Note: Descriptions are shown in the official language in which they were submitted.
s~
IMP~OVED METHO~ FOR THE SOLVENT
EXTRACTION OF POLYCHLORINATED BIPHENYLS
LOUIS L. PYTLEWSKI
EDWARD SO THORNE
BACKGROUND OF THE INVENTION
The commercial introduction of
polychlorinated biphenyls (PCBs) in 19~9 represented a
major breakthrough in the technology of dielectric
fluids. These compounds were found to have outstanding
thermal stability, resistance to oxidation, acids,
bases and other chemical agents, as well as excellent
electrical insulating characteristics making them ldeal
for applications in electrical capacitors and in high
performance electrical transformers. PCBs gained rapid
and widespread acceptance in the electrical industry.
In 1966, the discovery of PCBs in
environmental samples stimulated concern over, and
considerable research on their potential toxic hazards.
By the early 1970's those hazards had become well
recognized, and prompted major manufacturers of PCBs to
restrict sales to applications in closed electrical
systems. All production of PCBs was stopped in 1977.
During the 1970's the U.S. Environmental
Protection Agency (EPA) set out to develop guidelines
for control of PCBs. This effort culminated in
publication of a series of regulations on PCBs handling
and disposal requirements in the _ederal Regis~er on
May 31, 1979 and March 28, 1980. See also: "EPA's
Final PCB Ban Rule: Over 100 Questions and Answers to
~ 5~L49~i 1
Help You Meet These Requirements", Office of Toxic
Substances, EPA, Washington, D.C. (June 1980~. These
regulations cover the maintenance, operation, and
disposal of three classes of transformers, as follows:
Below 50 ppm - Noncontaminated [Non-PCB
Transformer]
50 ppm to 500 ppm - PCB Contaminated
Transformer
Above 500 ppm - PCB Transformer;
the higher the concentration of PCBs in the
transformer, the stricter the regulations.
These regulations have had particular impact
on electrical u~ility companiès. Although PCBs have
not been used extensively in general purpose
distribution transformers, cr~ss contaminatlon in
transformer manufacturing and service facilities over
many years has resulted in widespread appearance of
relatively small amounts of PCBs in many transformers.
The development of acceptable procedures for
operating under the EPA regulations has become the
subject of intensive research. The principal effort
has been directed toward development of safe and
effective PCB disposal techniques. Until recently the
only accepted methods o disposal were by dumping in
rigidly designed safe land fills or burning in
carefully controlled high temperature incinerators.
However, lack of approved facilities has limited
disposal capacity by these methods. Such methods are
also wasteful and result in permanent decommissioning
of transformers or destruction o~ valuable and
relatively scarce dielectric 1uids.
Because of their remarkable stability PCBs
are not only resistant to biological degradation bu~
)5~5
also to most of the well-known chemical decomposition
methods. So~e che~ical decontamination methods which
have reportedly produced posi~ive results suffer from
one or more serious limita~ionsO The most widely
reported chemical me~hods for decomposing PCBs employ
extremely reactive sodium compounds. Sodium in liquid
ammonia has long been used for this purpose
in analytical chemical laboratories. Other
decomposition processes for PCBs which are claimed to
be effective employ high surface sodium,
sodium/n~phthalene, and sodium~naphathalide. These
processes share some notable drawbacks. The reagents
are difficult to prepare, expensive to ship and
unstable in s~orage. Moreover, active sodium compounds
are sensitive to oxygen and to water and therefore
cannot be used reliably under field conditions.
A few combined chemical/physical me~hods of
PCB disposal have also been reported. See: O.
Hutzinger, et al., "The Chemistry of PCBs", CRC Press
Cleveland, Ohio, (1974). For example, radiation can
destroy PCBs under certain conditions, but the process
is slow, ineficient and not readily adap~able to field
use. Some polymers,such as chloroprene derivatives,
have been used to absorb PCBs from oil but ~hese also
apparently have limited effectiveness because of very
low absorption capacity and very slow absorption rate.
