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Wayang DANG, et al.

Oil-Water Separation Membrane









http://cen.acs.org/articles/93/web/2015/08/New-EasyClean-Membrane-Separates-Oil.html

New Easy-To-Clean Membrane Separates Oil From Water

by

Prachi Patel



TAKING A DIP --A plastic tube covered on the bottom with a new self-cleaning, oil-separating membrane is immersed (left) into a mixture of water with a 4-cm layer of red-dyed petroleum on top. When the membrane reaches the water (center), water soaks the membrane and rinses off any petroleum that might have stuck to it. When the tube is lifted (right), it pulls out a 4-cm-layer of petroleum.

A steel mesh with a novel self-cleaning coating can separate oil and water, easily lifting oil from an oil-water mixture and leaving the water behind (ACS Nano 2015, DOI: 10.1021/acsnano.5b03791). If the coated mesh gets contaminated with oil, it can be simply rinsed off with water and reused. The new membrane promises to be a practical technology to clean up oil spills, its developers say.

Emergency responders typically fight oil spills by burning, using booms and skimmers, or releasing chemical dispersants. Oil-water separation membranes would be faster and more effective. Although various types of membranes have been studied, they aren’t practical yet, mainly because they are easily contaminated with oil, which renders them useless, says Xiaokong Liu, a polymer chemistry and surface science researcher at the University of South Australia.

Oil-water separation membranes fall into two categories. One is a water-repelling membrane that selectively lets oil seep through. Over time, this type gets clogged with oil and loses its effectiveness. The other, more common type of membrane loves water and repels oil when it is already wet, preventing oil from crossing. This type has to be completely wetted before it can be used. If oil touches it when it’s dry or partially dry—which happens easily in an oil-spill environmen t— it loses its oil-water separation ability and must be cleaned using detergents.

Liu and his colleagues made a membrane of the second hydrophilic type, but with a key improvement that makes it more practical: Theirs can be quickly cleaned of oil contamination simply by water rinsing, which also means it doesn’t need to be wetted carefully before use.





http://cgi.cen.acs.org/cgi-bin/cen/trustedproxy.cgi?redirect=http://pubs.acs.org/doi/abs/10.1021/acsnano.5b03791?source=cen
http://pubs.acs.org/doi/abs/10.1021/acsnano.5b03791?source=cen

Cleaning of Oil Fouling with Water Enabled by Zwitterionic Polyelectrolyte Coatings:
Overcoming the Imperative Challenge of Oil–Water Separation Membranes


Ke He, Haoran Duan, George Y. Chen, Xiaokong Liu, Wensheng Yang, Dayang Wang

Herein we report a self-cleaning coating derived from zwitterionic poly(2-methacryloyloxylethyl phosphorylcholine) (PMPC) brushes grafted on a solid substrate. The PMPC surface not only exhibits complete oil repellency in a water-wetted state (i.e., underwater superoleophobicity), but also allows effective cleaning of oil fouled on dry surfaces by water alone. The PMPC surface was compared with typical underwater superoleophobic surfaces realized with the aid of surface roughening by applying hydrophilic nanostructures and those realized by applying smooth hydrophilic polyelectrolyte multilayers. We show that underwater superoleophobicity of a surface is not sufficient to enable water to clean up oil fouling on a dry surface, because the latter circumstance demands the surface to be able to strongly bond water not only in its pristine state but also in an oil-wetted state. The PMPC surface is unique with its described self-cleaning performance because the zwitterionic phosphorylcholine groups exhibit exceptional binding affinity to water even when they are already wetted by oil. Further, we show that applying this PMPC coating onto steel meshes produces oil–water separation membranes that are resilient to oil contamination with simply water rinsing. Consequently, we provide an effective solution to the oil contamination issue on the oil–water separation membranes, which is an imperative challenge in this field. Thanks to the self-cleaning effect of the PMPC surface, PMPC-coated steel meshes can not only separate oil from oil–water mixtures in a water-wetted state, but also can lift oil out from oil–water mixtures even in a dry state, which is a very promising technology for practical oil-spill remediation. In contrast, we show that oil contamination on conventional hydrophilic oil–water separation membranes would permanently induce the loss of oil–water separation function, and thus they have to be always used in a completely water-wetted state, which significantly restricts their application in practice.



