Cleaning agent for silicon scale formed on reverse osmosis membrane and nanofiltration membrane

Abstract

The invention provides a cleaning agent for silicon scale formation of a reverse osmosis membrane and a nanofiltration membrane, and belongs to the technical field of scale removers, the cleaning agent comprises the following components by volume fraction: 1-5 parts of polyacrylate, 1-5 parts of a phosphono carboxylic acid copolymer, 10-15 parts of a ceramic dispersant, 15-20 parts of sodium polyacrylate, 2-4 parts of sodium hydroxide, and 1-5 parts of sodium dodecyl benzene sulfonate. The method is high in pertinence and high in efficiency, silicon scale which cannot be removed by a traditional acid-base cleaning agent can be cleaned, the cleaning time is greatly shortened, and therefore the energy consumption of the system is reduced; the flux and operation efficiency of the reverse osmosis membrane can be quickly and efficiently recovered, and the service life of the reverse osmosis membrane is prolonged; the cleaning method and process using the cleaning agent are simple in operation, low in maintenance cost and easy to realize automatic operation.

Description

Technical Field

[0001] This invention relates to the field of descaling agents, specifically to a cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes. Background Technology

[0002] Reverse osmosis / nanofiltration membrane technology, as a novel separation technology, is one of the most widely used technologies in wastewater treatment. However, in the process of wastewater reuse, the high content of calcium and magnesium ions, which contribute to hardness, poses a significant hazard and has received considerable attention. The treatment of dissolved silica compounds, however, has not received sufficient attention. Once silica compounds form dense scale on the surface of the reverse osmosis membrane, they are difficult to clean using ordinary methods, seriously affecting the long-term safe operation of the reverse osmosis membrane.

[0003] To date, methods for preventing the formation of particularly difficult-to-clean silica scale on reverse osmosis membranes in projects using reverse osmosis membrane technology to treat high-silica or silica-containing wastewater include lime removal, pH adjustment for silica removal, flocculation sedimentation, and the use of silica inhibitors and scale inhibitors. However, these methods involve real-time monitoring of incoming water quality, real-time adjustment of process control, real-time monitoring of the reverse osmosis membrane system's operating status, and the scale inhibition effect of silica inhibitors and scale inhibitors. Oversights are inevitable. Once the control of dissolved silica compounds fluctuates, silica scale will inevitably form on the reverse osmosis membrane, leading to a deterioration in operating parameters such as permeate flow, desalination rate, and pressure differential of the reverse osmosis system. In such cases, conventional acid-base chemical cleaning methods can only remove carbonate scale on the surface of the reverse osmosis membrane and cannot effectively clean the stubborn silica scale that has already formed. Summary of the Invention

[0004] The purpose of this invention is to provide a cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes, so as to solve at least one of the technical problems existing in the background art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes. The cleaning agent comprises the following components by volume fraction: 1-5 parts polyacrylate, 1-5 parts phosphonocarboxylic acid copolymer, 10-15 parts ceramic dispersant, 15-20 parts sodium polyacrylate, 2-4 parts sodium hydroxide, and 1-5 parts sodium dodecylbenzenesulfonate.

[0007] Preferably, the cleaning agent comprises the following volume fractions: 1 part polyacrylate, 1 part phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 15 parts sodium polyacrylate, 2 parts sodium hydroxide, and 1 part sodium dodecylbenzenesulfonate.

[0008] Preferably, the cleaning agent comprises the following volume fractions: 5 parts polyacrylate, 5 parts phosphonocarboxylic acid copolymer, 15 parts ceramic dispersant, 20 parts sodium polyacrylate, 4 parts sodium hydroxide, and 5 parts sodium dodecylbenzenesulfonate.

[0009] Preferably, the cleaning agent comprises the following volume fractions: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate.

[0010] Preferably, the cleaning agent is prepared by mixing the following components according to volume fractions: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate.

[0011] Optionally, the silica scale is any one or a combination of at least two of silicate scale or colloidal silica.