During the past several years the Franklin
Research Center of the Franklin Institute,
Philadelphia, Pennsylvania has developed a proprietary
system for stripping the chlorine substituents from
PCBs, thus rendering them non-toxic and readily
disposable. More specifically, Pytlewski, Krevitz and
Smith, in their United States Patent,
s
No. ~1,337,368, discloses and c]aims a method for the decomposition
of halogenated organic compounds, especially PCBs, which represents
a significant advance over the aforementioned methods of the
prior art. The decomposition reagent used in practicing that
method is produced by reacting an alkali metal, a liquid reactant,
such as a polyglycol or a polyglycol monalkyl ether, and oxygen.
This reagent produces virtually complete dehalogenation of a
variety of halogenated organic compounds, simply by mixing it with
the halogenated compound in the presence of oxygen.
In United States patent No. 4,400,552 there is described
and claimed another invention by the same inventors based upon
the discovery that decomposition of halogenated organic compounds
may be carried out using a reagent produced by the reaction of an
alkali metal hydroxide (rather than an alkali metal), a liquid
reactant, such as a polyglycol or a polyglycol monalkyl ether,
and oxygen. This decomposition reagent gives results which are
comparable to those obtained with the method described in the
earlier patent referred to above.
The reagents of the aforesaid patents
_ 4 _
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are collectively referred to hereinafter as NaPEG
reagents, or simply NaPEG.
The development of the NaPEG reagents has
made it possible to remove PCBs from fluids
contamina~ed ~herewith, as well as to decompose PCBs in
a safe, eficien~ and efecti~e manner.
SUMMARY OF THE INVENTION
In accordance wi~h the present invention,
~here is provided a process for reducing the level of
PCBs in a dielectric fluid by extracting with one or
more polyethylene glycols ~PEG~ By so doing the PCB
level of the fluid may be reduced to to below 50 ppm.
The process may be used to advantage in converting PCB
Contaminated Transformers to Noncontaminated
Transformers.
No specially designed equipment is required
for the practice of this invention. The estima~ed cost
of installation, opera~ion, and maintenance of the
process is less than the cost of replacement of the
dielectric fluid. Reduction of PCBs to an acceptable
level may be accomplished in about one to two weeks,
and the treated oil meets current ASTM standards.
The present process is applicable to
transformer sizes above 500 KVA through the largest EHV
power transformer, and to loaded and energized
transformers having oil temperatures between about 40C
and 95C.
Other advantages of the process are that the
chemical agents used are compatible with ~ransformer
materials, and that the toxic materials isolated in the
course of carrying out the process, upon further
treatment, may be rendered non-toxic, allowing for easy
1 `~
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5~5
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disposal thereof. The hazard potential in carrying out
the process is quite small since there is minimal
contact with contaminated oil or vapor during
ins~allation and opera~ion.
The present invention satisfies the criteria
set forth in the recent publication of the Electrical
Power Research Institute (EPRI), XFR 5592, Augus~ 22,
1980, and thus constitutes an appropriate procedure for
reducing PCBs in field-installed transformers to ~he
Noncontaminated level under the EPA regulations.
In accordance with o~e aspect of the present
invention, there is carried out a continuous,
multi-stage extraction of PCB's from fluids
contaminated therewith using polyethylene glycols
(PEG), which have been determined to have a selective
attraction for PCBs. The process of ~he present
invention is universally applicable to all known PCBs
and PC~-con~aining oils, including, but not limited to 9
the widely used Inerteen- and Pyranol-typesO This
process has the advantage over the acetonitrile
extraction process recommended by the Environmen~al
Protection Agency that it does not extract the
aliphatic hydrocarbon components o the transformer
fluids or other contamina~ed fluid, which complicates
the analysis of acetonitrile-extracted PCB components.
