KR20140118748A - Fabricating method of polymetric composite nanofiber membrane adsorbent incorporated with manganese oxide particles for lithium recovery and polymetric composite nanofiber membrane fabricated by the method - Google Patents

Abstract

Disclosed in the present invention are a method for preparing a composite nanofiber lithium absorption film with immobilized manganese oxide absorbed powder which selectively absorbs lithium and a method for preparing a composite nanofiber film. The method for preparing a composite nanofiber lithium absorption film of the present invention comprises: a step for preparing a viscous solution by mixing lithium-manganese oxide absorbed powder and a high molecular material in a solvent; a step for preparing a composite nanofiber film by electrospinning the viscous solution; and a step for acid-treating the composite nanofiber film to give lithium absorption properties. Also, the method for preparing a composite nanofiber film of the present invention comprises: a step for preparing a viscous solution by mixing acid-treated lithium-manganese oxide absorbed powder and a high molecular material in a solvent; and a step for preparing a composite nanofiber film by electrospinning the viscous solution.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method for producing a composite nanofibrous lithium adsorption film having a manganese oxide-adsorbed powder immobilized thereon, and a composite nanofibrous lithium adsorbed film prepared thereby. THE METHOD}

The present invention relates to a method for producing a composite nanofiber lithium adsorbing film for recovering lithium and a method for recovering lithium using the composite nanofibrous lithium adsorbing film. More particularly, the present invention relates to a method for recovering lithium, A method for producing a polymer nanocomposite membrane, and a method for recovering lithium by selectively adsorbing lithium using the nanocomposite membrane.

Recently, the development of electric cars and the rapid increase in the demand for portable electronic appliances such as smart phones and tablet PCs are rapidly expanding the lithium secondary battery market, and the demand for lithium used in lithium batteries is also rapidly increasing. However, the reserves of lithium resources are concentrated in some Central and South American countries. Bolivia, Chile and Argentina account for 80% of the world's reserves. Therefore, it is necessary to develop new technologies that can secure lithium resources to replace limited land resources in these limited areas. Recently, researches are being made on the development of an adsorbent having excellent adsorption performance capable of recovering lithium from seawater, wastewater, and lithium concentrated wastewater in addition to lithium resources mined from the land.

In the prior art, the most commonly studied and superior performance adsorbent precursors include lithium-manganese oxide-based adsorbent powders, and their chemical structures include Li _1.33 Mn _1.67 O ₄ , LiMn ₂ O _4, and Li _1.6 Mn _1.6 O ₄ and so on. Of these, the oxide having the best adsorption performance to date is known as Li _1.6 Mn _1.6 O ₄ . However, these adsorbed powders are disadvantageously handled in recovering lithium in the form of powder having a diameter of several microns to several tens of microns.

In order to solve such problems, in Korean Patent Laid-Open Nos. 10-2005-0045792 and 10-2005-0045793, lithium-manganese oxide powder is formed into a honeycomb form by adopting ethylene vinyl acetate as a binder, or by using a urethane foaming agent, Thereby facilitating handling of the adsorbent. In addition, Korean Patent Nos. 10-0896053 and 10-2010-003656 facilitate the handling by filling lithium-manganese oxide in the floss fabric filter or filling it in a teabag-shaped polymer membrane filter. However, this method poses the risk of massive loss of powdery adsorbent when the filter is damaged by external forces.

Aya Umeno and his colleagues (Aya Umeno, "Preparation and adsorption properties of membrane-type adsorbents") have adopted a method in which PVC is dissolved in a solvent and manganese oxide is added to prepare a composite membrane. for lithium recovery from seawater ", Industrial Engneering Chemistry Research 41 (2002) 4281-4287). However, this method has a problem that PVC adsorbs lithium ions by blocking the lithium adsorption sites of manganese oxides.

Korean Patent Publication No. 10-2005-0045792 Korean Patent Publication No. 10-2005-0045793 Korea Patent No. 10-0896053 ≪ tb >

Aya Umeno, "Preparation and adsorptive properties of membrane-type adsorbents for lithium recovery from seawater ", Industrial Engneering Chemistry Research 41 (2002) 4281-4287

Disclosure of Invention Technical Problem [8] The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a method of manufacturing an adsorption membrane in which a manganese oxide selectively adsorbing lithium is fixed on a polymer nanofiber, The purpose is to provide.

In order to accomplish the above object, the present invention provides a method for preparing a composite nanofibrous lithium adsorption film, comprising: (1) preparing a viscous solution by mixing a lithium-manganese oxide adsorbing powder and a polymer material in a solvent; Electrospinning the viscous solution to produce a composite nanofiber film (step 2); And a step (step 3) of subjecting the composite nanofiber film to an acid treatment to impart a lithium adsorption capability.

The method for producing a composite nanofiber lithium adsorption film may further include a step of heat-treating the composite nanofiber film before the step 3, wherein the heat treatment is performed at a temperature below a melting point of the polymeric material at or above a glass transition temperature Range. ≪ / RTI >

The lithium-manganese oxide adsorbing powder may be any one of Li _1.6 Mn _1.6 O ₄ , Li _1.33 Mn _1.67 O ₄ , LiMnO ₂ and LiMn ₂ O ₄ , and preferably has an average diameter of 3 μm or less, desirable.

The lithium-manganese oxide adsorption powder is preferably added to the solvent in the range of 15 to 50 wt% based on the weight of the polymer material added to the solvent.

The polymer material may be any polymer selected from the group consisting of polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride, a copolymer thereof, or a mixture of one or more polymers It can be a polymer.

The polymer material may be added in an amount of 15 to 25% by weight based on the weight of the solvent, more preferably 18 to 25% by weight based on the weight of the solvent.

According to another aspect of the present invention, there is provided a method for preparing a composite nanofiber film, comprising: (1) preparing a viscous solution by mixing an acid-treated lithium-manganese oxide adsorbing powder and a polymer material in a solvent; And electrospinning the viscous solution to produce a composite nanofiber film (step 2).

The acid-treated lithium-manganese oxide adsorption powder may be any one of H _1.6 Mn _1.6 O ₄ , H _1.33 Mn _1.67 O ₄ , HMnO ₂ and HMn ₂ O ₄ , and the weight of the polymer substance added to the solvent By weight to 20% by weight to 60% by weight.

The polymer material may be any polymer selected from the group consisting of polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride, a copolymer thereof, or a mixture of one or more polymers It can be a polymer.

According to another aspect of the present invention, there is provided a method of recovering lithium from a composite nanofibrous lithium adsorption film produced by the method of manufacturing the composite nanofibrous lithium adsorption film or a composite nanofiber film produced by the method of manufacturing the composite nanofiber film, And recovering lithium from the recovered solution containing lithium.

The lithium recovery may be performed by immersing the composite nanofiber lithium adsorption film or the composite nanofiber film in the recovered solution.

The present invention constructed as described above is able to manufacture an adsorption membrane which is easy to handle and which minimizes the performance degradation of the adsorbed powder by fixing the lithium-manganese oxide adsorption powder to a nanofiber membrane having a high porosity with a large surface area per unit area There is an effect.

