Multifunctional scale and corrosion inhibitor for reverse osmosis system and preparation method thereof

Abstract

A multifunctional scale inhibitor dispersant applied to a reverse osmosis system and a preparation method thereof, the composition ingredients are as follows in terms of mass fraction: CS-GLU: 6-9 parts, ascorbic acid: 1.5-2.5 parts, polyaspartic acid: 3-4.5 parts, sodium gluconate: 1-2 parts, polyethylene glycol: 2-4 parts, nano-SiO2: 0.005-0.03 parts, triammonium citrate: 1-3.5 parts, acetic acid: 3-6 parts, urea: 0.2-0.5 parts, EDTA-2Na: 1-2.5 parts, and deionized water: 65.47-81.295 parts. Traditional scale inhibitors only rely on chemical chelation, without repair and antioxidant capacity. The product breaks through the single function limitation through the synergy of chemical scale inhibition and physical repair (film formation + nano filling); the built-in antioxidant system (ascorbic acid + EDTA) in the product replaces the dangerous reducing agent, prolonging the film life; traditional scale inhibitors are sensitive to high-valence ions such as Fe 3+ , Al 3+ , etc., and the applicable water quality range is narrow. The product is designed with amphoteric ion characteristics through charge matching, avoiding the deposition pollution of traditional anionic scale inhibitors.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a multifunctional scale inhibitor and dispersant for use in reverse osmosis systems and its preparation method. Background Technology

[0002] Reverse osmosis membranes possess excellent properties such as high flux, high desalination rate, and high mechanical and chemical strength, and are currently widely used in various industries including power, chemical, environmental protection, and printing and dyeing. With the popularization and development of reverse osmosis membranes, membrane fouling and chlorination degradation of the membrane surface active layer are problems present in almost all reverse osmosis systems, severely restricting their promotion and application. Although most contaminants can be removed and membrane performance restored after membrane fouling through physical and chemical cleaning, over time, difficult-to-clean contaminants accumulate, leading to increasingly poor cleaning effects and difficulty in restoring membrane flux. Furthermore, chemical cleaning exacerbates the decline in membrane desalination performance, causing the product water quality to fail to meet standards, necessitating membrane replacement. The surface active layer of the reverse osmosis membrane plays a crucial role in the selective separation performance of the membrane; however, this active layer has poor chlorine resistance, making it highly susceptible to chlorine degradation, causing irreversible damage, reducing membrane performance, and shortening membrane lifespan. Current research focuses on modifying reverse osmosis membranes with novel materials to enhance the hydrophilicity and chlorine resistance of the membrane separation layer, thereby optimizing the selective permeability, chlorine resistance, and antifouling performance of the reverse osmosis membrane. To address membrane fouling and chlorination issues, the most economical and commonly used method is to add antiscalants and reducing agents to reverse osmosis membranes, thereby mitigating fouling and preventing chlorination. Therefore, the performance of these antiscalants and reducing agents is crucial to the operational efficiency of reverse osmosis systems.

[0003] The separation layer on the surface of a reverse osmosis membrane is formed by the interfacial polymerization of polyamides and polyacrylamides. It's unavoidable that excess acrylamide groups will remain on the membrane surface, giving it a negative charge. Therefore, to prevent scale inhibitors from depositing on the membrane surface and causing chemical fouling, currently available reverse osmosis membrane scale inhibitors are all anionic, such as hydroxyethylidene diphosphonic acid (HEDPA), sodium ethylenediaminetetramethylenephosphonate (EDTMPS), sodium polyacrylate (PAAS), and hydrolyzed polymaleic anhydride (HPMA). Researchers are now focusing on non-anionic scale inhibitors, but no substantial progress has been reported. Meanwhile, to prevent residual chlorine or other strong oxidizing substances in the water from damaging the membrane separation layer, a reducing agent is usually added before the reverse osmosis system; the most commonly used reducing agent is sodium bisulfite.

[0004] In the pretreatment process of reverse osmosis systems, coagulants, including aluminum and iron salts, are typically added. Residual aluminum and iron ions not only readily adsorb onto the negatively charged membrane surface, forming a precipitate layer that clogs the reverse osmosis membrane and degrades the system's performance, but also significantly affect the performance of the membrane antiscalant. (Reference: "Fe...") 3+ And Al 3+ The effects of iron and aluminum ions on reverse osmosis membrane antiscalants are detailed in the articles "The Influence of Iron and Aluminum Ions on Antiscalant Effects" (Zhou Baiqing et al., *Water Treatment Technology*) and "The Influence of Harmful Ions on Reverse Osmosis Antiscalants" (Xu Houdao et al., *Chemical Industry and Engineering Technology*). Experiments have shown that when the iron ion concentration in water exceeds 5 mg / L, the antiscaling effect of PAAS and HPMA decreases by more than 60%. Iron and aluminum ions also significantly reduce the antiscaling effect of antiscalants on barium sulfate scale. Most anionic membrane antiscalants have poor tolerance to iron and aluminum ions. Furthermore, the reducing agent sodium bisulfite is unstable and is classified as a Class B hazardous material.

[0005] These anionic scale inhibitors cannot be effectively adsorbed in the initial stage due to charge repulsion, resulting in a high concentration region near the membrane-liquid interface. The scale inhibitor molecules form aggregates through hydrophobic interactions or hydrogen bonds. These aggregates then impact the membrane surface under shear forces, partially embedding themselves in the membrane pores or adsorbing onto the membrane surface. Fe 3+ Al 3+ It complexes with scale inhibitors to form precipitates, which further fill the voids in the aggregates, forming a dense fouling layer. The thickening of the fouling layer leads to narrowing of water flow channels, increased membrane pressure differential, a significant decrease in flux, and deterioration of membrane performance.

[0006] Chinese patent application CN202010971612.0 discloses a high-efficiency, multifunctional, and multipurpose reverse osmosis membrane antiscalant, its preparation method, and its application. However, the raw materials used in this technical solution mainly include sodium ethylenediamine di-o-hydroxyphenylacetate, polyaminopolyether methylenephosphonic acid, hydrolyzed polymaleic anhydride, acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, 2,2-dibromo-3-hypochlorous acid propionamide, and isothiazolinone. Sodium ethylenediamine di-o-hydroxyphenylacetate, due to its excessively high phosphorus and nitrogen content, has been included in the "Restricted Import of Phosphorus-Containing Raw Materials" list by the national environmental protection department. Furthermore, isothiazolinone in the formulation is highly toxic. Most importantly, the tolerance of the antiscalant to iron and aluminum ions in this solution is not described.

[0007] Chinese patent application CN202211003468.7 discloses a multi-functional scale inhibitor / dispersant that can effectively control scaling and microbial growth under conditions of high hardness, high alkalinity, high iron, high sulfate, high pH, ​​high organic matter, and high microbial content. However, the raw materials used in this technical solution also contain toxic isothiazolinones, and the dispersing ability of the membrane scale inhibitor for insoluble iron and aluminum compounds is not described in detail.

[0008] Chinese patent application CN202211672033.1 discloses a scale inhibitor for RO membrane recovery of high-salinity wastewater and its preparation method. The scale inhibitor prepared in this method has excellent silicon and aluminum inhibition properties, and it also has excellent dispersibility for iron oxide. However, the raw material uses a large amount of phosphorus-containing compounds, which are one of the nutrient sources for microorganisms, easily nourishing bacteria and algae, causing eutrophication of the environmental water body, and resulting in water pollution. Summary of the Invention

[0009] This invention provides a multifunctional scale inhibitor and dispersant, as well as its preparation method, which not only has a certain repair and protection effect on reverse osmosis membranes and prevents membrane chlorination, but also keeps dissolved iron or aluminum stable in water, has a good dispersion effect on insoluble iron and aluminum compounds, prevents iron and aluminum deposition and scaling, and effectively controls the formation of scale such as CaCO3 and CaSO4.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A multifunctional scale inhibitor and dispersant for use in reverse osmosis systems comprises, by weight parts: CS-GLU: 6-9 parts, ascorbic acid: 1.5-2.5 parts, polyaspartic acid: 3-4.5 parts, sodium gluconate: 1-2 parts, polyethylene glycol: 2-4 parts, nano-SiO2: 0.005-0.03 parts, triammonium citrate: 1-3.5 parts, acetic acid: 3-6 parts, urea: 0.2-0.5 parts, EDTA-2Na: 1-2.5 parts, and deionized water: 65.47-81.295 parts.