The polyethylene glycol extraction of PCBs
from transformer fluids or other liquids according to
this invention is preferably followed by a second
extraction of the PCBs from the PEG solution with
cyclohexane or a similar non-polar solvent. The
concentrated and isolated PCBs thus obtained may then
be decomposed by techniques known to the art to remove
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the chlorine substituents from the PCBs, rendering them
non-toxic and readily disposable.
The present invention also provides a means
for rApidly and easily determining the concentration of
S PCBs in a given sample of dielectric or other fluid.
This is accomplished by first extracting the PCBs from
the transformer fluid with polyethylene glycol,
subsequently extracting the PCBs from the polyethylene
glycol solution by cyclohexane extraction, as described
above, and thereafter analyzing the PCB-cyclohexane
extract by gas chromatography-electron capture
(g.c.-e.c.) to determine its PCB concentration.
The extraction process of the present
invention is an improvement over previous technology in
that interference due to water present in the system is
largely eliminated. Indeed, the polyethylene glycol
extraction agent may contain up to 15% water by weight
and still cause no interference wi~h the present
process, since such an amount of water is
readily dissolved in the polyethylene glycol without
retaining appreciable amounts of PCBs, and can be
discarded therewith or removed, if desired. In
general, the possibil~y of water interfering with the
present invention when used to treat PCB-contaminated
hydrocarbon oils may be readily avoided. Water will
form a two phase system with hydrocarbon oils and may
be decanted therefrom, and high grade extraction agents
containing less than 2% water are commercially
available~
~he present invention is based upon the
unexpected discovery that polyethylene glycols, even
though immiscible with transformer oils or other
non-polar dielectric fluids, are capable of selectively
" ~Lf'20~ 5
dissolving PCBs in such fluids and removing them
without altering the essential composition of the oil.
Polyethylene glycols having a wide range of molecular
weights, i.e., both liquids and solids, are effective
for this purpose. For example, liquid polyethylene
glycol having an average molecular weigh~ of about 400
has been found to be very effective in extracting PCBs
from transformer oil. Lower molecular weight
polyethylene glycol is also effective. On the other
hand, solid polyethylene glycol, such as Carbowax~,
having an averag~ molecular we'ight of about 20,000 is
also very effective in extracting PCB's from
transformer oil, as are solid polyethylene glycols of
even higher molecular weight.
It has been found, moreover, that
polyethylene glycol, whether liquid or solid, is able
to selectively remove about 25 to 35~O of the content of
PCBs in a transformer oil in a single extraction and
that the PCBs may be removed substantially completely
in about 3 to 8 extractions, depending upon the
particular PCB-type involved and certain other factors.
Moreover, the presence of water in the oil to be
treated does not appreciably interfere with
the polyethylene glycol extraction, nor is there any
significan~ contamination of the treated oil by the
polyethylene gl'ycol. It is preferred that about equal
volumes of polyethylene glycol and oil be employed in
order to achieve the most eficient extraction,
although higher proportions of polyethylene glycol up
to about 3:1, or lower proportions of as little as 1:3
may be employed with success. The number o
extractions necessary will depend on the PCB level in
the oil to be treated. To convert a transformer from
~ 2CI ~
the PCB Contamina~ed Transformer classification to the
Noncontaminated classification, at 25% to 35%
extraction efficiency with each extraction, will
generally require from about 3 to about 8 extractions.
Having completed the primary extraction of
PCBs from the transformer oil or other dielectric
fluid, it is desirable to carry out a secondary
extraction of PCBs from the PEG~PCB solution by the use
of cyclohexane or a similar solvent. In this way the
PCBs are removed from the polyethylene glycol which may
then be recycled for a second primary extraction, and
so on, until all PCBs are removed.
The present ex~raction process is fully
operative at ambient temperatures or at the normal
operating temperatures of electrical transformers in
the range from about 40 to about 95C. The process of
the present invention can be conducted on an operating
transformer without shut--down, for example, by treating
fluid drawn from the transformer.
