Silicon scale cleaning agent and method of using the same

Abstract

The application relates to a silicon scale cleaning agent and a use method of the silicon scale cleaning agent. The silicon scale cleaning agent comprises, in percentage by mass, an acid solution, an inorganic salt component and water; the acid solution accounts for 0.50-2.75 percent, the inorganic salt component accounts for 0.10-0.50 percent, and the rest is water; wherein the inorganic salt component comprises a first inorganic salt and a second inorganic salt; the first inorganic salt comprises a fluorine salt; and the second inorganic salt is selected from one or more of a chlorine salt, a bromine salt, an iodine salt and a sulfate salt. According to the silicon scale cleaning agent, the first inorganic salt serves as a main active component for silicon scale cleaning, can specifically coordinate with the silicon scale, realizes efficient removal of the silicon scale, and the second inorganic salt adjusts the concentration of fluorine ions in the solution by affecting the dissolution balance of the first inorganic salt, significantly slows down the dissolution rate of the fluorine salt, and avoids the instantaneous generation and diffusion of harmful HF gas due to the too fast dissolution rate.

Description

Technical Field

[0001] This invention relates to the field of membrane system cleaning technology, specifically to a silica scale cleaning agent and a method for using the silica scale cleaning agent. Background Technology

[0002] In water treatment systems, especially in the operation of reverse osmosis (RO) membrane systems, nanofiltration (NF) membrane systems, and industrial circulating water systems, existing technologies generally focus on preventing and controlling metal ion scaling such as calcium scale, magnesium scale, and iron scale, while the hazards of silica scale have long been overlooked.

[0003] Natural water bodies and industrial wastewater (such as coal chemical wastewater) typically contain high concentrations of silicon, primarily in the form of monomeric silicic acid. Silica scale exists in various forms, including colloidal silica and metal silicates. During membrane system operation, as silica accumulates continuously at the concentrate end of the membrane module, monomeric silica readily undergoes a condensation reaction to form colloidal silica. If metal ions such as iron and aluminum are also present in the water, dense metal silicate deposits with extremely low solubility will further form. Once silica scale deposits, it can easily lead to a sharp drop in the desalination rate of the membrane module and a drastic reduction in permeate flow. In severe cases, it can also cause a surge in differential pressure, detachment of the concentrate grid, and even irreversible physical scratches on the membrane, significantly shortening its service life. Summary of the Invention

[0004] Fluoride salts are used as the active ingredient in silica descaling agents. This typically involves the reaction of fluoride ions with silica or silicates under acidic conditions to form soluble hexafluorosilicic acid. Fluoride salts, or their salts, dissolve silica scale. However, fluoride salts dissolve rapidly in acidic aqueous solutions, instantly releasing high concentrations of fluoride ions. These fluoride ions quickly combine with hydrogen ions in the solution to generate large amounts of volatile HF gas, which is highly toxic and corrosive. If it cannot be dissolved in water in a timely and complete manner, it can easily escape into the working environment, posing serious operational safety hazards and environmental risks, and may corrode equipment.

[0005] To address the aforementioned issues, it is necessary to provide a silica scale cleaning agent that can efficiently remove silica scale while effectively controlling the generation of toxic and harmful gases such as HF, as well as a method for preparing the silica scale cleaning agent.

[0006] A first aspect of the present invention provides a silica scale cleaning agent, comprising, by mass percentage: an acidic solution comprising 0.50% to 2.75%, an inorganic salt component comprising 0.10% to 0.50%, and the balance being water; or, an acidic solution comprising 0.63% to 2.38%, an inorganic salt component comprising 0.11% to 0.45%, and the balance being water; or, an acidic solution comprising 0.75% to 2.13%, an inorganic salt component comprising 0.13% to 0.30%, and the balance being water; or, an acidic solution comprising 1.00% to 2.00%, an inorganic salt component comprising 0.15% to 0.25%, and the balance being water; wherein the inorganic salt component comprises a first inorganic salt and a second inorganic salt, the first inorganic salt comprising a fluoride salt, and the second inorganic salt selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

[0007] In one embodiment, the fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

[0008] In one embodiment, the bromide salt is selected from one or more of sodium bromide, ammonium bromide, and potassium bromide.

[0009] In one embodiment, the iodized salt is selected from one or more of sodium iodide, ammonium iodide, and potassium iodide.

[0010] In one embodiment, the sulfate is selected from one or more of sodium sulfate, ammonium sulfate, and potassium sulfate.

[0011] In one embodiment, the mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:1, or 8:1 to 2:1, or 6:1 to 3:1, or 5:1 to 3:1.

[0012] In one embodiment, the acidic solution includes an acidic substance and a solvent, wherein the acidic substance includes an organic acid and an inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:1, or 2:1 to 6.5:1, or 2.5:1 to 5.5:1, or 3:1 to 5:1.

[0013] In one embodiment, the solvent is water, and the mass ratio of the sum of the organic acid and the inorganic acid to water is 0.3:1 to 1:1, or 0.35:1 to 0.9:1, or 0.4:1 to 0.7:1, or 0.4:1 to 0.6:1.

[0014] In one embodiment, the organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

[0015] In one embodiment, the water-soluble carboxylic acid includes oxalic acid and / or citric acid.

