A method for preparing an organic solvent-resistant self-supporting hydrogel membrane based on phenolic compound-metal ion coordination modification.

Abstract

This invention discloses a method for preparing a self-supporting hydrogel membrane resistant to organic solvents based on phenolic compound-metal ion coordination modification, belonging to the field of membrane separation technology. It addresses the problems of poor tolerance of commonly used organic solvent-resistant membranes in strongly polar aprotic solvents, and the difficulty in controlling the pore size and separating small molecules in alginate-based hydrogel membranes in organic solvents. This invention first prepares a sodium alginate casting solution, which is then placed in an aqueous metal ion solution to form an alginate-based hydrogel membrane. Then, a complexation reaction between phenolic compounds and metal ions occurs on the surface of the alginate-based hydrogel membrane, forming a separation layer with a fixed pore size, thereby enabling precise separation of nanoscale small molecules in organic solvent systems. This gel membrane preparation method is simple, low-cost, uses green and biodegradable materials, and avoids the use of organic solvents during membrane fabrication, making it promising for applications in fine separation and organic solvent recovery.

Description

[Technical Field]

[0001] This invention relates to a method for preparing a self-supporting hydrogel membrane resistant to organic solvents based on phenolic compound-metal ion coordination modification, belonging to the field of membrane separation technology. [Background Technology]

[0002] With the rapid development of industries such as chemical engineering, printing and dyeing, and pharmaceuticals, the consumption of organic solvents in these industries is increasing year by year. Improper handling of these organic solvents will pose a huge threat and damage to the environment. Organic solvent nanofiltration (OSN), as an emerging membrane separation technology, has advantages over traditional processes such as distillation and extraction, including simple preparation process, low energy consumption, and easy operation. It can efficiently and accurately separate small organic molecules of 200-1000 g / mol in organic solvent systems, and has become a research hotspot for organic solvent treatment in recent years.

[0003] Currently, commonly used materials for preparing organic solvent-resistant nanofiltration membranes can be divided into inorganic materials and polymer membrane materials. Membranes made from inorganic materials exhibit good resistance to various types of organic solvents; however, inorganic membranes suffer from uneven pore size distribution and high fabrication costs. In contrast, polymer membranes, due to their simpler fabrication process and lower raw material prices, have gradually become the mainstream choice for preparing organic solvent-resistant membranes. However, organic solvent-resistant nanofiltration membranes using materials such as polyacrylonitrile and polyimide as base membranes have limited resistance to organic solvents, and organic solvents are used multiple times in the preparation of the base membrane and subsequent intermediate layer construction and interfacial polymerization processes. As an emerging green technology, organic solvent nanofiltration should minimize the use of organic solvents and simplify the membrane fabrication process to reduce energy consumption. Therefore, selecting more environmentally friendly materials and demonstrating their practicality in the organic solvent nanofiltration process is essential.

[0004] Hydrogels are polymeric materials with a three-dimensional network structure due to moderate cross-linking, belonging to cross-linked polymers. Hydrogels contain a large number of hydrophilic groups, allowing water molecules to rapidly enter the polymer, causing the gel to expand in volume. This expansion, caused by water molecules, leads to the extension of the network molecular chains in the hydrogel into three-dimensional space. The resulting stress causes elastic contraction of the molecular network, leading to further shrinkage. When this swelling-contraction behavior reaches equilibrium, swelling equilibrium is achieved. Natural hydrogel materials have become a focus of attention due to their high adsorption capacity, low cost, and non-toxicity, and are widely used in water treatment. Commonly used natural biodegradable polymeric materials include alginate and chitosan.

