Sodium hypochlorite synthesis method based on electron beam radiation

Abstract

The invention relates to the technical field of sodium hypochlorite preparation, in particular to a sodium hypochlorite synthesis method based on electron beam radiation, which comprises the following steps: step S1, preparing an aqueous solution containing sodium chloride with the mass concentration of 0.5-5wt% as a basic reaction medium; s2, disodium hydrogen phosphate and sodium dihydrogen phosphate are added into the basic reaction medium, and the pH value is adjusted to 7.0-8.5; s3, adding not more than 1wt% of a silver ion accelerant and ethylene glycol into the basic reaction medium obtained in the step S2; and S4, putting the basic reaction medium obtained in the step S3 into a pressure-resistant reaction container. The electron accelerator is adopted to directly radiate the reaction medium, ionization and free radical reaction of sodium chloride molecules in the aqueous solution can be rapidly initiated, then the sodium chloride molecules are converted into sodium hypochlorite, use of a traditional chemical oxidizing agent or catalyst is avoided, side reactions are reduced, and therefore the synthesis efficiency and the purity of the final product are improved.

Description

Technical Field

[0001] The invention relates to the technical field of sodium hypochlorite preparation, and in particular to a sodium hypochlorite synthesis method based on electron beam radiation. Background Art

[0002] At present, sodium hypochlorite is an inorganic compound and the most common one in the hypochlorite family. It is a light yellow transparent liquid with a strong pungent odor and is a widely used strong oxidant and bleaching agent. The hypochlorous acid produced by the dissociation of sodium hypochlorite in water has a strong disinfection ability and can effectively kill bacteria, viruses and other microorganisms. Therefore, it is widely used in water treatment, medical and health care, food processing, textiles and pulp bleaching.

[0003] In the current prior art, the synthesis methods of sodium hypochlorite mainly include the following:

[0004] Liquid alkali chlorination method: This is the most commonly used method in industry. Chlorine gas is passed into a diluted sodium hydroxide (NaOH) solution to react at a suitable temperature to generate sodium hypochlorite, sodium chloride and water. This method can control the reaction conditions to prepare sodium hypochlorite of different purity levels.

[0005] Electrolysis of salt water: This method directly electrolyzes saturated or diluted salt (NaCl) aqueous solution. In the electrolytic cell, the salt is decomposed into sodium hypochlorite, hydrogen and chlorine through electrolysis. The anode produces chlorine, the cathode produces hydrogen and sodium hydroxide, and then the chlorine reacts with sodium hydroxide to form sodium hypochlorite.

[0006] However, the traditional synthesis method for preparing sodium hypochlorite has the following problems:

[0007] The liquid alkali chlorination method directly uses chlorine gas, which is highly toxic, flammable and explosive, and has extremely high requirements for operational safety. In addition, the reaction conditions of chlorine gas and sodium hydroxide need to be strictly controlled. The sodium chloride and wet chlorine gas produced in the process are highly corrosive to the equipment.

[0008] The side reaction between chlorine and sodium hydroxide during the electrolysis of brine may result in a certain proportion of sodium chloride and sodium hypochlorite mixture in the product, affecting the purity of the final product.

[0009] The above traditional methods are unable to directly use physical means to efficiently initiate the reaction, resulting in low sodium hypochlorite synthesis efficiency. Traditional methods rely on chemical oxidants or catalysts. The use of these substances not only increases the complexity of the reaction, but may also introduce impurities, affecting the purity of the final product.

[0010] In this regard, the present application specifically proposes a sodium hypochlorite synthesis method based on electron beam radiation to solve the above technical problems. Summary of the invention

[0011] The invention provides a sodium hypochlorite synthesis method based on electron beam radiation. The invention adopts an electron accelerator to directly radiate a reaction medium. The electron beam direct radiation is used as an efficient physical means to quickly induce ionization and free radical reaction of sodium chloride molecules in an aqueous solution, thereby converting the sodium chloride molecules into sodium hypochlorite. The invention avoids the use of traditional chemical oxidants or catalysts, reduces the occurrence of side reactions, thereby improving the synthesis efficiency and the purity of the final product. By controlling the dosage of the electron beam, the reaction process can be accurately regulated to ensure the high quality of the product.

[0012] The technical solution adopted by the present invention to solve the above technical problems is: a method for synthesizing sodium hypochlorite based on electron beam radiation, comprising the following steps:

[0013] Step S1: preparing an aqueous solution containing sodium chloride with a mass concentration of 0.5 wt % to 5 wt % as a basic reaction medium;

[0014] Step S2: adding disodium hydrogen phosphate and sodium dihydrogen phosphate to the basic reaction medium, and adjusting the pH value to 7.0 to 8.5;

[0015] Step S3: adding no more than 1 wt % of a silver ion promoter and ethylene glycol to the basic reaction medium obtained in step S2;

[0016] Step S4: placing the basic reaction medium obtained in step S3 into a pressure-resistant reaction container;

[0017] Step S5: directly irradiating the reaction medium using an electron accelerator with an acceleration voltage of 0.5 MeV to 5 MeV, with the radiation dose set at 5 kGy to 50 kGy;

[0018] Step S6: cooling the irradiated reaction medium, filtering and purifying the cooled reaction medium to obtain a sodium hypochlorite solution;

[0019] Step S7: adjusting the concentration of the sodium hypochlorite solution to 5wt% to 15wt%.

