Note: Descriptions are shown in the official language in which they were submitted.
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TREATMENT OF LIQUID WITH OILY CONTAMINANTS
This invention relates to products for the treatment of contaminated liquid by
contact with an adsorbent material. It has particular application in the
treatment of liquids
to remove oily contaminants. It uses technology disclosed in our International
Patent
Publication Nos: WO 2007/125334, WO 2008/047,132, and WO 2009/050485; and
British Patent No: GB2470042.
Adsorbent materials are commonly used in liquid treatment apparatus. Carbon-
based such materials are particularly useful, and are capable of regeneration
by the
passage of an electric current therethrough. The use of carbon-based
adsorbents in the
treatment of contaminated water is described in the following papers published
by The
University of Manchester Institute of Science and Technology (now the
University of
Manchester) in 2004:
Electrochemical regeneration of a carbon-based adsorbent loaded
with crystal violet dye by N W Brown, E P L Roberts, A A Garforth
and R A W Dryfe
Electrachemica Acta 49 (2004) 3269-3281
Atrazine removal using adsorption and electrochemical regeneration by
N W Brown, E P L Roberts, A Chasiotis, T Cherdron and N Sanghrajka
Water Research 39 (2004) 3067-3074
The present invention adapts the techniques disclosed in the Patent
Publications
and Applications referred to above to remove oil contaminants from aqueous
liquids.
So contaminated liquids appear in many fields of activity, one of which is the
nuclear
industry where the disposal of radioactive oils and oily wastewaters is a
major problem.
According to the invention a method of removing oil contaminants from aqueous
liquids comprises contacting the liquid with particles of a carbon-based
adsorbent
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material to form a layer of the oil contaminant on each particle, and
electrochemically
regenerating the adsorbent particles and recycling the particles in the liquid
to form an
additional layer of the oil contaminant on each particle. The particles can
then be
regenerated by electrochemical oxidation, normally after removal from the
liquid. In
the practice of the method the particles bearing the oil contaminant layers
can be
allowed to coalesce in the liquid into one or more solid bodies with voids
between the
particles into which bodies further oily contaminant is absorbed.
According to one aspect of the present invention there is provided a method
of removing oil contaminants from aqueous liquids comprising contacting the
aqueous liquid with particles of a carbon-based adsorbent material to form a
layer
of the oil contaminant on each particle, and electrochemically regenerating
the
adsorbent particles by the application of a charge in the range 5 to 50 c/g so
as to
leave a layer of the oil contaminant on each particle, recycling the particles
in the
liquid to form an additional layer of the oil contaminant on each particle,
and
regenerating the particles by electrochemical oxidation by the application of
a
charge of at least 4,500 c/g.
To treat a neat oil or a concentrated oily wastewater, it can be desirable to
dilute
the oil with water. Since oils are usually not miscible with water, it is
necessary to treat
the oil with an emulsifying agent. Of course, soluble oils which mix readily
with water
will not need such an addition. The emulsifying agent is likely to be an
organic
polymer of some description, but any organic emulsifying agent could be used.
An
organic emulsifying agent is recommended as this will be destroyed in the
regeneration
process.
In one particular application of the invention, the process can be used to
treat
radioactive contaminated waste oil or oily wastewater. In this application,
the aim is to
destroy the oil whilst leaving the radioactive particles in the aqueous phase.
The
generation of radioactive oils and oily wastewaters is an issue for the
nuclear industry
for which there is currently no satisfactory treatment solution. Existing
cementation or
vitrification processes are unable to produce stable matrices when oil is
present in
anything other than low quantities. By using adsorption coupled with
electrochemical
regeneration, it is possible to destroy the oil component leaving the
radioactive particles
in the water. Radioactive particles present in water can be treated using
existing
technologies.
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The method of the present invention is well suited to the treatment of
individual
quantities of liquid in a batch rather than in a continuous treatment process.
When so
practised the contaminated liquid is delivered to a treatment reservoir
containing the
carbon based adsorbent material in the form of a bed of material at the base
of the
reservoir. The bed is agitated for a period to distribute the adsorbent
material in the
liquid and adsorb contaminant therefrom, at the end of which period the
agitation
ceases, allowing the bed of material to settle. During this settlement period
the
adsorbent will separate from the liquid. The degree of separation depends upon
the
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length of time allowed. It is possible to adjust the time scale according to
the nature of
the liquid being treated. The adsorbent is then regenerated, during or after
settlement,
by passing an electric current through the bed to release from the adsorbent
gaseous
products derived from the contaminant in bubbles rising through the
decontaminated
liquid in the reservoir, which is then removed. The liquid can of course be
removed
before the adsorbent is finally regenerated. At different stages of the
regeneration
period, the current can be adjusted. For example, at the beginning of the
regeneration
period, only a very thin layer of the adsorbent will have settled so a smaller
current is
required than later in the regeneration period when substantial settlement has
occurred.
