A method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane and its application

Abstract

This invention relates to a method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane and its application. The invention aims to address the technical problem that existing polymer thin films struggle to simultaneously increase permeate flux while improving retention rate. This invention provides a nanofiltration membrane with high efficiency in separating cobalt and lithium ions and significantly enhanced permeate flux. It achieves this by doping p-aminobenzenesulfonic acid during the preparation of traditional TFC nanofiltration membranes, efficiently introducing sulfonic acid groups to promote the formation of an ordered nanochannel structure in the polyamide network, thereby increasing water flux. Simultaneously, the negative charge carried by the sulfonic acid groups enhances the overall electronegativity of the membrane, making it more effective against Co ions. 2+ The electrostatic adsorption capacity is significantly higher than that of Li + This enables efficient separation of cobalt and lithium ions. The nanofiltration membrane material provided by this invention can be widely used in the resource-based treatment of acid leaching wastewater from lithium cobalt oxide batteries, achieving efficient separation and recovery of cobalt and lithium, and improving economic benefits and resource utilization.

Description

Technical Field

[0001] This invention relates to a method for preparing a nanofiltration membrane that improves the separation performance of cobalt and lithium, and its application. Background Technology

[0002] Cobalt and lithium, as two core strategic metals, are widely used in lithium-ion batteries for electric vehicles, electronic devices, and energy storage. They often coexist in the cathode materials of spent lithium-ion batteries, making effective separation crucial during recycling. It is predicted that by 2050, global demand for cobalt will surge several times over, and demand for lithium will also increase significantly. This surge in demand stems from the booming electric vehicle industry, the widespread adoption of electronic devices, and the increasing demand for energy storage. With the rapid consumption of these devices, coupled with the lack of responsibility among some users, a large amount of resources are being wasted. These water-containing waste streams hold enormous potential for cobalt and lithium recycling, offering the possibility of resource reuse. Therefore, the global recycling of these strategic metals and wastewater treatment are not only necessary for practicing the circular economy concept but also key to protecting natural resources and minimizing environmental burden.

[0003] Currently, membrane separation technology, due to its lack of phase change processes, has relatively low energy consumption, significantly reducing energy consumption and carbon emissions compared to traditional separation methods. Nanofiltration membranes, in particular, possess excellent ion selectivity, allowing for the retention or permeation of specific ions by adjusting pore size and charge properties according to actual needs. Therefore, they are widely used in municipal water supply, wastewater treatment, food and beverage processing, and pharmaceutical manufacturing. Meanwhile, interfacial polymerization, due to its simple and inexpensive process for preparing polyamide films and its ability to produce high-performance films, has become the mainstream method for nanofiltration membrane preparation worldwide. Although TFC membranes (polyamide nanofiltration membranes) prepared by interfacial polymerization have made some progress, they still face common problems associated with traditional polyamide membranes, such as insufficient hydrophilicity, poor permeability, low retention efficiency, poor thermal stability, and susceptibility to fouling. Therefore, developing nanofiltration membranes with both high permeability and high selectivity has become a current research hotspot and challenge. Summary of the Invention

[0004] The present invention aims to solve the technical problem that existing polymer films are difficult to improve permeation flux while increasing the rejection rate of the membrane, and provides a method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane and its application.

[0005] The method for preparing the p-aminobenzenesulfonic acid blended nanofiltration membrane of the present invention is carried out according to the following steps:

[0006] 1. Mix p-aminobenzenesulfonic acid and piperazine in water to obtain a mixed aqueous solution;

[0007] The concentration of PIP (piperazine) in the blended aqueous solution is 10 g / L to 18 g / L, and the concentration of p-aminobenzenesulfonic acid is 0.5 g / L to 5.5 g / L.

[0008] 2. Clean the polyethersulfone membrane with anhydrous ethanol and then dry it; then immerse the dried polyethersulfone membrane in the blend solution prepared in step 1 for 1 min to 3 min, pour out the liquid, and let the membrane dry naturally in the air to obtain a PIP saturated membrane.

[0009] 3. Immerse the PIP saturated membrane prepared in step 2 into a hexane solution of TMC (trimethylammonium chloride) for 20s to 100s to induce interfacial polymerization. Pour out the liquid and then place the membrane in a drying oven for heat treatment for 23min to 27min at a temperature of 50℃ to 70℃ to obtain a p-aminobenzenesulfonic acid blended nanofiltration membrane.