[0016] According to the silica scale cleaning agent of the present invention, the first inorganic salt, as the main active ingredient for silica scale cleaning, can undergo a specific coordination reaction with silica scale to achieve efficient removal of silica scale. The second inorganic salt, by affecting the dissolution balance of the first inorganic salt, adjusts the concentration of fluoride ions in the solution, significantly slows down the dissolution rate of fluoride salt, and avoids the instantaneous generation and release of harmful HF gas due to excessively fast dissolution rate.

[0017] A second aspect of the present invention provides a method for using a silica scale cleaning agent, comprising the following steps: mixing a first inorganic salt and a second inorganic salt to obtain an inorganic salt component, and dividing the inorganic salt component into inorganic salt component A and inorganic salt component B according to a first mass ratio; providing an acidic solution and water, and sequentially adding the acidic solution and inorganic salt component A to the water to obtain a silica scale intermediate cleaning agent; using the silica scale intermediate cleaning agent to clean the silica scale, and adding inorganic salt component B to the silica scale intermediate cleaning agent; wherein, the first inorganic salt includes a fluoride salt, and the second inorganic salt is selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

[0018] As one embodiment, the step of sequentially adding the acidic solution and inorganic salt component A to the water to prepare the intermediate cleaning agent for silica scale includes: adding the acidic solution to the water and mixing to obtain a diluted acidic solution; and adding the inorganic salt component A to the diluted acidic solution to prepare the intermediate cleaning agent for silica scale.

[0019] In one implementation, the first mass ratio ranges from 1:9 to 7:3, or 2:3 to 7:3, or 2:3 to 1:1.

[0020] As one embodiment, adding inorganic salt component B to the intermediate cleaning agent for silica scale includes: dividing the inorganic salt component B into n parts according to a second mass ratio, where n is a positive integer greater than or equal to 2; and adding the n parts of the inorganic salt component B to the intermediate cleaning agent for silica scale respectively.

[0021] In one implementation, n=3, and the second mass ratio is (1~3):(1~3):(1~3); the step of adding n parts of the inorganic salt component B to the intermediate cleaning agent for silica scale includes: adding 3 parts of the inorganic salt component B to the intermediate cleaning agent for silica scale in sequence according to the second mass ratio.

[0022] In one embodiment, by mass percentage, the acidic solution comprises 0.50% to 2.75%, the inorganic salt component comprises 0.10% to 0.50%, and the balance is water; or, the acidic solution comprises 0.63% to 2.38%, the inorganic salt component comprises 0.11% to 0.45%, and the balance is water; or, the acidic solution comprises 0.75% to 2.13%, the inorganic salt component comprises 0.13% to 0.30%, and the balance is water; or, the acidic solution comprises 1.00% to 2.00%, the inorganic salt component comprises 0.15% to 0.25%, and the balance is water.

[0023] In one embodiment, the fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

[0024] In one embodiment, the bromide salt is selected from one or more of sodium bromide, ammonium bromide, and potassium bromide.

[0025] In one embodiment, the iodized salt is selected from one or more of sodium iodide, ammonium iodide, and potassium iodide.

[0026] In one embodiment, the sulfate is selected from one or more of sodium sulfate, ammonium sulfate, and potassium sulfate.

[0027] In one embodiment, the mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:1, or 8:1 to 2:1, or 6:1 to 3:1, or 5:1 to 3:1.

[0028] In one embodiment, the acidic solution includes an acidic substance and a solvent, wherein the acidic substance includes an organic acid and an inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:1, or 2:1 to 6.5:1, or 2.5:1 to 5.5:1, or 3:1 to 5:1.

[0029] In one embodiment, the solvent is water, and the mass ratio of the sum of the organic acid and the inorganic acid to water is 0.3:1 to 1:1, or 0.35:1 to 0.9:1, or 0.4:1 to 0.7:1, or 0.4:1 to 0.6:1.

[0030] In one embodiment, the organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

[0031] In one embodiment, the water-soluble carboxylic acid includes oxalic acid and / or citric acid.

[0032] The method of using the silica scale cleaning agent of the present invention involves first dissolving an acidic solution in water, and then adding inorganic salt components in batches in a specific sequence. This allows the system to first form a uniform and stable acidic environment. Subsequently, inorganic salt components A and B dissolve stepwise in this controlled environment, which buffers the initial intensity of the reaction between fluoride salts and acid, suppresses the instantaneous concentration of HF, and makes the release of fluoride ions and subsequent reaction with silica scale more stable and controllable. At the same time, by influencing the dissolution balance of the first inorganic salt through the second inorganic salt, the concentration of fluoride ions in the solution is adjusted, further slowing down the dissolution rate of fluoride salts. Thus, while extending the effective action time and increasing the cleaning depth, the generation of harmful byproducts is suppressed to the greatest extent. The preparation method of the silica scale cleaning agent of the present invention is simple in steps, has mild process conditions, and is easy to implement on a large scale. Attached Figure Description

[0033] Figure 1 This is the scanning electron microscope (SEM) spectrum of the membrane before cleaning.

[0034] Figure 2 The image shows the scanning electron microscope (SEM) spectrum of the membrane after cleaning in Experiment Example 4.

