A covalent organic framework membrane for waste acid recovery and power generation, and a preparation method and application thereof

Abstract

This invention provides a covalent organic framework membrane for waste acid recovery and power generation, its preparation method, and its application, relating to the field of wastewater separation and recovery technology. The invention utilizes a PaTp-TMC membrane formed on a substrate surface using p-phenylenediamine, trialdehyde resorcinol, and trimesoyl chloride. This covalent organic framework membrane exhibits high selectivity and can achieve high efficiency for H+ ions. + Its ultra-fast transport and efficient retention of other ions enable it to simultaneously complete two processes: waste acid recovery and power generation (osmotic energy conversion), greatly improving the efficiency of process applications.

Description

Technical Field

[0001] This invention relates to the field of wastewater separation and recycling technology, and in particular to a covalent organic framework membrane that can be used for waste acid recovery and power generation, its preparation method, and its application. Background Technology

[0002] In industrial processes such as metal smelting, etching, and mining, large quantities of inorganic acids, including hydrochloric acid, sulfuric acid, and nitric acid, are used to clean metal surfaces or extract metal components. If the waste acids generated from these processes are discharged directly without treatment, it not only poses a significant threat to the environment but also results in a massive waste of resources. Therefore, the resource recovery and recycling of waste acids has become a major trend in waste acid treatment. Osmotic energy is a abundant and readily available renewable clean energy source, with the most common osmotic power generation coming from the mixing of river and seawater. However, the use of acidic industrial wastewater for osmotic energy generation is often overlooked. In particular, acidic wastewater discharged from chemical plants contains a large number of protons and various inorganic ions, providing a prerequisite for obtaining osmotic energy based on proton gradients.

[0003] Traditional methods for treating waste acid include neutralization precipitation, distillation, solvent extraction, and membrane treatment. Among these, membrane treatment technology has advantages such as low energy consumption, small equipment footprint, and high separation efficiency, and is widely used in wastewater treatment. However, it also suffers from problems such as secondary pollution, high energy consumption, and cumbersome operation. In recent years, two-dimensional nanofluidic channel membrane materials, inspired by eel ion channel proteins, have exhibited excellent energy conversion performance. Sun et al. designed a membrane with uniform angstrom-level pores and built-in charge-assisted hydrogen bond donors, which preferentially conducts HCl while exhibiting negligible conductivity to other compounds. The COFMs synthesized by Banerjee et al. have high application value in sulfuric acid recovery. Wang et al. reported a RED device based on a two-dimensional (2D) layered Ti3C2Tx MXene membrane for harvesting permeation energy from industrial wastewater with a proton gradient. However, the permeation performance and separation performance of membrane materials currently reported for acidic wastewater recovery or permeation energy harvesting are mutually exclusive, and can only achieve one of the two applications: waste acid resource recovery or power generation from acidic solutions. In view of this, it is necessary to provide a new type of separation membrane material to solve the problem of balancing high permeability and high selectivity, and to simultaneously realize the two processes of waste acid resource recovery and power generation (i.e., permeation energy conversion). Summary of the Invention

[0004] In view of the shortcomings of the prior art, the first objective of this invention is to provide a method for preparing a covalent organic framework membrane that can be used for waste acid recovery and power generation.

[0005] The second objective of this invention is to provide a covalent organic framework membrane that can be used for waste acid recovery and power generation.

[0006] A third objective of this invention is to provide applications of covalent organic framework membranes that can be used for waste acid recovery and power generation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a covalent organic framework membrane that can be used for waste acid recovery and power generation, comprising the following steps:

[0009] (1) Dissolve p-phenylenediamine (Pa) in ultrapure water to obtain solution A, and dissolve trialdehyde phloroglucinol (Tp) and trimesoyl chloride (TMC) in n-hexane to obtain solutions B and C respectively;

[0010] (2) Solution A is dropped onto the surface of the PES membrane to form a Pa layer; then solution B is added to react with Pa to form a Pa-Tp composite layer; finally, solution C is added to react with the Pa-Tp composite layer to form a Pa-Tp-TMC membrane, and excess solution is removed.

[0011] (3) Solidification yields a covalent organic framework membrane that can be used for waste acid recovery and power generation, which is then stored in ultrapure water.