In the above described method adsorption occurs within the regeneration zone
as
well as the adsorption zone, facilitating a compact and potentially mobile
apparatus. It
also allows for a larger regeneration zone. An increase in the size of the
electrodes
would be beneficial for treatment liquid containing a high concentration of
contaminant.
Particular advantages of the above method are that it allows a treatment cycle
to
be selected for the particular liquid to be treated. The method allows the
steps of
agitating the bed and allowing it to settle, and of regenerating the
adsorbent, to be
repeated to remove further contaminant from the liquid prior to its removal.
Put another
way, the degree of decontamination of the liquid can be monitored, and the
method
adapted accordingly. It will also be appreciated that the relative sizes of
the
regeneration and adsorption zones can be varied according to the treatment
required.
The quantity of adsorbent that is added to the tank can be adapted to type and
load of
contamination present in the liquid. The ability to modify the method, the
quantity of
adsorbent and the relative sizes of adsorption and regeneration zones gives a
process
with significant flexibility.
In the method of the invention, before a repeated adsorption stage the
adsorbent
is not fully regenerated, but retains oil or oily matter on its surfaces. In
each repeated
stage additional layers of oil or oily matter are adsorbed. This partial
regeneration can
be accomplished by passing a much lower charge; 50 coulombs per gram or less,
through the adsorbent, compared to that required for full regeneration;
theoretically
around 5,400 c/g for =expanded intercalated graphite.
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Preferred adsorbent materials for use in the method of the invention comprise
unexpanded intercalated graphite, preferably in powder or flake form. The
material
may consist only of unexpanded intercalated graphite, or a mixture of such
graphite
with one or more other adsorbent materials, as described in British Patent No:
GB2470042 referred to above. Individual particles of the adsorbent can
themselves
comprise a mixture of more than one adsorbent material. It can be appreciated
that any
conducting material could be used.
In this preferred method, the bed of adsorbent material is normally agitated
by
the delivery of fluid to the base of the bed. The fluid will normally be a
gas, such as air,
but in some circumstances a liquid can be used. The liquid may be neutral such
as
water, or may be the contaminated liquid itself as or as part of its delivery
to the
reservoir. In other words, the contaminated liquid can be delivered to the
treatment
reservoir as part of the agitating process, at least in an initial
decontamination stage. If
a subsequent decontamination stage is required, a different agitator fluid,
such as air,
can be used. The agitating fluid can itself include a treatment component or a
component to be treated if required.
Apparatus for carrying out the preferred method can be simply designed to
enable the method steps to be carried out. The apparatus comprises a reservoir
for the
liquid having an upper and a lower section. The reservoir will contain a
particulate
adsorbent material, preferably of the kind referred to above, capable of
electrochemical
regeneration, and in the form of a bed supported in the lower section at the
base of the
reservoir. An agitator is installed for agitating the bed to distribute the
particles in
liquid contained in the reservoir including the upper section, and electrodes
are disposed
from opposite sides of the lower section for delivery of an electric current
to pass
through the bed of particles. The agitator will normally comprise a chamber
under the
bed with discharge orifices directed upwardly therefrom into the bed, and
means will be
provided for delivering fluid under pressure through the orifices into the bed
to
--, distribute the bed particles. Typically, the agitator will comprise a
plurality of nozzles,
for example in the form of a manifold, for directing fluid under pressure
upwards into
the bed of particles. It could be in the form of a chamber with a porous plate
above.
The agitator can be provided with means for connecting it to an external
source of
pressurised fluid, but could be quite independent with a source of pressurised
fluid
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being installed in the agitator itself This provides for the possibility of
the agitator
being installed in an existing reservoir to treat contaminated liquid on site.
Provided the
agitator dimensions are compatible with those of the reservoir, the agitator
can be
installed and the bed of particles formed thereover, prior to delivery of the
contaminated
liquid, from above or below the bed of particles.
An additional means for agitation of the content of the reservoir can be
included
in the form of a mechanical mixer with the extra function of preventing
coagulation of
the adsorbent material and treatment liquid in the upper section of the
reservoir.