SUBSTRATES FOR OIL AND WATER SEPARATION
WO2015113106

Disclosed herein is an oil-water separation substrate comprising a porous substrate and a coating formed from an epoxy functionalised polyelectrolyte on said substrate.

TECHNICAL FIELD

[0002 ] The present invention relates to substrates, such as membranes, that can be used to separate mixtures of oil and water, to methods for preparing these substrates, and to methods for separating oil and water mixtures using these substrates.

BACKGROUND

[0003 ] Contamination of water with oil is a constant problem in natural environments as well as in industrial settings. As a result, there is a need for effective methods for separating oil from oil-water mixtures.

[0004 ] Oil and water mixtures can be separated using separation tanks in which the oil is allowed to separate from the water naturally and the oil is then removed from the water. However, this method is time consuming, inefficient and not particularly suitable for separations using large volumes. More commonly nowadays efficient oil-water separation relies on cross-flow filtration through hydrophobic (superhydrophobic) membranes which allow oil to pass through the membrane whilst retaining water above. However, as the density of oil is lower than that of water, water naturally settles below the oil. Therefore, oil-water separation through hydrophobic membranes of this type requires high energy input. Recently, hydrophilic membranes which can completely repel oil underwater have been used for oil water separation driven only by gravity. However, these hydrophilic membranes can only be used in a water- wetted state because the hydrophilic membranes are easily contaminated by oil in when they are in a dry state. Once a membrane has been contaminated with oil in this way it cannot be used for oil water separation any more.

[00051 There is a need for oil-water separation substrates that overcome one or more of the problems with known substrates and/or provide an alternative to known substrates. SUMMARY

[0006] In a first aspect, provided herein is an oil-water separation substrate, said substrate comprising a porous substrate and a coating formed from an epoxy functionalised polyelectrolyte on said substrate.

[0007] In certain embodiments, the oil-water separation substrate is a mesh, fabric, sponge, foam or other nanoporous material. In certain specific embodiments, the substrate is a water purification membrane or filter.

10008] In certain embodiments, the epoxy functionalised polyelectrolyte is a poly(ammonium phosphate). In certain specific embodiments, the epoxy functionalised polyelectrolyte has structural formula (I):

<img class="EMIRef" id="289894517-imgf000003_0001" />

(I) wherein Rj , R4, and R5are each independently (<">-(% alkyl;

R2and R3are each independently selected from the group consisting of H and C i-C2alkyl; Re, R?, Rx are each independently Cj -C2alkyl; and R9is selected from the group consisting of CI and Br.

[0009] In certain embodiments, the coating formed from the epoxy functionalised polyelectrolyte is cross linked. The coating formed from the epoxy functionalised may be cross linked using a cross linking agent. The cross linking agent may be a polyamine. The polyamine may be a polyamine comprising more than three primary amino groups. In certain embodiments, the polyamine is selected from the group consisting of poly(allylamine), polyethylenimine (branched), and polyv inyl amine). In certain specific embodiments, the polyamine is poly(allylamine). The polyamine may be coated onto the porous substrate w<r>ith the epoxy functionalised polyelectrolyte or the epoxy functionalised polyelectrolyte may be treated with the polyamine after the former has been coated onto the porous substrate. The primary amine groups of the polyamine react with the epoxy groups of the epoxy functionalised polyelectrolyte to form a cross- linked composite. [0010] In a second aspect, provided herein is an epoxy functionalised polyelectrolyte having structural formula (I):



(I) wherein Rj , R4, and R5are each independently ( -( \ alkyl;

R2and R3are each independently selected from the group consisting of H and Ci-C2alkyl; R6, R7, R are each independently Cj -C2alkyl; and R9is selected from the group consisting of CI and Br.

[001 1 1 In a third aspect, provided herein is a coating composition for coating a porous substrate to form an oil-water separation substrate, the coating composition comprising an aqueous mixture of an epoxy functionalised polyelectrolyte.

[0012] In certain embodiments of the third aspect, the coating composition further comprises a cross linking agent. The cross linking agent may be a polyamine. The polyamine may be a polyamine comprising more than three primary amino groups. In specific embodiments, the polyamine is selected from the group consisting of poly(allylamine), polyethylenimine (branched), and poly(vinyl amine).

[0013] In certain other embodiments of the third aspect, the epoxy functionalised polyelectrolyte may be treated with the polyamine after the former has been coated onto the porous substrate.

