Preparation of hydrogen ion selective separation membrane and its application in electrodialysis acid recovery

Abstract

The application discloses a preparation of a hydrogen ion selective separation membrane and application of the hydrogen ion selective separation membrane in acid recovery by electrodialysis. The hydrogen ion selective separation membrane utilizes a hydrogen bond network and a hydrophobic chain to repel high-valence cations, and can realize efficient separation in the process of acid recovery by electrodialysis. The preparation method of the hydrogen ion selective separation membrane is simple, mass production is realized, and the hydrogen ion selective separation membrane has many advantages such as excellent effect, long service life and excellent mechanical property in the aspect of acid recovery by electrodialysis.

Description

Technical Field

[0001] This invention belongs to the field of selective electrodialysis technology, specifically relating to the preparation of a hydrogen ion selective separation membrane and its application in electrodialysis acid recovery. Background Technology

[0002] In industries such as smelting, electroplating, mining, and metal surface processing, the cleaning or leaching of metal components from metal surfaces requires the use of large quantities of inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid. The resulting wastewater is highly acidic and corrosive. Direct discharge of acidic wastewater into environmental water bodies can have a significant impact on the surrounding ecosystem and infrastructure, such as causing aquatic organism mutations, affecting plant growth, and corroding underground pipes. Furthermore, the metal ions in the acidic wastewater can cause serious environmental pollution. Direct loss of waste acid not only results in substantial waste but also damages the ecological environment. my country generates over 100 million tons of waste acid annually, making it imperative to improve the utilization rate of waste acid resources for sustainable industrial development. However, waste acid varies in concentration, originates widely, and has complex compositions. Currently used separation methods include concentration, extraction, distillation, and chemical oxidation, but these methods suffer from high processing costs and are prone to causing secondary pollution.

[0003] Membrane treatment technology, due to its advantages such as small footprint, high degree of automation, and stable effluent, is widely used in wastewater treatment and reclaimed water recycling. Among these, diffusion dialysis based on anion exchange membranes, a concentration gradient-driven membrane separation technology, has been widely applied in the aforementioned waste acid recovery industry. Diffusion dialysis is based on the selective separation of membranes, using a concentration gradient as the driving force to diffuse small solute molecules to the side with lower concentration, thus achieving substance separation. In acid recovery, the feed solution and the recovered solution are located on opposite sides of the anion exchange membrane. Because the anion exchange membrane itself is positively charged, it attracts anions while repelling cations. Under the concentration gradient, anions in the feed solution pass through the ion exchange membrane and enter the side with lower concentration, forming the recovered solution. Due to charge balance, some cations are also carried along with the anions. However, due to other cations (such as Fe...),... 2+ Zn 2+ Ni 2+ Al 3+ (etc.) have a large hydration radius and exhibit a high valence state, therefore H with a smaller hydration radius +Diffusion dialysis is superior to other cation exchange membranes used for anion exchange, thus achieving the separation of impurities from acids. It can be carried out at ambient temperature and pressure, has low installation and operating costs, simple equipment that is easy to automate, low energy consumption, mild operating conditions, and minimal environmental pollution, making it suitable for industrial production. However, diffusion dialysis also has certain limitations in engineering applications. Compared to other membrane treatment technologies, its processing capacity is relatively small, and it requires a low concentration of suspended solids in the feed water. Due to the low concentration of recovered acid, it generally needs to be concentrated again in industrial production before it can be recycled. Selective electrodialysis can recover acid from waste acid solutions and simultaneously increase its concentration, solving the problems associated with acid recovery in diffusion dialysis. The monovalent ion selective separation membrane, as the core component of selective electrodialysis, determines the acid recovery efficiency. In industrial production, the commercial monovalent ion selective separation membrane market is monopolized by two Japanese companies, and suffers from high prices, low acid recovery efficiency, and low metal ion rejection rates. Therefore, there is an urgent need to develop an industrially scalable monovalent ion selective separation membrane that has high selective permeability, a simple preparation process, low production cost, and good mechanical properties.