In addition, the composite nanofiber adsorption film and the composite nanofiber film of the present invention can be manufactured by a method in which the adsorbent fixed on the nanofiber and the contact with water, such as a polymer membrane, a foam or a ceramic membrane to which a conventional manganese oxide- It is easy to adsorb lithium.

Furthermore, since the composite nanofiber adsorption film and the composite nanofiber film of the present invention are porous films, it is possible to recover lithium by simply dipping them in a solution without consuming additional filtration pressure or energy during the lithium adsorption process.

1 is a scanning electron microscope (SEM) image of Li _1.6 Mn _1.6 O ₄ prepared in this example.
2 is a graph showing XRD (X-ray diffraction) analysis results of Li _1.6 Mn _1.6 O _4, H _1.6 Mn _1.6 O _4, and LiMnO ₂ produced in this example.
FIG. 3 is a photograph showing a composite nanofiber film manufactured according to an embodiment of the present invention and a nanofiber film to which a lithium-manganese oxide adsorbing material is not added.
4 is a photograph showing a composite nanofiber membrane prepared by electrospinning a viscous solution having a weight ratio of a polymeric substance of less than 15%.
5 is a scanning electron micrograph of the surface of a composite nanofiber membrane to which 15 wt% of Li _1.6 Mn _1.6 O ₄ adsorbed powder is added.
6 is a scanning electron microscope (SEM) image of the surface of a composite nanofiber membrane to which Li _1.6 Mn _1.6 O ₄ adsorbed powder is added in an amount of 50% by weight.
FIG. 7 is a transmission electron microscope (HR-TEM) photograph of a spherical aberration-corrected transmission electron microscope image of a composite nanofiber membrane to which Li _1.6 Mn _1.6 O ₄ adsorbing powder is added in an amount of 50% by weight.
8 is an electron micrograph of the composite nanofiber film before heat treatment (left) and after heat treatment (right).
Fig. 9 is an SEM photograph of a composite nanofiber membrane that is not subjected to heat treatment.
10 is a scanning electron microphotograph of a composite nanofiber membrane thermally treated at 170 ° C.
11 is a scanning electron microscope photograph of a composite nanofiber film heat-treated at 180 ° C.
12 is a scanning electron micrograph of a composite nanofiber membrane heat-treated at 190 ° C.
13 is a scanning electron microphotograph of a composite nanofiber film heat-treated at 200 ° C.
FIG. 14 is a graph showing the lithium adsorption capacity of each of the composite nanofiber adsorption membranes prepared by acid treatment of the composite nanofiber membranes heat-treated under different temperature conditions under the same conditions.
FIG. 15 is a graph showing the selectivity evaluation of a composite nanofiber adsorbing film and H _1.6 Mn _1.6 O ₄ powder for metal ions including lithium ions. FIG.
16 is a scanning electron microphotograph of a composite nanofiber membrane to which 20 wt% H _1.6 Mn _1.6 O ₄ adsorbing powder is added.
17 is an SEM photograph of a composite nanofiber membrane to which 40 wt% H _1.6 Mn _1.6 O ₄ adsorbing powder is added.
18 is a scanning electron micrograph of a composite nanofiber membrane to which 40 wt% of H _1.6 Mn _1.6 O ₄ adsorbing powder is added.
19 is a scanning micrograph of a pure polyacrylonitrile nanofiber membrane.
FIG. 20 is a graph showing a linear model of equilibrium lithium adsorption of each of the composite nanofiber lithium adsorption membranes prepared by different H _1.6 Mn _1.6 O ₄ contents. FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, embodiments of the present invention will be described in detail.

Preparation of lithium-manganese oxide adsorption powder

One embodiment of the present invention is a lithium manganese oxide (LiMnO ₂ , average diameter: <1 μm,> 99% trace metals basis) manufactured by Sigma-Aldrich as a reactant for forming a lithium- Were used. Lithium manganese oxide is heat-treated under Li _1.6 Mn _1.6 O and used as a reactant to obtain the _4, Li _1.6 Mn _1.6 O ₄ atmosphere (air) at a temperature of 400 ~ 600 ℃ the LiMnO ₂ to synthesize the atmosphere.

In a study by Ramesh Chitrakar et al., LiMnO ₂ produced by hydrothermal reaction of γ-MnOOH and LiOH at 120 ° C. for one hour was heat-treated at 400 to 600 ° C. for 4 hours under air condition to obtain Li _1.6 Mn _1.6 O ₄ product. In the above study, when LiMnO ₂ was heat-treated at 450 ° C, it was confirmed that the lithium adsorption performance of the adsorbed powder was the most excellent.

In one embodiment of the present invention, Li _1.6 Mn _1.6 O ₄ adsorbent powder was prepared by heat treatment at 450 ° C. for 4 hours under air conditions according to the above-mentioned research paper. Li _1.6 Mn _1.6 O ₄ powder was used as the lithium-manganese oxide adsorbing powder for the preparation of the composite nanofibrous lithium adsorption film. However, the Li _1.6 Mn _1.6 O ₄ powder is not limited to Li _1.6 Mn _1.6 O ₄ , Li _1.33 Mn _1.67 O ₄ , LiMnO _2, LiMn ₂ O _{4 ,} or the like.

FIG. 1 is an electron microscope (SEM) image of the Li _1.6 Mn _1.6 O ₄ adsorption powder, and FIG. 2 is an XRD analysis result of Li _1.6 Mn _1.6 O ₄ adsorbing powder.

The lithium-manganese oxide adsorbent powder used in the production of the polymer composite nano-fiber adsorbent preferably has an average diameter of 3 m or less and more preferably 1 m or less in average diameter as the lithium-manganese oxide adsorbent powder. When the diameter of the powder exceeds 3 탆, the mechanical properties of the nanofiber are lowered, and the powder is easily separated from the nanofibers during the recovery of lithium. Referring to FIG. 1, the Li _1.6 Mn _1.6 O ₄ adsorbent powder of one embodiment of the present invention has an average diameter of 1 μm or less.

Fabrication of composite nanofiber membranes

One embodiment of the present invention is a method for producing a composite nanofiber film, which comprises the steps of mixing polysulfone (Solvay solexsis, Udel P-3500) as a polymer material, N, N-dimethylformamide and tetrahydrofuran as a solvent : 1 in volume ratio was used.

An embodiment of the present invention uses polysulfone as a polymer material. The polysulfone is most widely used for manufacturing membranes, has a low cost of polymers, is excellent in chemical resistance and durability, and is suitable for manufacturing composite nanofiber membranes . However, the present invention is not limited thereto, and it is possible to use a polyethersulfone, a polyacrylonitrile, a polyvinylidene fluoride, a cellulose acetate and a polyvinyl chloride ), A copolymer thereof, or a polymer in which one or more polymers are mixed, may be suitably modified. In addition, the present invention is not limited to the polymers listed above, and can be applied as a material for manufacturing the composite nanofibers adsorption film of the present invention if it is a polymer material capable of electrospinning.

