adjusting the density of the
DNAPL to
effect downward vertical migrational controls, but does not effect a
horizontal
migrational control.
In view of what has been previously proposed in the prior art, it is clear
that there exists a
need and that it would be both desirable and advantageous to have an effective
chemical
preparation that could remove large amounts of DNAPL in a relatively short
period of
time. It would also be desirable and advantageous to have a chemical
preparation that
could remove DNAPLs found as residual pools, both in the soil and in the
groundwater.
It would also be desirable and advantageous to have a chemical preparation
that can
reduce the density of the contaminant DNAPL to reduce downward vertical
migration. It
would be further desirable and advantageous to have a chemical preparation
that would
have inherent horizontal migratory controls. It would again be desirable and
advantageous to have a chemical preparation of low toxicity, based primarily
upon a
solvent that is naturally occurring in nature. It would be additionally
desirable and
advantageous to have a chemical preparation that could be mixed with water on
site. It
again would be desirable and advantageous to have a chemical preparation that
is readily
biodegradable and supports microbiological activity in the contaminated soil
or
groundwater.
Previous methods of in-situ treatments for petroleum hydrocarbons included
hydrogen
peroxide, aqueous solutions of micro-organisms, alcohols, toxic solvents or
surfactants.
Peroxide treatments would oxidize these hydrocarbons but provide no
solubility, were
dangerous to handle and difficult to control reaction rates. Micro-organisms,
also known
as bio-remediation, is a slow process of metabolism of petroleum hydrocarbons
to carbon
dioxide and water. Short comings in bio-remediation treatments are control of
soil pH's,
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lack of year round moderate temperatures, other toxic soil contaminants and
availability
of specific nutrients. Alcohols, such as isopropyl or methyl alcohol used as
in-situ
treatments as solubilizing agents are highly flammable, dangerous to handle
and can be
toxic to indigenous micro-organisms. Toxic solvents such as toluene, used as
solubilizing
agents are extremely toxic, highly flammable, dangerous to handle and can
often worsen
existing contaminant profiles, by adding unwanted toxins if the procedures are
not finely
controlled. Surfactants alone lack solubilities for wide ranges of DNAPL and
require
large pore volumes of water to stimulate a pump and treat technology or
extraction
technology.
SPECIFICATION:
This invention relates to the effective aquifer DNAPL remedial composition,
and method
of its manufacture.
It is another objective of this embodiment to provide an aquifer DNAPL geo-
chemical
remedial composition, that can effectively decontaminated a large volume of
soil, a large
area of land or a large volume of water that contains DNAPL.
It is also another objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition that can reduce the high cost of soil and water
removal
and excavation, by being used in-situ.
It is further another objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition that can reduce the density of the contaminant
DNAPL to
reduce downward vertical migration.
It is an additional objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition that is based primarily upon a naturally
occurring solvent
as a co-solvent.
It is again a further objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition that uses a monoterpene, a naturally occurring
non-polar
hydrocarbon solvent, as a co-solvent to co-solubilize with the contaminated
DNAPL in
the aquifer, to create or effect a combined monoterpene-DNAPL of lower density
than
the original contaminating DNAPL, which will reduce the tendency of the
combined
monoterpene-DNAPL to migrate vertically downwards in an aquifer.
It is yet another objective of this embodiment to provide an aquifer DNAPL geo-
chemical remedial composition that can be mixed or diluted on site, with
either hard or
soft water.
It is yet further the objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition to form a micro-emulsion of the combined
monoterpene-
DNAPL, in-situ, with the non-ionic surfactant, in the presence of water
provided by
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preparing aquifer DNAPL remedial composition, or by groundwater, or by pore
volumes
of water added to the contaminated aquifer.
It is yet an additional objective of this embodiment to provide an aquifer
DNAPL geo-
chemical remedial composition that may be able to control horizontal migration
of the
said formed micro-emulsion in-situ, by negating the surfactant properties of
the said non-
ionic surfactant, through a process of splitting the hydrophilic head from the
hydrophobic tail of the said non-ionic surfactant by hydrolysis, rendering the
non-ionic
surfactant into a water soluble hydrophilic head and a non-water soluble
hydrophobic tail
portion.
It is again an objective of this embodiment to provide an aquifer DNAPL geo-
chemical
remedial composition that can be stopped from horizontally migrating of DNAPL
in the
soil or groundwater.
