TECHNICAL FIELD

[0001 ] The present application is in the filed of materials and methods for separating water from oil. More specifically, the present application relates to oil-water separator filters combining nanoparticles and soot impregnated on sponges, and methods for preparing the same.

BACKGROUND

[0002] In recent years, oil leakage and organic chemicals coming from many industries are causing substantial water pollution and have emerged as a global problem imposing a threat to the environment. Expansion in oil production and transportation in the last few decades have caused a fast growth in chemical spillage from oil tankers or ships and industrial accidents. This imparts a catastrophic effect on the aquatic and marine ecosystems.

[0003] Consequently, many mammals and seabirds have died and seaweed has also suffered heavy damage. Therefore, there is a need to modify existing materials or develop new materials for the removal of various oil-based contaminants from water.

[0004] Conventionally used methods for removing oil from water include chemical dispersants, bioremediation, mechanical collection, and adsorbent materials. Recently, materials with hydrophobic and hydrophilic properties have lead researches to develop oilwater separators.

[0005] Carbon nanotubes, filter paper, mesh films, and graphene have all been used for removing oil from water. ^{1 -7} Some foam based adsorbents coated with carbon can be used for multiple times without losing carbon particles into water. ^8-11 It is noted that carbon is also known for its good adsorbent properties.

[0006] Activated carbon, graphene, and carbon derived from various waste materials like coconut shells and peanut hulls are known for adsorbing toxic organic compounds such as various dyes from wastewater. ^12-15 In this direction, candle soot has been successfully examined as an adsorbent of two cationic dyes, rhodamine B (RB) and methylene blue (MB). ¹⁶

[0007] As such, there is a need to develop new materials suitable to be used as nanofilters for oil-water separation. There is a need for nanofilters that are reusable, have extended surface area for better removal capacity, are stable in various conditions, and may be produced in large scale and at a low cost.

SUMMARY

[0008] It has been surprisingly shown herein that nanofilters of the present application provide high removal capacity of oil in water, while being reusable, stable at various pH and temperature conditions and being suitable for large scales at low cost. The processes of the present application further provide for the fabrication of such nanofilters. Comparable nanofilters and processes did not display the same properties, highlighting the surprising results obtained with the nanofilters and processes of the application.

[0009] Accordingly, the present application includes a nanofilter for oil-water separation, the nanofilter comprising: one or more hydrophobic nanoparticles; an amorphous carbon; a support comprising a polymeric sponge or a fabric; wherein the one or more hydrophobic nanoparticles and the amorphous carbon are impregnated on the support to provide the nanofilter.

[0010] The present application also provides a method for producing a nanofilter for oil-water separation, the method comprising: impregnating one or more hydrophobic nanoparticles and amorphous carbon on a support by sonication to provide an impregnated support; optionally drying the impregnated support to provide the nanofilter.

[0011 ] The present application further includes a method for selective separation of oil contaminants from water, the method comprising: contacting a contaminated water with a nanofilter under conditions for adsorption of the oil contaminants on the nanofilter; removing the nanofilter adsorbed with the oil contaminants from the water to provide filtered water; optionally extracting the oil contaminants from the nanofilter and recycling the nanofilter for further separation; wherein the nanofilter comprises one or more hydrophobic nanoparticles; an amorphous carbon; a support comprising a polymeric sponge or a fabric; wherein the one or more hydrophobic nanoparticles and the amorphous carbon are impregnated on the support to provide the nanofilter.

[0012] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope of the claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole.

DETAILED DESCRIPTION

I. Definitions

[0013] Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.

[0014] As used in this application and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0015] The term “consisting” and its derivatives as used herein are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and/or steps.

[0016] The term “consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and/or steps as well as those that do not materially affect the basic and novel characteristic(s) of these features, elements, components, groups, integers, and/or steps.

[0017] The terms "about", “substantially” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies or unless the context suggests otherwise to a person skilled in the art.

[0018] As used in the present application, the singular forms “a”, “an” and “the” include plural references unless the content clearly dictates otherwise. [0019] The term “and/or” as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that “at least one of” or “one or more” of the listed items is used or present.

[0020] The term “nanoparticles” as used herein means an ultrafine particle of about 1 to about 100 nanometers in diameter.

[0021 ] The term “nanofilter” as used herein means a filtration membrane or device based on nanometer sized technology.

[0022] The term “hydrophobic” as used herein refers to the physical property of a molecule or substance that is seemingly repelled from water.

[0023] The term “soot” as used herein generally refers to carbon particles, typically amorphous carbon, resulting from the incomplete combustion of hydrocarbons.

[0024] The term “sponge” as used herein refers to a structure comprising pores or channels allowing fluid to circulate through them or be retained therein, and refers to a synthetic sponge or a natural sponge.

