A method for preparing a DABSA sulfonated modified composite nanofiltration membrane by interfacial polymerization in situ

Abstract

The application relates to a method for preparing a DABSA sulfonated modified composite nanofiltration membrane in situ through interfacial polymerization, belonging to the field of lithium extraction from a high magnesium-lithium ratio salt lake. The method comprises the following steps: preparing a DABSA aqueous monomer solution, adding a phase transfer catalyst into the DABSA solution, and then adjusting the pH of the solution to be alkaline; preparing an organic phase monomer solution in an organic solvent; using an interfacial polymerization method, immersing the DABSA solution into the surface of a commercial polymer composite membrane, immersing the organic phase solution into the surface of the commercial polymer composite membrane, and preparing a nascent layer of the DABSA sulfonated modified composite nanofiltration membrane; and further heat-crosslinking the nascent layer of the composite nanofiltration membrane by using a blast oven to obtain the DABSA sulfonated composite nanofiltration membrane. The membrane can be used in the pretreatment process of lithium extraction from a high magnesium-lithium ratio salt lake, and the magnesium-lithium ratio can be preliminarily reduced through the mass transfer promotion effect of the nanofiltration membrane on Mg 2+ , so that the energy consumption of the lithium extraction process is reduced, and the method belongs to the field of magnesium-lithium separation through nanofiltration membranes.

Description

Technical Field

[0001] This invention relates to a method for the synergistic preparation of sulfonated modified composite nanofiltration membrane PA-DABSA using interfacial polymerization technology and in-situ growth. This type of membrane can be used in the pretreatment process of lithium extraction from high magnesium-to-lithium ratio salt lakes, and can improve the Mg2+ content of magnesium-to-lithium ratio cells through nanofiltration. 2+ It promotes mass transfer, reduces energy consumption in the lithium extraction process, and thus reduces the cost of lithium extraction from salt lakes, belonging to the field of lithium extraction from salt lakes. Background Technology

[0002] Salt lake brines, representing approximately 60% of the global lithium reserves, have made lithium extraction technology a crucial direction for lithium resource development. Among numerous extraction methods, nanofiltration membrane technology demonstrates significant advantages in efficiency, energy saving, and environmental friendliness compared to traditional extraction and electrodialysis methods, and has become one of the key technologies for lithium extraction from salt lakes [Liu M, Wei M, Liu G, et al. Journal of Membrane Science, 2024, 712:123247; Ying Y, Ying W, Li Q, et al. Applied Materials Today, 2017, 7:144-158.]. However, the prevalent coexistence of lithium and magnesium ions in salt lake resources, along with the high magnesium-to-lithium ratio (typically tens to thousands) [Liu Y, Li Q, Wang S, et al. Separation and Purification Technology, 2023, 308:122968.], poses a significant challenge to directly extracting lithium from brine using only preferential lithium-permeability membranes.

[0003] In recent years, adsorption-membrane separation coupling technology has gradually become the mainstream technology for treating brine with a high magnesium-to-lithium ratio in salt lakes. This process selectively extracts lithium ions through adsorption, concentrates them through elution (i.e., reduces the magnesium-to-lithium ratio), and finally purifies them through a lithium-permeable membrane. However, the adsorption process suffers from problems such as large adsorbent consumption and high energy consumption, which significantly increases the overall cost of lithium extraction from salt lakes [Butt F, Lewis A, Chen T, et al. Membranes, 2022, 12(4), 373.]. Against this backdrop, developing a magnesium-permeable separation membrane can effectively alleviate the consumption of adsorption columns, and through a dual-membrane coupling process of a magnesium-permeable membrane and a lithium-permeable membrane, it is expected to achieve low energy consumption in the lithium extraction process from salt lakes, thereby reducing the cost of lithium extraction. Therefore, the development of a magnesium-permeable nanofiltration membrane has important research value and application prospects. However, a literature review found that there are currently no reports on research on magnesium-permeable membranes.