[0010] The concentration of the hexane solution of the TMC is 0.2 g / L to 1.5 g / L.

[0011] The p-aminobenzenesulfonic acid blended nanofiltration membrane prepared by this invention is used to selectively separate cobalt and lithium ions in acid leaching wastewater from lithium cobalt oxide batteries. The specific method is as follows: the pH of the acid leaching wastewater from lithium cobalt oxide batteries is adjusted to 1-2, and then filtered through the p-aminobenzenesulfonic acid blended nanofiltration membrane to selectively separate cobalt and lithium ions.

[0012] The p-aminobenzenesulfonic acid blended nanofiltration membrane prepared by this invention breaks the trade-off effect between the permeability and rejection rate of traditional polymer membranes, while achieving a high cobalt-lithium separation efficiency.

[0013] Retention rate, separation factor, and water flux are three important parameters for evaluating nanofiltration membranes. The performance of this invention is evaluated using retention rate, separation factor, and water flux.

[0014] Retention rate R (%) is defined as: the concentration (C0) of a specific substance in the feed solution under certain operating conditions. p ) and concentration in the permeate (C f The percentage of the difference between the concentrations in the feed solution and the concentration in the feed solution:

[0015]

[0016] Separation factor S Co,Li Defined as: under certain operating conditions, the Li in the permeate + ion concentration (C Li,p ) and Co in the permeate 2+ ion concentration (C Co,p The ratio of ) to Li in the raw material solution + ion concentration (C Li,f) and Co in the raw material liquid 2+ ion concentration (C Co,f The ratio of ) to:

[0017]

[0018] Water flux is defined as the volume of water passing through a unit membrane area per unit time under certain operating conditions. The unit used in this invention is L / (m²). 2 ·h).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention modifies the TFC membrane by doping it with p-aminobenzenesulfonic acid during the preparation of a traditional TFC composite membrane. By comparing the molecular configurations of p-aminobenzenesulfonic acid, o-aminobenzenesulfonic acid, and m-aminobenzenesulfonic acid, it was found that p-aminobenzenesulfonic acid exhibits superior reactivity in interfacial polymerization due to its smaller steric hindrance effect. The efficient introduction of its sulfonic acid groups (-SOH) promotes the formation of an ordered nanochannel structure in the polyamide network. The hydrophilic sulfonic acid groups increase the membrane flux, thereby regulating the filtration rate of pure water permeation. Simultaneously, the negative charge of the sulfonic acid groups enhances the electronegativity of the entire membrane, thus improving its resistance to Co. 2+ Its repulsion ability is significantly higher than that of Li + This enables selective separation, ultimately affecting the membrane's permeation of water in wastewater and the separation of metal ions.

[0021] This invention utilizes an optimized low-monomer concentration PIP blend with p-aminobenzenesulfonic acid and TMC to form a thin polyamide selective layer on the surface of a polyethersulfone support layer, achieving excellent nanofiltration thickness. The introduction of sulfonic acid groups from p-aminobenzenesulfonic acid significantly enhances the membrane's water flux and enrichment rate. The nanofiltration membrane prepared by this invention exhibits superior permeability and retention compared to traditional TFC membranes, and possesses the hydrophilicity, antibacterial properties, and thermal stability of nanofiltration materials. It can be widely used for the separation of various salts. Furthermore, this membrane has been applied for the first time to treat acid leaching wastewater from lithium cobalt oxide battery cathode materials. It achieves maximum retention rates of 7.25% for monovalent lithium ions and 100% for divalent cobalt ions, with a separation factor of 477.2, demonstrating extremely high selectivity and achieving ultra-high separation efficiency for both cobalt and lithium ions. It effectively retains Co in the wastewater. 2+ This also increases the pure water permeation flux of the membrane, with a maximum water flux of 12.52 L / (m²) at a pressure of 2 bar. 2 ·h). Attached Figure Description

[0022] Figure 1 The structural formulas of o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid and p-aminobenzenesulfonic acid are shown.

[0023] Figure 2 This is a graph of the data in Table 1;

[0024] Figure 3 This is a data graph for Table 2. Detailed Implementation

[0025] Specific Implementation Method 1: This implementation method is a method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane, specifically carried out according to the following steps:

[0026] 1. Mix p-aminobenzenesulfonic acid and piperazine in water to obtain a mixed aqueous solution;

[0027] The concentration of PIP in the blended aqueous solution is 10 g / L to 18 g / L, and the concentration of p-aminobenzenesulfonic acid is 0.5 g / L to 5.5 g / L.