It is further another objective of this embodiment to provide an aquifer DNAPL
geo-
chemical remedial composition that will be readily biodegradable and support
microbiological activity in the contaminated aquifer.
It is a further objective of this embodiment to provide a method for preparing
an aquifer
DNAPL geo-chemical remedial composition containing the steps of:
Adding with agitation, from about a 0.01 % to 5.00 % volume of ethylene
diamine tetraacetic acid-sodium salt, to water a 5.00 % to 25.00 % volume, to
create a substantially homogeneous resultant mixture.
2. Then adding with agitation, from about 0.01 % to 10.00 % volume of a
phosphate,
to the first homogeneous mixture to create a substantially second homogeneous
resultant mixture.
Then again with agitation the addition from about 0.50 % to 95.00 % volume of
non-ionic surfactant to the second resultant mixture to obtain a third
substantially
homogeneous resultant mixture.
4. Following, still with agitation, an addition from about 0.50 % to 80.00 %
volume
of a monoterpene, to the third homogeneous mixture to create a fourth
substantially homogeneous mixture.
5. Water forms the remainder of the geo-chemical solvent remedial composition
of
this invention. It can be present from about 10 to about 95% volume, based on
the
total weight of the final aquifer DNAPL geo-chemical remedial composition .
Preferably it should be present from about 5.0 to 75.0 volume % Most
preferably,
it should be present in a total amount of about 56.73 volume %.
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This invention precludes the use of toxic solvents, oxidizers, aicohols or
flammable
materials and does not require physical or mechanical removal of contaminated
soils, or
contaminated groundwater.
DETAILED DISCUSSION:
Broadly, the aquifer DNAPL geo-chemical remedial composition of this invention
contains from 0.01 % to 10.0 % volume of a chelant, from about 0.01 % to about
10.0
volume of a phosphate, , from about 0.50 % to about 95.0 % volume of an non-
ionic
surfactant, from about 0.50 to about 80.0 % volume of a monoterpene and the
remainder
water.
The first two ingredient used in this invention are a chelant and water. A
chelant or
chelating agent is an organic chemical compound used in formulations to assist
the
formulated compound to withstand precipitating effects of commonly present
precipitating and scaling agents.
Common precipitating and scaling agents are, among others, alkaline earth
metals such as
calcium and magnesium, divalent metals such as copper, and amphoteric metals
such as
aluminum. The removal of undesirable metal ions is often difficul and it is
usually easier
to inactivate them with a chelating agent. Undesirable metal ions may be found
present in
water used for formulating or held and/or commercial dilution purposes of the
final
aquifer DNAPL geo-chemical remedial composition. Amino acid chelating agents
are
known to be stable in acid or alkaline solutions and at elevated temperatures.
Amino acid
chelating agents securely bind metal ions to form stable complexes, which
remain very
soluble in this form. They are also quite resistant to the action of oxidizing
or reducing
agents and exhibit low toxicity.
For this invention, the most preferred chelant is the sodium salt of
ethylenediamine
tetraacetic acid. This is a commercially available compound from chemical
vendors. The
sodium salt of ethylenediaminetetraacetic acid in this invention is present at
a level from
about 0.01 % to 10.00 % volume, based upon the total volume of the aquifer
DNAPL
geo-chemical remedial composition. Preferably, the ingredient should be
present at a
volume from about 0.15 % to 2.00 % volume. Most preferably about 0.20 % volume
of
this ingredient should be used.
Water is used as the diluant and carrier in this geo remedial composition.
Water is
initially present at a level from about 5.0 % to 25.0% based upon the total
volume
Preferably water is initially present at a level of 7.0 % to 20.0% of the
total volume and
most preferably, water is initially present at a level of 20.0 % of the total
volume.
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CA 02327443 2000-11-27
The next ingredient of this aquifer DNAPL geo-chemical remedial composition is
a
phosphate. Soluble phosphate salts are commercially available produced from
the
neutralization of orthosphosphoric acid with an alkali. Another member of the
commercial phosphate compounds are the molecularly dehydrated phosphates.
Phosphates have been used in many types of detergents, cleaning compounds,
industrial
boiler water and cooling treatments. Certain phosphates also been used for
many years in
controlling scale deposition in potable water systems and as buffers in
propylene glycol
based antifreeze compounds. Thus, they find application in water conditioning
and
cleansing operations. Phosphates not only soften water, but have other
properties such as
the ability to deflocculate and suspend insoluble materials, emulsify oils,
etc., which aid
in the desorption and removal of DNAPLs from soil substrates. Phosphates also
act as a
basic nutrient source for many species of micro-flora. While not wishing to be
bound by
theory, it is believed that the incorporation of phosphate as an ingredient
into this
invention will assist in the desorption and removal of DNAPL from soil
substrates and
contribute to the stimulation and growth of naturally occurring hydrocarbon
assimilating
microflora.
