Preparation method of slightly acidic electrolyzed preservation water

Abstract

This invention relates to a method for preparing slightly acidic electrolyzed preservation water, comprising: introducing sodium chloride electrolyte into the cathode chamber of an anion exchange membrane electrolyzer and high-purity water into the anode chamber for primary electrolysis to obtain first acidic electrolyzed water with a pH of 2.0–5.0; introducing the first acidic electrolyzed water into the anode chamber of a cation exchange membrane electrolyzer and pure water into the cathode chamber for secondary electrolysis to obtain second acidic electrolyzed water with a pH of 3.0–6.0; and introducing the second acidic electrolyzed water into the anode chamber of the cation exchange membrane electrolyzer and pure water into the cathode chamber for circulating electrolysis to obtain the slightly acidic electrolyzed preservation water with a pH of 5.0–6.5. This water is free of metal ions, has high hypochlorous acid purity, good stability, excellent microbial killing performance, leaves no residue or pollution, is environmentally friendly, and is suitable for the preservation and disinfection of agricultural products, especially fresh medicinal herbs.

Description

Technical Field

[0001] This invention relates to the field of agricultural product processing, and in particular to a slightly acidic electrolyzed preservative water and its preparation method. Background Technology

[0002] Agricultural products not only provide humans with abundant nutrients such as protein, carbohydrates, lipids, vitamins, inorganic elements, dietary fiber, and water, but also contain various organic substances that can be used to prevent and treat diseases, such as terpenes and volatile oils, alkaloids, flavonoids, quinones, phenylpropanoids, triterpenes and their glycosides, steroids and their glycosides, sugars and their glycosides, etc. my country has a vast territory and a wide variety of agricultural products, most of which are supplied to the market fresh. However, a large amount of agricultural products are not preserved, leading to serious spoilage and loss. According to estimates by the Food and Agriculture Organization of the United Nations, the post-harvest loss rate of agricultural products worldwide is very high, ranging from 10% to 15% in developed countries and exceeding 25% in developing countries. Reducing the post-harvest loss rate of agricultural products to 5% would be equivalent to increasing production by hundreds of millions of tons, which is crucial for ensuring human survival and development. Therefore, in-depth research on agricultural product preservation technology is of great significance for promoting agricultural development.

[0003] Agricultural product preservation involves using physical or chemical methods to slow down the decline in freshness and prevent spoilage, maintaining the product's quality and freshness. Fresh agricultural products exhibit respiration and evaporation, and their surfaces are often covered with numerous bacteria, viruses, and other microorganisms. Therefore, during harvesting, processing, transportation, and storage, agricultural products are susceptible to physical damage, chemical changes, and the action of endogenous enzymes and microorganisms, making them highly prone to spoilage and causing food safety risks and economic losses. Microorganisms and their metabolites are a key cause of spoilage. Therefore, effectively controlling microorganisms is crucial for ensuring the nutritional value and freshness of agricultural products, extending their shelf life, reducing losses, and improving their quality and safety.

[0004] Given the importance of agricultural product preservation, various storage and preservation technologies have been developed, including physical preservation technologies such as low-temperature preservation, ice-temperature preservation, heat treatment, radiation storage, and controlled atmosphere storage; chemical preservation technologies such as Fusarium wilt treatment, calcium chloride treatment, ethanol fumigation, 1-methylcyclopropene treatment, and deoxygenation preservation; and biological preservation technologies such as natural plant preservatives, natural animal preservatives, and microbial preservatives. While these preservation technologies are effective, they still have many aspects that need improvement. For example, traditional heat sterilization can significantly damage the flavor, color, and nutritional components of agricultural products; materials such as PE and PVC used in controlled atmosphere storage are difficult to degrade and can easily cause environmental pollution; UV technology has problems such as high energy consumption, easy damage, and the generation of toxic substances; and ultra-high pressure, pulsed electric field, ultrasonic, cold plasma sterilization, high hydrostatic pressure sterilization, and high-density CO2 sterilization have disadvantages such as high sterilization costs or significant impact on food quality. Active atmosphere packaging (APP) technology relies on low-temperature environments, requiring cold storage facilities, which incurs significant costs. Furthermore, low-temperature storage is prone to chilling injury, leading to various biochemical and physiological dysfunctions that negatively impact the quality of agricultural products. Chemical treatment technologies raise concerns about the use and overuse of additives. Biological preservation technologies, on the other hand, suffer from drawbacks such as cumbersome operation and high implementation costs, thus their application in agricultural product preservation is relatively limited and requires further research and exploration.

[0005] Traditional Chinese medicine (TCM) falls under the category of agricultural products, and fresh TCM herbs were among the earliest medicinal materials used to prevent and treat diseases. Data shows that of the more than 2,000 commonly used TCM herbs, over 600 were traditionally used primarily as fresh herbs. Since the harvesting season for TCM herbs is mostly autumn or spring, ensuring a year-round supply of high-quality fresh herbs requires a preservation period of 3-6 months, or even up to 12 months. This places higher demands on the preservation techniques for fresh herbs. Traditional preservation techniques for fresh medicinal herbs include natural storage, sand storage, sand planting, refrigeration, and transplanting. Modern preservation methods include physical techniques such as controlled atmosphere storage, irradiation storage, vacuum freeze-drying, cryogenic storage, vacuum refrigeration, ultrasonic treatment, ozone preservation, critical low-temperature high-humidity preservation, and structured water technology; chemical preservation techniques such as SO2 fumigation, chemical soaking (e.g., sodium sulfite, γ-aminobutyric acid, oxalic acid), and chemical coating; and biological preservation techniques such as antagonistic microbial cell preservation, microbial secondary metabolite preservation, and antimicrobial peptide preservation. However, these techniques rarely achieve a shelf life of 6-12 months. Constrained by these relatively outdated traditional Chinese medicine preservation techniques, the development and clinical application of fresh medicinal herbs are severely limited.