[0012] The preferred multifunctional scale inhibitor for reverse osmosis membranes is prepared by mixing and dissolving the following components in parts by mass: CS-GLU: 8 parts, ascorbic acid: 2 parts, triammonium citrate: 1.5 parts, polyaspartic acid: 3.5 parts, sodium gluconate: 2 parts, nano-SiO2: 0.01 parts, polyethylene glycol: 3 parts, acetic acid: 5 parts, urea: 0.4 parts, EDTA-2Na: 1.5 parts, and deionized water: 73.09 parts.

[0013] The CS-GLU is a cross-linked product with chitosan (CS) and L-glutamic acid (GLU) as the main raw materials.

[0014] The preparation method of the CS-GLU is as follows:

[0015] 1) Raw material pretreatment: Dissolve chitosan in a 1%–3% acetic acid solution, stir magnetically at 500–1000 rpm, at 18–25°C, for 4–6 hours until completely dissolved. Filter through a 0.45 μm filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water, stir at 300–500 rpm, at 18–25°C, for 0.5–1 hour until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a 1:1 volume ratio, stir magnetically at 200–500 rpm, at 18–25°C, for 0.5–1 hour to ensure uniform mixing.

[0016] 2) Benzaldehyde protection reaction: Benzaldehyde is slowly added dropwise to the mixed solution obtained in step 1) at a rate of 0.5-2 mL / min. Under nitrogen protection, the mixture is kept in a constant temperature water bath at 55-65℃ with continuous stirring at a speed of 300-500 rpm. The pH is adjusted to 4.4-4.6 with 1-2 mol / L NaOH or 0.5-1 mol / L acetic acid. The reaction time is 5-7 hours.

[0017] 3) Purification and drying: After the reaction is completed, cool to 20-25℃, add anhydrous ethanol to precipitate the product, let stand for 0.5-1 hour, centrifuge for 10-20 minutes at 5000-8000 rpm, and discard the supernatant; wash the precipitate 2-4 times with 60-70% ethanol to remove residual benzaldehyde; vacuum dry for 24-48 hours at 35-45℃ to obtain a white powdery protective product.

[0018] 4) Glyoxal crosslinking: Dissolve the protected product in deionized water and sonicate; 0.5–1 hour, frequency 40–50 kHz. Incubate in a 45–50°C water bath, adjust pH to 5.4–5.6 with phosphate buffer, add glyoxal, stir for 4–5 hours at 300–500 rpm; then add anhydrous ethanol to terminate the reaction, centrifuge for 10–20 minutes at 5000–8000 rpm, collect the precipitate; wash 2–4 times with an ethanol-water (7:3, v / v) mixture to remove unreacted glyoxal.

[0019] 5) Hydrolysis with dilute hydrochloric acid: Disperse the crosslinking product from step 4) in a 0.1–0.3 mol / L dilute HCl solution, stir in a water bath at 35–45°C for 2–3 hours at a speed of 300–500 rpm; adjust the pH to 6.8–7.2 with 1–3 mol / L NaOH; place it in a dialysis bag with a molecular weight cutoff of 3500 Da, dialyze with flowing deionized water for 24–48 hours, changing the water every 4–6 hours to remove benzaldehyde and small molecule impurities; then freeze-dry at -50 to -35°C for 24–48 hours to obtain a white porous solid product, which is CS-GLU.

[0020] A method for preparing a multifunctional scale inhibitor and dispersant for use in reverse osmosis systems, specifically comprising:

[0021] 1) Solvent premixing and main agent dissolution: Mix deionized water, acetic acid and urea, and slowly add CS-GLU while stirring at 35-45℃ for 2-4 hours to dissolve;

[0022] 2) Functional components are added in steps: Ascorbic acid and triammonium citrate are added in sequence, and the pH is adjusted to 5.5-6.0; then polyaspartic acid and sodium gluconate are added, and the mixture is stirred for 45-90 minutes.

[0023] 3) Integration of nanomaterials and wetting agents: Disperse nano-SiO2 ultrasonically for 45-90 minutes at a frequency of 40-50kHz, add it to the system obtained in step 2), then add polyethylene glycol, and mix and stir for 1-2 hours;

[0024] 4) Stabilization treatment: Add EDTA-2Na to inhibit oxidation, filter with a 0.8μm filter membrane to remove undissolved impurities, fill in the dark, and store at 4-10℃ (shelf life 60 days).

[0025] The method of using the multifunctional scale inhibitor and dispersant in the reverse osmosis system specifically includes:

[0026] 1) Before performing repairs, the reverse osmosis membrane system must be pretreated and cleaned to ensure that there are no contaminants deposited on the membrane surface. Commonly used cleaning agents include citric acid, sodium hydroxide, and sodium dodecyl sulfate. The specific proportions and operations should be carried out in accordance with the standardized cleaning methods recommended in the "Technical Specification for Cleaning Membrane Elements of Reverse Osmosis Systems" or the membrane manufacturer's manual.

[0027] 2) The system collects and records the membrane system's baseline operating parameters: inlet water pressure (MPa), system pressure difference (MPa), desalination rate (%), and standardized permeate flow rate (m³). 3 ( / h) etc.

[0028] 3) Use reverse osmosis permeate to prepare the repair solution, and control the concentration at 0.5-1.0 kg / 1000 L (equivalent to 500-1000 ppm by mass-volume ratio). Complete dissolution is achieved by mechanical stirring or circulating pump. The daily scale inhibitor dosage is: based on the influent flow rate, add 2-6 mg / L continuously for compliant systems. It is recommended to use an online dilution metering pump to accurately control the dosage.

[0029] 4) Perform gradient pressure circulation treatment: The first stage is high-flow-rate flushing, with full-flow circulation for 5 to 15 minutes, and the circulation flow rate is not less than 110% of the design value (design value of low-pressure flushing flow rate of reverse osmosis system); the second stage is enhanced permeation, gradually increasing the inlet water pressure to 1.1 to 1.5 times the operating pressure, controlling the ratio of concentrate to product water flow rate to be less than 3, and continuously circulating for 20 to 40 minutes.

[0030] 5) High-pressure operation verification: The system is switched to normal pressure (or +5% overpressure) operation mode. The desalination rate is monitored in real time. If the expected value is not reached, steps 4-5 are repeated. The maximum number of repairs for a single system should not exceed 3.