In the present invention, the polymer material serves as a binder of lithium-manganese oxide adsorbing powder, and a lithium-manganese oxide adsorption powder is added into a composite nanofiber film prepared by electrospinning a viscous solution containing lithium- By fixing the powder, the handling of the lithium-manganese oxide-adsorbed powder is facilitated.

In an embodiment of the present invention, a mixed solvent obtained by mixing N, N-dimethylformamide and tetrahydrofuran as a solvent is used, but the present invention is not limited thereto, N-dimethylformamide, tetrahydrofuran, N, N-dimethylacetamide and N-methyl-2-pyrrolidone, or a mixture thereof As shown in Fig.

The composite nanofiber membrane according to one embodiment of the present invention is obtained by dissolving the polysulfone in the mixed solvent at a weight ratio of 18:82, adding 15% by weight of Li _1.6 Mn _1.6 O ₄ adsorbed powder based on the polysulfone weight, To prepare a viscous solution, which was prepared by electrospinning the viscous solution. In the electrospinning process, a nozzle having a nozzle size (OD) of 0.51 mm was used. The distance between the nozzle and the drum winding machine was 120 mm, and the polymer solution was discharged at a discharge speed of 4 m / h at a supply voltage of 20 kV. The composite nanofibers were dried in a vacuum oven at 70 DEG C for at least 12 hours in order to completely remove the remaining solvent.

However, the present invention is not limited thereto. The composite nanofibrous membrane may be prepared by adding a lithium-manganese oxide adsorption powder to a solvent in a desired ratio and allowing the adsorbed powder to be dispersed in a solvent by applying ultrasonic waves. The desired high molecular weight material is then adsorbed onto lithium- And the mixture was stirred at room temperature for more than 500 rpm until the polymer material was completely dissolved in the solvent to prepare a viscous solution. An appropriate amount of the prepared viscous solution was added to the syringe, and the mixture was stirred at a constant speed using a syringe pump The solution is supplied to the nozzle, and a high voltage is supplied to the nozzle portion, thereby producing a composite nanofiber film. Particularly, when the electrostatic repulsion supplied from the surface tension of the viscous solution is larger than that of the viscous solution, nanofibers are formed and are wound on the aluminum foil in a film form.

3 is a photograph showing a composite nanofiber film (right side) prepared according to an embodiment of the present invention and a nanofiber film (left side) to which no lithium-manganese oxide adsorbing material is added.

In particular, the left image is Li _1.6 Mn _1.6 O ₄ powder is a non-addition of nanofiber membrane picture shows a bright white, Li _1.6 Mn _1.6 O ₄ are shown in gray as shown in the adsorbed powder is added to the composite nano-fiber membranes at right .

The content of the polymer material for performing the electrospinning process is not limited to a specific one, but the solution is prepared in a weight ratio suitable for the kind of the solvent and the kind of the solvent. However, in preparing the viscous solution for producing nanofibers, the content of the polymeric material relative to the solvent is preferably 15 to 25% by weight.

4 is a photograph of a composite nanofiber membrane prepared by electrospinning a viscous solution having a weight ratio of a polymeric material of less than 15%. As shown, the viscosity of the viscous solution is too low to observe a bead-like structure, and this type of nanofiber has a problem of impairing the porosity and surface area of the nanofiber.

 More preferably, when the viscous solution having a content of the polymer substance relative to the solvent is 18 to 25% by weight, the spherical fiber is not observed, the nanofiber form is well formed and the appropriate mechanical strength Respectively.

Generally, nanofibers electrospun are advantageous in maximizing the surface area of the nanofibers as the diameter of the nanofibers is smaller. However, if the diameter of the nanofibers is too small, the mechanical strength of the nanofibers deteriorates. Therefore, the diameter of the nanofibers is preferably in the range of 200 to 2000 nm.

The diameter or the shape of the nanofibers is affected by the viscosity of the viscous solution, but also by the electrospinning conditions. For example, increasing the velocity of the viscous solution increases the diameter of the nanofiber, and conversely, increasing the distance between the spinning nozzle and the sample winding drum or increasing the electrical conductivity of the viscous solution decreases the diameter of the nanofiber . Therefore, optimization of the spinning conditions is also important to produce nanofibers in the diameter range desired to be obtained from the electrospinning of the viscous solution.

In preparing the viscous solution for producing the nanofibers, the content of the lithium-manganese oxide adsorbing powder is preferably 15 to 50 wt% based on the polymer material used for producing the viscous solution.

In the method for producing a composite nanofiber film according to an embodiment of the present invention, the Li _1.6 Mn _1.6 O ₄ adsorbing powder is added in an amount of 15 to 50 wt% based on the weight of the polymer material used for preparing the viscous solution The properties of the composite nanofiber membranes are shown in Table 1 below. &Lt; tb &gt;&lt; TABLE &gt;

Li _1.6 Mn _1.6 O ₄ Adsorbed powder content (wt%) Composite nanofiber membrane Film thickness (mm) Average pore size (탆) Average Diameter Size (mm) 15 0.190 1.750 800 ± 352 20 0.160 2.362 842 ± 363 25 0.178 2.508 - 30 0.164 2.325 994 ± 357 35 0.180 2.487 - 40 0.141 2.649 1045 ± 405 50 0.180 2.256 1182 ± 539

In Table 1, the composite nanofiber film thickness was measured with a digital micrometer and the average pore distribution was measured with a capillary flow porometer (CFP-1200AE, Porous Materials, Inc., USA). The Li _1.6 Mn _1.6 O ₄ adsorbed powder content The average diameter size of the composite nanofibrous film gradually increased from 15 wt% to 50 wt%, but it was found to be 2 탆 or less.

Figure 5 Li _1.6 Mn _1.6 O ₄ adsorbed powder is a scanning micrograph of the composite nano-fiber membrane surface was added 15% by weight, and Figure 6 is Li _1.6 Mn _1.6 O ₄ adsorbed powder is a hybrid nanofiber membrane surface was added 50% by weight &Lt; / RTI &gt; Referring to FIGS. 5 and 6, it can be seen that the composite nanofiber film is formed even when the Li _1.6 Mn _1.6 O ₄ adsorption powder is increased from 15 wt% to 50 wt%.

And Figure 7 is Li _1.6 Mn _1.6 O ₄ adsorbed powder is 50% of the composite nano-fiber membrane of spherical aberration corrected transmission electron microscopy (HR-TEM) was added by weight of pictures, well fixed Li _1.6 Mn _1.6 O ₄ adsorbing powder into hybrid nanofiber .

Mechanical properties of composite nanofiber membranes through heat treatment

The composite nanofiber membrane produced by the above method has an advantage that it has a very large surface area per unit area, but on the contrary, it has a disadvantage that mechanical strength is low because of large porosity. In order to overcome such disadvantages, the composite nanofiber film is thermally treated to induce physical binding (bonding) between the nanofibers, whereby a composite nanofiber film having excellent strength can be obtained.

