CN114307690B - Monovalent cation exchange membrane and preparation method and application thereof - Google Patents
Monovalent cation exchange membrane and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a monovalent cation exchange membrane, a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) Electrodepositing the cation exchange base film to obtain a modified cation exchange base film; (2) Mixing a polymer monomer, an oxidant and the modified cation exchange base membrane obtained in the step (1), and carrying out polymerization reaction to obtain the monovalent cation exchange membrane. The positive electricity polymer layer is generated on the cation exchange base film through electrodeposition, then the conductive polymer layer is introduced, the firmness of the monovalent cation exchange film is improved through combination of the two layers, and the durability and the selectivity of the monovalent cation exchange film are enhanced. The monovalent cation exchange membrane can selectively separate mono-valent cations and divalent cations under the dual actions of electrostatic force and aperture screening, so that the monovalent ions pass through the membrane to separate the divalent ions, thereby achieving the separation effect.
Description
Technical Field
The invention relates to the technical field of membrane separation, in particular to a monovalent cation exchange membrane, a preparation method and application thereof.
Background
The direction of preparation of monovalent selective cation exchange membranes can be divided into two aspects, membrane matrix modification and membrane surface modification. During the experiment, the membrane surface modification mode is found to be simple and easy to operate, and the modified effect is better than that of most of membrane matrix modification modes, probably because the main occurrence of selectivity is on the membrane surface. In real life, a plurality of monovalent cation exchange membranes are prepared by applying electropositive polymers on the surface of the cation exchange membranes, so that the effect of blocking high-valence ions by the membranes is realized, the effect is mainly from the electrostatic force action of modified layers on the ions, and the repulsive force of the high-valence ions is far greater than that of the low-valence ions due to the fact that the high-valence ions contain more charges, so that the separation of single multivalent cations is realized.
One solution is to attach a modifying layer to the cation exchange membrane using electrostatic forces. The selectivity of this type of film is good, but it is difficult to achieve high stability by only electrostatic force between the modifying substance and the film, and the modifying layer gradually drops off with time, resulting in a decrease in selectivity, and it is necessary to recoat the film with the modifying layer. For example, immersing the cation exchange membrane in a PEI solution. The most typical example is the ASV membrane of the AGC in japan, where the selectivity is achieved by adding a modified layer of PEI to the surface of the cation exchange membrane, but since PEI is relatively soluble in aqueous and organic solutions, this tends to cause the modified layer to fall off in use. This gives the film a useful life, requires periodic coating modifications of the film, increases the difficulty of operation, and is not conducive to the improvement of the economics of the industrial process.
In order to solve the above-mentioned stability problem, a second solution has been developed to enhance the stability of the modified layer by generating new bonds through chemical reaction. This approach does achieve the intended purpose and increases the stability of the modified layer. Because many cationic substances do not have functional groups required by chemical reaction processes, an additional chemical pretreatment process is required in the preparation process, and high requirements are placed on the membrane substrate and the modified substances. The modified membrane may cause the increase of membrane resistance due to the increase of density, and the additional expenditure of cost is increased both in the process of producing the monovalent cation exchange membrane and in the process of using the monovalent cation exchange membrane, which is not beneficial to the popularization and the use of the membrane.
In order to reduce the modification resistance, conductive polymers are selected to prepare monovalent cation exchange membranes. The monomers of the substances are subjected to surface polymerization reaction on the surface of the cation exchange membrane to form a modified layer with a rigid structure, and the main selectivity of the modified layer to ions is derived from the pore size screening effect of the membrane. Although the conductive polymer has certain electropositivity, the electropositivity is weaker than that of the former two types of modified substances, so that the main selectivity of the modification is attributed to pore size screening action, the membrane prepared by the modification scheme has poorer selectivity but better affinity than that of the cationic modified membrane, and the polymerized modified layer is difficult to fall off from the membrane due to easy permeation of the monomer stage into the membrane.
CN 102941026a discloses a composite membrane selective for a single ion, which has a substrate of a common cation exchange membrane and a modified layer of polyethylenimine. The single cation with selectivity is Cu 2+ 、Zn 2+ 、Ni 2+ 、Hg 2+ 、Ag + 、Pt 2+ 、Co 2+ 、Cr 3+ It has been found in this invention that the separation of mono-multivalent ions by the action of the introduction of electrostatic forces is also very effective. However, the film modified by electrostatic force has poor stability, and the performance of the film is continuously reduced, and the film must be recoated. Therefore, the lifetime of the ion exchange membrane is short.