[0004] The ion separation mechanisms of nanofiltration membranes mainly include size sieving and the Donnan effect. Because magnesium ions have a larger hydration radius, size sieving alone cannot achieve preferential permeation of magnesium ions. Current research shows that most highly negatively charged nanofiltration membranes... 2+ / Na + During the separation process, MgCl2 showed a higher permeation rate than NaCl. By enhancing the negative charge density of the nanofiltration membrane separation layer [Zhu Y, Dou P, He H, et al. Separation and Purification Technology, 2020, 239:116528; Al-Nahari A, Li S, Su B, et al. Separation and Purification Technology, 2022, 291:120947.], the adsorption and transport of magnesium ions were promoted. Experimental results showed that MgCl2 exhibited better permeability than NaCl, confirming the practical feasibility of preferential magnesium ion permeation due to strong negative charge characteristics. However, the magnesium / sodium selectivity of this system remained low. The main reason is that although the high charge density of sulfonic acid groups on the surface of the nanofiltration membrane separation layer endows it with a preferential adsorption advantage for magnesium ions, the discontinuous distribution of negatively charged functional groups in the mass transfer channels inside the membrane cannot promote the rapid transport of magnesium ions. Therefore, developing a nanofiltration membrane separation layer with continuous strong negative charge characteristics is an effective way to achieve preferential magnesium permeation in nanofiltration membranes.

[0005] Nanofiltration membranes prepared by conventional methods with piperazine and 1,3,5-pyromellitic trimethylol chloride typically have pore diameters of 0.5 nm [Zhu Q, Xu Z, Fu J, et al. Desalination, 2023, 558, 116623.], while Mg... 2+ The hydration radius is approximately 0.43 nm, and relying solely on pore size sieving is insufficient to achieve the desired Mg hydration radius. 2+ The nanofiltration membrane separation layer is positively charged, making it difficult to transport Mg according to the Donnan effect. 2+ This achieves preferential transport. In recent years, researchers have enhanced the transport of Mg by selecting sulfonated amine monomers to regulate the charge and pore size of the separation layer. 2+The mass transfer-promoting effect. 2,5-Diaminobenzenesulfonic acid (DABSA) is a common polymer material. Due to the presence of both amino active reaction sites and sulfonic acid functional groups in its molecular structure, it is widely used in the preparation of separation membranes, and both exhibit excellent separation performance [Liu X, Wang J, Shang Y, et al. Journal of the American Chemical Society, 2024, 146: 2313-2318; Wei X, Gan Z, Shen Y, et al. Journal of Colloid and Interface Science, 2019, 553: 475-483.]. Interfacial polymerization is an effective method for preparing composite nanofiltration membranes [Zhang X, Zhang H, Wang L, et al. Desalination, 2024, 578:117422; Zhang H, Chen Y, Tang S, et al. Journal of Membrane Science, 2022, 664:121070.]. Therefore, this invention utilizes interfacial polymerization and in-situ growth methods to synergistically prepare negatively charged, continuously sulfonated (DABSA) modified composite nanofiltration membranes. This method effectively improves the nanofiltration membrane's ability to filter Mg. 2+ The mass transfer rate, while maintaining the mass transfer rate of Li + The process exhibits high efficiency retention characteristics. This preparation method is simple and reproducible. Through charge continuity regulation and mass transfer path optimization, a new strategy is proposed for the pretreatment stage of lithium extraction from high magnesium-to-lithium ratio salt lakes. Summary of the Invention

[0006] The purpose of this invention is to construct a Mg-containing compound using interfacial polymerization technology and in-situ growth synergistically. 2+ The preferred transport sulfonated modified composite nanofiltration membrane has a separation layer with continuous negatively charged mass transfer channels, enabling it to transport Mg. 2+ The composite membrane, prepared for preferential transport of magnesium-to-lithium ratio lithium, is applied in the pretreatment process of lithium extraction from high magnesium-to-lithium ratio salt lakes using nanofiltration separation, exhibiting excellent preferential transport of magnesium. 2+ Transmission performance and stability.