First, the composite nanofiber film prepared by the above method was heat-treated at 190 ° C for 90 minutes, and mechanical properties were tested. The mechanical properties were measured using a universal testing machine (UTM, LF-plus) manufactured by LLoyd, UK. The gage length was measured at 20 mm and the crosshead speed was measured at 5 mm / min.

 FIG. 8 is an electron micrograph of the composite nanofiber film before the heat treatment (left) and after the heat treatment by the above method (right). As shown in FIG. 8, it was confirmed that physical bonding occurred between the nanofibers by heat treatment as shown in FIG.

When the composite nanofibrous film is heat treated to enhance the mechanical properties, the temperature and time conditions of the heat treatment are very important factors. When the heat treatment is performed at a too high temperature or for a long time, the nanofiber shrinks, and in particular, the Li adsorption site of Li _1.6 Mn _1.6 O _{4 in} the nanofiber is clogged due to polymer shrinkage, It is important.

In order to maximize the mechanical strength while minimizing the shrinkage of the composite nanofiber and to find the optimal conditions for minimizing the deterioration of the lithium adsorption efficiency due to the heat treatment, the heat treatment was performed under different temperature conditions and the heat treatment time was comparatively experimented , More specifically, the composite nanofibrous film prepared by the above method on the basis of the glass transition temperature (T _g : 185 ° C) of the polysulfone and the melting point (T _m : 190 to 195 ° C) ℃ and 200 ℃ for 90 minutes. In order to prevent sudden shrinkage of the sample due to high temperature, the upper part of the nanofiber membrane was sandwiched with a Teflon plate.

FIG. 9 is a scanning electron micrograph of a composite nanofiber membrane that is not subjected to heat treatment, and FIGS. 10 to 13 are scanning electron micrographs of a composite nanofiber membrane heat-treated at 170 ° C., 180 ° C., 190 ° C., and 200 ° C., respectively.

9 to 11, the composite nanofiber membranes subjected to the heat treatments at 170 ° C. and 180 ° C., which are lower than the glass transition temperature of the polysulfone, are different from the composite nanofiber membranes in which the heat treatment is not performed, Almost nothing can be seen.

Referring to FIG. 12, it can be seen that the composite nanofibers obtained by performing heat treatment at 190 ° C. within the melting point range of the polysulfone showed a change in the morphology of the nanofibers but were not significantly deformed.

Referring to FIG. 13, it can be seen that the composite nanofibers obtained by heat treatment at 200 ° C higher than the melting point of polysulfone are hardly found in the form of nanofibers, and the melted nanofibers are bonded to each other to form a large branch shape .

The results of measuring the mechanical strength of the composite nanofiber film according to the heat treatment temperature are shown in Table 2 below.

Heat treatment temperature Film thickness The tensile strength Elongation Average pore size - 0.196mm 1.56 MPa 11.55% 1.78 탆 170 ℃ 0.220 mm 3.65 MPa 26.31% 1.86 탆 180 DEG C 0.207mm 6.04 MPa 74.82% 1.66 탆 190 ℃ 0.199mm 6.66 MPa 81.11% 1.75 탆 200 ℃ 0.086mm 14.66 MPa 15.79% 3.16 탆

The thickness of the heat treated composite nanofiber membrane was measured using a micrometer, and the tensile strength and elongation were measured using a tensile strength tester. The average pore size was measured using a PMI (Capillary Flow Porometer) manufactured by Porous Materials, USA.

Referring to Table 2, the thickness of the composite nanofibrous film was not significantly changed compared to the sample that was heat-treated at 190 ° C and the sample that was not heat-treated, and it was confirmed that the thickness of the film decreased by almost 50% there was. Also, the average pore size increased sharply in the heat treated samples at 200 ℃. On the other hand, it was confirmed that the tensile strength increased with the heat treatment under the high temperature condition. The elongation of the film increased as the temperature of the sample was increased. However, the elongation of the film increased sharply in the samples annealed at 200 ℃, which is higher than the melting point of polysulfone.

Therefore, it is preferable that the heat treatment for reinforcing the mechanical properties of the composite nanofiber membrane using polysulfone is performed at a temperature range of 185 to 195 ° C, which is a temperature range from the glass transition temperature to the melting point of the polysulfone. However, the present invention is not limited to this, and in the case where another polymer material is used in the production of the composite nanofiber film, it is preferable to heat-treat the polymer material in a temperature range from the glass transition temperature to the melting point.

Acid treatment of composite nanofiber membranes to produce complex nanofiber lithium adsorption membranes

In order to recover lithium from seawater and concentrated water of a brine or seawater desalination plant, the lithium-manganese adsorption powder fixed on the composite nanofiber membrane should be subjected to an acid treatment to form a composite nanofiber lithium adsorption membrane. When an acid aqueous solution is added to the composite nanofiber membrane, lithium can be replaced with hydrogen to become a manganese oxide and adsorb lithium.

In one embodiment of the present invention, 0.5 M dilute acid was used as an acid treatment solution for the preparation of the composite nanofibrous lithium adsorption membrane, and each composite nanofiber membrane heat-treated at different temperatures (170-200 ° C) , And then reacted in an incubator at a stirring speed of 200 rpm or more for 24 hours to prepare composite nanofiber lithium adsorption membranes.

Evaluation of Lithium Adsorption Capacity of Composite Nanofiber Lithium Adsorption Membrane by Annealing Temperature

Each of the composite nanofiber lithium adsorbing membranes prepared by the above method was washed several times with tertiary distilled water, and the water was removed and immersed in a solution of 1 mM LiOH (pH 11, 150 mL) to conduct lithium adsorption experiments. The lithium adsorption experiments were carried out in an incubator at a shaking speed of 200 rpm under a temperature condition of 30 ° C. for 24 hours. The solution was sampled and extracted using an inductively coupled plasma mass spectrometer (ICP-MS) The amount of lithium was measured and calculated.

FIG. 14 is a graph showing the lithium adsorption capacity of a composite nanofibrous lithium adsorption film prepared by acid-treating each composite nanofiber film heat-treated under different temperature conditions under the same conditions.

14, the pure lithium-free powder (HMO) containing no polymer was highest by adsorbing 11.4 mg of lithium per weight (g), and the composite nanofiber lithium adsorbed film heat- The lithium adsorption capacity was the highest at 8.0 mg per g of the adsorbed powder contained, which was 70% of the lithium adsorption capacity of the pure lithium adsorption powder. Also, the composite nanofiber lithium adsorption membrane heat treated at 200 ℃ showed the lowest lithium adsorption capacity of 6.3mg per weight (g) of the adsorbed powder contained in the composite nanofiber and 52.8% of the adsorption capacity of pure lithium adsorption powder.

The specific surface area of the composite nanofiber lithium adsorbing film, lithium-manganese oxide adsorbing powder and acid-treated lithium-manganese oxide adsorbing powder was measured using a specific surface area meter (BET).