[0028] 2. Clean the polyethersulfone membrane with anhydrous ethanol and then dry it; then immerse the dried polyethersulfone membrane in the blend solution prepared in step 1 for 1 min to 3 min, pour out the liquid, and let the membrane dry naturally in the air to obtain a PIP saturated membrane.

[0029] 3. Immerse the PIP saturated membrane prepared in step 2 into the hexane solution of TMC for 20s to 100s to carry out the interfacial polymerization reaction, pour out the liquid, and then place the membrane in a drying oven for heat treatment for 23min to 27min at a temperature of 50℃ to 70℃ to produce a p-aminobenzenesulfonic acid blended nanofiltration membrane.

[0030] The concentration of the hexane solution of the TMC is 0.2 g / L to 1.5 g / L.

[0031] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mixing method in step one involves simultaneous ultrasonication and stirring for 5 to 10 minutes. Everything else is the same as in Specific Implementation Method One.

[0032] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the frequency of the ultrasound in step one is 30kHz to 40kHz. Everything else is the same as in Specific Implementation Method 2.

[0033] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the specific process of cleaning the polyethersulfone membrane with anhydrous ethanol and then drying it in step two is as follows: the polyethersulfone membrane is soaked in anhydrous ethanol for 2 to 3 hours to remove surface impurities and improve the hydrophilicity of the polyethersulfone membrane surface, and then dried at 60°C for 10 minutes. Everything else is the same as in Specific Implementation Methods One to Three.

[0034] Specific Implementation Method 5: This implementation method is an application of the p-aminobenzenesulfonic acid blended nanofiltration membrane in Specific Implementation Method 1, specifically applied to the selective separation of cobalt and lithium ions in acid leaching wastewater from lithium cobalt oxide batteries.

[0035] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the specific method for selectively retaining cobalt elements in the acid leaching wastewater from lithium cobalt oxide batteries is as follows: the pH of the acid leaching wastewater from lithium cobalt oxide batteries is adjusted to 1-2, and then filtered through the aforementioned p-aminobenzenesulfonic acid blended nanofiltration membrane to selectively separate cobalt and lithium ions. Everything else is the same as in Specific Implementation Method Five.

[0036] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the metal ions in the acid leaching wastewater of the lithium cobalt oxide battery cathode material are Li... + and Co 2+ And Li + The concentration is 50 mg / L to 100 mg / L, Co 2+ The concentration is 100 mg / L to 300 mg / L. Everything else is the same as in Specific Implementation Method Six.

[0037] The invention was verified using the following experiments:

[0038] Experiment 1: This experiment demonstrates a method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane, specifically carried out according to the following steps:

[0039] 1. Mix p-aminobenzenesulfonic acid and piperazine in water by ultrasonication and stirring for 10 minutes at a frequency of 35 kHz to obtain a mixed aqueous solution.

[0040] The concentration of PIP in the blended aqueous solution is 17.5 g / L, and the concentration of p-aminobenzenesulfonic acid is 0.875 g / L.

[0041] 2. Soak the polyethersulfone membrane in anhydrous ethanol for 2 hours to remove surface impurities and improve the hydrophilicity of the polyethersulfone membrane surface. Then dry it at 60°C for 10 minutes. Then immerse the dried polyethersulfone membrane in the blend solution prepared in step 1 for 2 minutes, pour out the liquid, and let the film dry naturally in the air to obtain a PIP saturated membrane.

[0042] 3. Immerse the PIP saturated membrane prepared in step 2 into the hexane solution of TMC for 60 seconds to carry out interfacial polymerization reaction. Pour out the liquid, and then place the membrane in a drying oven for heat treatment for 25 minutes at a temperature of 60°C to obtain the p-aminobenzenesulfonic acid blended nanofiltration membrane, denoted as M-1.

[0043] The concentration of the hexane solution of the TMC is 1.75 g / L.

[0044] Experiment 2: This experiment differs from Experiment 1 in that the concentration of p-aminobenzenesulfonic acid mentioned in step one is 1.75 g / L. Everything else is the same as in Experiment 1. The final nanofiltration membrane is designated M-2.

[0045] Experiment 3: This experiment differs from Experiment 1 in that the concentration of p-aminobenzenesulfonic acid mentioned in step one is 3.5 g / L. Everything else is the same as in Experiment 1. The final nanofiltration membrane is designated M-3.

