A production method of a composite scale-inhibiting reverse osmosis membrane

Abstract

The application provides a production method of a composite scale-inhibiting reverse osmosis membrane, comprising the following steps: step one, providing a non-woven fabric support base material; step two, providing a high-molecular polymer solution, and making the high-molecular polymer in the high-molecular polymer solution combine with the surface of the non-woven fabric support base material to form a polymer porous support base layer through liquid-solid phase conversion; step three, preparing a desalination layer on the polymer porous support base layer; and step four, providing a scale inhibitor system solution, coating the scale inhibitor system solution on the surface of the desalination layer, and combining with the surface of the desalination layer to form a scale inhibition layer after dehydration. Compared with a traditional reverse osmosis membrane, the application adds a scale inhibition layer, so that a scale inhibitor does not need to be added in a water treatment process; compared with the slow forming speed of a traditional scale inhibitor, the application adopts DMTMM as a catalyst to rapidly react polyaspartic acid with a crosslinking agent, forms a stable structure on the surface of the desalination layer, and has the advantages of saving energy and reducing consumption.

Description

Technical Field

[0001] This invention relates to the field of reverse osmosis membrane production technology, and in particular to a method for producing a composite scale-inhibiting reverse osmosis membrane. Background Technology

[0002] Currently, reverse osmosis membrane technology is widely used in water treatment, including water purification, industrial water treatment, ultrapure water production, and seawater desalination. To ensure the long-term stable operation of reverse osmosis membranes, scale inhibitors are commonly used to prevent scaling on the membrane surface, which could lead to a decrease in reverse osmosis efficiency. The significance of scale inhibitors is mainly reflected in the following aspects:

[0003] 1. Inhibit crystallization and scaling: Scale inhibitors react chemically with hardness ions such as calcium and magnesium in the water, as well as other ions that are prone to scaling, to form stable soluble complexes, thereby preventing these ions from depositing as hard scale on the surface of the reverse osmosis membrane.

[0004] 2. Dispersing microcrystals: For microcrystals that have already formed, scale inhibitors can be adsorbed on their surface, changing the growth pattern and morphology of the crystals, making them less likely to aggregate and grow, thereby preventing them from adhering and accumulating on the reverse osmosis membrane surface;

[0005] 3. Improve water production and quality: Effective use of scale inhibitors can significantly reduce scaling on the membrane surface, maintain good permeability of membrane elements, and thus improve the water production and quality of the reverse osmosis system.

[0006] 4. Extend membrane lifespan: Antiscalants can reduce membrane damage caused by scaling, thereby extending the lifespan of reverse osmosis membranes;

[0007] 5. Energy saving and consumption reduction: By reducing the frequency of cleaning and membrane replacement due to scaling, the use of scale inhibitors reduces operating costs and energy consumption.

[0008] 6. Equipment protection: Scale inhibitors can prevent equipment damage caused by scaling, such as clogging or corrosion of pressure vessels, pipelines and reverse osmosis membrane components, and ensure the long-term stable operation of the entire reverse osmosis water treatment system.

[0009] Commonly used scale inhibitors mainly include the following types:

[0010] 1. Organophosphonate scale inhibitors: Common examples include hydroxyethylidene diphosphine (HEDP) and aminotrimethylene phosphonic acid (ATMP). These scale inhibitors can form stable complexes with hardness ions such as calcium and magnesium in water, preventing them from forming scale on the membrane surface.

[0011] 2. Polycarboxylic acid scale inhibitors: such as polyacrylic acid (PAA) and polyaspartic acid (PASP). These scale inhibitors prevent hardness ions in the water from depositing on the membrane surface through dispersion.

[0012] 3. Inorganic salt scale inhibitors: such as silicates and polyphosphates (including sodium tripolyphosphate, sodium hexametaphosphate, etc.). Silicates can form a protective film on metal surfaces to reduce corrosion; polyphosphates, on the other hand, prevent scale crystal growth by reacting with calcium and magnesium ions in water.

[0013] 4. Organic polyphosphonic acid scale inhibitors: such as ATMP (aminotrimethylenephosphonic acid) and HEDP (hydroxyethylidene diphosphonic acid). These agents have good chelating ability and can effectively complex metal ions, preventing them from combining with anions to form insoluble precipitates.

[0014] However, using scale inhibitors in reverse osmosis membranes has the following drawbacks: 1. Increased cost: The preparation of scale inhibitors requires advanced chemical formulations and processes, resulting in relatively high prices and increasing water treatment costs. 2. Risk of overuse: Excessive use of scale inhibitors can alter the chemical composition and pH value of the water, potentially affecting the treatment efficiency of the reverse osmosis system and shortening its lifespan. 3. Potential environmental impact: Some chemicals contained in scale inhibitors may pose minor health risks to humans and the environment (especially those containing phosphorus and polyacrylic acid).

[0015] In conclusion, the use of appropriate scale inhibitors is an essential step in water treatment processes using reverse osmosis membranes. However, traditional production processes have many shortcomings (economic efficiency and water quality compatibility). Therefore, integrated composite scale-inhibiting reverse osmosis water purification membranes have great practical value and application market potential.

[0016] Chinese invention patent application CN114162980B discloses a reverse osmosis membrane antiscalant and its preparation method. The antiscalant comprises 20-30 parts polyaspartic acid, 20-30 parts tannin, 10-20 parts alkyl epoxy carboxylate, 8-12 parts non-oxidizing bactericide, and 100 parts deionized water. The polyaspartic acid is sulfonic acid-modified polyaspartic acid. The preparation method optimizes the order of addition of each component and the pH value of the antiscalant, ensuring effective and uniform dispersion of each component and improving their stability. However, this patented antiscalant and reverse osmosis membrane are manufactured separately, resulting in lower economic efficiency and limiting its application in more fields.

