Repair additive suitable for oxidized reverse osmosis membrane and preparation method thereof

Abstract

The invention belongs to the technical field of reverse osmosis, and particularly relates to a repair additive suitable for an oxidized reverse osmosis membrane and a preparation method of the repair additive. The repairing additive comprises the following components in percentage by mass: 5%-10% of a novel biological degradable material, 80%-89.95% of a lipid organic compound, 5%-10% of an organic solvent and 0.05%-0.1% of a thickening agent, according to the method, the desalination rate of the oxidized reverse osmosis membrane can be recovered to 97% or above, the recovery rate of a single membrane can be recovered to about 15%, and the repair effect can be stably maintained for half a year or above; and meanwhile, the reverse osmosis water production can be maintained not to be reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of reverse osmosis, and particularly relates to a repair additive for oxidized reverse osmosis membranes and a preparation method thereof. Background Art

[0002] Water is the source of life on Earth. However, with the growth of the population, the acceleration of industrialization, and global climate change, the problem of water shortage has become increasingly severe. Against this background, water treatment technology has become an important means to address the global water crisis. Among them, reverse osmosis membrane technology has become a star technology in the water treatment field due to its high filtration efficiency and wide application scenarios. Reverse osmosis membrane technology can remove more than 99% of impurities in water, including dissolved salts, heavy metals, microorganisms, organic pollutants, etc. Therefore, the water quality treated by reverse osmosis is extremely pure and meets the high-standard water quality requirements for various uses.

[0003] The reverse osmosis membrane is a key part of the reverse osmosis system. With the increase in the membrane treatment volume and the extension of the use time, the desalination rate of the reverse osmosis membrane will decrease. In addition, regular acid-base chemical cleaning will also cause the gradual attenuation of the membrane performance. Usually in the pure water field, especially in the ultra-pure water field, the desalination rate of the membrane is required to be above 95% for a single set of systems. Under normal circumstances, after about 2 years, the desalination rate of the membrane will drop below 95%, and even drop below 90%. In some reclaimed water reuse fields, due to the use of the oxidizing biocide sodium hypochlorite, it is extremely easy to cause the membrane to be oxidized due to the residual oxidizing biocide entering the reverse osmosis system, resulting in a significant decrease in the desalination rate of the reverse osmosis membrane. In view of the above situation, there are some agents in the prior art to improve the desalination rate of the membrane, which can achieve a certain degree of recovery of the membrane desalination rate.

[0004] Currently, some power plants choose to use a composite repair agent carefully formulated with high-purity diaminobenzoic acid or triaminobenzoic acid as the core active ingredient, supplemented by the natural biopolymer chitosan (a natural polysaccharide with good biocompatibility and film-forming properties), and a specific proportion of aminopentane (an organic amine compound commonly used to adjust the pH value of the solution and enhance permeability).

[0005] However, for the above-mentioned raw materials, especially diaminobenzoic acid, triaminobenzoic acid, and chitosan, due to the complex production process and high purification difficulty, their market prices are relatively high, which undoubtedly increases the operating costs of the power station. Secondly, although these repair agents have shown certain effects in improving the desalination rate, during the actual application process, technicians found that they tend to affect the water production capacity of the reverse osmosis system to a certain extent. Specifically, in the initial stage of repair or under specific conditions, with the effective removal of pollutants on the membrane surface and partial recovery of the membrane pore structure, although the desalination rate increases, at the same time, due to the change of the hydrodynamic characteristics on the membrane surface or the increase of partial resistance in the membrane, the water molecule flux passing through the membrane decreases, that is, the water production capacity shows a downward trend. Summary of the Invention

[0006] The purpose of the present invention is to provide a repair additive suitable for oxidized reverse osmosis membranes and a preparation method thereof, so as to solve the technical problem that the reduction of the desalination rate of reverse osmosis membranes in the prior art affects the safe production of units.

[0007] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a repair additive suitable for oxidized reverse osmosis membranes, which, by mass percentage, includes 5% - 10% of a new biological degradable material, 80% - 89.95% of a lipid organic compound, 5% - 10% of an organic solvent, and 0.05% - 0.1% of a thickener.

[0008] Preferably, the new biological degradable material is one or more of polylactic acid and acrylic acid - hydroxypropyl acrylate copolymer.

