DESC:FIELD
The present disclosure relates to a process for the preparation of a superhydrophobic membrane.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Superhydrophobic membrane – refers to a membrane with water contact angle greater than 150° and made out of low surface energy coating.
Pristine membrane – refers to a commercially available polyurethane (PU) membrane, which is inherently hydrophilic i.e., soaks water. The terms ‘pristine membrane’, ‘polyurethane membrane’, and ‘uncoated polyurethane membrane’ are used interchangeably across the specification.
Biomimetic materials – refers to synthetic (man-made) materials that mimic natural materials or that follow a design motif derived from nature.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
The aquatic ecosystem is affected due to oil contamination by regular industrial discharges or accidental oil spillages during production and transportation. Conventionally, the oil can be separated from water by using biomimetic materials based systems such as superhydrophobic membrane. Conventionally, the superhydrophobic membrane is prepared by multistep chemical and physical processes. The superhydrophobic membrane prepared by using the conventional multistep processes has low durability and fails to perform under severe conditions. Further, the multistep processes are difficult to scale up and require post chemical modifications that lead to an increased cost for the preparation of superhydrophobic membranes.
There is, therefore, a need for a process for the preparation of the superhydrophobic membrane which mitigates the above mentioned drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for preparing a superhydrophobic membrane for oil and water separation.
Another object of the present disclosure is to provide a mechanically tough superhydrophobic membrane prepared from small molecules.
Still another object of the present disclosure is to provide a process for preparing a superhydrophobic membrane that involves a single step, easy to scale up, requires no post chemical modification, and no use of polymer and nanoparticles.
Yet another object of the present disclosure is to provide a process for preparing a superhydrophobic membrane that is durable, non-toxic, and energy-efficient.
Yet another object of the present disclosure is to provide a superhydrophobic membrane for oil and water separation at practically relevant severe conditions.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY
The present disclosure relates to a process for the preparation of a superhydrophobic membrane. The process comprises mixing predetermined amounts of at least two acrylates and at least one aminosilane in a fluid medium under stirring for a time period in the range of 2 hours to 5 hours to obtain a solution. The solution is coated on a membrane to obtain a coated membrane. The coated membrane is dried at a temperature in the range of 50 oC to 80 oC for a first predetermined time period to obtain a dried membrane. The dried membrane is subjected to electromagnetic radiation for a second predetermined time period to obtain the superhydrophobic membrane.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figures 1A to C illustrate chemical structures of A) Dipentaerythritol pentaacrylate (5Acl); B) 3-(Aminopropyl) triethoxysilane (AS) and C) Octadecyl acrylate (ODA);
Figures 1D to K illustrate digital images (D, F, H, J) and contact angle images (E, I, G, K) of a beaded water droplet (E, I) and oil droplet (G, K) on the pristine membrane (D-G) and superhydrophobic membrane (H-K);
Figures 1L to O illustrate digital images of pristine membrane dipped in water (L) and superhydrophobic membrane dipped in water (M), water stream over the pristine membrane (N), and water stream over the superhydrophobic membrane (O);
Figures 2A to B illustrate FTIR Spectra of chemicals used for the preparation of the superhydrophobic surface: Figure 2A illustrates FTIR spectra of 3-aminopropyl triethoxysilane before polymerization (blue) and after polymerization (red), Figure 2B represents FTIR spectra of octadecyl acrylate (violet), dipentaerythritol pentaacrylate (yellow), and superhydrophobic coating (red);
Figures 2C to D illustrate FESEM images of pristine fibers (C) and superhydrophobic membrane (D);
Figures 2E to F illustrate EDX maps of Si on pristine fibers (E) and superhydrophobic membrane (F);
Figure 3A illustrates stress-strain curves of superhydrophobic membrane (black) and pristine membrane (red);
Figure 3B illustrates a stretched pristine membrane with a load applied of 500gm (stretched and damaged);
Figure 3C illustrates a superhydrophobic membrane with a load applied of 500gm (non-stretchable);
Figures 4A to C illustrate sandpaper abrasion test: Figure 4A illustrates sandpaper abrasion test, Figure 4B illustrates beaded water droplet on the abraded superhydrophobic membrane surface and Figure 4C illustrates water contact angle (WCA) of the superhydrophobic membrane after abrasion test;