[0005] Sodium alginate (NaAlg) is a linear block copolymer extracted from brown algae, composed of β-D-mannuronic acid (M) and α-L-guluronic acid (G). Its molecule contains free hydroxyl and carboxyl groups, and it can form a hydrogel through crosslinking with divalent or polyvalent metal ions under mild conditions. Zhao Kongyin et al. used sodium alginate as the film-forming substrate and polyethylene glycol as the porogen, and Ca... 2+ Self-supporting calcium alginate (CaAlg) hydrogel filtration membranes were prepared using ions as crosslinking agents. These hydrogel membranes exhibited excellent dye rejection performance and high flux in aqueous systems [K. Zhao, X. Zhang, J. Wei, et al., Journal of Membrane Science, 2015, 492: 536-546]. However, when the pure ion-crosslinked calcium alginate hydrogel membrane was placed in different organic solvent systems, the original pore size changed, resulting in a significant decrease in dye rejection performance.

[0006] Phenolic compounds are a class of compounds composed of one or more aromatic rings combined with one or more hydroxyl groups, and are widely found in animals and plants. Among them, polyphenolic compounds (such as dopamine, tannic acid, gallic acid, and catechin) contain a large number of catechol structures, which can not only coordinate with metal ions, but also have excellent adhesion properties, enabling them to adhere to the surface of the support layer, making them excellent membrane modification materials.

[0007] Therefore, based on the technical defects of calcium alginate hydrogel membranes and the properties of phenolic compounds, a self-supporting hydrogel membrane resistant to organic solvents based on phenolic compound-metal ion coordination modification was developed. The large pore size of the original alginate-based hydrogel membrane is covered by a polyphenol-metal network, and the separation performance of the alginate-based hydrogel membrane in organic solvents is improved by utilizing the fixed pore size of the polyphenol-metal network itself. [Summary of the Invention]

[0008] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is that commonly used organic solvent resistant membranes have poor tolerance in strongly polar aprotic solvents, and that alginate-based hydrogel membranes are difficult to control in terms of pore size and to separate small molecules in organic solvents.

[0009] The technical solution of this invention to solve the problems of poor tolerance of commonly used organic solvent-resistant membranes in strongly polar aprotic solvents and the difficulty in controlling the pore size and separating small molecules in alginate-based hydrogel membranes in organic solvents is to prepare a layer of phenolic compound-metal ion coordination network on the surface of the alginate-based hydrogel membrane, thereby obtaining a composite hydrogel filter membrane with controllable pore size.

[0010] This invention provides a method for preparing a solvent-resistant self-supporting hydrogel membrane based on phenolic compound-metal ion coordination modification, characterized by the following steps:

[0011] a) Under magnetic stirring, slowly add 0.1-2g of sodium alginate to 20-80mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12 hours to remove bubbles and obtain the casting solution.

[0012] b) Prepare an aqueous solution of a metal salt with a mass percentage of 1%-10% as an ionic crosslinking agent;

[0013] c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 250-1000 μm for coating, and then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 1-20 min to obtain an alginate-based hydrogel film.

[0014] d) Soak the alginate-based hydrogel membrane obtained in step c) in the ionic crosslinking agent obtained in step b) for use;

[0015] e) Prepare a phenolic compound solution with a mass percentage of 0.1%-10%;

[0016] f) Prepare an aqueous solution of metal salt with a mass percentage of 0.1%-10%;

[0017] g) Immerse the metal salt aqueous solution obtained in step f) on the surface of the alginate-based hydrogel membrane obtained in step d) for 10-300s, rinse with deionized water and dry in air to obtain alginate-based hydrogel membrane with metal ion deposition.

[0018] h) Coat the surface of the alginate-based hydrogel membrane with metal ion deposition obtained in step g) with the phenolic compound solution obtained in step e) for 10-300s to carry out the complexation reaction between phenolic compound and metal ion. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted phenolic compound solution, and obtain a self-supporting alginate-based hydrogel membrane with phenolic compound-metal ion coordination modification.

