A multi-nanopore pi membrane, its preparation method and application

Abstract

This invention discloses a multi-nanoporous PI membrane, its preparation method, and its applications. The multi-nanoporous PI membrane comprises a PI membrane characterized by: etched multiple dumbbell-shaped nanopores; Azo-G4-DNA and G4-DNA respectively attached to the inner surfaces of the two segments of the aminated PI membrane's dumbbell-shaped nanopores. The preparation method includes: step 1, etching multiple dumbbell-shaped nanopores in the PI membrane; step 2, activating the carboxyl groups of the dumbbell-shaped nanopores in the PI membrane; and step 3, modifying the inner surfaces of the two segments of the dumbbell-shaped nanopores in step 2 with Azo-G4-DNA and G4-DNA respectively. The multi-nanoporous PI membrane of this invention exhibits selectivity for thallium ions, enabling the transport of thallium ions against their concentration gradient under voltage or ultraviolet light stimulation, thus achieving the collection and extraction of thallium.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal treatment technology, and particularly relates to a multi-nanoporous PI membrane, its preparation method and application. Background Technology

[0002] Thallium, a highly dispersed rare metal, has important applications in medicine, chemical industry, optoelectronics, aerospace, and superconducting materials. However, thallium is usually in a dispersed state, existing in sulfur mines along with metals such as iron, lead, and copper, and has no direct commercial value. Thallium is very rare in nature and difficult to enrich. Common technologies for treating thallium-containing wastewater include adsorption, redox precipitation, and ion exchange, but these technologies are difficult to enrich trace amounts of thallium. Therefore, it is crucial to develop a technology to enrich thallium.

[0003] Polymer films irradiated with charged heavy ions, such as polyimide (PI) films and polyethylene terephthalate (PET) films, can be chemically etched to obtain nanopores of various shapes and sizes. These nanopores have wide applications in ion and molecular pump transport and separation, energy conversion, and biosensors. However, achieving high-level intelligent ion transport characteristics remains a huge challenge. Most cation pump research is limited to alkali metals such as lithium, sodium, and potassium, and research on thallium ions is still lacking.

[0004] Chinese patent document CN 116139713A discloses a method for preparing a PI membrane for ion separation, which yields a sub-nanoporous PI membrane with multiple through-holes. The method is simple and practical, and is suitable for monovalent ions (Li... + Na + K + ) and divalent ions (Mg 2+ Ca 2+ The PI membrane exhibits a high ion separation ratio and good separation effect. However, the PI membrane in this patent does not possess Tl. + Due to its separation characteristics, it cannot extract metallic thallium. Summary of the Invention

[0005] To address the problems existing in the prior art, the technical problem to be solved by this invention is to provide a multi-nanoporous PI membrane capable of reverse concentration transport of thallium ions and collecting and extracting thallium substances. This invention also provides a method for preparing this PI membrane and its applications.

[0006] To solve the above technical problems, the following technical solution is adopted:

[0007] The present invention provides a multi-nanoporous PI membrane, comprising a PI membrane etched with multiple dumbbell-shaped nanopores, and Azo-G4-DNA and G4-DNA respectively modifying the inner surfaces of the two segments of the dumbbell-shaped nanopores of the PI membrane.

[0008] This invention also provides a method for preparing a multi-nanoporous PI membrane, comprising the following steps:

[0009] Step 1: Etch multiple dumbbell-shaped nanopores in the PI film.

[0010] The PI membrane, after being irradiated with heavy ions, was then irradiated with ultraviolet light on both sides. The PI membrane was then sandwiched in the middle of an H-type electrolytic cell. Under constant temperature water bath conditions, etching solution was added to both chambers of the H-type electrolytic cell, and platinum electrodes were inserted on both the left and right sides. A constant voltage of 1.0V was applied, and the output current was observed. After the current suddenly increased and was maintained for a period of time, the pressure was stopped, and the etching solution was poured out. Stop solution was added to both sides, and a constant voltage of 1.0V was continued to be applied and maintained for an appropriate time before stopping. The stop solution was poured out, and the PI membrane in the middle of the H-type electrolytic cell was removed and rinsed with distilled water to obtain multiple dumbbell-shaped nanoporous PI membranes.