[0004] The *Journal of Membrane Science* (563, 2018, 320-325) reports a monovalent cation-selective separation membrane with zwitterionic side chains containing two quaternary ammonium groups and one sulfonic acid group. The presence of the quaternary ammonium groups enhances the electrostatic repulsion between the ion channel and high-valent cations, effectively preventing their passage and significantly improving the membrane's ion separation performance. In acid recovery electrodialysis tests, this monovalent cation-selective separation membrane exhibited excellent H₂O₂ concentration. + Flux (16.92 mol·h) -1 ·m -2 (approximately 2.5 times that of commercial cation-selective separation membranes CSO) and higher H + / Zn 2+ Ion selectivity is 23.5, approximately 6.7 times that of CSO. However, its preparation process is relatively complex, which is not conducive to large-scale production. The *Journal of Materials Chemistry A* (2018, 6, 22940-22950) reported a comb-shaped sulfonated polyether ether ketone (SPEEK) membrane with long alkyl (butyl and octyl) side chains, where the degree of substitution can be controlled by adjusting the amount of activating agent added. The comb-shaped membrane, through hydrophilic-hydrophobic separation, can effectively allow H+ ions to pass through. + It can transport molecules, but its low ion exchange capacity and low water absorption rate result in high membrane resistance.

[0005] Currently, monovalent selective separation membranes suffer from problems such as low selective separation performance, low ion flux, and complex membrane preparation processes. To address these issues, this invention proposes a method for preparing a hydrogen ion selective separation membrane for acid recovery. This method has the potential for large-scale application, excellent mechanical properties, good stability, significant separation selectivity, and high ion flux. Summary of the Invention

[0006] To address existing technical problems, this invention proposes the preparation of a hydrogen ion selective separation membrane and its application in electrodialysis acid recovery. The hydrogen ion selective separation membrane of this invention utilizes hydrogen bonding networks and hydrophobic chains to repel high-valence cations, achieving efficient separation during electrodialysis acid recovery. The preparation method of this hydrogen ion selective separation membrane is simple, allows for large-scale production, and offers numerous advantages in electrodialysis acid recovery, including excellent performance, long service life, and superior mechanical properties.

[0007] This invention proposes a method for preparing a hydrogen ion selective separation membrane, the specific steps of which are as follows:

[0008] S1: Using an ether-free polymer as the main chain, and then soaking it in a sodium hydroxide solution;

[0009] S2: Dissolve bromoalkylamine hydrobromide and acyl chloride monomer in organic solvent 1 and react to obtain solution I containing bromo small molecule monomer;

[0010] S3: Dissolve the polymer in organic solvent 1, add solution I to react, and prepare the membrane solution;

[0011] S4: Coat the membrane solution onto the substrate and dry it to obtain a hydrogen ion selective separation membrane.

[0012] In S1, the structural formula of the ether-free polymer is:

[0013]

[0014] in, Specifically Ar stands for benzene ring, m is an integer from 2 to 6, and Ar are connected in three forms: ortho, meta, and para.

[0015] In S1, the concentration of sodium hydroxide is 0.2 mol / L-3 mol / L; the soaking time is 2-48 h.

[0016] In S2, the organic solvent 1 is N-methylpyrrolidone.

[0017] In S2, the bromoalkylamine hydrobromide is selected from one of 2-bromoethylamine hydrobromide, 3-bromopropylamine hydrobromide, or 4-bromobutylamine hydrobromide.

[0018] The acyl chloride monomer is selected from one of propionyl chloride, butyryl chloride, valerate, hexanoyl chloride, or heptanyl chloride.

[0019] The structural formula of the brominated small molecule monomer in solution I is:

[0020]

[0021] n = 3 or 4, and n' takes values ​​from 3 to 7.

[0022] In S3, the molar ratio of the polymer material to the brominated small molecule monomer (c) is 1:(0.1-1); the reaction conditions are 40℃~60℃ for 48h.

[0023] In S4, the drying conditions are drying at 80℃~100℃ for 8 hours.

[0024] In S4, the thickness of the membrane is controlled between 10-100 μm.

[0025] The application of the hydrogen ion selective separation membrane of this invention is to separate hydrogen ions and metal ions with higher valence states than hydrogen ions during the electrodialysis acid recovery process.

[0026] The hydrogen ion selective separation membrane prepared by this invention is a homogeneous membrane, which avoids the defects of hydrogen ion selective separation membranes prepared by surface modification. Its effectiveness is specifically reflected in the following aspects:

[0027] (1) The polymer backbone structure without ether bonds does not contain other active groups such as ether, sulfur, and ketone, which improves its mechanical properties and extends its service life. At the same time, the polymer uses its own protons to screen ions, does not contain side-chain polymer electrolytes, has good stability, and has a simple and rapid preparation method. Starting from the polymer molecular chain design and micro-control, this invention prepares a hydrogen ion selective separation membrane with excellent mechanical properties, good stability, extremely significant separation selectivity, and high ion flux.