[0017] Chinese invention patent application CN113908705A discloses a high-flux inorganic scaling-resistant, moderately desalinated nanofiltration membrane and its preparation method. Specifically, it involves treating a polymer-based membrane with an aqueous amine solution, an oil solution, and a dimethylformamide solution. Through a specific component ratio in the aqueous amine and oil solutions, the prepared high-flux inorganic scaling-resistant, moderately desalinated nanofiltration membrane exhibits higher permeate flow rate under the same operating pressure compared to traditional nanofiltration and reverse osmosis membranes, achieving moderate desalination and improved resistance to inorganic scaling. However, the reagents used in this method are ether-based, and the small equivalent amount is insufficient to maintain long-term stability at high flux, thus lacking long-term stable use value. Summary of the Invention

[0018] The technical problem to be solved by the embodiments of the present invention is to provide a method for producing a composite antiscaling reverse osmosis membrane, thereby solving the problem that existing reverse osmosis membranes require the separate addition of antiscalants during water treatment.

[0019] To address the aforementioned technical problems, this invention provides a method for producing a composite scale-inhibiting reverse osmosis membrane, comprising:

[0020] Step 1: Provide a non-woven fabric support substrate;

[0021] Step 2: Provide a polymer solution and allow the polymer solution to bond to the surface of the nonwoven support substrate through a liquid-solid phase transformation to form a porous polymer support base layer.

[0022] Step 3: Prepare a desalination layer on the polymer porous support substrate;

[0023] Step 4: Provide a scale inhibitor system solution, coat the scale inhibitor system solution on the surface of the desalination layer, and after dehydration, combine it with the surface of the desalination layer to form a scale inhibitor layer.

[0024] The nonwoven fabric support substrate is made of polyester substrate produced by wet processing.

[0025] The polymer solution is composed of a polymer and a solvent, and its components, calculated by mass percentage concentration, include: 15-20% polymer and 80-85% solvent; wherein the polymer is polysulfone and the solvent is dimethylformamide (DMF).

[0026] The steps for preparing a polymer mixture solution include: adding the polymer to a solvent according to the mass ratio, stirring at 100-140℃ for 6-12 hours until the polymer is completely dissolved to form a primary solution; then evacuating the primary solution and maintaining it for 10-12 hours to obtain the polymer mixture solution.

[0027] Step two also includes immersing the prepared polymer porous support base layer in deionized water, so that the solvent dissolves in the deionized water and separates from the polymer porous support base layer, forming a mixed waste liquid of deionized water and solvent, and then recycling the mixed waste liquid for reuse.

[0028] The recycling and reuse of mixed waste liquid includes:

[0029] Step A: The mixed waste liquid is concentrated by passing it through a reverse osmosis membrane to form a concentrated liquid with a higher solvent concentration, and deionized water is separated.

[0030] Step B: Separate the concentrate obtained in Step A by distillation to obtain high-purity DMF and deionized water;

[0031] Step C: Mix the high-purity DMF and polymer obtained in step B, heat, and vacuum to prepare a polymer solution; at the same time, use the deionized water obtained in steps A and B to soak the porous polymer support layer, thereby realizing the full recycling of DMF and deionized water.

[0032] Step three, which involves preparing a desalination layer on a polymer porous support substrate, includes:

[0033] The nonwoven support substrate with a polymer porous support layer obtained in step two is successively treated with an aqueous amine solution and an oil solution, followed by heat treatment, washing with pure water, and then soaking in a humectant glycerin and drying.

[0034] The heat treatment refers to heating the polymer porous support base layer to 60-100℃ and then cooling it to room temperature.

[0035] Specifically, the process involves: immersing a nonwoven support substrate with a polymer porous support layer on its surface in an aqueous amine solution for 0.3-5 minutes, and squeezing out excess aqueous phase; then coating the polymer porous support substrate with an oil phase solution for 0.3-2 minutes to perform an interfacial reaction; followed by immersion in an alkaline solution for 0.5-2 minutes for alkaline washing, immersion in hot water for 10-30 minutes for setting, and glycerin for 0.5-2 minutes for moisturizing to form a desalination layer.

[0036] The aqueous amine solution comprises, by mass percentage concentration: 1.5-4.5% m-phenylenediamine, 1-5% triethylamine hydrochloride, 0.01-0.05% sodium hydroxide, and 0.01-0.2% sodium bisulfite.

[0037] The oil phase solution comprises, by mass percentage concentration: 0.1-0.28% pyromellitic methyl chloride, 0.6-1% tripropyl phosphate, and the balance being the organic solvent ISOPAR M.

[0038] The scale inhibitor system solution is composed of polyaspartic acid, hexamethylenediamine / pentanediamine, potassium dihydrogen phosphate / tripotassium phosphate, catalyst, and pure water. Its composition, calculated by mass percentage, is as follows: polyaspartic acid 0.1-2%, hexamethylenediamine / pentanediamine 0.1-1%, potassium dihydrogen phosphate / tripotassium phosphate 0.01-0.1%, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) 0.1%-1%, with the balance being pure water.

[0039] Polyaspartic acid is used as the film-forming material, hexamethylenediamine / pentanediamine is used as the crosslinking agent, and potassium dihydrogen phosphate / tripotassium phosphate is used as the buffer.