CN 108097069a discloses a method for preparing monovalent selective cation exchange membranes by forming polypyrrole on the membrane surface and also demonstrates that the stability of the structure is better than electrostatic forces. The method mainly utilizes the rigid structure of the conductive polymer, namely the pore size screening takes the dominant role, and no extra electrostatic repulsive force is introduced, so that the selectivity is always shown to be difficult to be greatly improved.
CN 112844058A discloses a preparation method of a single-sided modified cation exchange membrane, which comprises the steps of immersing the cation exchange membrane in a mixed solution of pyrrole and chitosan in a certain proportion, slowly dripping an oxidant into the mixed solution, taking out the membrane after the reaction is completed, immersing the membrane in glutaraldehyde solution to crosslink chitosan, and obtaining the single-sided modified cation exchange membrane. Although the method additionally introduces the positive polymer (chitosan) on the basis of polypyrrole, the mode continues to be a chemical crosslinking mode, the use of glutaraldehyde of the crosslinking agent increases the complexity and the cost of the process, and the process does not apply the special properties of the cationic polymer and the conductive polymer respectively. The durability of the film is also not mentioned in this invention.
How to improve the preparation technology of monovalent cation exchange membranes, improve the selectivity and the service life of the membranes, and is a technical problem which needs to be solved in the technical field of membrane separation.
Disclosure of Invention
In order to solve the technical problems, the invention provides the monovalent cation exchange membrane, the preparation method and the application thereof, wherein the monovalent cation exchange membrane improves the screening of ions, has higher selectivity and service life, is convenient for industrialized popularization and improves the economical efficiency of industrial production.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a monovalent cation exchange membrane, said method comprising the steps of:
(1) Electrodepositing the cation exchange base film to obtain a modified cation exchange base film;
(2) Mixing a polymer monomer, an oxidant and the modified cation exchange base membrane obtained in the step (1), and carrying out polymerization reaction to obtain the monovalent cation exchange membrane.
The invention generates an electropositive polymerization layer on the surface of the cation exchange base membrane by electrodeposition, and generates a conductive polymerization layer after the polymerization reaction of a polymer monomer and an oxidant. The modified layer obtained by combining the conductive polymer layer and the electropositive polymer layer improves the compactness and firmness of the monovalent cation exchange membrane, enhances the stability of the monovalent cation exchange membrane, and solves the technical problem that the electropositive polymer layer of the monovalent cation exchange membrane is easy to fall off, thereby being beneficial to popularization into industrial production and improving the economical efficiency of the industrial production. The monovalent cation exchange membrane prepared by the method can selectively separate mono-valent and divalent cations under the dual actions of electrostatic force and aperture screening, namely the monovalent cation exchange membrane can pass monovalent ions and separate divalent ions, so that the separation effect is achieved.
Preferably, the cation exchange membrane in step (1) is washed before being used, and the washing liquid used in the washing comprises deionized water and/or sodium chloride solution.
The concentration of the sodium chloride solution according to the present invention is 0.3 to 0.6mol/L, and for example, may be 0.3mol/L, 0.35mol/L, 0.4mol/L, 0.45mol/L, 0.5mol/L, 0.55mol/L or 0.6mol/L, but is not limited to the values recited, and other values not recited in the numerical range are equally applicable.
Preferably, the method of washing comprises: immersing unwashed cation exchange base membrane in washing liquid for 3-4h, and then carrying out ultrasonic washing for 3-5h to obtain the cation exchange base membrane.
The soaking time is 3-4h, for example, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
The ultrasonic washing time is 3-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the recited values, and other non-recited values in the range of values are equally applicable.
Preferably, the cation exchange base membrane of step (1) comprises a sulfonic acid group base membrane.
Preferably, the electrodeposited deposition solution of step (1) comprises an electropositive polymer and a medium.
The solvent of the deposition solution includes water.
Preferably, the electropositive polymer comprises an amino group-based high molecular polymer.
