Separation operations of liquid mixtures (immiscible or miscible) span across numerous manufacturing industries including petrochemicals, textiles, leather, wastewater treatment and biofuel production. According to a recent report, separation operations account for a quarter of all in-plant energy consumption in the United States.
One of the most ubiquitous immiscible liquid mixtures is oil and water. A large amount of oily wastewater is produced every day during industrial processing. The effect of this wastewater on the environment can be severe, unless it is adequately treated before discharge, as can be observed from the many recent oil-spill disasters. In addition, shortage of freshwater has become a severe problem in the world, especially in certain underdeveloped regions. Purification of oily wastewater can enhance the amount of water available for use. Furthermore, expulsion of water from fuel oil is of great concern in petroleum and automobile industries because even a small amount of water in the fuel oil may damage engines, threatening the safety of the automobile.
The separation of miscible liquid mixtures is also important in many industries. For example, in the petroleum refining process, small amounts of miscible impurities including sulfur, nitrogen and metal compounds are separated from crude oil to produce fuel oil. Similarly, the high quality of biofuels such as bioethanol or biodiesel can only be produced by removing dissolved byproducts generated during the separation process. In addition, recovery of organic acids from agroindustrial wastewater is essential not only for environmental requirements, but also for economic benefits.
A large number of methodologies including distillation, liquid-liquid extraction and membranes have been used to separate miscible or immiscible liquid mixtures. Distillation separates components from a mixture based on differences in their boiling points. Since distillation is a simple and well-established technology, it is by far the most widely used separation process. However, distillation has low energy efficiency and it requires thermal stability of compounds at their boiling points. In addition, it is not suitable for the separation of components with similar boiling points such as azeotropes.
Liquid-liquid extraction is typically used to separate azeotropes and components with overlapping boiling points where simple distillation cannot be used. Liquid-liquid extraction is a separation technique that separates components of a liquid mixture by contact with another insoluble liquid. Components in a liquid mixture are separated based on their difference in solubility with the insoluble liquid. One primary challenge in liquid-liquid extraction is to increase contact between the two liquid phases for efficient mass transfer. This is typically achieved by employing energy-intensive ultrasonication or pumping the two liquids through packed columns with high tortuosity.
Membrane-based technologies physically separate a liquid mixture into its components by allowing one phase to permeate through the membrane while retaining the other component. Since the separation is performed at ambient temperature without chemically altering the components, membrane-based separation operations consume less energy than other separation methods. However, membranes can be fouled by particulates or organic matters during the separation operation, which results in a decline of the permeability.
Absorption can be a useful alternative for the separation of either miscible or immiscible liquid mixtures. Embodiments of absorption techniques are described herein for the purpose of separating miscible and/or immiscible liquid mixtures.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify the critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented herein.
In one embodiment, a hydrogel has effective amounts of: N-ispropylacrylamide (NIPAM); N,N′ Methylenebisacrylamide (MBAA); 2-hydroxy-2-methylpropiophenone; and 1H,1H,2H,2H-perfluorodecyl acrylate. The hydrogel has the following chemical structure:
In another embodiment, a method for synthesizing a hydrogel includes the steps of: (a) dissolving N-isopropylacrylamide, N,N′ Methylenebisacrylamide (MBAA) and 2-hydroxy-2-methylpropiophenone in deionized water to form a NIPAM solution; (b) preparing a solution of 1H,1H,2H,2H-Perfluorodecyl acrylate in ethanol; (c) separately stirring the solutions prepared in steps (a) and (b) for approximately three hours; (c) gradually introducing the solution from step (b) into the solution from step (a); (d) stirring the resulting solution from step (c) for about two hours; and (e) pouring the resulting solution from step (d) into a mold and irradiating with UV-A (λ=365 nm) for about 15 minutes.
In still another embodiment, methods for synthesizing a hydrogel are disclosed. The method includes the steps of: (a) dissolving effective amounts of a monomer, a crosslinker, and a photoinitiator in deionized water, wherein the overall concentration is about 200 mg/ml; (b) preparing a solution of a fluorinated acrylate or diacrylate in ethanol wherein the overall concentration is about 200 mg/ml; (c) separately stirring the solutions prepared in steps (a) and (b) for approximately three hours; (c) gradually introducing the solution from step (b) into the solution from step (a); (d) stirring the resulting solution from step (c) for about two hours; and (e) exposing the solution from step (d) to UV-A irradiation for about 15 minutes.