[0035] Figure 3 The image shows the electron microscopy scanning energy spectrum of the membrane after cleaning, as shown in Comparative Example 1. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The invention will now be described in detail with reference to the embodiments.

[0037] As described in the background section, existing silica scale cleaning agents use fluorinated salts as the active ingredient, which poses operational safety hazards and environmental risks, and may corrode equipment. To address the aforementioned technical problems, one aspect of the present invention provides a silica scale cleaning agent, comprising, by mass percentage: an acidic solution comprising 0.50% to 2.75%, an inorganic salt component comprising 0.10% to 0.50%, and the balance being water; or, an acidic solution comprising 0.63% to 2.38%, an inorganic salt component comprising 0.11% to 0.45%, and the balance being water; or, an acidic solution comprising 0.75% to 2.13%, an inorganic salt component comprising 0.13% to 0.30%, and the balance being water; or, an acidic solution comprising 1.00% to 2.00%, an inorganic salt component comprising 0.15% to 0.25%, and the balance being water; wherein the inorganic salt component comprises a first inorganic salt and a second inorganic salt, the first inorganic salt comprising a fluoride salt, and the second inorganic salt selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

[0038] In one embodiment, the bromide salt is selected from one or more of sodium bromide, ammonium bromide, and potassium bromide.

[0039] In one embodiment, the iodized salt is selected from one or more of sodium iodide, ammonium iodide, and potassium iodide.

[0040] In one embodiment, the sulfate is selected from one or more of sodium sulfate, ammonium sulfate, and potassium sulfate.

[0041] According to the silica scale cleaning agent of the present invention, the acidic solution can effectively soften silica scale and wash away metal ions (such as calcium, magnesium, iron, etc.) in the surface structure, thereby exposing the core structure of the silica scale and providing a suitable acidic environment for the reaction of fluoride ions with the silica scale. The inorganic salt component not only reacts directly with the exposed core structure of the silica scale, promoting its dissolution, but also ensures the stable dissolution of fluoride salts through the rational control of the first and second inorganic salts, avoiding the instantaneous large-scale generation and release of harmful HF gas due to excessively rapid dissolution. This reduces safety hazards and environmental risks during operation and decreases the possibility of equipment corrosion. Specifically, the first inorganic salt, as the main active ingredient in silica scale cleaning, can undergo a specific coordination reaction with the silica scale, achieving efficient removal. The second inorganic salt, by affecting the dissolution balance of the first inorganic salt, regulates the concentration of fluoride ions in the solution, significantly slowing down the dissolution rate of fluoride salts, thereby reducing the instantaneous generation and volatilization of HF, greatly improving the environmental and operational safety of the cleaning process, and extending the effective cleaning time.

[0042] As one implementation method, the water can be deionized water, soft water, etc., and no specific limitation is made here.

[0043] In one embodiment, the fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

[0044] Sodium fluoride, ammonium fluoride, and potassium fluoride, as soluble fluoride salts, provide a stable and essential source of fluoride ions for the system, forming the active material basis for ensuring the silica scale removal reaction can proceed. The selected chloride salts (sodium chloride, ammonium chloride, or potassium chloride), as the second inorganic salt, are not only widely available and inexpensive, but also provide the same cations as the first inorganic salt. A significant common ion effect is generated in the system. This effect can effectively inhibit the shift of the dissolution equilibrium of the first inorganic salt towards rapid dissolution, thereby stabilizing and slowing down the release rate of fluoride ions, significantly reducing the instantaneous concentration of HF and the potential risk of escape, and extending the effective action period of the cleaning agent while ensuring operational safety.

[0045] In one embodiment, the mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:1, or 8:1 to 2:1, or 6:1 to 3:1, or 5:1 to 3:1.

[0046] By controlling the mass ratio of the first inorganic salt to the second inorganic salt at 10:1 to 2:1, or even further at 8:1 to 2:1, 6:1 to 3:1, or 5:1 to 3:1, it is possible to maintain an effective fluoride ion concentration while utilizing the common ion effect generated by the same cation contained in the second inorganic salt to suppress the dissolution equilibrium of the first inorganic salt, thereby significantly slowing down the release rate of fluoride ions. This not only avoids violent reactions and the large-scale generation of HF gas caused by excessively high instantaneous fluoride ion concentrations, but also allows fluoride ions to react with silica scale in a stable and controllable manner, effectively extending the effective reaction time of the cleaning agent and achieving safe control and improved efficiency in the cleaning process.

[0047] In one embodiment, the acidic solution includes an acidic substance and a solvent, wherein the acidic substance includes an organic acid and an inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:1, or 2:1 to 6.5:1, or 2.5:1 to 5.5:1, or 3:1 to 5:1.

[0048] Organic acids effectively dissolve and remove metal cations from silica scale through complexation. This weakens the structural stability of metal silicates, achieving initial softening of the silica scale structure. Inorganic acids further promote scale dissociation through strong protonation, providing the necessary acidic environment for the subsequent specific fluorination reaction between fluoride ions and silica or silicate framework, generating soluble fluorosilicic acid (salts). Specifically, strong protonation refers to the ionization of inorganic acids in water to produce a high concentration of hydrogen ions. These It can actively and strongly attack the metal-oxygen bond (MO) in silicate, and at the same time regulate the system to an acidic environment to ensure the stability of fluoride ions, so that they can smoothly undergo a specific coordination reaction with silicon-oxygen bond (Si-O), causing these chemical bonds to break and weaken, thereby destroying the dense structure of silica scale as a whole, making it loose and easy to fall off.