[0014] In a fourth aspect, provided herein is a method for forming an oil-water separation substrate, the method comprising providing a porous substrate and contacting the porous substrate with the coating composition according to the third aspect under conditions to form a coating formed from the epoxy functionalised polyelectrolyte on said substrate.

[0015 ] In a fifth aspect, the present invention provides a method for separating oil and water from an oil- water mixture, the method comprising contacting the oil-water mixture with the substrate of the first aspect of the invention under conditions to separate at least some of the oil from the oil-water mixture.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[0016] Figure 1 shows X-ray photoelectron spectroscopy (XPS) wide scans for a stainless steel mesh without (a) and with (b) an epoxy functionalised PMPC coating. Inset of b: High-resolution spectra for P 2p from the PMPC coated stainless steel mesh.

[0017] Figure 2 shows a time series of optical photos recorded during the stainless steel meshes (aperture of 100 µ??) were contaminated by Nile red labelled canola oil in air, and then were immersed into water. The left sample is a piece of raw stainless steel mesh and the right one is a piece of stainless steel mesh coated with epoxy functionalised PMPC.

[0018] Figure 3 shows photographs showing: a. the epoxy functionalised PMPC coated stainless steel mesh is wetted by water; b. oil-water mixture was poured above the epoxy functionalised PMPC coated mesh; c. the oil-water mixture is separated.

[0019] Figure 4 shows a time series of optical photos recorded during which stainless steel mesh covered plastic tubes were immersed in an oil-water mixture to skim the oil out. It can be observed that the epoxy functionalised PMPC coated mesh can successfully skim the oil out from the oil-water mixture, but the same result cannot be achieved with the raw mesh.

DESCRIPTION OF EMBODIMENTS

10020] The present invention, and embodiments thereof, will now be described in more detail. However, before proceeding it is important to note that various terms that will be used throughout the specification have meanings that will be well understood by a skilled addressee. However, for ease of reference, some of these terms will now be defined.

[0024] As discussed, the present invention provides an oil-water separation substrate, said substrate comprising a porous substrate and a coating fonned from an epoxy functionalised polyelectrolyte on said substrate.

[0025] As discussed previously, hydrophilic membranes are known for use in separating oil from oil- water mixtures. However, these membranes tend to be contaminated with oil in a dry state which then renders them not fit for purpose. Advantageously, we have found that the substrates of the present invention are hydrophilic, oil-repellent underwater and self-cleaning which means that oil contaminations on the substrate can simply be washed away with water.

[0026] The substrates of the present invention are particularly suitable for use in oil-water separations and for oil skimming from oil-water mixtures. The fonner property is highly desirable for remediating oil contaminated waters whilst the latter property is highly desired for oil spill remediation.

[0027] Without intending to be bound by any specific theory, we suggest that the functional groups of the polyelectrolyte, such as the phosphate and ammonium groups of the epoxy functionalised polyelectrolyte of formula (1), have a strong hydration ability and this enables the surface of the substrate to strongly trap water molecules. Even if the surface is contaminated by oil the oil can be replaced by water. The coating can be used for oil-water separation because it can be highly hydrated in water, thus forming a dense water layer which can retain oil above the water layer.

[0028] The porous substrate may be any flexible, rigid or semi-rigid metal, plastic or ceramic material having pores of a size sufficient to allow water to pass through. Advantageously, we have found that the coating comprising the epoxy functionalised polyelectrolyte can be formed on a range of substrate materials and, indeed, its effectiveness as a coating is largely independent of the material used in the substrate. By way of example only, suitable metal substrates that can be used include iron, titanium, aluminium, nickel, copper, and alloys of any of these metals such as steel. The metal substrate may be in the form of a mesh, fabric, sponge, foam or other porous material. Suitable plastic substrates that can be used include polytetrafluoroethylenene (Teflon), polyethylene, polypropylene (PP), polydimethylsiloxane (PDMS), polystyrene (PS), poly(ether sulfone), polyacrylonitrile, cellulose acetate, polyvinylidene fluoride, polysulfone, polyamide, polyurethane, poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), poly(ethylene terephthalate) (PET), and poly(4-methyl- l -pentene) (PMP). The plastic substrate may be in the form of a mesh, fabric, sponge or foam.