[0009] Preferably, the lipid organic compound is one or more of ethyl acetate and n - butyl acetate.

[0010] Preferably, the organic solvent is isopropanol.

[0011] Preferably, the thickener is polyethylene oxide.

[0012] In the second aspect, the present invention provides a preparation method of a repair additive suitable for oxidized reverse osmosis membranes, including the following steps: S1: Mix the new biological degradable material and the lipid organic compound, stir and heat to a set temperature until completely dissolved to obtain solution A; S2: Add the organic solvent and the thickener to solution A, stir until completely dissolved to obtain the repair additive.

[0013] Preferably, the rotation speed of the stirring in S1 is 50 - 70 rpm.

[0014] Preferably, the set temperature in S1 is 60 - 80 °C.

[0015] In a third aspect, the present invention provides an application of a repair additive suitable for an oxidized reverse osmosis membrane in the field of reverse osmosis technology.

[0016] Preferably, the repair additive is used to repair the reverse osmosis membrane.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention improves the repair effect of the reverse osmosis membrane through biodegradable materials, repairs the micro-damage on the membrane surface, thereby prolonging the service life of the membrane; penetrates lipid organic compounds into the micro-cracks and damaged areas of the membrane to improve the structure of the membrane material and delay oxidation damage; changes the surface tension of the membrane through organic solvents to help the repair additive form a uniform coating on the membrane surface; improves the coating performance of the repair additive through thickeners to prevent the loss of the repair agent during use and ensure the durability and stability of the repair effect. The repair additive prepared by the present invention can restore the desalination rate of the oxidized reverse osmosis membrane to more than 97%, and the single-membrane recovery rate can be restored to about 15%. The repair effect can be stably maintained for more than half a year; at the same time, the present invention can maintain the reverse osmosis water production without reduction. Detailed Embodiments

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art with respect to the present invention. In case of conflict, the definition in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not in any way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0020] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the range (including integers and fractions).

[0021] In this article, unless otherwise specified, terms such as "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0022] In this text, for the sake of brevity in description, not all possible combinations of all technical features in each implementation or embodiment are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation or embodiment can be combined arbitrarily, and all possible combinations should be considered to be within the scope described in this specification.

[0023] The first object of the present invention is to provide a repair additive suitable for oxidized reverse osmosis membranes, which, by mass percentage, includes 5% - 10% of a new biological degradable material, 80% - 89.95% of a lipid organic compound, 5% - 10% of an organic solvent, and 0.05% - 0.1% of a thickener.

[0024] The new biological degradable material has good thermal stability, good anti-solvent property, and can be processed in various ways, such as extrusion, spinning, biaxial stretching, injection blow molding. At the same time, it has good biodegradability and can be completely degraded by microorganisms in nature after use, finally generating carbon dioxide and water without polluting the environment, which is very beneficial to environmental protection and is a recognized environmentally friendly material. The biodegradable material helps to improve the repair effect of the reverse osmosis membrane by repairing the micro-damage on the membrane surface, thereby extending the service life of the membrane. In addition, the use of the degradable material may also enhance the affinity between the repaired membrane and the water flow and improve the water permeability.

[0025] The lipid organic compound is a fast-drying solvent with excellent dissolving ability, an excellent industrial solvent, and can also be used as an eluent for column chromatography. It can be used for nitrocellulose, ethyl cellulose, chlorinated rubber and vinyl resins, cellulose acetate esters, cellulose acetate butyrate, and synthetic rubbers, and can also be used for liquid nitrocellulose ink for copiers; or it can be used as a solvent for adhesives and a thinner for paints. The lipid organic compound can penetrate into the micro-cracks and damaged areas of the membrane, improve the structure of the membrane material, and restore some of its original functions, thereby effectively delaying the further development of oxidative damage.

[0026] The organic solvent is a colorless and transparent liquid, can be freely mixed with water, has a stronger dissolving power for lipophilic substances than ethanol, and can be used as a solvent for nitrocellulose, rubber, paints, shellac, alkaloids, etc. The organic solvent helps the repair additive to form a uniform coating on the membrane surface by changing the surface tension of the membrane. In addition, the solvent can also help dissolve and release the oxidation substances or other impurities in the membrane, promoting the repair and cleaning of the membrane.