Sample Annealing Temperature (° C) Surface area (m ² / g) Pore size (nm) Li _1.6 Mn _1.6 O ₄ - 11.09 8.22 H _1.6 Mn _1.6 O ₄ - 39.16 6.68 PSf / Li _1.6 Mn _1.6 O ₄ - 3.24 4.33 PSf / Li _1.6 Mn _1.6 O ₄ 180 3.48 2.86 PSf / Li _1.6 Mn _1.6 O ₄ 190 3.75 3.17 PSf / Li _1.6 Mn _1.6 O ₄ 200 2.64 -

Referring to Table 3, it can be seen that the specific surface area of the composite nanofiber lithium adsorption film is in agreement with the tendency of lithium adsorption capability. Particularly, the surface area of the acid-treated lithium-manganese oxide adsorbent powder not including the polymer was the highest at 39.16 m ² / g, and the composite nanofibrous lithium adsorbent had the highest value at the heat treatment temperature of 190 ° C., The lowest specific surface area was obtained when the temperature was 200 ° C.

The composite nanofibers prepared by using the polysulfone from the lithium adsorption capacity (FIG. 14), mechanical properties (Table 2) and specific surface area analysis results (Table 3) were found to be optimum when annealed at 185 ° C. to 195 ° C., , And it can be seen that the lithium adsorption capacity is improved by the heat treatment. However, when the high molecular weight material was melted at a high temperature of 195 ° C or higher and the nanofibers were deformed in structure, the lithium absorption capacity was deteriorated. However, the present invention is not limited thereto, and the optimal heat treatment temperature range may vary depending on the polymer material used in the production of the composite nanofiber film.

Evaluation of Lithium Adsorption Capacity of Composite Nanofiber Lithium Adsorption Membrane by Content of Lithium-Manganese Oxidation Powder

The content of Li _1.6 Mn _1.6 O ₄ adsorbed powder was varied from 15 to 50% by weight based on the weight of the polysulfone used in the preparation of the viscous solution to prepare each of the composite nanofiber membranes, , And the heat treated composite nanofibers were immersed in dilute acid at a temperature of 30 ° C and reacted in an incubator at a stirring speed of 200 rpm or more for 24 hours to prepare composite nanofiber lithium adsorption membranes.

Each of the composite nanofibrous lithium adsorption membranes prepared by the above method was washed several times with tertiary distilled water, and then the water was removed and immersed in a solution of 1 mM LiOH (pH 11, 150 mL) to conduct lithium adsorption experiments. rpm agitation speed (shaking speed) in an incubator for 24 hours under a temperature condition of 30 ° C. The solution was sampled and the amount of lithium extracted using an inductively coupled plasma mass spectrometer (ICP-MS) was measured Are shown in Table 4 below.

Li _1.6 Mn _1.6 O ₄ content (wt%) Lithium adsorption capacity (mg Li / g Li _1.6 Mn _1.6 O ₄ ) Tensile Strength (MPa) Elongation (%) 15% 8.03 7.00 80.11 20% 8.34 7.57 87.22 25% 9.00 6.54 103.70 30% 9.00 6.21 76.59 35% 9.41 5.85 74.13 40% 10.69 5.75 48.77 50% 10.72 4.90 43.23 Li _1.6 Mn _1.6 O ₄ powder 11.43 - -

Referring to Table 4, it can be seen that as the Li _1.6 Mn _1.6 O ₄ adsorptive powder content increases, the lithium adsorption capacity increases substantially proportionally. In particular, when the loading of Li _1.6 Mn _1.6 O ₄ powder was 50%, the lithium adsorption capacity was 10.72 mg, which was approximately 93% as compared with the lithium adsorption capacity of the pure Li _1.6 Mn _1.6 O ₄ adsorption powder . This is because as the loading of Li _1.6 Mn _1.6 O ₄ powder increases, the influence of the polymer material is less and the reduction of the lithium adsorption capacity is less.

On the other hand, as the loading of Li _1.6 Mn _1.6 O ₄ powder increased, the tensile strength and elongation of the composite nanofiber film gradually decreased, but still showed competitive mechanical properties.

Selectivity Evaluation of Lithium Ion by Composite Nanofiber Lithium Adsorption Membrane in the Presence of Other Metal Ions

Representative cations competing with each other of lithium (Li) ions adsorbed by the composite nanofibrous lithium adsorption film of the present invention include monovalent ions of potassium (K) and sodium (Na) ions, magnesium (Mg) Ca) ion, and the like. These cations are in competition with lithium ions and can degrade the selectivity of lithium ions during the adsorption process.

Therefore, a metal ion solution was prepared to evaluate the selectivity of lithium ions by the composite nanofibrous lithium adsorption film of the present invention, as shown in Table 5 below.

No. Li solutions Metal ion Metal ion conc. pH ① LiOH solution Li ⁺ 1 mM 11 ② LiOH with other metal ions solution Li ⁺ , K ⁺ , Na ⁺ , Ca2 ⁺ , Mg2 ⁺ 1 mM 11 ③ LiCl buffer solution Li ⁺ 10 mM 9.75 ④ LiCl with other metal ions buffer solution Li ⁺ , K ⁺ , Na ⁺ , Ca2 ⁺ , Mg2 ⁺ 10 mM 9.75

Referring to Table 5, a 1 mM LiOH (pH 11) metal ion solution (①) was prepared, and a metal ion solution (②) was prepared by adding 1 mM Na, K, Mg and Ca ions to the solution . In addition, a buffer solution (NH ₃ -NH ₄ Cl, pH 9.75) was prepared in order to minimize the influence of the pH of the solution during the lithium adsorption experiment, and LiCl (≥98%, Fluka) (3) was prepared. To the solution (3), Na, K, Mg and Ca ions were added at a concentration of 10 mM, respectively, to prepare a metal ion solution (4).

The composite nanofiber adsorption membrane for evaluating the selectivity of lithium ions was prepared by preparing a viscous solution by adding 38.3 wt% of Li _1.6 Mn _1.6 O ₄ adsorbed powder based on polysulfone content and then spinning the composite nanofiber membrane prepared by electrospinning at 190 ° C And then subjected to an acid treatment after the heat treatment. For comparison, H _1.6 Mn _1.6 O ₄ adsorbing powder of the same amount (130 to 134 mg) as the Li _1.6 Mn _1.6 O ₄ adsorption powder contained in the composite nanofibers adsorption membrane was used Respectively.

In the evaluation test of lithium ion selectivity, the composite nanofiber adsorbed film and the H _1.6 Mn _1.6 O ₄ powder were respectively immersed in the metal ion solution (300 mL) of (1) and (2) and the metal ion solution (150 mL) of The reaction was carried out for 24 hours in an incubator at a stirring rate of 200 rpm under a temperature condition of 30 ° C., and adsorption experiments were carried out. Two samples were prepared for reliability of the experimental results and the results were averaged and shown in Table 6 below.