[0028] (2) Utilizing the property that pyridine groups can form stable salts with strong acids, and the fact that the nitrogen atom on the pyridine group has unshared electron pairs, the preparation conditions of the superacid environment of the ether-free polymer, with its strong proton-donating properties, allow the nitrogen atom to readily acquire protons, making the pyridine group positively charged. This is equivalent to the main chain itself containing positively charged functional groups, and these functional groups cover every pyridine ring on every main chain, exhibiting extremely high uniformity and ensuring that the prepared membrane has high ion flux. In addition, by controlling the ratio of alkyl-side long chains to the protonated polymer main chain, the proton distribution can be regulated, maximizing the functional groups inside the polymer membrane, thereby maximizing hydrogen ion flux and reducing membrane resistance.

[0029] (3) The hydrophilicity and hydrophobicity of the membrane can be controlled by using the alkyl side long chains bridged by amide bonds. Specifically, different alkyl side long chains have different hydrophilicity and hydrophobicity. Since high-valence metal ions have higher hydration energy than hydrogen ions, the alkyl side long chains bridged by amide bonds of different lengths and contents can achieve the separation of hydrogen ions and metal ions.

[0030] (4) Selective separation of hydrogen ions and ferrous ions is achieved by utilizing the hydrogen bond network formed by the alkyl side long chains bridged by amide bonds. Because O-H-N hydrogen bonds exist between the amide bonds, a hydrogen bond network can be formed to achieve selective separation of hydrogen ions. Specifically, the hydrogen bond network acts as another "ion channel," actively and rapidly transporting protons; simultaneously, the non-covalent crosslinks formed by the hydrogen bond network block the migration of ferrous ions, thus improving the selective separation of hydrogen ions and ferrous ions. Attached Figure Description

[0031] Figure 1 The hydrogen ion selective separation membranes prepared in Examples 1, 2 and 3 of this invention have hydrogen nuclear magnetic resonance spectra (NMR spectra). 1 H-NMR);

[0032] Figure 2 The tensile stress of the hydrogen ion selective separation membrane prepared in Example 1 of this invention;

[0033] Figure 3 A schematic diagram of the hydrogen ion selective separation membrane and its internal structure shown in Embodiment 1 of the present invention;

[0034] Figure 4 A schematic diagram of the electrodialysis testing device in an embodiment of the present invention. Detailed Implementation

[0035] This invention provides a method for hydrogen ion selective separation membrane, which is described in detail below. The specific experimental steps are as follows:

[0036] S1: A certain amount of biphenyl and 4-acetylpyridine were dissolved in dichloromethane. Trifluoromethanesulfonic acid was added as a catalyst under low temperature conditions, and the mixture was stirred for 24 hours. After the reaction was completed, the above reaction solution was slowly dissolved in deionized water to precipitate an ether-free polymer. The ether-free polymer was then soaked in sodium hydroxide solution, followed by repeated soaking and rinsing with pure water to remove residual alkaline solution from the surface. After drying, the polymer material was obtained.

[0037] S2: Dissolve a certain amount of bromoalkylamine hydrobromide in N-methylpyrrolidone, and add acyl chloride monomer dropwise to react and obtain a solution containing bromo-containing small molecule monomer.

[0038] S2: Dissolve a certain amount of polymer material in N-methylpyrrolidone, add a solution containing bromine-containing small molecule monomers to react, and prepare a membrane solution.

[0039] S3: Coat the membrane solution onto the substrate and dry it at 80℃~100℃ for 8 hours to obtain a hydrogen ion selective separation membrane for acid recovery.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0041] Example 1:

[0042] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0043] S1: Dissolve 3.084 g of biphenyl in 5 mL of dichloromethane. Add 3.15 g of 4-acetylpyridine to a round-bottom flask equipped with a mechanical stirrer and stir continuously in an ice bath until completely dissolved. When the reaction system is below 5°C, slowly add 24 mL of trifluoromethanesulfonic acid while stirring to prevent excessive exothermic reaction. Then add 1.1 mL of trifluoroacetic acid. After stirring the reaction for 8 hours, precipitate the mixture in deionized water.

[0044] The precipitate was washed in a 2 mol / L sodium hydroxide solution and stirred into smaller fragments using a mechanical stirrer, then soaked for 24 hours. After soaking, it was continuously washed with deionized water and filtered until the pH of the final wash solution reached 7. The solution was then dried at 80°C for 12 hours.