Preferably, the amino group-containing polymer comprises any one or a combination of at least two of polyethylenimine, polyethylenimine quaternary ammonium salt, chitosan quaternary ammonium salt, polyimide quaternary ammonium salt, polymeric imidazole quaternary ammonium salt, polystyrene methyl trimethyl amine salt, polyether sulfone methyl trimethyl amine salt, polysulfone methyl trimethyl amine salt or polyether ketone methyl trimethyl amine salt. Typical but non-limiting combinations include combinations of polyethylenimine and quaternary ammonium salts of polyethylenimine, combinations of quaternary ammonium salts of polyethylenimine and chitosan, combinations of chitosan and quaternary ammonium salts of chitosan, combinations of quaternary ammonium salts of chitosan and polyimide, combinations of quaternary ammonium salts of polyimide and polymeric imidazole, combinations of quaternary ammonium salts of polymeric imidazole and polystyrene-based methyltrimonium salts, combinations of polystyrene-based methyltrimonium salts and polyethersulfone-based methyltrimonium salts, combinations of polyethersulfone-based methyltrimonium salts and polysulfone-based methyltrimonium salts, or combinations of polysulfone-based methyltrimonium salts and polyetherketone-based methyltrimonium salts. Preferably any one or a combination of at least two of polyethylenimine, chitosan, a quaternary amine salt of polyethylenimine or a quaternary amine salt of chitosan.
Preferably, the concentration of the electropositive polymer in the deposition solution is 2-4g/L, which may be, for example, 2g/L, 2.5g/L, 3g/L, 3.5g/L, or 4g/L, but is not limited to the recited values, as other non-recited values within the range of values are equally applicable.
Preferably, the medium comprises an acid and/or a salt.
Preferably, the concentration of the deposition liquid medium is 0.8 to 1.2mol/L, for example, 0.8mol/L, 0.9mol/L, 1mol/L, 1.1mol/L or 1.2mol/L, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the time of electrodeposition in step (1) is 0.8-1.2h, for example, 0.8h, 0.9h, 1h, 1.1h or 1.2h, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the electrodepositing in step (1) has a current density of 5-15mA/cm 2 For example, it may be 5mA/cm 2 、7.5mA/cm 2 、10mA/cm 2 、12.5mA/cm 2 Or 15mA/cm 2 But not limited to, the values recited, within the range of valuesOther non-enumerated values are equally applicable.
The electropositive polymer layer is obtained by an electrodeposition method, the adsorption quantity of the electropositive polymer can be improved by controlling the pH of the deposition solution, the current density and the electrifying time of electrodeposition, and meanwhile, the electropositive polymer layer with uniform and stable structure is obtained.
Preferably, the polymer monomers of step (2) comprise pyrrole and/or dopamine.
Preferably, the oxidizing agent of step (2) comprises FeCl 3 、NaIO4、Na 2 S 2 O 8 、(NH) 4 S 2 O 8 Or H 2 O 2 Any one or a combination of at least two of these.
Preferably, the method of mixing of step (2) comprises: and (3) immersing the modified cation exchange base membrane obtained in the step (1) into a polymer monomer aqueous solution, and then dropwise adding an oxidant aqueous solution to complete mixing.
The polymer monomer provided by the invention is oxidized and polymerized to form a conjugate bond, so that a delocalized electron system is obtained, and macromolecules formed by oxidation have conductive performance, so that a conductive polymer layer is generated. Because the affinity between the polymer monomer and the membrane is better, the polymer monomer is easy to contact the surface of the membrane through osmosis, and the mixing method of firstly soaking the polymer monomer and then dripping the oxidant for oxidation in the step (2) ensures that the conductive polymer layer can be formed on the surface of the electropositive polymer layer and can permeate through the electropositive polymer layer to be formed on the surface of the cation exchange base membrane.
Preferably, the concentration of the aqueous polymer monomer solution is 0.05 to 0.15mol/L, for example, 0.05mol/L, 0.09mol/L, 0.1mol/L, 0.12mol/L or 0.15mol/L, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the concentration of the aqueous oxidant solution is 0.1 to 0.2mol/L, for example, 0.1mol/L, 0.12mol/L, 0.14mol/L, 0.16mol/L, 0.18mol/L or 0.2mol/L, but not limited to the recited values, and other non-recited values within the numerical range are equally applicable.
Preferably, the volume ratio of the aqueous polymer monomer solution to the aqueous oxidant solution is (6-7): 1, which may be, for example, 6:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1 or 7:1, but is not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the polymerization reaction in step (2) is carried out for a period of time ranging from 4 to 5 hours, and may be carried out for example for 4 hours, 4.2 hours, 4.4 hours, 4.6 hours, 4.8 hours or 5 hours, but not limited to the recited values, and other non-recited values within the range of values are equally applicable.
Preferably, the polymerization reaction in step (2) is carried out at a temperature of 20 to 40 ℃, for example, 20 ℃, 25 ℃, 30 ℃, 35 ℃ or 40 ℃, but not limited to the values recited, and other values not recited in the numerical range are equally applicable.