Coagulation can prove a problem as it entraps the agitation bubbles, reducing
the
density of the adsorbent material and therefore causing it to float. This
reduces the
efficiency of adsorption and can cause incomplete separation. This can be a
problem
associated with the presence of, for example, a surfactant or oil in the
liquid to be
treated. However, with oil contaminants coagulated particles can create bodies
with
voids which absorb, rather than adsorb, further contaminant from the liquid.
In a
preferred embodiment of the experiment, the mixer is positioned within an
upper
section of the reservoir and attached to a lid or cover if used, but it could
be
incorporated anywhere in the adsorption section of the chamber. A mechanical
mixer
can also be used to fluidise the bed as an alternative to the use of
pressurised fluid. This
could be necessary when the contaminated liquid is of a nature that should not
be
exposed to bubbles; for example, foaming agents or highly volatile agents.
Generally, the reservoir in apparatus for use with the invention will have a
substantially uniform horizontal cross-section, with the bed of adsorbent
particles
extending across the entirety of that cross-section. However, the cross-
sections of the
upper and lower reservoir sections do not have to be the same, and
particularly for
relatively large quantities of lightly contaminated liquid, the bed of
adsorbent material
can be defined in a lower section of smaller cross-section than the upper
section, and
into which the adsorbent material flows as it settles. In this embodiment, the
reservoir
can then take the form of a hopper with an intermediate section between the
upper and
lower sections around which the reservoir wall or walls converge towards the
lower
section in which the adsorbent bed is formed.
In the practice of the method using the above apparatus, when the agitated
adsorbent bed material has been allowed to settle, it is regenerated by
passing an electric
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current through the bed. This current is created by the application of a
voltage between
electrodes on opposite sides of the bed. Normally, the cross-section of the
bed or lower
section of the reservoir will be square or rectangular, with the electrodes
disposed on
opposite sides of the lower section. A plurality of electrodes can be disposed
along
each of these sides. For example, in a reservoir, having a uniform rectangular
cross-
section of 200 x 100cm, 30 electrodes might be disposed along each of the
longer
opposite sides. Multiple electrodes can be installed horizontally to allow
different
currents to be applied at different heights in the bed during regeneration.
The above and further features of the invention will be apparent from the
following description given by way of example, of apparatus in which the
method may
be practised. Reference will be made to the accompanying schematic drawings
wherein:
Figure 1 is a perspective view of the apparatus;
Figure 2 is a top plan view of the base of the reservoir in Figure 1, upon
which a
bed of adsorbent is supported;
= Figure 3 is a perspective view of a device for supporting a fluidized bed
in
apparatus for use in the practice of the invention;
Figure 4 is a perspective view of an alternative form of apparatus for use in
the
practice of the invention;
Figure 5 is a top plan view of an alternative base of the reservoir of Figure
1,
below the level of the distribution plate, and showing an alternative
arrangement
of regeneration electrodes; and
Figures 6 and 7 illustrate the use of multiple cells in the base of apparatus
for
use in the practice of the invention.
Figure 1 illustrates a simple tank 2 of rectangular horizontal cross-section.
In
the lower section of the tank a bed of particulate adsorbent material is
supported on a
plate 6. Beneath the plate 6 is a chamber 8 for receiving a fluidising medium,
such as
air, from inlet pipe 10.
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Figure 2 is a horizontal cross-sectional view of the lower section 4 of the
tank 2,
specifically showing the plate 6 and the inlet pipe 10. Figure 2 also shows
the openings
12 in the plate for the passage of fluidising medium from the chamber 8 below.
On the
opposite longer sides of the plate 6, and extending upwardly therefrom, are
two banks
14 of electrodes 16. The bed of adsorbent material is supported on the plate 6
within
the walls of the container 2, between the banks 14 of electrodes 16.
The adsorbent material used in the practice of the present invention is carbon
based, and provided in particulate form that can be readily fluidised within a
body of
liquid. Preferred adsorbents are those disclosed in the Patent Publications
and
Applications referred to above. In use of the apparatus of Figures 1 and 2,
contaminated
liquid is delivered to the tank 2 which is normally open at the top. The
adsorbent
material is then fluidised by delivery of a suitable medium through input 10
to distribute
the adsorbent material within the body of contaminated liquid then contained
in the
tank. The adsorbent takes contaminants from the liquid which attach to the
surfaces of
the adsorbent particles. After a predetermined period of time, the flow of
fluidizing
medium is stopped with the consequence that the adsorbent material settles on
the plate
6 between the banks 14 of electrodes 16. At this point the decontaminated
liquid can be
removed through discharge 18 but its removal may be deferred. Its degree of
decontamination can be measured, and if this is now acceptable then it may be
removed.