[0031] The multifunctional scale inhibitor CS-GLU uses chitosan (CS) and L-glutamic acid (GLU) as main raw materials. Benzaldehyde is used to protect the amino groups in chitosan and L-glutamic acid, allowing the amino groups to react with benzaldehyde to form stable Schiff bases. Protecting the amino groups prevents excessive reaction between the amino groups and glyoxal during subsequent cross-linking, ensuring controllable cross-linking sites. Then, glyoxal is used as a short-chain cross-linking agent, utilizing its two aldehyde groups to undergo condensation reactions with the remaining hydroxyl groups (or unprotected amino groups) of the chitosan Schiff base and the L-glutamic acid Schiff base, forming a cross-linked network. Finally, under dilute acid conditions, the Schiff base hydrolyzes and breaks down, releasing free amino groups while retaining the cross-linked structure, thus preparing CS-GLU with a three-dimensional network structure. Through an amino protection-cross-linking-deprotection strategy, CS-GLU, possessing both repair and scale inhibition functions, was successfully prepared. Its repair mechanism is based on chemical bond reconstruction and physical barrier protection. The amino group of CS-GLU undergoes a nucleophilic substitution reaction with the broken amide bond (-CO-NH-) of the polyamide reverse osmosis membrane to form a new covalent bond (-CO-NH-CH2-), directly repairing microcracks on the membrane surface. CS-GLU can also form a dense hydrophilic gel membrane on the membrane surface, adsorbing onto the membrane surface through hydrogen bonds and van der Waals forces, preventing free chlorine from permeating and attacking the amide bond, and reducing the risk of membrane oxidative damage. In addition, the amino and carboxylic acid groups in CS-GLU can scavenge free radicals and inhibit chlorination reactions, further protecting the membrane structure. Its scale inhibition mechanism relies on the synergistic effect of chelation, lattice distortion, and dispersion. CS-GLU has abundant functional groups and a cross-linked network structure. The amino and carboxylic acid groups form bifunctional groups that can synergistically chelate Ca. 2+ 、Sr 2+ Ba 2+ Plasma, by forming stable and soluble complexes, inhibits the nucleation of scale crystals such as CaCO3 and CaSO4. The CS-GLU cross-linked structure adsorbs onto the CaCO3 crystal face, interfering with crystal orientation and inhibiting scale growth. The zwitterionic properties of CS-GLU (weakly positive charge at pH 5.5-6.0) are dynamically adjusted (-NH4+). 3+The CS-GLU membrane achieves weak net positive charge adsorption on the membrane surface ( / -COO- balance), promoting uniform adsorption and avoiding strong electrostatic repulsion. It adsorbs negatively charged Fe2O3 / Al(OH)3 colloidal particles through charge neutralization, forming a stable suspension. The three-dimensional network structure of CS-GLU can also physically trap Fe2O3 / Al(OH)3 colloidal particles through steric hindrance, preventing particle aggregation. Compared to ordinary chitosan, the nitrogen and oxygen atoms of the amino and hydroxyl groups in the chitosan molecule have lone pairs of electrons, which can bind with metal ions through coordinate bonds, thus playing a scale inhibition role. Simultaneously, chitosan binds to the membrane surface through hydrogen bonding of amino and hydroxyl groups, and adheres more tightly to the membrane surface through electrostatic interactions, thereby restoring the selective permeability of the reverse osmosis membrane and playing a repair role. CS-GLU introduces carboxylic acid groups of glutamic acid and forms a three-dimensional cross-linked network. The introduced carboxylic acid groups provide additional chelating sites over a wider pH range (pH 3-8), enhancing the adhesion of Fe... 3+ Al 3+ The coordination ability significantly enhances chelation capacity and scale inhibition efficiency. The carboxylic acid group and amino group synergistically form a multidentate ligand, increasing the stability of the complex by 2-3 times, especially for multivalent metal ions (Ca). 2+ Fe 3+ CS-GLU exhibits superior scale inhibition capabilities compared to chitosan. Its covalent bond repair and nano-reinforcement network not only enhance repair efficiency but also form a long-lasting protective layer, significantly improving membrane durability and antifouling ability. In summary, CS-GLU, as the main agent in this multifunctional scale inhibitor, provides basic repair and scale inhibition capabilities, combining membrane repair, scale inhibition, and dispersion functions. Its amino groups repair amide bonds in the membrane, while its carboxylic acid chelates Ca... 2+ Fe 3+ In the cross-linked structure, the carboxylic acid groups and amino groups work together to form a dynamic chelating nanonetwork adsorption layer. The carboxyl groups in the adsorption layer can further chelate residual Ca permeating the membrane. 2+ This forms a "secondary scale barrier," achieving integrated and synergistic effects of scale inhibition and repair functions.

[0032] In this multifunctional scale inhibitor, ascorbic acid acts as both an antioxidant and a chlorine neutralizer, primarily serving to prevent membrane chlorination and promote synergistic repair. Ascorbic acid neutralizes residual chlorine in water through reduction, blocking its oxidative attack on the reverse osmosis membrane. Synergistically with the antioxidant properties of CS-GLU, it employs a dual-mechanism approach to scavenge free radicals: ascorbic acid directly reduces free radicals, while the amino groups in CS-GLU assist in scavenging through hydrogen donation, thereby increasing the total free radical scavenging rate and reducing membrane oxidative damage.

[0033] Polyaspartic acid in multifunctional scale inhibitors is a broad-spectrum scale inhibitor synergist. Polyaspartic acid binds to Ca through chelation via its carboxylic acid groups. 2+ It induces lattice distortion and forms a "multi-point anchoring" effect with CS-GLU, enhancing the support for Ca. 2+ 、Sr2+ Ba 2+ The chelating ability of polyaspartic acid long-chain sterically hindered dispersible colloidal particles, in synergy with the main agent CS-GLU carboxylic acid, enhances the dispersion of Fe2O3 / Al(OH)3 colloids.

[0034] In multifunctional scale inhibitors, triammonium citrate primarily functions as a pH buffer and performs competitive adsorption. Triammonium citrate forms a buffer pair with acetic acid, stabilizing the pH environment and maintaining the activity of CS-GLU and the stability of the agent. Through its tricarboxylic acid structure, triammonium citrate competitively adsorbs with polyaspartic acid, forming a dicarboxylic acid network and enhancing its adsorption on Ca2+. 2+ chelation capacity.

[0035] In multifunctional scale inhibitors, EDTA-2Na acts as an oxidation stabilizer and metal ion control agent. Ascorbic acid is easily oxidized and decomposed under acidic conditions (generating dehydroascorbic acid), reducing chlorine neutralization efficiency. EDTA-2Na chelates metal ions (Fe... 3+ / Cu 2+ It inhibits the oxidation chain reaction and prolongs the half-life of ascorbic acid. The hexadecimal coordination structure of EDTA-2Na can interact with Fe... 3+ Al 3+ Forms a 1:1 stable complex, targeting and chelating Fe. 3+ Al 3+ Free Fe 3+ Al 3+ When the concentration is reduced to below 0.1 mg / L, it prevents the scale inhibitor from interfering with and binding with it, thus playing a role in controlling metal ions.

[0036] Sodium gluconate acts as a dispersant in this multifunctional scale inhibitor, enhancing dispersion stability by adsorbing microcrystalline particles and reducing physical deposition. Together with PASP, it interferes with CaCO3 crystal growth, synergistically inhibiting scale and improving lattice distortion. Sodium gluconate and triammonium citrate work synergistically to maintain the system pH, jointly achieving Fe... 3+ Al 3+ Targeted clearance optimizes the local environment and enhances the solubility of CS-GLU and the stability of ascorbic acid.

[0037] In this multifunctional scale inhibitor, polyethylene glycol (PEG) acts as a membrane wetting and dispersing agent. PEG reduces the membrane surface contact angle, decreases particle deposition caused by concentration polarization, increases water flux, and alleviates flux decline due to the repair process. PEG wetting synergistically repairs reverse osmosis membranes with CS-GLU, reducing the surface energy of the repair layer, promoting uniform CS-GLU spreading, and improving CS-GLU coverage. The ether bonds in PEG are adsorbed onto the surface of Fe2O3 / Al(OH)3 particles via hydrogen bonds, forming a flexible polymer layer that enhances steric hindrance and optimizes colloidal dispersion.

[0038] In this multifunctional scale inhibitor, nano-SiO2 primarily functions as a dispersant and wetting agent. Nano-SiO2 adsorbs Fe2O3 particles through its surface hydroxyl groups, dispersing the colloidal particles. The combination of nano-SiO2 and polyethylene glycol (PEG) provides rigid support from the nanoparticles and enhances flexibility through the long chains of PEG, forming a "rigid-flexible" dispersion layer. Furthermore, nano-SiO2 acts as a physical cross-linking point, enhancing the mechanical strength of the repair layer and ensuring its integrity even under high pressure (1.6 MPa).