[0012] Further, in step (1), the mass fraction of p-phenylenediamine in solution A is 1-3%, the mass fraction of trialdehyde phloroglucinol in solution B is 0.01-0.1%, and the mass fraction of pyromellitic acid chloride in solution C is 0.1-0.3%.

[0013] Furthermore, in step (2), the PES membrane is soaked in ultrapure water before solution A is added, and the soaking time is 12-36 hours.

[0014] Further, in step (2), the volume ratio of solution A, solution B and solution C is (12-18):(7-13):(7-13), preferably 15:10:10.

[0015] Furthermore, in step (2), the residence time of solution A on the surface of the PES membrane is 10-40s, preferably 30s.

[0016] Furthermore, in step (2), the reaction time between solution B and Pa is 5-15s, preferably 10s.

[0017] Further, in step (2), the reaction time between solution C and the Pa Tp composite layer is 10-40 s, preferably 30 s.

[0018] Further, in step (3), the curing temperature is 70-90℃, preferably 80℃; the curing time is 3-7min, preferably 5min.

[0019] In a second aspect, the present invention provides a covalent organic framework membrane prepared according to the preparation method described in the first aspect, which can be used for waste acid recovery and power generation.

[0020] Furthermore, the covalent organic framework membrane that can be used for waste acid recovery and power generation includes: a PES membrane substrate, and a PaTp-TMC membrane formed by forming a PaTp composite layer on the surface of the substrate with Pa and Tp and then modifying it with TMC.

[0021] Furthermore, in the covalent organic framework membrane that can be used for waste acid recovery and power generation, the thickness of the Pa Tp-TMC membrane is 0.7-3.4 μm, preferably 2-2.5 μm, and more preferably 2.4 μm.

[0022] Thirdly, the present invention provides the application of the covalent organic framework membrane described above for waste acid recovery and power generation, including its use in waste acid recovery and power generation.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention provides a covalent organic framework membrane that can be used for waste acid recovery and power generation. It is obtained by interfacial polymerization of p-phenylenediamine and trialdehyde-resorcinol on a substrate surface to form a PaTp composite layer, followed by modification with trimesoyl pyromellitic chloride to obtain a PaTp-TMC membrane. This covalent organic framework membrane exhibits high selectivity and can achieve high efficiency in the recovery of H+. + Its ultra-fast transport and efficient retention of other ions enable it to simultaneously complete two processes: waste acid recovery and power generation (osmotic energy conversion), greatly improving the efficiency of process applications.

[0025] 2. The covalent organic framework membrane of the present invention, applicable to waste acid recovery and power generation, possesses high selectivity due to the sub-nanometer channels of the PaTp-TMC membrane. By modifying PaTp with TMC, the pore size of the resulting covalent organic framework membrane can be further reduced, increasing its affinity for H+. + The binding site, thereby achieving H + Its ultra-fast transport and efficient retention of other ions have great potential in waste acid recovery.

[0026] 3. The covalent organic framework membrane of the present invention, which can be used for waste acid recovery and power generation, is prepared by casting. The process is simple, the conditions are mild, the equipment is simple and easy to operate, it can be prepared over a large area, there is no subsequent chemical treatment, it is green and environmentally friendly, and it can be used for industrial production.

[0027] 4. The covalent organic framework membrane of the present invention, which can be used for waste acid recovery and power generation, does not require heating energy consumption in waste acid recovery compared with traditional waste acid recovery technology. It has low requirements for the membrane's high temperature resistance and chemical corrosion resistance and exhibits excellent durability in the separation process. In the process of permeate energy conversion and collection, the device used is simple, easy to assemble, and the testing method is universal. Attached Figure Description

[0028] Figure 1 This invention relates to a method for preparing covalent organic framework membranes for waste acid recovery and power generation.

[0029] Figure 2 An optical photograph of a covalent organic framework membrane used for waste acid recovery and power generation.

[0030] Figure 3 The infrared spectra of covalent organic framework membranes used for waste acid recovery and power generation are shown in Figure 1. Figure 1a shows the infrared spectra of three monomers, and Figure 1b shows the partial infrared spectra of PaTp / PES and PaTp-TMC / PES membranes.