[0045] S2: Take 2g of bromopropylamine hydrobromide and 0.9g of propionamide and react them in N-methylpyrrolidone to obtain a solution containing a bromo-containing small molecule monomer; take 1g of the polymer and dissolve it in 9g of N-methylpyrrolidone, add a solution containing 0.32g of bromo-containing small molecule monomer, and react at 40℃ for 48h.

[0046] S3: The membrane solution is uniformly coated onto a glass plate and heated at 80°C for 8 hours. The membrane is then bonded to the glass plate to obtain a hydrogen ion selective separation membrane.

[0047] The hydrogen ion selective separation membrane obtained in this embodiment was used for acid recovery. Its performance was tested by electrodialysis. The electrodialysis conditions were: a mixed solution of 0.2667 mol / L FeCl2 and 1 mol / L HCl in the desalination chamber, 0.01 mol / L HCl in the concentration chamber, 0.3 mol / L Na2SO4 in the electrode chamber, and a current density of 10 mA / cm². 2 The time was 1 hour, and the effective area of ​​the membrane was 21 cm². 2 .

[0048] The formula for calculating ion flux is:

[0049]

[0050] Where J is the flux of ions through the membrane, in mol·m⁻¹. -2 ·h;

[0051] C t C0 and C0 are the ion concentrations in the concentration chamber at time t and the initial time, respectively, in mol / L.

[0052] V is the volume of the solution in the concentration chamber, expressed in liters (L).

[0053] A m The effective contact area between the membrane and the solution, expressed in m². 2 ;

[0054] t represents the electrodialysis operation time, in hours (h).

[0055] The formula for calculating ion selectivity is:

[0056]

[0057] in, and Fe at the initial temperature of the desalination chamber 2+ and H + The concentration of ions, expressed in mol / L.

[0058] Electrodialysis testing revealed that the flux of ferrous ions in the product of Example 1 during acid recovery testing was [value missing]. Hydrogen ion flux is Ion selectivity Example 2:

[0059] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0060] S1: The same preparation method as in Example 1 is used.

[0061] S2: Take 2g of bromopropylamine hydrobromide and 0.9g of propionamide and react them in N-methylpyrrolidone to obtain a solution containing a bromo-containing small molecule monomer; take 1g of polymer material and dissolve it in 9g of N-methylpyrrolidone, add a solution containing 0.46g of bromo-containing small molecule monomer, and react at 40℃ for 48h.

[0062] S3: The same preparation method as in Example 1 is used.

[0063] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 2 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 3:

[0064] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0065] S1: The same preparation method as in Example 1 is used.

[0066] S2: The same preparation method as in Example 1 is used, except that a solution containing 0.53g of a brominated small molecule monomer is added.

[0067] S3: The same preparation method as in Example 1 is used.

[0068] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 3 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 4:

[0069] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0070] S1: The same preparation method as in Example 1 is used.

[0071] S2: Take 2g of bromopropylamine hydrobromide and 1.3g of hexamethylenetetramine and react them in N-methylpyrrolidone to obtain a solution containing 0.46g of a brominated small molecule monomer; take 1g of the protonated polymer and dissolve it in 9g of N-methylpyrrolidone, add a solution containing 0.37g of a brominated small molecule monomer, and react at 40℃ for 48h.

[0072] S3: The same preparation method as in Example 1 is used.

[0073] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 4 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 5:

[0074] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0075] S1: The same preparation method as in Example 1 is used.

[0076] S2: The same preparation method as in Example 4 is used, except that a solution containing 0.61g of a brominated small molecule monomer is added.

[0077] S3: The same preparation method as in Example 1 is used.

[0078] In this embodiment, the hydrogen ion selective separation membrane's performance in acid recovery was tested via electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 5 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 6:

[0079] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0080] S1: The same preparation method as in Example 1 is used.

[0081] S2: The same preparation method as in Example 4 is used, except that a solution containing 0.86g of a brominated small molecule monomer is added.

[0082] S3: The same preparation method as in Example 1 is used.

[0083] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 6 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 7:

[0084] The steps for preparing a hydrogen ion selective separation membrane are as follows:

[0085] S1: The same preparation method as in Example 1 is used.

[0086] S2: The same preparation method as in Example 4 is used, except that a solution containing 1.1g of a brominated small molecule monomer is added.

[0087] S3: The same preparation method as in Example 1 is used.

[0088] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 7 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 8:

[0089] S1: The same preparation method as in Example 1 is used.