10029] The substrate may be any suitable form, such as a membrane, filter, film, boom, and the like. It can be any shape. In specific embodiments, the porous substrate is in the form of a water purification membrane or filter. In other embodiments, the porous substrate is in the form of an elongate, flexible boom that can be used to contain oil spills and/or skim oil from the surface of a body of water. [0030] The average pore diameter of the substrate may be in the range of about 50 nm to about 5 mm. For example, the substrate may be a stainless steel mesh with apertures of about 25 µ??, about 50 µ?? or about 100 µ??.

[0031 ] The epoxy functionalised polyelectrolyte may be any polyelectrolyte having one or more epoxy groups covalently bonded thereto. In embodiments, the polyelectrolyte is a poly(ammonium phosphate). In embodiments, the polyelectrolyte is a poly(tetraalkyl ammonium phosphate).

[0032] In specific embodiments, the epoxy functionalised polyelectrolyte has structural formula (I):



(I)

[0033] wherein R R4, and R5are each independently C1-C3 alkyl;

[0034] R2and R3are each independently selected from the group consisting of H and C i-C2alkyl; [0035] R6, R7, R8are each independently Cj-C2alkyl; and [0036] R9is selected from the group consisting of CI and Br.

[0037] The C 1 -C3 alkyl group may be selected from the group consisting of: -CH2-, -CH2CH2-, - CH2CH2CH2-, and -CH2(CH3)CH2-. The Cj-C? alkyl group may be selected from the group consisting of: -CH2-, and -CH2CH2-.

[0038] The term "a coating formed from an epoxy functionalised polyelectrolyte" is used herein because the porous substrate is coated with a coating composition comprising the epoxy functionalised polyelectrolyte which may, in turn, react with functional groups on the substrate. For example, the epoxy group of the epoxy functionalised polyelectrolyte may react with hydroxy or amino groups on the substrate and, therefore, after coating not all of the molecules in the coating may be in the form of the epoxy functionalised polyelectrolyte.

[0039] Optionally, the epoxy functionalised polyelectrolyte in the coating may be cross linked using a cross linking agent. The cross linking agent may be a multifunctional molecule having two or more functional groups that are capable of reacting with functional groups of the epoxy functionalised polyelectrolyte. In certain embodiments, the cross linking agent is a polyamine and the coating is formed from the epoxy fiinctionalised polyelectrolyte and the polyamine. The polyamine may be a polyamine comprising more than three primary amino groups. In embodiments, the polyamine is selected from the group consisting of poly(allylamine), polyethylenimine (branched), and poly(vinyl amine). In specific embodiments, the polyamine is poly(allylamine).

[0040] The epoxy functionalised polyelectrolyte may be cross linked during coating of the porous substrate with the epoxy functionalised polyelectrolyte or the epoxy functionalised polyelectrolyte may be treated with the cross linking agent after the former has been coated onto the porous substrate. For example, the polyamine may be coated onto the porous substrate with the epoxy functionalised polyelectrolyte or the epoxy functionalised polyelectrolyte may be treated with the polyamine after the former has been coated onto the porous substrate. The primary amine groups of the polyamine react with the epoxy groups of the epoxy functionalised polyelectrolyte to form a cross-linked composite.

Polyamines comprising more than three primary amino groups are particularly suitable for this purpose. Polyamines that can be used include poly(allylamine), polyethylenimine (branched), and polyvinyl amine). Without intending to be bound by any specific theory, we suggest that the polyamine facilitates the adhesion of the epoxy functionalised polyelectrolyte onto the substrate and improve the coating stability because the primary amine groups react with the epoxy groups to cross link the epoxy functionalised polyelectrolyte.

[0041 ] To coat the substrate, an aqueous coating composition comprising the epoxy functionalised polyelectrolyte and polyamine (if present) is formed. The concentration of the epoxy functionalised polyelectrolyte in the aqueous coating composition may be from about 0.05 mg/mL to about 500 mg/mL. The concentration of the polyamine in the coating composition may be from about 0.01 mg/mL to about 100 mg/mL. In embodiments, the concentration of the epoxy functionalised polyelectrolyte in the aqueous coating composition is about 5 mg/mL and the concentration of the polyamine in the coating composition (if present) is about 1 mg/mL. The mass ratio of epoxy functionalised polyelectrolyte to polyamine in the coating composition may be in the range of 5000: 1 to 5: 1.