For this invention, the most preferred phosphate is sodium hexametaphosphate.
This is a
commercially available compound from industrial and commercial chemical
vendors.
Sodium hexametaphosphate in this invention is present at a level from about
0.01 % to
10.00 % volume, based upon the total volume of the final aquifer DNAPL geo-
chemical
remedial composition. Preferably, the ingredient should be present at a volume
from
about 1.00 % to 2.50 % volume. Most preferably this ingredient should be
present about
1.17 % volume.
The next ingredient in this invention is a surfactant. Surfactants are organic
compounds
consisting of two parts: ( I ) A hydrophilic portion, usually including a long
chain
hydrocarbon; and (2) a hydrophilic portion which renders the compound
sufficiently
soluble in water or other polar solvents. This combination of the two parts,
hydrophilic
and hydrophobic portions in a surfactant render the surfactant surface-active
and thus
able to concentrate at the interface between a substrate to be cleansed. Two
properties of
surfactants are central to contaminated aquifer remediation technologies are
the ability to
lower interfacial tension and the ability to increase solubility of
hydrophobic organic
compounds.
Both properties arise from the fact that surfactant molecules have a
hydrophobic portion
and a hydrophilic portion. As a result, when water containing surfactant and
DNAPL
come into contact, surfactant molecules will concentrate along the interface,
with their
polar ends in the water and their non-polar ends in the DNAPL; this lowers the
interfacial
tension between the two immiscible fluids. When present in sufficient
concentration the
critical miCellar concentration (CMC), surfactant molecules form oriented
aggregates,
termed micelles. In water, the molecules in a micelle are arranged with their
polar ends
outwards and their non-polar ends inwards, forming a non-polar interior to the
micelle.
Micelles can incorporate hydrophobic molecules in their interior, producing an
apparent
increase in solubility. The process of dissolving by incorporation into
micelles is termed
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solubilization. Once solubilized, a compound is transported as if it were a
typical
dissolved phase. Micellar solutions may either be a single phase system in
which micelles
containing solubilized contaminant are transported as a dissolved phase in the
groundwater, or a separate phase, termed a middle phase micro-emulsion, in
which a
separate phase containing approximately equal volumes of surfactant and
contaminant is
formed.
The extent of increase of solubility (solubilization) produced depends upon
the
contaminant, the surfactant, the salinity and the surfactant concentration.
Increases in
solubility of more than five orders of magnitude and solubilities in the
hundreds of
thousands of mg/L have been reported for common DNAPL components (Baran et al,
1994). Early surfactant field trials used surfactants that produced modest
increases in
solubility (one or two orders of magnitude) and extracted the DNAPL through
slow
dissolution. This approach required multiple pore volumes (more than 10)
(Fountain et
al, 1996). More recent work has emphasized higher performance systems that
produce
solubilizations above 100, 040 mg/L (Brown et al., 1997).
Surfactants are additionally categorized as anionic, cationic or non-ionic. An
anionic
surfactant' hydrophilic molecule portion contains a negative charge. A
cationic
surfactant's hydrophilic portion contains a positive charge. A non-ionic
surfactant does
not dissociate but derive their hydrophilic portions from polyhydroxy or
polyethoxy
structures. Additional categorization of surfactants is amphoteric and
zwitterionic. These
are less common than the anionic, cationic and non-ionic surfactants.
It is known that avionics, cationics, and amphoteric surfactants which contain
charged
ions can be neutralized (i.e., lose surfactant properties) by adjusting the pH
of the
mixtwe. However, this does not work for conventional nonionic surfactants,
other than
certain amine-based surfactants, since they do not carry a charged moiety.
For this invention the preferred type of non-ionic surfactant is an acetyl
based non-ionic
surfactant and more preferably the surfactant for this invention is an acetyl
based non-
ionic surfactant manufactured by Union Carbide under the trade name "Triton SP
series
surfactants". Accordingly, the Union Carbide Triton SP series surfactants are
manufactured from certain cyclic acetals having a pendant hydroxyl goup that
function
as the hydrophobe portion of a pH-splittable surfactant. This series of Union
Carbide
Triton SP series surfactants which have been alkoxylated or otherwise
modified, are
surfactants with a wide range of HLBs and having performance properties which
are
surprisingly superior to those exhibited by other surfactants of related
chemical structure.