As a preferred technical scheme of the preparation method according to the first aspect of the present invention, the preparation method comprises the following steps:
(1) Immersing unwashed cation exchange base film in washing liquid for 3-4h, ultrasonic washing for 3-5h to obtain cation exchange base film, electrodepositing the cation exchange base film for 0.8-1.2h, and charging current density of 5-15mA/cm 2 Obtaining a modified cation exchange base membrane;
(2) Soaking the modified cation exchange base membrane obtained in the step (1) into a polymer monomer aqueous solution, then dropwise adding an oxidant aqueous solution, and carrying out polymerization reaction for 4-5h at 20-40 ℃ to obtain the monovalent cation exchange membrane;
the washing liquid comprises deionized water and/or sodium chloride solution; the cation exchange base membrane comprises sulfonic acid groups; the electrodeposited deposition solution comprises an electropositive polymer and a medium; the electropositive polymer comprises an amino high molecular polymer with the concentration of 2-4g/L; the amino high polymer comprises any one or a combination of at least two of polyethylenimine and quaternary amine salts thereof, chitosan and quaternary amine salts thereof, polyimide and quaternary amine salts thereof, polyimidazole and quaternary amine salts thereof, polystyrene methyltrimellidine salts, polyether sulfone methylated trimethylamine salts, polysulfone methyltrimellidine salts or polyether ketone methyltrimellidine salts; the medium comprises an acid and/or a salt; the concentration of the medium in the deposition solution is 0.8-1.2mol/L;
the polymer monomer comprises pyrrole and/or dopamine; the concentration of the polymer monomer aqueous solution is 0.05-0.15mol/L; the oxidant comprises FeCl 3 、NaIO 4 、Na 2 S 2 O 8 、(NH) 4 S 2 O 8 Or H 2 O 2 Any one or a combination of at least two of the following; the concentration of the oxidant aqueous solution is 0.1-0.2mol/L; the volume ratio of the polymer monomer aqueous solution to the oxidant aqueous solution is (6-7): 1.
In a second aspect, the present invention provides a monovalent cation exchange membrane obtainable by the process according to the first aspect.
In a third aspect, the present invention provides the use of a monovalent cation exchange membrane according to the second aspect for desalinating sea water.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The positive electricity polymer layer is generated on the cation exchange base film through electrodeposition, then the conductive polymer layer is introduced, the firmness of the monovalent cation exchange film is improved through combination of the two layers, and the durability and the selectivity of the monovalent cation exchange film are enhanced.
(2) The monovalent cation exchange membrane provided by the invention can selectively separate mono-divalent cations and divalent cations under the dual actions of electrostatic force and aperture screening, and even if the monovalent ions pass through, the divalent ions are blocked, so that the effect of separating the mono-divalent cations from the divalent cations is achieved.
Detailed Description
To facilitate understanding of the present invention, examples are set forth below. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.5h, immersing in 0.5mol/L sodium chloride solution, ultrasonic washing for 4h to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 1h, and applying current with density of 10mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and hydrochloric acid, the solvent is water, the concentration of polyethylenimine is 3g/L, and the concentration of hydrochloric acid is 1mol/L, and the modified cation exchange base membrane is obtained;
(2) Soaking the modified cation exchange membrane obtained in the step (1) into an aqueous solution of pyrrole monomer (Jiu Ding chemical, PE 879) with the concentration of 0.1mol/L, and then dropwise adding FeCl with the concentration of 0.15mol/L 3 And (3) carrying out polymerization reaction on the aqueous solution for 4.5 hours at the temperature of 30 ℃ after the dripping is completed, wherein the volume ratio of the aqueous solution is 6.5:1, and obtaining the monovalent cation exchange membrane.
Example 2
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.2h, immersing in 0.4mol/L sodium chloride solution, ultrasonic washing for 3.5h to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 0.9h, and charging with current density of 12mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai source leaf biotechnology Co., ltd.) and sulfuric acid, the solvent is water, the concentration of polyethylenimine is 2.5g/L, and the concentration of sulfuric acid is 0.9mol/L, and the modified cation exchange base membrane is obtained;
(2) Immersing the modified cation exchange membrane obtained in the step (1) into 0.08mol/L dopamine (Ron chemical reagent, R012298) aqueous solution, then dropwise adding 0.12mol/L NaIO4 aqueous solution, wherein the volume ratio is 6.2:1, and carrying out polymerization reaction for 4.8 hours at 25 ℃ after the dropwise adding is completed, so as to obtain the monovalent cation exchange membrane.