Described herein are hydrogels with selective wettability of water (polar liquid) over oil (non-polar liquid) and methods for synthesizing same. As is described in greater detail below, the hydrogels set forth herein may selectively absorb polar liquid while repel non-polar liquid. Utilizing such a highly selective absorption behavior, it may be possible to almost completely separate both immiscible oil-water mixtures and miscible polar-non-polar liquid mixtures.
A hydrogel is a three-dimensional polymer that can hold water in its network when submerged in water. Due to such a unique ability to absorb water, hydrogels have been widely studied and applied in a range of applications. Common examples of hydrogels are polyethylene glycol (PEG), polyvinyl alcohol (PVA), hydroxypropyl cellulose (HPC), polyacrylamide (PAM), etc.
Poly N-isopropylacrylamide (PNIPAM) is a thermo-responsive hydrogel that can show different water absorption behavior as a function of temperature. For example, PNIPAM readily gets wet by water (that is, hydrophilic) and absorbs it at a relatively lower temperature (T<32° C.). At an elevated temperature (T>32° C.), PNIPAM becomes hydrophobic (that is, repellent to water) and releases water retained within its network. The temperature (T=32° C.) at which PNIPAM undergoes the transition between absorbing and releasing water is known as lower critical transition temperature (LCST). Such a thermo-responsive switching of water-wettability of PNIPAM has led to several reports of separating oil-water mixtures upon heating and cooling. However, these reports often failed to characterize the wettability (or absorption) of oils by the PNIPAM. Almost all hydrogel is hydrophilic and oleophilic (wet by oil) unless it is carefully designed and synthesized to possess selective wettability. The hydrogels described herein uniquely exhibit in-air hyrophilicity and oleophobicity.
Liquids can be considered either polar or non-polar. Polar liquids (such as water, alcohols and acetone) possess a dipole in their molecules, while non-polar liquids (such as alkanes, benzene, toluene, etc.) do not. Typically, polar (e.g., water) and non-polar (e.g., oil) liquids do not mix together. They form two separate phases when they contact each other. However, there are a few pairs of polar and non-polar liquids that are completely miscible.
One of the well-known examples of an immiscible liquid mixture is oil and water. Oil-water mixtures are classified, in terms of the diameter (d) of the dispersed phase, as free oil and water if d>150 μm, a dispersion if 20 μm<d<150 μm, or an emulsion if d<20 μm. When a surfactant is introduced, the stability of an oil-water mixture is significantly enhanced. This is because surfactant can effectively lower the interfacial tension (γow) of oil and water. Examples of surfactants that are typically used to stabilize oil-water emulsions (or dispersions) include but are not limited to sodium dodecylsulfate (SDS), Sorbitan monooleate (e.g., Tween80, Span80, Span120, etc.), and Sorbitan monolaurate (e.g., Tween20, Span20, Tween21, etc.).
In some cases, polar and non-polar liquids can completely mix together to form a homogeneous single phase. Examples of such miscible mixtures are ethanol-heptane, butanol-hexane and methanol-diesel fuel. These miscible liquids can be found in various industrial process including biodiesel production, jet fuel purification and pharmaceutical process.
Distillation is widely used to separate the miscible liquid mixtures. However, the disadvantages of distillation include its low energy efficiency and that it requires thermal stability of compounds at their boiling points. Large energy savings could be obtained by replacing distillation with low-energy intensity operations, such as absorption.
In one example of the invention, a simple free radical polymerization method initiated with ultraviolet (UV) light to synthesize fluorinated PNIPAM (F-PNIPAM) was employed. First, N-isopropylacrylamide (NIPAM), N, N′ Methylenebisacrylamide (MBAA), and Darocur1173 (2-hydroxy-2-methylpropiophenone) were dissolved in deionized (DI) water in 97:1:2 weight ratio (NIPAM solution). NIPAM, MBAA and Darocur1173 are monomer, crosslinker and photoinitiator, respectively. The overall concentration of the solution is about 200 mg/ml.
A solution of 1H,1H,2H,2H-Perfluorodecyl acrylate (perfluoro acrylate solution, or F-acrylate) was separately prepared in ethanol with substantially the same concentration (e.g., about 200 mg/ml). The prepared solutions are then separately stirred for about 3 hours using a mechanical stirrer in dark conditions to prevent light exposure and unexpected cross-linking. Subsequently, perfluoro acrylate solution is gradually introduced to the NIPAM solution, followed by a vigorous stirring for about 2 hours. The ratio of 1H,1H,2H,2H-Perfluorodecyl acrylate and NIPAM is maintained at 9:1. The solution was then poured into a cubical mold (1.2 cm×1.2 cm) followed by UV-A (λ=365 nm) irradiation for 15 mins. This leads to photoinitiation of free radical polymerization and crosslinking.