[0019] The phenolic compounds described in this invention are one or more of the following: dopamine hydrochloride, tannic acid, catechol, caffeic acid, ferric titanate, anthocyanins, proanthocyanidins, tannins, resveratrol, tannic acid, caffeic acid, cinnamic acid, chinocanaic acid, chlorogenic acid, caustic acid, tea polyphenols, grape seed polyphenols, agrimony extract, sanguisorbin, rose extract, anthocyanins, catechins, epicatechin, geranium extract, cinnamic acid, evening primrose extract, astaxanthin, pungent extract, cornus extract, quercetin, gallic acid, and ellagic acid.

[0020] The metal salts described in this invention are one or more of the following: calcium chloride, calcium sulfate, magnesium sulfate, magnesium chloride, ferric chloride, ferric sulfate, copper chloride, copper sulfate, manganese sulfate, manganese chloride, zinc chloride, zinc sulfate, barium sulfate, and barium chloride. Detailed Implementation

[0021] The following describes specific embodiments of the present invention, but the present invention is not limited to these embodiments.

[0022] Example 1.

[0023] a) Under magnetic stirring, slowly add 2g of sodium alginate to 80mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12 hours to remove bubbles and obtain the casting solution.

[0024] b) Prepare a 3% (w / w) calcium chloride aqueous solution as an ion crosslinking agent;

[0025] c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 1000 μm for coating, and then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 2 min to obtain calcium alginate hydrogel film.

[0026] d) Soak the calcium alginate hydrogel membrane obtained in step c) in the calcium chloride solution obtained in step b) for use;

[0027] e) Prepare an aqueous solution of tannic acid with a mass percentage of 0.4%;

[0028] f) Prepare a 0.3% (w / w) ferric chloride aqueous solution;

[0029] g) Immerse the ferric chloride solution obtained in step f) on the surface of the calcium alginate hydrogel membrane obtained in step d) for 180s, rinse with deionized water and dry in air to obtain a calcium alginate hydrogel membrane with iron ion deposition.

[0030] h) Coat the surface of the calcium alginate hydrogel membrane with iron ion deposition obtained in step g) with the tannic acid solution obtained in step e) for 10s to carry out the complexation reaction of tannic acid and iron ion. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted tannic acid solution and obtain the self-supporting calcium alginate hydrogel membrane with tannic acid-iron ion coordination modification.

[0031] i) The tannic acid-iron ion coordinated modified self-supporting calcium alginate hydrogel membrane obtained in the above steps was subjected to dye retention in ethanol solvent. The retention rates for Congo Red, Acid Red 66, Reactive Red 2, and Acid Chrome Blue K were greater than 95%, with an ethanol flux of 20 L·m⁻¹. -2 ·h -1 ·bar -1After immersion in the highly polar aprotic solvent N,N-dimethylformamide for 3 months, the retention rate of the aforementioned dyes, such as Congo red, remained greater than 92%, with an ethanol flux of 21 L·m⁻¹. -2 ·h -1 ·bar -1 .

[0032] Example 2.

[0033] a) Under magnetic stirring, slowly add 1.2g of sodium alginate to 40mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12h to remove bubbles and obtain the casting solution.

[0034] b) Prepare a 6% (w / w) calcium chloride aqueous solution as an ion crosslinking agent;

[0035] c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 750 μm and scrape the film, then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 5 min to obtain calcium alginate hydrogel film.

[0036] d) Soak the calcium alginate hydrogel membrane obtained in step c) in the calcium chloride solution obtained in step b) for use;

[0037] e) Prepare an aqueous solution of tannic acid with a mass percentage of 0.4%;

[0038] f) Prepare a 0.2% (w / w) aqueous solution of copper chloride;

[0039] g) Immerse the copper chloride solution obtained in step f) on the surface of the calcium alginate hydrogel membrane obtained in step d) for 300s, rinse with deionized water and dry in air to obtain a calcium alginate hydrogel membrane with copper ion deposition.

[0040] h) Coat the surface of the calcium alginate hydrogel membrane with copper ion deposition obtained in step g) with the tannic acid solution obtained in step e) for 60s to carry out the complexation reaction between tannic acid and copper ions. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted tannic acid solution and obtain the self-supporting calcium alginate hydrogel membrane with tannic acid-copper ion coordination modification.