[0006] In recent years, slightly acidic electrolyzed water for preservation has been widely used for disinfection of medical devices and supplies, skin and mucous membranes, food and beverage utensils and processing equipment, fruits and vegetables, object surfaces, and environmental surfaces due to its highly efficient and broad-spectrum bactericidal and viral killing effects. It has gained attention for its low concentration, effective bactericidal and viral killing, lack of residue and pollution, mild use, and environmental friendliness. The national standard GB28234-2020, "Hygienic Requirements for Acidic Electrolyzed Water Generators," specifies the performance and physicochemical indicators of slightly acidic electrolyzed water for preservation: ① Colorless and transparent liquid with a slight chlorine odor. ② The main effective component is hypochlorous acid (HClO), with an effective chlorine content of 40mg / L-80mg / L. ③ pH value of 5.0-6.5. ④ Oxidation-reduction potential (ORP) ≥ 600mV. ⑤ Residual chloride ions < 1000mg. ⑥ Heavy metal content meets the requirements of GB5749. Under the aforementioned physicochemical conditions, slightly acidic hypochlorous acid can kill microorganisms such as Staphylococcus aureus (ATCC6538), Escherichia coli (8099), Candida albicans (ATCC10231), and Pseudomonas aeruginosa (ATCC15442) within 1 minute, and achieve a laboratory kill log of over 5.00 against poliovirus type I vaccine strain within 5 minutes. Its disinfection effect against Escherichia coli is superior to that of ClO₂ at the same concentration. - Up to 80 times more efficient. Slightly acidic electrolyzed preservative water boasts advantages such as low production material costs, high disinfection efficiency, broad-spectrum disinfection, no chlorine (Cl2) residue, water-saving effect due to the elimination of the need for rinsing, and complete safety without concerns about improper operation, accidental ingestion, or skin contact. Therefore, it has seen rapid development and application in the sterilization and disinfection of agricultural products.

[0007] The current methods for preparing slightly acidic electrolyzed preservative water mainly employ the following two approaches. One approach involves passing hydrochloric acid, industrial salt, or a dilute seawater solution into an electrolytic cell without a diaphragm (or membrane) for electrolysis, and obtaining the product through the following reaction.

[0008] (1) NaCl = Na + +C1 - (2) H2O=H + +OH - (3) Anode: 2Cl - -2e=Cl2;(4) Cathode:2H + +2e = H2;

[0009] Between the two electrodes, the product undergoes a secondary reaction:

[0010] (1)Cl2+2NaOH=NaCl+NaClO+2H2O. (2)NaClO+HCl=HClO+NaCl.

[0011] Another method is to use industrial salt or a dilute seawater solution to pass through an electrolytic cell with a diaphragm (or membrane) for electrolysis, and obtain the product through the following reaction.

[0012] (1) NaCl = Na + +C1 - (2) H2O=H + +OH - (3) Anode: 2Cl - -2e-=Cl2;(4) Cathode: 2H + +2e = H2;

[0013] (3) Anode: Cl2 + H2O = HClO + H + +Cl-;(4) Cathode: 2H + +2e- = H2;

[0014] A partition (or diaphragm) divides the electrolytic cell into two chambers: the anode chamber and the cathode chamber. On the anode surface, two chloride ions lose two electrons to generate chlorine gas. The chlorine gas dissolves in water to form equimolar amounts of hydrochloric acid and hypochlorous acid. Therefore, only 50% of the chloride ions are used to generate the required hypochlorous acid, and the other 50% to generate hydrochloric acid. Consequently, the electrolyzed water generated on the anode side has a pH value below 7.0. Furthermore, the higher the concentration of hypochlorous acid generated, the higher the concentration of hydrochloric acid generated, and the lower the pH value of the electrolyzed water. According to GB28234-2020, when the effective chlorine concentration of the electrolyzed water on the anode side is between 40 mg / L and 80 mg / L, the pH value of the electrolyzed water is 2–3. If the pH value of the electrolyzed water on the anode side is between 5.0 and 6.5, the resulting disinfectant solution contains an effective chlorine concentration below 5 mg / L, far below the concentration required for actual disinfection. To meet the physicochemical indicators of slightly acidic electrolyzed water for preservation as specified in GB28234-2020, it is necessary to add an alkaline solution to the acidic electrolyzed water to adjust the pH value and effective chlorine concentration to meet the requirements. Alternatively, the acidic electrolyzed water can be electrolyzed again to allow the chloride ions in the electrolyzed water to continue to generate hypochlorous acid, thereby increasing the effective chlorine concentration and pH value.