[0007] The method includes the following steps:

[0008] (1) Pretreatment of the polymer composite base film to remove organic matter, inorganic matter and microorganisms from the surface of the base film;

[0009] (2) Disperse the sulfonated amine monomer in deionized water, add a certain amount of phase transfer catalyst to the solution, adjust the pH of the solution to alkaline such as 10, and prepare a homogeneous aqueous solution by ultrasound.

[0010] (3) Dissolve a certain amount of organic phase monomer in an organic solvent to prepare a homogeneous organic phase solution, which can then be further utilized by ultrasound.

[0011] (4) Using interfacial polymerization, the aqueous solution is immersed in the surface of the porous base membrane, and after a certain period of time, the excess aqueous solution is removed by a rubber roller.

[0012] (5) After (4) is completed, a certain amount of organic phase solution is immersed in the surface of the porous base membrane, and after a certain time, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated modified composite nanofiltration membrane.

[0013] (6) The composite membrane obtained in (5) is placed in a forced-air drying oven for heat treatment for a certain period of time. A 2,5-diaminobenzenesulfonic acid-based sulfonated modified (DABSA) composite nanofiltration membrane is obtained.

[0014] The substrate used in this invention to prepare the sulfonated modified composite nanofiltration membrane can be a commercially available polymer composite nanofiltration membrane. The membrane material is aromatic polyamide, polypiperazine amide, sulfonated polysulfone, polyurea, polyether, or a mixture of polydienol / polypiperazine amide. The porous membrane has a pore size of approximately 1.0 nm.

[0015] In step (2), the aqueous monomer used for interfacial polymerization, sulfonated amine monomer, is selected from 2,5-diaminobenzenesulfonic acid (DABSA) with a mass percentage concentration of 0.3-0.9% in the aqueous solution, and the phase transfer catalyst CTAB has a mass percentage concentration of 0.012-0.036%.

[0016] Step (3) Organic phase monomers: 1,3,5-pyromellitic trichloroisocyanurate, terephthaloyl chloride, cyanuric chloride, toluene diisocyanate, isophthaloyl chloride, hexamethylene diisocyanate. The mass percentage concentration is 0.08-0.15%, preferably 0.1%.

[0017] Organic solvents: n-hexane, cyclopentyl methyl ether, toluene, dichloromethane, cyclopentane, xylene, chloroform.

[0018] In step (4), the time for the aqueous solution to immerse in the polymer composite membrane is 4-8 min, preferably 5 min.

[0019] In step (5), the time for the organic phase solution to immerse in the polymer composite membrane is 0.8-1.2 min, preferably 1 min.

[0020] The reaction temperature in steps (4) and (5) is 15-45°C, preferably 25°C, and the reaction humidity is 20-30%RH, preferably 21%RH.

[0021] This invention utilizes nanofiltration membranes for lithium extraction pretreatment processes from lakes containing high-magnesium lithium salts (magnesium-lithium molar ratio greater than or equal to 1:1). The nanofiltration membrane effectively removes Mg... 2+The mass transfer-promoting effect achieves the initial goal of reducing the magnesium-lithium ratio in salt lakes.

[0022] The principle of this invention is as follows: Utilizing interfacial polymerization, the amino group (-NH2) exhibits strong nucleophilicity, attacking the carbonyl carbon atom of the acyl chloride group (-COCl) to undergo a nucleophilic substitution reaction, generating an amide bond (-CONH-). Simultaneously, hydrogen chloride (HCl) is released as a byproduct. This byproduct is rapidly neutralized by the alkali in the aqueous phase, forming a sulfonated polyamide membrane. Alternatively, the amino group (-NH2) attacks the isocyanate group (-NCO) to react and generate a sulfonated polyurea membrane. Furthermore, the sulfonic acid groups are enriched on the surface of the separation layer, giving the highly cross-linked separation layer network a negative charge, which effectively reacts with Mg... 2+ The Dornan effect occurs, greatly promoting the growth of Mg. 2+ During transport in the separation layer, sulfonic acid groups react with Li + Na + The weaker interaction forces trap Mg on the upstream side of the membrane, thus making it difficult for Mg to interact with the membrane. 2+ Li + Na + Retained (i.e., preferential Mg) 2+ (Transmission) to achieve magnesium-lithium separation.