[0027] The thickener has complete water solubility, excellent solution rheology, binding effect with organic solvents, low ash content, and thermoplasticity, etc. The thickener can improve the coating performance of the repair additive, help form a uniform and lasting membrane repair layer, prevent the loss of the repair agent during use, and ensure the durability and stability of the repair effect.

[0028] The novel biodegradable material is one or more of polylactic acid (PLA) and acrylic acid - hydroxypropyl acrylate (PAA - HPA) copolymer. PLA molecules have high adhesiveness, can penetrate and fill the microcracks and damaged areas on the membrane surface, help repair the membrane material and restore its water permeability. By repairing the damage on the membrane surface, PLA helps delay the oxidation and aging process of the membrane, thus extending the service life of the membrane. The PAA - HPA copolymer can penetrate into the microcracks or damaged parts on the membrane surface and fill and repair these areas through its adhesiveness, enhancing the integrity of the membrane and preventing pollutants from further entering these areas. When both are used simultaneously, PLA provides the functions of biodegradability and enhancing the membrane structure, while the PAA - HPA copolymer improves the hydrophilicity and repair performance of the membrane, not only enhancing the repair effect but also improving the durability and anti - pollution ability of the membrane.

[0029] The lipid organic compound is one or more of ethyl acetate and n - butyl acetate. Ethyl acetate and n - butyl acetate are good solvents, which can dissolve lipids and some polar organic substances. During the repair process of the reverse osmosis membrane, they can effectively remove the organic dirt, grease and other pollutants accumulated on the membrane surface, clean the membrane surface and restore the water permeability of the membrane. Secondly, during the repair process, both of them can improve the permeability of the membrane by dissolving the pollutants attached to the membrane surface. By removing the pollution, the flux and selectivity of the membrane can be restored to near the initial state, thus improving the efficiency of the reverse osmosis system.

[0030] The organic solvent is isopropanol. Isopropanol has good dissolution characteristics and can effectively dissolve and remove organic pollutants, grease, sediments, etc. on the membrane surface, helping to clean the reverse osmosis membrane surface, reducing the accumulation of dirt on the membrane, and thus restoring the water permeability and separation effect of the membrane. In addition, isopropanol can promote the penetration of the repair additive components, making them better contact and act on the membrane surface. At the same time, isopropanol is relatively safe, with low toxicity, and is suitable for use in the membrane repair process. It does not pose too much risk to the environment and operators during handling, is an environmentally friendly solvent, and its biodegradability also ensures that the residues after use will not cause long - term pollution to the environment.

[0031] The thickener is polyethylene oxide. Polyethylene oxide has strong thickening ability and can significantly increase the viscosity of the repair additive. The increased viscosity enables the additive to be evenly coated on the reverse osmosis membrane surface, helping it to better adhere and be evenly distributed during the repair process, ensuring the complete repair of the membrane surface. Polyethylene oxide has good lubricating properties, which can make the surface of the repaired membrane smoother, reducing the resistance when water flows through the membrane. This helps to reduce the friction coefficient on the membrane surface, reduce the wear on the membrane surface, and improve the flux and use efficiency of the membrane.

[0032] The second object of the present invention is to provide a preparation method of a repair additive suitable for an oxidized reverse osmosis membrane, comprising the following steps: S1: Mix a biological new degradable material and a lipid organic compound, stir at 50-70 rpm and heat to a set temperature (60-80 °C) until completely dissolved to obtain solution A; S2: Add an organic solvent and a thickener to solution A, stir until completely dissolved to obtain the repair additive.

[0033] Through the synergistic effect of the biological new degradable material and the lipid organic compound, the present invention forms an efficient repair solution A under specific temperature and stirring conditions, and further optimizes the performance of the additive by combining an organic solvent and a thickener. The prepared repair additive not only realizes the efficient repair of the oxidized membrane layer and the recovery of the desalination rate, but also significantly improves the stability and compatibility of the repair agent, extends the service life of the reverse osmosis membrane. At the same time, the selection of green and environmentally friendly raw materials reduces the environmental risk, providing an economical, efficient and sustainable membrane repair solution for power stations. In addition, the method of the present invention is simple to operate and the process is not complicated, and it has high applicability for large-scale use scenarios.