[0012] The beneficial effects of this invention are: it is highly targeted and efficient, capable of cleaning silica scale that traditional acid and alkali cleaning agents cannot remove, greatly shortening the cleaning time and thus reducing the system's energy consumption; it can quickly and efficiently restore the flux and operating efficiency of the reverse osmosis membrane, extending the service life of the reverse osmosis membrane; the cleaning method and process using the cleaning agent of this invention are simple to operate, have low maintenance costs, and are easy to automate.

[0013] The advantages of additional aspects of the invention will be set forth more clearly in the following description or will be learned by practice of the invention. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0015] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0016] It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as here.

[0017] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, and / or groups thereof.

[0018] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of those different embodiments or examples.

[0019] To facilitate understanding of the present invention, the present invention will be further explained and described below with reference to specific embodiments, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0021] The purpose of this invention is to overcome the aforementioned shortcomings of the prior art by providing a composite cleaning agent for reverse osmosis membrane silica scaling and its preparation method. This invention primarily addresses the problem of silica scaling on reverse osmosis membranes due to the inability to stably control the operating process in existing reverse osmosis silica scaling technologies. It proposes using specific chemical agents to alter the composition or properties of contaminants, thereby achieving chemical cleaning of reverse osmosis membrane systems with special silica scaling, and restoring the membrane elements to their original performance requirements.

[0022] Example 1

[0023] In this embodiment 1, a composite cleaning agent for silica scale buildup on reverse osmosis / nanofiltration membranes is provided. Its composition includes: polyacrylate, phosphonocarboxylic acid copolymer, ceramic dispersant, sodium polyacrylate, sodium hydroxide, and sodium dodecylbenzenesulfonate. The volume fractions of the cleaning agent are: 1-5 parts polyacrylate, 1-5 parts phosphonocarboxylic acid copolymer, 10-15 parts ceramic dispersant, 15-20 parts sodium polyacrylate, 2-4 parts sodium hydroxide, and 1-5 parts sodium dodecylbenzenesulfonate. The composite cleaning agent is obtained by mixing the above components.

[0024] Example 2

[0025] In this embodiment 2, a composite cleaning agent for treating silica scale buildup on reverse osmosis / nanofiltration membranes is provided. The cleaning agent comprises the following volume fractions: 1 part polyacrylate, 1 part phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 15 parts sodium polyacrylate, 2 parts sodium hydroxide, and 1 part sodium dodecylbenzenesulfonate. The composite cleaning agent is obtained by mixing the above components.

[0026] Example 3

[0027] In this embodiment 3, a composite cleaning agent for silica scale buildup on reverse osmosis / nanofiltration membranes is provided, wherein the volume fraction of the cleaning agent is: 5 parts polyacrylate, 5 parts phosphonocarboxylic acid copolymer, 15 parts ceramic dispersant, 20 parts sodium polyacrylate, 4 parts sodium hydroxide, and 5 parts sodium dodecylbenzenesulfonate.

[0028] Example 4

[0029] In this embodiment 4, a composite cleaning agent for silica scale buildup on reverse osmosis / nanofiltration membranes is provided, wherein the volume fraction of the cleaning agent is: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate.

[0030] Example 5

[0031] In this embodiment 5, a composite cleaning agent for silica scale buildup on reverse osmosis / nanofiltration membranes is provided. The cleaning agent is prepared by mixing the following components according to volume fractions: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate. After mixing evenly, the cleaning agent can be prepared.

[0032] Example 6

[0033] In this embodiment 6, a cleaning agent is provided that can quickly and efficiently remove a dense layer of silicate scale or colloidal silica formed on the surface of membrane elements, restoring the flux and operating efficiency of the membrane elements and extending the service life of reverse osmosis / nanofiltration membranes. Its working principle is as follows: the cleaning agent contains anionic surfactants and sodium hydroxide. During the online chemical cleaning process, the cleaning agent is added. Due to the influence of the surfactant and electrostatic repulsion, the interaction forces of silica scale contaminants are significantly weakened, and the bonds between contaminants are broken. This causes the originally aggregated silica scale to gradually separate, eventually decomposing from a solid state into a dissolved state. When this cleaning agent fills the filtration device, contaminants on the surface layer of the membrane elements continuously dissolve in the cleaning agent, thereby achieving the cleaning purpose.