[0023] Technological advantages

[0024] This invention prepares a sulfonated modified composite nanofiltration membrane with a negatively charged through-structure using interfacial polymerization technology. This unique negatively charged through-structure can effectively promote the formation of Mg... 2+ Selective transport through mass transfer channels improves membrane structural stability and permeation flux while maintaining Li + Retention rate; This method is a typical sulfonation-modified composite membrane preparation technology, which is simple to operate and structurally stable, and has potential for industrial application. The sulfonation-modified composite nanofiltration membrane prepared using this technology was used to separate 1 g / L sodium sulfate aqueous solution, 1 g / L magnesium chloride aqueous solution, and 1 g / L lithium chloride solution. At an operating pressure of 0.4 MPa, the fluxes were 6.66 L / m³, respectively. 2 h bar, 7.37L / m 2 h bar and 6.59L / m 2 h bar; the retention rates were 97.3%, 53.59%, and 81.5%, respectively. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope (SEM) image of the cross-section of the DABSA sulfonated composite nanofiltration membrane subjected to interfacial polymerization treatment in Example 1.

[0026] Figure 2 This is a scanning electron microscope image of the surface of the DABSA sulfonated composite nanofiltration membrane in Example 1. Detailed Implementation

[0027] The present invention will be described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0028] The DABSA sulfonated composite nanofiltration membrane prepared using this technology is used to separate 1 g / L sodium sulfate aqueous solution system, 1 g / L magnesium chloride aqueous solution system, and 1 g / L lithium chloride solution system.

[0029] Example 1

[0030] Commercially available polymer composite nanofiltration membranes are used, mostly polysulfone ultrafiltration membrane materials, with pore sizes of 0.001–0.1 μm and membrane areas of 22.05 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0031] Preparation method of DABSA sulfonated composite nanofiltration membrane

[0032] (1) The polysulfone ultrafiltration membrane with a length of about 5cm is rinsed with deionized water to remove organic matter, inorganic matter and microorganisms on its surface. Then the deionized water is replaced and stored until use.

[0033] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0034] (3) Dissolve 0.1 wt% of 1,3,5-pyromellitic chloride monomer in n-hexane organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0035] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 15-40℃, preferably 25℃, and the humidity is 20-35%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0036] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0037] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 min. 2,5-Diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained.

[0038] (7) The PA-DABSA composite nanofiltration membrane prepared above is soaked in deionized water for storage.

[0039] When the operating pressure is 0.4 MPa, the sodium sulfate rejection rate and flux are 97.3% and 6.66 L / m³, respectively. 2 hbar; In another parallel experiment, the rejection rate and flux for sodium sulfate were 99.73% and 6.72 L / m, respectively. 2 h bar.

[0040] When the operating pressure is 0.4 MPa, the rejection rate and flux for magnesium chloride are 53.59% and 7.37 L / m³, respectively. 2 hbar. In another parallel experiment, the rejection rate and flux for magnesium chloride were 43.71% and 8.39 L / m³, respectively. 2 h bar.

[0041] When the operating pressure is 0.4 MPa, the lithium chloride rejection rate and flux are 81.5% and 6.59 L / m³, respectively. 2 hbar.