This actual bond-breaking process, which affords a hydrophobe portion and a
hydrophile
portion, is splittable and referred to as splittable. Moreover, contrary to
the prior amine-
based surfactants, which are generally regarded as "reversibles," Union
Carbide Triton SP
series surfactants do not re-form into surfactants when the pH is again raised
to the
alkaline range. These Union Carbide Triton Sp series surfactants act as
nonionic
8
CA 02327443 2000-11-27
surfactants in an alkaline or high pH environment. (n an acidic environment,
these
surfactants undergo, due to the presence of the acetal chemical functionality,
a chemical
splitting of the hydrophobe portion of the surfactant from the hydrophile
portion, which
destroys their surfactant properties, thereby breaking down their association
with the
hydrophobic constituents, and allowing them to more easily separate from the
aqueous
phase.
In broad terms, the this provides the splittable, nonionic surfactant portion
of this
invention, conforming to the deactivation of the surfactant to release the
monoterpene-
DNAPL contaminant mixture from association with the surfactant, by adjusting
the pH of
the aqueous stream to an acidic pH sufficient to split the surfactant
irreversibly into a
relatively water-insoluble fraction and a relatively water-soluble fraction.
The released
monoterpene-DNAPL and the water-insoluble fraction of the surfactant form a
relatively
water-insoluble phase
The catalyzed hydrolysis of acetals has been extensively studied in the art.
For example,
T. H. Fife, Accounts of Chemical Research, Volume S {1972), pp. 264-272; and,
E. H.
Cordes and H. G. Bull, Chemical Reviews, Volume 74(1974) pp. S81-603. From
these, it
is apparent that the rate and reaction conditions necessary to cause carbon-
oxygen bond
rupture of the acetal are complex. While not wishing to be bound by theory,
the splittable,
nonionic surfactants of this invention may be split over a wide range of
pressures ranging
from atmospheric or sub-atmospheric pressures to super-atmospheric pressures.
The splittable, nonionic surfactant in this final aquifer DNAPL geo-chemical
remedial
composition is split into a relatively water-insoluble fraction (hydrophobic)
and a
relatively water-soluble (hydrophilic) fraction. The water-insoluble fraction
comprises an
aldehyde and the water-soluble fraction comprises an alkoxylated polyol.
Neither fraction
produced from the hydrolysis is surface-active, so the monoterpene-DNAPLs are
released
from association, e.g., emulsion, with the surfactant. The monoterpene-DNAPL
and the
hydrophobic fraction of the surfactant form a relatively water-insoluble phase
in the
aqueous stream. At least a portion of this phase in the spent aqueous stream
can
recovered by conventional methods such as filtration, skimming, and the like.
A
substantial portion of the water-insoluble phase can be recovered. The
recovered water-
insoluble phase can be disposed in accordance with regulatory requirements.
The
remaining aqueous stream can be discharged to a water treatment effluent
system after a
final pH adjustment to a relatively non-acidic pH that conforms the waste
effluent to
environmental regulations,
Suitable acids for splitting the surfactant in this final aquifer DNAPL geo-
chemical
remedial composition, are for example, sulfuric acid, hydrochloric acid,
acetic acid, etc.
Preferably, the pH of the adjusted solution is from about pH 3 to about pH 6.
The amount
of acid to be added is an amount sufficient to cause splitting of the
surfactant.
CA 02327443 2000-11-27
The surfactants useful in this invention have been broadly described in the
art,
particularly U.S. Pat. Nos. 3,948,953 and 3,909,460, as well as Polish
Temporary Pat.
Nos. 115,527 and 139,977.
The Triton SP 140 surfactant in this invention is present at a level from
about 0.10 % to
95.0 % volume, based upon the total volume of the final aquifer DNAPL geo-
chemical
remedial composition. Preferably, the ingredient should be present at a volume
from
about 3.00 % to 25.00 % volume. Most preferably about 17.00 % volume of this
ingredient should be used.
The next ingredient in this invention is a monoterpene . Terpenes are a
classification of
biogenic compounds; monoterpenes are a subgroup of terpenes, some of which
have
stntctures which be thought as being loosely based on that of two isoprene
molecules.
Terpenes are the most abundant and widely distributed class of natural
products. Many
play important biological roles and numerous of them are used by humans and as
components of spices and flavours. (ane very important group includes vitamins
A, D and
E, and hormones (cortisone, estrogen and testosterone).