[0039] In multifunctional scale inhibitors, acetic acid and urea are solubilizing agents. CS-GLU is prone to gel formation, which leads to excessively high system viscosity. By using a mixed solvent of acetic acid and water and urea, the intermolecular hydrogen bonding of CS-GLU is reduced, gelation is inhibited, and the solubility of CS-GLU is improved.

[0040] The interfacial interactions among the various components of the aforementioned multifunctional antiscalant for reverse osmosis membranes achieve a high degree of integration of antiscaling, dispersion, and repair functions through multi-level chelation, nano-polymer synergistic dispersion, and a dynamic repair network. CS-GLU, as the core carrier, exhibits charge complementarity with triammonium citrate and polyaspartic acid, and forms a stable synergistic system with triammonium citrate, PASP, and nano-SiO2 through electrostatic, hydrogen bonding, and covalent interactions, significantly improving the overall performance of the reverse osmosis membrane under extreme water quality conditions. The carboxylic acid groups of CS-GLU form multi-level chelation sites with triammonium citrate and polyaspartic acid, expanding the chelation network and increasing chelation capacity. CS-GLU macromolecular chelation, polyaspartic acid medium-molecular chelation, and triammonium citrate small-molecule chelation form a hierarchical chelation system, covering scale inhibition at all scale scales from ionic to microcrystalline states. The amino groups of CS-GLU exhibit charge complementarity with the surface charge of nano-SiO2, enhancing colloidal adsorption stability. Simultaneously, the nano-SiO2 is embedded in the chitosan network, improving the density of the repair layer. In the multifunctional scale inhibitor, triammonium citrate and polyaspartic acid chelate free ions in the early stage to reduce crystal nucleation. In the middle stage, nano-SiO2 and polyethylene glycol inhibit particle aggregation and ensure a clean repair interface. In the later stage, CS-GLU dynamically fills cracks and blocks scale adhesion sites, achieving chelation-dispersion-repair linkage.

[0041] This invention systematically solves the problems of charge limitation, metal ion interference, reducing agent hazards, and short membrane life of similar domestic products through six major advantages: non-anionic scale inhibition design, high tolerance to metal ions, safe antioxidant system, nano-enhanced dispersion, dynamic membrane repair, and multi-component synergy. It achieves a leap from "passive scale inhibition" to "active protection + repair," providing a brand-new solution for the long-term stable operation of reverse osmosis membranes.

[0042] Compared with existing technologies, the beneficial effects of this invention are:

[0043] 1) Synergistic design of chemical scale inhibition and physical remediation to achieve integrated remediation and scale inhibition;

[0044] This product achieves functional protection and damage repair of reverse osmosis membranes through the synergy of chemical scale inhibition (chelation + lattice distortion) and physical repair (film formation + nanofilling), overcoming the limitations of single-function approaches. The product incorporates an antioxidant system (ascorbic acid + EDTA-2Na) to replace hazardous reducing agents. This system is not only highly safe but also eliminates the need for additional hazardous chemicals, simplifying the pretreatment process and extending membrane life.

[0045] 2) Non-anionic scale inhibitor design overcomes the limitation of negative charge on membrane surface;

[0046] This product's non-anionic design achieves a performance breakthrough through the following innovations: Its zwitterionic properties optimize adsorption assistance, avoiding the low adsorption efficiency, abnormal aggregation in solution, and co-contamination by metal ions caused by the charge repulsion between traditional anionic scale inhibitors and the reverse osmosis membrane surface, which ultimately leads to membrane flux decline and frequent cleaning. This process is essentially the result of the combined effects of interfacial instability dominated by electrostatic repulsion and secondary contamination caused by chemical complexation. This product's non-anionic scale inhibitor systematically solves the inherent defects of traditional technologies through charge adaptation, gradient chelation, and nano-enhanced dispersion.

[0047] 3) Highly efficient metal ion chelation and high tolerance, solving the problem of iron / aluminum ion interference;

[0048] Conventional scale inhibitors for Fe 3+ Al 3+ The tolerance for these substances is generally low. This product utilizes a gradient chelation system constructed from polyaspartic acid, sodium gluconate, and EDTA-2Na: sodium aspartate and sodium gluconate preferentially chelate Ca through their polycarboxylic acid structure. 2+ Mg 2+ It inhibits scale formation; EDTA-2Na, as a strong chelating agent, targets and binds Fe. 3+ Al 3+ High-valence ions form stable complexes, significantly reducing their concentration's interference with scale inhibition. Simultaneously, the dynamic pH buffering effect of triammonium citrate further reduces metal ion precipitation, preventing membrane clogging.

[0049] 4) Nanomaterials enhance dispersion and physical scale inhibition;

[0050] Conventional products rely on a single chemical scale inhibition mechanism, while this product introduces nano-SiO2: through ultrasonic dispersion, nano-sized particles are formed and adsorbed onto the surface of microcrystals, providing a steric hindrance effect to prevent crystal aggregation; nano-SiO2 forms a hydrogen bond network with the carboxyl groups of CS-GLU, enhancing the adhesion of the agent to the membrane surface and improving scale inhibition durability. In addition, the mechanical filling effect of nano-SiO2 can repair microcracks on the membrane surface and reduce contaminant adhesion.

[0051] 5) Dynamic film formation and self-healing functions extend membrane life;

[0052] Conventional scale inhibitors lack membrane repair capabilities. This product, CS-GLU, forms a dense polymer membrane on the membrane surface, covering defective areas, and achieves dynamic repair through hydrogen bonding networks between hydroxyl groups and the amide groups of the polyamide membrane. Simultaneously, the hydrophilic long chains of polyethylene glycol encapsulate nano-SiO2, forming a lubricating layer that reduces membrane surface roughness and minimizes contaminant deposition. This dual protection mechanism of "chemical adsorption + physical filling" significantly extends the service life of reverse osmosis membranes. Attached Figure Description

[0053] Figure 1 This is a scale inhibition performance diagram of CS-003 in Example 3.

[0054] Figure 2 The graph shows the scale inhibition performance of CS-003 and ATMP in Example 3.

[0055] Figure 3 This is a graph showing the changes in desalination rate versus influent pressure after standardization in Example 4. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the embodiments, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0057] This invention discloses a multifunctional scale inhibitor and dispersant for reverse osmosis systems, achieving integrated "repair-scale inhibition-dispersion" functions. This scale inhibitor is a composite reagent. The raw material specifications of this multifunctional scale inhibitor for reverse osmosis membranes are shown in Table 1.

[0058] Table 1 Specifications of the medicines in the formula

[0059]

[0060]

[0061] Note: Chitosan has a molecular weight of 10-50 kDa; nano-SiO2 has an average particle size of 20 nm, and its surface is treated with KH590, resulting in a specific surface area of ​​230 m². 2 / g, density 2.2-2.6g / cm³ 3 Its crystal form is spherical.

[0062] Example 1: A method for preparing a multifunctional scale inhibitor for reverse osmosis membranes, comprising the following steps:

[0063] (1) Preparation of chitosan-L-glutamic acid cross-linked product CS-GLU:

[0064] ① Raw material pretreatment: Dissolve chitosan in 1% acetic acid solution, stir magnetically at 500 rpm, 25℃ for 4 hours until completely dissolved, and filter through a 0.45 μm filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water, stir at 300 rpm, 25℃ for 1 hour until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a 1:1 volume ratio, stir magnetically at 200 rpm, 25℃ for 1 hour to ensure uniform mixing.

[0065] ② Benzaldehyde protection reaction: Benzaldehyde was slowly added dropwise to the mixed solution at a rate of 1 mL / min. Under nitrogen protection, the mixture was kept in a constant temperature water bath at 60°C with continuous stirring at 400 rpm. The pH was adjusted to 4.5 with 1 mol / L NaOH, and the reaction time was 6 hours.

[0066] ③ Purification and drying: After the reaction is complete, cool to 25℃ and add anhydrous ethanol to precipitate the product. Let stand for 0.5 hours, centrifuge for 10 minutes at 8000 rpm, and discard the supernatant. Wash the precipitate three times with 70% ethanol to remove residual benzaldehyde. Vacuum dry for 24 hours at 40℃ to obtain a white powdery protective product.

