Method for preparing high-flux reverse osmosis membrane by washing with n-butyl alcohol

Abstract

The invention relates to a method for preparing a high-flux reverse osmosis membrane by washing with n-butyl alcohol, in particular to a method for preparing the high-flux reverse osmosis membrane by washing with n-butyl alcohol to remove an Isopar G solvent subjected to interfacial polymerization. According to the specific steps of bottom membrane pretreatment, water phase and oil phase solution preparation, interfacial polymerization reaction, n-butyl alcohol cleaning, post-treatment and the like and the parameter ranges in the steps, an Isopar G solvent left after the n-butyl alcohol is subjected to interfacial polymerization on the reverse osmosis membrane is innovatively selected; according to the method, the normal butanol is used as a raw material, parameters such as concentration, temperature and time in the normal butanol cleaning process are accurately controlled, and meanwhile, the steps of early-stage bottom membrane pretreatment, water phase and oil phase solution preparation and post-treatment also have a synergistic effect with normal butanol cleaning, so that the high performance of the reverse osmosis membrane is jointly ensured, and the method is suitable for industrial production and has very high practicability.

Description

Technical Field

[0001] This invention belongs to the technical field of membrane materials, and particularly relates to a method for preparing high-flux reverse osmosis membranes using n-butanol cleaning. Background Technology

[0002] Reverse osmosis membranes, as a key component of membrane separation technology, are widely used in many fields such as seawater desalination, industrial wastewater treatment, and pure water production. In the preparation process of reverse osmosis membranes, interfacial polymerization is one of the most commonly used methods. Interfacial polymerization involves the polymerization reaction of amine monomers in the aqueous phase and acyl chloride monomers in the oil phase on the bottom membrane surface, thereby forming an ultrathin active layer with separation function.

[0003] In existing interfacial polymerization processes for preparing reverse osmosis membranes, organic solvents such as Isopar G are typically used to dissolve the acyl chloride monomers in the oil phase. This is because Isopar G has good solubility and volatility, providing a suitable reaction environment for the interfacial polymerization reaction. However, after the interfacial polymerization reaction is complete, the Isopar G solvent remaining on and inside the membrane surface causes a series of problems.

[0004] First, incompletely removed Isopar G occupies part of the membrane pore space, reducing the effective pore size of the membrane. This directly affects the flux of water molecules through the membrane, reducing the permeate output of the reverse osmosis membrane and failing to meet the high-efficiency filtration requirements of practical applications. For example, in some large-scale seawater desalination projects, reduced flux means that more membrane modules are needed to achieve the same permeate output, which undoubtedly increases equipment costs and floor space requirements.

[0005] Secondly, as an organic compound, Isopar G residues may negatively impact the chemical stability of the membrane. During long-term operation, changes in environmental factors such as temperature and pH can cause residual Isopar G to react chemically with the membrane material, leading to gradual degradation of membrane performance and a shortened lifespan. Particularly in extreme industrial wastewater treatment scenarios, the complex composition of the wastewater interacts with residual Isopar G, accelerating membrane aging and damage.

[0006] Furthermore, traditional cleaning methods are not ideal for completely removing Isopar G. Conventional water washing is ineffective because water and Isopar G are poorly miscible, making it difficult to remove them effectively from the membrane surface and interior. While cleaning with strong organic solvents can remove Isopar G to some extent, these solvents may damage the membrane structure, affecting its separation performance. In addition, these organic solvents themselves may be toxic and volatile, posing potential threats to operator health and the environment.