Monoterpenes can be either acyclic (e.g. myrcene), or contain one ring, called
monocyclic (limonene), or two ring structures (alpha and beta-pinene, 3-
carene). The
emissions from deciduous (hardwood/broadleaf) trees such as oak, poplar,
aspens and
willows comprise mainly of isoprene, whereas coniferous (softwood) woodland
such as
pine trees, cedars, redwood and firs emit predominantly monoterpene.
Monoterpenes are found in essential oils of many plants, including fruits,
vegetables and
herbs. They prevent the carcinogenisis process at both the initiation and
promotion/progression stages. In addition, monoterpenes are effective in
treating early
and advanced cancers. Monoterpenes such as limonene and perillyl alcohol have
been
shown to prevent mammary, liver, lung and other cancers. They have also been
used to
treat rodent cancers, including breast and pancreatic carcinomas. In addition,
in vitro data
suggest that they may be effective in treating neuroblastomas and leukemias.
(Gould, 1997)
For this invention, the most preferred monoterpene is d-limonene. This is a
commercially
available compound from industrial and commercial chemical vendors. d-Limonene
has a
flash point of approximately I 15 degrees F., categorizing it as a combustible
liquid not
flammable, a specific gravity of approximately 0.84, and is characterized
being non-polar
and insoluble in water.
Limonene (C6Hlo) has the properties of optical rotation. There are two
optically differing
types of limonene, d and 1. c~ limonene rotates to the right and l-limonene
rotates to the
CA 02327443 2000-11-27
left. d-Limonene is one of the naturally occurring monoterpenes, and is found
in high
concentrations in citrus fruits. Because of its pleasant citrus fragrance, it
is widely used as
a flavor and fragrance additive in perfumes, soaps, foods, chewing gum and
beverages.
Also, because d-limonene is a relatively safe and highly effective organic
solvent, it is
finding increasing use in household and industrial cleaning products,
replacing dangerous
petroleum-based solvents and environmentally hazardous hydrocarbon solvents.
Another
application of d-limonene has been as an odorant in sewage treatment plants.
Additionally, the manufacture of d-limonene is ecologically sound since
discarded citrus
pulp and peels from the citrus juice industry are used as the source material
for this
chemical.
It is well established that d-limonene, in man and in other species of
mammals, is rapidly
broken down by the liver. Considering its natural origin, it is generally
believed that
d-limonene and related products are readily degraded. Indirect evidence for
this belief
can be found in publications by several investigators who have demonstrated
the ability
of certain types of bacteria, called Pseudomonads, to totally degrade d-
limonene-like
compounds. Other types of bacteria, such as Enterobacteria are capable of
transforming
d-limonene into other by-products, such as dihydroperillic acid and perillic
acid.
d-Limonene is easily degraded by microorganisms found in forest soil, and
Bacillus
stearothermophilus can grow on and degrades d-limonene.
t~Vhen used in or on food, d-limonene is regulated by the United States, Food
and Drug
Administration (FDA) Title 21 of the Code of Federal Regulations lists d-
limonene (and
its variant forms 1-limonene, and dl-limonene) as a Generally Recognized as
Safe
(GRAS) food additive.
The USEPA regulates the use of limonene when used in cleaning agents and
pesticides.
Aside from regulatory requirements regarding product registration, research
into other
applicable regulations revealed that d-limonene is not specifically listed as
a regulated
waste by the Resource Conservation and Recovery Act (RCRA), Title III of the
Superfund Authorization and Reclamation Amendments (SARA), or the Clean Air
Act
Amendments of 1990 (CAAA). In addition, neither the National Institute of
Occupational
Safety and Health (NIOSH) nor the American Conference of Governmental
Industrial
Hygienists (ACGIH) have developed "Permissible Exposure Limits" (PELs) for
this
material. From these above human safe and ecologically sound perspectives, one
can see
that d-limonene is a viable alternative to dangerous petroleum based solvents.
SEAR is the acronym for Surfactant Enhanced Aquifer Remediation. SEAR-NB is a
concept of SEAR at neutral buoyancy, where neutral buoyancy is an effective
resultant
density of the combined co-solvent and DNAPI.,, which resists downward
vertical
migration. SEAR-NB is well documented by Shook ( 1998) and by Kostarelos (
1998).