No. Li solutions
Lithium adsorption capacity (mg Li / g Li _1.6 Mn _1.6 O ₄ ) H _1.6 Mn _1.6 O ₄ adsorption powder Composite nanofiber adsorption membrane ① LiOH solution 11.43 10.72 ② LiOH with other metal ions solution 10.99 10.44 ③ LiCl buffer solution 21.03 19.90 ④ LiCl with other metal ions buffer solution 20.53 19.61

As shown in Table 6, the adsorption capacity of H _1.6 Mn _1.6 O _{4 as a} whole is slightly higher than that of the composite nanofiber adsorption membrane, and metal ions other than lithium ions (K ⁺ , Na ⁺ , Mg ²⁺ , Ca ²⁺ ), the adsorption capacity for lithium was reduced by about 3 to 4%. Further, the recovered amount of the lithium ions in the metal ion solution of ③ is eotneunde represent nearly twice the recovery of lithium ion in the metal ion solution of ① to each 21.03mg and 19.90mg, which are H ⁺ / Li ⁺ ions Because they are not affected by the decrease in pH when exchanged.

However, as a whole, the lithium adsorption capacity of the composite nanofiber adsorptive membrane is reduced to only 6% or less as compared with the lithium adsorption capacity of the H _1.6 Mn _1.6 O ₄ adsorbent powder.

15 is a graph showing the selectivity evaluation of metal ion containing lithium ions in the composite nanofiber adsorbing film and the H _1.6 Mn _1.6 O ₄ adsorbing powder.

15, the selectivity of metal ions by H _1.6 Mn _1.6 O ₄ adsorbing powder was higher in the order of Li >>Na>Mg>Ca> K, and Li >>Mg>Na>Ca> K, and the selectivity for lithium ion among the metal ions is very high.

Fabrication of Composite Nanofiber Membrane Using Acid-Treated Lithium-Manganese Oxides and Evaluation of Physical Properties

In order to produce a composite nanofiber membrane according to another embodiment of the present invention, H _1.6 Mn _1.6 O ₄ acid-treated Li _1.6 Mn _1.6 O ₄ adsorbed powder as an adsorbent powder and polyacrylonitrile as a polymer material were used.

20, 40, and 60 wt% of H _1.6 Mn _1.6 O ₄ adsorbed powder, respectively, were added to the solvent of dimethylformamide based on the weight of the polyacrylonitrile to be added to the solvent, followed by stirring at 60 ° C for 2 hours to disperse the poly Acrylonitrile was added and dissolved for 4 hours and further reacted at room temperature for further 4 hours to prepare a viscous solution.

The polyacrylonitrile is preferably added in a weight ratio of 1: 9 based on the solvent. However, the weight ratio of the polyacrylonitrile to the solvent may be varied depending on the kind of the polymer added to the solvent.

15 mL of the viscous solution was taken in a polypropylene syringe (20 mL), and a needle having an inner diameter of 0.51 mm was connected thereto. The needle was attached to a syringe pump (KD Scientific 750, South Korea), and viscous solution was applied at a constant flow rate of 4 mL / (PAN / H _1.6 Mn _1.6 O ₄ ) was prepared by an electrospinning apparatus (Model: ESP200D / ESP100D, NanoNC Co., Ltd., South Korea).

In particular, a voltage of 22-25 V was applied for electrospinning. The distance between the needle and the drum winding was fixed at 100 mm, and the winding machine was rotated at a constant speed of 500 rpm to collect the nanofibers in a film form on the aluminum foil And then placed in a vacuum oven at a temperature of 60 DEG C for one day and dried for removing the remaining solvent.

16 to 18 are scanning electron micrographs of a composite nanofiber membrane to which H _1.6 Mn _1.6 O ₄ adsorbing powders of 20, 40 and 60 wt%, respectively, are added based on the weight of the polyacrylonitrile.

16 to 18, it can be seen that the nanofibers of the composite nanofibers are well formed without the formation of beads. In addition, when 20 wt.% Of H _1.6 Mn _1.6 O ₄ was added (FIG. 16), H _1.6 Mn _1.6 O ₄ particles evenly dispersed in the nanofibers and H _1.6 Mn _1.6 O ₄ particles clearly visible on the surface of the nanofibers when almost were not be found, is added when 40% of the H _1.6 Mn _1.6 O ₄ by weight of the addition (17), and 60% of H _1.6 Mn _1.6 O ₄ by weight (Fig. 18) is H _1.6 Mn _1.6 O ₄ It can be seen that large H _1.6 Mn _1.6 O ₄ particles can be observed easily as the particles come out from each other and protrude out of the nanofiber.

In particular, the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄ ) has an average diameter of 200 to 300 μm, and the composite nanofiber membrane (PSf / Li _1.6 Mn _1.6 O ₄ ), which is an embodiment of the present invention, It is possible to manufacture a composite nanofiber membrane having a much smaller diameter.

Further, in order to prepare a pure polyacrylonitrile nanofiber membrane for comparison with the composite nanofiber membrane, 10% by weight based on the weight of the dimethylformamide solvent was added to the dimethylformamide solvent to prepare a viscous solution. Were prepared in the same manner as the composite nanofibers.

FIG. 19 is a scanning electron microscope photograph of a pure polyacrylonitrile nanofiber membrane. It can be seen that the nanofibers are well formed without the formation of a bead like the composite nanofiber membrane.

Generally, nanofibers formed with beads weaken the linkage of the polymer. Therefore, such a structure may irregularly form the nanofiber diameter and may interfere with the dispersion of the H _1.6 Mn _1.6 O ₄ particles, or the polyacrylonite around the adsorbed particles It is inappropriate to increase the thickness of the reel binder.

Generally, when the thickness of the binder which serves to fix the adsorbent is increased, the adsorption ability of the composite nanofiber membrane can be remarkably reduced as compared with pure H _1.6 Mn _1.6 O ₄ particles not containing a binder.

Likewise, despite the existence of H _1.6 Mn _1.6 O ₄ particles in the viscous solution, it was possible to produce composite nanofiber membranes without bead shape because of the continuous dispersion of the viscous solution from the nozzles and not greatly affected by the particles.

The tensile strength (MPa) and the elongation (%) of the pure polyacrylonitrile nanofiber membrane were 8.72 MPa and 34%, respectively. The composite nanofibers membrane (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) were 8.81 MPa and 7%, respectively, but tensile strength was not changed with addition of adsorbed powder, but elongation was decreased.

Evaluation of Lithium Adsorption Capacity of Composite Nanofibers Membrane According to the Contents of Oxidized Lithium-Manganese-Adsorbed Powder

H _1.6 Mn _1.6 O ₄ adsorbed powder (HMO) and polyacrylonitrile were added 20, 40 and 60 wt% H _1.6 Mn _1.6 O ₄ adsorbing powder on the basis of the weight of the composite nanofibers, respectively, to a randomly prepared lithium solution And equilibrium lithium adsorption was evaluated by reacting in an incubator for 24 hours at 30 DEG C and 200 rpm stirring speed.

For the above evaluation, lithium hydroxide solution (7 to 35 mg / L) prepared by adding 1 mM LiOH solution and fixing the pH to 11 and lithium chloride (LiCl) added to the lithium solution was used Respectively.