[0067] ④ Glyoxal crosslinking: Dissolve the protected product in deionized water and sonicate for 0.5 hours at 40 kHz. Incubate in a 50°C water bath, adjust the pH to 5.5 with phosphate buffer, add glyoxal, and stir for 4 hours at 400 rpm. Terminate the reaction with anhydrous ethanol, centrifuge for 10 minutes at 8000 rpm, and collect the precipitate. Wash three times with an ethanol-water (7:3, v / v) mixture to remove unreacted glyoxal.

[0068] ⑤ Hydrolysis with dilute hydrochloric acid: The cross-linking product was dispersed in 0.1 mol / L HCl solution and stirred in a water bath at 40°C for 2 hours at 300 rpm. The pH was adjusted to 7.0 with 1 mol / L NaOH. The mixture was placed in a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with flowing deionized water for 48 hours, changing the water every 6 hours to remove benzaldehyde and small molecule impurities. The mixture was then freeze-dried at -50°C for 48 hours to obtain a white porous solid product.

[0069] (2) Preparation of multifunctional antiscalant for reverse osmosis membranes (CS-001):

[0070] ① Solvent premixing and main agent dissolution: Mix 63.09 parts deionized water, 5 parts acetic acid, and 0.4 parts urea, and slowly add 8 parts CS-GLU while stirring at 40°C, and dissolve for 2 hours.

[0071] ② Functional components are added in steps: 2 parts ascorbic acid and 1.5 parts triammonium citrate are added sequentially, and sodium hydroxide is added to adjust the pH to 5.5. Then, 3.5 parts polyaspartic acid and 2 parts sodium gluconate are added, and the mixture is stirred for 45 minutes.

[0072] ③ Integration of nanomaterials and wetting agents: 0.01 parts of nano SiO2 were ultrasonically dispersed in 10 parts of deionized water for 45 min at a frequency of 40 kHz, and then added to the system. Subsequently, 3 parts of polyethylene glycol were added and stirred for 1 hour.

[0073] ④ Stabilization treatment: Add 1.5 parts of EDTA-2Na to inhibit oxidation, filter with a 0.8μm filter membrane to remove undissolved impurities, fill in the package away from light, and store at 4℃.

[0074] To verify the antioxidant capacity of the multifunctional scale inhibitor CS-001 on reverse osmosis membranes and quantify its effectiveness in maintaining membrane desalination rate in chlorinated water, the specific operation was carried out in accordance with GB / T 32373-2015.

[0075] Experimental and control groups were set up, with each group containing 3 membrane samples: CS-001 treatment group: reverse osmosis membrane (model: BW30-400IG, Dow) was immersed in an aqueous solution containing 5 ppm residual chlorine (adjusted with NaClO) and CS-001 (concentration 100 ppm) was added; untreated group: the same membrane was immersed in an aqueous solution containing 5 ppm residual chlorine without adding any reagents; blank control group: the membrane was immersed in pure water without residual chlorine to verify the stability of the basic desalination rate.

[0076] Experimental conditions: The temperature was controlled at 25±1℃ in a constant temperature water bath, the pH was maintained at 6.5±0.2 in phosphate buffer, the long-term exposure was simulated for 60 days, the residual chlorine concentration was monitored daily, and NaClO was added to maintain 5±0.5ppm.

[0077] Test method: The test solution simulates brackish water, 2000ppm NaCl solution, test pressure 15.5 bar, test frequency, desalination rate is measured once every 24 hours.

[0078] The experimental results and data analysis are shown in Table 2:

[0079] Table 2. Trend of desalination rate in Example 1

[0080]

[0081]

[0082] Accelerated chlorination experiments confirmed that in the CS-001-treated group, the desalination rate decreased by only 1.1% after 60 days. CS-001 effectively protects the reverse osmosis membrane from oxidative damage caused by residual chlorine, and the desalination rate remained above 98% after 60 days. In the untreated group, the desalination rate plummeted by 13.7% after 3 days and dropped to 41.6% after 60 days, indicating severe membrane performance degradation. In the blank control group, under conditions without residual chlorine, the membrane desalination rate naturally decreased by 0.6%, demonstrating the stability of the experimental environment. CS-001 is suitable for protecting reverse osmosis membranes in high-chlorine water quality for long-term stable operation.

[0083] The repair effect of CS-001 on chlorinated reverse osmosis membranes was verified by quantitative indicators such as flux and desalination recovery rate to clarify the repair effect.

[0084] The reverse osmosis membrane was immersed in a 200 mg / L NaClO solution (pH 4.0) and kept at 40°C for 1 hour. After chlorination, the initial flux of the membrane increased from 52.2 L / (m²). 2 The concentration of ·h) increased to 62.5 L / (m 2 (·h), the desalination rate decreased from 98.8% to 91.2%. CS-001 and chitosan were used to repair the chlorinated membrane.

[0085] After chlorination, the membranes were immersed in five solutions: 0.5%, 1%, 2% CS-001, and 1% chitosan, with three membrane samples in each solution. The solutions were kept at 40°C for 2 hours. The test solution simulated brackish water, using a 2000ppm NaCl solution, and the test pressure was 15.5 bar.

[0086] CS-001, through a combined repair mechanism of cross-linking, pore plugging, and chelation, achieves a reasonable 7% decrease in membrane flux and a 6.1% increase in desalination rate after chlorination. This is superior to the 16% decrease in flux and 4.2% increase in desalination rate achieved by chitosan alone. After repair with 1.0% CS-001, the membrane desalination rate reaches 97.7%, close to the original membrane's 98.8%, meeting practical application requirements. Specific data are shown in Table 3.

[0087] Table 3 Performance test after repair in Example 1

[0088]

[0089] Example 2: A method for preparing a multifunctional scale inhibitor for reverse osmosis membranes, comprising the following steps:

[0090] (1) Preparation of chitosan-L-glutamic acid cross-linked product CS-GLU:

[0091] ① Raw material pretreatment: Dissolve chitosan in 1% acetic acid solution, stir magnetically at 500 rpm, 25℃ for 4 hours until completely dissolved, and filter through a 0.45 μm filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water, stir at 300 rpm, 25℃ for 1 hour until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a 1:1 volume ratio, stir magnetically at 200 rpm, 25℃ for 1 hour to ensure uniform mixing.

[0092] ② Benzaldehyde protection reaction: Benzaldehyde is slowly added dropwise to the mixed solution at a rate of 1 mL / min. Under nitrogen protection, the mixture is kept in a constant temperature water bath at 60°C with continuous stirring at a speed of 400 rpm. The pH is adjusted to 4.5 with 1 mol / L NaOH or acetic acid. The reaction time is 6 hours.

[0093] ③ Purification and drying: After the reaction is complete, cool to 25℃ and add anhydrous ethanol to precipitate the product. Let stand for 0.5 hours, centrifuge for 10 minutes at 8000 rpm, and discard the supernatant. Wash the precipitate three times with 70% ethanol to remove residual benzaldehyde. Vacuum dry for 24 hours at 40℃ to obtain a white powdery protective product.

[0094] ④ Glyoxal crosslinking: Dissolve the protected product in deionized water and sonicate for 0.5 hours at 40 kHz. Incubate in a 50°C water bath, adjust the pH to 5.5 with phosphate buffer, add glyoxal, and stir for 4 hours at 400 rpm. Terminate the reaction with anhydrous ethanol, centrifuge for 10 minutes at 8000 rpm, and collect the precipitate. Wash three times with an ethanol-water (7:3, v / v) mixture to remove unreacted glyoxal.