[0034] On the other hand, an important indicator for evaluating the cleaning of fouled membranes is the change in the membrane's ion separation performance after cleaning.

[0035] In this embodiment, based on actual cleaning, the following conclusions can be drawn: the original membrane is effective for Cl... - and SO4 2- The separation efficiency reached 45%.

[0036] The formula for calculating ion separation efficiency is as follows:

[0037]

[0038] In the formula, c is the concentration of inorganic anions, the subscripts f and p represent raw water and permeate water respectively, and R is the retention efficiency of nanofiltration membrane / reverse osmosis membrane for the corresponding inorganic anions.

[0039] The formula for calculating ion rejection rate is as follows:

[0040]

[0041] In the formula, c is the concentration of inorganic anions, and the subscripts f and p represent raw water and permeate water, respectively.

[0042] After different cleaning processes, the retention efficiencies of the fouled membranes for both inorganic anions decreased to varying degrees. Among these, cleaning with HCl solution resulted in the largest decrease in ion separation efficiency of the nanofiltration membrane, with the cleaned membrane exhibiting the highest retention efficiency for Cl... - and SO4 2- The separation efficiency was only 7. However, after cleaning with the reagent in this embodiment, the ion separation efficiency can be restored to 44.8. Based on the recovery of membrane flux, the nanofiltration membrane cleaned with this reagent is more thorough.

[0043] In summary, the present invention relates to a composite cleaning agent for reverse osmosis membrane silica scale and its preparation method, wherein the silica scale includes any one or a combination of at least two of silicate scale and colloidal silica, and the cleaning agent comprises the following components in volume fractions: 1-5 parts of polyacrylate, 1-5 parts of phosphonocarboxylic acid copolymer, 10-15 parts of ceramic dispersant, 15-20 parts of sodium polyacrylate, 5-10 parts of sodium hydroxide, and 1-5 parts of sodium dodecylbenzenesulfonate.

[0044] The functions of each component in the composite cleaning agent of this invention are described below:

[0045] Polyacrylate (1-5 parts), as an anionic polymer, chelates metal ions (such as Ca2+) in silicates through carboxylic acid groups. 2+ Mg 2+ This process disrupts the crystal structure of the silica deposits; simultaneously, it adsorbs onto the surface of colloidal silica, dispersing the particles through electrostatic repulsion. Key characteristics: Moderate molecular weight, balancing chelation and dispersion capabilities.

[0046] Phosphonoylcarboxylic acid copolymer (1-5 parts), a bifunctional polymer containing phosphonic acid and carboxylic acid groups, exhibits strong chelating ability against silicate scale (especially at high pH) while inhibiting the redeposition of colloidal silica. Advantages: Strong alkali resistance, suitable for use in combination with sodium hydroxide.

[0047] Ceramic dispersant (10-15 parts), specially designed for high-hardness, high-silica water. It stabilizes colloidal silica through steric hindrance, preventing its aggregation and deposition. It may contain siloxane components to specifically break Si-O-Si bonds. Special feature: Synergistic effect with organic polymers to improve the removal efficiency of colloidal silica.

[0048] Sodium polyacrylate (15-20 parts): High concentration provides a large amount of negative charge, enhancing the electrostatic dispersion of colloidal silica; it also acts as a carrier to enhance the permeability of other agents and help remove scale from the membrane surface. Proportioning considerations: Use the largest amount due to its low cost and linearly increasing dispersion effect with concentration.

[0049] Sodium hydroxide (5-10 parts) provides a strongly alkaline environment (pH>11), promoting the hydrolysis of silicates into soluble silicic acid (H3SiO4-), while also dissolving organic pollutants. Balance point: Excessive amounts will damage the membrane material, so it should be controlled within 10 parts.

[0050] Sodium dodecylbenzenesulfonate (1-5 parts), an anionic surfactant, reduces surface tension and enhances the penetration of the agent into the colloidal silica within the membrane pores; at the same time, it emulsifies oily contaminants and assists in the removal of silica scale.