[0011] Step 2: Carboxyl activation of the dumbbell-shaped nanopores in the PI membrane.

[0012] A PI membrane with multiple dumbbell-shaped nanopores was immersed in a mixed solution of EDC and NHSS to activate the carboxyl groups.

[0013] Step 3: Modify the inner surfaces of the two segments of the dumbbell-shaped nanopores in the PI membrane from Step 2 with Azo-G4-DNA and G4-DNA, respectively.

[0014] The activated PI membrane was fixed in the middle of an H-type electrolytic cell. The left and right chambers were respectively contacted with Azo-G4-DNA and G4-DNA solutions for at least 12 hours in the absence of light. Then the PI membrane was removed and washed to obtain a multi-nanoporous PI membrane with the dumbbell-shaped nanopores modified by Azo-G4-DNA and G4-DNA biomolecules.

[0015] The present invention also provides a multi-nanoporous PI membrane for reverse concentration transport of thallium ions under a 60-fold concentration difference.

[0016] The technical effects of this invention are:

[0017] The multi-nanoporous PI membrane of the present invention is selective for thallium ions and can achieve the transport of thallium ions against the concentration gradient under voltage or ultraviolet light stimulation, thereby realizing the collection and extraction of thallium substances. Attached Figure Description

[0018] The accompanying drawings of this invention are described below:

[0019] Figure 1 This is a schematic diagram of the H-type electrolytic cell.

[0020] Figure 2 This is a scanning electron microscope image of the PI film surface after etching.

[0021] Figure 3 This is a scanning electron microscope image of the modified PI film surface;

[0022] Figure 4 A schematic diagram of the structure of dumbbell-shaped nanopores modified with two biomolecules;

[0023] Figure 5 The current generated by three concentration differences under different illumination conditions;

[0024] Figure 6 The waveform of the current generated by a 10-fold concentration difference under fluctuating voltage. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0026] Example: Preparation of a multi-nanoporous PI membrane for reverse concentration transport of thallium ions

[0027] Step 1: Etch multiple dumbbell-shaped nanopores in the PI film.

[0028] After being irradiated with a heavy ion density of 10 7 pcs / cm 2 The irradiated PI film was subjected to ultraviolet light (365nm, 2500mW / cm²) on both sides. 2 Irradiate for 60 minutes; then clamp the PI membrane in the middle of the polytetrafluoroethylene H-type electrolytic cell, as follows. Figure 1 As shown, the H-type electrolytic cell includes a left chamber, a right chamber, and a PI membrane sandwiched at the central connecting port. Under constant temperature water bath conditions of 50℃, etching solution (13% NaClO by mass) was added to both chambers of the H-type electrolytic cell. Platinum electrodes were inserted on both the left and right sides. A constant voltage of 1.0V was applied using a CHI 660 electrochemical workstation, and the output current was observed. When the current suddenly increased, the etching time was maintained for another 60 minutes before the pressure was stopped and the etching solution was poured out. Stop solution (1.0 mol / L KI) was added to both sides, and a constant voltage of 1.0V was applied for another 30 minutes before stopping. The stop solution was then poured out, and the PI membrane in the middle of the H-type electrolytic cell was removed. After rinsing 3-5 times with distilled water, it was soaked in distilled water for later use, resulting in multiple dumbbell-shaped nanoporous PI membranes, as shown... Figure 2 As shown, the PI film surface has multiple nanopores.

[0029] Step 2: Carboxyl activation of the dumbbell-shaped nanopores in the PI membrane.

[0030] A PI membrane with multiple dumbbell-shaped nanopores was immersed in a mixed solution of carbodiimide (EDC, 15 g / L) and N-hydroxysuccinimide (NHSS, 3 g / L) for 60 min to activate the carboxyl groups.

[0031] Step 3: Modify the inner surfaces of the two segments of the dumbbell-shaped nanopores in the PI membrane from Step 2 with Azo-G4-DNA and G4-DNA, respectively.