[0015] Currently, many manufacturers both domestically and internationally utilize diaphragm-free electrolyzers to produce slightly acidic electrolyzed preservative water. This involves electrolyzing a mixed solution of hydrochloric acid and sodium chloride. However, the hydrochloric acid and sodium chloride mixture is highly acidic, corrosive, and irritating, posing significant safety risks. Leaks can easily cause burns to equipment and personnel. Hydrochloric acid is a strong industrial acid and a precursor to toxic substances, subject to strict national regulations. Its use also poses substantial environmental problems. Therefore, avoiding the use of hydrochloric acid has become a consensus within the industry. While using a diaphragm electrolyzer to produce slightly acidic electrolyzed fresh water eliminates the need for hydrochloric acid, its electrolysis efficiency is lower compared to diaphragm-free electrolyzers. Production is significantly affected by the performance of the diaphragm or separator, as well as by parameters such as the purity of sodium chloride raw material, salt solution concentration, electrolysis voltage and current, electrolyte flow rate, and chlorine concentration. Furthermore, real-time online monitoring of available chlorine content, pH value, and chloride ion content is required during production, along with real-time adjustment of the sodium hydroxide solution flow rate. The complexity and high cost of these online monitoring and automatic control systems severely hinder their application and widespread adoption.

[0016] Agricultural product preservation aims to maintain the original quality and freshness of agricultural products to the maximum extent possible over a relatively long period. In other words, fresh agricultural products, after a period of preservation and storage, should retain the freshness and quality of just harvested or nearly so. Therefore, if slightly acidic electrolyzed preservation water is used for agricultural product preservation, it must possess long-term stability, meaning it should maintain stable physicochemical properties and sustained activity in killing microorganisms during the preservation period. The active component of slightly acidic electrolyzed preservation water is hypochlorous acid. In the structure of hypochlorous acid (HClO), chlorine has a +1 valence, a high oxidation state, and a strong tendency to gain electrons. This makes the HClO molecule highly oxidizing and extremely unstable, easily decomposing and losing its activity under various influences. Therefore, slightly acidic electrolyzed preservation water should be prepared immediately before use and stored in light-proof, airtight containers made of rigid polyvinyl chloride (PVC) at room temperature for no more than 3 days. Therefore, the current industry methods for preparing slightly acidic electrolyzed preservation water obviously cannot meet the requirements of agricultural product preservation for slightly acidic electrolyzed preservation water to be stable and maintain microbial killing for a long time.

[0017] Factors affecting the stability of hypochlorous acid in slightly acidic electrolyzed preservation water include light, temperature, pH, concentration, and impurities. Higher temperatures and concentrations increase the likelihood of disproportionation reactions, while light exposure promotes photolysis. Metal ions and heavy metal ions readily catalyze the decomposition of hypochlorous acid. Therefore, slightly acidic electrolyzed preservation water should be stored in brown or opaque containers under sealed, light-proof, dry, and cool conditions. Even with strict adherence to the aforementioned storage conditions, the shelf life of slightly acidic electrolyzed preservative water remains very short, ranging from only 1-2 weeks to 2-3 months. This is due to the lack of effective control over impurities, particularly the content of metal ions, in the slightly acidic electrolyzed preservative water. Studies have shown that metal ions can catalyze the decomposition of hypochlorous acid, leading to a rapid decrease in hypochlorous acid concentration. Therefore, slightly acidic electrolyzed preservative water prepared according to GB28234-2020 cannot meet the requirements for maintaining the original quality and freshness of agricultural products to the maximum extent over a long period of time, especially for fresh medicinal herbs which require preservation for up to one year. Summary of the Invention

[0018] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing high-purity, high-stability, slightly acidic electrolyzed preservation water for the preservation of agricultural products, especially fresh Chinese medicinal herbs.

[0019] To achieve the above objectives, the present invention adopts the following technical solution:

[0020] A method for preparing slightly acidic electrolyzed preservative water includes the following steps:

[0021] Sodium chloride electrolyte is introduced into the cathode chamber of the anion exchange membrane electrolyzer, and high-purity water is introduced into the anode chamber for primary electrolysis to obtain first-stage acidic electrolyzed water with a pH value of 2.0 to 5.0.

[0022] The first acidic electrolyzed water is introduced into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber for secondary electrolysis to obtain second acidic electrolyzed water with a pH value of 3.0–6.0; and

[0023] The second acidic electrolyzed water is introduced into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber for circulating electrolysis to obtain the slightly acidic electrolyzed fresh water with a pH value of 5.0 to 6.5.

[0024] In some embodiments, sodium chloride electrolyte is introduced into the cathode chamber of the anion exchange membrane electrolyzer, and high-purity water is introduced into the anode chamber. A 5-100V DC power supply is connected to perform primary electrolysis. First alkaline electrolyzed water is obtained at the cathode chamber outlet, and first acidic electrolyzed water with a pH value of 2.0 to 5.0 is obtained at the anode outlet.

[0025] In some embodiments, first acidic electrolyzed water generated by primary electrolysis is introduced into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber. A 5-100V DC power supply is connected to perform secondary electrolysis, and second acidic electrolyzed water with a pH of 3.0 to 6.0 is obtained at the anode side outlet and stored in a storage tank; second alkaline electrolyzed water is obtained at the cathode side outlet.

[0026] In some implementations, the second acidic electrolyzed water in the storage tank is pumped into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber. A 5-100V DC power supply is connected to perform circulating electrolysis, and slightly acidic electrolyzed fresh water with a pH value of 5.0 to 6.5 is obtained on the anode side.

[0027] In some embodiments, the sodium chloride in the sodium chloride electrolyte accounts for 0.1% to 20% of the electrolyte by mass.

[0028] In some specific embodiments, the sodium chloride accounts for 0.2% to 10% of the mass percentage of the electrolyte.

[0029] The high-purity water is water that has been treated to pure water through a reverse osmosis membrane and then treated by continuous electrodeionization (EDI) technology or a mixed ion exchange resin column. The high-purity water has an impurity content of less than 0.1 mg / L, a conductivity of less than 0.1 μS / cm, and a pH of 6.8 to 7.0.