[0040] The coating thickness of the scale inhibitor system solution is 15-80 μm; after coating, it is dried in an environment of 60-100℃ for 1-5 minutes to allow the scale inhibitor system solution to form a scale inhibitor layer on the surface of the desalination layer. The reaction formula is as follows:

[0041]

[0042] The present invention also provides a composite scale-inhibiting reverse osmosis membrane, comprising: a non-woven fabric support substrate, a polymer porous support base layer, a desalination layer, and a scale-inhibiting layer, wherein the polymer porous support base layer is formed on the surface of the non-woven fabric support substrate, the desalination layer is formed on the surface of the polymer porous support base layer, and the scale-inhibiting layer is formed on the surface of the desalination layer.

[0043] The nonwoven fabric support substrate is made of polyester substrate produced by wet processing.

[0044] The polymer porous support base layer is formed by bonding the polymer mixture to the surface of the nonwoven support substrate through a liquid-solid phase transformation on the nonwoven support substrate.

[0045] The polymer solution is composed of a polymer and a solvent, and its components, calculated by mass percentage concentration, include: 15-20% polymer and 80-85% solvent; wherein the polymer is polysulfone and the solvent is dimethylformamide.

[0046] The scale inhibitor layer is formed by coating the surface of the desalination layer with a scale inhibitor system solution. After heating and dehydration, polyaspartic acid and hexamethylenediamine / pentanediamine undergo a cross-linking reaction under the action of a catalyst, thereby forming a scale inhibitor layer on the surface of the desalination layer.

[0047] Compared to traditional reverse osmosis membranes, this invention adds a scale inhibitor layer, thus eliminating the need to add scale inhibitors during water treatment. In contrast to the slow molding speed of traditional scale inhibitors, this invention uses DMTMM as a catalyst to rapidly react polyaspartic acid with a crosslinking agent, molding it onto the surface of the desalination layer to form a stable structure.

[0048] The method for producing a composite scale-inhibiting reverse osmosis water purification membrane provided by this invention forms a scale-inhibiting layer on the surface of the desalination layer of the reverse osmosis membrane. This method offers greater economic efficiency in the water purification field and maximizes space utilization for home users. Compared to other similar technologies that add insufficient scale inhibitors to the desalination or polysulfone layers, which are prone to loss, this method ensures continuous system stability. This invention employs a quantitative coating of cross-linked grafts to form the scale-inhibiting layer on the desalination layer, achieving effective scale inhibition (-CONH-, preventing aggregation, sedimentation, and dissolution through complexation) and long-term operational stability (due to the condensation grafting of amino groups with the carboxyl groups of the third polyamide membrane, as well as the electrostatic adsorption effect of residual end groups).

[0049] In this invention, a polyamide reverse osmosis membrane is first formed through solid-liquid phase transformation and interfacial polymerization. Then, a mixed solution containing polyaspartic acid, hexamethylenediamine / pentanediamine, buffer, and catalyst (DMTMM) is coated onto the desalination layer. Under weakly alkaline, high-temperature thermal crosslinking reaction, an integrated composite scale-inhibiting reverse osmosis water purification membrane scale inhibitor layer is formed. The crosslinked polyaspartic acid molecule contains alternating polyamide bonds, which can complex calcium and magnesium ions in the operating water, effectively reducing flux reduction and clogging caused by ion precipitation. Through the electrostatic interaction of the carboxyl and amino groups on the polyamide bonds, the attractive force between particles is reduced, preventing aggregation and deposition. The molecule exists in a chain structure, which can adsorb particles deposited in the water, inhibit their growth, and dissolve together in the water after adsorption. This greatly delays the degradation of membrane performance and improves long-term operational stability.

[0050] This invention involves coating a polyester substrate with a polymer solution composed of polysulfone and DMF using a wet process, obtaining a porous polymer support layer formed of polysulfone through a solid-liquid phase separation method, and then cleaning and heat-setting the substrate.

[0051] Then, through the interfacial crosslinking reaction of aqueous phase and oil phase impregnation, followed by heat treatment, pure water washing, heat setting, and humectant protection, a desalination layer formed of polyamide is obtained.

[0052] A scale inhibitor system solution with scale inhibition function is quantitatively coated on the front side of the desalination layer and crosslinked by catalytic heat treatment under weak alkaline and high temperature conditions to form a composite scale-inhibiting reverse osmosis water purification membrane with surface scale inhibition function.

[0053] This invention also provides a formulation for a scale inhibitor system solution capable of forming a scale inhibitor layer, solving the problem that existing reverse osmosis membranes cannot form a stable scale inhibitor layer on the surface of the desalination layer.

[0054] The formulation of the scale inhibitor system solution capable of forming a scale inhibitor layer provided by the present invention is composed of polyaspartic acid, crosslinking agent, buffer, catalyst and pure water, wherein the catalyst is 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM).

[0055] The polyaspartic acid has a mass percentage of 0.1-2%;

[0056] The catalyst has a mass percentage content of 0.1-1%;

[0057] The crosslinking agent is hexamethylenediamine or pentanediamine, with a mass percentage content of 0.1-1%;

[0058] The buffer is potassium dihydrogen phosphate or tripotassium phosphate, with a mass percentage content of 0.1-1%;

[0059] The remainder is pure water.

[0060] The present invention also provides a method for molding a scale inhibitor system solution onto a reverse osmosis membrane, comprising:

[0061] Provide a reverse osmosis membrane carrier with a desalination layer surface;

[0062] The scale inhibitor system solution is coated onto the surface of the desalination layer, and then heated to form a scale inhibitor layer on the surface of the desalination layer.

[0063] The coating thickness is 15-80 μm, the heating temperature is 60-100℃, and the heating time is 15 min.