The SEAR-NB method comprises adjusting at least one of the following design
parameters:
a
CA 02327443 2000-11-27
(i) the density of the micro-emulsion;
(ii) distance between injection of the chemicals and extraction
of the micro-emulsion;
(iii) the rate of injection of the chemicals and
(iv) the viscosity of the micro-emulsion
which minimizes the vertical mobility of the micro-emulsion and improves
extraction.
The method further includes sampling the aquifer for at least one of the
following
environmental factors of the aquifer:
(i) horizontal permeability;
(ii) vertical permeability;
(iii) aquifer thickness;
(iv) relative permeability to the micro-emulsion phase
(v) relative permeability to the water phase,
and adjusting at least one of the design parameters to reduce vertical
migration of the
contaminant. The density of the micro-emulsion is adjusted by injecting
chemicals in the
form of a chemical composition which is sufficiently less dense than the dense
non-
aqueous phase liquid to reduce the density of the resulting micro-emulsion. To
accomplish this reduction in effectual density of the DNAPL, water miscible
alcohol has
been proposed by Shook (United States Patent 5,993,660) as the co-solvent and
is thus
mixed with an undefined surfactant. The alcohol co-solvent is miscible with
the DNAPL
and the resultant density of the alcohol-DNAPL is lowered and an undefined
surfactant
creates a micelle.
Ternary phase diagrams for various alcohol-DNAPL systems have been developed
by a
number of researchers { Peters and Luthy, 1993; Brandes 1997; Falta, et al
1996; Lunn
and Keeper 1996, 1997) and have shown that ternary phase diagrams can predict
performance. If alcohol concentrations are kept below the binodal curve, the
primary
removal mechanism is DNAPL dissolution. If it is increased above the binodal
curve, the
interfacial tensions reduce towards zero, resulting in complete miscibility,
and therefore
complete mobilization in water. Whether the miscible mixture of alcohol
mixture will be
more or less dense than water will depend upon the initial DNAPL density and
the
relative proportion of components in the system.
One of the inventive ideas of this invention is specifically avoiding the use
of an alcohol
and instead, using d-limonene to avoid the binodal curve phenomena associated
with an
alcohol when reducing the effective density of the DNAPL. d-Limonene is a non-
polar
substance, whereas alcohols are polar substances and as such, d-limonene does
not reduce
interfacial tensions of DNAPL-water towards zero, thus does not result in
miscibility of
the DNAPL in water, as alcohols do. This provides an extra measure of safety
in-situ, by
not promoting the mobilization of the DNAPL in water and eliminates the
potential of an
alcohol-DNAPL downward vertical migration or horizontal migration in the
aquifer.
lz
CA 02327443 2000-11-27
d-Limonene compares favourably with alcohols as a neutral buoyancy enhancer
(or
density lowering agent). The inherent problems of lowered interfacial DNAPL-
water
tensions associated with an alcohol is alleviated. As d-limonene is a non-
aqueous phase
liquid, it is strongly preferential to the DNAPL, causing swelling of the
DNAPL and
lowering the effective density. The chart below illustrates the specific
gravity of three
common remedial alcohols, methanol, isopropyl alcohol, and ethanol as opposed
to d-
limonene and a common DNAPL such as trichloroethylene.
Chemical Com ound S ecific Gravi
Trichloroeth lene 1.456
TCE
Ethanol 0.790
Tso ro 1 Alcohol 0.786
Methanol 0.792
d-Limonene 0.840
Based upon d-limonene's low toxicity, its ability to reduce the effective
density of
DNAPL for SEAR-NB type systems in contaminated aquifers, and owing to its
biodegradability, d-limonene is a superior and desirable co-solvent.
d-Limonene in this invention is present at a level from about 0.50 % to 80.00
% volume,
based upon the total volume of the final aquifer DNAPL geo-chemical remedial
composition. Preferably, the ingredient should be present at a volume from
5.00 % to
40.00 % volume. Most preferably this ingredient should be present about 25.0
volume.
Water forms the remainder of the final ingredient of this final aquifer DNAPL
geo-
chemical remedial composition invention. As water was added a diluant with the
chelant
in the first stage of manufacture of this invention at a most preferable range
of 20.0 % to
volume of the final aquifer DNAPL geo-chemical remedial, water is added as the
balance
to comprise 100.00% of the final aquifer DNAPL remedial composition . Water
can be
present from about 10 to about 95% volume, based on the total weight of the
final aquifer
DNAPL geo-chemical remedial composition. Preferably it should be present from
about
5.0 to 85.0 volume %. Most preferably, it should be present in a total amount
of about
56.73 volume %.