[0030] The flow rate of the sodium chloride electrolyte is 0.1 L / min to 10.0 L / min; preferably, the flow rate of the sodium chloride electrolyte is 1.0 L / min to 5.0 L / min.

[0031] The flow rate of the high-purity water is 0.1 L / min to 5.0 L / min. Preferably, the flow rate of the high-purity water is 0.5 L / min to 3.0 L / min.

[0032] The electrolysis process parameters of the anion exchange membrane electrolyzer are a DC voltage of 5V to 100V and a current of 5 to 100A. Preferably, the electrolysis process parameters of the anion exchange membrane electrolyzer are a DC voltage of 10V to 50V and a current of 5A to 40A.

[0033] The anode chamber of the cation exchange membrane electrolyzer is circulated with first-stage acidic electrolyzed water produced by primary electrolysis, while the cathode chamber is circulated with pure water for secondary electrolysis.

[0034] The pure water is water with an impurity content of 1.0 to 5.0 mg / L and an electrical conductivity of less than 1.0 to 10.0 μS / cm.

[0035] The flow rate of the first acidic electrolyzed water with pH 2.0 to 5.0 is 0.1 L / min to 10.0 L / min; preferably, the flow rate of the first acidic electrolyzed water with pH 2.0 to 5.0 is 1.0 L / min to 5.0 L / min.

[0036] The flow rate of the pure water is 0.1 L / min to 5.0 L / min. Preferably, the flow rate of the pure water is 0.5 L / min to 3.0 L / min.

[0037] The electrolysis process parameters of the cation exchange membrane electrolyzer are a DC voltage of 5V to 100V and a current of 1A to 50A. Preferably, the electrolysis process parameters of the cation exchange membrane electrolyzer are a DC voltage of 10V to 50V and a current of 5A to 40A.

[0038] The second acidic electrolyzed water with a pH of 3.0 to 6.0 generated by the secondary electrolysis is pumped into the anode chamber of the cation exchange membrane electrolyzer, while pure water is introduced into the cathode chamber for circulating electrolysis.

[0039] The pure water is water with an impurity content of 1.0 to 5.0 mg / L and an electrical conductivity of less than 1.0 to 10.0 μS / cm.

[0040] The flow rate of the second acidic electrolyzed water is 1.0 L / min to 5.0 L / min; preferably, the flow rate of the second acidic electrolyzed water is 2.0 L / min to 4.0 L / min.

[0041] The flow rate of the pure water is 0.5 L / min to 5.0 L / min. Preferably, the flow rate of the pure water is 0.5 L / min to 2.0 L / min.

[0042] The process parameters for the cyclic electrolysis are a DC voltage of 5V to 100V and a current of 1A to 50A. Preferably, the process parameters for the cyclic electrolysis are a DC voltage of 10V to 50V and a current of 5A to 40A.

[0043] This invention also provides a slightly acidic electrolyzed preservative solution obtained by the above-described method for preparing slightly acidic electrolyzed preservative water. This invention also provides a method for preserving agricultural products, comprising applying the slightly acidic electrolyzed preservative water of claim 10 to the agricultural products.

[0044] Compared with the prior art, the present invention has the following characteristics:

[0045] The present invention provides a method for preparing slightly acidic electrolyzed preservative water, employing a two-stage electrolytic cell series electrolysis method combined with a circulating electrolysis method. Specifically, the first stage uses an anion exchange membrane electrolyzer to electrolyze a sodium chloride electrolyte, generating acidic electrolyzed water. The second stage uses a cation exchange membrane electrolyzer to electrolyze the acidic electrolyzed water generated in the first stage, thereby increasing the concentration and purity of hypochlorous acid and reducing the concentration of metal ions. The acidic electrolyzed water generated in the second stage is then repeatedly circulated and electrolyzed in a cation exchange membrane electrolyzer to further increase the concentration and purity of hypochlorous acid and reduce the concentration of metal ions. The final product is slightly acidic electrolyzed preservative water with high-purity hypochlorous acid and no metal ions.

[0046] The first stage of electrolysis involves electrolyzing a sodium chloride solution using an anion exchange membrane electrolyzer. Sodium chloride electrolyte is introduced into the cathode chamber, and high-purity water is introduced into the anode chamber. When direct current is applied to the electrolyzer, the Cl- in the cathode chamber... - Driven by voltage and current, Cl - It enters the anode chamber through the anion exchange membrane and loses electrons at the anode surface to generate Cl2. Cl2 dissolves in water to form hypochlorous acid and H2. + and Cl - The first acidic electrolyzed water, with a pH of 2.0 to 5.0, flows out from the anode chamber; while the first alkaline electrolyzed water is obtained because the cations cannot pass through the anion exchange membrane and flow out from the cathode chamber.

[0047] The first-stage electrolysis uses an anion exchange membrane electrolyzer, which completely isolates the anode and cathode chambers. Only anions can pass through the anion exchange membrane into the anode chamber in the cathode chamber, while cations cannot pass through the anion exchange membrane into the anode chamber. Therefore, the concentration of metal ions in the first acidic electrolyzed water produced in the anode chamber is greatly reduced, resulting in first acidic electrolyzed water with high hypochlorous acid purity.