Figures 4D to F illustrates adhesive tape test: Figure 4D illustrates adhesive tape test, Figure 4E illustrates beaded water droplet on the abraded superhydrophobic membrane surface and Figure 4F illustrates the water contact angle (WCA) of the superhydrophobic membrane after abrasion test;
Figures 4G to I illustrates knife scratch test: Figure 4G illustrates knife scratch test, Figure 4H illustrates beaded water droplet on the abraded superhydrophobic membrane surface and Figure 4I illustrates water contact angle (WCA) of the superhydrophobic membrane after abrasion test;
Figures 4J to M illustrates sand drop test: Figures 4J to K illustrate sand drop test, Figure 4L illustrates beaded water droplet on the abraded superhydrophobic membrane surface and Figure 4M illustrates water contact angle (WCA) of the superhydrophobic membrane after abrasion test;
Figures 4N to P illustrate digital images of various physical manipulations winding (N), creasing (O), twisting (P) on the superhydrophobic membrane, Figure 4Q illustrates beaded water droplet on the abraded superhydrophobic membrane surface and Figure 4R illustrates water contact angle (WCA) of the superhydrophobic membrane after abrasion test;
Figure 5 illustrates the embedded water wettability of superhydrophobic membrane after exposing to harsh aqueous chemical conditions;
Figures 6 A to D illustrate digital images of gravity-driven filtration of oil-dichloromethane mixture;
Figures 6 E to H illustrate digital images of gravity-driven filtration of oil-kerosene mixture;
Figures 7 A to D illustrate digital images of gravity-driven filtration of oil-diesel mixture;
Figures 7 E to H illustrate digital images of gravity-driven filtration of oil-petrol mixture;
Figures 8 A to D illustrate digital images of gravity-driven filtration of water-silicone oil mixture;
Figure 9 illustrates the oil separation efficiency of various oil/water mixtures, oils with varying densities;
Figure 10 illustrates the oil separation efficiency of the superhydrophobic membrane with petrol and diesel/water mixtures with water of various harsh chemical conditions;
Figure 11 illustrates repetitive oil separation of the superhydrophobic membrane for 100 cycles using petrol and diesel; and
Figure 12 illustrates advancing contact angle and contact angle hysteresis of the superhydrophobic membrane after repetitive use for 100 cycles for remediation of petrol and diesel/water mixture.
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawings.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The term “superhydrophobic” as used herein refers to a property of a material that is extremely hydrophobic and difficult to wet. The degree of hydrophobicity or wettability of the material is determined by the contact angle of water with the material. When the water contact angle (WCA) is greater than 90o, the surface is hydrophobic and when the water contact angle is greater than 150o, it is considered to be superhydrophobic. It is also long known in the art that when the contact angle is 0o, the material is considered wet with respect to that material. A given substrate may give a continuous range of contact angle values. The maximum contact angle is referred to as the advancing contact angle, a measure of liquid-solid cohesion, and the minimum contact angle is referred to as receding contact angle, a measure of liquid-solid adhesion, and is measured from dynamic experiments. The difference between the two is contact angle hysteresis.
Conventionally prepared superhydrophobic membranes used for the separation of oil and water have low durability and fail to perform under severe conditions. The conventional processes are multistep, tedious, are difficult to scale up, requires post chemical modifications, and therefore not economic.
The process of the present disclosure provides a simple, easy to scale up, environment friendly, and economic process for the preparation of superhydrophobic membrane.
In an aspect of the present disclosure, there is provided a process for the preparation of superhydrophobic membrane.
The process is described in detail.
In a first step, predetermined amounts of at least two acrylates and at least one aminosilane are mixed in a fluid medium under stirring for a time period in the range of 2 hours to 5 hours to obtain a solution.
In an embodiment, the acrylate is selected from dipentaerythritol pentaacrylate, and octadecyl acrylate. In an exemplary embodiment, the acrylate is a combination of dipentaerythritol pentaacrylate, and octadecyl acrylate.
In an embodiment, the aminosilane is selected from 3-aminopropyltriethoxysilane, [3-(2-Aminoethylamino)propyl]trimethoxysilane, and (3-Aminopropyl) trimethoxy silane. In an exemplary embodiment of the present disclosure, the aminosilane is 3-aminopropyltriethoxysilane.
The chemical structures of the compounds are illustrated in Figures 1A to C.