[0049] The synergistic effect of organic and inorganic acids in the above ratio significantly improves the efficiency of silica scale removal. At the same time, through the corrosion inhibition effect of organic acids and the reasonable adjustment of the strength of inorganic acids, the risk of corrosion of equipment materials (especially membrane materials) by the cleaning agent is effectively reduced, thus achieving a balance between efficient cleaning and material protection.

[0050] In one implementation, the acidic substance may also include only organic acids.

[0051] In one embodiment, the solvent is water, and the mass ratio of the sum of the organic acid and the inorganic acid to water is 0.3:1 to 1:1, or 0.35:1 to 0.9:1, or 0.4:1 to 0.7:1, or 0.4:1 to 0.6:1.

[0052] Water is used as a solvent to fully dissolve and uniformly disperse organic and inorganic acids, forming a stable homogeneous system. The above-mentioned ratio helps ensure the acidic solution maintains chemical stability and component homogeneity during storage and transportation. Simultaneously, by controlling the water content of the acidic solution, the corrosive and volatile risks of organic and inorganic acids are effectively reduced. Furthermore, the acidic solution can be diluted to the required concentration before actual use, balancing storage safety, operational convenience, and final cleaning effectiveness.

[0053] In one embodiment, the organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

[0054] The carboxyl group (-COOH) in water-soluble carboxylic acids can react with metal ions in or on the surface of silica scale. A complexation reaction occurs, forming a stable, water-soluble complex that effectively strips and dissolves the metal ion components on the surface of the silica scale. This not only removes the metal coating that hinders the reaction, exposing the internal silica or silicate core structure, but also significantly weakens the overall stability of the silica scale by removing metal cations from the structure, achieving initial softening. Hydrochloric acid provides a strongly protonated environment, further promoting the decomposition of the silicate framework and synergistically maintaining the acidic conditions required by the system with the organic acid. Under these conditions, the fluoride ions released by the subsequently added fluoride salt react efficiently with the exposed silica scale to generate soluble fluorosilicone compounds, thus achieving a synergistic cleaning mechanism of organic acid softening and stripping, inorganic acid decomposition providing reaction sites, and fluoride ion specific dissolution.

[0055] As one embodiment, the water-soluble carboxylic acid includes oxalic acid and / or citric acid.

[0056] Oxalic acid can efficiently complex polyvalent metal ions such as iron and aluminum in silica scale, thereby effectively disrupting the stable structure of metal silicates and promoting scale dissociation. Citric acid, with its excellent pH buffering properties, helps maintain the stability of the acidity of the reaction system and exhibits a gentler effect on equipment materials. Both can be used alone or in combination to complex and strip metal ions, stabilize the reaction environment, and synergistically create favorable conditions for subsequent fluorination reactions, improving cleaning efficiency while ensuring operational safety and equipment compatibility.

[0057] In one embodiment, the first inorganic salt and the second inorganic salt contain the same cation. For example, the first inorganic salt may be sodium fluoride and the second inorganic salt may be sodium chloride; or, the first inorganic salt may be sodium fluoride and ammonium fluoride and the second inorganic salt may be sodium chloride and ammonium chloride; or, the first inorganic salt may be sodium fluoride, ammonium fluoride and potassium fluoride and the second inorganic salt may be sodium chloride, ammonium chloride and potassium chloride, and so on.

[0058] By ensuring that the first and second inorganic salts share the same cation, the second inorganic salt completely ionizes in solution to generate a high concentration of this common cation. Based on the common ion effect, this inhibits the shift of the first inorganic salt's dissolution equilibrium towards ionization, thereby significantly slowing its dissolution rate. Consequently, fluoride ions are released slowly and controllably, further reducing the instantaneous rate of their reaction with acid to generate HF. This significantly improves the safety and controllability of the cleaning process without affecting the final removal of silica scale.

[0059] A second aspect of the present invention also provides a method for preparing a silica scale cleaning agent, comprising the following steps: mixing a first inorganic salt and a second inorganic salt to obtain an inorganic salt component, and dividing the inorganic salt component into inorganic salt component A and inorganic salt component B according to a first mass ratio; providing an acidic solution and water, and sequentially adding the acidic solution and inorganic salt component A to the water to obtain a silica scale intermediate cleaning agent; using the silica scale intermediate cleaning agent to clean the silica scale, and adding inorganic salt component B to the silica scale intermediate cleaning agent; wherein, the first inorganic salt includes a fluoride salt, and the second inorganic salt is selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

[0060] The preparation method of the silica scale cleaning agent of the present invention involves pre-dry mixing the first inorganic salt and the second inorganic salt to form a homogeneous inorganic salt component. This ensures that the two salts achieve microscopic uniform dispersion in the solid state, effectively avoiding the problem of instantaneous aggregation and dissolution of fluoride salts that may be caused by uneven local feeding during the subsequent dissolution process. This lays a physical foundation for the stable release of fluoride ions from the source. By adopting a specific order of first dissolving the acidic solution in water and then adding the inorganic salt component, the system is ensured to first form a homogeneous and stable acidic environment. Subsequently, the first inorganic salt group and inorganic salt component B are gradually added and dissolved in this controlled environment, effectively buffering the intensity of the initial reaction between fluoride salts and acid, further suppressing the instantaneous peak concentration of HF, and making the release of fluoride ions and the subsequent reaction with silica scale more stable and controllable.