[0048] The second-stage electrolysis uses a cation exchange membrane electrolyzer to electrolyze the first acidic electrolyzed water produced in the first stage. The first acidic electrolyzed water is introduced into the anode chamber, and pure water is introduced into the cathode chamber. When direct current is applied to the electrolyzer, trace metal ions in the first acidic electrolyzed water in the anode chamber pass through the cation exchange membrane into the cathode chamber under the drive of voltage and current. Simultaneously, Cl- in the anode chamber... - At the anode surface, electrons are lost to generate Cl2. Cl2 dissolves in water to form hypochlorous acid, thus increasing the concentration of Cl in the anode chamber. - The concentration is further reduced and flows out from the anode chamber, resulting in second acidic electrolyzed water with a pH of 3.0–6.0; while the cations flow out from the cathode chamber through the cation exchange membrane, resulting in second alkaline electrolyzed water.

[0049] The second-stage electrolysis uses a cation exchange membrane electrolyzer, which completely isolates the anode and cathode chambers. Only cations in the anode chamber can pass through the cation exchange membrane into the cathode chamber, while anions cannot. Therefore, the concentration of metal ions in the second acidic electrolyzed water produced in the anode chamber is significantly reduced. Simultaneously, the residual Cl in the first acidic electrolyzed water... - At the anode surface, electrons are lost to generate Cl2. Cl2 dissolves in water to form hypochlorous acid, thus increasing the concentration of Cl in the anode chamber. - The concentration was further reduced to obtain a second acidic electrolyzed water with higher hypochlorous acid purity.

[0050] The aforementioned cyclic electrolysis involves repeatedly electrolyzing the second acidic electrolyzed water produced in the second-stage electrolysis to further reduce the Cl- content. - This method aims to increase the concentration and purity of hypochlorous acid in the second acidic electrolyzed water by adjusting the concentration of metal ions. The circulating electrolysis uses a cation exchange membrane electrolyzer, where the second acidic electrolyzed water produced in the second stage is introduced into the anode chamber, and pure water is introduced into the cathode chamber. A direct current is applied to repeatedly circulate and electrolyze the second acidic electrolyzed water. Trace metal ions in the second acidic electrolyzed water in the anode chamber pass through the cation exchange membrane into the cathode chamber under the drive of voltage and current; simultaneously, trace amounts of Cl- in the anode chamber... - At the anode surface, electrons are lost to generate Cl2. Cl2 dissolves in water to form hypochlorous acid, thus increasing the concentration of Cl in the anode chamber. - The concentration further decreased and flowed out from the anode chamber, resulting in a metal-free, ultra-low Cl-free solution with a pH of 5.0–6.5. - Slightly acidic electrolyzed water with high ion content of hypochlorous acid.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] The slightly acidic electrolyzed preservation water of this invention uses a common, readily available, safe, and non-toxic sodium chloride electrolyte for electrolysis. The resulting slightly acidic electrolyzed preservation water has a pH value of 5.0–6.5, an effective chlorine concentration of 40 mg / L–10000 mg / L, and a Cl- ion concentration of less than 5% of the effective chlorine concentration. It is a slightly acidic electrolyzed preservation water free of metal ions. This preservation water exhibits excellent bactericidal and viral killing effects, with a kill logarithm greater than 5.0 against Escherichia coli (8099), Staphylococcus aureus (ATCC6538), Candida albicans (ATCC10231), Pseudomonas aeruginosa (ATCC15442), Bacillus subtilis var. niger spores (ATCC9372), and poliovirus type I vaccine strain.

[0053] The slightly acidic electrolyzed preservative water of this invention exhibits excellent stability. When packaged in an opaque brown container and stored under sealed, light-proof, dry, and cool conditions for 12 months, its available chlorine content decreases by only 5%-10%, making it a truly highly stable, high-purity slightly acidic electrolyzed preservative water containing hypochlorous acid. This preservative water can maintain the original quality and freshness of agricultural products to the maximum extent for extended periods, particularly meeting the requirement for fresh medicinal herbs to be preserved for up to one year. Attached Figure Description

[0054] Figure 1 This is a flowchart illustrating the process used in Examples 1 to 5 of this invention: a series-connected two-stage electrolysis method employing anion exchange membrane electrolyzers and cation exchange membrane electrolyzers, combined with cyclic electrolysis of the cation exchange membrane electrolyzer to prepare high-purity, high-stability, slightly acidic electrolyzed preservative water. Figure 1 In the diagram, 1 represents anion exchange membrane and 2 represents cation exchange membrane. Detailed Implementation

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0056] The present invention will be further described in detail below with reference to specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0057] The following is a specific embodiment.

[0058] Methods for preparing pure water and ultrapure water

[0059] The preparation methods of pure water and ultrapure water in this invention are as follows: Tap water (TDS value less than 200 ppm) is filtered through a PP cotton filter (melt-blown polyester fiber filter) and an activated carbon filter, and then purified through a 4040 (or 8040) reverse osmosis membrane (RO) to obtain reverse osmosis water with a conductivity of 1.0-10.0 μS / cm, an impurity content of 1.0-5.0 mg / L, and a flow rate of 4.0 L / min, which is the pure water used in this invention; the above pure water is then passed into an EDI (continuous electrolytic desalination) system to further remove impurities and various ions, to obtain water with a conductivity of less than 0.1 μS / cm, an impurity content of less than 0.1 mg / L, and a pH of 6.8-7.0, which is the ultrapure water used in this invention.

[0060] Example 1

[0061] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 2.0% sodium chloride.

