Electromagnetic Induction Pervaporation Membrane

Abstract

A pervaporation apparatus and method for liquid mixture separation are disclosed. The pervaporation disclosed utilizes an interfacial-heating membrane utilizing induction heating to provide temperature differences across the membrane for driving liquid mixture separation. The pervaporation system may include an electromagnetic induction heating device that is placed close to or encapsulated in a membrane module wherein one or more membranes with surfaces containing ferromagnetic or other induction-responsive materials. The membrane surface generates localized heat owing to the presence of a ferromagnetic composition that converts electric energy from an induction source to thermal energy. The ferromagnetic composition could include, without limitation, metals, metal alloys, composite materials, nanocomposite materials, nanoparticles, meshes, and combinations thereof.

Claims

1. A pervaporation system for liquid mixture separation, comprising: an interfacial-heating and separating dual functional composite membrane for simultaneously heating and separating a liquid mixture therethrough; and wherein the dual functional composite membrane generates a localized heat on a surface of the membrane when exposed to electromagnetic induction, and the heat generated on the surface enhances separation permeability.

2. The system of claim 1, wherein the interfacial-heating and separating dual functional composite membrane is a composite membrane that further includes: a top layer having a porous or non-porous interfacial-heating layer; a middle layer having a dense pervaporational separation layer; and a bottom layer having a porous support layer.

3. The system of claim 2, wherein the top layer contains an induction-responsive material or an induction-responsive material incorporated in a polymer membrane.

4. The system of claim 3, wherein the top layer when exposed to an electromagnetic field or an induction field generates heat by converting electric energy from an induction heating source to thermal energy.

5. The system of claim 4, wherein the electromagnetic field is amplified.

6. The system of claim 4, wherein the induction field is provided by a single induction heating source or multiple induction heating sources.

7. The system of claim 3, wherein the top layer is porous and has porosities ranging from 20%-90%, and has pore sizes between 0.05 μm to 5 μm.

8. The system of claim 3, wherein the top layer has a shape selected from a group consisting of a flat sheet, a cylinder, a cone, a rectangular, a sphere, an irregular shape, and any combinations thereof.

9. The system of claim 3, wherein the induction-responsive materials are selected from a group consisting of iron, metal, metal alloys and their oxides or compounds, Fe.sub.3O.sub.4 (Iron(II,III) oxide) nanoparticles, Fe.sub.2O.sub.3 (ferric oxide) nanoparticles, MXene (a ceramic of two dimensional inorganic compounds), ferromagnetic and conductive materials, and any combinations thereof.

10. The system of claim 3, wherein the polymer membrane is selected from a group consisting of poly(vinyl alcohol), chitosan, cellulose, polyaniline, polydimethylsiloxane, poly(ether amide), poly(l-trimethylsilyl-1-propyne), and any combination thereof.

11. The system of claim 3, wherein the induction-responsive materials are disposed in the polymer membrane through cross-linking, or coating, or blending, or grafting, or any combination thereof.

12. The system of claim 2, wherein the middle dense pervaporational separation layer is a material selected from a group consisting of poly(vinyl alcohol), chitosan, cellulose, polydimethylsiloxane, poly(ether amide), poly(l-trimethylsilyl-1-propyne), alumina, zeolites, metal-organic frameworks, and any combinations thereof.

13. The system of claim 2, wherein the bottom porous support layer is a material selected from a group consisting of polyvinylidene difluoride, polysulfones, polytetrafluoroethylene, poly(vinyl alcohol), chitosan, cellulose, polydimethylsiloxane, poly(ether amide), poly(l-trimethylsilyl-1-propyne), alumina, zeolites, and any combinations thereof.

14. The system of claim 2, wherein the porous membrane contains flat, tubular, or hollow fibers.

15. A pervaporation system for liquid mixture separation, comprising: a composite membrane separation module having an influent side, a permeate side, and a membrane, and wherein the membrane separation module contains an electromagnetic material; an induction heating device for heating the electromagnetic material in a localized area by inducing an electric current within the electromagnetic material; and wherein heat is generated on a surface of the composite membrane module to enhance solubility and diffusion of feed components to enhance permeability.