[0064] The scale inhibitor solution forms a scale inhibitor layer on the surface of the desalination layer, and the reaction formula is as follows:

[0065]

[0066] The heating is carried out in an oven.

[0067] Methods for providing a reverse osmosis membrane carrier having a desalination layer surface include:

[0068] Step 1: Provide a non-woven fabric support substrate;

[0069] Step 2: Provide a polymer solution and allow the polymer solution to bond to the surface of the nonwoven support substrate through a liquid-solid phase transformation to form a porous polymer support base layer.

[0070] Step 3: Prepare a desalination layer on the polymer porous support base layer.

[0071] The present invention also provides a reverse osmosis membrane, which is manufactured using the method described above of forming a scale inhibitor system solution onto a reverse osmosis membrane.

[0072] The present invention also provides a scale inhibitor system solution capable of forming a scale inhibitor layer, which uses DMTMM as a catalyst to significantly accelerate the cross-linking reaction rate of polyaspartic acid on the surface of the desalination layer, and to form a stable connection between the scale inhibitor layer and the desalination layer during the reaction process. The formed scale inhibitor layer can be continuously and stably connected to the desalination layer, thereby maintaining the scale inhibition effect.

[0073] Compared to traditional reverse osmosis membranes, this invention adds a scale inhibitor layer, thus eliminating the need to add scale inhibitors during water treatment. In contrast to the slow molding speed of traditional scale inhibitors, this invention uses DMTMM as a catalyst to rapidly react polyaspartic acid with a crosslinking agent, molding it onto the surface of the desalination layer to form a stable structure. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the overall process structure in an embodiment of the present invention.

[0075] In the picture:

[0076] 1-Non-woven fabric support substrate; 2-Porous polymer support base layer; 3-Desalination layer; 4-Scale inhibition layer. Detailed Implementation

[0077] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0079] This invention provides a method for producing a composite scale-inhibiting reverse osmosis membrane, comprising:

[0080] Step 1: Provide a non-woven fabric support substrate; the non-woven fabric support substrate is a wet-process polyester substrate.

[0081] Step 2: Provide a polymer solution and apply it to a nonwoven support substrate via a liquid-solid phase transformation to form a porous polymer support layer on the surface of the substrate. The polymer solution consists of a polymer and a solvent, with the components comprising, by mass percentage concentration: 15-20% polymer and 80-85% solvent; the polymer is polysulfone, and the solvent is dimethylformamide (DMF). The steps for preparing the polymer mixture solution include: adding the polymer to the solvent according to the mass ratio, stirring at 100-140℃ for 6-12 hours until the polymer is completely dissolved to form a primary solution; then evacuating the primary solution and maintaining the vacuum for 10-12 hours to obtain the polymer mixture solution. In step two, generally, the higher the temperature, the less time is required for stirring. For example, the stirring temperature can be 100℃, 110℃, 120℃, 130℃, or 140℃, and the corresponding stirring time can be 12 hours, 11 hours, 10 hours, 9 hours, 8 hours, 7 hours, or 6 hours. The vacuum holding time can be selected as 10 hours, 11 hours, or 12 hours depending on the implementation situation.

[0082] Step 3: Prepare a desalination layer on the polymer porous support layer, including:

[0083] The nonwoven support substrate with a polymer porous support layer obtained in step two is successively washed with aqueous amine solution, oil solution, and alkali, then washed with pure water, heat-treated, rinsed with pure water, and then soaked in glycerin moisturizer and dried.

[0084] Specifically, the process involves: immersing a nonwoven support substrate with a polymer porous support layer on its surface in an aqueous amine solution for 0.3-5 minutes, and squeezing out excess aqueous phase; then coating the polymer porous support substrate with an oil phase solution for 0.3-2 minutes to perform an interfacial reaction; followed by immersion in an alkaline solution for 0.5-2 minutes for alkaline washing, immersion in hot water for 10-30 minutes for setting, and glycerin for 0.5-2 minutes for moisturizing to form a desalination layer.

[0085] The aqueous amine solution comprises, by mass percentage concentration: 1.5-4.5% m-phenylenediamine, 1-5% triethylamine hydrochloride, 0.01-0.05% sodium hydroxide, and 0.01-0.2% sodium bisulfite. The values ​​of m-phenylenediamine can be 1.5%, 1%, 2.5%, 3%, 3.5%, 4%, or 4.5%; the values ​​of triethylamine hydrochloride can be 1%, 2%, 3%, 4%, or 5%; the values ​​of sodium hydroxide can be 0.01%, 0.02%, 0.03%, 0.04%, or 0.05%; and the values ​​of sodium bisulfite can be 0.01%, 0.05%, 0.1%, 0.15%, or 0.2%.

[0086] The oil phase solution comprises, by mass percentage concentration: 0.1-0.28% trimesoyl chloride, 0.6-1% tripropyl phosphate, and the balance being the organic solvent ISOPAR M. The trimesoyl chloride can be 0.1%, 0.15%, 0.18%, 0.2%, 0.24%, or 0.28%; the tripropyl phosphate can be 0.6%, 0.7%, 0.8%, 0.9%, or 1%.

[0087] The heat treatment temperature can be 60-100℃; the heat treatment time can be 1min-30min. The above-mentioned heat curing temperature and time are more conducive to further improving the crosslinking density of the coating, and more conducive to further enhancing the stability and adhesion between coatings.

[0088] Step 4: Provide a scale inhibitor system solution, coat the scale inhibitor system solution on the surface of the desalination layer, and after dehydration, combine it with the surface of the desalination layer to form a scale inhibitor layer.