[0095] ⑤ Hydrolysis with dilute hydrochloric acid: The cross-linking product was dispersed in 0.1 mol / L HCl solution and stirred in a water bath at 40°C for 2 hours at 300 rpm. The pH was adjusted to 7.0 with 1 mol / L NaOH. The mixture was placed in a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with flowing deionized water for 48 hours, changing the water every 6 hours to remove benzaldehyde and small molecule impurities. The mixture was then freeze-dried at -50°C for 48 hours to obtain a white porous solid product.

[0096] (2) Preparation of multifunctional antiscalant for reverse osmosis membranes (CS-002):

[0097] ① Solvent premixing and main agent dissolution: Mix 63.685 parts of deionized water, 4 parts of acetic acid, and 0.3 parts of urea. Slowly add 7 parts of CS-GLU while stirring at 40°C and dissolve for 2 hours.

[0098] ② Functional components are added in steps: Add 2 parts ascorbic acid and 2 parts triammonium citrate in sequence, and adjust the pH to 5.5 with sodium hydroxide. Add 4 parts polyaspartic acid and 2 parts sodium gluconate, and stir for 45 minutes.

[0099] ③ Integration of nanomaterials and wetting agents: 0.015 parts of nano SiO2 were ultrasonically dispersed in 10 parts of deionized water for 45 min at a frequency of 40 kHz, and then added to the system. Subsequently, 4 parts of polyethylene glycol were added and stirred for 1 hour.

[0100] ④ Stabilization treatment: Add 1 part EDTA-2Na to inhibit oxidation, filter with a 0.8μm filter membrane to remove undissolved impurities, fill in the package away from light, and store at 4℃.

[0101] Verification of CS-002 on Fe 3+ Al 3+ The stabilizing ability and dispersion effect of the agent on insoluble compounds (such as Fe(OH)3 and Al(OH)3) were analyzed to quantify the performance differences with traditional scale inhibitors (such as HEDPA).

[0102] Dissolved Fe 3+ Al 3+ Retention rate test: Prepare a solution containing 5 mg / L Fe using deionized water. 3+ (Fe(NO3)3) and 3 mg / L Al 3+ The mother liquor of (AlCl3) was prepared. The reagent (CS-002 or HEDPA) was added in proportion and mixed thoroughly. The mixture was placed in a constant temperature shaker and reacted for 24 hours. Samples were taken at 0, 6, 12, and 24 hours, and the turbidity of the unfiltered water sample was directly measured. The sample was then immediately filtered through a 0.22 μm filter membrane to remove suspended particles. The dissolved retention rate was calculated according to formula (1):

[0103]

[0104] In equation (1), C 溶解态 After the mixture is reacted and filtered in a constant-temperature shaker, the Fe in the mixture is... 3+ And Al 3+ Concentration, mg / L; C 初始 To prepare Fe in the mother liquor 3+ And Al 3+ Concentration, mg / L.

[0105] Analysis and testing: ICP-OES (Fe 3+ Detection wavelength 259.94nm, Al 3+ The detection wavelength is 396.15 nm; the turbidity of the water sample was measured using a turbidimeter (HACH 2100N).

[0106] Experimental conditions: constant temperature shaker at 25±1℃, shaking frequency 150rpm, pH adjusted to 5.5±0.2 with triammonium citrate buffer, basic water quality: conductivity adjusted to 500μS / cm with NaCl, hardness 200mg / L (calculated as CaCO3).

[0107] The experimental results and data analysis are shown in Table 4:

[0108] Table 4 Dissolved Fe 3+ / Al 3+ Retention rate

[0109] Group Dosage concentration mg / L <![CDATA[Fe 3+ Retention rate (24h) <![CDATA[Al 3+ Retention rate (24h) CS-002 processing group 100 96.2％ 91.5％ HEDPA processing group 100 38.7％ 32.4％ Unprocessed group - 12.3％ 10.8％

[0110] Table 5 Turbidity Changes

[0111] Time (h) CS-002 Group (NTU) HEDPA Group (NTU) Unprocessed Group (NTU) 0 0.5 0.5 0.5 6 0.7 5.2 8.1 12 0.8 9.6 12.4 24 0.9 13.8 15.0

[0112] The above experiments show that CS-002 significantly improves Fe 3+ Al 3+ Its dissolved retention rate stabilizes turbidity below 1 NTU. Its performance far surpasses traditional scale inhibitors (such as HEDPA), making it suitable for long-term scale inhibition and dispersion in water bodies with high metal ion content.

[0113] Example 3: A method for preparing a multifunctional scale inhibitor for reverse osmosis membranes, comprising the following steps:

[0114] (1) Preparation of chitosan-L-glutamic acid cross-linked product CS-GLU:

[0115] ① Raw material pretreatment: Dissolve chitosan in 1% acetic acid solution, stir magnetically at 500 rpm, 25℃ for 4 hours until completely dissolved, and filter through a 0.45 μm filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water, stir at 300 rpm, 25℃ for 1 hour until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a 1:1 volume ratio, stir magnetically at 200 rpm, 25℃ for 1 hour to ensure uniform mixing.

[0116] ② Benzaldehyde protection reaction: Benzaldehyde is slowly added dropwise to the mixed solution at a rate of 1 mL / min. Under nitrogen protection, the mixture is kept in a constant temperature water bath at 60°C with continuous stirring at a speed of 400 rpm. The pH is adjusted to 4.5 ± 0.1 with 1 mol / L NaOH or acetic acid. The reaction time is 6 hours.

[0117] ③ Purification and drying: After the reaction is complete, cool to 25℃ and add anhydrous ethanol to precipitate the product. Let stand for 0.5 hours, centrifuge for 10 minutes at 8000 rpm, and discard the supernatant. Wash the precipitate three times with 70% ethanol to remove residual benzaldehyde. Vacuum dry for 24 hours at 40℃ to obtain a white powdery protective product;

[0118] ④ Glyoxal crosslinking: Dissolve the protected product in deionized water and sonicate for 0.5 hours at 40 kHz. In a 50°C water bath, adjust the pH to 5.5 ± 0.1 with phosphate buffer, add glyoxal, and stir for 4 hours at 400 rpm. Terminate the reaction with anhydrous ethanol, centrifuge for 10 minutes at 8000 rpm, and collect the precipitate. Wash three times with an ethanol-water (7:3, v / v) mixture to remove unreacted glyoxal.

[0119] ⑤ Hydrolysis with dilute hydrochloric acid: The cross-linking product was dispersed in 0.1 mol / L HCl solution and stirred in a water bath at 40°C for 2 hours at 300 rpm. The pH was adjusted to 7.0 ± 0.2 with 1 mol / L NaOH. The mixture was placed in a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with flowing deionized water for 48 hours, changing the water every 6 hours to remove benzaldehyde and small molecule impurities. The mixture was then freeze-dried at -50°C for 48 hours to obtain a white porous solid product.

[0120] (2) Preparation of multifunctional antiscalant for reverse osmosis membranes (CS-003):

[0121] ① Solvent premixing and main agent dissolution: Mix 60.995 parts of deionized water, 5 parts of acetic acid, and 0.5 parts of urea, and slowly add 8 parts of CS-GLU while stirring at 40°C, and dissolve for 2 hours;

[0122] ② Functional components are added in steps: 1.5 parts ascorbic acid and 3 parts triammonium citrate are added sequentially, and the pH is adjusted to 5.5 with sodium hydroxide. 4.5 parts polyaspartic acid and 2 parts sodium gluconate are added, and the mixture is stirred for 45 minutes.

[0123] ③ Integration of nanomaterials and wetting agents: 0.005 parts of nano SiO2 were ultrasonically dispersed in 10 parts of deionized water for 45 min at a frequency of 40 kHz, and then added to the system. Subsequently, 3 parts of polyethylene glycol were added and stirred for 1 hour.

[0124] ④ Stabilization treatment: Add 1.5 parts of EDTA-2Na to inhibit oxidation, filter with a 0.8μm filter membrane to remove undissolved impurities, fill in the package away from light, and store at 4℃.