13
CA 02327443 2000-11-27
METHOD OF MANUFACTURE:
Broadly, the aquifer DNA.PL geo-chemical remedial composition of this
invention
contains from 0.01 % to 10.0 % volume of a chelant, from about 0.10 % to about
10.0
volume of a phosphate, , from about 0.50 % to about 95.0 % volume of an non-
ionic
surfactant, from about 0.50 to about 80.0 % volume of a monoterpene and the
remainder
water.
The aquifer DNAPL geo-chemical remedial composition of this invention was
manufactured from the following steps:
First a chelant, of ethylene diamine tetraacetic acid-sodium salt was added
about 0.20%
to an initial volume of water about 20.0 %, under agitation to create the
first resultant
substantially homogeneous mixture.
Then about 1.17% by volume of the second ingredient, sodium hexametaphosphate
was
added under agitation to the first substantially homogeneous mixture to create
the second
resultant substantially homogeneous mixture.
Then under agitation, about 17.00 % by volume of the third ingredient, an
acetyl non-
ionic surfactant, was added to the second substantially resultant homogeneous
mixture to
create a resultant third substantially homogeneous mixture.
Then again under agitation the fourth ingredient, d-limonene, was added about
25.00
volume, to the third substantially resultant homogeneous mixture to create a
substantially
resultant fourth homogeneous mixture.
Finally the final ingredient, water was added, about 36.63 % volume to the
substantially
resultant fourth homogeneous mixture to create the final substantially
resultant
homogeneous mixture of this aquifer DNAPL gea-chemical remedial composition
invention.
COMPOSITION
The following composition is representative of this innovation.
Component
Ethylenediamine tetraacetic acid 0.20 (% by volume)
(sodium salt)
Water 20.00 (% by volume)
Sodium Hlexametaphosphate 1.17 (% by volume)
Non-ionic surfactant 17.0 (% by volume)
d-limonene 25.00 (% by volume)
Water 36.30 ~% by volume)
14
CA 02327443 2000-11-27
This aquifer DNAPL geo-chemical remedial composition is stable. It can de
diluted in
hard or soft water to form an aqueous dilution. It effectively solubilizes and
emulsifies
DNAPL contaminants from soil and from groundwater. The d-limonene co-solvent
portion is miscible with DNAPL and effects a lower density of the non-polar,
non-
aqueous phase liquid portion, thus resisting downward vertical migration in
the aquifer.
The non-ionic surfactant can be split into a resultant water-insoluble
fraction comprising
an aldehyde and the water-soluble fraction comprising an alkoxylated polyol.
Neither
fraction produced from the hydrolysis is surface-active, therefore micelle
formation is
removed and migrational controls in the aquifer are instituted. The
surfactant, terpene and
chelant portion of this embodiment are all biodegradable, while the phosphate
portion
assists in stimulating micro-flora.
ENVIRONMENTAL REMEDIATION APPLICABILITY
EXAMPLE I : Feeding Neat into an Area of Contaminated Ground
Generally, the geo-chemical solvent remedial composition of the present
invention can be
used to remedy an area of ground contaminated with DNAPL as follows:
Administering
through one or more perforated pipes that have been injected into the ground,
aquifer
DNAPL geo-chemical remedial composition of this invention can be slowly
introduced
into the perforated pipes to allow the composition to slowly penetrate into
the
contaminated soil. Several pore volumes of water are then added to the
perforated pipes
to follow behind the aquifer DNAPL geo-chemical remedial composition. Through
one
or more injected perforated pipes at an extraction location down flow from the
contaminated zone, the resultant solubilized DNAPL-monoterpene that has a
lowered
density from that of the original DNAPL, with the aquifer DNAPL geo-chemical
remedial composition of this invention and the pore volumes of water can be
extracted
through a suction pump mechanism or a submersible pump system. The resultant
solubilized DNAPL resists downward vertical migration into lower levels of the
aquifer.