[0034] The third object of the present invention is to provide an application of a repair additive suitable for an oxidized reverse osmosis membrane in the field of reverse osmosis technology.

[0035] Specifically, the repair additive is used to repair the reverse osmosis membrane. When in use, it can be used in combination with a reverse osmosis scale inhibitor according to specific production conditions. Exemplarily, if there is scaling or fouling, first perform chemical cleaning or physical flushing to ensure the cleanliness of the membrane surface and avoid interfering with the repair effect. Adopt intermittent dosing (1-2 times a day, each time lasting 1-2 hours), and inject it into the inlet pipeline of the reverse osmosis system through a dosing pump. It is preferred to select the position downstream of the scale inhibitor dosing point to ensure that the repair agent is evenly dispersed in the inlet water. Among them, the initial dosing concentration starts from a low dose (1-3 ppm) and is gradually increased to 10 ppm according to the recovery of the desalination rate. If the desalination rate recovers slowly, the single dosing time can be extended or the frequency can be increased (such as 3 times a day).

[0036] In addition, when performing the repair, it is necessary to first confirm the chemical compatibility of the repair additive with the existing reverse osmosis scale inhibitor (such as the pH range, whether the components conflict and react), and verify the stability after mixing through small-scale experiments to avoid problems such as precipitation, increased scaling, membrane fouling or agent failure caused by chemical incompatibility.

[0037] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0038] In the following embodiments, conventional instrument and equipment in the art are used. For the experimental methods without specific conditions indicated in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. In the following embodiments, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0039] Example 1 S1: Mix 5% of polylactic acid and 85% of ethyl acetate, stir at 50 rpm and heat to 60 °C until completely dissolved to obtain Solution A; S2: Add 9.05% of isopropanol and 0.05% of polyethylene oxide to Solution A, stir until completely dissolved to obtain the repair additive.

[0040] Example 2 S1: Mix 10% of polylactic acid and 80% of n-butyl acetate, stir at 60 rpm and heat to 65 °C until completely dissolved to obtain Solution A; S2: Add 9.05% of isopropanol and 0.05% of polyethylene oxide to Solution A, stir until completely dissolved to obtain the repair additive.

[0041] Example 3 S1: Mix 5% of acrylic acid-acrylic acid hydroxypropyl ester copolymer and 89.95% of ethyl acetate, stir at 70 rpm and heat to 70 °C until completely dissolved to obtain Solution A; S2: Add 5% of isopropanol and 0.05% of polyethylene oxide to Solution A, stir until completely dissolved to obtain the repair additive.

[0042] Example 4 S1: Mix 6% of acrylic acid-acrylic acid hydroxypropyl ester copolymer and 83.92% of n-butyl acetate, stir at 70 rpm and heat to 75 °C until completely dissolved to obtain Solution A; S2: Add 10% of isopropanol and 0.08% of polyethylene oxide to Solution A, stir until completely dissolved to obtain the repair additive.

[0043] Example 5 S1: Mix the mixture of 5% polylactic acid and acrylic acid - hydroxypropyl acrylate copolymer with the mixture of 88% ethyl acetate and n - butyl acetate, stir at 70 rpm and heat to 80 °C until completely dissolved to obtain solution A; S2: Add 6.9% isopropanol and 0.1% polyethylene oxide into solution A, stir until completely dissolved to obtain the repair additive.

[0044] To verify the repair effect of the repair additive on the oxidized reverse osmosis membrane, the repair additive prepared in Example 1 was used to repair the oxidized reverse osmosis membrane. The specific experimental conditions and data are as follows: Experimental group 1: Repair of slightly oxidized membrane (3 ppm repair agent) 1. Initial state of the membrane: (1) Desalination rate: 88% → Recovery rate: 8% → Water production: 8.5 m 3 / h; (2) Oxidation characteristics: Slight embrittlement on the membrane surface, history of chlorine exposure (0.2 ppm for 30 days).

[0045] 2. Repair plan: (1) Repair agent concentration: 3 ppm, added 2 times a day (1 hour each time), added at different times from the scale inhibitor; (2) Repair cycle: 5 days.