[0041] i) The tannic acid-copper ion-modified self-supporting calcium alginate hydrogel membrane obtained in the above steps was subjected to dye retention in ethanol solvent. The retention rates for Congo Red, Acid Red 66, Reactive Red 2, and Acid Chrome Blue K were greater than 95%, with an ethanol flux of 22 L·m⁻¹. -2 ·h -1 ·bar -1 After immersion in the strongly polar aprotic solvent N,N-dimethylformamide for 3 months, the retention rate of the aforementioned dyes, such as Congo red, remained greater than 92%, with an ethanol flux of 23 L·m⁻¹.-2 ·h -1 ·bar -1 .

[0042] Example 3.

[0043] a) Under magnetic stirring, slowly add 2g of sodium alginate to 80mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12 hours to remove bubbles and obtain the casting solution.

[0044] b) Prepare a 10% (w / w) barium chloride aqueous solution as an ionic crosslinking agent;

[0045] c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 1000 μm for coating, and then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 10 min to obtain a barium alginate hydrogel film.

[0046] d) Soak the barium alginate hydrogel membrane obtained in step c) in the barium chloride solution obtained in step b) for use;

[0047] e) Prepare a 0.2% (w / w) solution of dopamine hydrochloride;

[0048] f) Prepare a 0.6% (w / w) ferric chloride aqueous solution;

[0049] g) Immerse the ferric chloride solution obtained in step f) on the surface of the barium alginate hydrogel membrane obtained in step d) for 180s, rinse with deionized water and dry in air to obtain a barium alginate hydrogel membrane with iron ion deposition.

[0050] h) Coat the surface of the barium alginate hydrogel membrane with iron ion deposition obtained in step g) with the dopamine hydrochloride solution obtained in step e) for 90s to carry out the complexation reaction between dopamine hydrochloride and iron ions. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted dopamine hydrochloride solution and obtain the self-supporting barium alginate hydrogel membrane with dopamine hydrochloride-iron ion coordination modification.

[0051] i) The self-supporting barium alginate hydrogel membrane modified with dopamine hydrochloride-iron ion coordination obtained in the above steps was subjected to dye retention in ethanol solvent. The retention rates for Congo Red, Acid Red 66, Reactive Red 2, and Acid Chrome Blue K were greater than 85%, with an ethanol flux of 18 L·m⁻¹. -2 ·h -1 ·bar -1 After immersion in the strongly polar aprotic solvent N,N-dimethylformamide for 3 months, the retention rate of the aforementioned dyes, such as Congo red, remained greater than 80%, with an ethanol flux of 19 L·m⁻¹. -2 ·h -1 ·bar -1 .

[0052] Example 4.

[0053] a) Under magnetic stirring, slowly add 2g of sodium alginate to 80mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12 hours to remove bubbles and obtain the casting solution.

[0054] b) Prepare a 3% (w / w) zinc chloride aqueous solution as an ionic crosslinking agent;

[0055] c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 750 μm for coating, and then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 2 min to obtain zinc alginate hydrogel film.

[0056] d) Soak the zinc alginate hydrogel membrane obtained in step c) in the zinc chloride solution obtained in step b) for use;

[0057] e) Prepare a 2% (w / w) titanium-iron reagent solution;

[0058] f) Prepare a 1% (w / w) aqueous solution of copper chloride;

[0059] g) Immerse the copper chloride solution obtained in step f) on the surface of the zinc alginate hydrogel membrane obtained in step d) for 60s, rinse with deionized water and dry in air to obtain a zinc alginate hydrogel membrane with copper ion deposition.

[0060] h) Coat the surface of the zinc alginate hydrogel membrane with copper ion deposition obtained in step g) with the titanium iron reagent solution obtained in step e) for 20s to carry out the complexation reaction between titanium iron reagent and copper ion. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted titanium iron reagent solution and obtain the self-supporting zinc alginate hydrogel membrane with titanium iron reagent-copper ion coordination modification.