[0046] Experiment 4: This experiment differs from Experiment 1 in that the concentration of p-aminobenzenesulfonic acid mentioned in step one is 4.375 g / L. Everything else is the same as in Experiment 1. The final nanofiltration membrane is designated M-4.

[0047] Experiment 5: This experiment differs from Experiment 1 in that the concentration of p-aminobenzenesulfonic acid mentioned in step one is 5.25 g / L. Everything else is the same as in Experiment 1. The final nanofiltration membrane is designated M-5.

[0048] Comparative Example 1: This experiment differs from Experiment 1 in that p-aminobenzenesulfonic acid was not added in step one. Everything else was the same as Experiment 1. The final nanofiltration membrane was denoted as M-0.

[0049] Comparative Example 2: This experiment differs from Experiment 1 in that o-aminobenzenesulfonic acid at a concentration of 1.75 g / L was added in step one. Everything else was the same as in Experiment 1. The final nanofiltration membrane was designated M-6.

[0050] Comparative Example 3: This experiment differs from Experiment 1 in that m-aminobenzenesulfonic acid at a concentration of 2.625 g / L was added in step one. Everything else was the same as in Experiment 1. The final nanofiltration membrane was designated M-7.

[0051] Application Example 1:

[0052] The nanofiltration membranes prepared in Experiment 1 to Comparative Example 3 were fixed in ultrafiltration cups. 30 mL of deionized water was added to the ultrafiltration cups, and after sealing, an air compressor and the ultrafiltration cups were connected. The membranes were used for the first time to pre-compress them at a pressure of 2 bar. After pre-compressing, the volume of liquid permeating through the membrane per unit time was measured using a stopwatch and a graduated cylinder. The water flux was calculated using the following formula:

[0053]

[0054] In the formula: J is the flux L / (m 2 ·h), T is the test time (h), V is the volume of aqueous solution permeating the membrane during time T (L), and A is the effective membrane area (m²). 2 ).

[0055] The pure water flux of each nanofiltration membrane at 2 bar pressure can be calculated using the above formula. The specific results are shown in Table 1.

[0056] Application Example 2: Prepare Li solutions with an initial concentration of 0.55 g / L. + Aqueous solution and 4 g / L Co 2+ Take 5 mL of each of the above aqueous solutions and mix them in a 100 mL volumetric flask. Make up to volume with deionized water and adjust the pH to 1.6 with hydrochloric acid. Then add 20 mL of the above mixed solution to an ultrafiltration cup, seal it, and connect an air compressor and the ultrafiltration cup. Filter the mixed solution through nanofiltration membranes prepared in Experiment 1 to Comparative Example 1 at a pressure of 2 bar. Take the feed solution and permeate, filter them through a 0.22 μm filter. Take one portion each of the filtered feed solution and permeate, add 1% concentrated nitric acid, and then dilute 100 times with ultrapure water. Detect the Co content using a flame atomic absorption spectrophotometer. 2+ and Li + The concentration of the nanofiltration membrane. Retention rate and separation factor are two important parameters for evaluating the separation performance of nanofiltration membranes.

[0057]

[0058] In the formula: R is the retention rate (%), C p C represents the concentration of ions in the feed solution (mg / L). f The concentration of ions in the permeate (mg / L).

[0059] Based on the above formula, the amount of Li in the feed liquid can be calculated. + The solution concentration was 27.5 mg / L, Co 2+ At a solution concentration of 200 mg / L, the p-aminobenzenesulfonic acid blended nanofiltration membrane exhibits good adhesion to Co at a pressure of 2 bar. 2+ and Li + The retention performance is shown in Table 1.

[0060] Table 1 Nanofiltration Membrane Performance

[0061]

[0062] Table 1 shows that the addition of p-aminobenzenesulfonic acid promotes the pure water flux and retention performance of the nanofiltration membrane, with the highest pure water flux reaching 15.78 L / (m²). 2 h), but the separation performance is poor at this time. When the pure water flux reaches 10.74 L / (m 2 At time h) (M-3), the separation effect reaches its optimal level, effectively retaining Co in the wastewater. 2+ At the same time, for Li +The retention rate was kept below 5%. Comparing the effects of adding o-aminobenzenesulfonic acid and m-aminobenzenesulfonic acid, it was found that p-aminobenzenesulfonic acid, due to its smaller molecular steric hindrance, can more effectively embed into the interfacial polymerization reaction system, thereby significantly improving the water flux performance of the composite membrane. At the same time, p-aminobenzenesulfonic acid exhibits the best embedding ability during interfacial polymerization, thus significantly improving the separation performance of the blend membrane. Figure 2 The data in Table 1 is plotted.