In an embodiment, the molar ratio of the acrylate to the aminosilane is in the range of 1:2 to 1:4. In an exemplary embodiment of the present disclosure, the molar ratio of the acrylate to the aminosilane is 1: 3.5.
In an embodiment, the molar ratio of dipentaerythritol pentaacrylate to 3-aminopropyltriethoxysilane to octadecyl acrylate is in the range of 1:15:3.
In an embodiment, the fluid medium is at least one selected from toluene, ethanol, acetone, and pentanol. In an exemplary embodiment of the present disclosure, the fluid medium is toluene.
In an embodiment, the dipentaerythritol pentaacrylate, 3-aminopropyltriethoxysilane, and octadecyl acrylate are mixed in a fluid medium for a time period in the range of 2 hours to 5 hours to obtain a solution. In an exemplary embodiment of the present disclosure, the time period is 3 hours.
In a second step, the solution is coated on a membrane to obtain a coated membrane.
In an embodiment, the coating is carried out by a method selected from spray deposition, and dip coating. In an exemplary embodiment of the present disclosure, the coating is carried out by spray deposition.
In an embodiment, the membrane is selected from polyurethane, cotton fabric, jute, and silk.
In an exemplary embodiment of the present disclosure, the membrane is a polyurethane membrane. The uncoated polyurethane membrane is both hydrophilic and oleophilic to water and oil with a contact angle of 0°.
In accordance with the present disclosure, the thickness of the coating on the membrane is in the range of 0.5 micrometers to 2 micrometers.
In a third step, the coated membrane is dried at a predetermined temperature for a first predetermined time period to obtain a dried membrane.
In an embodiment, the predetermined temperature is in the range of 50 oC to 80 oC. In an exemplary embodiment of the present disclosure, the predetermined temperature is 60 oC.
In an embodiment, the first predetermined time period is in the range of 2 hours to 4 hours. In an exemplary embodiment of the present disclosure, the first predetermined time period is 3 hours.
In the final step, the dried membrane is subjected to electromagnetic radiation for a second predetermined time period to obtain the superhydrophobic membrane.
In an embodiment, the electromagnetic radiation is selected from UV radiation, sunlight.
In an embodiment, the second predetermined time period is in the range of 1 hour to 3 hours. In an exemplary embodiment of the present disclosure, the second predetermined time period is 1 hour.
In an embodiment, the contact angle of the superhydrophobic membrane of the present disclosure is in the range of ~154° to ~157°. In an exemplary embodiment, the contact angle of the superhydrophobic membrane of the present disclosure 155.6°.
The superhydrophobic membrane with contrasting wettability’s soaks the oil phase while extremely repelling the water is used for filtration based separation of various kinds of the oil-water mixtures. The oils can include petrol, diesel, kerosene, silicone oil, and dichloromethane.
In accordance with the present disclosure, 3-aminopropyltriethoxysilane (AS) undergoes polymerization during the evaporation of the fluid medium through the formation of Si-O-Si bond. The polymerization of 3-aminopropyltriethoxysilane forms covalent cross-linking with dipentaerythritol pentaacrylate (5Acl) and octadecyl acrylate (ODA). The Fourier-transform infrared spectroscopy (FTIR) characterization analysis identified the peak at 1076 cm-1 for Si-O-C bond of AS significantly reduced during heating and a new peak at 1028 cm-1 is observed due to the formation of Si-O-Si bond which confirms the polymerization of the AS. The peaks at 1617 cm-1 corresponding to the amine groups of the AS, which remains unaffected during the polymerization process. These primary amines were reacted with the acrylate groups of 5Acl and ODA through the 1,4-conjugate addition reaction.
Further, 5Acl covalently cross-links with AS polymeric network which imparts superior mechanical durability to the superhydrophobic membrane. The surfactant like ODA molecule with acrylate moiety at one end and a hydrophobic chain on the other end imparts the water repellent property to the membrane. The successful reaction of AS with 5Acl and ODA is evident from the FTIR study where 1409 cm-1 peak corresponding to the C-H bond for ß carbon of the vinyl group of both 5Acl and ODA, that significantly reduced with respect to the carbonyl stretching (1735 cm-1) after reacting with the AS polymer. The unreacted acrylates of 5Acl and ODA are likely to react with each other through a 2p+2p cycloaddition reaction after UV treatment.