[0062] (1) First stage electrolysis: The above sodium chloride electrolyte is introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 1.0 L / min, and high-purity water is introduced into the anode chamber at a flow rate of 0.5 L / min to carry out the first stage electrolysis. The electrolysis voltage and current are adjusted to obtain the first acidic electrolyzed water with a pH of 3.65 and an effective chlorine concentration of 50 mg / L in the anode chamber; and the first alkaline electrolyzed water with a pH of 12.1 is discharged from the cathode chamber.

[0063] (2) Second stage electrolysis: The first acidic electrolyzed water with a pH of 3.65 obtained in step (1) is introduced into the anode chamber of the cation exchange membrane electrolyzer. At the same time, pure water is introduced into the cathode chamber of the cation exchange membrane electrolyzer at a flow rate of 0.5 L / min to carry out the second stage electrolysis. The electrolysis voltage and current are adjusted to obtain the second acidic electrolyzed water with a pH of 4.25 and an effective chlorine concentration of 198 mg / L on the anode side.

[0064] (3) Circulating electrolysis: Open the two-way valve and pump, and pump the second acidic electrolyzed water with a pH of 4.25 obtained in step (2) into the anode chamber of the cation exchange membrane electrolyzer at a flow rate of 1.0 L / min. At the same time, pure water is introduced into the cathode chamber of the cation exchange membrane electrolyzer at a flow rate of 0.5 L / min to carry out circulating electrolysis. Adjust the electrolysis voltage and current to obtain slightly acidic electrolyzed fresh water with a pH of 5.83 and an effective chlorine concentration of 530 mg / L on the anode side.

[0065] Example 2

[0066] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 4.0% sodium chloride.

[0067] (1) First stage electrolysis: The above sodium chloride electrolyte is introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 2.0 L / min, and high-purity water is introduced into the anode chamber at a flow rate of 1.0 L / min; the electrolysis voltage and current are adjusted to carry out the first stage electrolysis, and the first acidic electrolyzed water with a pH value of 3.41 and an effective chlorine concentration of 73 mg / L is obtained on the anode side; the first alkaline electrolyzed water with a pH of 11.9 is discharged from the cathode chamber.

[0068] (2) Second stage electrolysis: The first acidic electrolyzed water with a pH of 3.41 obtained in step (1) is introduced into the anode chamber of the cation exchange membrane electrolyzer. At the same time, pure water is introduced into the cathode chamber at a flow rate of 1.0 L / min. The electrolysis voltage and current are adjusted to carry out the second stage electrolysis. The second acidic electrolyzed water with a pH of 4.94 and an effective chlorine concentration of 186 mg / L is obtained on the anode side.

[0069] (3) Circulating electrolysis: Open the two-way valve and pump, and pass the second acidic electrolyzed water with a pH of 4.94 obtained in step (2) into the anode chamber of the cation exchange membrane electrolyzer at a flow rate of 1.0 L / min. At the same time, pure water is passed into the cathode chamber at a flow rate of 1.0 L / min. Adjust the electrolysis voltage and current to carry out circulating electrolysis, and obtain slightly acidic electrolyzed fresh water with a pH of 5.53 and an effective chlorine concentration of 677 mg / L on the anode side.

[0070] Example 3

[0071] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 6.0% sodium chloride.

[0072] (1) First-stage electrolysis: The above sodium chloride electrolyte was introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 3.0 L / min, and high-purity water was introduced into the anode chamber at a flow rate of 1.5 L / min. The electrolysis voltage and current were adjusted to carry out the first-stage electrolysis; the first acidic electrolyzed water with a pH of 3.58 and an effective chlorine concentration of 92 mg / L was obtained in the anode chamber; and the first alkaline electrolyzed water with a pH of 11.7 was obtained in the cathode chamber.

[0073] (2) Second stage electrolysis: The first acidic electrolyzed water with a pH of 3.58 obtained in step (1) is introduced into the anode chamber of the cation exchange membrane electrolyzer. At the same time, pure water is introduced into the cathode chamber at a flow rate of 1.5 L / min. The electrolysis voltage and current are adjusted to carry out the second stage electrolysis. The second acidic electrolyzed water with a pH of 4.79 and an effective chlorine concentration of 230 mg / L is obtained on the anode side.

[0074] (3) Circulating electrolysis: Open the two-way valve and pump, and pass the second acidic electrolyzed water with a pH of 4.79 obtained in step (2) into the anode chamber of the cation exchange membrane electrolyzer at a flow rate of 1.0 L / min. At the same time, pure water is passed into the cathode chamber at a flow rate of 1.0 L / min. Adjust the electrolysis voltage and current to carry out circulating electrolysis. A slightly acidic electrolyzed fresh water with a pH of 5.42 and an effective chlorine concentration of 737 mg / L is obtained on the anode side.

[0075] Example 4

[0076] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 8.0% sodium chloride.

[0077] (1) First-stage electrolysis: The above sodium chloride electrolyte was introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 4.0 L / min, and high-purity water was introduced into the anode chamber at a flow rate of 2.0 L / min. The electrolysis voltage and current were adjusted to carry out the first-stage electrolysis. A first-stage acidic electrolyzed water with a pH of 4.06 and an effective chlorine concentration of 119 mg / L was obtained in the anode chamber; a first-stage alkaline electrolyzed water with a pH of 12.7 was discharged from the cathode chamber.

[0078] (2) Second stage electrolysis: The first acidic electrolyzed water with a pH of 4.06 obtained in step (1) is introduced into the anode chamber of the cation exchange membrane electrolyzer. At the same time, pure water is introduced into the cathode chamber at a flow rate of 2.0 L / min. The electrolysis voltage and current are adjusted to carry out the second stage electrolysis, and the second acidic electrolyzed water with a pH of 5.23 and an effective chlorine concentration of 231 mg / L is obtained on the anode side.