16. The system of claim 15, wherein the electromagnetic material is selected from a group consisting of iron, metal, metal alloys, Fe.sub.3O.sub.4 nanoparticles, Fe.sub.2O.sub.3 nanoparticles, MXene (a ceramic of two dimensional inorganic compounds), ferromagnetic and conductive materials, and any combinations thereof.

17. A method of using a pervaporation system for liquid mixture separation, comprising providing an interfacial-heating and separating dual functional composite membrane for simultaneously heating and separating a liquid mixture therethrough, the membrane having an induction-responsive material-coated interfacial-heating layer; exposing the induction-responsive material-coated interfacial-heating layer to an electromagnetic field or induction by an induction heating device at frequencies between about 0.1 kHz-500 kHz and power supply between about 0.1-10 KWh; pumping by a liquid circulating pump a feed liquid stored in a storage tank into an influent side of the membrane; heating the feed liquid in the influent side in the membrane by the induction heating device, resulting in a promoted driving force for pervaporation separation; and wherein the heating generates a localized heat on a surface of the membrane when exposed to the electromagnetic field or induction wherein the dual functional composite membrane, and the heat generated on the surface enhances separation permeability.

18. The method of claim 17, further includes: maintaining, in a permeate side in the membrane, a vacuum by a cascade of a cold trap and a vacuum pump; creating a temperature difference and a partial vapor pressure difference between the influent side and the permeate side to cause liquid components to pass through a dense layer of the membrane, wherein the dense layer is either a hydrophobic layer or a hydrophilic layer depending on hydrophobicity of a target separation component; concentrating the target separation component at the permeate side due to higher selectivity of the membrane towards the target separation component; and collecting the target separation component in the cold trap.

19. The method of claim 17, wherein the dual functional membrane is heated periodically or continuously.

20. The method of claim 18, wherein the cold trap is selected from a group consisting of a liquid nitrogen, a dry ice, a dry ice in acetone or a solvent with a boiling point between 40° C.-95° C., or any combination thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To assist those of skill in the art in making and using the disclosed pervaporation system and method and associated systems and methods, reference is made to the accompanying figures, wherein:

[0026] FIG. 1 is a schematic diagram of an electromagnetic induction pervaporation system, in accordance with one embodiment of the present disclosure;

[0027] FIG. 2 illustrates liquid mixture separation under induction heating; and,

[0028] FIGS. 3A and 3B are diagrams showing the structures of the interfacial-heating/separation dual functional pervaporation membranes in which the induction-responsive materials are blended into the selective layer of the membrane (FIG. 3A) or the induction-responsive materials are coated on the top of the selective layer of the membrane (FIG. 3B).

DETAILED DESCRIPTION

[0029] Adverting to the drawings, FIG. 1 is a schematic diagram of one embodiment of an electromagnetic induction pervaporation system comprising a membrane separation module 1 for the liquid mixture separation, an influent side 2, and a permeate side 3, an interfacial-heating/separation dual functional membrane 4 for separation, and an induction heating device 5. The pervaporation system could comprise a raw feed storage tank 6, a raw feed circulating pump 7, a liquid nitrogen cold trap 8, a permeate collecting tube 9, and a vacuum pump 10.

[0030] During a typical operation, the raw feed stored in the raw feed storage tank 6 is pumped into the influent side 2 of the membrane module 1 by the raw feed circulating pump 7. The raw feed in the influent side 2 in the membrane module 1 of the present invention contacts the locally heated membrane surface under an electromagnetic induction, resulting in the heating of interfacial liquid in the raw feed. Meanwhile, the permeate side 3 in the membrane module 1 in the present embodiment is maintained a high vacuum (4-5 kPa) by a cascade of the liquid nitrogen cold trap 8, the permeate collecting tube 9, and the vacuum pump 10. The purified components from the permeate side 3 is condensed in the liquid nitrogen cold trap 8 and collected periodically from the permeate collecting tube 9.