[0025] The term “fabric” as used herein refers to a a flexible material made by creating an interlocking network of yarns and/or threads, which are produced by spinning raw fibers, from either natural or synthetic source, into long and twisted lengths. Fabrics are made through weaving, knitting, spreading, felting, stitching, crocheting or bonding and may be used in the production of further products.

II. Nanofilters of the Application

[0026] It has been surprisingly shown herein that nanofilters of the present application provide high removal capacity of oil from water, while being reusable, stable at various pH and temperature conditions and being suitable for large scales at low cost. Comparable nanofilters did not display the same properties, highlighting the surprising results obtained with the nanofilters of the application.

[0027] Accordingly, the present application includes a nanofilter for oil-water separation, the nanofilter comprising: one or more hydrophobic nanoparticles; an amorphous carbon; a support comprising a polymeric sponge or a fabric; wherein the one or more hydrophobic nanoparticles and the amorphous carbon are impregnated on the support to provide the nanofilter.

[0028] In some embodiments, the one or more hydrophobic nanoparticles comprises hydrophobic TiO ₂ nanoparticles. In some embodiments, the one or more hydrophobic nanoparticles comprises an alkyl-capped TiO2 modified with perfluorocarboxylic acid. In some embodiments, the perfluorocarboxylic acid has the formula CnF(2n+i)CO2H. In some embodiments, n is an integer from 1 to 20. In some embodiments, the perfluorocarboxylic acid is perfluorooctanoic acid, perfluorononanic acid, perfluoroheptanoic acid, perfluorohexanoic acid, perfluoropentanoic acid, perfluorobutanoic acid, perfluoropropanoic acid, perfluoroethanoic acid, or trifluoroacetic acid. In some embodiments, the perfluorocarboxylic acid is trifluoroacetic acid. In some embodiments, the alkyl-capped TiO ₂ comprises an hydroxyCi ealkyl fatty acid ester deposited on TiO2. In some embodiments, the fatty acid is a saturated or unsaturated unbranched chain from 4 to 28 carbon atoms. In some embodiments, the fatty acid ester is a oleate, linoleate, palmitate, caprate, laurate, caproate, caprylate, or the like. In some embodiments, the fatty acid ester is oleate. In some embodiments, the alkyl-capped TiO ₂ comprises hydroxyethyloleate deposited on TiO2.

[0029] In some embodiments, the amorphous carbon comprises soot. In some embodiments, the amorphous carbon comprises a diesel exhaust soot, candle soot, graphene, carbon derived from various waste materials like coconut shell and/or peanuts’ hull, waste engine oil or waste tires.

[0030] In some embodiments, the support comprises a polymeric sponge or a fabric. In some embodiments, the polymeric sponge comprises a synthetic sponge or a natural sponge. In some embodiments, the synthetic sponge is selected from a melamine sponge, a polyurethane sponge, a polyester sponge and a polycarbonate sponge. In some embodiments, the natural sponge is a plant fiber sponge or an animal fiber sponge. In some embodiments, the fabric is made from fibers from animals such as wool, angora, mohair and/or silk, plant such as cotton, flax, hemp, sisal, jute and/or bamboo, mineral such as asbestos and/or glass fiber, or synthetic such as nylon, polyester, acrylic and/or rayon.

[0031 ] In some embodiments, the ratio of amorphous carbon to polymeric sponge is about 1 :1 to about 4:1 , in weight by weigth (w/w). In some embodiments, the ratio of amorphous carbon to polymeric sponge is about 1 :1 to about 3:1 . In some embodiments, the ratio of amorphous carbon to polymeric sponge is about 2:1 to about 3:1 .

[0032] In some embodiments, the ratio of amorphous carbon to hydrophobic nanoparticles is about 40:1 to about 60:1 (w/w). In some embodiments, the ratio of amorphous carbon to hydrophobic nanoparticles is about 50:1 .

[0033] In some embodiments, the ratio of hydrophobic nanoparticles to polymeric sponge is about 40:1 to about 70:1 (w/w). In some embodiments, the ratio of hydrophobic nanoparticles to polymeric sponge is about 45:1 to about 65:1 , or about 50:1 to about 60:1 .

[0034] In some embodiments, the ratio of amorphous carbomhydrophobic nanoparticles:polymeric sponge is about 20:1 :40 to about 45:1 :70 (w/w). In some embodiments, the ratio of amorphous carbomhydrophobic nanoparticles:polymeric sponge is about 25:1 :45 to about 40:1 :65, or about 30:1 :50 to about 35:1 :60.

[0035] In some embodiments, the nanofilter provides removal of at least 98% of oil contaminants present in water. In some embodiments, the nanofilter provides removal of at least 99% of oil contaminants present in water. In some embodiments, the nanofilter provides removal of at least 98% of oil contaminants present in water.