[0007] In summary, how to effectively remove the residual Isopar G solvent after interfacial polymerization during the reverse osmosis membrane preparation process, while ensuring the high flux and stability of the reverse osmosis membrane, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The technical problem to be solved by this invention is to effectively remove the residual Isopar G solvent after interfacial polymerization without damaging the structure and separation performance of the reverse osmosis membrane, thereby improving the flux of the reverse osmosis membrane. In order to improve its shortcomings, this invention provides a method for preparing a high-flux reverse osmosis membrane by cleaning with n-butanol, that is, after the interfacial polymerization is completed, the membrane is cleaned with n-butanol to obtain a high-flux reverse osmosis membrane.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: A method for preparing a high-flux reverse osmosis membrane using n-butanol cleaning includes the following steps: S1: Pretreatment of the substrate; Select a suitable substrate material, cut the substrate to a suitable size, immerse it in a solution containing a pretreatment agent for 1 hour, after immersion, remove the substrate and rinse it with deionized water until neutral, and then dry it in an oven for 2 hours; S2: Preparation of aqueous and oil phase solutions; Aqueous phase solution preparation: Dissolve a certain amount of m-phenylenediamine in deionized water, add an appropriate amount of additives, stir evenly, and prepare an aqueous phase solution with a concentration of 0.5-4%; Oil phase solution preparation: Dissolve trimesoyl chloride in Isopar G organic solvent to prepare an oil phase solution with a concentration of 0.1-0.2%. S3: Interfacial polymerization reaction; The pretreated substrate is completely immersed in the aqueous solution for 1 minute to allow the substrate to fully adsorb the m-phenylenediamine in the aqueous phase. Then, the substrate is removed, excess aqueous solution is drained from the surface, and it is quickly placed in the oil phase solution. On the surface of the substrate, m-phenylenediamine and trimesoyl chloride undergo interfacial polymerization. The reaction time is controlled at 3-5 minutes. During this process, the temperature of the reaction environment should be maintained at 5℃ and the humidity at 30%. S4: n-Butanol cleaning; After the interfacial polymerization reaction is completed, the substrate with the polymerized film is removed from the oil phase solution and immediately placed into the pre-prepared n-butanol cleaning solution. The concentration of n-butanol is controlled at 5% - 30%, the cleaning temperature is maintained at 5℃ - 30℃, and the cleaning time is 5 minutes - 30 minutes. During the cleaning process, the film is stirred at a speed of 5r / min using a stirring device to ensure that the n-butanol is in full contact with the surface and interior of the film, ensuring that the residual Isopar G solvent is effectively dissolved and removed. S5: Post-treatment; After cleaning, remove the membrane from the n-butanol cleaning solution, rinse it several times with deionized water to remove residual n-butanol from the membrane surface, and then immerse the membrane in a solution containing post-treatment agent for 1 hour. After immersion, remove the membrane and let it air dry at room temperature to finally obtain a high-flux reverse osmosis membrane.

[0010] As a preferred embodiment, the pretreatment agent in step S1 is a low-concentration alcohol solution, such as ethanol, isopropanol, or a dilute acid solution, such as a 0.1%-0.5% hydrochloric acid solution.

[0011] As a preferred embodiment, the post-treatment agent in step S5 is a hydrophilic polymer solution, such as polyvinyl alcohol, polyethylene glycol, or amino acid compounds, such as glycine or alanine.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention innovatively selects n-butanol to clean the residual Isopar G solvent after the polymerization at the reverse osmosis membrane interface, and precisely controls parameters such as concentration, temperature and time during the n-butanol cleaning process. At the same time, the pretreatment of the bottom membrane, the preparation of aqueous and oil phase solutions and the post-treatment steps also work synergistically with the n-butanol cleaning to jointly ensure the high performance of the reverse osmosis membrane, making it suitable for industrial production and highly practical. Detailed Implementation

[0013] The technical solution of this application will be further described and illustrated below through embodiments.

[0014] A method for preparing a high-flux reverse osmosis membrane using n-butanol cleaning includes the following steps: S1: Pretreatment of the substrate; Select a suitable substrate material, cut the substrate to a suitable size, immerse it in a solution containing a pretreatment agent for 1 hour, after immersion, remove the substrate and rinse it with deionized water until neutral, and then dry it in an oven for 2 hours; S2: Preparation of aqueous and oil phase solutions; Aqueous phase solution preparation: Dissolve a certain amount of m-phenylenediamine in deionized water, add an appropriate amount of additives, stir evenly, and prepare an aqueous phase solution with a concentration of 0.5-4%; Oil phase solution preparation: Dissolve trimesoyl chloride in Isopar G organic solvent to prepare an oil phase solution with a concentration of 0.1-0.2%. S3: Interfacial polymerization reaction; The pretreated substrate is completely immersed in the aqueous solution for 1 minute to allow the substrate to fully adsorb the m-phenylenediamine in the aqueous phase. Then, the substrate is removed, excess aqueous solution is drained from the surface, and it is quickly placed in the oil phase solution. On the surface of the substrate, m-phenylenediamine and trimesoyl chloride undergo interfacial polymerization. The reaction time is controlled at 3-5 minutes. During this process, the temperature of the reaction environment should be maintained at 5℃ and the humidity at 30%. S4: n-Butanol cleaning; After the interfacial polymerization reaction is completed, the substrate with the polymerized film is removed from the oil phase solution and immediately placed into the pre-prepared n-butanol cleaning solution. The concentration of n-butanol is controlled at 5% - 30%, the cleaning temperature is maintained at 5℃ - 30℃, and the cleaning time is 5 minutes - 30 minutes. During the cleaning process, the film is stirred at a speed of 5r / min using a stirring device to ensure that the n-butanol is in full contact with the surface and interior of the film, ensuring that the residual Isopar G solvent is effectively dissolved and removed. S5: Post-treatment; After cleaning, remove the membrane from the n-butanol cleaning solution, rinse it several times with deionized water to remove residual n-butanol from the membrane surface, and then immerse the membrane in a solution containing post-treatment agent for 1 hour. After immersion, remove the membrane and let it air dry at room temperature to finally obtain a high-flux reverse osmosis membrane.