Example 3
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.8 hr, immersing in 0.55mol/L sodium chloride solution, ultrasonic washing for 4.5 hr to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 1.1 hr, and charging with current density of 8mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and sodium chloride, the solvent is water, the concentration of polyethylenimine is 3.5g/L, the concentration of sodium chloride is 1.1mol/L, and the modified cation exchange base membrane is obtained;
(2) Soaking the modified cation exchange membrane obtained in the step (1) into 0.11mol/L dopamine (Tianjin Ron chemical reagent, R012298) aqueous solution, and then dropwise adding Na with the concentration of 0.18mol/L 2 S 2 O 8 And (3) carrying out polymerization reaction on the aqueous solution for 4.2 hours at the temperature of 35 ℃ after the dripping is completed, wherein the volume ratio of the aqueous solution is 6.7:1, and obtaining the monovalent cation exchange membrane.
Example 4
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base film (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3 hr, immersing in 0.3mol/L sodium chloride solution, ultrasonic washing for 3 hr to obtain cation exchange base film, electrodepositing the cation exchange base film for 0.8 hr, and charging current density of 15mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and hydrochloric acid, the solvent is water, the concentration of polyethylenimine is 2g/L, the concentration of hydrochloric acid is 0.8mol/L, and the modified cation exchange base membrane is obtained;
(2) Soaking the modified cation exchange base membrane obtained in the step (1) into pyrrole (Jiudinghua) with the concentration of 0.05mol/LPE 879) was added dropwise to the aqueous solution at a concentration of 0.1mol/L (NH) 4 S 2 O 8 And (3) carrying out polymerization reaction on the aqueous solution at 20 ℃ for 5 hours after the dripping is completed, wherein the volume ratio of the aqueous solution is 6:1, and obtaining the monovalent cation exchange membrane.
Example 5
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base film (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 4 hr, immersing in 0.6mol/L sodium chloride solution, ultrasonic washing for 5 hr to obtain cation exchange base film, electrodepositing the cation exchange base film for 1.2 hr, and charging current density of 5mA/cm 2 The deposition solution is a mixed solution of polyethyleneimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and hydrochloric acid, the solvent is water, the concentration of polyethyleneimine is 4g/L, and the concentration of hydrochloric acid is 1.2mol/L, and the modified cation exchange base membrane is obtained;
(2) Soaking the modified cation exchange base membrane obtained in the step (1) into pyrrole (Jioding chemical, PE 879) water solution with the concentration of 0.15mol/L, and then dropwise adding H with the concentration of 0.2mol/L 2 O 2 And (3) carrying out polymerization reaction for 4 hours at the temperature of 40 ℃ after the solution is dropwise added, wherein the volume ratio of the solution is 7:1, and obtaining the monovalent cation exchange membrane.
Example 6
This example provides a monovalent cation exchange membrane, the process steps being the same as those of example 1 except that the polyethyleneimine of step (1) was replaced with chitosan of equal mass (C0831, division of medical science, ltd, shanghai).
Example 7
This example provides a monovalent cation exchange membrane, the process steps being the same as in example 1 except that the polyethyleneimine of step (1) is replaced with an equal mass polyimide (P874997, shanghai microphone Biochemical technologies Co., ltd.).
Example 8
This example provides a monovalent cation exchange membrane, the process steps being the same as in example 1 except that the polyethyleneimine of step (1) is replaced with an equal mass of polymeric imidazole (Shanghai Michelin Biochemical technologies Co., ltd., P909984).
Example 9
This example provides a monovalent cation exchange membrane having a current density of 3mA/cm except for step (1) 2 The remaining process steps are the same as in example 1.
Example 10
This example provides a monovalent cation exchange membrane having a current density of 17mA/cm except for the one described in step (1) 2 The remaining process steps are the same as in example 1.
Example 11
This example provides a monovalent cation exchange membrane, the process steps being the same as in example 1 except that the concentration of hydrochloric acid in step (1) is 0.5 mol/L.
Example 12
This example provides a monovalent cation exchange membrane, the process steps being the same as in example 1 except that the concentration of hydrochloric acid in step (1) is 1.5 mol/L.