[0031] Figure 4 SEM images of covalent organic framework membranes of different thicknesses used for waste acid recovery and power generation.

[0032] Figure 5 Schematic diagrams of covalent organic framework structures of different modified monomers used for waste acid recovery and power generation.

[0033] Figure 6 This is a schematic diagram of a permeation experiment used for waste acid recovery; the left side is the feed side, and the right side is the permeation side.

[0034] Figure 7 This is a physical image of an apparatus used for waste acid recovery and power generation.

[0035] Figure 8 The images show the physical samples before and after the simulated waste acid solution recovery and power generation performance test. In the image, a is the raw material of the simulated waste acid solution, b is the original simulated waste acid solution, c is the simulated waste acid solution after filtering out excess precipitate (for subsequent performance testing), and d is the clarified solution after the permeation test.

[0036] Figure 9 The results are for performance tests on waste acid recovery and power generation applications; a) is the output power density measured in a 50-fold simulated waste acid solution; b) is the ion concentration in the permeate side solution measured after 5 hours of permeation following the power generation test; c) is the H2O concentration after the permeation test. + Cu 2+ Permeation and H + / Cu 2+ The choice ratio. Detailed Implementation

[0037] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0038] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0039] Example 1

[0040] A method for preparing a covalent organic framework membrane that can be used for waste acid recovery and power generation (its flowchart is shown below). Figure 1 (As shown), including the following steps:

[0041] (1) Soak the PES membrane in ultrapure water for 24 hours and set aside for later use;

[0042] (2) Dissolve p-phenylenediamine (Pa) in ultrapure water to obtain a 2% solution A. Dissolve trialdehyde phloroglucinol (Tp, 0.05wt%) and the modified monomer trimesoyl chloride (TMC, 0.2wt%) in n-hexane to obtain a 0.05% solution B and a 0.2% solution C.

[0043] (3) 15 mL of solution A was dropped onto the surface of the PES membrane for 30 s to form a Pa layer; then solution B was added and reacted with Pa for 10 s to form a PaTp composite layer; finally solution C was added and reacted with the PaTp composite layer for 30 s to form a PaTp-TMC membrane, and the excess solution was removed.

[0044] (4) After removing excess organic solution, the resulting membrane was cured at 80°C for 5 min to obtain a covalent organic framework membrane, denoted as PaTp-TMC / PES. An optical photograph of the obtained membrane is shown below. Figure 2 It appears as a glossy orange-yellow film.

[0045] The PaTp-TMC / PES obtained in this embodiment was characterized by infrared radiation, and the results are as follows: Figure 3 As shown in the figure, after TMC modification, 1650cm -1 A new peak appeared, which is attributed to the C=O stretching vibration of the amide group, proving the success of the modification.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 1 lies in the different amounts of solutions A, B, and C, as shown in Table 1 below. This resulted in the preparation of PaTp-TMC / PES membranes of varying thicknesses, as illustrated in the SEM images below. Figure 4 As shown.

[0048] Table 1

[0049] Group Volume of solution A, mL Volume of solution B, mL Solution C volume, mL membrane Example 1 15 10 10 <![CDATA[Pa 15 Tp 15 -TMC 10 / PES]]> Comparative Example 1-1 9 6 6 <![CDATA[Pa9Tp6-TMC6 / PES]]> Comparative Examples 1-2 3 2 2 <![CDATA[Pa3Tp2-TMC2 / PES]]>

[0050] Comparative Example 2

[0051] The difference between Comparative Example 2 and Example 1 lies in the different types of modifying monomers. The structural diagram is shown below. Figure 5 As shown in the table below.