[0089] The scale inhibitor system solution is composed of polyaspartic acid, hexamethylenediamine / pentanediamine, potassium dihydrogen phosphate / tripotassium phosphate, catalyst, and pure water. Its composition, calculated by mass percentage, is as follows: polyaspartic acid 0.1-2%, hexamethylenediamine / pentanediamine 0.1-1%, potassium dihydrogen phosphate / tripotassium phosphate 0.01-0.1%, 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) 0.1%-1%, with the balance being pure water. The values ​​for polyaspartic acid can be 0.1%, 1.5%, or 2%; the values ​​for hexamethylenediamine / pentanediamine can be 0.1%, 0.4%, 0.6%, 0.8%, or 1%; the values ​​for potassium dihydrogen phosphate / tripotassium phosphate can be 0.01%, 0.05%, 0.08%, or 0.1%; and the values ​​for 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) can be 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, or 1%.

[0090] The coating thickness of the scale inhibitor system solution is 15-80 μm; after coating, it is dried in an environment of 60-100°C for 1-5 minutes to form a scale inhibitor layer on the surface of the polymer porous support substrate.

[0091] Step two also includes immersing the prepared polymer porous support base layer in deionized water, so that the solvent dissolves in the deionized water and separates from the polymer porous support base layer, forming a mixed waste liquid of deionized water and solvent, and then recycling the mixed waste liquid for reuse.

[0092] The recycling and reuse of mixed waste liquid includes:

[0093] Step A: The mixed waste liquid is concentrated by passing it through a reverse osmosis membrane to form a concentrated liquid with a higher solvent concentration, and deionized water is separated.

[0094] Step B: Separate the concentrate obtained in Step A by distillation to obtain high-purity DMF and deionized water;

[0095] Step C: Mix the high-purity DMF and polymer obtained in step B, heat, and vacuum to prepare a polymer solution; at the same time, use the deionized water obtained in steps A and B to soak the porous polymer support layer, thereby realizing the full recycling of DMF and deionized water.

[0096] The recycling and utilization method for mixed waste liquid can ensure that all DMF and deionized water can be recycled in the production process, avoiding the discharge of DMF wastewater and preventing environmental pollution.

[0097] In a preferred embodiment, the preparation method of the present invention includes the following steps:

[0098] 15-20% polysulfone was dissolved in dimethylformamide (DMF) solvent at 120℃ and coated 40 micrometers onto a 100-micrometer thick nonwoven fabric support substrate (polyester PET nonwoven fabric). A solid porous supported polysulfone film (polymer porous support base layer) was formed by liquid-solid phase separation. After cleaning and heat setting, the film was dipped into an aqueous phase amine solution (1.5-4.5% m-phenylenediamine, 1-5% triethylamine hydrochloride, 0.01-0.05% sodium hydroxide, 0.01-0.2% sodium bisulfite) and an oil phase solvent (0.1-0.28% pyromellitic acid chloride, 0.6-1% tripropyl phosphate, and the balance of ISOPAR M organic solvent). Interfacial polymerization was carried out, followed by treatment in a hot oven for 3 minutes, rinsing in a water bath for 5 minutes, and wetting with a humectant to obtain a 0.2-0.4 micrometer polyamide desalination layer. Then, a scale inhibitor solution (0.1-2% polyaspartic acid, 0.1-1% hexamethylenediamine / pentanediamine, 0.01-0.1% potassium dihydrogen phosphate / tripotassium phosphate buffer, 0.1%-1% 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) catalyst, with pure water as the balance) is coated onto the surface of the desalination layer. This solution is then cross-linked in a weak alkali environment and a 70°C oven for 3 minutes to form a scale inhibitor layer of 1-4 micrometers. The cross-linked polyaspartic acid molecule contains alternating polyamide bonds, which can complex calcium and magnesium ions in the operating water, effectively reducing flux reduction and clogging caused by ion precipitation. Furthermore, the electrostatic interaction between the carboxyl and amino groups on the polyamide bonds reduces the attraction between particles, preventing aggregation and deposition. Simultaneously, the molecule exists in a chain structure, capable of adsorbing deposited particles in the water, inhibiting their growth, and dissolving together in water after adsorption, thus forming an integrated composite scale inhibitor reverse osmosis water purification membrane.

[0099] Example 1 (Blank Example)

[0100] In this embodiment 1, a method for preparing and applying an integrated composite scale-inhibiting reverse osmosis membrane is provided, including the following steps:

[0101] Nonwoven support substrate provided: 100μm thickness, 75g / m² weight 3 Breathability: 3cc / cm² / sec;

[0102] Preparation of polymer porous support base layer: 17% polysulfone was dissolved in dimethylformamide (DMF) solvent at 120℃ and high speed stirring for 8h, vacuum static pressure for 10h, and coated 40 microns onto 100 microns polyester PET nonwoven fabric. Through liquid-solid phase separation method, and after cleaning and quenching (heated to 80℃ and then cooled to room temperature), a solid porous support polysulfone base film was formed.

[0103] Prepare an aqueous amine solution by mixing 3% m-phenylenediamine, 3% triethylamine hydrochloride, 0.02% sodium hydroxide, 0.05% sodium bisulfite, and pure water.

[0104] Prepare the oil phase solution: 0.2% pyromellitic methyl chloride, 0.8% tripropyl phosphate, and ISOPAR M organic solvent.

[0105] Preparation of desalination layer (interfacial polymerization): The polymer porous support base layer is immersed in an aqueous amine solution for 1 min and then removed. Excess amine solution is removed with nitrogen or a rubber roller, and then immersed in an oil phase solution for 1 min and removed.