[0125] Evaluation of static CaCO3 scale inhibition performance:

[0126] The scale inhibition performance was determined using the static concentration method. The specific steps were as follows: using fresh industrial water as the test water, adding the reagent, and evaporating and concentrating it to 1.5 times in an 80℃ constant temperature water bath, then sampling and analyzing the concentration of residual calcium ions in the water. A blank test was also performed simultaneously. The scale inhibition rate η was calculated according to formula (2):

[0127]

[0128] In formula (2), C2 is the stable calcium ion concentration (mg / L) after the addition of the reagent; C0 is the calcium ion concentration (mg / L) in the blank test; and C1 is the calcium ion content (mg / L) in the industrial fresh water. The higher the scale inhibition rate, the better the scale inhibition performance.

[0129] Water quality indicators for the test water: Ca 2+ The alkalinity and total hardness (all calculated as CaCO3) were 480 mg / L, 390 mg / L and 620 mg / L, respectively.

[0130] Evaluation of CaSO4 scale inhibition performance:

[0131] The static non-concentration experimental method was adopted. Water was used for preparation, with analytical grade anhydrous calcium chloride and sodium sulfate as reagents. The experimental water sample was prepared using deionized water. 2+ (Calculated as CaCO3) is 6800 mg / L, SO4 2- The concentration of Na₂SO₄ was 7100 mg / L, the pH was 6.5, the temperature was 80℃, and the constant temperature time was 16 h. The scale inhibition rate η was calculated according to formula (3):

[0132]

[0133] In formula (3): C2 is the Ca in the solution after heating when the scale inhibitor is added. 2+ Content, mg / L; CO is the Ca content in the solution after heating without scale inhibitor. 2+ Content, mg / L; C1 is the calcium content of the experimental water without scale inhibitor and without heating. 2+ Content (mg / L)

[0134] Depend on Figure 1 As can be seen, the scale inhibition rate of scale inhibitor CS-003 gradually increases with increasing dosage, and the increase is relatively large. The various molecules in CS-003 exhibit a synergistic effect, resulting in a scale inhibition rate of over 75% for CaCO3 scale at a concentration of 16 mg / L. At a concentration of 4 mg / L, the scale inhibition rate for CaSO4 scale reaches over 90%.

[0135] The static non-concentration experimental method was adopted. Water was used for preparation, with analytical grade anhydrous calcium chloride and sodium bicarbonate as reagents. The experimental water sample was prepared using deionized water. 2+ (Calculated as CaCO3) is 200 mg / L, HCO3 - (Calculated as CaCO3) is 600 mg / L, scale inhibitor CS-003 and ATMP are added at a concentration of 16 mg / L, Fe 3+ Al 3+ The concentration was added at a ratio of 2:1, and the mixture was kept at 80℃ for 8 hours. The experimental results are shown below. Figure 2 .

[0136] Figure 2 Show Fe 3+ / Al 3+ The effect of CS-003 and the traditional scale inhibitor ATMP on scale inhibition performance. CS-003 and ATMP achieved scale inhibition rates of 74.6% and 80.9% for CaCO3, respectively, with ATMP showing better initial performance. With the increase of Fe... 3+ / Al 3+ With increasing concentration, the efficiency of both scale inhibitors decreased, but ATMP was more significantly affected by metal ions. When Fe... 3+ / Al 3+ At a concentration of 10 mg / L, ATMP showed a 37.6% decrease in scale inhibition rate, while CS-003 only decreased by 8.8%. Notably, even at low metal ion concentrations (0.5-2 mg / L), ATMP exhibited a significant decrease in scale inhibition rate, while the decrease in CS-003 within this range was relatively gradual. This suggests that CS-003 has stronger tolerance to metal ions, and its molecular structure may possess better anti-interference capabilities. The experimental results indicate that in practical industrial applications, when Fe... 3+ / Al 3+ When contamination occurs, it is necessary to prioritize the use of scale inhibitors with stronger anti-interference properties, such as CS-003, to ensure the scale inhibition effect.

[0137] Example 4: A method for preparing a multifunctional scale inhibitor for reverse osmosis membranes, comprising the following steps:

[0138] (1) Preparation of chitosan-L-glutamic acid cross-linked product CS-GLU:

[0139] ① Raw material pretreatment: Dissolve chitosan in 1% acetic acid solution, stir magnetically at 500 rpm, 25℃ for 4 hours until completely dissolved, and filter through a 0.45 μm filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water, stir at 300 rpm, 25℃ for 1 hour until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a 1:1 volume ratio, stir magnetically at 200 rpm, 25℃ for 1 hour to ensure uniform mixing.

[0140] ② Benzaldehyde protection reaction: Benzaldehyde was slowly added dropwise to the mixed solution at a rate of 1 mL / min. Under nitrogen protection, the mixture was kept in a constant temperature water bath at 60°C with continuous stirring at a speed of 400 rpm. The pH was adjusted to 4.6 with 1 mol / L acetic acid, and the reaction time was 6 hours.

[0141] ③ Purification and drying: After the reaction is complete, cool to 25℃ and add anhydrous ethanol to precipitate the product. Let stand for 0.5 hours, centrifuge for 10 minutes at 8000 rpm, and discard the supernatant. Wash the precipitate three times with 70% ethanol to remove residual benzaldehyde. Vacuum dry for 24 hours at 40℃ to obtain a white powdery protective product.

[0142] ④ Glyoxal crosslinking: Dissolve the protected product in deionized water and sonicate for 0.5 hours at 40 kHz. Incubate in a 50°C water bath, adjust the pH to 5.4 with phosphate buffer, add glyoxal, and stir for 4 hours at 400 rpm. Terminate the reaction with anhydrous ethanol, centrifuge for 10 minutes at 8000 rpm, and collect the precipitate. Wash three times with an ethanol-water (7:3, v / v) mixture to remove unreacted glyoxal.

[0143] ⑤ Hydrolysis with dilute hydrochloric acid: The cross-linking product was dispersed in 0.1 mol / L HCl solution and stirred in a water bath at 40°C for 2 hours at 300 rpm. The pH was adjusted to 7.2 with 1 mol / L NaOH. The mixture was placed in a dialysis bag with a molecular weight cutoff of 3500 Da and dialyzed with flowing deionized water for 48 hours, changing the water every 6 hours to remove benzaldehyde and small molecule impurities. The mixture was then freeze-dried at -50°C for 48 hours to obtain a white porous solid product.

[0144] (2) Preparation of multifunctional antiscalant for reverse osmosis membranes (CS-004):

[0145] ① Solvent premixing and main agent dissolution: Mix 63.695 parts of deionized water, 4.5 parts of acetic acid, and 0.3 parts of urea, and slowly add 7.5 parts of CS-GLU while stirring at 40°C, and dissolve for 2 hours.

[0146] ② Functional components are added in steps: Add 2 parts ascorbic acid and 2.5 parts triammonium citrate in sequence, and adjust the pH to 5.5 with sodium hydroxide. Add 4 parts polyaspartic acid and 1.5 parts sodium gluconate, and stir for 45 minutes.

[0147] ③ Integration of nanomaterials and wetting agents: 0.005 parts of nano-SiO2 were ultrasonically dispersed in 10 parts of deionized water for 45 min at a frequency of 40 kHz, and then added to the system. Subsequently, 3 parts of polyethylene glycol were added and stirred for 1 hour.

[0148] ④ Stabilization treatment: Add 1 part EDTA-2Na to inhibit oxidation, filter with a 0.8μm filter membrane to remove undissolved impurities, fill in the package away from light, and store at 4℃.

[0149] A factory's wastewater reuse system employs a pretreatment plus dual-membrane process. The reverse osmosis membrane uses Hydranautics PROC30 membrane elements. The reverse osmosis feed water conductivity is 1500-1700 μS / cm, the initial product water conductivity is approximately 16 μS / cm, and the product water flow rate is 140 m³ / cm. 3 The system operates at a flow rate of 0.8 MPa per hour, with an inlet pressure of 0.8 MPa and a system differential pressure of 0.15 MPa. After three years of operation, the conductivity of the produced water has increased to approximately 70 μS / cm, and the production capacity is 130 m³ / h. 3 / h, system pressure difference 0.13MPa.