[0032] G-tetramers are G-base-rich DNA strands (abbreviated G4-DNA) characterized by structural and functional diversity. The central structure of a G-tetramer contains a hollow chamber that is sensitive to Tl... + It possesses specific recognition capabilities and strong affinity. The G4 sequence used in this patent is 5′-G TGG GTA GGG CGG GTT GG-3′ [see the literature "Functional Nucleic Acid Probe for Parallel Monitoring K"]. + and Protoporphyrin IX in Living Organism”, Cheng et al., Analytical Chemistry, 2016, 88(5) (“Functional nucleic acid probes for parallel monitoring of K+ and protoporphyrin IX in living organisms”, Cheng et al., Analytical Chemistry, 2016, 88(5)). Azobenzene (Azo) is an organic molecule sensitive to ultraviolet and visible light and is widely used in photostimulation responses such as small molecule transmembrane transport and ion selective separation. In this step, Azo is modified into the middle of the above G4-rich DNA strand (5′-GTGGGTAGG-Azo-GCGGGTTGG-3′) to construct an Azo-G4-DNA photoresponsive thallium ion transport gating switch.

[0033] The activated PI membrane was fixed in the middle of an H-type electrolytic cell (without electrodes). The left and right chambers were respectively contacted with 10 μmol / L Azo-G4-DNA and G4-DNA solutions for 12 hours in the absence of light. Then the PI membrane was removed and washed to obtain a multi-nanoporous PI membrane with the dumbbell-shaped nanopores modified by Azo-G4-DNA and G4-DNA biomolecules.

[0034] Scanning electron microscopy of the modified PI film surface as follows Figure 3 As shown, Figure 4 The structure of dumbbell-shaped nanopores modified with two biomolecules is shown. The pores on the left side of the PI membrane immobilize Azo-G4-DNA, and the pores on the right side of the PI membrane immobilize G4-DNA.

[0035] Performance testing of multi-nanoporous PI membranes of the present invention

[0036] To investigate the performance of the prepared dumbbell-shaped multi-nanoporous PI membrane under different illumination conditions, the modified dumbbell-shaped multi-nanoporous PI membrane was fixed in the middle of an H-type electrolytic cell, with the Azo-G4-DNA modified surface corresponding to the left chamber and the G4-DNA modified surface corresponding to the right chamber. Platinum electrodes were inserted on both the left and right sides. Low and high concentrations of thallium nitrate solutions were added to the left and right chambers, respectively. After reacting for 3 hours, the Tl values ​​in the left and right chambers were measured by inductively coupled plasma atomic absorption spectrometry (ICP-AES). + After the concentration stabilizes, the current obtained across the electrodes is read using a Keithley 6487 ammeter, and the following six tests are performed:

[0037] Scenario 1: In the absence of light, with a 10-fold concentration gradient (C 左 =1 μmol / L, C 右 At a concentration of 10 μmol / L, the Tl in the left chamber after the reaction + The concentration was 4.59 μmol / L, and the measured steady-state current reading was 4.86 nA. The positive bias of the ammeter indicates the presence of Tl. + Ions diffuse and transport from the high concentration side to the low concentration side.

[0038] Case 2: Irradiation of the low-concentration PI film with ultraviolet light (wavelength 320nm, power 12W) for 3 hours, followed by a 10-fold concentration gradient (C 左 =1 μmol / L, C 右 =10μmol / L) at 3h, Tl in the left chamber + At a concentration of 0.02 μmol / L, the measured steady-state current reading was -8.39 nA. The negative bias of the ammeter indicates the presence of Tl. + The diffusion transport of ions is canceled out, and Tl + Ions are transported from the low concentration side to the high concentration side, and then under continuous irradiation with visible light (wavelength 450nm, power 12W), the current gradually recovers to the magnitude of case 1.

[0039] Scenario 3: In the absence of light, with a 50-fold concentration gradient (C 左 =1 μmol / L, C 右 At 50 μmol / L, Tl in the left chamber after the reaction + The concentration was 29.99 μmol / L, and the measured steady-state current reading was 12.8 nA. The positive bias of the ammeter indicates the presence of Tl. + Ions diffuse from the high concentration side to the low concentration side, and the current generated is greater than that of diffusion transport under a 10-fold concentration gradient (Case 1).