EXAMPLE 2 : Feeding an Aqueous Dilution into an Area of Contaminated
Ground
Generally, the geo-chemical solvent remedial composition of the present
invention can be
used to remedy an area of ground contaminated with DNAPLs as follows: The geo-
chemical solvent remedial composition of this invention can be diluted from
one part
geo-chemical solvent remedial composition, to one part water up to 1 one part
geo-
CA 02327443 2000-11-27
chemical remedial solvent composition to twenty parts water to make an aqueous
solution. This resultant solution of water and aquifer DNAPL geo-chemical
remedial
composition can be administering through one or more perforated pipes that
have been
injected into the ground, the geo-chemical solvent remedial composition of
this invention
can be slowly introduced into the perforated pipes to allow the composition to
slowly
penetrate into the contaminated soil. Through one or more injected perforated
pipes at an
extraction location down flow from the contaminated zone, the resultant
solubilized
DNAPL with the aquifer DNAPL geo-chemical remedial composition of this
invention -
water solution can be extracted through a suction pump mechanism or a
submersible
pump system. The resultant solubilized DNAPL resists downward vertical
migration into
lower levels of the aquifer.
EXAMPLE 3: Feeding an Aqueous Solution into an Area of Contaminated
Ground and Splitting the Surfactant.
Generally, the geo-chemical solvent remedial composition of the present
invention can be
used to remedy an area of ground contaminated with DNAPL as follows:
Administering
through one or more perforated pipes that have been injected into the ground
aquifer
DNAPL geo-chemical remedial composition of this invention can be slowly
introduced
into the perforated pipes to allow the composition to slowly penetrate into
the
contaminated soil. Several pore volumes of water are then added to the
perforated pipes
to follow behind the aquifer DNAPL geo-chemical remedial composition. Through
one
or more injected perforated pipes at an extraction location horizontally or
vertically down
flow from the contaminated zone, an acid may be injected either in
concentrated form or
as a diluted aqueous acid, to form a reactive chemical barner. The acid of
this injected
chemical barrier will hydrolyze the non-ionic surfactant portion of this
aquifer DNAPL
geo-chemical remedial composition of this invention, splitting the hydrophilic
head of the
non-ionic surfactant away from the hydrophobic tail, of the non-ionic
surfactant. The
resultant water-insoluble fraction comprising an aldehyde and the water-
soluble fraction
comprising an alkoxylated polyol. Neither fraction produced from the
hydrolysis is
surface-active, so the monoterpene-DNAPL created by the aquifer DNAPL geo-
chemical
remedial composition are released from association with the surfactant of the
aquifer
DNAPL geo-chemical remedial composition. The monoterpene-DNAPL and the
hydrophobic fraction of the surfactant form a relatively water-insoluble phase
in the
aqueous stream that has a density lower than that of the original
contaminating DNAPL.
The resultant relatively water-insoluble phase DNAPL-monoterpene that has a
lowered
density than that of the original DNAPL, is resistant to downward vertical
migration in
the aquifer.
16
CA 02327443 2000-11-27
EXAMPLE 4: Feeding Neat or an Aqueous Dilution into Contaminated
Groundwater, and Splitting the Surfactant.
Generally, the geo-chemical solvent remedial composition of the present
invention can be
used to remedy an area of groundwater contaminated with DNAPL as follows:
Administering through one or more perforated pipes that have been injected
into the
ground, the aquifer DNAPL geo-chemical remedial composition of this invention
can be
slowly introduced as the neat form or in an aqueous dilution into the
perforated pipes to
allow the composition to slowly penetrate into the groundwater without the
addition of
pore volumes of water. Through one or more injected perforated pipes at an
extraction
location horizontally or vertically down flow from the contaminated zone, an
acid may be
injected either in concentrated form or as a diluted aqueous acid, to form a
reactive
chemical barrier. The acid of this injected chemical barrier will hydrolyze
the non-ionic
surfactant portion of this aquifer DNAPL geo-chemical remedial composition of
this
invention, splitting the hydrophilic head of the non-ionic surfactant away
from the
hydrophobic tail, of the non-ionic surfactant. The resultant water-insoluble
fraction
comprising an aldehyde and the water-soluble fraction comprising an
alkoxylated polyol.
Neither fraction produced from the hydrolysis is surface-active, so the
monoterpene-
DNAPL created by the aquifer DNAPL geo-chemical remedial compositior~,are
released
from association with the surfactant of the aquifer DNAPL geo-chemical
remedial
composition. The monoterpene-DNAPL and the hydrophobic fraction of the
surfactant
form a relatively water-insoluble phase in the aqueous stream that has a
density lower
than that of the original contaminating DNAPL. The resultant relatively water-
insoluble
phase DNAPL-monoterpene that has a lowered density than that of the original
DNAPL,
is resistant to downward vertical migration in the aquifer.
The invention now being fully described, it will be apparent to one of
ordinary skill in the
art that many changes and modifications can be made thereto without departing
from the
spirit or scope of the invention as defined in the following claims.