[0106] Oven heat treatment: The product after interfacial polymerization is placed in an oven for heat treatment. The heat treatment temperature is 70℃ and the heat treatment time is 5min to improve the crosslinking density of the coating and enhance the stability and adhesion of the coating.

[0107] Water tank cleaning process: After heat treatment, the product is rinsed with hot pure water for 5 minutes and soaked in a moisturizer for 2 minutes.

[0108] Heat drying treatment: Drying in a 70℃ oven for 3 minutes to form a conventional reverse osmosis membrane.

[0109] Example 2 (Preferred Example)

[0110] The difference between Example 2 and Example 1 is that, after the heat drying treatment in Example 1, the scale inhibitor system solution is coated on the reverse osmosis membrane after S7 cleaning, and crosslinked in a 70°C oven for 3 minutes to form a scale inhibitor layer with a diameter of 2 micrometers; the scale inhibitor system solution consists of the following components: 0.3% polyaspartic acid, 0.1% crosslinking agent hexamethylenediamine, 0.02% buffer potassium dihydrogen phosphate / tripotassium phosphate, 0.1%-1% catalyst 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM), and the balance being pure water.

[0111] Example 3

[0112] The difference between Example 3 and Example 2 is that 0.1% pentanediamine is used instead of hexanediamine, thereby obtaining a scale inhibitor layer with a diameter of 2 micrometers through heat treatment crosslinking.

[0113] The remaining steps are the same as in Example 2, resulting in an integrated composite scale-inhibiting reverse osmosis water purification membrane.

[0114] Example 4

[0115] The difference between Example 4 and Example 2 is that, after heat drying, a cross-linking grafting reaction was carried out using a concentration of 0.1% polyaspartic acid.

[0116] The remaining steps are the same as in Example 2, resulting in an integrated composite scale-inhibiting reverse osmosis water purification membrane.

[0117] Example 5

[0118] The difference between Example 5 and Example 2 is that, after heat drying, a cross-linking grafting reaction was carried out using a concentration of 0.5% polyaspartic acid.

[0119] The remaining steps are the same as in Example 2, resulting in an integrated composite scale-inhibiting reverse osmosis water purification membrane.

[0120] Example 6

[0121] The difference between Example 6 and Example 2 is that after heat drying, the cross-linking grafting reaction is carried out in a 50°C oven for 3 minutes.

[0122] The remaining steps are the same as in Example 2, resulting in an integrated composite scale-inhibiting reverse osmosis water purification membrane.

[0123] Example 7

[0124] The difference between Example 7 and Example 2 is that after heat drying, the cross-linking grafting reaction is carried out in a 90°C oven for 3 minutes.

[0125] The remaining steps are the same as in Example 2, resulting in an integrated composite scale-inhibiting reverse osmosis water purification membrane.

[0126] Initial performance and scale inhibition performance testing and evaluation

[0127] The scale-inhibiting reverse osmosis water purification membranes prepared in the examples were subjected to desalination, flux, water efficiency life and scale inhibition tests, respectively.

[0128] I. Initial Performance

[0129] The integrated composite scale-inhibiting reverse osmosis water purification membranes prepared according to the methods of Examples 1-7 were cut separately, with DuPont Dow reverse osmosis water purification membrane XLE as a commercial comparative example; the membranes were placed on a cross-flow membrane test platform for initial membrane performance testing: the operating pressure was 0.69 MPa, the test solution was 2 g / L sodium chloride solution, the solution temperature was 25℃, the pH was 7-8, and the water flux and desalination rate were tested after the membranes had been running for 30 min; the test results are shown in Table 1.

[0130] Table 1: Performance Tests of Sodium Chloride

[0131] Experimental subjects Flux (LMH) Desalination rate (%) Example 1 (Blank Example) 61.5 97 Example 2 (Preferred Example) 55.7 98.5 Example 3 52.3 98.6 Example 4 57.2 98 Example 5 50.6 98.7 Example 6 59.6 97.5 Example 7 53.2 98.5 Business Comparison 50 98.3

[0132] The test results show that the scale-inhibiting reverse osmosis water purification membrane prepared by the method described in this patent has a higher flux than commercial reverse osmosis water purification membranes, and the desalination rate is stable at over 98%.

[0133] II. Water Efficiency Life Operation Test - Scale Inhibition Effect

[0134] Flux decay rate tests were conducted on the membranes in Table 1. The original aqueous solution was prepared according to the test water standard of GB34914-2017 "Water Efficiency Limits and Water Efficiency Grades for Reverse Osmosis Water Purifiers". The initial flux and initial desalination rate of the membranes were tested at an operating pressure of 0.69 MPa, a solution temperature of 25℃, and a pH of 7-8. After continuous operation for 48 hours, the water flux and desalination rate of the membranes were tested again. The flux decay rate of the membranes was calculated, and the results are shown in Table 2.

[0135] Among them, flux decay rate = (initial water flux - end-of-operation water flux) / initial water flux * 100%, desalination decay rate = (initial desalination rate - end-of-operation desalination rate) / initial desalination rate * 100%;

[0136] Table 2: Membrane Water Efficiency Life Operation Test

[0137]

[0138] The test results show that, after 24 hours of operation, the integrated composite scale-inhibiting reverse osmosis water purification membrane prepared by the method described in this patent has lower flux and desalination rate than commercial reverse osmosis water purification membranes, but better initial performance, indicating excellent scale inhibition performance.