[0040] Case 4: Irradiation of the low-concentration PI film with ultraviolet light (wavelength 320nm, power 12W) for 3 hours, followed by a 50-fold concentration gradient (C 左 =1 μmol / L, C右 =50μmol / L) at 3h, Tl in the left chamber + With a concentration of 0.21 μmol / L, the measured steady-state current reading was -1.91 nA. The negative bias of the ammeter indicates the presence of Tl. + Ion diffusion transport is canceled out, and Tl + Ions are transported from low concentration to high concentration, but the current generated is smaller than that generated by reverse transport under a 10-fold concentration gradient (case 2). Then, under continuous irradiation with visible light (wavelength 450nm, power 12W), the current gradually recovers to the size of case 3.

[0041] Case 5: In the absence of light, with a 100-fold concentration gradient (C 左 =1 μmol / L, C 右 At a concentration of 100 μmol / L, the Tl in the left chamber after the reaction + The concentration was 45.03 μmol / L, and the measured steady-state current reading was 21.21 nA. The positive bias of the ammeter indicates the presence of Tl. + Ions diffuse from high concentration to low concentration and generate a larger current than those generated by diffusion transport under concentration gradients of 10 times (case 1) and 50 times (case 3).

[0042] Case 6: Irradiation of the low-concentration PI film with ultraviolet light (wavelength 320nm, power 12W) for 3 hours, followed by a 100-fold concentration gradient (C 左 =1 μmol / L, C 右 =100μmol / L) at 3h, Tl in the left chamber + The concentration was 5.26 μmol / L, and the measured steady-state current reading was 6.52 nA, indicating the presence of Tl. + Ions diffuse from the high concentration to the low concentration side, but the current generated is less than that under no light conditions, indicating that there is still transport against the concentration gradient. However, the ion current generated against the concentration gradient is insufficient to offset the current generated by the diffusion transport under the concentration gradient. Then, under continuous irradiation with visible light (wavelength 450nm, power 12W), the diffusion current gradually returns to state 5.

[0043] The performance of the multi-nanoporous PI membrane of the present invention is shown in Table 1:

[0044] Table 1. Tl of PI film under different conditions + Ion transport performance

[0045]

[0046] The above experiments demonstrate that under ultraviolet light irradiation, dumbbell-shaped multi-nanoporous PI membranes modified on both sides of Azo-G4-DNA and G4-DNA exhibit thallium ion pumping, i.e. thallium ions are transported against the concentration gradient. When the PI membrane on the low concentration side is irradiated with ultraviolet light, a reverse current is generated, indicating that the diffusion transport of thallium ions along the initial concentration gradient direction is weakened.

[0047] Figure 5 The current generated under different light conditions represents three concentration differences: 10 times, 50 times, and 100 times. It can be seen that under ultraviolet light irradiation, the current reaches zero when the concentration difference is between 60 and 70 times. This indicates that when the concentration difference is between 10 and 70 times, the current is zero. + The concentration is 1 μmol / L, and the right side Tl + When the concentration is less than 60 μmol / L, thallium ions will be transported against the concentration gradient, and the right-hand side Tl will be affected. + When the concentration is greater than 70 μmol / L, under ultraviolet light irradiation at a wavelength of 320 nm and a power of 12 W, the ion current generated against the concentration gradient is insufficient to offset the current generated by concentration gradient diffusion transport. Thallium ions in the channel still primarily diffuse down the concentration gradient. Furthermore, under no light and visible light irradiation, Tl... + The ion transport states are similar.

[0048] Performance of multi-nanoporous PI membranes under fluctuating voltage

[0049] The modified dumbbell-shaped multi-nanoporous PI membrane was fixed in the middle of an H-type electrolytic cell, with the Azo-G4-DNA modified surface corresponding to the left chamber and the G4-DNA modified surface corresponding to the right chamber. Thallium nitrate solutions of 1 μmol / L and 10 μmol / L were added to the left and right chambers, respectively. Under no light illumination, platinum electrodes were inserted on both the left and right sides, and a periodically varying voltage from -1V to +1V was applied. The change in current generated under this fluctuating electric field over time was observed. Figure 6 As shown, under an oscillating electric field with a mean of zero, an average current of -9.73 nA can be observed for a concentration difference of 10 times. This indicates that under a periodically varying voltage stimulus from -1V to +1V, Tl + Ions also have a net flow in the opposite direction of concentration.