[0042] Example 2

[0043] Commercially available polymer composite nanofiltration membranes are used, mostly made of polypiperazine amide membrane material, with a pore size of 0.5–1.0 nm and a membrane area of ​​10.8 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0044] Preparation method of DABSA sulfonated composite nanofiltration membrane

[0045] (1) Rinse the polypiperazine amide membrane, which is about 7cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0046] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0047] (3) Dissolve 0.1 wt% of 1,3,5-pyromellitic chloride monomer in n-hexane organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0048] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 20-40℃, preferably 25℃, and the reaction humidity is 20-30%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0049] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0050] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven for 10 minutes and heat-treated at 60°C. A 2,5-diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained. (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. When the operating pressure was 0.4 MPa, the sodium sulfate rejection rate and flux were 98.5% and 7.63 L / m, respectively. 2 h bar; when the operating pressure is 0.4 MPa, the magnesium chloride rejection rate is 45.69%; when the operating pressure is 0.4 MPa, the lithium chloride rejection rate is 80.3%.

[0051] Example 3

[0052] Commercially available polymer composite nanofiltration membranes are used, mostly made of polyurea, with pore sizes of 0.5–2 nm and a membrane area of ​​15.78 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0053] Preparation method of DABSA sulfonated composite nanofiltration membrane

[0054] (1) Rinse the polyurea membrane, which is about 5cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0055] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0056] (3) Dissolve 0.1 wt% of 1,3,5-pyromellitic chloride monomer in n-hexane organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0057] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 15-45℃, preferably 25℃, and the reaction humidity is 20-35%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0058] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0059] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 min. 2,5-Diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained.

[0060] (7) The PA-DABSA composite nanofiltration membrane prepared above is soaked in deionized water for storage.

[0061] When the operating pressure is 0.4 MPa, the sodium sulfate rejection rate and flux are 96.98% and 7.36 L / m³, respectively. 2 hbar.

[0062] When the operating pressure is 0.4 MPa, the magnesium chloride rejection rate is 47.2%; when the operating pressure is 0.4 MPa, the lithium chloride rejection rate is 79.6%.

[0063] Example 4

[0064] Commercially available polymer composite nanofiltration membranes are used, mostly aromatic polyamide nanofiltration membrane materials, with pore sizes of 0.5–1.2 nm and membrane areas of 20.3 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0065] Preparation method of DABSA sulfonated composite nanofiltration membrane

[0066] (1) Rinse the aromatic polyamide nanofiltration membrane, which is about 6 cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0067] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0068] (3) Dissolve 0.1 wt% of 1,3,5-pyromellitic chloride monomer in n-hexane organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0069] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 20-40℃, preferably 35℃, and the reaction humidity is 20-30%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0070] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0071] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 min. 2,5-Diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained.

[0072] (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. At an operating pressure of 0.4 MPa, the rejection rate and flux for magnesium chloride were 49.6% and 6.88 L / m³, respectively. 2 h bar. The sodium sulfate rejection rate was 95.77% at an operating pressure of 0.4 MPa, and the lithium chloride rejection rate was 81.4% at an operating pressure of 0.4 MPa.

[0073] Example 5

[0074] Commercially available polymer composite nanofiltration membranes are used, mostly polysulfone ultrafiltration membrane materials, with pore sizes of 0.001–0.1 μm and membrane areas of 22.05 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0075] Preparation method of DABSA sulfonated composite nanofiltration membrane

[0076] (1) The polysulfone ultrafiltration membrane with a length of about 5cm is rinsed with deionized water to remove organic matter, inorganic matter and microorganisms on its surface. Then the deionized water is replaced and stored until use.

[0077] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0078] (3) Dissolve 0.1 wt% terephthaloyl chloride monomer in the organic solvent dichloromethane, and prepare a homogeneous organic phase solution by ultrasound.

[0079] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 20-30℃, preferably 25℃, and the reaction humidity is 20-30%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0080] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0081] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 min. 2,5-Diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained.

[0082] (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. At an operating pressure of 0.4 MPa, the rejection rate for lithium chloride was 83.5%, and the rejection rate for magnesium chloride was 42.7%. At an operating pressure of 0.4 MPa, the rejection rate and flux for sodium sulfate were 93.75% and 6.83 L / m³, respectively. 2 h bar.