[0079] (3) Circulating electrolysis: Open the two-way valve and pump, and pass the second acidic electrolyzed water with a pH of 5.23 obtained in step (2) into the anode chamber of the cation exchange membrane electrolyzer at a flow rate of 1.0 L / min. At the same time, pure water is passed into the cathode chamber at a flow rate of 1.0 L / min. Adjust the electrolysis voltage and current to carry out circulating electrolysis, and obtain slightly acidic electrolyzed fresh water with a pH of 5.41 and an effective chlorine concentration of 923 mg / L on the anode side.

[0080] Example 5

[0081] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 10.0% sodium chloride.

[0082] (1) First-stage electrolysis: The above sodium chloride electrolyte was introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 5.0 L / min, and high-purity water was introduced into the anode chamber at a flow rate of 2.5 L / min. The electrolysis voltage and current were adjusted to carry out the first-stage electrolysis. A first-stage acidic electrolyzed water with a pH of 3.35 and an effective chlorine concentration of 106 mg / L was obtained in the anode chamber, and a first-stage alkaline electrolyzed water with a pH of 11.3 was discharged from the cathode chamber.

[0083] (2) Second stage electrolysis: The first acidic electrolyzed water with a pH of 3.35 obtained in step (1) is passed into the anode chamber of the cation exchange membrane electrolyzer. At the same time, pure water is passed into the cathode chamber at a flow rate of 2.5 L / min. The electrolysis voltage and current are adjusted to carry out the second stage electrolysis. The second acidic electrolyzed water with a pH of 4.65 and an effective chlorine concentration of 189 mg / L is obtained on the anode side.

[0084] (3) Circulating electrolysis: Open the two-way valve and pump, and add the second acidic electrolyzed water with a pH value of 4.65 obtained in step (2) to the anode chamber of the two-chamber electrolyzer with a cation exchange membrane at a rate of 1.0 L / min. At the same time, pure water is introduced into the cathode chamber at a flow rate of 1.0 L / min. Adjust the electrolysis voltage and current to carry out circulating electrolysis, and obtain slightly acidic electrolyzed fresh water with a pH value of 5.26 and an effective chlorine concentration of 1012 mg / L on the anode side.

[0085] Comparative Example 1

[0086] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 10.0% sodium chloride.

[0087] Sodium chloride electrolyte was introduced into a diaphragmless electrolytic cell at a flow rate of 1.5 L / min. Electrolysis was carried out by adjusting the electrolysis voltage and current to obtain electrolyzed water with a pH of 7.29 and an effective chlorine concentration of 37 mg / L.

[0088] Comparative Example 2

[0089] Preparation of sodium chloride electrolyte: Take an appropriate amount of high-quality refined salt (sodium chloride) without additives and nutrient fortifiers, add it to high-purity water to dissolve and prepare an electrolyte containing 10.0% sodium chloride.

[0090] The sodium chloride electrolyte was introduced into the cathode chamber of the anion exchange membrane electrolyzer at a flow rate of 5.0 L / min, and high-purity water was introduced into the anode chamber at a flow rate of 2.5 L / min. Electrolysis was carried out by adjusting the electrolysis voltage and current. Acidic electrolyzed water with a pH of 3.35 and an effective chlorine concentration of 106 mg / L was obtained in the anode chamber. Alkaline electrolyzed water with a pH of 11.3 was discharged from the cathode chamber.

[0091] The physicochemical properties of the slightly acidic electrolyzed preservation water in Examples 1-5 and Comparative Examples 1-2 are shown in Table 1.

[0092] Physicochemical indicators were tested according to the requirements of the "Disinfection Technical Specifications" (2002 edition). Chloride ion content was tested according to the method in GB / T5750.5. Metal ion content was tested according to the method in GB / T5750-2023.

[0093] Table 1. Physicochemical properties of slightly acidic electrolyzed preservation water in Examples 1-5 and Comparative Examples 1-2

[0094]

[0095] Experimental Example 1

[0096] The bactericidal and inactivation effects of the slightly acidic electrolyzed preservation water in Examples 1-5 and Comparative Examples 1-2 were tested.

[0097] Test method: Tested in accordance with GB28234-2020.

[0098] In Examples 1-5 and Comparative Example 2, ultrapure water was added to adjust the effective chlorine concentration to approximately 60 mg / L. The logarithmic values ​​of the killing and inactivation of relevant microorganisms by the slightly acidic electrolyzed preservation water prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 2.

[0099] Table 2: Logarithmic values ​​of microbial killing and inactivation in Examples 1-5 and Comparative Examples 1-2

[0100]

[0101] Experimental Example 2

[0102] The stability of the slightly acidic electrolyzed preservation water in Examples 1-5 and Comparative Examples 1-2 was tested.

[0103] Test method: The test shall be conducted in accordance with the requirements of the "Disinfection Technical Specifications" (2002 edition).

[0104] In Examples 1-5 and Comparative Example 2, ultrapure water was added to adjust the available chlorine concentration to approximately 60 mg / L. The results of the available chlorine content determination in the 1-year stability test of the samples prepared in Examples 1-5 and Comparative Examples 1-2 are shown in Table 3.