The small molecules (acrylates and aminosilanes) are polymerized in situ which offer enhanced mechanical strength to the highly deformable membrane. The coated membrane is non-stretchable, resists deformation thus improving the mechanical durability of the superhydrophobic membrane.
In an embodiment, the superhydrophobic membrane obtained by the process of the present disclosure is characterized by having
• a water contact angle in the range of 154° to 157°;
• enables to resist the deformation of a highly deformable membrane due to coating; and
• has a filtration efficiency of 99% even after 100 consecutive cycles of separation.
The superhydrophobic membrane prepared in accordance with the present disclosure is evaluated by mechanical properties, physical durability tests, and filtration efficiency with various oil-water mixtures. It is observed that the efficiency of the membrane remains above 99% even after rigorous mechanical and physical durability tests.
Further, the superhydrophobic membrane provides reusability for up to 100 consecutive cycles with a filtration efficiency of above 99%. Thus the superhydrophobic membrane is cost-effective, saving energy and time.
The foregoing description of the embodiments has been provided for purposes of illustration and is not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. These laboratory scale experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial/commercial scale.
EXPERIMENTAL DETAILS
Experiment 1: Process for the preparation of superhydrophobic membrane
0.15 g of dipentaerythritol pentaacrylate, 1 ml of 3-aminopropyl triethoxysilane, and 300 mg of octadecyl acrylate were mixed in 5 ml of toluene under stirring for a time period of 3 hours to obtain a solution. The so obtained solution was spray deposited on a polyurethane membrane (10 x 10 cm2) to obtain a coated membrane. The coated membrane was dried at 60°C in an oven for 3 hours to obtain the dried membrane. The dried membrane was subjected to UV-light treatment (365 nm, 16W) for 1 hour to obtain the superhydrophobic membrane.
Hydrophobicity of the membrane was observed through visual inspection. Contact angles with respect to oil and water were measured with the help of KRUSS Drop Shape Analyser-DSA25 instrument with an automatic liquid dispenser at ambient conditions.
The uncoated polyurethane membrane was both hydrophilic and oleophilic with a water and oil contact angle of 0° as illustrated in Figures 1D to 1G (The stains visible in Figure 1D refer to the soaked water droplets on the polyurethane membrane, the water was dyed with Rhodamine-6g for enhanced visibility). The contact angle of the superhydrophobic membrane of the present disclosure was 155.6°, as illustrated in Figures 1H to 1I, whereas the interface displays selective superoleophilicity with the oil contact angle of ~0°, as illustrated in Figures 1J to 1K.
The superhydrophobic membrane displays a shiny interface when immersed underwater, as illustrated in Figure 1M, which was attributed to the presence of metastable trapped air (Cassie-Baxter State) that confers superhydrophobicity to the material. The uncoated polyurethane membrane doesn't display any shiny surface, as illustrated in Figure 1L.
The superhydrophobic membrane repels water from the surface when placed under the water stream, thus, exhibiting the durable and extreme water repellent property of the coated membrane, whereas the uncoated membrane became wet by absorbing the water, as illustrated in Figures 1N-O.
FTIR analysis:
3-aminopropyltriethoxysilane (AS) undergoes polymerization during the evaporation of the fluid medium through the formation of the Si-O-Si bond. The polymerization of 3-aminopropyltriethoxysilane formed covalent cross-linking with dipentaerythritol pentaacrylate (5Acl) and octadecyl acrylate (ODA). The Fourier-transform infrared spectroscopy (FTIR) characterization analysis identified that the peak at 1076 cm-1 for Si-O-C bond of AS significantly reduced during heating at 60°C and a new peak at 1028 cm-1 was observed due to the formation of Si-O-Si bond which confirms the polymerization of AS, which is illustrated in Figure 2A. The peaks at 1617 cm-1 corresponding to the amine groups of AS, which remains unaffected during the polymerization process, is also illustrated in Figure 2A. These primary amines were available for ready reaction with the acrylate groups of 5Acl and ODA through the 1,4-conjugate addition reaction.