[0036] Without being bound to theory, the use of soot as the amorphous carbon provides for an inexpensive solution to produce more efficient and effective nanofilters. The nanofilters herein produced are stable under various conditions, such as different pH and/or elevated temperatures, and are reusable in multiple seperation cycles. Again, without being bound to theory, the use of soot as the amorphous carbon provides a nanofilter removing at least 98% of oil contaminants, which is a significant improvement over known filters or nanofilters. In some embodiments, the absorption capacity or removal capacity of the nanofilters of the present application is stable and effective in absorbing a wide range of oils with good recyclability. In some embodiments, the nanofilters of the application are used in environmental remediation to eliminate various contaminants from water.

III. Methods of Preparing the Nanofilters of the Application

[0037] The present application further includes a method for producing a nanofilter for oilwater separation, the method comprising: impregnating one or more hydrophobic nanoparticles and an amorphous carbon on a support by sonication to provide an impregnated support; optionally photografting a surface of the impregnated support by irradiation; optionally drying the impregnated support to provide the nanofilter.

[0038] In some embodiments, the one or more hydrophobic nanoparticles are prepared according to methods known in the art.

[0039] In some embodiments, impregnating one or more hydrophobic nanoparticles and an amorphous carbon on a support by sonication to provide an impregnated support is conducted at a frequency of about 20 kHz to about 50 kHz at 50 W. In some embodiments, the frequency is about 25 kHz to about 45 kHz, or about 30 kHz to about 40 kHz. In some embodiments, the sonication is conducted for about 30 minutes to about 100 minutes. In some embodiments, the sonication is conducted for about 40 minutes to about 90 minutes. In some embodiments, the sonication is conducted for about 50 minutes to about 80 minutes. In some embodiments, the sonication is conducted for about 70 minutes.

[0040] In some embodiments, a photografting step is conducted. Without being bound to theory, photografting increases the adherence of the nanoparticles at the surface of the support thus decreasing the leaching of the nanoparticles, for greater stability. In some embodiments, the photografting comprises irradiating the surface in the presence of at least one monomer for photopolymerization at the surface. In some embodiments, the monomer is phenylethylene, divinylbenzene, vinyl chloride, styrene or a mixture thereof. In some embodiments, irradiation is conducted for about 3 hours to about 7 hours. In some embodiments, irradiation is conducted for about 4 hours to about 6 hours. In some embodiments, drying the impregnated support is conducted for about 5 hours.

[0041 ] In some embodiments, the impregnated support is dried to provide the nanofilter. In some embodiments, drying the impregnated support is conducted at a temperature of about 40 °C to about 80 °C. In some embodiments, drying the impregnated support is conducted at a temperature of about 50 °C to about 70 °C. In some embodiments, drying the impregnated support is conducted at a temperature of about 55 °C to about 65 °C. In some embodiments, drying the impregnated support is conducted for about 1 hour to about 3 hours. In some embodiments, drying the impregnated support is conducted for about 1 .5 hours to about 2.5 hours. In some embodiments, drying the impregnated support is conducted for about 2 hours.

IV. Methods and Uses of the Application [0042] Also provided is use of a nanofilter of the present application, for selectively separating oil contaminants from water.

[0043] In some embodiments, the oil conatminants are crude oil, diesel, engine oil, petrol oil, or the like.

[0044] In some embodiments, the nanofilter is integrated within a filtration apparatus. In some embodiments, the filtration apparatus is a floating device. In some embodiments, the floating device is as disclosed in WO2017130032.

[0045] The present application further includes a method for selective separation of oil contaminants from water, the method comprising: contacting a contaminated water with a nanofilter of the present application under conditions for adsorption of the oil contaminants on the nanofilter; removing the nanofilter adsorbed with the oil contaminants from the water to provide filtered water; optionally extracting the oil contaminants from the nanofilter and recycling the nanofilter for further separation.

[0046] In some embodiments, adsorption of the oil contaminants on the nanofilter substantially retains total solids dissolved in water.

EXAMPLES

[0047] The following non-limiting examples are illustrative of the present application.

EXAMPLE 1

Preparation of nano-filter a. Preparation of TiO ₂ nanoparticles:

[0048] In a typical procedure, a piece of commercial filter paper was placed in a suction filtering unit and washed with ethanol, followed by drying with air flow. Three milliliters of titanium tetraisopropoxide (TTIP, 98%) was added to 20 mL of isopropyl alcohol with stirring. The pH value of the solution was adjusted to 1 -2 using36-38% HCI solution. In another container, 0.3 mL of deionized water was addedto 5 mL of isopropyl alcohol under stirring.