[0139] This invention employs an integrated, quantitatively coated, cross-linked graft onto the desalination layer. The cross-linked polyaspartic acid molecule contains alternating polyamide bonds, which effectively complex calcium and magnesium ions in the operating water, reducing flux reduction and clogging caused by ion precipitation. Furthermore, through the electrostatic interaction of the carboxyl and amino groups on the polyamide bonds, the attractive force between particles is reduced, preventing aggregation and deposition. Simultaneously, the molecule exists in a chain structure, capable of adsorbing micro-deposited scale in the water, inhibiting its growth, and dissolving together with it after adsorption, thus forming an integrated, composite scale-inhibiting reverse osmosis water purification membrane.

[0140] The method for producing a composite scale-inhibiting reverse osmosis water purification membrane provided by this invention forms a scale-inhibiting layer on the surface of the desalination layer of the reverse osmosis membrane. This method offers greater economic efficiency in the water purification field and maximizes space utilization for home users. In contrast, other patents that add only small amounts of scale inhibitors to the desalination or polysulfone layers are insufficient and prone to loss, failing to guarantee continuous system stability. This invention employs a quantitative coating of cross-linked grafts to form the scale-inhibiting layer on the desalination layer, achieving effective scale inhibition (-CONH-, preventing aggregation, sedimentation, and dissolution through complexation) and long-term operational stability (due to the condensation grafting of amino groups with the carboxyl groups of the third polyamide membrane, as well as the electrostatic adsorption effect of residual end groups).

[0141] like Figure 1 As shown, this embodiment of the invention also provides a composite scale-inhibiting reverse osmosis water purification membrane, comprising: a non-woven fabric support substrate 1, a polymer porous support base layer 2, a desalination layer 3, and a scale-inhibiting layer 4, wherein the polymer porous support base layer is formed on the surface of the non-woven fabric support substrate, the desalination layer is formed on the surface of the polymer porous support base layer, and the scale-inhibiting layer is formed on the surface of the desalination layer.

[0142] The nonwoven fabric support substrate is made of wet-process polyester substrate, with a thickness of 100μm and a weight of 75g / m². 3 Breathability is 3cc / cm² / sec.

[0143] The polymer porous support layer is formed by bonding the polymer mixture to the surface of the nonwoven support substrate through a liquid-solid phase transformation. The thickness of the polymer porous support layer is 40 micrometers.

[0144] The polymer solution is composed of a polymer and a solvent, and its components, calculated by mass percentage concentration, include: 15-20% polymer and 80-85% solvent; wherein the polymer is polysulfone and the solvent is dimethylformamide.

[0145] The desalination layer is 0.2-0.4 micrometers thick.

[0146] The scale inhibitor layer is formed by coating the surface of the desalination layer with a scale inhibitor solution, which is then dehydrated and bonded to the surface of the desalination layer. The thickness of the scale inhibitor layer is 1-4 micrometers.

[0147] The present invention also provides a formulation of a scale inhibitor system solution capable of forming a scale inhibitor layer, which is composed of polyaspartic acid, crosslinking agent, buffer, catalyst and pure water, wherein the catalyst is 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM).

[0148] This invention primarily utilizes 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride (DMTMM) as a catalyst to catalyze the crosslinking reaction of polyaspartic acid and a crosslinking agent, significantly accelerating the reaction rate. The crosslinked polyaspartic acid molecule contains alternating polyamide bonds, which effectively complex calcium and magnesium ions in the operating water, reducing flux reduction and clogging caused by ion precipitation. Through electrostatic interactions caused by the charges of the carboxyl and amino groups on the polyamide bonds, the attractive force between particles is reduced, preventing aggregation and deposition. The molecule exists in a chain structure, capable of adsorbing deposited particles in the water, inhibiting their growth, and dissolving together in water after adsorption. This significantly delays membrane performance degradation and improves long-term operational stability.

[0149] The mass percentage of the polyaspartic acid is 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or other values ​​between 0.1% and 2%.

[0150] The catalyst has a mass percentage content of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, 1%, or other values ​​between 0.1% and 1%.

[0151] The crosslinking agent is hexamethylenediamine or pentanediamine, with a mass percentage content of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, 1%, or other values ​​between 0.1% and 1%.

[0152] The buffer is potassium dihydrogen phosphate or tripotassium phosphate, with a mass percentage content of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.7%, 0.8%, 1%, or other values ​​between 0.1% and 1%.

[0153] The remainder is pure water.

[0154] The present invention also provides a method for molding a scale inhibitor system solution onto a reverse osmosis membrane, comprising:

[0155] Provide a reverse osmosis membrane carrier with a desalination layer surface;

[0156] The scale inhibitor system solution is coated onto the surface of the desalination layer, and then heated to form a scale inhibitor layer on the surface of the desalination layer.

[0157] The coating thickness is 15-80 μm, the heating temperature is 60-100℃, and the heating time is 15 min.

[0158] The scale inhibitor solution forms a scale inhibitor layer on the surface of the desalination layer, and the reaction formula is as follows:

[0159]

[0160] The heating is carried out in an oven.

[0161] A method for providing a reverse osmosis membrane carrier having a desalination layer surface can be referred to in the above embodiments, including:

[0162] Step 1: Provide a non-woven fabric support substrate;

[0163] Step 2: Provide a polymer solution and allow the polymer solution to bond to the surface of the nonwoven support substrate through a liquid-solid phase transformation to form a porous polymer support base layer.

[0164] Step 3: Prepare a desalination layer on the polymer porous support base layer.

[0165] The present invention also provides a reverse osmosis membrane, which is manufactured using the method described above of forming a scale inhibitor system solution onto a reverse osmosis membrane.