[0051] The compound cleaning agent of this invention is designed based on the following principle regarding the proportions of each component:

[0052] (1) Clear distinction between primary and secondary components: Sodium polyacrylate (15-20 parts) and ceramic dispersant (10-15 parts) are the main components, accounting for the highest proportion, directly solving the problem of silica scale dispersion. Sodium hydroxide (5-10 parts) needs to be sufficient but not excessive to balance solubility and membrane safety.

[0053] (2) Synergistic effect: Polyacrylate + phosphonocarboxylic acid copolymer (1-5 parts each): Low-proportion compounding achieves chelation-dispersion dual pathways, avoiding precipitation caused by excessive amount of single agent (such as Ca-phosphonate). Surfactant (1-5 parts): A small amount can significantly reduce the contact angle, while too high a value will easily cause foaming and affect the cleaning operation.

[0054] (3) Targeted adaptation to the characteristics of silica scale: Colloidal silica relies on electrostatic dispersion (sodium polyacrylate / ceramic dispersant), while silicate scale relies on alkaline hydrolysis + chelation (NaOH + phosphonoyl copolymer). In an alkaline environment (pH>11), the zeta potential of colloidal silica is more negative, which enhances the effect of the dispersant. Therefore, the ratio of NaOH to dispersant needs to be matched.

[0055] (4) Safety and cost: All components are water-soluble, with no risk of solid residue. Polyacrylate is more expensive and is limited to 5 parts; sodium polyacrylate is cheaper and can be used in larger quantities.

[0056] This invention's composite cleaning agent solves the problem of poor cleaning effect of traditional acid and alkali cleaning agents on silica scale buildup in reverse osmosis and nanofiltration membrane elements. By configuring it into a silica scale cleaning solution for online cleaning, the reverse osmosis membrane can be restored to its original performance. Compared with existing technologies, this invention uses specific chemical agents to change the composition or properties of contaminants, thereby achieving chemical cleaning of reverse osmosis membrane systems with special silica scale buildup, restoring the membrane elements to their original performance requirements. This cleaning agent is simple to operate, safe to use, widely applicable, provides stable cleaning results, and can extend the service life of reverse osmosis membranes.

[0057] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in the present invention, various modifications or variations that can be made by those skilled in the art without creative effort should be included within the scope of protection of the present invention.

Claims

1. A cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes, characterized in that, The cleaning agent comprises the following components by volume fraction: 1-5 parts polyacrylate, 1-5 parts phosphonocarboxylic acid copolymer, 10-15 parts ceramic dispersant, 15-20 parts sodium polyacrylate, 2-4 parts sodium hydroxide, and 1-5 parts sodium dodecylbenzenesulfonate.

2. The cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes according to claim 1, characterized in that, The cleaning agent comprises the following components by volume fraction: 1 part polyacrylate, 1 part phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 15 parts sodium polyacrylate, 2 parts sodium hydroxide, and 1 part sodium dodecylbenzenesulfonate.

3. The cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes according to claim 1, characterized in that, The cleaning agent comprises the following components by volume fraction: 5 parts polyacrylate, 5 parts phosphonocarboxylic acid copolymer, 15 parts ceramic dispersant, 20 parts sodium polyacrylate, 4 parts sodium hydroxide, and 5 parts sodium dodecylbenzenesulfonate.

4. The cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes according to claim 1, characterized in that, The cleaning agent comprises the following components by volume fraction: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate.

5. The cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes according to claim 1, characterized in that, The cleaning agent is prepared by mixing the following components according to volume fractions: 2 parts polyacrylate, 2 parts phosphonocarboxylic acid copolymer, 10 parts ceramic dispersant, 10 parts sodium polyacrylate, 2 parts sodium hydroxide, and 2 parts sodium dodecylbenzenesulfonate.

6. The cleaning agent for silica scale buildup on reverse osmosis membranes and nanofiltration membranes according to any one of claims 1-5, characterized in that, The silica scale is any one or a combination of at least two of silicate scale or colloidal silica.

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