It shall be noted that 1H,1H,2H,2H-Perfluorodecyl acrylate (F-acrylate) can be replaced by other fluorinated acrylates (or diacrylates) including but not limited to 1H,1H,6H,6H-Perfluoro-1,6-hexandiol diacrylate, 1H,1H-perfluoro-n-octyl methacrylate, and 1H,1H-perfluoro-n-octyl acrylate, all of which are contemplated within the scope of the invention.
Fourier-transform infrared spectroscopy (FTIR) was used to identify the chemical structure of F-PNIPAM and to ensure the copolymerization of PNIPAM with F-acrylate. Before conducting the FTIR analysis, a F-PNIPAM film, prepared by drop casting on a glass slide, was dried to remove the water vapor present in the film. The sample was then scanned at the rate of 5 cm−1 resolution and the absorption peaks were monitored and compared with the absorption peaks of NIPAM and F-acrylate.
The peaks between 1,200 cm−1 and 1,250 cm−1 in F-PNIPAM spectrum in
Energy Dispersive X-ray Spectroscopy (EDS) was performed to determine the surface chemistry of F-PNIPAM. EDS was performed in conjunction with Scanning Electron Microscope (SEM).
The wettability switch of the F-PNIPAM with a change in ambient temperature was studied. First, a thin film of 10 wt. % F-PNIPAM was fabricated on a small piece of glass. Contact angles (θ) for water, ethanol, hexadecane, and heptane were determined at room temperature (T=21° C.) and at elevated temperature (T=40° C.). At room temperature, it was found that the water and ethanol contact angle (θ) is 0° whereas that of hexadecane is 90° and heptane is 70° (
Referring now to
The wettability of F-PNIPAM copolymerized with various compositions of F-acrylate was also studied.
Surprisingly, it was determined that the F-PNIPAM can reversibly switch its wettability to water by repeated heating-cooling cycles, while maintaining its oil repellency.
The LCST of PNIPAM can be altered by co-polymerization. Copolymerizing with hydrophilic materials typically increases the LCST of PNIPAM, whereas hydrophobic materials can result in a decrease in LCST. Various characterization methods have been utilized to determine LCST of copolymerized PNIPAM including Differential Scanning calorimetry (DSC), cloud point, and UV-Vis spectrometry to characterize turbidity and light scattering. Here, DSC was used to determine the LCST of the F-PNIPAM.
The shift in the corresponding endothermic peaks can be attributed to the copolymerization of PNIPAM with hydrophobic F-acrylate. The lower value of LCST for the F-NIPAM is favorable to release and collect the absorbed liquid (water) at a lower temperature.
The Owens-Wendt method utilizes the Young's relation (Eqn. 1) and the Fowke's postulation (Eqn. 2) to estimate the surface energy (γSV) from the liquid contact angles.
Here, γSVd is the dispersive component that accounts for the dispersive forces while γSVp is the polar component that accounts for polar forces such as hydrogen-bond or dipole-dipole interaction. The table below shows the surface energy of F-NIPAM. To calculate the dispersive component (γSVd), the contact angle (OHD) and surface tension of hexadecane (γHD=27.5 mN/m) were used in Eqn. 4. The calculated dispersive component (γSVd) along with the water contact angle were used to calculate the polar component of surface energy (γSVp) using Eqn. 5. Here, the dispersive and polar components of water surface tension are γLVd=21.1 mN/m and γLVp=51.0 mN/m, respectively. The total surface energy (γSV) of F-NIPAM is calculated by summing up the dispersive and polar surface energy components.
Adding fluorinated materials to a surface lowers the surface energy. Therefore, the surface energy of the F-PNIPAM can be lowered by increasing the wt. % of F-acrylate. This results in higher contact angles for contacting liquids. The hexadecane and water contact angles on F-NIPAM were used to calculate the surface energy. The surface energy of F-NIPAM decreases with increasing the F-acrylate composition, as shown in
Absorption tests were conducted to verify that the F-PNIPAM can selectively absorb polar liquid (water) while repelling non-polar liquid (oil). First, F-PNIPAM cubes were fabricated. Subsequently, the prepared F-PNIPAM cube was completely submerged in a desired liquid bath. After 1 hour, the weight of F-PNIPAM cube was measured and normalized against an as-prepared cube.