The cyclohexane-PCB extract may be processed
further in various ways depending upon the desired
result. It may be analy~ed for PCB content by
conventional gas chromatography-electron capture
detection techniques. Inasmuch as the cyclohexane
extraction has been found to effect substantially
quantitative removal of PCBs from the
polyethylene glycol-PCB solution, the PCB content of
the original transformer oil may thus be reliably
determinedO
The PCBs present in the cyclohexane solution
may be rendered non-toxic by any suitable means known
to the art. It is preferred in the process of the
present invention to accomplish this by dehalogenating
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the PCB using NaPEG reagents, which, as previously
mentioned, include a family of chemical derivatives of
alkali metal (or alkali metal hydroxide) and liquid
reactants, such as polyethylene glycol. These reagents
are produced from relatively low cost raw materials
without significant manufacturing problems; and they
are stable in the presence of air and water, easily
shipped and relatively safe. They present no
flammability or dangerous decomposition hazards (over
one year storage), but are highly basic (similar
alkalinity to 0.l N sodium hydroxide).
The dehalogenation properties of the NaPEG
reagents are remarkable. They can be used to
dehalogenate PCBs (and many other halogenated
materials) in concentrated or dilute form.
Dehalogenation of PCBs, for example, occurs in a few
minutes at temperatures on the order of 100C. using
approximately stoichiometric quantities of reagent.
Reaction also occurs, albeit more slowly, at ambient
temperatures. Reaction products from dehalogena~ion
include sodium chloride and various oxygenated aromatic
compounds ~ha~ are easily disposable under
environmentally safe conditions~
BRIEF DESCRIPTION OF TUE DRAWING
~5 Fi~. l is a flow diagram of a process for the
extraction of PCBs from the oil of an operating
electrical transformer.
As illustrated in the drawing, transformer
oil is taken off from an operating transformer 11 as a
stream (indicated by arrow 13) and passed by means of
pump P through a filter 15 for removal of solids3 ~hen
a dryer 17, and thereafter to an extraction column 19.
Polyethylene glycol is fed from surge tank 20 to the
extraetion column counter-currently, and the resulting
PCB-rich polyethylene glycol solution is drawn off at
the bottom of ~he extraction column, and pumped from
surge tank 21 together with cyclohexane from surge tank
23 into a mixer-extractor 25 from whence the mixture is
delivered to separator 27 where the mixture separates
into two liquids phases. From the separator, the lower
phase consisting essen~ially of polyethylene glycol
freed from PCBs and cyclohexane`is recycled through
surge tank 20 to extraction column 19 (as indicated by
arrow 29). The upper phase from separator 27,
consisting essentially of a cyclohexane-PCB solution,
is heated to evaporate cyclohexane, which is recycled
to surge tank 23 for further use, and the remaining
product, consisting essentially of PCBs, is ~ransferred
to reactor 31 containing a NaPEG reagent (from a source
not shown), and the chlorine substituents are stripped
from the PCBs. The resulting decomposition mixture,
containing sodium chloride-and various oxygenated
derivatives of ~he PCBs, are discarded.
Polyethylene glycol and cyclohexane needed
initially or as make-up may be added to surge tank 20
and to surge tank 23, respectively.
Transformer oil mixed with some polyethylene
glycol is drawn off at the top of extraction column 19
and sent to a separator 39 where the polyethylene
`glycol is separated and recycled to the extraction
column. The product from separator 39, which is
transformer oil containing no more than 50
ppm PCB is returned to the ~ransformer. In this way
the PCB content o the transformer oil can
s
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be reduced to, and maintained at the desired acceptable
concentration .
All of the e~uipment utilized in the
above-described process is conventional and
commercially available and requires no modification or
special design or construction. The unit operations
are all standard and well known. The system as a whole
is connected to the transformer through conventional
valving and conduits.