[0046] 3. Data after repair: (1) Desalination rate: 97.2%; (2) Recovery rate of a single membrane: 15.5%; (3) Water production: 8.5 m 3 / h (no decrease); (4) Stability: The desalination rate fluctuates ≤ 0.5% within 6 months, and the recovery rate is maintained at 15% ± 0.3%.

[0047] Experimental group 2: Repair of moderately oxidized membrane (6 ppm repair agent) 1. Initial state of the membrane: (1) Desalination rate: 82% → Recovery rate: 6.5% → Water production: 7.8 m 3 / h; (2) Oxidation characteristics: Local discoloration on the membrane surface, peak chlorine concentration of 0.5 ppm (short - term shock).

[0048] 2. Repair plan: (1) Repair agent concentration: 6 ppm, added 3 times a day (2 hours each time), added synchronously with the scale inhibitor (compatibility has been verified); (2) Repair cycle: 7 days.

[0049] 3. Data after repair: (1) Salt rejection rate: 97.8%; (2) Recovery rate of a single membrane: 15.2%; (3) Water production: 7.8 m 3 / h (no decrease); (4) Stability: The salt rejection rate drops to 97.1% and the recovery rate drops to 14.7% within 6 months.

[0050] Experimental group 3: Repair of severely oxidized membrane (10 ppm repair agent) 1. Initial state of the membrane: (1) Salt rejection rate: 75% → Recovery rate: 5% → Water production: 6.2 m 3 / h; (2) Oxidation characteristics: The surface of the membrane is significantly embrittled and fractured, and the residual chlorine exceeds the standard for a long time (0.3 ppm for 60 days).

[0051] 2. Repair plan: (1) Concentration of the repair agent: 10 ppm, added 4 times a day (2 hours each time), added independently of the scale inhibitor; (2) Repair period: 10 days.

[0052] 3. Data after repair: (1) Salt rejection rate: 97.5%; (2) Recovery rate of a single membrane: 14.8%; (3) Water production: 6.2 m 3 / h (no decrease); (4) Stability: The salt rejection rate drops to 95.3% and the recovery rate drops to 13.5% within 6 months.

[0053] In summary, the present invention can restore the salt rejection rate of the oxidized reverse osmosis membrane to over 97%, and the recovery rate of a single membrane can be restored to about 15%. The repair effect can be stably maintained for more than half a year. At the same time, the present invention can maintain the reverse osmosis water production without decrease.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A repair additive applicable to oxidized reverse osmosis membranes, characterized in that, By mass percentage, it includes 5% - 10% of a new biological degradable material, 80% - 89.95% of a lipid organic compound, 5% - 10% of an organic solvent, and 0.05% - 0.1% of a thickener.

2. The repair additive for an oxidized reverse osmosis membrane according to claim 1, wherein The new biological degradable material is one or more of polylactic acid and a copolymer of acrylic acid and hydroxypropyl acrylate.

3. The repair additive suitable for an oxidized reverse osmosis membrane according to claim 1, wherein, The lipid organic compound is one or more of ethyl acetate and n-butyl acetate.

4. A repair additive applicable to an oxidized reverse osmosis membrane according to claim 1, characterized in that, The organic solvent is isopropanol.

5. A repair additive applicable to an oxidized reverse osmosis membrane according to claim 1, characterized in that, The thickener is polyethylene oxide.

6. The preparation method of a repair additive applicable to an oxidized reverse osmosis membrane according to any one of claims 1 to 5, characterized in that, It includes the following steps: S1: Mix the new biological degradable material and the lipid organic compound, stir and heat to a set temperature until completely dissolved to obtain solution A; S2: Add the organic solvent and the thickener to solution A, stir until completely dissolved to obtain the repair additive.

7. The preparation method of a repair additive applicable to an oxidized reverse osmosis membrane according to claim 6, characterized in that, The rotation speed of the stirring in S1 is 50 - 70 rpm.

8. The preparation method of a repair additive applicable to an oxidized reverse osmosis membrane according to claim 6, characterized in that, The set temperature in S1 is 60 - 80 °C.

9. Application of a repair additive for an oxidized reverse osmosis membrane according to claim 1 in the field of reverse osmosis technology.

10. The application according to claim 9, wherein The repair additive is used to repair the reverse osmosis membrane.