[0061] As one embodiment, the step of sequentially adding the acidic solution and inorganic salt component A to the water to prepare the intermediate cleaning agent for silica scale includes: adding the acidic solution to the water and mixing to obtain a diluted acidic solution; and adding the inorganic salt component A to the diluted acidic solution to prepare the intermediate cleaning agent for silica scale.

[0062] By diluting the acidic solution to obtain an acidic solution diluent, and adding inorganic salt component A to the acidic solution diluent, the concentration of reactants is avoided from a sudden increase due to the addition of all inorganic salt components at once. This results in the release of fluoride ions and the subsequent generation of HF in the system exhibiting segmented and stable kinetic characteristics, suppressing drastic fluctuations in the reaction rate, and providing better reaction conditions for the layer-by-layer and continuous dissolution of deep silica scale.

[0063] In one implementation, the first mass ratio ranges from 1:9 to 7:3, or 2:3 to 7:3, or 2:3 to 1:1.

[0064] By using the first mass ratio, the system quickly reaches and exceeds the initial threshold concentration of fluoride ions required for effective cleaning, thus ensuring the effective initiation of the reaction.

[0065] As one embodiment, adding inorganic salt component B to the intermediate cleaning agent for silica scale includes: dividing the inorganic salt component B into n parts according to a second mass ratio, where n is a positive integer greater than or equal to 2; and adding the n parts of the inorganic salt component B to the intermediate cleaning agent for silica scale respectively.

[0066] By actively controlling the reaction process through a gradient addition scheme, the second inorganic salt is added in steps after inorganic salt component A is added. This further disperses the instantaneous dissolution amount of fluoride salt and the reaction exothermic rate, and further effectively suppresses the instantaneous concentration peak of HF, thereby significantly improving the operational safety and environmental friendliness of the cleaning process.

[0067] In one implementation, n=3, and the second mass ratio is (1~3):(1~3):(1~3); the step of adding n parts of the inorganic salt component B to the intermediate cleaning agent for silica scale includes: adding 3 parts of the inorganic salt component B to the intermediate cleaning agent for silica scale in sequence according to the second mass ratio.

[0068] After the addition of inorganic salt component A, the second inorganic salt is added in steps according to the second mass ratio mentioned above. This not only suppresses the instantaneous concentration of HF and makes the release of fluoride ions more stable, but also makes the subsequent cleaning of silica scale more efficient.

[0069] In one embodiment, by mass percentage, the acidic solution comprises 0.50% to 2.75%, the inorganic salt component comprises 0.10% to 0.50%, and the balance is water; or, the acidic solution comprises 0.63% to 2.38%, the inorganic salt component comprises 0.11% to 0.45%, and the balance is water; or, the acidic solution comprises 0.75% to 2.13%, the inorganic salt component comprises 0.13% to 0.30%, and the balance is water; or, the acidic solution comprises 1.00% to 2.00%, the inorganic salt component comprises 0.15% to 0.25%, and the balance is water.

[0070] In one embodiment, the fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

[0071] In one embodiment, the mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:1, or 8:1 to 2:1, or 6:1 to 3:1, or 5:1 to 3:1.

[0072] In one embodiment, the acidic solution includes an acidic substance and a solvent, wherein the acidic substance includes an organic acid and an inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:1, or 2:1 to 6.5:1, or 2.5:1 to 5.5:1, or 3:1 to 5:1.

[0073] In one embodiment, the solvent is water, and the mass ratio of the sum of the organic acid and the inorganic acid to water is 0.3:1 to 1:1, or 0.35:1 to 0.9:1, or 0.4:1 to 0.7:1, or 0.4:1 to 0.6:1.

[0074] In one embodiment, the organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

[0075] In one embodiment, the water-soluble carboxylic acid includes oxalic acid and / or citric acid.

[0076] In one embodiment, when the acidic solution is added to water and mixed to obtain a diluted acidic solution, the operating temperature is less than or equal to 60°C, or 30°C to 50°C.

[0077] In one embodiment, when the acidic solution is added to water and mixed to obtain a diluted acidic solution, the stirring speed is 30 rpm to 100 rpm or 50 rpm to 80 rpm.

[0078] In one embodiment, when the acidic solution is added to water and mixed to obtain a diluted acidic solution, the stirring time is less than or equal to 30 minutes, or 10 to 20 minutes.

[0079] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0080] It should be noted that, in order to verify and compare the overall performance of the silica scale cleaning agent described in this invention, the following tests were conducted on the embodiments and comparative examples: 1. Cleaning Efficiency Test: Using the silica scale cleaning agents prepared in all examples and comparative examples, reverse osmosis (RO) membrane systems with the same degree of silica scale fouling were cleaned under the same conditions. All cleaning was performed using a flat-sheet membrane testing machine manufactured by Shanghai Tongqin Environmental Protection Technology Co., Ltd., model TQFM40-3F. Following the following reverse osmosis membrane testing procedures (including test steps and cleaning effect judgment), flux tests were conducted on the membranes before and after cleaning, and the cleaning recovery effect was evaluated.