[0015] Six sets of examples were designed using the controlled variable method to verify the relationship between the ratio of aqueous phase solution and oil phase solution in the above steps, as well as the influence of the ratio of n-butanol cleaning solution concentration on throughput improvement. The basic conditions were uniformly set as follows: cleaning temperature 20°C and cleaning time 15 minutes. Example

[0016] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions: Prepare an aqueous phase solution with a concentration of 2% and an oil phase solution with a concentration of 0.15%, using the intermediate values ​​from the above steps. S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution is controlled at 15%, also using an intermediate value; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux improvement rate of approximately 12.5%. This set of data was used as a baseline control group to verify the average effect of this scheme compared to the method without n-butanol cleaning. Example

[0017] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions, including a 4% aqueous phase solution and a 0.15% oil phase solution; S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution is controlled at 15%; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux improvement rate of approximately 14.2%. Compared with the data in Example 1, this set of data increased the concentration of the aqueous phase solution to the upper limit while keeping the concentrations of the oil phase solution and the n-butanol cleaning solution constant. Example

[0018] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions, preparing an aqueous phase solution with a concentration of 0.5% and an oil phase solution with a concentration of 0.15%; S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution is controlled at 15%; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux improvement rate of approximately 10.8%. Compared with the data in Example 1, this set of data reduced the concentration of the aqueous phase solution to the lower limit while keeping the concentrations of the oil phase solution and the n-butanol cleaning solution constant. Example

[0019] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions, including a 2% aqueous phase solution and a 0.15% oil phase solution; S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution should be controlled at 30%; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux increase rate of approximately 15%. Compared with the data in Example 1, this set of data increased the concentration of n-butanol cleaning solution to the upper limit while keeping the concentrations of aqueous and oil phase solutions constant. Example

[0020] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions, including a 2% aqueous phase solution and a 0.15% oil phase solution; S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution is controlled at 5%; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux improvement rate of approximately 10.2%. Compared with the data in Example 1, this set of data reduced the concentration of n-butanol cleaning solution to the lower limit while keeping the concentrations of the aqueous and oil phase solutions constant. Example

[0021] S1: Pretreatment of the bottom film; S2: Preparation of aqueous and oil phase solutions, including a 2% aqueous phase solution and a 0.2% oil phase solution; S3: Interfacial polymerization reaction; S4: n-Butanol cleaning; the concentration of the n-butanol cleaning solution is controlled at 15%; S5: Post-processing; Conclusion: The reverse osmosis membrane produced through the above steps was tested and found to have a flux improvement rate of approximately 10.2%. Compared with the data in Example 1, this set of data increased the oil phase solution concentration to the upper limit while keeping the concentrations of the aqueous solution and the n-butanol cleaning solution constant.

[0022] The above six sets of examples are summarized in the table below: The following conclusions can be drawn from the above data: 1. The concentration of n-butanol solution is the core factor affecting flux improvement; when the concentration of n-butanol increases from 5% to 30%, the flux improvement rate increases from 10.2% to 15%. Higher concentrations of n-butanol have higher solubility in Isopar G solvent, which can more thoroughly remove residual solvent in the membrane pores, restore the effective pore size, and reduce the resistance to water molecule passage. 30% is the optimal concentration. Further increases may cause the membrane material to swell, which will negatively affect the separation performance. 2. The concentration of the aqueous solution also has a significant impact on flux improvement. When the aqueous solution concentration is 4% (Example 2), the flux improvement rate is 14.2%, which is 3.4 percentage points higher than that of 0.5% concentration (Example 3). Higher concentrations of m-phenylenediamine can form a more uniform active layer structure, reduce membrane pore blockage, and achieve the dual effect of "structure optimization + residue removal" when combined with n-butanol cleaning. 3. The concentration of the oil phase solution has a relatively small impact on the flux increase. For example, when the oil phase concentration increases from 0.15% to 0.2% (Example 6), the flux increase rate only increases by 1.3 percentage points, which is a limited increase. The oil phase concentration mainly affects the polymerization reaction rate. Within the range of 0.1%-0.2%, the reaction degree can meet the basic requirements of the active layer, and further increases have limited benefits for flux.

[0023] Based on the above six examples, the optimal solution concentration combination should be 3-4% aqueous solution, 0.15%-0.2% oil solution, and 25%-30% n-butanol cleaning solution, with cleaning conditions of 20℃-25℃ and 15-20 minutes. Using the above combination can achieve a flux increase of 14.5%-15.0% while ensuring membrane stability and service life.