[0020] Furthermore, the concentration of the silver ion promoter added in step S3 is 0.01 wt % to 0.05 wt %.

[0021] Furthermore, the amount of ethylene glycol added in step S3 is 0.1 wt % to 0.5 wt % of the total mass of the reaction medium.

[0022] Furthermore, the pressure-resistant reaction vessel in step S4 is made of stainless steel, and the inner surface of the pressure-resistant reaction vessel is coated with a radiation-resistant coating with a thickness of 50 nm to 200 nm, the coating being a composite of a fluorine-containing polymer and nano-titanium dioxide.

[0023] Furthermore, during the electron beam irradiation in step S5, the temperature of the basic reaction medium is maintained in the range of 20°C to 40°C.

[0024] Furthermore, in step S6, the temperature of the reaction medium within 5 minutes of irradiation is reduced to room temperature by a cooling device.

[0025] Furthermore, in step S6, filtering and purifying the cooled reaction medium to obtain a sodium hypochlorite solution comprises:

[0026] Step S6-1: using a filter membrane with a pore size of no more than 0.2 μm to remove suspended particles and incompletely reacted solid impurities in the reaction medium;

[0027] Step S6-2: further removing small molecular organic impurities and residual inorganic salts in the reaction medium through a reverse osmosis membrane or a nanofiltration membrane to ensure that the purity of the sodium hypochlorite solution reaches at least 99.5%;

[0028] Step S6-3: Use an ion exchange column to deeply purify cations and anions to remove transition metal ions that affect product stability.

[0029] Furthermore, the cations in step S6-3 include copper ions, iron ions, manganese ions, nickel ions, and chromium ions, and the anions include bromide ions, iodide ions, sulfate ions, carbonate ions, and bicarbonate ions.

[0030] The advantages of the present invention are: the present invention provides a method for synthesizing sodium hypochlorite based on electron beam radiation, which has the following advantages:

[0031] 1. The present invention uses an electron accelerator to directly irradiate the reaction medium. As a highly efficient physical means, direct electron beam radiation can quickly induce ionization and free radical reactions of sodium chloride molecules in an aqueous solution, thereby converting them into sodium hypochlorite. There is no need to directly use chlorine gas, thereby eliminating the high toxicity and explosion risks in the storage, transportation and operation of chlorine gas, and greatly improving production safety. The present invention avoids the use of traditional chemical oxidants or catalysts, reduces the occurrence of side reactions, thereby improving the synthesis efficiency and the purity of the final product. By controlling the dose of the electron beam, the reaction process can be accurately regulated to ensure the high quality of the product.

[0032] 2. In the synthesis of sodium hypochlorite, the electron beam can almost instantly excite water molecules to form free radicals, which then participate in the oxidation reaction and quickly convert sodium chloride into sodium hypochlorite. The entire process can be completed in a relatively short time, improving production efficiency. This "instant start" feature means that the reaction can achieve a high conversion rate in a relatively short time scale, reducing energy consumption and time costs, while also reducing the possibility of side reactions, which is conducive to obtaining higher purity products.

[0033] 3. This method does not require the use of traditional chemical oxidants or catalysts, reduces the consumption of chemicals and the generation of by-products, reduces environmental pollution, is carried out in a closed reaction vessel, reduces the release of harmful gases, is more environmentally friendly, and the entire process is greener and more energy-efficient.

[0034] 4. The present invention uses ethylene glycol as ethylene glycol, which effectively prevents the decomposition of sodium hypochlorite. At the same time, the transition metal ions that may affect the stability are deeply purified by ion exchange columns, thereby enhancing the stability and shelf life of the final product.

[0035] 5. The filtration and purification step of the present invention can effectively remove various impurities in the reaction medium, including suspended particles, organic matter, inorganic salts and specific ions, which not only improves the purity of sodium hypochlorite, but also improves the safety of the product.

[0036] 6. The pressure-resistant reaction vessel in the present invention is made of stainless steel and coated with an anti-radiation coating, which improves the durability of the vessel and the stability in a radiation environment, extends the service life of the equipment, and reduces maintenance costs.