Further, 5Acl was covalently cross-linked with AS polymeric network which imparts superior mechanical durability to the coated membrane (superhydrophobic membrane). The surfactant like OA molecule with acrylate moiety at one end and a hydrophobic chain on the other end imparts the water repellent property to the Superhydrophobic membrane. The successful reaction of AS with 5Acl and ODA was evident from FTIR study where 1409 cm-1 peak corresponds to the C-H bond for ß carbon of the vinyl group of both 5Acl and ODA, that significantly reduced with respect to the carbonyl stretching (1735 cm-1) after reacting with AS polymer at 60°C, which is illustrated in Figure 2B. The unreacted acrylates of 5Acl and ODA are likely to react with each other through 2p+2p cycloaddition reaction after 1 hr of UV treatment.
FEMSEM analysis:
The uniform deposition of the polymeric coating on the fibers of the membrane was evaluated through Field Emission Scanning Electron Microscopy (FESEM), where the featureless and smooth fiber of the polyurethane membrane, as illustrated in Figure 2C were uniformly decorated with granular features which provided the essential hierarchical topography for displaying extreme water repellent property as shown in Figure 2D. Further, the energy-dispersive X-ray spectroscopy (EDX) images revealed that Si was uniformly distributed throughout the coated fibers of the polyurethane membrane, whereas Si was completely absent on the uncoated fibers, which is illustrated in Figures 2E to F.

Study of mechanical strength:
The mechanical strength of the superhydrophobic membrane was characterized by uniaxial stretching experiments.
The pristine membrane and the superhydrophobic membrane prepared in accordance with the present disclosure required 4.1 MPa and 31.3 MPa stress respectively for achieving 150% stretching. The tensile stress-strain curves for pristine membrane and superhydrophobic membrane at the same strain rates revealed that the mechanical strength of the superhydrophobic membrane was several times higher than the pristine membrane, as illustrated in Figure 3A.
The pristine membrane and superhydrophobic membrane of the present disclosure was applied with a load of 500g. The pristine membrane was stretched and damaged, whereas the superhydrophobic membrane became nonstretchable under the same applied load, as illustrated in Figure 3B and 3C respectively. The enhanced mechanical strength of the superhydrophobic membrane was attributed to the chemical cross-linking of the selected reactants.
Abrasive tolerance of the superhydrophobic membrane
The abrasive tolerance of the superhydrophobic membrane was evaluated by severe and standard abrasive tests that disrupt the superhydrophobic properties.
Experiment 2: Sandpaper abrasion test
The superhydrophobic membrane (10 cm x 10 cm) was fixed on a glass slide using adhesive tape. Further, sandpaper (3cm X 1.5 cm) was placed on top of the superhydrophobic membrane with a load of 750g. The sandpaper was rubbed on the superhydrophobic membrane back and forth 50 times, followed by measuring the water wettability by using digital images and contact angle measurements. The abraded interface continued to exhibit extreme water repellant property with a water contact angle of 154.4° and contact angle hysteresis below 10? as illustrated in Figures 4A to C.
Experiment 3: Adhesive tape test
An adhesive tape was fixed onto the superhydrophobic membrane with a load of 750g on top and kept undisturbed for one minute (60 seconds) to ensure uniform contact with the membrane and peeled off. The process was repeated 25 times. The abraded surface was examined through digital images and contact angle measurements. It was observed that the abraded surface displays uninterrupted extreme water-repellent property with a water contact angle (WCA) of 154.3o as illustrated in Figures 4D to F.
Experiment 4: Knife scratch test
The superhydrophobic membrane was scratched arbitrarily by using a sharp-edge knife multiple times. The abraded surface was examined through digital images and contact angle measurements. It was observed that the superhydrophobic property of the superhydrophobic membrane surface remained intact with a water contact angle (WCA) of 154.2o, which is illustrated in Figures 4G to I.
Experiment 5: Sand drop test
250 gm of sand grains were dropped on the superhydrophobic membrane (tilted at ~45°) from a height of ~20 cm. The abraded surface was examined through digital images and contact angle measurements. The integrity and the anti-wetting property of the abraded surface remained unperturbed with a water contact angle (WCA) of 153.8o as illustrated in Figures 4J to M.
Experiment 6: Physical manipulations
The superhydrophobic membrane was subjected to various physical manipulations including winding, creasing, and twisting, as illustrated in Figures 4N to P. The abraded surface was examined through digital images and contact angle measurements. It was observed that the water repellence of superhydrophobic membrane remained unperturbed after the manipulations with the water contact angle (WCA) of 153.8o, which is illustrated in Figures 4Q to R.