Equilibrium lithium adsorption capacity (Qe) is defined by the formula (1) where C ₀ is the initial lithium concentration, C _e is the lithium concentration after the end of the adsorption reaction, V is the volume of solution and m is the dried H _1.6 Mn _1.6 O ₄ weight .

[Chemical Formula 1]

In particular, the equilibrium lithium adsorption evaluation of composite nanofiber lithium adsorption membranes prepared by different H _1.6 Mn _1.6 O ₄ contents was carried out using Freundlich and Langmuir adsorption equations as defined in formulas (2) and (3) Linear model.

(2)

(3)

In Formulas 2 and 3, K _f and n are Freundlich constants, while K _L is the Langmuir adsorption equilibrium constant. q _m represents the theoretical maximum lithium adsorption capacity.

FIG. 20 is a graph showing a linear model of equilibrium lithium adsorption of composite nanofibers prepared by different contents of H _1.6 Mn _1.6 O ₄ using the general formulas (2) and (3). The values calculated from the above formulas (2) and (3) are shown in Table 7 below.

Nanofiber membrane Formula 2 (Freundlich) (Langmuir) n K _f (mg / g) r ² K _L (L / mg) q _m (mg / g) r ² H _1.6 Mn _1.6 O ₄ (HMO) 12.82 8.06 0.90 0.99 10.7 0.99 PAN / H _1.6 Mn _1.6 O ₄ (20 wt%) 5.98 5.48 0.92 0.85 8.3 0.99 PAN / H _1.6 Mn _1.6 O ₄ (40 wt%) 6.06 5.59 0.97 0.95 9.5 0.99 PAN / H _1.6 Mn _1.6 O ₄ (60 wt%) 6.56 6.25 0.83 0.98 10.3 0.99

Based on the correlation coefficient _{^{(r 2), H 1.6 Mn}} 1.6 O Li adsorbed on ₄ adsorbed powder (HMO) and PAN / H _1.6 Mn _1.6 O ₄ in the H _1.6 Mn _1.6 O ₄ is formula (3) rather than Formula 2 (Freundlich) (Langmuir) is well suited to.

The maximum adsorption capacity q _m values were obtained from H _1.6 Mn _1.6 O _4. All composite nanofiber membranes (PAN / H _1.6 Mn _1.6 O ₄ ) showed lower q _m values than H _1.6 Mn _1.6 O ₄ adsorption powders, As the content of H _1.6 Mn _1.6 O ₄ increases, q _m value increases.

This is because the nano-composite hayeotgi nanofiber surface, while the content of H _1.6 Mn _1.6 O ₄ increase in the fiber H _1.6 Mn _1.6 O ₄ particles to stick together H _1.6 Mn _1.6 O ₄ having a large particle size of the particles increased. As a result, these phenomena reduced the clogging caused by the polyacrylonitrile binder, thereby minimizing the reduction of adsorbable sites by increasing the protons of H _1.6 Mn _1.6 O ₄ particles ejected onto the surface of the nanofibers.

Composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄  )

The regeneration performance of the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) was evaluated using a solution having a pH of 11 and a lithium concentration of 35 mg / L.

After each adsorption cycle, the nanofibers were immersed in 45 mL of 0.5 M HCl solution and acid-treated at 30 ° C for 24 hours to elute lithium ions. The regenerated PAN / H _1.6 Mn _1.6 O ₄ nanofibers after the acid treatment, After washing with deionized water until the pH was neutral, the water was removed with a kim-wipe tissue and then used for the next adsorption experiment.

The adsorption-desorption cycle experiment was repeated 5 times in total, and the experimental results are shown in Table 8 below.

Number of repetitions Adsorption amount (mg Li + / g H _1.6 Mn _1.6 O ₄ ) Desorption amount (mg Li + / g H _1.6 Mn _1.6 O ₄ ) pH 1 time 9.032 19.13 8.005 Episode 2 10.690 10.50 5.445 3rd time 9.691 9.85 5.780 4 times 9.534 9.50 5.945 5 times 9.610 9.47 6.095

As shown in Table 8, the equilibrium adsorption amount by the adsorbent in the first cycle was 10 mg Li ⁺ / g H _1.6 Mn _1.6 O _4, and in the first elution test by the acid treatment after the adsorption experiment, 17 mg / g of lithium was eluted . This is more than the amount of lithium recovered by the first adsorption test (10 mg / g). H _1.6 Mn _1.6 O ₄ added to the polyacrylonitrile nanofiber eluted 12% of the remaining lithium This is because the amount of adsorbed material eluted more than the adsorbed amount in the elution experiment.

In the second cycle, the amount of available ion exchange adsorption sites produced by the first elution process was relatively increased, and more lithium was recovered. As the total number of lithium adsorption cycles increased, the amount of lithium adsorption decreased slightly.

This tendency can be confirmed by the tendency of the equilibrium pH value measured after the adsorption experiment. Generally, when lithium is extracted from H _1.6 Mn _1.6 O ₄ in the acid treatment, some manganese also dissolves, resulting in decomposition of the structure of H _1.6 Mn _1.6 O _4. Eventually, the structure is further decomposed Lt; / RTI &gt;

However, from the experimental results, the lithium adsorption capacity decreased only 4.3% in the fifth adsorption experiment, indicating that the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄ ) is relatively chemically stable.

The reduction of the lithium adsorption capacity in the lithium adsorption and regeneration experiments by the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄ ) was minimized when the polyacrylonitrile serving as the binder was reacted with H _1.6 Mn _1.6 O ₄ Therefore, H _1.6 Mn _1.6 O ₄ immobilized in the polyacrylonitrile nanofibers from the regeneration experiment is chemically more stabilized, and it is possible to extend the life even in long-term use.

Furthermore, the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄ ) is easier to handle for use compared to H _1.6 Mn _1.6 O ₄ powder, and can be used to minimize the loss of H _1.6 Mn _1.6 O ₄ There is an advantage.

From the seawater concentrated water, PAN / H _1.6 Mn _1.6 O ₄  Evaluation of lithium adsorption performance of composite nanofiber membranes

To evaluate the ability of composite nanofiber membranes to recover lithium from actual seawater, a RO retentate seawater from a seawater desalination plant was used. Since the concentration of lithium in the seawater was low, 15 mg of LiCl was added to 1 L of the solution, and the ion concentration of the seawater-concentrated water was analyzed.

Cation Concentration (mg / L) Li ⁺ 0.60 × 10 ¹ Na ⁺ 1.97 x 10 ⁴ Mg ²⁺ 1.52 x 10 ³ Ca ²⁺ 3.58 × 10 ² K ⁺ 5.34 x 10 ² Tot-Fe 0.20 × 10 ¹ Zn ²⁺ 0.20 x 10 ^-2 Sr ²⁺ 0.48 x 10 ^-1

(Na ⁺ , K ⁺ , Ca) contained in the seawater concentrated water were measured using H _1.6 Mn _1.6 O ₄ adsorbed powder and a composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) ^{2 +,} and Mg ^{2 +} , were evaluated for the effect of lithium adsorption and selective separation ability by monovalent and divalent ions, which are in competition with each other.