It was also found that the F-PNIPAM can absorb approximately 1.3 times more polar liquids as compared with a neat PNIPAM cube. This is because of a so-called ‘loosened’ NIPAM polymer network of the F-PNIPAM due to the presence of perfluoro acrylate. Such a loosened polymer network can be also obtained by reducing crosslinking density.
In order to verify this, multiple F-PNIPAM cubes with different concentration of crosslinker (MBAA) were fabricated. Here 0.5 wt %, 2.0 wt %, 4.0 wt % and 6.0 wt % of MBAA were used.
Time-dependent absorption of polar liquids of the F-PNIPAM was also observed.
It has been demonstrated that the F-PNIPAM can absorb various polar liquids such as alcohols and water whereas non-polar liquids are not absorbed. Therefore, the F-PNIPAM may separate oil-water mixtures by selectively absorbing water. To illustrate, in a first instance, a free hexadecane and water with 50:50 vol %:vol % solution was first prepared. In the example, a total volume of the hexadecane-water mixture is about 4 mL. Subsequently the F-PNIPAM is completely submerged in the hexadecane-water mixture. After approximately 80 mins, it was observed that the F-PNIPAM can selectively absorb blue-dyed water from hexadecane-water mixture resulting in almost complete separation as shown in
In a second instance, a free hexadecane and water solution (50:50 vol %, total volume of about 6 mL) was prepared for separation using F-PNIPAM. The separation is illustrated in
where S.R.eq indicates the equilibrium swelling ratio and S.R. is the swelling ratio at a time (t). In 15 minutes, the separation efficiency was found to be about 99%.
To determine the separation efficiency using thermogravimetric analysis (TGA), about 16 mg of a liquid was heated from 25° C. to 105° C. at a rate of 5° C./min and the temperature was held constant at 105° C. for 10 minutes.
Decreasing the submerged area of F-PNIPAM results in a slower swelling. This is because water is absorbed less when the submerged area is low. Although the swelling rate is affected by the submerged area, F-PNIPAMs could effectively reach to their equilibrium swelling after 120 minutes.
So far it has been shown that the F-PNIPAM can absorb only polar liquids while repel non-polar liquids. This allows for almost complete separation of water from an immiscible oil-water mixture by selective absorption. Separating immiscible liquid mixtures (oil-water) via selective absorption using a sponge-like gel is relatively easy and has been demonstrated in literature. However, the separation of miscible liquid mixtures such as alcohol-alkane or alcohol-water through selective absorption of one phase over another is more challenging. Unlike immiscible liquids, miscible liquids typically possess similar physical or chemical properties.
The F-PNIPAM was also tested for its ability to separate a miscible ethanol-heptane mixture. Note that ethanol and heptane are completely miscible. A 3 mL mixture of heptane and ethanol (2:1 vol %:vol %) was first prepared, and the F-PNIPAM cube was then fully submerged for about 40 min, as shown in
Refractive index (RI) measurements were conducted to verify the separation efficiency. The RI for a feed mixture of 1:2 vol:vol ethanol:heptane is 1.3761, as shown in
F-PNIPAM with a desired volume was prepared by molding in cubical polydimethylsiloxane (PDMS) mold. Briefly, the PDMS mold was prepared by mixing the main component and the curing agent in 10:1 ratio by weight followed by degasification in vacuum oven to remove trapped air bubbles. The mixture was then poured in a cuboidal mold of 1.2 cm×1.2 cm base and heated at 60° C. for 6 hours for cross-linking. The PDMS mold replicated the shape of the mold with the dimensions mentioned above. Subsequently, 1 mL of the F-PNIPAM solution was poured in the PDMS mold and exposed to ultraviolet light (UV-A, λ=365 nm) for 15 minutes for photocuring. After photocuring, the cross-linked F-PNIPAM gel with 1.2 cm×1.2 cm×0.7 cm (about 1 cm3 volume) dimension was carefully removed from the mold.