[0052] Table 2

[0053] Group Modified monomers membrane Example 1 TMC PaTp-TMC / PES Comparative Example 2-1 terephthaloyl chloride (TPC) PaTp-TPC / PES Comparative Example 2-2 Benzoyl chloride BZC PaTp-BZC / PES Comparative Examples 2-3 \ PaTp / PES

[0054] Test Example 1: Permeation Test

[0055] In a typical experimental procedure, the membrane sealed with sealing film is placed in the center of an H-shaped tank (e.g., ...). Figure 6 The feed solution (1M HCl / KCl solution) and ultrapure water were added to the left and right sides of the tank, respectively. At regular intervals, all ultrapure water from the permeation side (right side) was collected for analysis. Simultaneously, the same volume of ultrapure water as the feed side (left side) was added to the permeation side to maintain continuous permeation. The proton and cation concentrations on the permeation side were measured using a pH meter and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The ion permeation rate (P0) was measured. i ,mol m -2 h -1 The calculation formula is shown in equation (I) below:

[0056] P i =(ΔC×V) / (A×Δt) (I)

[0057] Wherein, ΔC(mol L -1 V(L) is the ion concentration on the osmotic side, V(L) is the effective volume of the solution on the osmotic side, and A(m) is the ion concentration on the osmotic side. 2 ) is the effective infiltration area, and Δt(h) is the infiltration time.

[0058] The various membranes obtained in the above embodiments and comparative examples were tested according to the above method, and the results are shown in Table 3 below.

[0059] Table 3

[0060] Group <![CDATA[H + / K + Selection ratio <![CDATA[H + Osmotic flux (mol m) -2 h -1 )]]> Example 1 451 6.72 Comparative Example 1-1 55 2.40 Comparative Examples 1-2 10 1.15 Comparative Example 2-1 61 3.31 Comparative Example 2-2 3 1.56 Comparative Examples 2-3 1 1.10

[0061] The results showed that the thickness of the PaTp-TMC / PES film in Example 1 was different from that in Comparative Example 1, H+ / K + The selectivity differences were significant, with the PaTp-TMC / PES membrane obtained in Example 1 exhibiting the highest selectivity.

[0062] Compared to Comparative Example 2, the PaTp-TMC / PES membrane obtained in Example 1 exhibits the best performance, maintaining H₂O while possessing high proton flux. + / K + The highest selectivity was observed in the PaTp-TPC / PES membrane, followed by the PaTp-BZC / PES membrane. In contrast, the PaTp-BZC / PES and PaTp / PES membranes exhibited lower selectivity, although the modified PaTp-BZC / PES was slightly superior to the original PaTp / PES. Therefore, selecting the TMC of this invention as the modifying monomer yields membranes with superior selectivity and permeation flux.

[0063] To investigate the effect of HCl / KCl solution concentration, this experiment tested the permeation performance of the PaTp-TMC / PES membrane obtained in Example 1 under different concentrations of HCl / KCl solution systems. The results are shown in Table 4 below.

[0064] Table 4

[0065] HCl / KCl solution concentration (M) <![CDATA[H + / K + Selection ratio <![CDATA[H + Osmotic flux (mol m) -2 h -1 )]]> 1 451 6.72 0.5 478 1.94 0.25 226 0.48 0.1 54 0.13

[0066] The results showed that the proton permeation rate and H2O of the PaTp-TMC / PES membrane were... + / K + The selectivity increases in the HCl / KCl solution concentration range of 0.1M to 0.5M, and continues to increase to 1M. + Permeation flux increased significantly, while the selectivity decreased slightly but remained at a high level. (Combined H) + The results for both permeation flux and selectivity are optimal when the HCl / KCl feed solution concentration is 1M.

[0067] Experiment Example 2: Electrical Experiment

[0068] Transmembrane ion transport characteristics were tested using a Keithley 2450 source meter within a voltage range of -1.0 to 1.0 V. The PaTp-TMC / PES membrane was placed between H-type cells, with a preferred membrane area of ​​3.14 mm². 2 Current-voltage characteristics were recorded using a pair of Ag / AgCl electrodes. Subsequently, IV curves were recorded in electrolytes with specific concentration gradients to obtain osmotic energy output (power density) performance. Power density (P, W / m³) -2 The calculation formula is shown in equation (II) below:

[0069] P = (I 2 ×R) / S (II)

[0070] Where I is the current (A), R is the resistance (Ω), and S is the film area (m²). 2 ).

[0071] To investigate the effect of concentration gradient in the HCl / HCl solution system, this experiment tested the electrical properties of the PaTp-TMC / PES membrane obtained in Example 1 under HCl / HCl solution systems with different concentration gradients. The results are shown in Table 5 below.