Example 13
The present embodiment provides a monovalent cation exchange membrane, the method of preparing the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.5h, immersing in 0.5mol/L sodium chloride solution, ultrasonic washing for 4h to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 1h, and applying current with density of 10mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and hydrochloric acid, the solvent is water, the concentration of polyethylenimine is 3g/L, and the concentration of hydrochloric acid is 1mol/L, and the modified cation exchange base membrane is obtained;
(2) Soaking the modified cation exchange membrane obtained in the step (1) into pyrrole (Jiu Ding chemical, PE 879) and FeCl 3 Is a mixed solution of (1) pyrrole with a concentration of 0.1mol/L，FeCl 3 The concentration of the catalyst is 0.15mol/L, the volume ratio of the catalyst and the catalyst is 6.5:1, and the catalyst is subjected to polymerization reaction for 4.5 hours at 30 ℃ to obtain the monovalent cation exchange membrane.
Comparative example 1
The present comparative example provides a monovalent cation exchange membrane, the method of making the monovalent cation exchange membrane comprising the steps of:
(1) Immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.5h, immersing in 0.5mol/L sodium chloride solution, ultrasonic washing for 4h to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 1h, and applying current with density of 10mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (S25144, shanghai Yuan Ye Biotechnology Co., ltd.) and hydrochloric acid, the solvent is water, the concentration of polyethylenimine is 3g/L, and the concentration of hydrochloric acid is 1mol/L, and the modified cation exchange base membrane is obtained;
(2) Immersing the modified cation exchange base membrane obtained in the step (1) into pyrrole (Jiuding chemical, PE 879) monomer aqueous solution with the concentration of 0.1mol/L, and carrying out polymerization reaction for 4.5h at the temperature of 30 ℃ to obtain the monovalent cation exchange membrane.
Comparative example 2
The present comparative example provides a monovalent cation exchange membrane, the method of making the monovalent cation exchange membrane comprising the steps of:
immersing unwashed sulfonic acid group cation exchange base membrane (TRJCM, available from Beijing wetting film technology development Co., ltd.) in deionized water for 3.5h, immersing in 0.5mol/L sodium chloride solution, ultrasonic washing for 4h to obtain cation exchange base membrane, electrodepositing the cation exchange base membrane for 1h, and applying current with density of 10mA/cm 2 The deposition solution is a mixed solution of polyethylenimine (Shanghai source leaf biotechnology Co., ltd., S25144) and hydrochloric acid, the solvent is water, the concentration of polyethylenimine is 3g/L, and the concentration of hydrochloric acid is 1mol/L, and the monovalent cation exchange membrane is obtained.
Comparative example 3
This comparative example provides a sulfonic acid-based cation exchange membrane (TRJCM, inc. of Beijing wetting film technology development Co., ltd.) which has not been treated by the preparation method provided by the present invention.
Performance testing
The cation exchange membranes obtained in examples 1 to 13 and comparative examples 1 to 3 were subjected to a selectivity test and a stability test, and the results are shown in table 1.
Selectivity test: placing a cation exchange membrane in CaCl 2 In the mixed solution with NaCl, caCl 2 And NaCl at 0.1mol/L, respectively, and the applied current density was 10mA/cm 2 After 1h of power on, the Na on the side of the cation exchange membrane close to the cathode is measured + And Ca 2+ Concentration of Na is calculated + Relative to Ca 2+ Migration amount of (2) is expressed as
The calculation formula is as follows:
Stability test: the cation exchange membrane is placed in 1mol/L dilute hydrochloric acid, 10mA/cm is applied 2 Is electrified for 3 hours, the cation exchange membrane is taken out and placed in CaCl 2 In the mixed solution with NaCl, caCl 2 And NaCl at 0.1mol/L, respectively, of 10mA/cm 2 Is electrified for 1h, and the Na of the side of the cation exchange membrane close to the cathode is measured + And Ca 2+ Concentration of Na is calculated + Relative to Ca 2+ Migration amount of (2) is expressed as
TABLE 1
From table 1 the following conclusions are drawn:
(1) From examples 1 to 5, the present invention produced an electropositive polymeric layer on a cation exchange base membrane by electrodeposition, followed by the introduction of a conductive polymeric layer, improved the firmness of the monovalent cation exchange membrane by the combination of the two layers, and enhanced the durability and selectivity of the monovalent cation exchange membrane.
(2) As can be seen from a comparison of examples 6 to 8 and example 1, the electropositive polymer provided by the present invention can be combined with the conductive polymer layer by electrodepositing the electropositive polymer layer formed on the cation exchange base membrane, thereby improving the firmness of the monovalent cation exchange membrane and enhancing the durability and selectivity of the monovalent cation exchange membrane.