[0049] The above two solutions were added dropwise into the filter paper alternatively. After, 40 mL of ethanol was then immediately filtered to removethe unreacted metal alkoxide. Then the filter papers were dried with airflow. By the process of filtration/deposition, thin titania gel layers were deposited on the morphologically complex surface of paper. Finally, the resultant paper/titania composites were calcined in air at 723 K for 6 h to remove the original filter paper and form the TiO ₂ nanoparticles. b. Synthesis of alkyl-chain-capped TiO2 nano-particles (OC-TiO ₂ ):

[0050] 2.0 g of the TiO ₂ nanoparticles was added to 80 g of degassed oleic acid and allowed to stir for 10 min. 20 mmol of tributylamine in 9.5 g of 1 ,2-ethandiol wassubsequently added. Then, the solution was maintained in a close system at 180 °C for 7 h. Subsequently, the 2- hydroxyethyloleate-capped TiO ₂ nanoparticles (OC-TiO ₂ ) were rapidly precipitated with addition of excess of ethanol. c. Perfluorocarboxylic acid (PFOA) modified the nano-OC-Ti02 (PFOC-TiO ₂ ):

[0051 ] 1 g of OC-TiO2, 25 ml of perfluorocarboxylic acid and 40 ml isopropanol were mixed through sonication. Subsequently, the mixture was refluxed at 80 °C for 4 h and then the nanoparticles (PFOC-TiO ₂ ) filtered and washed with isopropanol. d. Preparation of nano-based TiO ₂ filter:

[0052] A commercial melamine sponge was cut into blocks (2x2x1 cm ³ ), and ultrasonically cleaned in ethanol. Then, the blocks were rinsed with distilled water and dried at 70 °C. After routine solvent cleaning, the blocks were then dipped into the solution containing 250 ml H2O distilled water, 20mg of PFOC-TiO ₂ and 1 .0 g of diesel exhaust soot, and sonicated (Q2000 Sonicator, 2,000 Watts with the dimension 7" H x 15" W x 18.25" D) for 70 min. e. Sponge Photografting

[0053] The prepared sponge was dried at 50°C in an oven for 60 min. A certain amount of the result powder (at least 0.1 g) was dry-pressed in a steel die to forma pellet with a 13 mm diameter. Then it was immersed in a glass tank (1 .0 cm ³ ) containing 2 mL of phenylethylene and 6 mL of divinylbenzene, and irradiated with 100 WHg lamp under nitrogen atmosphere for 5 h. After the self-initiated photografting and photopolymerization were performed, the obtained materials were successively washed with toluene, ethyl acetate, and ethanol, and finally dried in oven at 60°C for 2 h.

Preparation of nano-based TiO ₂ fabric [0054] Similar procedure as in steps a-c were conducted. In step d., the polymeric sponge was replaced by a polystyrene fabric to provide the nano-based TiO ₂ impregnated on fabric.

Oil uptake on sponge

[0055] For measuring oil uptake, the filter was installed as the following:

[0056] The sponge with a known initial dry weight (1 .0 g) was dipped into a mixture of the crude oil/water until it became saturated with the oil. Then, the sorbent sponge was removed using a pair of tweezers, drained for 2 min and squeezed to remove oil.

[0057] The corresponding results, based on the total organic content (TOC), expressed in % of organic material removed, are illustrated in the Tables 1 -5.

Table 1 . Optimization of the Amount of Soot/Sponge for Crude Oil Removal after 5 min:

Table 2. Optimization of the Amount of Adsorbent for Crude Oil Removal after 5 min:

Table 3. Reusability of the Adsorbent for Crude Oil Removal after 5min: Table 4. Optimization for DifferentConcentrations of Crude Oil in Water after 5 min:

Table 5. Ability of the Adsorbent for Removal of otherOrganic Contaminants in Water after 5 min:

Oil uptake on fabric

[0058] The separation experiment of a mixture of crude oil (2.0 ml) in water (150.0 ml) was performed as described above, but the fabric was fixed by a cable tie on a small beaker. The mixture was gradually poured on the fabric and passed through the fabric into the small beaker upon gravity and tension forces, and the liquid dripped into the beaker was collected for analysis.

[0059] The corresponding results based on the total organic content (TOC) is illustrated in the Table 6.

Table 6. Evaluation of Crude Oil Removal from Water Utilizing 0.5 g of the Fabric after 5 min:

[0060] For both approaches, using a sponge or a fabric as the support, the removal capacity (RC) was calculated upon theTOC (Total Organic Compound) of the aqueous phase. [0061 ] Also, the above investigation was repeated using the optimized method in large scale separation. Based on the study, 5 L of crude oil utilizing the fabric (98% removal percent) and the sponge (99 % removal percent) was separated from 50 L of the water-crude oil mixture.

[0062] While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments as the embodiments described herein are intended to be examples. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments described herein, the general scope of which is defined in the appended claims.

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