[0072] Table 5

[0073] HCl / HCl concentration gradient M / M <![CDATA[Maximum power density (W m -2 )]]> 2 / 0.04 6.64 2 / 0.4 2.32 2 / 0.2 4.97 2 / 0.02 5.63 2 / 0.01 4.82

[0074] The results showed that as the concentration gradient increased from 5 times (2 / 0.4M) to 50 times (2 / 0.04M), the maximum power density gradually increased, reaching a maximum of 6.64 W / m³ at the 50-fold increase. -2 An increase in power density indicates improved permeation energy conversion efficiency. Further increasing the concentration gradient causes the power density to decrease. Therefore, the optimal HCl / HCl concentration is 2 / 0.04M, meaning a proton concentration gradient of 50 times across the permeation tank.

[0075] Experimental Example 3

[0076] The PaTp-TMC / PES membrane obtained in Example 1 was subjected to simulated waste acid solution recovery and power generation performance tests under the preferred concentration gradient of 2 / 0.04M. The specific steps are as follows:

[0077] (1) Preparation of simulated waste acid solution: The simulated waste acid solution was prepared based on the "acid method for copper extraction". Malachite powder (200 mg) was dissolved in H2SO4 (2.5 M, 50 mL) and heated at 70 °C at 500 r / min. -1 Stir at a constant speed for 2 hours. Then, cool the solution to room temperature and filter to remove the precipitate. Collect the filtrate and use it as a waste acid simulation solution;

[0078] (2) Adjust the pH of the original waste acid solution so that the proton concentrations on both sides are 2M / 0.04M;

[0079] (3) The power generation test process was carried out according to the steps in Example 2. A physical diagram of the test device can be found here. Figure 7 ;

[0080] (4) After the power generation test is completed, conduct the permeation experiment according to the steps in the test example (the state changes of the solution system are as follows). Figure 8 ), and calculate the ion permeation rate.

[0081] The performance test results of the covalent organic framework membrane used for waste acid recovery and power generation in this invention are shown below. Figure 9The maximum power density is close to 4.5W / m³. -2 At the same time, it can maintain H + With heavy metal ions (representative Cu) 2+ The high selectivity (selectivity ratio 7516) demonstrates the great application value of this invention in realizing both waste acid recovery and permeation energy power generation.

[0082] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An application of a covalent organic framework membrane for waste acid recovery and power generation, characterized in that, This includes using the covalent organic framework membrane, which can be used for waste acid recovery and power generation, simultaneously for both waste acid recovery and power generation; wherein, The covalent organic framework membrane that can be used for waste acid recovery and power generation includes: a PES membrane substrate, and a PaTp-TMC membrane formed by forming a PaTp composite layer on the surface of the substrate and then modifying it with TMC; the thickness of the PaTp-TMC membrane is 0.5-3.5 μm; The method for preparing the covalent organic framework membrane that can be used for waste acid recovery and power generation includes the following steps: (1) Dissolve Pa in ultrapure water to obtain solution A, and dissolve Tp and TMC in n-hexane to obtain solution B and solution C respectively; The mass fraction of Pa in solution A is 1-3%, the mass fraction of Tp in solution B is 0.01-0.1%, and the mass fraction of TMC in solution C is 0.1-0.3%. (2) Solution A is dropped onto the surface of the PES membrane to form a Pa layer; then solution B is added to react with Pa to form a Pa-Tp composite layer; finally, solution C is added to react with the Pa-Tp composite layer to form a Pa-Tp-TMC membrane, and excess solution is removed. The volume ratio of solution A, solution B, and solution C is (12-18):(7-13):(7-13). (3) Solidification yields a covalent organic framework membrane that can be used for waste acid recovery and power generation, which is stored in ultrapure water.

2. The application according to claim 1, characterized in that, In step (2), the PES membrane is further soaked in ultrapure water before solution A is added, and the soaking time is 12-36 h.

3. The application according to claim 1, characterized in that, In step (2), the residence time of solution A on the surface of the PES membrane is 10-40 s; the reaction time of solution B with Pa is 5-15 s; and the reaction time of solution C with the Pa-Tp composite layer is 10-40 s.

4. The application according to claim 1, characterized in that, In step (3), the curing temperature is 70-90 ℃ and the curing time is 3-7 min.

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