The secondary ex~raction of PCBs with
cyclohexane permits recyling of the primary extractant
with minimal processing and expense.
The detoxification of the PCB content of the
secondary extract by the use of the NaPEG reagents
according to the process of the United States PatentS
Nos. 4,337,368 and 4,400,552,
referr~d to above completes an efficient and low cost
system of ridding contaminated fluids of toxic PCBs.
The preceding description is of a presently
preferred embodiment of the invention wherein PCBs are
removed from an operating transformer by extraction,
separation and decomposition of the PCBs in separate
unit processes. With a simple modification, this
process may also be applied in a one-step procedure to
transfor~ers in storage, or to any PCB-contaminated
functional fluid stored in drums. In this modification
a composition comprising a mixture of the polyethylene
glycol extraction agent and the NaPEG rea~ent is added
with agitation to the functional fluid in a container,
and the container is allowed to stand for an extended
period of time, on the order of three months, with
occasional venting to permit the introduction of air
into the container. The polyetllylene glycol
}r ,
l~j
5~5
selectively extracts PCBs from the function~l fluid and the NaPEG
reagent introduced with the polyethylene glycol reacts with the
PCBs and oxygen from the air to dehalogenate the PCBs.
In order to form a s~able dispersion of the composition
in the fluid undergoing treatment the aforesaid composition should
contain a suitable surfactant of the general formula,
H-O(-C~2-CH2-O)x-R, wherein x is > 2 and R
represents an alkyl group having 12 or more carbon atoms, an
aral~yl group, an ester residue, or a polypropylene glycol group.
Suitable surfactants of the above formula include Igepa ~, Pluronic~
or Triton~. If desired, these materials may be used in the
production of the NaPEG reagent.
The amount of composition employed may vary depending on
the PCBs content of the func~ional fluid being treated. Satisfactory
results have been obtained using about 2 percent of a 1:1 PEG to
NaP~G composition9 based on the volume of fluid to be treated. The
spent composition and dehalogenation reaction products are easily
removed from the treated functional fluid, e.g. by washing with
water.
The modified process just described provides a safe,
efficient and effective way for reducing the PCB content of
dielectric fluids of PCB Contaminated Transformers to below 50 ppm.
The principal benefit of this modified process is that it obviates
significant investment in chemical processing equipment.
The operation of the present invention will be further
understood by reference to the following
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specific examples.
The concentrations of PCBs reported in the
examples were determined by comparing the areas of
selected peaks from the gas chromatographs of
cyclohexane extracts of unknown concentration with
those of a standard solution of PCBs (either Pyranol or
Inerteen) in cyclohexane. So long as the peak areas on
the chromatographs were on the same order of magnitude
they were considered suitable for comparision.
In order to quantitatively calculate the PCB
concentration o~ a particular unknown sample, three to
five representative peaks were selected from the
chromatograph of the unknown sample as a reference for
comparision and the total area of each peak was
determined and compared with the corresponding peaks on
the chromatograph of the standard solution. Thus, for
example, if the total area of the selected peaks for
the unknown sample was measured to be 50% of the
corresponding peaks for the standard, the concentration
of PCBs in the unknown sample was determined to be 50%
that of the standard. In making these calculations
dilution effects were considered negligible inasmuch
the volume of the extraction agent employed and the
solution being extracted were equal. As previously
noted, PCBs are substantially completely removed from
polyethylene glycol by cyclohexane.
To evaluate the scientific acceptability of
the data used in making these calculations three to six
replications of the experiment were carried out for the
selected peaks, and the peak area data were subjected
to sta~istical analysis by the Chauvenet criterion and
all data were found to be acceptable.