[0063]

[0064] In the above formula, S Co,Li For membrane to Co 2+ and Li + The separation factor, C Li,f For Li in the raw material solution + The ion concentration, C Co,f Co in the raw material solution 2+ The ion concentration, C Li,p Li in the permeate + ion concentration, C Co,p Co in the permeate 2+ The ion concentration of Li in the feed solution can be calculated using the above formula. + The concentration was 27.5 mg / L, Co 2+ At a concentration of 200 mg / L, the p-aminobenzenesulfonic acid blended nanofiltration membrane exhibits good performance against Co at a pressure of 2 bar. 2+ and Li + The separation performance is shown in Table 2.

[0065] Table 2. Effects of nanofiltration membranes on Co 2+ and Li + Separation factor

[0066]

[0067] Table 2 shows that the addition of p-aminobenzenesulfonic acid promotes the separation performance of nanofiltration membranes. The nanofiltration membrane M-3, with the highest separation performance, shows a positive effect on Li... + and Co 2+ With a maximum separation factor of 477.2, it exhibits extremely high selectivity, achieving high separation of cobalt and lithium elements, thus laying a solid foundation for subsequent recycling. Figure 3 This is a data graph for Table 2.

Claims

1. A method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane, characterized in that... The preparation method of the p-aminobenzenesulfonic acid blended nanofiltration membrane is carried out according to the following steps:

1. Mix p-aminobenzenesulfonic acid and piperazine in water to obtain a mixed aqueous solution; The concentration of piperazine in the blended aqueous solution is 10 g / L to 18 g / L, and the concentration of p-aminobenzenesulfonic acid is 0.5 g / L to 5.5 g / L.

2. Clean the polyethersulfone membrane with anhydrous ethanol and then dry it; then immerse the dried polyethersulfone membrane in the blend solution prepared in step 1 for 1 min to 3 min, pour out the liquid, and let the membrane dry naturally in the air to obtain a PIP saturated membrane.

3. Immerse the PIP saturated membrane prepared in step 2 into the hexane solution of TMC for 20s~100s to carry out the interfacial polymerization reaction, pour out the liquid, and then place the membrane in a drying oven for heat treatment for 23min~27min at a temperature of 50℃~70℃ to obtain the p-aminobenzenesulfonic acid blended nanofiltration membrane. The concentration of the hexane solution of the TMC is 0.2 g / L to 1.5 g / L.

2. The method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane according to claim 1, characterized in that... The mixing method in step one is to perform ultrasonication and stirring simultaneously for 5 to 10 minutes.

3. The method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane according to claim 2, characterized in that... The frequency of ultrasound in step one is 30kHz~40kHz.

4. The method for preparing a p-aminobenzenesulfonic acid blended nanofiltration membrane according to claim 1, characterized in that... The specific process of cleaning the polyethersulfone membrane with anhydrous ethanol and then drying it in step two is as follows: soak the polyethersulfone membrane in anhydrous ethanol for 2 to 3 hours to remove surface impurities and improve the hydrophilicity of the polyethersulfone membrane surface, and then dry it at 60°C for 10 minutes.

5. An application of the p-aminobenzenesulfonic acid blended nanofiltration membrane as described in claim 1, characterized in that... p-Aminobenzenesulfonic acid blended nanofiltration membranes are used for the selective separation of cobalt and lithium ions in acid leaching wastewater from lithium cobalt oxide batteries.

6. An application of the p-aminobenzenesulfonic acid blended nanofiltration membrane according to claim 5, characterized in that... The specific method for selectively separating cobalt from the acid leaching wastewater of lithium cobalt oxide batteries is as follows: the pH of the acid leaching wastewater of lithium cobalt oxide batteries is adjusted to 1~2, and then filtered through the p-aminobenzenesulfonic acid blended nanofiltration membrane to selectively separate cobalt and lithium ions.

7. An application of the p-aminobenzenesulfonic acid blended nanofiltration membrane according to claim 6, characterized in that... The metal ions in the acid leaching wastewater of the lithium cobalt oxide battery cathode material are Li. + and Co 2+ And Li + The concentration is 50 mg / L~100 mg / L, Co 2+ The concentration is 100 mg / L to 300 mg / L.

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