All absorption experiments were performed using F-PNIPAM with 10 wt. % F-acrylate. The swelling ratio (S.R.) of F-PNIPAM was determined using Eqn. 6 from the weight of F-PNIPAM at time ‘t’ (W), during preparation (Wo) and the weight of polymer in F-PNIPAM (Ws, equivalent to weight of dried F-PNIPAM). Similarly, the equilibrium swelling ratio would indicate the swelling ratio of F-PNIPAM at its maximum swelling state. The equilibrium swelling ratio (S.R.eq) was obtained by submerging F-PNIPAM in the desired solvent for seven days.
Interestingly, it was found that F-PNIPAM can absorb a larger amount of alcohols with increasing number of hydrocarbons in alcohols, as shown in
If HSP values are not known, they can be estimated by using the group contribution method by Hoftyzer and Van Krevelen (Eqn. 8). the Hansen solubility parameters of PNIPAM were estimated as δD=19.15 √{square root over (MPa)}, δP=7.76 √{square root over (MPa)} and δH=7.04 √{square root over (MPa)}. The Hansen solubility parameters for F-acrylate from the group contribution method were also estimated. The estimated HSPs for F-acrylate are δD=14.87 √{square root over (MPa)}, δP=2.74 √{square root over (MPa)} and δH=3.97√{square root over (MPa)}.
Using the estimated Hansen solubility parameters, the χ values of NIPAM (χNIPAM) with various alcohols can be calculated using Eqn. 7. The χ values of F-acrylate (χF-acrylate) with various alcohols were also calculated. The χ values of F-PNIPAM (χF-PNIPAM) were then calculated by considering F-acrylate a factor of 0.1 (i.e. χF-PNIPAM=0.9 χNIPAM+0.1 χF-acrylate). These χ values for F-PNIPAM (χF-PNIPAM) for various alcohols are shown in
A hexadecane-in-water emulsion (30:70, vol:vol) was prepared using sodium dodecyl sulfate (SDS) as a surfactant. SDS was dissolved in water such that the concentration is 10 mg/mL. Hexadecane was added to the SDS dissolved water such that the volume ratio of water and hexadecane is 70:30 followed by vigorous stirring for emulsification. A cube of F-PNIPAM (1 cm3) was submerged into 2 mL of hexadecane-in-water emulsion, as shown in
A water-in-hexadecane emulsion (50:50, vol:vol) was prepared using span80 as a surfactant. Here, span80 was dissolved in hexadecane such that the concentration of span80 in hexadecane is 1 mg/mL. Water was added to this span80 dissolved hexadecane such that the ratio of water to hexadecane by volume is 50:50. The mixture was then vigorously stirred for 10 minutes to prepare the emulsion.
The capability of the F-PNIPAM to separate miscible liquid mixtures was also tested. First, a miscible liquid mixture that consists of ethanol (polar) and heptane (non-polar) is separated. Heptane and ethanol are miscible in all ranges of compositions. Here, the heptane-ethanol azeotrope (54.5 vol % heptane and 45.5 vol % ethanol) was used to eliminate the evaporation effect during separation process.
The separation of miscible methanol (MeOH) and methyl oleate (MO) was studied.
The F-PNIPAM was also used to separate a polar-polar liquid mixture consisting of dimethylformamide (DMF) and water. The χ value of the F-PNIPAM with DMF was determined to be 0.22. Since χDMF<χwater, (χwater=0.45), it is expected that the F-PNIPAM can absorb a larger amount of DMF than water.
To study the kinetics of absorption, the F-PNIPAM was submerged in the desired liquid and the weight change was recorded at intervals.
It was previously described that the F-PNIPAM can selectively absorb polar liquid (water) from a non-polar liquid (hexadecane, oil). Releasing the absorbed water from F-PNIPAM is critical to recover the water and to recycle the F-PNIPAM for further separation operation.
One of the simplest methods to release water from hydrogel is heat treatment. PNIPAM releases water at a temperature above its LCST, discussed further below. Although heat treatment is effective to release and recover water, it is highly energy-intensive. Mechanical compression has been utilized to squeeze water from hydrogel. However, this method can also be limited by damaging or sometimes disintegrating hydrogel. These challenges associated to the current thermal and mechanical treatments may be overcome by utilizing thermodynamic approaches. Two different techniques were tested to release water from F-PNIPAM. One is so-called co-nonsolvency and the other is osmosis.