More specifically, evaluation was performed using a distribution coefficient (K _D ) of the following chemical formula (4), a separation factor (?) Of the chemical formula (5), and a concentration factor (CF)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

The evaluation of the lithium adsorption of H _1.6 Mn _1.6 O ₄ adsorbed powder and composite nanofiber membranes (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) evaluated using Formulas 4 to 6 was evaluated according to the following table 10 and Table 11, respectively.

ion C _o
(mg / L) C _o
(mmol / L) C _e
(mmol / L) Q _e
(mmol / g) K _D
(mL / g) alpha
(Li, / Me) CF × 10 ^-3
(L / g) Li ⁺ 15.34 2.21 1.21 ± 1.25 占 1035.55 One 565.29 Na ⁺ 18,515 805.70 805.66 ± 0.05 ± 0.07 15401 0.1 Mg ²⁺ 2,359 97.08 96.63 ± 0.42 ± 4.38 233 4.4 K ⁺ 702 17.95 17.93 ± 0.02 ± 1.33 766 1.3 Ca ²⁺ 433 10.80 10.75 ± 0.05 ± 4.55 224 4.5

ion C _o
(mg / L) C _o
(mmol / L) C _e
(mmol / L) Q _e
(mmol / g) K _D
(mL / g) alpha
(Li, / Me) CF × 10 ^-3
(L / g) Li ⁺ 15.34 2.21 1.39 ± 1.07 ± 771.48 One 484.5 Na ⁺ 18,515 805.70 805.64 ± 0.08 ± 0.10 7563 0.1 Mg ²⁺ 2,359 97.08 96.52 ± 0.75 ± 7.72 93 7.5 K ⁺ 702 17.95 17.91 ± 0.06 ± 3.26 219 3.1 Ca ²⁺ 433 10.80 10.76 ± 0.06 ± 5.91 121 5.7

Table 10 and Referring to Table 11, H _1.6 Mn _1.6 O ₄ adsorbing powder and the Q _e value obtained from hybrid nanofiber membrane _{(PAN / H 1.6 Mn 1.6 O} 4, 60wt% H 1.6 Mn 1.6 O 4) is Li ⁺ & Gt ^; Mg &lt; ^{2 +} > > Na ⁺ > Ca &lt; ^{2 +} &gt; &gt; K ⁺ , which means that lithium ion has the highest selectivity.

The K _D values for the lithium ions of the H _1.6 Mn _1.6 O ₄ adsorbent powder and the composite nanofiber membranes (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) were much higher than other cations, Which means that ion adsorption far exceeds the non-selective surface adsorption of other cations.

The α value of the H _1.6 Mn _1.6 O ₄ adsorptive powder and the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) shows a higher separation efficiency for lithium ions compared to other cations , The CF value indicates that the other cations are already concentrated, while the lithium ions can be concentrated to approximately 500 times.

Compared with H _1.6 Mn _1.6 O ₄ , the composite nanofiber membranes (PAN / H _1.6 Mn _1.6 O _4, 60 wt% H _1.6 Mn _1.6 O ₄ ) exhibited slightly lower lithium adsorption capacity and slightly higher Q _e values for other cations The slight increase in Na ⁺ , Ca ²⁺ , Mg ²⁺ and K ⁺ adsorption is not considered to be considered because the K _D and CF values are low in the separation performance of the composite nanofiber membrane. Thus, the composite nanofiber membrane (PAN / H _1.6 Mn _1.6 O ₄ ) proved to be a potentially renewable material for the recovery of lithium ions from seawater.

While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Those skilled in the art will understand. Therefore, the scope of protection of the present invention should be construed not only in the specific embodiments but also in the scope of claims, and all technical ideas within the scope of the same shall be construed as being included in the scope of the present invention.

Claims (18)

Preparing a viscous solution by mixing the lithium-manganese oxide adsorbing powder and the polymer material in a solvent (step 1);
Electrospinning the viscous solution to produce a composite nanofiber film (step 2); And
And a step (step 3) of treating the composite nanofibrous film with an acid to impart a lithium adsorption capability to the composite nanofiber film.
The method according to claim 1,
The method of claim 1, further comprising the step of heat-treating the composite nanofiber film before the step (3).
The method of claim 2,
Wherein the heat treatment is performed in a temperature range lower than a melting point of the polymer material at a temperature higher than the glass transition temperature of the polymer material.
The method according to claim 1,
Wherein the lithium-manganese oxide adsorbing powder is any one of Li _1.6 Mn _1.6 O ₄ , Li _1.33 Mn _1.67 O ₄ , LiMnO ₂ and LiMn ₂ O ₄ .
The method according to claim 1,
Wherein the lithium-manganese oxide adsorption powder has an average diameter of 3 mu m or less.
The method according to claim 1,
Wherein the average diameter of the lithium-manganese oxide adsorbing powder is 1 占 퐉 or less.
The method according to claim 1,
Wherein the lithium-manganese oxide adsorbing powder is added to the solvent in an amount of 15 to 50 wt% based on the weight of the polymer material added to the solvent.
The method according to claim 1,
The polymer material may be any polymer selected from the group consisting of polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride, a copolymer thereof, or a mixture of one or more polymers Wherein the composite nanofiber is a polymer.
The method according to claim 1,
Wherein the polymeric material is added in an amount ranging from 15 to 25% by weight based on the weight of the solvent.
The method according to claim 1,
Wherein the polymer material is added in a range of 18 to 25 wt% based on the weight of the solvent.
Preparing a viscous solution by mixing the acid-treated lithium-manganese oxide adsorbing powder and the polymer substance in a solvent (step 1); And
And a step of electrospunning the viscous solution to produce a composite nanofiber film (step 2).
The method of claim 11,
Wherein the acid-treated lithium-manganese oxide adsorption powder is any one of H _1.6 Mn _1.6 O ₄ , H _1.33 Mn _1.67 O ₄ , HMnO ₂ and HMn ₂ O ₄ .
The method of claim 11,
Wherein the acid-treated lithium-manganese oxide adsorption powder is added to the solvent in an amount of 20 to 60 wt% based on the weight of the polymer material added to the solvent.
The method of claim 11,
The polymer material may be any polymer selected from the group consisting of polysulfone, polyethersulfone, polyacrylonitrile, polyvinylidene fluoride, cellulose acetate, and polyvinyl chloride, a copolymer thereof, or a mixture of one or more polymers Wherein the polymer is a polymer.
A composite nanofiber lithium adsorption membrane produced by any one of claims 1 to 10.
A composite nanofiber membrane produced by any one of claims 11 to 14.
A lithium recovery method, comprising recovering lithium from a recovered solution containing lithium using a composite nanofibrous lithium adsorbent film produced by the method of claim 15 or a composite nanofiber film produced by the method of claim 16.
18. The method of claim 17,
Wherein the lithium recovery is performed by immersing the composite nanofiber lithium adsorption film or the composite nanofiber film in the recovered solution.

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