(3) As can be seen from a comparison of examples 9, 10 with example 1, when the electrodeposited current density exceeds 5-15mA/cm 2 In the process, the electrodeposition effect is not ideal, and the formed electropositive polymeric layer is unstable, so that the prepared monovalent cation exchange membrane has low selectivity and poor stability, which shows that the current density provided by the invention is beneficial to improving the firmness degree of the monovalent cation exchange membrane and enhancing the monovalent cationDurability and selectivity of ion exchange membranes.
(4) As is clear from comparison of examples 11 and 12 with example 1, when the concentration of the acid in the electrodeposition solution exceeds 0.8 to 1.2mol/L, the electrodeposition effect is not ideal, and the formed electropositive polymeric layer is unstable, so that the prepared monovalent cation exchange membrane has low selectivity and poor stability, which indicates that the concentration of the acid in the electrodeposition solution provided by the invention is favorable for improving the firmness degree of the monovalent cation exchange membrane and enhancing the durability and selectivity of the monovalent cation exchange membrane.
(5) As is apparent from a comparison of example 13 and example 1, when the modified cation exchange base membrane is added to the mixed solution of the polymer monomer and the oxidizing agent, rather than adding the polymer monomer first and then adding the oxidizing agent, the effect of the polymerization reaction is not ideal, and the formed conductive polymer layer cannot penetrate into the electrodeposited layer, so that the prepared monovalent cation exchange membrane has low selectivity and poor stability, which indicates that the mixing method provided by the invention is favorable for improving the firmness of the monovalent cation exchange membrane and enhancing the durability and selectivity of the monovalent cation exchange membrane.
(6) As is apparent from a comparison of comparative example 1 and example 1, when the oxidizing agent is not added, the effect of the polymerization reaction is not ideal, and the formed conductive polymeric layer is unstable, so that the prepared monovalent cation exchange membrane has low selectivity and poor stability, which indicates that the oxidizing agent provided by the invention is favorable for improving the firmness degree of the monovalent cation exchange membrane and enhancing the durability and selectivity of the monovalent cation exchange membrane.
(7) As is apparent from a comparison of comparative example 2 and example 1, when the conductive polymeric layer is not added, the prepared monovalent cation exchange membrane has low selectivity and poor stability, which indicates that the preparation of the conductive polymeric layer provided by the invention is beneficial to improving the firmness of the monovalent cation exchange membrane and enhancing the durability and selectivity of the monovalent cation exchange membrane.
(8) As can be seen from a comparison of comparative example 3 with example 1, the present invention produces a positively charged polymeric layer on a cation exchange base membrane by electrodeposition, and then introduces a conductive polymeric layer, improving the firmness of a monovalent cation exchange membrane by the combination of the two layers, and enhancing the durability and selectivity of the monovalent cation exchange membrane.
The detailed process flow of the present invention is described by the above embodiments, but the present invention is not limited to the above detailed process flow, i.e., it does not mean that the present invention must be implemented depending on the above detailed process flow. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (21)
1. A method of preparing a monovalent cation exchange membrane, said method comprising the steps of:
(1) Electrodepositing a cation exchange base film, wherein the electrodeposited deposition solution comprises an electropositive polymer and a medium, and an electropositive polymer layer is generated on the surface of the cation exchange base film to obtain a modified cation exchange base film;
(2) Mixing a polymer monomer, an oxidant and the modified cation exchange base membrane obtained in the step (1), performing polymerization reaction to generate a conductive polymer layer, and combining the conductive polymer layer and the electropositive polymer layer to obtain a modified layer to obtain the monovalent cation exchange membrane; the polymer monomers include pyrrole and/or dopamine.
2. The method according to claim 1, wherein the cation exchange membrane of step (1) is washed before use, and the washing solution used for washing comprises deionized water and/or sodium chloride solution.
3. The method of preparation according to claim 2, wherein the method of washing comprises: immersing unwashed cation exchange base membrane in washing liquid for 3-4h, and then carrying out ultrasonic washing for 3-5h to obtain the cation exchange base membrane.
4. The method of claim 1, wherein the cation exchange base membrane of step (1) comprises a sulfonic acid-based base membrane.
5. The method according to claim 1, wherein the electropositive polymer in step (1) comprises an amino group-based high molecular polymer.