[0083] Example 6

[0084] Commercially available polymer composite nanofiltration membranes are used, mostly made of polypiperazine amide membrane material, with a pore size of 0.5–1.0 nm and a membrane area of ​​22.05 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0085] Preparation method of PA-DABSA sulfonated composite nanofiltration membrane

[0086] (1) Rinse the polypiperazine amide membrane, which is about 7cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0087] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0088] (3) Dissolve 0.1 wt% of cyanuric chloride monomer in cyclopentyl methyl ether organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0089] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 20-45℃, preferably 25℃, and the reaction humidity is 20-40%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0090] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0091] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 minutes. A 2,5-diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained. (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. When the operating pressure was 0.4 MPa, the rejection rate for sodium sulfate was 96.9%, and the rejection rate for magnesium chloride was 45.2%.

[0092] Example 7

[0093] Commercially available polymer composite nanofiltration membranes are used, mostly made of polyurea, with pore sizes of 0.5–2 nm and a membrane area of ​​7.07 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0094] Preparation method of PA-DABSA sulfonated composite nanofiltration membrane

[0095] (1) Rinse the polyurea membrane, which is about 5cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0096] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0097] (3) Dissolve 0.1 wt% of toluene diisocyanate monomer in toluene organic solvent and prepare a homogeneous organic phase solution by ultrasound.

[0098] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 15-30℃, preferably 25℃, and the reaction humidity is 20-30%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0099] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0100] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 minutes. A 2,5-diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained. (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. When the operating pressure was 0.4 MPa, the rejection rate for lithium chloride was 83.5%, and the rejection rate for magnesium chloride was 42.1%.

[0101] Example 8

[0102] Commercially available polymer composite nanofiltration membranes are used, mostly aromatic polyamide nanofiltration membrane materials, with pore sizes of 0.5–1.2 nm and membrane areas of 25 cm². 2 The concentration of DABSA in the aqueous phase is 0.7 wt%.

[0103] Preparation method of PA-DABSA sulfonated composite nanofiltration membrane

[0104] (1) Rinse the aromatic polyamide nanofiltration membrane, which is about 6 cm long, with deionized water to remove organic matter, inorganic matter and microorganisms from its surface. Then replace the deionized water and store it until use.

[0105] (2) Disperse 0.7 wt% DABSA monomer in deionized water, add 0.028 wt% CTAB phase transfer catalyst to the solution, and adjust the pH of the solution to 10 using NaOH. Prepare a homogeneous aqueous solution using ultrasound.

[0106] (3) Dissolve 0.1 wt% of cyanuric chloride monomer in the organic solvent cyclopentyl methyl ether and prepare a homogeneous organic phase solution by ultrasound.

[0107] (4) Using interfacial polymerization, the temperature of the constant temperature and humidity chamber is set to 20-40℃, preferably 35℃, and the reaction humidity is 20-30%RH, preferably 21%RH. The aqueous solution is immersed in the surface of the porous base membrane, and after reacting for 5 minutes, the excess aqueous solution is removed with a rubber roller.

[0108] (5) After (4) is completed, the organic phase solution is immersed in the surface of the porous base membrane. After reacting for 1 minute, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane.

[0109] (6) The composite membrane obtained in (5) was placed in a forced-air drying oven and heat-treated at 60°C for 10 minutes. A 2,5-diaminobenzenesulfonic acid (PA-DABSA) composite nanofiltration membrane was obtained. (7) The PA-DABSA composite nanofiltration membrane prepared above was stored by immersing it in deionized water. When the operating pressure was 0.4 MPa, the rejection rate for magnesium chloride was 47.5%, and the rejection rate for lithium chloride was 69.3%.