[0081] Reverse osmosis membrane testing procedures

[0082] Test steps: (1) Preparation of basic test water: 10L water + 4g sodium chloride + 1g anhydrous magnesium sulfate, conductivity: 1000+μS / cm, pH: 7.0~7.4; (2) Membrane performance test before cleaning: The sample membrane is cut into a circular membrane with a diameter of 7cm. After clamping with the test equipment, it is pre-circulated with basic test water at 25℃ for half an hour. Then the timing is started and the product water is collected from the product water outlet. The test ends after 1 hour. The conductivity and volume of the product water are measured to calculate the water flux. (3) Membrane performance test after cleaning: The cleaned membrane was pre-circulated with basic test water at 25°C for half an hour, then the timing was started and the product water was collected from the product water outlet. The test ended after 1 hour, and the conductivity and volume of the product water were measured to calculate the water flux.

[0083] Judging the cleaning effect: By comparing the flux before and after cleaning, the flux recovery rate was calculated to compare the cleaning effect of the silica scale cleaning agent. The formulas for calculating flux and flux recovery rate are as follows:

[0084] 2. Safety Testing: For Example 4 and Comparative Example 2, the concentration of HF gas was detected using a dedicated toxic and hazardous gas detector. The manufacturer of the detector was Shenzhen Honeywell Technology Co., Ltd., model HNAG900-HF-T. The detection method was as follows: the detector was placed at the operator's breathing belt height, and continuous real-time monitoring was performed throughout the cleaning process. The instantaneous peak concentration and the time-varying arithmetic mean concentration of HF gas were recorded. The instantaneous peak concentration was the maximum value among all gas content data. The arithmetic mean concentration was obtained by extracting air every 15 seconds and obtaining concentration data, adding all data together and dividing by the total number of extractions (960) to obtain the arithmetic mean concentration.

[0085] Example 1 The preparation method of the silica scale cleaning agent in this embodiment includes the following steps: (1) Preparation of acidic solution: Weigh 71.1g of oxalic acid and 8.9g of hydrochloric acid, add them to 80.0g of deionized water at 60℃, and dissolve them at a stirring speed of 30rpm for 30 minutes to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 3.0g of sodium fluoride and 1.0g of sodium chloride, stir and mix them, and the resulting solid mixture is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 110.0g of acidic solution, stir and mix, then add 1.6g of inorganic salt component, stir until dissolved, and obtain silica scale intermediate cleaning agent; The silica-contaminated membrane was cleaned using this intermediate cleaning agent in a flat-sheet membrane testing machine. The cleaning procedure was as follows: after every 1 hour of operation, 0.8 g of inorganic salt component was added to the system and stirred to dissolve. The total cleaning time was 4 hours. The cleaning results are detailed in Table 1.

[0086] Example 2 The preparation method of the silica scale cleaning agent in this embodiment includes the following steps: (1) Preparation of acidic solution: Weigh 60.0g citric acid and 20.0g hydrochloric acid, add them to 80.0g deionized water at 40℃, and dissolve them at a stirring speed of 100rpm for 30 minutes to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 18.1g of sodium fluoride and 1.9g of sodium chloride, stir and mix them, and the resulting solid mixture is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 20.0g of the above acidic solution, stir and mix, then add 8.0g of inorganic salt component, stir until dissolved, and obtain silica scale intermediate cleaning agent; The silica scale intermediate cleaning agent was used in a flat-sheet membrane testing machine to circulate and clean silica scale-contaminated membranes. The cleaning procedure was as follows: after every 1 hour of operation, 4.0 g of inorganic salt component was added to the system and stirred to dissolve. The total cleaning time was 4 hours. The cleaning results are detailed in Table 1.

[0087] Example 3 The preparation method of the silica scale cleaning agent in this embodiment includes the following steps: (1) Preparation of acidic solution: Weigh 18.0g citric acid and 6.0g hydrochloric acid, add them to 80.0g deionized water at 50℃, and dissolve them for 10 minutes at a stirring speed of 80rpm to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 5.3g of ammonium fluoride and 0.7g of ammonium chloride, stir and mix them, and the resulting solid mixture is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 40.0g of the above acidic solution, stir and mix, then add 2.4g of inorganic salt component, stir until dissolved, and obtain silica scale intermediate cleaning agent; The silica scale intermediate cleaning agent was used in a flat-sheet membrane testing machine to circulate and clean silica scale-contaminated membranes. The cleaning procedure was as follows: after every 1 hour of operation, 1.2 g of inorganic salt component was added to the system and stirred to dissolve. The total cleaning time was 4 hours. The cleaning results are detailed in Table 1.