[0031] The temperature difference and vapor pressure difference between the influent side 2 and the permeate side 3 cause the liquid component to permeate through the functional membrane 4 in the present embodiment. The functional membrane 4 will be described in detail in FIG. 2.

[0032] FIG. 2 is a detailed illustration of one embodiment of a mass transfer process within the membrane module 1. In this embodiment, the membrane module 1 could comprise an interfacial-heating/separation dual functional composite membrane, which includes three different layers. The top layer is a porous or non-porous interfacial-heating layer 11, which is induction-responsive and can be heated under an electromagnetic field 16. Depending on the embodiment 16 may be one or more electromagnetic field (EMF) device(s) also known as induction heating source(s). These EMF devices, include but are not limited to thermoelectric devices, electrochemical cells, photodiodes, solar cells, electrical generators, transformers, and Van de Graaff generators. In addition, the EMF may be amplified using various devices, such as but not limited to magnetic amplifier (mag amp), transistor amplifier and the like. Magnetic amplifiers have largely been superseded by the transistor-based amplifier, except in a few critical, high-reliability or extremely demanding applications. Combinations of transistor and mag-amp techniques may still be used.

[0033] The middle layer of the membrane is a dense pervaporational separation layer 12, which has perm-selectivity for the feed stream at the influent side 15. The bottom layer is a porous support layer 13 providing mechanical support for the top two layers. The localized heating generated at the interfacial-heating layer 11 promotes the solubility and diffusion of the influent feed 15 in the separation layer 12 and converts to a vapor at the permeate side 14 where a vacuum is maintained. The vapor flows through the channel 14 and is then condensed and collected in the tube 9 shown in FIG. 1.

[0034] FIGS. 3A-3B are diagrams showing the structures of the interfacial-heating/separation dual functional pervaporation membranes in which the induction-responsive materials are either blended into the selective layer of the membrane (FIG. 3A) or the induction-responsive materials are coated on the top of the selective layer of the membrane (FIG. 3B). Depending on the embodiment, the induction responsive materials include, but are not limited to, a group consisting of iron, metal, metal alloys and their oxides or compounds, Fe.sub.3O.sub.4 (Iron(II,III) oxide) nanoparticles, Fe.sub.2O.sub.3 (ferric oxide) nanoparticles, MXene (a ceramic of two dimensional inorganic compounds), ferromagnetic and conductive materials, and any combinations thereof.

[0035] In the embodiment shown in FIG. 3A, the membrane module 1 could comprise an interfacial-heating/separation dual functional composite membrane, which includes two different layers. The top layer is a hybrid porous interfacial-heating and dense pervaporational separation layer, and the bottom layer is a porous support layer providing mechanical support for the top layer. Depending on the implementation, the top layer may have a porosity between about 20-90%. Porosity is defined in this disclosure as a void or void fraction. Porosity is a measure of the void (i.e., “empty”) spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. In addition, depending on the implementation, the top layer may include a shape selected from a group consisting of a flat sheet, a cylinder, a cone, a rectangular, a sphere, an irregular shape, and any combinations thereof.

[0036] The materials and the methods of the present disclosure used in examples will be described below. While the examples discuss the use of specific compounds and materials, it is understood that the present disclosure could employ other suitable compounds or materials. Similar quantities or measurements may be substituted without altering the method embodied below.

Example 1

[0037] First, Fe.sub.3O.sub.4 nanoparticles are synthesized by a modified chemical co-precipitation method. Briefly, 0.99 g FeCl.sub.2.4H.sub.2O and 2.7 g FeCl.sub.3.6H.sub.2O are dissolved in 100 ml deionized water in a 250 ml flask with mechanical stirring under nitrogen atmosphere at 80° C.

[0038] Then 10 mL NH.sub.3.H.sub.2O 25% (v %) is dropped at a speed of 1 drop per second into the above solution. The mixture is stirred continuously for 30 min. The obtained black Fe.sub.3O.sub.4 is washed with deionized water and ethanol under magnetic field and dried in the vacuum oven.