Co-nonsolvency refers to a finding that hydrogel can release containing liquid when it is submerged in a solution of two or more liquids. For example, PNIPAM releases water when it is submerged in an ethanol-water mixture having a certain composition. A solution of ethanol and water (1:1) was used to test releasing water of the F-PNIPAM. To test the release of water of the F-PNIPAM, it was introduced to a water bath for 1 hour. The F-PNIPAM swelled and absorbed about 1,473 mg. Subsequently, the F-PNIPAM was transferred into a 15 mL of ethanol-water (1:1) solution bath. After 1 hour, the F-PNIPAM had released 1,234 mg of water. This value corresponds to about 83.8% of that water which was absorbed.
In another embodiment, osmosis (or osmotic pressure)-driven methods were used for releasing water from hydrogel. Here, a sodium chloride aqueous solution (NaCl, 300 mg/mL) was used to release water from F-PNIPAM. The F-PNIPAM containing 1,200 mg of water is submerged in NaCl solution for 1 hour. 870 mg of water was released, which corresponds to about 71.8% of that which was absorbed.
A combined approach—e.g., submerging the F-PNIPAM in a 1:1 ethanol:water solution containing NaCl—may result in an enhanced release. Therefore a test was conducted using 1:1 ethanol:water solution containing 30 mg/mL of NaCl. Surprisingly, it was observed that the F-PNIPAM lost about 93.3% of water in 1 hour, which indicates that almost all water is released. The table below summarizes the experimental data representing the releasing of the absorbed water from F-PNIPAM using different solutions.
For comparison, the same recovery tests of a neat PNIPAM were also conducted. The table below summarizes the results.
As discussed in greater detail above, the F-PNIPAM can also selectively absorb ethanol from a completely miscible mixture with a non-polar liquid (heptane). The same solutions discussed above were used to recover ethanol from the F-PNIPAM. The table below summarizes the results.
For comparison, the same recovery tests of a neat PNIPAM were also conducted, and the table below summarizes the results.
The recyclability of the F-PNIPAM was observed after releasing water by submerging it in a water bath for 1 hour and comparing the amount of absorbed water with that obtained using an as-prepared F-PNIPAM, as described above.
Due to the thermo-responsive behavior of NIPAM, the F-PNIPAM can release absorbed liquid (water) at a temperature above the LCST. It should be emphasized that the LCST for the F-PNIPAM was found to be about 28° C. This allows for water release at a mild heat treatment.
Salt ions may induce deswelling of NIPAM and consequently, the release of absorbed liquid. Anions contribute to the deswelling process. First, anions can polarize the water molecules that hydrogen bond to the amide groups. This results in the weakened hydrogen bond. In addition, anions disrupt the hydrophobic hydration of water molecules to the isopropyl groups.
Sodium chloride (NaCl) was found to effectively induce deswelling of the F-PNIPAM and consequently releasing the absorbed liquid.
It was also demonstrated that ethanol can be released using an aqueous NaCl solution.
Hydrophilic yet oleophobic materials have been used in separation of liquid mixtures consisting of polar (such as water) and non-polar (such as oil) phases. For example, hydrophilic/oleophobic membranes can selectively allow water to wet the surface and permeate through while repelling oil. Similarly, it has been demonstrated that the F-PNIPAM as described herein can be preferentially wet by water while repelling oil at temperatures below the LCST. Specifically, it was demonstrated that a water droplet can undercut the oil and consequently wet the surface. Such self-cleaning ability is critical to mitigate surface fouling.
By contrast,
According to another embodiment of the invention, an apparatus was developed for separating and recovering absorbed liquid from the F-PNIPAM. In order to achieve the continuous separation and simultaneous release of the absorbed liquid, the F-PNIPAM needs to contact a liquid mixture to selectively absorb one phase over the other while contacting the salt aqueous solution to release the absorbed liquid.
Referring now to
Thus has been described a new hydrogel, F-PNIPAM, and methods of making same, and apparatus for separating absorbed liquids from the hydrogel, which have superior qualities when compared to prior art hydrogels. While specific examples are provided herein in describing the invention, it shall be understood that the example are only for the purpose of describing the invention, and are not intended to be limiting. Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the spirit and scope of the present invention. Embodiments of the present invention have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to those skilled in the art that do not depart from its scope. A skilled artisan may develop alternative means of implementing the aforementioned improvements without departing from the scope of the present invention. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations.
This application claims priority to U.S. Provisional Patent Application No. 62/629,356 filed Feb. 12, 2018, the entirety of which is incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/US2019/017724 | 2/12/2019 | WO | 00 |
Number | Date | Country | |
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62629356 | Feb 2018 | US |