If further decontamination is required, it is retained in the tank 2.
If required, additional agitation of the liquid in the upper section of the
tank 2
can be provided by a mechanical mixer indicated at 19. This can be a simple
paddle,
which will normally be sufficient if it is to function in conjunction with the
fluidising
medium delivered through the plate 6. If it is to be the only agitating
mechanism, then
it can be installed within or under the bed to urge the adsorbent material
into the upper
section, but it can be installed in the upper section itself. Particularly if
disposed at the
surface of liquid of the reservoir it can be used to coagulated particles.
Whether or not the decontaminated liquid has been removed, the adsorbent
material in the bed supported on the plate 6 can now be regenerated. This is
accomplished by passing an electric current through the material of the bed
between the
electrodes 16. This releases the adsorbed contaminants in the form of
carbonaceous
gases and water. The gases are released either through the open top of the
tank 2, or if
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the top is closed, through a separate exhaust duct 20, possibly for subsequent
treatment.
If the decontaminated liquid remains in the tank, the released gases merely
bubble
through it. Contaminated liquid retained in the tank after regeneration of the
adsorbent
material can of course now be further decontaminated by re-fluidization of the
bed to
distribute the particulate adsorbent once more within the liquid. This
sequence can be
repeated, with the degree of decontamination of the liquid being monitored
after each
treatment.
In the treatment of oils, oils in water or oily wastes at least two adsorption
stages
can be beneficial. In the first a single layer of oil forms on the adsorbent
particles.
However on regeneration, the capacity for adsorption remains similar, even if
insufficient charge is passed to achieve 100% electrochemical regeneration of
the
adsorbent material. After a charge has been passed through the adsorbent
during
regeneration, the surface of the adsorbent/oil is suitable for subsequent
layers of oil to
be adsorbed. Hence multi-layer adsorption appears to occur under these
conditions
when there is a high liquid phase concentration. In addition the presence of
oil causes
the adsorbent particles to stick together to create solid bodies or "balls".
These have
spaces between the particles which can then fill due to absorption, probably
caused by
capillary condensation. Oil concentrations on the adsorbent through a number
of
adsorptions after partial regeneration can at this stage reach 60% by weight.
After the treatment is concluded the adsorbent is removed and regenerated by
electrochemical oxidation. This removes the oil adsorbed on the surface of
the
material; any "balls" are destroyed; and the original particles are recovered.
After this
is achieved the particles can be reused.
In the apparatus of Figure 1 the bed of adsorbent material; the means for
fluidizing the bed to distribute the material within liquid in the tank; and
the electrodes
for regenerating the adsorbent after a decontamination treatment, are all
integrated in
the tank construction. However, it will be appreciated then, that the tank is
a mobile
decontamination unit that can be moved between sites where one or more batches
of
liquid must be contaminated, but where a permanent installation is not
required. If a
suitable tank is already on site, then it is the decontamination system; the
bed of
adsorbent and fluidizing mechanism that can be delivered separately. Such a
system is
illustrated in Figure 3 which, as can be seen, includes the same elements as
are present
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in the lower section of the tank 2 in Figure 1, with the exception of the
input 10 for the
fluidizing medium. This is replaced by a pipe 22, which can extend through the
top of
an on-site container for connection to a source of fluidizing medium. In use,
the
system shown in Figure 3 will be installed in the lower section of a tank,
with suitable
seals between the end boundaries 24 and the electrode banks 14 with the walls
of the
container, and the adsorbent material then delivered to rest on the plate 6
between the
electrode banks 14. Contaminated liquid is then delivered to the tank and the
treatment
followed, as described above. When the treatment is complete, the respective
tank can
be drained and the system removed together with or separate from the adsorbent
material on the plate 6.
Figure 4 shows an alternative apparatus according to the invention which is
suitable for smaller quantities of contaminated liquid; for example, for
experimental
use. The elements of the apparatus are essentially similar to those of the
apparatus of
Figures 1 and 2, but the cross-section of the lower section 26 of the tank 29
is smaller
than that of the upper section 21. In the treatment process, the adsorbent
material on the
plate 6 is fluidized in the same way by delivery of a simple medium through
input 10,
and when delivery of the fluidizing medium is halted, the adsorbent material
is directed
back into the lower section 26 by the converging container walls 33.