[0166] The present invention also provides a scale inhibitor system solution capable of forming a scale inhibitor layer, which uses DMTMM as a catalyst to significantly accelerate the cross-linking reaction rate of polyaspartic acid on the surface of the desalination layer, and to form a stable connection between the scale inhibitor layer and the desalination layer during the reaction process. The formed scale inhibitor layer can be continuously and stably connected to the desalination layer, thereby maintaining the scale inhibition effect.

[0167] Compared to traditional reverse osmosis membranes, this invention adds a scale inhibitor layer, thus eliminating the need to add scale inhibitors during water treatment. In contrast to the slow molding speed of traditional scale inhibitors, this invention uses DMTMM as a catalyst to rapidly react polyaspartic acid with a crosslinking agent, molding it onto the surface of the desalination layer to form a stable structure.

[0168] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0169] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for producing a composite scale-inhibiting reverse osmosis water purification membrane, comprising: Step 1, providing a non-woven fabric support substrate; Step 2, providing a high polymer solution, and making the high polymer in the high polymer solution bind to the surface of the non-woven fabric support substrate by liquid-solid phase transformation to form a polymer porous support base layer on the non-woven fabric support substrate; Step 3, preparing a desalination layer on the polymer porous support base layer; Step 4, providing a scale inhibitor system solution, coating the scale inhibitor system solution on the surface of the desalination layer, and combining the scale inhibitor system solution on the surface of the desalination layer to form a scale inhibition layer after dehydration; The scale inhibitor system solution is composed of polyaspartic acid, hexanediamine / pentanediamine, potassium dihydrogen phosphate / tripotassium phosphate, a catalyst, and pure water, wherein the catalyst is 4-(4, 6-dimethoxytriazin-2-yl)-4-methylmorpholine hydrochloride, and the components are calculated according to mass percentage: polyaspartic acid 0.1-2%, hexanediamine / pentanediamine 0.1-1%, potassium dihydrogen phosphate / tripotassium phosphate 0.01-0.1%, 4-(4, 6-dimethoxytriazin-2-yl)-4-methylmorpholine hydrochloride 0.1%-1%, and the balance is pure water; The coating thickness of the scale inhibitor system solution is 15-80um; After the coating is completed, drying is performed at 60-100℃ for 1-5min to make the scale inhibitor system solution form a scale inhibition layer on the surface of the desalination layer. 2.The method according to claim 1, wherein The non-woven fabric support substrate adopts a wet process polyester substrate; The high polymer solution is composed of a high polymer and a solvent, and the components are calculated according to mass percentage concentration and include: high polymer 15-20%, solvent 80-85%; wherein the high polymer is polysulfone, and the solvent is dimethylformamide. 3.The method according to claim 2, wherein The step of configuring the high polymer mixed solution includes: adding the high polymer into the solvent according to mass ratio, stirring at 100-140℃ for 6-12 hours until the high polymer is completely dissolved to form a primary solution; then vacuumizing the primary solution and keeping for 10-12 hours or more to obtain the high polymer mixed solution. 4.The method according to claim 1, wherein Step 2 further includes soaking the prepared polymer porous support base layer in deionized water to make the solvent dissolve in the deionized water and separate from the polymer porous support base layer to form a mixed waste liquid of deionized water and solvent, and then recycling and utilizing the mixed waste liquid; The recycling and utilizing of the mixed waste liquid includes: Step A, concentrating the mixed waste liquid through a reverse osmosis membrane to form a concentrated liquid with higher solvent concentration, and separating the deionized water; Step B, obtaining high-purity DMF and deionized water by distillation separation of the concentrated liquid obtained in step A. Step C, using high-purity DMF obtained in step B and high-molecular polymer mixing, heating, vacuum preparation of high-molecular polymer solution; at the same time, the deionized water obtained in step A and step B is used to soak the polymer porous support base layer, so as to realize the full recycling of DMF and deionized water.

5. The production method according to claim 4, characterized in that, Step three, the preparation of desalination layer on the polymer porous support base layer, comprising: The non-woven fabric support substrate with polymer porous support base layer on the surface obtained in step two is treated with aqueous amine solution, oil phase solution, and then washed with pure water after heat treatment, and then soaked in moisturizing agent glycerol and dried to obtain; Specifically, the non-woven fabric support substrate with polymer porous support base layer on the surface is soaked in aqueous amine solution for 0.3-5 min, and the excess aqueous phase is squeezed out; then the oil phase solution is coated on the polymer porous support base layer for 0.3-2 min for interfacial reaction, then soaked in lye for 0.5-2 min for alkaline washing, immersed in hot water for 10-30 min for shaping, and glycerol moisturizing for 0.5-2 min to form a desalination layer; The aqueous amine solution contains m-phenylenediamine 1.5-4.5%, triethylamine hydrochloride 1-5%, sodium hydroxide 0.01-0.05%, and sodium bisulfite 0.01-0.2% by mass percentage concentration; The oil phase solution includes trimesoyl chloride 0.1-0.28%, tripropyl phosphate 0.6-1%, and organic solvent ISOPAR M as the balance by mass percentage concentration.

6. The composite anti-fouling reverse osmosis water purification membrane produced by the method according to any one of claims 1-5, characterized in that, Including: The non-woven fabric support substrate, the polymer porous support base layer, the desalination layer, and the scale inhibition layer, wherein the polymer porous support base layer is formed on the surface of the non-woven fabric support substrate, the desalination layer is formed on the surface of the polymer porous support base layer, and the scale inhibition layer is formed on the surface of the desalination layer.

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