[0150] The above-mentioned reverse osmosis system for wastewater reuse, after being cleaned with citric acid, sodium hydroxide, and sodium dodecyl sulfonate, had its membrane system operating parameters recorded: inlet water pressure (MPa), system differential pressure (MPa), desalination rate (%), and standardized permeate flow rate (m³). 3 / h), etc. CS-004 is prepared using reverse osmosis permeate, with a concentration controlled at 0.8 kg / 1000 L. After complete dissolution via a circulation pump, it undergoes gradient pressure circulation treatment: First stage, full-flow circulation for 10 minutes, circulation flow rate 340 m³ / h. 3 / h (The design value of the low-pressure flushing flow rate of this reclaimed water system is 300m³ / h) 3 / h); In the second stage, the influent pressure is gradually increased to 0.95MPa, the concentrate to product water flow ratio is controlled at 2, and the system is continuously circulated for 30 minutes. The system then enters normal operation mode with an influent flow rate of 200m³ / h. 3 Based on a per-hour rate, CS-004 was continuously added at a concentration of 4 mg / L, and the operating parameters of the membrane system were recorded.

[0151] Using the aforementioned multifunctional scale inhibitor CS-004 for online scale repair, the standardized permeate flow rate of the reverse osmosis system was restored to 140 m³ / h after the repair. 3 / h. The operational performance of this reverse osmosis system for wastewater reuse is shown in the following... Figure 3 .

[0152] from Figure 3 As can be seen, the desalination rate of the reverse osmosis system rapidly increased from 95.6% before repair to 98.8%, with the inlet water pressure simultaneously rising to 0.99 MPa. After repair, the system operated stably for approximately 70 days, maintaining a desalination rate of 98.0%-98.5% and an inlet water pressure fluctuating between 0.93-0.96 MPa. However, with prolonged operation, the desalination rate gradually decreased to 95.7%, accompanied by a drop in pressure to 0.84 MPa. In summary, CS-004 can achieve efficient short-term, periodic repairs, but its long-term stability is limited by the complexity of contaminants. Regular chemical cleaning, optimized pretreatment processes (such as enhanced organic matter removal), and dynamic adjustments to the scale inhibitor dosage strategy can be combined to extend the repair cycle and improve system sustainability.

Claims

1. A multifunctional scale inhibitor and dispersant for use in reverse osmosis systems, characterized in that, Its components, by mass parts, are as follows: CS-GLU: 6-9 parts, ascorbic acid: 1.5-2.5 parts, polyaspartic acid: 3-4.5 parts, sodium gluconate: 1-2 parts, polyethylene glycol: 2-4 parts, nano-SiO2: 0.005-0.03 parts, triammonium citrate: 1-3.5 parts, acetic acid: 3-6 parts, urea: 0.2-0.5 parts, EDTA-2Na: 1-2.5 parts, deionized water: 65.47-81.295 parts; The CS-GLU is a cross-linked product made from chitosan and L-glutamic acid. The preparation method of the CS-GLU is as follows: Step 1) Raw material pretreatment: Dissolve chitosan in acetic acid solution and stir magnetically until completely dissolved. Filter with a filter membrane to remove undissolved impurities. Dissolve L-glutamic acid in deionized water and stir until completely dissolved. Mix the chitosan solution and L-glutamic acid solution at a volume ratio of 1:1 and mix evenly by magnetic stirring. Step 2) Benzaldehyde protection reaction: Slowly add benzaldehyde dropwise to the mixed solution obtained in step 1), at a rate of 0.5 to 2 mL / min, under nitrogen protection, in a constant temperature water bath at 55 to 65°C with continuous stirring, and then adjust the pH to 4.4 to 4.

6. Step 3) Purification and drying: After the reaction is complete, cool to 20-25°C, add anhydrous ethanol to precipitate the product, let stand, centrifuge, and discard the supernatant; wash the precipitate with ethanol to remove residual benzaldehyde; vacuum dry to obtain a white powdery protective product; Step 4) Glyoxal crosslinking: Dissolve the protected product in deionized water and disperse it by ultrasonication; bathe in a 45-50°C water bath, then adjust the pH to 5.4-5.6, add glyoxal, and stir; then add anhydrous ethanol to terminate the reaction, centrifuge, and collect the precipitate; Wash with an ethanol-water mixture to remove unreacted glyoxal; Step 5) Hydrolysis with dilute hydrochloric acid: Disperse the crosslinking product from step 4) in dilute HCl solution and stir in a water bath at 35-45°C; then adjust the pH to 6.8-7.2; put it into a dialysis bag and dialyze with flowing deionized water to remove benzaldehyde and small molecule impurities; then freeze dry at -50 to -35°C to obtain a white porous solid product, which is CS-GLU.

2. The multifunctional scale inhibitor and dispersant for reverse osmosis systems according to claim 1, characterized in that, It is prepared by mixing and dissolving the following components in parts by mass: CS-GLU: 8 parts, ascorbic acid: 2 parts, triammonium citrate: 1.5 parts, polyaspartic acid: 3.5 parts, sodium gluconate: 2 parts, nano SiO2: 0.01 parts, polyethylene glycol: 3 parts, acetic acid: 5 parts, urea: 0.4 parts, EDTA-2Na: 1.5 parts, and deionized water: 73.09 parts.

3. The multifunctional scale inhibitor and dispersant for reverse osmosis systems according to claim 1, characterized in that, In step 2), the pH is adjusted to 4.4-4.6 with 1-2 mol / L NaOH or 0.5-1 mol / L acetic acid, and the reaction time is 5-7 hours.

4. The multifunctional scale inhibitor and dispersant for reverse osmosis systems according to claim 1, characterized in that, In step 4), the pH is adjusted to 5.4–5.6 using phosphate buffer.

5. A multifunctional scale inhibitor and dispersant for use in reverse osmosis systems according to claim 1, characterized in that, In step 5), the pH is adjusted to 6.8-7.2 using 1-3 mol / L NaOH.

6. A method for preparing a multifunctional scale inhibitor and dispersant for use in reverse osmosis systems as described in any one of claims 1-5, characterized in that, Specifically, it includes: S1) Solvent premixing and main agent dissolution: Mix deionized water, acetic acid and urea, and slowly add CS-GLU while stirring at 35-45℃ to dissolve; S2) Functional components are added in steps: ascorbic acid and triammonium citrate are added in sequence, and the pH is adjusted to 5.5-6.0; then polyaspartic acid and sodium gluconate are added and mixed. S3) Integration of nanomaterials and wetting agents: Nano-SiO2 is ultrasonically dispersed and added to the system obtained in step 2), followed by the addition of polyethylene glycol and mixing. S4) Stabilization treatment: Add EDTA-2Na to inhibit oxidation, filter with a filter membrane to remove undissolved impurities, and fill in the dark.

7. The method for preparing a multifunctional scale inhibitor and dispersant for use in a reverse osmosis system according to claim 6, characterized in that, The ultrasonic frequency in S3 is 40–50 kHz.

8. A method of using a multifunctional scale inhibitor and dispersant for reverse osmosis systems as described in any one of claims 1-7, characterized in that, Specifically, it includes: 1) Use reverse osmosis permeate to prepare the repair solution, and control the concentration at 0.5-1.0 kg / 1000 L; the daily scale inhibitor dosage is: based on the influent flow rate, add continuously at 2-6 mg / L; 2) Perform gradient pressure circulation treatment: The first stage is high-velocity flushing, with full-flow circulation for 5 to 15 minutes, and the circulation flow rate is not less than 110% of the design value; The second stage involves enhancing infiltration, increasing the influent pressure to 1.1 to 1.5 times the operating pressure, controlling the concentrate to permeate flow rate ratio to be less than 3, and continuously circulating the treatment for 20 to 40 minutes.

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