6. The method according to claim 5, wherein the amino group-containing polymer comprises one or a combination of at least two of polyethylenimine, a quaternary ammonium salt of polyethylenimine, chitosan, a quaternary ammonium salt of chitosan, polyimide, a quaternary ammonium salt of polyimide, polyimidazole, a quaternary ammonium salt of polyimidazole, a polystyrenic methyltrimonium salt, a polyethersulfone-based methyltrimonium salt, a polysulfone-based methyltrimonium salt, and a polyetherketone-based methyltrimonium salt.
7. The method of claim 1, wherein the concentration of the electropositive polymer in the deposition solution is 2-4g/L.
8. The method of claim 1, wherein the medium comprises an acid and/or a salt.
9. The method according to claim 1, wherein the concentration of the medium in the deposition solution is 0.8 to 1.2mol/L.
10. The method of claim 1, wherein the electrodeposition time of step (1) is 0.8 to 1.2 hours.
11. The method according to claim 1, wherein the electrodeposited current density in step (1) is 5-15mA/cm 2 。
12. The method of claim 1, wherein the oxidizing agent of step (2) comprises FeCl 3 、NaIO 4 、Na 2 S 2 O 8 、(NH) 4 S 2 O 8 Or H 2 O 2 Any one or a combination of at least two of these.
13. The method of claim 1, wherein the method of mixing of step (2) comprises: and (3) immersing the modified cation exchange base membrane obtained in the step (1) into a polymer monomer aqueous solution, and then dropwise adding an oxidant aqueous solution to complete mixing.
14. The method according to claim 13, wherein the concentration of the aqueous polymer monomer solution is 0.05 to 0.15mol/L.
15. The method of claim 13, wherein the aqueous oxidant solution has a concentration of 0.1 to 0.2mol/L.
16. The method according to claim 13, wherein the volume ratio of the aqueous polymer monomer solution to the aqueous oxidant solution is (6-7): 1.
17. The process according to claim 1, wherein the polymerization reaction in step (2) is carried out for a period of 4 to 5 hours.
18. The process according to claim 1, wherein the polymerization reaction in step (2) is carried out at a temperature of 20 to 40 ℃.
19. The preparation method according to claim 1, characterized in that the preparation method comprises the steps of:
(1) Immersing unwashed cation exchange base film in washing liquid for 3-4h, ultrasonic washing for 3-5h to obtain cation exchange base film, electrodepositing the cation exchange base film for 0.8-1.2h, and charging current density of 5-15mA/cm 2 Generating an electropositive polymerization layer on the surface of the cation exchange base membrane to obtain a modified cation exchange base membrane;
(2) Soaking the modified cation exchange base membrane obtained in the step (1) into a polymer monomer aqueous solution, then dropwise adding an oxidant aqueous solution, and carrying out polymerization reaction for 4-5 hours at 20-40 ℃ to generate a conductive polymer layer, wherein the conductive polymer layer and the modified layer obtained by combining an electropositive polymer layer are used for obtaining the monovalent cation exchange membrane;
the washing liquid comprises deionized water and/or sodium chloride solution; the cation exchange base membrane comprises sulfonic acid groups; the electrodeposited deposition solution comprises an electropositive polymer and a medium; the electropositive polymer comprises an amino high molecular polymer with the concentration of 2-4g/L; the amino high polymer comprises any one or a combination of at least two of polyethylenimine and quaternary ammonium salt thereof, chitosan and quaternary ammonium salt thereof, polyimide and quaternary ammonium salt thereof, polyimidazole and quaternary ammonium salt thereof, polystyrene methyl trimethyl amine salt, polyether sulfone methyl trimethyl amine salt, polysulfone methyl trimethyl amine salt or polyether ketone methyl trimethyl amine salt; the medium comprises a salt and/or an acid; the concentration of the medium in the deposition solution is 0.8-1.2mol/L;
the polymer monomer comprises pyrrole and/or dopamine; the concentration of the polymer monomer aqueous solution is 0.05-0.15mol/L; the oxidant comprises FeCl 3 、NaIO 4 、Na 2 S 2 O 8 、(NH) 4 S 2 O 8 Or H 2 O 2 Any one or a combination of at least two of the following; the concentration of the oxidant aqueous solution is 0.1-0.2mol/L; the volume ratio of the polymer monomer aqueous solution to the oxidant aqueous solution is (6-7): 1.
20. A monovalent cation exchange membrane obtainable by the process of any one of claims 1 to 19.
21. Use of a monovalent cation exchange membrane according to claim 20 for desalinating seawater.
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