Experiment 7:
The superhydrophobic membrane was exposed to harsh aqueous chemical conditions ranging from pH 1 and 12, acidic water (pH 1), basic water (pH 12), river water (Brahmaputra, Assam India), artificial seawater, and continuous UV radiation (at ?max = 254 and 365 nm) for 20 days. Artificial seawater was prepared by mixing MgCl2 (0.226g), MgSO4 (0.325g), NaCl (2,673g), CaCl2 (0.112g) in 100 ml of de-ionized water. The digital images and contact angle measurements were acquired every 3 days to examine the durability of the liquid water wettability of the superhydrophobic membrane. After 20 days it was observed that the water contact angle remained above 150o and the contact angle hysteresis of below 10o. The superhydrophobic property of the membrane remained intact even after continuous exposure to various harsh environments. The acquired advancing water contact (?adv) angle and the contact angle hysteresis (?hys) values at regular intervals are illustrated in Figure 5.
Filtration efficiency: Study of oil-water separation
The superhydrophobic membrane prepared in accordance with the present disclosure was tested for its oil-water separation efficiency. The superhydrophobic membrane was tied at the open end of the lab-made prototype and the oil/water mixtures were poured through the funnel placed at the opposite end of the tied membrane.
The gravity-driven filtration-based oil/water separation for various oils (sediment and floating oils) that are extensively used in general practice were evaluated.
Experiment 8: Separation of dichloromethane
20 ml dichloromethane (model sediment oil-dyed pink for visual inspection) and 20 ml water (dyed blue for visual inspection) were taken in a beaker and poured through the superhydrophobic membrane, as illustrated in Figures 6A to C. The dichloromethane rapidly and selectively permeated through the membrane which was collected in a beaker. The water remained suspended and restricted by the membrane in the falcon tube due to the extremely water-repellent property exhibited by the membrane, which is illustrated in Figure 6D.
Experiment 9: Separation of kerosene
20 ml kerosene (floating oil – dyed blue for visual inspection) and 20 ml water (dyed orange for visual inspection) were taken in a beaker and poured through the superhydrophobic membrane, as illustrated in Figures 6E to G. The kerosene rapidly and selectively permeated through the superhydrophobic membrane that was collected in a beaker. The water remained suspended and restricted by the superhydrophobic membrane in the falcon tube due to the extremely water-repellent property exhibited by the membrane, which is illustrated in Figure 6H.
Experiment 10: Separation of Diesel
20 ml diesel (dyed yellow for visual inspection) and 20 ml water (dyed blue for visual inspection) were taken in a beaker and poured through the superhydrophobic membrane as illustrated in Figures 7A to C. The diesel rapidly and selectively permeated through the membrane that was collected in a beaker. The water remained suspended and restricted by the superhydrophobic membrane in the falcon tube due to the extremely water-repellent property exhibited by the superhydrophobic membrane, which is illustrated in Figure 7D.
Experiment 13: Separation of petrol
20 ml petrol (brownish red) and 20 ml water (dyed blue for visual inspection) were taken in a beaker and poured through the superhydrophobic membrane as illustrated in Figures 7E to G. The petrol rapidly and selectively permeated through the superhydrophobic membrane was collected in a beaker. The water remained suspended and restricted by the superhydrophobic membrane in the falcon tube due to the extremely water-repellent property exhibited by the superhydrophobic membrane which is illustrated in Figure 7H.

Experiment 14: Separation of silicone oil
20 ml silicone oil (dyed pink for visual inspection) and 20ml water (dyed blue for visual inspection) were taken in a beaker and poured through the superhydrophobic membrane as illustrated in Figures 8A to C. The silicone oil rapidly and selectively permeated through the superhydrophobic membrane was collected in a beaker. The water remained suspended and restricted by the membrane in the falcon tube due to the extremely water-repellent property exhibited by the membrane, which is illustrated in Figure 8D.
Oil separation efficiency- calculations
The oil separation efficiency of the superhydrophobic membrane was calculated for various oils (sediment and floating) with varying densities such as chloroform, dichloromethane (DCM), silicon oil, diesel, petrol, kerosene, petroleum ether using the following formula:
Separation Efficiency (?) = (Vr /Vi) X 100
where Vi and Vr are the initial volume of oil taken and the oil recovered after separation, respectively.
The separation efficiency of the superhydrophobic membrane prepared in accordance with the present disclosure remained above 98% irrespective of the densities of the oils used, which is illustrated in Figure 9.