~ s~s
EXAMPLE 1
A sample of comm~rcial transformer oil known
to contain 600 ppm Pyranol (PCBs) was treated by adding
equal volumes o~ the oil and polye-thylene glycol
(average M.W. 400) to a large beaker and stirring the
mixture until equilibration was reached, generally a
minimum of 3 minutes. The immiscible mixture was then
transferred to a separatory funnel and the lower
polyethylene glycol-PCB phase was drawn off and treated
with an equal volume of cyclohexane with stirring for a
minimum of 3 minutes. A second mixture was formed and
was separated as before, except that the
cyclohexane-PCB layer was the upper phase in the
separatory funnel.
The cyclohexane-PCB solution thus obtained
was then analyzed by a conventional gas
chromatograph-electron capture (g.c.-e.c.) detector and
compared with the chromatogram of a standard solution
of known concentration of Pyranol in cyclohexane. This
extract was found to contain 152 ppm of Pyranol. This
represents approximately 25% of the PCBs in the
original sample of the transformer oil, inasmuch as
equal volumes were used in the ex~ractions and
cyclohexane effects substantially quantitative removal
of PCBs from polyethylene glycol.
EXAMPLE 2
A solution of Pyranol in mineral oil was
prepared containing approximately 1000 ppm of PCBs. A
sample of this standard solution was extracted with
polyethylene glycol (average M.W,400) which, in turn
was extracted with cyclohexane, as described in Example
1. The cyclohexane extract was analyzed by g.c.-e.c.,
~,~OS~95
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as in Example 1, and it was determined that the
recovery was 24.3% of the Pyranol present in the
prepared solution. At this rate, (according to the
equation set forth in Example 4, below) about 7 to 8
extractions would effect substantially complete removal
of the Pyranol from the mineral oil.
EXAMPLE 3
A determination was made of the amount of
Inerteen (a proprietary PCB), which can be recovered
from an oil in a-~ingle extraction according to the
present invention.
A small amount (0.1g.) of Inerteen, was added
to 100 ml. of Nujol~mineral oil and agitated until a
homogeneous solution was obtained. The concentration
of Inerteen in the mineral oil was calculated to be
1162 ppm.
A 50 ml. sample of this solution was added to
50 ml. of polyethylene glycol (average M.W. 400) and
the immiscible mixture was stirred vigorously at room
temperature for about 3 minutes. Stirring was stopped
and a~ter separation of the layers 50 ml. of
cyclohexane was added to the lower (PEG) phase. This
second extraction was carried out for about 3 minutes
and the upper (cyclohexane) phas~ was separated and
analyzed by g.c.-e.c. as in Example 1 above.
When the chromatogram was compared to that of
a standard Inerteen solution containing 1069 ppm, it
was found that the percentage of recovery of the PCB on
this single two-step extraction was 25.7%.
EXAMPLE 4
The purpose of this experiment was to
determine the effect of water on the distribution of
PCBs between a polyethylene glycol-water mixture and
cyclohexane. This was intended to simulate a si~uation
in which the PCB~contaminated liquid undergoing
trea~ment contains water which would be transferred to
the polyethyleneglycol during extraction.
A standard solution of 106.9 ppm Interteen in
cyclohexane was prepared by quantitative dilution of a
stronger standard solution. An aqueous polyethylene
glycol solution (67% by volume water) was prepared and
a 5 ml. sample thereof was interfaced with an equal
volume of the jus-t described standard cy~lohexane-PCB
solution. The mixture was vigorously ~gitPted for
about 3 minu~es, after which t~e cyclohexane layer was
injected into the g.c./e.c. detec~or. Because equal
volumes of cyclohexane and extraction agent were used
there were no diIution effects to be compensated for in
the concentration calculations.
The percentage of PCB extracted (E) by the
cyclohexane is calculated from the equation:
E = 103 [l ~ ~m + l)-IT]
wherein D is the mole distribution ratio which is
defined by:
D = concentration of PCB in cyclohexane
~ concentration~~FPCB in water
and n represents ~he number of extractions which have
been performed. For the derivation of this equation,
see: Fritz and Schenk, Quantitative Analytical
Chemis~r~, at 348-49 (4th ed. ). It should be noted
that Dm~ as set forth above, relates to the
extraction o PCBs from water into cyclohexane. Once
5~
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Dm has been obtained for any particular system, the
number of extractions necessary to extract any given
percentage of the PCB into the extractant can be
determined.