[0105] Table 3: Results of available chlorine content determination (mg / L) in the 1-year stability test of Examples 1-5 and Comparative Examples 1-2

[0106] October January February April August December Example 1 58 56 55 53 53 54 Example 2 61 58 55 56 55 55 Example 3 63 61 59 60 61 59 Example 4 59 55 54 55 55 54 Example 5 60 57 58 56 55 54 Comparative Example 1 37 11 0 0 0 0 Comparative Example 2 65 37 22 8 0 0

[0107] The physicochemical properties of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1. The results indicate that Examples 1-5, employing the two-stage electrolysis plus circulating electrolysis method of this invention, firstly, pass sodium chloride electrolyte into an anion exchange membrane electrolyzer for electrolysis, obtaining first-stage acidic electrolyzed water in the anode chamber. This first-stage acidic electrolyzed water is then passed into a cation exchange membrane electrolyzer for second-stage electrolysis, yielding second-stage acidic electrolyzed water. Finally, this second-stage acidic electrolyzed water is passed into a cation exchange membrane electrolyzer for circulating electrolysis, resulting in slightly acidic electrolyzed preservation water with a pH of 5.26-5.83 and an effective chlorine concentration of 530 mg / L-1012 mg / L. This slightly acidic electrolyzed preservation water has a high effective chlorine concentration, a chloride ion concentration of less than 5% of the effective chlorine concentration, and contains no metal ions. Comparative Example 1, using a diaphragm-free electrolysis method, produced alkaline electrolyzed water with a pH of 7.29 and an effective chlorine concentration of only 37 mg / L, while the concentrations of chloride ions and metal ions were both above 10,000 mg / L. Comparative Example 2, using a two-chamber electrolyzer with an anion exchange membrane, electrolyzed sodium chloride electrolyte, yielded acidic electrolyzed water with a pH of 3.35 and an effective chlorine concentration of 106 mg / L at the anode side, with a chloride ion concentration as high as 1000 mg / L and a metal ion concentration of 137 mg / L.

[0108] Table 2 shows the results of the microbial killing and inactivation experiments of Examples 1-5 and Comparative Examples 1-2. Examples 1-5 showed excellent bactericidal and viral inactivation effects with log values ​​≥5.0 for the corresponding bacteria and viruses. Comparative Example 1 showed poor bactericidal effect and had no effect on Candida albicans and viruses. Comparative Example 2 showed good bactericidal and viral inactivation effects.

[0109] Table 3 shows the 12-month stability test results for Examples 1-5 and Comparative Examples 1-2. The results indicate that in Examples 1-5, the effective chlorine concentration decreased by less than 5% compared to the first month, demonstrating excellent stability and laying the foundation for long-term preservation of agricultural products. In Comparative Example 1, the effective chlorine concentration dropped to 0 after two months. In Comparative Example 2, during the 8-month period, the effective chlorine concentration had already dropped below the specified level (40-80 mg / L) in the first month, and to 0 in the eighth month. This demonstrates that the stability of Comparative Examples 1-2 is far lower than that of Examples 1-5, and they are not suitable for use as preservation water for agricultural products.

[0110] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing slightly acidic electrolyzed preservative water, characterized in that, Includes the following steps: Sodium chloride electrolyte is introduced into the cathode chamber of the anion exchange membrane electrolyzer, and high-purity water is introduced into the anode chamber for primary electrolysis to obtain first-stage acidic electrolyzed water with a pH value of 2.0 to 5.

0. The first acidic electrolyzed water is introduced into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber for secondary electrolysis to obtain the second acidic electrolyzed water with a pH value of 3.0 to 6.

0. as well as The second acidic electrolyzed water is introduced into the anode chamber of the cation exchange membrane electrolyzer, and pure water is introduced into the cathode chamber for circulating electrolysis to obtain the slightly acidic electrolyzed fresh water with a pH value of 5.0 to 6.

5.

2. The preparation method according to claim 1, characterized in that, The sodium chloride content in the sodium chloride electrolyte is 0.1% to 20% by mass, preferably 0.2% to 10%.

3. The preparation method according to claim 1 or 2, characterized in that, The flow rate and electrolysis voltage and current of the sodium chloride electrolyte are controlled so that the anode chamber of the anion exchange membrane electrolyzer generates the first acidic electrolyzed water with a pH value of 2.0 to 5.

0.

4. The preparation method according to claim 3, characterized in that, The flow rate of the sodium chloride electrolyte is 0.1 L / min to 10.0 L / min, preferably 1.0 L / min to 5.0 L / min.

5. The preparation method according to claim 3, characterized in that, The process parameters for the first-stage electrolysis are: DC voltage 5V to 100V, preferably 10V to 50V, and current 5A to 100A, preferably 5A to 40A.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The voltage and current of the secondary electrolysis are controlled so that the anode chamber of the cation exchange membrane electrolyzer generates the second acidic electrolyzed water with a pH value of 3.0 to 6.

0.

7. The preparation method according to claim 6, characterized in that, The process parameters for the secondary electrolysis are: DC voltage 5V to 100V, preferably 10V to 50V, and current 5A to 100A, preferably 5A to 40A.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The voltage and current of the circulating electrolysis are controlled so that the anode chamber of the cation exchange membrane electrolyzer generates slightly acidic electrolyzed fresh water with a pH value of 5.0 to 6.

5.

9. The preparation method according to claim 8, characterized in that, The process parameters for the cyclic electrolysis are: DC voltage 5V to 100V, preferably 10V to 50V, and current 5A to 100A, preferably 5A to 40A.

10. Slightly acidic electrolyzed preservative water obtained by the preparation method according to any one of claims 1 to 9.

11. A method for preserving agricultural products, comprising applying the slightly acidic electrolyzed preservative water of claim 10 to the agricultural products.

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