Further, the separation efficiency of the superhydrophobic membrane of the present disclosure was evaluated for petrol and diesel with contaminated water of various harsh chemical conditions including acidic water (pH 1), basic water (pH 12), artificial seawater, river water (Brahmaputra, Assam India), surfactants i.e. sodium dodecyl sulfate (SDS), dodecyltrimethylammonium bromide (DTAB).
It was observed that the oil-water separation efficiency of the membrane was above 99% for different contaminants, illustrated in Figure 10.

Repetitive separation efficiency
The oil separation efficiency of the superhydrophobic membrane was evaluated by performing oil/water separation using petrol and diesel for 100 consecutive cycles. It was observed that the separation efficiency of the superhydrophobic membrane remained above 99% throughout these 100 consecutive cycles as illustrated in Figure 11, establishing the excellent reusability of the superhydrophobic membrane.
The anti-wetting property was also evaluated after every 20 cycles of reuse, it was observed that the anti-wetting property remained intact with an advancing contact angle of >150° and contact angle hysteresis of <10° during the 100 cycles of repetitive separation process for both petrol and diesel as illustrated in Figure 12.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization and a process for the preparation of a superhydrophobic membrane which
- involves single step for preparation,
- use of small molecules;
- resists deformation of a highly deformable membrane;
- easy to scale up;
- requires no post chemical modification treatment;
- produces superhydrophobic membrane which is durable, eco-friendly, non-toxic, and energy-efficient;
- maintains separation efficiency and anti-wetting property of the superhydrophobic membrane even after 100 consecutive cycles;
- highly efficient oil/water separation of the superhydrophobic membrane under gravity; and
- suitable for use at harsh chemical conditions of pH 1- 12.
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.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions, and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

,CLAIMS:We Claim:
1. A process for the preparation of a superhydrophobic membrane, said process comprising the following steps:
a) mixing predetermined amounts of at least two acrylates and at least one aminosilane in a fluid medium under stirring for a time period in the range of 2 hours to 5 hours to obtain a solution;
b) coating said solution on a membrane to obtain a coated membrane;
c) drying said coated membrane at a predetermined temperature for a first predetermined time period to obtain a dried membrane; and
d) subjecting said dried membrane to electromagnetic radiation for a second predetermined time period to obtain a superhydrophobic membrane.
2. The process as claimed in claim 1, wherein said acrylate is selected from dipentaerythritol pentaacrylate, octadecyl acrylate, and combinations thereof.
3. The process as claimed in claim 1, wherein said aminosilane is selected from 3-aminopropyltriethoxysilane, [3-(2-Aminoethylamino)propyl]trimethoxy silane, and (3-Aminopropyl)trimethoxysilane.
4. The process as claimed in claim 1, wherein the molar ratio of said acrylate to said aminosilane is in the range of 1:2 to 1:4.
5. The process as claimed in claim 1, wherein the molar ratio of dipentaerythritol pentaacrylate to 3-aminopropyl triethoxysilane to octadecyl acrylate is 1:15:3.
6. The process as claimed in claim 1, wherein said fluid medium is selected from toluene, ethanol, acetone, and pentanol.
7. The process as claimed in claim 1, wherein said coating is carried out by a method selected from spray deposition, dip coating.
8. The process as claimed in claim 1, wherein said membrane is selected from polyurethane, cotton fabric, jute, and silk.
9. The process as claimed in claim 1, wherein said predetermined temperature is in the range of 50oC to 80oC.
10. The process as claimed in claim 1, wherein said first predetermined time period is in the range of 2 hours to 4 hours.
11. The process as claimed in claim 1, wherein said electromagnetic radiation is selected from UV radiation, sunlight,
12. The process as claimed in claim 1, wherein said second predetermined time period is in the range of 1 hour to 3 hours.
13. A superhydrophobic membrane is characterized by having:
a. water contact angle in the range of 154° to 157°;
b. enables to resist the deformation of a highly deformable membrane due to coating; and
c. filtration efficiency of 99% even after 100 consecutive cycles of separation.

Dated this 5th Day of February, 2021

MOHAN RAJKUMAR DEWAN, IN/PA-25
of R.K. DEWAN & COMPANY
APPLICANT’S PATENT ATTORNEY

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT CHENNAI