[0088] Example 4 The preparation method of the silica scale cleaning agent in this embodiment includes the following steps: (1) Preparation of acidic solution: Weigh 33.3g citric acid and 6.7g hydrochloric acid, add them to 80.0g deionized water at 30℃, and dissolve them at a stirring speed of 60rpm for 20 minutes to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 8.0g of sodium fluoride and 2.0g of sodium chloride, stir and mix them, and the resulting solid mixture is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 80.0g of the above acidic solution, stir and mix, then add 4.0g of inorganic salt component, stir until dissolved, and obtain silica scale intermediate cleaning agent; The silica-contaminated membrane was cleaned using this intermediate cleaning agent in a flat-sheet membrane testing machine. The cleaning procedure was as follows: after every 1 hour of operation, 2.0 g of inorganic salt component was added to the system and stirred to dissolve. The total cleaning time was 4 hours. The cleaning results are detailed in Table 1.

[0089] Example 5 The preparation method of the silica scale cleaning agent in this embodiment includes the following steps: (1) Preparation of acidic solution: Weigh 40.0g oxalic acid and 8.0g hydrochloric acid, add them to 80.0g deionized water at 50℃, and dissolve them for 20 minutes at a stirring speed of 50rpm to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 8.0g of sodium fluoride and 2.0g of sodium chloride, stir and mix them, and the resulting solid mixture is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 70.0g of the above acidic solution, stir and mix, then add 4g of inorganic salt component, stir until dissolved, and obtain silica scale intermediate cleaning agent; The silica-contaminated membrane was cleaned using this intermediate cleaning agent in a flat-sheet membrane testing machine. The cleaning procedure was as follows: after every 1 hour of operation, 2.0 g of inorganic salt component was added to the system and stirred to dissolve. The total cleaning time was 4 hours. The cleaning results are detailed in Table 1.

[0090] Comparative Example 1 The contaminated membrane with silica scale was cleaned by circulating a 0.5% hydrochloric acid solution for 4 hours in a flat-sheet membrane testing machine. The cleaning results are detailed in Table 1.

[0091] Comparative Example 2 The preparation method of the silica scale cleaning agent in this comparative example includes the following steps: (1) Preparation of acidic solution: Weigh 33.3g of oxalic acid and 6.7g of hydrochloric acid, add them to 80.0g of deionized water at 30℃, and dissolve them at a stirring speed of 60rpm for 20 minutes to obtain an acidic solution; (2) Preparation of inorganic salt components: Weigh 8.0g of sodium fluoride, stir and mix evenly, and the resulting solid substance is the inorganic salt component; (3) Preparation of silica scale cleaning agent: Measure 4.0L of pure water, add 80.0g of the above acidic solution, stir and mix, then add 8g of inorganic salt component, stir until dissolved, and obtain silica scale cleaning agent; The silica scale cleaner was used to circulate and clean the silica scale-contaminated membranes for 4 hours in a flat sheet membrane testing machine. The cleaning results are detailed in Table 1.

[0092] According to the reverse osmosis membrane testing procedure, the flux of the membrane before and after cleaning for each embodiment and comparative example was obtained. The flux recovery rate of the membrane after cleaning was calculated and is shown in Table 1.

[0093] Based on the test data shown in Table 1, it can be seen that, compared with conventional acidic cleaning agents (Comparative Example 1), the silica scale cleaning agent provided by the present invention has better performance in flux recovery rate, especially the silica scale cleaning agent prepared in Example 4.

[0094] Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were performed on the reverse osmosis membranes before cleaning, after cleaning in Example 4, and after cleaning in Comparative Example 1 to further verify the cleaning effect from the perspective of microstructure and elemental composition. The results are as follows: Figure 1 - As shown in Table 3 and Table 2, the manufacturer of the scanning electron microscope is Hitachi, and the model is SU8010.

[0095] Table 2. Quantitative analysis results of electron microscopy before membrane cleaning, after membrane cleaning in Example 4, and after membrane cleaning in Comparative Example 1.

[0096] Depend on Figure 1 As shown in Table 2, the elemental analysis data indicates that before cleaning, the sum of the mass percentages of silicon (Si) and oxygen (O) on the membrane surface accounted for 75.24% of the total weight, indicating the presence of a large amount of silica scale on the membrane surface. After cleaning in Example 4, the... Figure 2 As can be seen from the data in Table 2, no silicon (Si) element signal can be detected on the surface of the membrane, and the oxygen (O) element content has dropped to below 15%, indicating that the silicon scale has been effectively removed.

[0097] In contrast. Figure 3 The corresponding data in Table 2 show that the combined content of silicon (Si) and oxygen (O) on the membrane surface after treatment with conventional acidic cleaning agent (Comparative Example 1) is still as high as 70%, indicating that it failed to effectively remove silicon scale.

[0098] The above microscopic elemental analysis results and the summary table of macroscopic membrane cleaning effects (Table 1) corroborate each other, jointly demonstrating that the silica scale cleaning agent provided in Example 4 has a significant cleaning effect on silica scale.

[0099] Based on the environmental air monitoring conducted during the preparation and cleaning processes of Example 4 and Comparative Example 2, the concentration of HF gas was continuously and in real time detected using a toxic and harmful gas detector. The detection results are shown in Table 3.