[0090] S2: Take 2g of bromopropylamine hydrobromide and 1.5g of hexamethylenetetramine and react them in N-methylpyrrolidone to obtain a solution containing a bromo-containing small molecule monomer; take 1g of the protonated polymer and dissolve it in 9g of N-methylpyrrolidone, add a solution containing 0.4g of the bromo-containing small molecule monomer, and react at 40℃ for 48h.

[0091] S3: The same preparation method as in Example 1 is used.

[0092] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 8 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 9:

[0093] S1: The same preparation method as in Example 1 is used.

[0094] S2: The same preparation method as in Example 8 is used, except that a solution containing 0.66g of a brominated small molecule monomer is added.

[0095] S3: The same preparation method as in Example 1 is used.

[0096] In this embodiment, the hydrogen ion selective separation membrane's performance in acid recovery was tested via electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 9 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 10:

[0097] S1: The same preparation method as in Example 1 is used.

[0098] S2: The same preparation method as in Example 8 is used, except that a solution containing 0.93g of a brominated small molecule monomer is added.

[0099] S3: The same preparation method as in Example 1 is used.

[0100] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 10 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 11:

[0101] S1: The same preparation method as in Example 1 is used.

[0102] S2: The same preparation method as in Example 8 is used, except that a solution containing 1.2g of a brominated small molecule monomer is added.

[0103] S3: The same preparation method as in Example 1 is used.

[0104] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 11 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity Example 12:

[0105] S1: The same preparation method as in Example 1 is used.

[0106] S2: Take 2g of bromopropylamine hydrobromide and 1.75g ​​of hexamethylenetetramine and react them in N-methylpyrrolidone to obtain a solution containing a bromo-containing small molecule monomer; take 1g of the protonated polymer and dissolve it in 9g of N-methylpyrrolidone, add a solution containing 0.43g of the bromo-containing small molecule monomer, and react at 40℃ for 48h.

[0107] S3: The same preparation method as in Example 1 is used.

[0108] In this embodiment, the performance of the hydrogen ion selective separation membrane for acid recovery was tested by electrodialysis, under the same conditions as in Example 1. After electrodialysis testing, the flux of ferrous ions in the product of Example 12 was measured to be [value missing]. Hydrogen ion flux is Ion selectivity

Claims

1. An application of a hydrogen ion selective separation membrane, characterized in that: The hydrogen ion selective separation membrane is used to separate hydrogen ions and metal ions with higher valence states than hydrogen ions during the electrodialysis acid recovery process. The hydrogen ion selective separation membrane is prepared by a method comprising the following steps: S1: Using an ether-free polymer as the main chain, and then soaking it in a sodium hydroxide solution; S2: Dissolve bromoalkylamine hydrobromide and acyl chloride monomer in organic solvent 1 and react to obtain solution I containing bromo small molecule monomer; S3: Dissolve the polymer of S1 in organic solvent 1, add solution I to react, and prepare the membrane liquid; S4: Coat the membrane solution onto the substrate and dry it to obtain a hydrogen ion selective separation membrane; In S1, the general structural formula of the ether-free polymer is as follows: ； in, Specifically Ar stands for benzene ring, m is an integer from 2 to 6, and Ar are connected in three ways: ortho, meta or para. In S2, the general structural formula of the brominated small molecule monomer is: ； n = 3 or 4, and n' takes values ​​from 3 to 7.

2. The application according to claim 1, characterized in that: In S1, the concentration of sodium hydroxide is 0.2 mol / L-3 mol / L, and the soaking time is 2-48 h.

3. The application according to claim 1, characterized in that: In S2, the bromoalkylamine hydrobromide is selected from one of 2-bromoethylamine hydrobromide, 3-bromopropylamine hydrobromide, or 4-bromobutylamine hydrobromide.

4. The application according to claim 1, characterized in that: In S2, the acyl chloride monomer is selected from one of propionyl chloride, butyryl chloride, valerate, hexanoyl chloride, or heptanyl chloride.

5. The application according to claim 1, characterized in that: In S3, the molar ratio of the polymer material to the brominated small molecule monomer (c) is 1:(0.1-1).

6. The application according to claim 1, characterized in that: In S3, the reaction conditions are 40℃~60℃ for 48h.

7. The application according to claim 1, characterized in that: In S4, the thickness of the membrane is controlled between 10-100 μm.

8. The application according to claim 1, characterized in that: The organic solvent 1 is N-methylpyrrolidone.

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