Claims

1. A method for in-situ preparation of DABSA sulfonated modified composite nanofiltration membranes via interfacial polymerization for magnesium-lithium separation, characterized in that, Includes the following steps: (1) Pre-treat the porous base membrane to remove organic matter, inorganic matter and microorganisms from the surface of the base membrane; (2) Disperse the sulfonated amine monomer in deionized water, add a certain amount of phase transfer catalyst CTAB to the solution, adjust the pH of the solution to alkaline, and prepare a homogeneous aqueous solution by ultrasound; the sulfonated amine monomer is selected from 2,5-diaminobenzenesulfonic acid (DABSA). (3) Dissolve a certain amount of organic phase monomer in an organic solvent to prepare a homogeneous organic phase solution; (4) Using interfacial polymerization, the surface of the porous base membrane is immersed in an aqueous solution, and after a certain period of time, the excess aqueous solution is removed by a rubber roller. (5) After (4) is completed, a certain amount of organic phase solution is immersed in the surface of the porous base membrane. After a certain period of time, the excess organic phase solution is poured out to prepare the primary layer of the sulfonated composite nanofiltration membrane. (6) The porous base membrane with the primary layer obtained in (5) is placed in a blower oven for heat treatment to obtain DABSA sulfonated modified composite nanofiltration membrane.

2. The method according to claim 1, characterized in that, The porous base membrane is a commercially available polymer composite nanofiltration membrane. The porous base membrane material is selected from one of aromatic polyamide, polypiperazine amide, sulfonated polysulfone, polyurea, and polyether. The pore size of the porous base membrane is 1.0 nm.

3. The method according to claim 1, characterized in that, The mass percentage concentration of 2,5-diaminobenzenesulfonic acid (DABSA) in aqueous solution is 0.3% to 0.9%.

4. The method according to claim 1, characterized in that, The mass percentage concentration of the phase transfer catalyst CTAB in the aqueous solution is 0.012~0.036%.

5. The method according to claim 1, characterized in that, Step (3) The organic phase monomer is selected from one or more of 1,3,5-pyromellitic trichloroisocyanurate, terephthaloyl chloride, cyanuric chloride, toluene diisocyanate, isophthaloyl chloride, and hexamethylene diisocyanate; the mass percentage concentration of the organic phase monomer in the organic phase solution is 0.08-0.15%; the organic solvent is selected from one or more of n-hexane, cyclopentyl methyl ether, toluene, dichloromethane, cyclopentane, xylene, and chloroform.

6. The method according to claim 5, characterized in that, In step (3), the mass percentage concentration of the organic phase monomer in the organic phase solution is 0.1%.

7. The method according to claim 1, characterized in that, In step (4), the porous base membrane surface is immersed in the aqueous solution for 4-8 minutes.

8. The method according to claim 7, characterized in that, In step (4), the porous base membrane surface is immersed in the aqueous solution for 5 minutes.

9. The method according to claim 1, characterized in that, In step (5), the time for immersing the porous base membrane surface in the organic phase solution is 0.8-1.2 min.

10. The method according to claim 9, characterized in that, In step (5), the time for immersing the porous base membrane surface in the organic phase solution is 1 min.

11. The method according to claim 1, characterized in that, The reaction temperature in steps (4) and (5) is 15-45 °C and the relative humidity is 20-40%.

12. The method according to claim 1, characterized in that, The reaction temperature in steps (4) and (5) is 25 °C and the relative humidity is 21%.

13. The DABSA sulfonated modified composite nanofiltration membrane prepared according to any one of claims 1-12.

14. The application of the DABSA sulfonated modified composite nanofiltration membrane prepared according to any one of claims 1-12, wherein the nanofiltration membrane is used in the pretreatment process of lithium extraction from high-magnesium lithium salt lakes with a magnesium-lithium molar ratio greater than or equal to 1:1, and the nanofiltration membrane is used to filter Mg... 2+ The mass transfer-promoting effect, while the sulfonic acid group reacts with Li + Na + The weaker interaction forces trap Mg on the upstream side of the membrane, thus making it difficult for Mg to interact with the membrane. 2+ Li + Na + The interception achieved the initial goal of reducing the magnesium-lithium ratio in the salt lake.

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