[0100] As shown in Table 3, the cleaning agent prepared using the common ion effect competition effect and stepwise slow-release technology described in this invention (Example 4) significantly reduces the concentration of HF gas released throughout the entire operation. Specifically, the arithmetic mean concentration of HF gas is 0.3 mg / m³, and the instantaneous peak concentration does not exceed 0.6 mg / m³. This value is far below the maximum permissible concentration limit of HF (2 mg / m³) specified in the national mandatory standard "Occupational Exposure Limits for Hazardous Factors in the Workplace" (GBZ 2.1-2019).

[0101] In contrast, the cleaning agent that did not employ the aforementioned competing ions and sustained-release design (Comparative Example 2) had an arithmetic mean concentration of HF gas of 1.0 mg / m³ and an instantaneous peak concentration of 2.3 mg / m³ during operation, exceeding the safety limits of the aforementioned national standards.

[0102] The comparative data fully demonstrates that, through specific formulation and process design, this invention can effectively suppress the generation and emission of toxic and harmful gases, ensuring that the environmental emission indicators of the cleaning process not only meet but are significantly better than the mandatory requirements of national occupational health and safety standards, reflecting its excellent safety and environmental protection in the application process.

Claims

1. A silica scale cleaning agent, characterized in that, By weight percentage, including: The acidic solution comprises 0.50% to 2.75%, the inorganic salt component comprises 0.10% to 0.50%, and the remainder is water; The inorganic salt component includes a first inorganic salt and a second inorganic salt. The first inorganic salt includes a fluoride salt, and the second inorganic salt is selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

2. The silica scale cleaning agent as described in claim 1, characterized in that, The fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

3. The silica scale cleaning agent as described in claim 1, characterized in that, The mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:

1.

4. The silica scale cleaning agent as described in claim 1, characterized in that, The acidic solution comprises an acidic substance and a solvent, wherein the acidic substance comprises organic acid and inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:

1.

5. The silica scale cleaning agent as described in claim 4, characterized in that, The solvent is water, and the mass ratio of the organic acid and the inorganic acid to water is 0.3:1 to 1:

1.

6. The silica scale cleaning agent as described in claim 4, characterized in that, The organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

7. The silica scale cleaning agent as described in claim 6, characterized in that, The water-soluble carboxylic acids include oxalic acid and / or citric acid.

8. A method of using a silica scale cleaning agent, comprising the following steps: The first inorganic salt and the second inorganic salt are mixed to obtain an inorganic salt component, and the inorganic salt component is divided into inorganic salt component A and inorganic salt component B according to a first mass ratio; An acidic solution and water are provided, and the acidic solution and inorganic salt component A are added sequentially to the water to prepare an intermediate cleaning agent for silica scale. The silica scale is cleaned using the aforementioned intermediate cleaning agent, and inorganic salt component B is added to the intermediate cleaning agent. The first inorganic salt includes a fluoride salt, and the second inorganic salt is selected from one or more of chloride salts, bromine salts, iodide salts, and sulfate salts.

9. The method of use as described in claim 8, characterized in that, The step of preparing the intermediate cleaning agent for silica scale by sequentially adding the acidic solution and inorganic salt component A to the water includes: The acidic solution is added to water and mixed to obtain a diluted acidic solution. The inorganic salt component A is added to the acidic solution dilution to prepare an intermediate cleaning agent for silica scale.

10. The method of use as described in claim 8, characterized in that, The first mass ratio ranges from 1:9 to 7:

3.

11. The method of use as described in claim 8, characterized in that, The addition of inorganic salt component B to the intermediate cleaning agent for silica scale includes: The inorganic salt component B is divided into n parts according to the second mass ratio, where n is a positive integer greater than or equal to 2; n parts of the inorganic salt component B are added to the intermediate cleaning agent for silica scale.

12. The method of use as described in claim 11, characterized in that, n=3, the second mass ratio is (1~3):(1~3):(1~3); The step of adding n parts of the inorganic salt component B to the intermediate cleaning agent for silica scale includes: adding 3 parts of the inorganic salt component B to the intermediate cleaning agent for silica scale in sequence according to the second mass ratio.

13. The method of use as described in claim 8, characterized in that, By mass percentage, the acidic solution accounts for 0.50% to 2.75%, the inorganic salt component accounts for 0.10% to 0.50%, and the remainder is water.

14. The method of use as described in claim 8, characterized in that, The fluoride salt is selected from one or more of sodium fluoride, ammonium fluoride, and potassium fluoride; and / or the chloride salt is selected from one or more of sodium chloride, ammonium chloride, and potassium chloride.

15. The method of use as described in claim 8, characterized in that, The mass ratio of the first inorganic salt to the second inorganic salt is 10:1 to 2:

1.

16. The method of use as described in claim 8, characterized in that, The acidic solution comprises an acidic substance and a solvent, wherein the acidic substance comprises organic acid and inorganic acid, and the mass ratio of the organic acid to the inorganic acid is 1:1 to 8:

1.

17. The method of use as described in claim 16, characterized in that, The solvent is water, and the mass ratio of the organic acid and the inorganic acid to water is 0.3:1 to 1:

1.

18. The method of use as described in claim 16, characterized in that, The organic acid includes water-soluble carboxylic acids, and the inorganic acid includes hydrochloric acid.

19. The method of use as described in claim 18, characterized in that, The water-soluble carboxylic acids include oxalic acid and / or citric acid.

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