[0042] Optionally, the coating composition can contain solvents, excipients and/or additives as required. Specifically, the coating composition may contain conventional coating adjuvants, such as, for example, tackifiers, pigments, extenders, emulsifiers, crosslinkers, coalescing agents, buffers, neutralisers, thickeners or rheology modifiers, humectants, wetting agents, biocides, plasticisers, antifoaming agents, colorants, waxes, anti-oxidants, and the like.

[0043 ] The present invention provides an epoxy functionalised polyelectrolyte having structural formula (I):



(I) wherein R1 ;R4, and R5are each independently C 1-C3 alkyl;

R2and R3are each independently selected from the group consisting of H and C i-C2alkyl;

R6, R7, R8are each independently C|-C2alkyl; and R9is selected from the group consisting of CI and Br.

[0044] The present invention also provides a method for forming an oil-water separation substrate, the method comprising providing a porous substrate and contacting the porous substrate with a coating composition comprising an epoxy functionalised polyelectrolyte to form a coating formed from the epoxy functionalised polyelectrolyte on said substrate.

[0045] The surface of the substrate may be contacted with the coating composition by conventional application methods such as dip coating, spin coating, spray coating, curtain coating, roller coating, and the like. In embodiments, the surface of the substrate is contacted with the aqueous coating composition by dipping the substrate into the coating composition for a time and at a temperature that results in adsorption of at least some of the coating materials to the surface of the substrate.

[0046] In embodiments, the substrate is immersed in the coating composition for a period of from about 1 hour to about 36 hours. In specific embodiments, the immersion time is 24 hours. The thickness of the coating that is deposited on the surface of the substrate will depend, at least in part, on the l ength of time the substrate is immersed in the coating composition. The thickness may be between about 2 nm and about 1000 nm.

[0047] After removal from the coating composition the substrate is typically dried, or allowed to dry, to form a film on the surface. Typically, the solvent can be removed by dying the coating composition at room temperature or at elevated temperature (e.g. from about 5°C to about 95°C). The substrate can also be dried using a stream of air or nitrogen or at reduced pressure, if necessary.

[0048] The coating composition will normally be applied so as to provide a substantially uniform application of the coating composition onto the surface of the substrate and the formation of a continuous layer on the substrate. However, it is also contemplated that the coating composition can be applied so as to form a discontinuous layer on the substrate. In other words, the coating may cover the whole of the surface to which it is applied or it may cover only part of the surface to which it is applied.

[0049] In embodiments, the substrate is a water purification membrane or filter. Membranes of this type are typically made from poly(ether sulfone), polyacrylonitrile or polyvinylidene fluoride and are commonly used in water or wastewater filtration. We have found that the coating described herein separates oil from oil contaminated water that is passed through the membrane or filter. Advantageously, the methods of the present invention provide a relatively simple, and therefore inexpensive, way to separate oil from water and can be used for a range of applications such as remediation of oil contaminated industrial, domestic, municipal water.

[0050] The substrates of the present invention could also be used to separate two immiscible oils.

[0051 ] The present invention also provides a method for separating oil and water from an oil-water mixture, the method comprising contacting the oil-water mixture with the substrate of the first aspect of the invention under conditions to separate at least some of the oil from the oil-water mixture.

EXAMPLES

[0052] Example 1 - Synthesis of epoxy functionalised poly[2-(methyloyloxy)ethylphosphorylcholine] (PMPC).



[0053] A 100 mL flask was charged with 2-methacryloyloxyethyl phosphorylcholine (5 g, 16.96 mmol), 2,2'-bipyridine (61.7 mg, 0.4 mmol), glycidol 2-bromopropionate ( 104.5 mg, 0.5 mmol) and 10 mL of methanol. The flask was then sealed and degassed using a freeze-thaw method for 3 cycles. Subsequently, a catalyst containing CuBr ( 10.1 mg, 0.070 mmol) and CuBr2(5.0 mg, 0.022 mmol) was added rapidly. After 3 cycles of degassing again, the flask was charged with argon and incubated in a water bath at 30 °C for 12h. After reaction, the reaction mixture was diluted with ethanol and then filtered with silica column using ethanol as eluent to remove the residual CuBr2. The obtained ethanol solution was then concentrated by rotary evaporation. The concentrated ethanol solution was then precipitated by dropping it into a tenfold excess of non-solvent tetrahydrofuran (TH F). The precipitate was collected by centrifuge and dried in oven. [0054] Example 2 - Preparation of a coating composition

[0055] A coating composition comprising an aqueous solution of the epoxy functionalised PMCP was prepared by dissolving the epoxy functionalised PMCP from Example 1 in water at a concentration of 5mg/mL.