Additional mixing
may be required within the expanded upper zone if it is significantly larger
than the
lower section and this can be provided by additional agitators.
Figure 5 illustrates another embodiment of the invention in which a
multiplicity
of electrodes can be closely aligned in a cell in a parallel arrangement.
Application of a
voltage across the outer electrodes 28 and 30 polarises the intermediate
electrodes 32,
so effectively a series of alternate cathodes and anodes are present between
the
outermost cathode 28 and anode 30. The use of bipolar electrodes in this way
facilitates
one current to be generated a number of times with a proportional increase in
voltage.
This has the advantage of increasing the voltage to obtain a larger current in
the
adsorbent material in sections of the bed between the electrodes than would be
achieved
by the simple application of a larger voltage across the bed as a whole. The
distance
between the electrodes can be up to about 25 mm; this is sufficient to allow
cell voltage
to be kept at an acceptable level, without creating blockages of the adsorbent
material,
and to allow the released contaminants to escape in the form of bubbles.
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In the regeneration zone of apparatus of the invention the cathode will
normally
be housed in a separate compartment defined by a porous membrane or filter
cloth to
protect it from direct contact with the adsorbent material. A porous membrane
enables
a catholyte to be pumped through the compartment, serving both to provide a
means for
controlling the pH level and as a coolant for removing heat from the
regeneration zone.
Apparatus of the invention may contain a single cell, or a plurality of cells.
Figure 6
illustrates an arrangement of cells in an adjacent arrangement to one another
with equal
polarity. Figure 7 shows cells arranged in a continuous line, with opposite
polarities in
order to prevent unnecessary consumption of current. In each of the
arrangements
shown in Figures 6 and 7, the respective outermost electrodes must be
connected in
parallel.
In a typical process, using unexpanded intercalated graphite in particulate
form
as the adsorbent, an aqueous liquid with oily contaminants is exposed to the
adsorbent
by agitation in a reservoir with the adsorbent for around 15 minutes. The
amount of
adsorbent can be around 200 grams for each litre of liquid, but the amount can
vary
depending on the concentration of oily contaminant in the liquid, the length
of each
period of exposure, and how many cycles of treatment are to be completed. In
this first
cycle the contaminant attaches to form a layer of oil or oily matter on the
surfaces of the
adsorbent. The adsorbent is then allowed to settle, and a voltage is applied
to partially
regenerate it by passing a charge through the particles. A relatively small
charge, of say
5 to 30 Coulombs/gram is applied for 10 to 30 minutes to achieve partial
regeneration,
with very little oxidation of the oily matter on the particle surfaces, which
remains as a
first layer. The agitation of the liquid and adsorbent and subsequent partial
regeneration
of the adsorbent is then repeated in a second cycle with the consequence that
a second
layer of oily matter forms on the adsorbent surfaces. The process can be
repeated over a
number of cycles with several layers of oily matter forming on the adsorbent
surfaces,
resulting in an absorptive capacity much greater than could be achieved in a
single stage
process.
As noted above, the charge applied to the adsorbent in each adsorption cycle
of
the kind described can be very low. A charge of around 5 c/g can be sufficient
to
regenerate the adsorbent such that an additional layer of oily matter is
adsorbed.
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Normally though, a greater charge; say 20-50 c/g would be applied. In this
way, a
regeneration efficiency of 80% or more can be maintained over several cycles.
This multi-layer adsorption process on the adsorbent particles results in the
particles being held together by the oily layers. This creates voids between
the
agglomerated particles which can receive and retain further oily contaminant.
After completion of sufficient adsorption cycles to create multiple layers of
oily
matter on the adsorbent surfaces, the adsorbent can be fully regenerated by
electrochemical oxidation. In this stage a much higher charge is applied. The
theoretical charge required to achieve full regeneration of unexpanded
intercalated
graphite is 5,400 c/g, but we have achieved substantially complete
regeneration with
applied charge of around 4,700 c/g. By applying slightly greater charge levels
during
each of the earlier adsorption cycles, the charge required to achieve full
regeneration of
the adsorbent (oxidation of all the adsorbed and captured oily matter) at this
stage is
reduced. A typical minimum charge passed to achieve full recovery of the
adsorbent
capacity would be 4,500 c/g.
EXAMPLES
In each of the examples which follow, the adsorbent used is unexpanded
intercalated graphite having the following characteristics:
Appearance: Silvery black flakes with oily texture. Dry and free flowing.