[0039] Subsequently, Polyvinyl alcohol (PVA) powder is first dissolved in deionized (DI) water at 90° C. for at least 6 h to obtain a 2 wt. % PVA casting solution. Then, a cross-linking agent of maleic acid (mole ratio of maleic acid:PVA=0.05:1) is added to the PVA solution and further stirred at 90° C. for 12 h. Subsequently, Fe.sub.3O.sub.4 nanoparticles is added into the PVA casting solution and stir vigorously to obtain a Fe.sub.3O.sub.4/PVA casting suspension.

[0040] The concentrations of PVA and Fe.sub.3O.sub.4 in the resultant casting solution are both around 5 wt. %, respectively.

[0041] Afterwards, the casting suspension is carefully cast on a polyethersulfone (PES) support layer by a casting knife at a casting gate height of 50 and then dried at room temperature overnight to obtain the hybrid Fe.sub.3O.sub.4/PVA dual functional membrane, whose structure is shown in FIG. 3A.

Example 2

[0042] First, Fe.sub.3O.sub.4 nanoparticles were synthesized according to EXAMPLE 1 herein. Then, a PVA/PES membrane was prepared using the following steps: first, a 2 wt. % PVA aqueous solution is prepared by vigorously stirring PVA (polyvinyl alcohol) power in DI (deionized) water at 90° C. for 6 h. Then, the PVA solution is crosslinked by adding a maleic acid (a mole ratio of maleic acid:PVA=0.05:1) for another 12 h at 90° C. Afterwards, the PVA solution is poured into a rectangular container and the PES (polyethersulfone) porous membrane is dipped onto the PVA solution for 5 min and then taken out for drying in room temperature. Four dip-coating cycles are performed, and the resultant PVA/PES pervaporation membrane is dried overnight at room temperature. At the last step, the dried PVA/PES membrane is further cured in an air dry oven at 120° C. for 1 h to ensure complete crosslinking between the maleic acid with the PVA chain.

[0043] Subsequently, an interfacial-heating layer is coated through phase inversion method on the PVA/PES membrane prepared above: first, a Fe.sub.3O.sub.4/PVA casting mixture is first prepared by dispersing Fe.sub.3O.sub.4 (iron (II,III) oxide) nanoparticles in Milli-Q water under mechanical agitation, which is then added into a crosslinking-treated PVA aqueous solution. The concentrations of PVA and Fe.sub.3O.sub.4 in the casting mixture are 5 wt. % and 25 wt. %, respectively. Then, the casting mixture is carefully cast on the PVA/PES membrane by a casting knife with a casting gate height of 250 μm. The resultant membrane is immediately immersed into an ethanol coagulation bath at room temperature. After complete solidification, the membrane is taken out and dried at room temperature to obtain the composite multi-layer Fe.sub.3O.sub.4/PVA dual functional membrane, whose structure is shown in FIG. 3B.

Example 3

[0044] In this example, the inventors assessed the desalination performance of interfacial-heating/separation dual functional composite membranes by utilizing the bench scale system shown in FIG. 1. In specific, the bench top pervaporation unit has a pervaporation membrane module with an effective membrane diameter of 35 mm and a separation area of approximately 10 cm.sup.2. The module housing was made from acrylic glass and was placed on a commercial induction heating station. The interracial-heating and separation dual functional membrane prepared in EXAMPLE 2 was sealed in the middle of the module. The feed solution of synthetic seater of 3.5 wt. % NaCl water was circulated through the feed channel of modules at a flow velocity of 5 cm.Math.min.sup.−1. At the permeate channel, vacuum (4-5 kPa) was maintained by a cascade of a liquid nitrogen cold trap and a vacuum pump. The inlet temperatures at the feed were constantly maintained at 20±0.5° C. throughout the entire experiment. The induction heating system was operated at a frequency of 162 kHz and power supply of 5 kW. Any experiment under given conditions was pre-run for around 3 hours after steady state was reached. Finally, the permeate was collected periodically at the cold trap to calculate the salt rejection and water flux. The salt rejection was measured to be 99.9%, and the water flux was measured to be 2 kg.Math.m.sup.−2.Math.h.sup.−1.

[0045] While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.