Claims

1. A method for preparing a multi-nanoporous PI membrane, characterized in that, Includes the following steps: Step 1: Etch multiple dumbbell-shaped nanopores in the PI film. The PI membrane, after being irradiated with heavy ions, was then irradiated with ultraviolet light on both sides. The PI membrane was then sandwiched in the middle of an H-type electrolytic cell. Under constant temperature water bath conditions, etching solution was added to both chambers of the H-type electrolytic cell, and platinum electrodes were inserted on both the left and right sides. A constant voltage of 1.0 V was applied, and the output current was observed. After the current suddenly increased and was maintained for a period of time, the pressure was stopped, and the etching solution was poured out. Stop solution was added to both sides, and a constant voltage of 1.0 V was continued to be applied and maintained for an appropriate time before stopping. The stop solution was poured out, and the PI membrane in the middle of the H-type electrolytic cell was removed and rinsed with distilled water to obtain multiple dumbbell-shaped nanoporous PI membranes. Step 2: Carboxyl activation of the dumbbell-shaped nanopores in the PI membrane. A PI membrane with multiple dumbbell-shaped nanopores was immersed in a mixed solution of carbodiimide and N-hydroxysuccinimide to activate the carboxyl groups. Step 3: Modify the inner surfaces of the two segments of the dumbbell-shaped nanopores in the PI membrane from Step 2 with Azo-G4-DNA and G4-DNA, respectively. The activated PI membrane was fixed in the middle of an H-type electrolytic cell. The left and right chambers were respectively contacted with Azo-G4-DNA and G4-DNA solutions for at least 12 hours in the absence of light. Then the PI membrane was removed and washed to obtain a multi-nanoporous PI membrane with the dumbbell-shaped nanopores modified by Azo-G4-DNA and G4-DNA biomolecules.

2. The method for preparing a multi-nanoporous PI membrane according to claim 1, characterized in that, in In step 1, the heavy ion irradiation density is 10. 7 pcs / cm 2 Ultraviolet light wavelength 365 nm, irradiance 2500 mW / cm 2 Irradiation time should be at least 60 minutes.

3. The method for preparing a multi-nanoporous PI membrane according to claim 1, characterized in that, In step 1, the etching solution is a NaClO solution; the stopping solution is a KI solution.

4. The method for preparing a multi-nanoporous PI membrane according to claim 3, characterized in that: In the NaClO solution, the mass fraction of NaClO is 13%; in the KI solution, the concentration of KI is 1.0 mol / L; after the current suddenly increases, the etching time is maintained for a total of not less than 60 min; after adding the stop solution and applying a constant voltage of 1.0V, the total holding time is at least 30 min.

5. The method for preparing a multi-nanoporous PI membrane according to any one of claims 1 to 4, characterized in that, In step 2, the mixed solution contains 15 g / L of carbodiimide and 3 g / L of N-hydroxysuccinimide, and the PI membrane with multiple dumbbell-shaped nanopores is immersed for at least 60 min.

6. The method for preparing a multi-nanoporous PI membrane according to claim 5, characterized in that, In step 3, both the Azo-G4-DNA and G4-DNA solutions were 10 μmol / L.

7. A multi-nanoporous PI membrane prepared by the method of any one of claims 1-6, characterized in that: The PI film is etched with multiple dumbbell-shaped nanopores, and Azo-G4-DNA and G4-DNA are respectively used to modify the two inner surfaces of the dumbbell-shaped nanopores of the PI film.

8. An application of the multi-nanoporous PI membrane of claim 7 in reverse concentration transport of thallium ions under a 60-fold concentration difference.

9. The application of the multi-nanoporous PI membrane according to claim 8, characterized in that: The Azo-G4-DNA modified surface of the low-concentration side PI membrane was irradiated with ultraviolet light.

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