[0061] i) The self-supporting zinc alginate hydrogel membrane modified with titanium iron reagent-copper ion coordination obtained in the above steps was subjected to dye retention in ethanol solvent. The retention rates for Congo Red, Acid Red 66, Reactive Red 2, and Acid Chrome Blue K were greater than 80%, with an ethanol flux of 30 L·m⁻¹. -2 ·h -1 ·bar -1 After immersion in the strongly polar aprotic solvent N,N-dimethylformamide for 3 months, the retention rate of the aforementioned dyes, such as Congo red, remained greater than 75%, with an ethanol flux of 32 L·m⁻¹. -2 ·h -1 ·bar -1 .

Claims

1. A method for preparing an organic solvent-resistant self-supporting hydrogel membrane based on phenolic compound-metal ion coordination modification, characterized in that: First, sodium alginate casting solution is prepared and placed in an aqueous solution of metal ions to form an alginate-based hydrogel membrane. Then, a complexation reaction between phenolic compounds and metal ions is carried out on the surface of the alginate-based hydrogel membrane to form a separation layer with a fixed pore size. The preparation steps include the following: a) Under magnetic stirring, slowly add 0.1-2g of sodium alginate to 20-80mL of deionized water. After it is completely dissolved, let the resulting solution stand for 12 hours to remove bubbles and obtain the casting solution. b) Prepare an aqueous solution of a metal salt with a mass percentage of 1%-10% as an ionic crosslinking agent; c) Pour the casting solution obtained in step a) onto a dry and clean glass plate, adjust the height of the coating tool to 250-1000 μm for coating, and then immerse the film together with the glass plate in the ionic crosslinking agent obtained in step b) for 1-20 min to obtain an alginate-based hydrogel film. d) Soak the alginate-based hydrogel membrane obtained in step c) in the ionic crosslinking agent obtained in step b) for use; e) Prepare a phenolic compound solution with a mass percentage of 0.1%-10%; f) Prepare an aqueous solution of metal salt with a mass percentage of 0.1%-10%; g) Immerse the metal salt aqueous solution obtained in step f) on the surface of the alginate-based hydrogel membrane obtained in step d) for 10-300s, rinse with deionized water and dry in air to obtain alginate-based hydrogel membrane with metal ion deposition. h) Coat the surface of the alginate-based hydrogel membrane with metal ion deposition obtained in step g) with the phenolic compound solution obtained in step e) for 10-300s to carry out the complexation reaction between phenolic compound and metal ion. Wash the hydrogel membrane after reaction with deionized water to remove the unreacted phenolic compound solution, and obtain a self-supporting alginate-based hydrogel membrane with phenolic compound-metal ion coordination modification.

2. The method for preparing an organic solvent-resistant self-supporting hydrogel membrane based on phenolic compound-metal ion coordination modification according to claim 1, characterized in that: The phenolic compounds mentioned are one or more of the following: dopamine hydrochloride, tannic acid, catechol, caffeic acid, ferric titanate, anthocyanins, proanthocyanidins, tannins, cinnamic acid, chinocanaic acid, chlorogenic acid, caustic acid, tea polyphenols, grape seed polyphenols, agrimony, sanguisorbin, rose extract, anthocyanins, catechins, epicatechin, geranium extract, cinnamic acid, evening primrose extract, astaxanthin, pungent extract, cornus extract, quercetin, gallic acid, and ellagic acid.

3. The method for preparing an organic solvent-resistant self-supporting hydrogel membrane based on phenolic compound-metal ion coordination modification according to claim 1, characterized in that: The metal salt is one or more of the following: calcium chloride, calcium sulfate, magnesium sulfate, magnesium chloride, ferric chloride, ferric sulfate, copper chloride, copper sulfate, manganese sulfate, manganese chloride, zinc chloride, zinc sulfate, barium sulfate, and barium chloride.