[0024] In addition, the present invention also has the following effects: Significantly Improved Flux: The use of n-butanol for cleaning effectively removes residual Isopar G solvent after interfacial polymerization, restoring the effective pore size of the membrane and reducing the resistance of water molecules passing through the membrane, thereby significantly improving the flux of the reverse osmosis membrane. Actual testing shows that compared to traditional preparation methods without n-butanol cleaning, the reverse osmosis membrane prepared by this invention has a 10%-15% higher flux, capable of treating more water in the same amount of time, greatly improving water treatment efficiency. For example, in an industrial wastewater treatment project, the reverse osmosis membrane prepared by this invention significantly increased the water production, meeting the company's growing demand for production water.

[0025] Enhanced stability: Due to the excellent compatibility of n-butanol with membrane materials, it does not damage the membrane's structure and chemical properties during cleaning. Instead, it removes residual Isopar G that could potentially affect membrane stability. This allows the reverse osmosis membrane to better resist environmental factors such as temperature and pH changes during long-term operation, reducing the risk of membrane performance degradation and extending membrane lifespan. According to feedback from practical applications, the reverse osmosis membrane prepared by this invention has a 20%-30% longer lifespan compared to membranes prepared using traditional methods, reducing equipment maintenance and replacement costs.

[0026] Cost reduction: n-Butanol, as a common organic solvent, is relatively inexpensive and widely available. Compared with some traditional cleaning organic solvents, using n-butanol for cleaning not only provides better cleaning results but also lowers costs. Furthermore, because the reverse osmosis membrane prepared by this invention has increased flux and extended service life, the number of membrane modules required during the operation of the entire water treatment system is reduced, and the frequency of equipment maintenance decreases, further reducing overall costs and improving economic efficiency.

[0027] Environmentally friendly: n-Butanol has relatively low toxicity and low volatility, posing minimal health risks to operators during cleaning. Furthermore, n-Butanol degrades readily in the natural environment, unlike some traditional organic solvents that cause long-term environmental pollution. This makes the preparation method of this invention more environmentally friendly and conducive to sustainable development.

[0028] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A method for cleaning high flux reverse osmosis membranes using n-butanol, characterized in that, Comprising the following steps: S1: Pretreatment of the base film; select the appropriate base film material, cut the base film into the appropriate size, soak in a solution containing a pretreatment agent for 1H, after soaking is complete, remove the base film and rinse with deionized water until neutral, then dry in an oven for 2H; S2: Preparation of water phase and oil phase solutions; water phase solution preparation, dissolve a certain amount of m-phenylenediamine in deionized water, add an appropriate amount of additive, stir uniformly, prepare a water phase solution with a concentration of 0.5-4%; oil phase solution preparation, dissolve trimesoyl chloride in Isopar G organic solvent, prepare an oil phase solution with a concentration of 0.1-0.2%; S3: Interfacial polymerization; immerse the pretreated base film in the water phase solution for 1 minute to allow the base film to fully absorb the m-phenylenediamine in the water phase, then remove the base film and drain the excess water phase solution, quickly place it in the oil phase solution, where the m-phenylenediamine and trimesoyl chloride on the surface of the base film undergo interfacial polymerization, the reaction time is controlled at 3-5 minutes, and the temperature and humidity of the reaction environment are maintained at 5°C and 30%, respectively; S4: n-butanol cleaning; after the interfacial polymerization reaction is complete, remove the base film with the polymerized membrane from the oil phase solution and immediately place it in the pre-prepared n-butanol cleaning solution, control the n-butanol concentration to 5%-30%, maintain the cleaning temperature at 5°C-30°C, and the cleaning time for 5-30 minutes, during the cleaning process, stir the n-butanol and the membrane surface and interior with a stirring device at a speed of 5 r / min to ensure that the residual Isopar G solvent is effectively dissolved and removed; S5: Post-treatment; after cleaning is complete, remove the membrane from the n-butanol cleaning solution, rinse with deionized water several times to remove the residual n-butanol on the membrane surface, then immerse the membrane in a solution containing a post-treatment agent for 1 hour, after soaking is complete, remove the membrane and air dry at room temperature, and finally obtain a high-flux reverse osmosis membrane.

2. The method for cleaning the high flux reverse osmosis membrane by using n-butanol according to claim 1, characterized in that: The pretreatment agent in step S1 is a low-concentration alcohol solution, such as ethanol, isopropanol, or a dilute acid solution, such as a 0.1%-0.5% hydrochloric acid solution.

3. The method for cleaning the high flux reverse osmosis membrane by using n-butanol according to claim 1, characterized in that: The post-treatment agent in step S5 is a hydrophilic polymer solution, such as polyvinyl alcohol, polyethylene glycol, or an amino acid compound, such as glycine, alanine.