In the present experiment it was found that
approximately 10 to 12% of the PCB present in the
system was retained by the water-PEG layer when an
extraction with cyclohexane was performed. This
corresponds to a Dm value of approximately 8 for this
system. Using this value in ~he above equation and
solving for n, it was found that three extractions are
required for esséntially complete removal of the PCB
from the water. It can thus be seen that additional
extractions will be required to achieve complete
extraction of PCBs from a system containing a
substantial amoun~ of water.
In this example, "essentially complete
extraction" was deemed to have been achieved when the
percentage of PCBs extracted exceeded 99.9%.
This example shows that even when the
original PCB-contaminated liquid (or the PEG extractant
agent)-contains substantial amounts of water, the PCBs
can be reduced ~o an acceptable level simply by
increasing the total number of extractions. As
previously noted, however, interference due to the
presence of water in the system may often be avoided.
~XAMPLE 5
A test was conducted to determine the utility
of solid Carbowax polyethylene glycol (average M.W.
20,000) in selec~ively extracting PCBs from an oil
medium.
A sample of hydrocarbon oil (500 ml.)
containing about 1472 ppm. of Inerteen was placed in a
i
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19 -
150 ml. beaker and about 75 g. of Carbowax (average
M.W. 20,000) was added at room temperature and slurried
with the oil. Fractions were removed at timed
intervals and analyzed for PCB conten~. The
oil-polyethylene glycol mixture was stirred continually
on a magnetic stirring apparatus at room temperature.
The oil had a density of 0.91 g/ml. The PCB content of
the oil dropped from an initial 1472 ppm to g57 ppm in
90 minutes~ This amounts to an extraction of about 35%
of the PCB content of the oil which compares favorably
with the efficiency of lower molecular weight
polyethylene glycols.
EXAMPLE 6
. .
Another test along the lines of Example 5 was
conducted by placing 200 ml. of Carbowax in a beaker
containing 200 ml. of a transformer oil having a PCB
concentration of about 200 ppm, The mixture was
stirred continually and a sample was removed after 30
minutes and analyzed for PCB content by g.c.~e.c. as
~efore. It was found that 41% of the PCB content of
the oil had been extracted.
EXAMPLE 7
.
A series of tests was conducted to determine
whether the polyethylene gly~ol extraction agent for
PCBs would itself contaminate the treated oil. Samples
were prepared of PCB-contaminated switch fluid not
extracted with polyethylene glycol, the same fluid
after ex~raction with PEG (average MoW~ 400) ~ and pure
polyethylene glycol (average M.W. 400). The extraction
was carried out by adding 50 ml. of polyethylene
glycol to 50 ml. of the oil and agitating the mixtures
5~
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vigorously for three minutes.
T'ne presence or absence of polyethylene
glycol was determined by the presence or absence of the
characteristic OH band at 3700-3200 cm~1 of the
S infrared spectrum. No polyethylene glycol was detected
in the extracted sample of oil, thus indicating that at
the detection limits of infrared spectroscopy the
extraction agent does not itself contaminate the oil.
EXAMPLE 8
A series of extractions of an oil containing
Inerteen with and without added water was run to
determine whether or not the presence of water mixed
with a treated oil would adversely affect the
extraction efficiency of polethylene glycol. Analyses
of the resulting extracts showed that the extraction
efficiency of polyethylene glycol i9 not appreciably
affected by up to about 15% water by weight in the PEG
phase.
Those skilled in the art will appreciate that
the procedures disclosed in the foregoing exampies are
merely illustrative and are capable of variation and
modification without departing from the spirit and
scope of the invention as defined in the appended
claims.