100561 Example 3 - Preparation of an alternative coating composition

[0057] A coating composition comprising an aqueous solution of the epoxy functionalised PMCP and poly(allylamine) was prepared by dissolving the epoxy functionalised PMCP from Example 1 in water at a concentration of 5mg/mL and poly(allylkamine) (A/w~58000) at a concentration of 1 mg/mL.

[0058] Example 4 - Preparation of coated stainless steel meshes for oil-water separation

[0059] Stainless steel mesh with aperture of 100 µ?? was successively cleaned by sonication in acetone, iso-propanol and ethanol for 10 min for each step. The cleaned stainless steel mesh was dried using N2and then immersed in the coating composition of Example 2 for 24 h. The stainless steel mesh was then rinsed by water and dried by N2.

[0060] Results - Surface composition of the PMPC coated stainless steel mesh

[00611 In order to confirm the stainless steel mesh was successfully coated with the PMPC

polyelectrolyte, X-ray photoelectron spectroscopy measurements were employed to analyse the surface composition of the stainless steel mesh before and after being coated with PMPC.

[0062] As shown in Figure 1 , after being coated with the epoxy functionalised PMPC, the signal of Fe and Cr which are the typical elements from stainless steel mesh cannot be detected, but significant N and P which are from PMPC are detected, revealing the stainless steel mesh is successfully coated with the PMPC polyelectrolytes.

[0063] Results - Self-cleaning property of the epoxy functionalised PMPC coated stainless steel mesh

[0064] The epoxy functionalised PMPC coated stainless steel meshes exhibit excellent self-cleaning properties. Specifically, the oil contamination on the meshes can be easily and completely washed away by water without aid of any surfactant.

[0065] As shown in Figure 2, it can be observed that the two samples can be contaminated by canola oil in air, but when they were immersed into water, the oil would spread on the raw mesh more aggressively, but in contrast, the oil on the epoxy functionalised PMPC coated mesh completely detached from the mesh. Therefore, the epoxy functionaliscd PMPC coated mesh exhibits excellent self-cleaning properties which enables oil contamination on the mesh to be washed away with water without the need for detergents or other cleaning materials.

[0066] Results - Epoxy functionalised PMPC coated stainless steel mesh used for oil-water separation

10067] As shown in Figure 2, the epoxy functionalised PMPC coated stainless steel meshes exhibit perfect oil repellence in water. Therefore, the epoxy functionalised PMPC coated stainless steel meshes can be used for oil-water separation.

10068] As shown in Figure 3, it was observed that for the water wetted epoxy functionalised PMPC coated stainless steel mesh only permitted water to pass through and it retained the oil above. This demonstrates that the epoxy functionalised PMPC coated stainless steel mesh can be used for high efficient oil-water separation.

[0069] Results - PMPC coated stainless steel mesh used for skimming

[0070] By combining the self-cleaning property and the oil-water separation ability of the epoxy functionalised PMPC coated stainless steel mesh, the epoxy functionalised PMPC coated stainless steel mesh can be used for oil skimming.

10071] As seen in Figure 4a, one end of a plastic tube was covered by a piece of stainless steel mesh and fixed by a hollowed screw cap, this setup is further used for oil skimming. In figures a, b and c, there are two plastic tubes with one end covered by stainless steel meshes. The left tube is covered by a piece of raw stainless steel mesh, the right one is covered by a piece of epoxy functionalised PMPC coated stainless steel mesh. The beaker contains water-hexadecane mixtures, the hexadecane was stained by oil red O. Figure a, b, c is a time series of optical photos recorded during the stainless steel meshes coved plastic tubes were immersed into the oil-water mixture to skim the oil out. It can be observed that the epoxy functionalised PMPC coated mesh can successfully skim the oil out from the oil-water mixture, but the raw mesh can not.

[0072] Example 5 - Preparation of coated stainless steel meshes for oil-water separation

10073 ] A coated stainless steel mesh with aperture of 100 µ?? can be prepared using the coating composition of Example 3 and the coating method described in Example 4.

[0074] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

[0075] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

[0076] All publications mentioned in this specification are herein incorporated by reference. Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia or elsewhere before the priority date of each claim of this application.





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