Physical Properties Carbon content Minimum 94.0%
Moisture Maximum 2.0%
Bulk Density 0.4 ¨ 0.5 g/cm3
pH 4 ¨ 7
Particle Size
+ BSS 22 Mesh (710 Microns) Maximum 10%
+ BSS 30 Mesh (500 Microns) Minimum 20%
+ BSS 44 Mesh (355 Microns) Minimum 60%
+ BSS 72 Mesh (212 Microns) Minimum 80%
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+ BSS 100 Mesh (150 Microns) Minimum 90%
- BSS 100 Mesh Maximum 10%
1. Neat Oil treatment waste
A 25% oil water emulsion was created by mixing oil with water in the presence
of an
organic polymer to stabilise the emulsion. This was used to make a 500m1
solution of
5% oil. This was mixed with 100g of unexpanded intercalated graphite particles
as the
adsorbent. After mixing for 30 minutes, 100m1 of sample was removed for
analysis and
100 ml of 25% emulsified oil solution added. Between each adsorption cycle the
adsorbent was partially electrochemically regenerated by passing a charge of
18c/g
through the adsorbent particles. After adsorption cycle 8 a further 100m1
sample was
removed and 100 ml of 25% emulsified oil added. Table 1 below gives the Total
Organic Carbon (TOC) figures before and after adsorption.
TOC Before TOC After
Adsorption adsorption Adsorption
Cycle (mg/1) (ma
1 15669 4536
2 12380 8669
3 8669 5102
4 5102 2601
2601 1301
6 1301 895
7 895 701
8 701 584
9 7333 1680
1107 1107
11 1107 1125
12 1125 615
13 615 446
14 446 314
314 274
16 274 248
17 248 401
18 401 292
19 292 223
223 212
Table 1 ¨ Treatment of neat oils over a number of adsorption cycles
(with partial regeneration between cycles)
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Adsorptive/absorption capacity can be calculated as approximately 60% on a
weight for
weight basis.
2. Synthetic and semi synthetic cutting oils
Two samples of cutting oil solution were made up as 0.1% solutions and then
used in
the adsorption/regeneration system. Table 2 shows the Chemical Oxygen Demand
(COD) data before and after adsorption.
Cutting Oil COD before COD after
(mg/1) (mg/1)
Synthetic 1,524 0
Semi-synthetic 1,650 0
Table 2¨ COD before and after adsorption with electrochemical treatment
3. Adsorption with and without electrochemical treatment
In order to demonstrate the effect of electrochemical treatment, a 1 litre
emulsified
sample of 1% neat oil was mixed with 200g of unexpanded intercalated graphite
particles for 30 minutes. After mixing the mixture was allowed to stand and
the 750m1
of supernatant decanted. 750m1 of fresh emulsified 1% oil was added and the
solution
was mixed for a further 30 mins. This sequence was repeated.
In one series of experiments the adsorbent was electrochemically regenerated
by the
application of a charge of 15 c/g of adsorbent prior to each subsequent
adsorption and in
the other there was no electrochemical regeneration.
Adsorption No Treatment Electrochemical
cycle Regeneration
1 100 100
2 0 86.83
3 0 90.99
4 3.33 91.32
80.82
Table 3 ¨ Regeneration Efficiency compared with fresh adsorbent
with and without partial regeneration
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The table shows that the regeneration efficiency; the ratio of absorptive
capacity of
partially regenerated adsorbent to the absorptive capacity of fresh adsorbent
expressed
as a percentage, remains above 80% after five cycles of exposure to the same
emulsified
oil sample.
4. Oil in water
A 500m1 sample of oily water (5%) was treated mixed with 100g of the
unexpanded intercalated graphite adsorbent. The adsorbent was then treated by
passing
a charge of 1,800 Coulombs through the particles. After partial regeneration
(30 mins)
in this way, the adsorbent was mixed with a fresh oily waste (5%), and then
again
partially regenerated (30 mins). The same oily waste was then used for another
7
adsorption/regeneration cycles with the same adsorbent. This data is shown in
Table 1
and Figure 1 below.
Adsorption/Regeneration Liquid Phase Mass of oil Charge passed
Cycle removed Cumulative (C)
Concentration Cumulative (g)
% oil
1 1.45 17.76 1800
2 2.77 23.68 3600
3 1.63 29.37 5400
4 0.83 33.37 7200
0.42 35.44 9000
6 0.29 36.09 10800
7 0.22 36.40 12600
8 0.19 36.58 14400
TOTAL 36.58 14400
Table 4 - Summary Oil removal v charge passed