[0037] In summary, this technical solution not only achieves the efficient synthesis of high-purity sodium hypochlorite, but also shows obvious advantages in environmental protection, energy efficiency, product quality and production safety, and has important practical value and promotion prospects. DETAILED DESCRIPTION

[0038] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Embodiment 1:

[0040] A method for synthesizing sodium hypochlorite based on electron beam radiation comprises the following steps:

[0041] Step S1: preparing an aqueous solution containing sodium chloride with a mass concentration of 0.5 wt % to 5 wt % as a basic reaction medium;

[0042] Step S2: adding disodium hydrogen phosphate and sodium dihydrogen phosphate to the basic reaction medium, and adjusting the pH value to 7.0 to 8.5. Specifically, the detailed operation of step S2 can be divided into the following sub-steps:

[0043] Step S2-1: First, according to the required buffer capacity and target pH value, the optimal ratio of disodium hydrogen phosphate and sodium dihydrogen phosphate is calculated using the Henderson-Hasselbalch equation. The specific molar ratio of disodium hydrogen phosphate to sodium dihydrogen phosphate depends on the specific pH value to be achieved. According to the Henderson-Hasselbalch equation, the pH value can be calculated by the following formula: The pKa in the formula is the acid dissociation constant of the acid. For the sodium dihydrogen phosphate / disodium hydrogen phosphate system, the pKa value of sodium dihydrogen phosphate is mainly considered. The [A-] in the formula represents the concentration of disodium hydrogen phosphate, and [HA] represents the concentration of sodium dihydrogen phosphate. For example, it is adjusted according to a molar ratio of 1:10 to 10:1 (disodium hydrogen phosphate: sodium dihydrogen phosphate), and the specific ratio depends on the target pH value. If the target pH value is close to pH 7.0, the ratio of the two may be close to 1:1 or slightly higher, and the closer the target pH value is to 8.5, more disodium hydrogen phosphate is needed, and the ratio may be as high as 10:1 or higher. In this embodiment, in order to obtain a buffer solution of pH 8.0, the molar ratio of disodium hydrogen phosphate to sodium dihydrogen phosphate is 3:1 to 4:1.

[0044] Step S2-2: Accurately weigh the calculated mass of disodium hydrogen phosphate and sodium dihydrogen phosphate, dissolve disodium hydrogen phosphate in an appropriate amount of water, use warm water to promote dissolution, and stir until completely dissolved. Similarly, dissolve sodium dihydrogen phosphate in another portion of water, also ensuring complete dissolution.

[0045] Step S2-3: slowly add the dissolved disodium hydrogen phosphate solution to the basic reaction medium prepared in step S1, while monitoring the change of pH value with a pH meter.

[0046] Step S2-4: According to the pH meter reading, gradually add the pre-dissolved sodium dihydrogen phosphate solution while continuing to stir until the pH value stabilizes between 7.0 and 8.5, preferably close to the target pH value, such as 8.0.

[0047] Step S2-5: If the pH value deviates beyond the target range, fine adjustment can be made by fine-tuning the amount of disodium hydrogen phosphate or sodium dihydrogen phosphate added until the desired pH value is reached.

[0048] Step S2-6: Once the target pH value is reached, stop adding disodium hydrogen phosphate and sodium dihydrogen phosphate, and stir the solution thoroughly again to ensure homogeneity.

[0049] Step S2-7: Use a pH meter to confirm again that the pH value of the solution is stable within the desired range, and record the final pH value and the amount of disodium hydrogen phosphate and sodium dihydrogen phosphate added to provide a reference for subsequent production.

[0050] Through the above steps, the disodium hydrogen phosphate-sodium dihydrogen phosphate system can be effectively used as a buffer to adjust and maintain the pH value of the basic reaction medium within an ideal range of 7.0 to 8.5, thereby creating suitable reaction conditions for the subsequent electron beam radiation synthesis of high-purity sodium hypochlorite.

[0051] Step S3: adding no more than 1wt% of a silver ion promoter and ethylene glycol to the basic reaction medium obtained in step S2, specifically, the concentration of the silver ion promoter is 0.01wt% to 0.05wt%. The silver ion promoter can promote the generation of free radicals or stabilize free radicals, thereby accelerating the polymerization reaction.

[0052] The amount of ethylene glycol added is 0.1wt% to 0.5wt% of the total mass of the reaction medium;

[0053] In the present embodiment, the generation of sodium hypochlorite is mainly obtained by the reaction of free radicals (such as hydrated electrons and hydroxyl radicals) generated by direct action of electron beam radiation on water molecules with sodium chloride. The role of copper ions in this atypical free radical system can be understood as auxiliary catalysis and stabilization. Auxiliary catalysis: Although direct free radical chain growth is not the main way in the synthesis of sodium hypochlorite, copper ions, as transition metal ions, indirectly promote the ionization of water molecules or the generation of free radicals by forming complexes or through their own redox cycles, thereby accelerating the reaction of sodium chloride being converted into sodium hypochlorite. Stabilization effect: copper ions or other transition metal ions can stabilize reaction intermediates or products through coordination to avoid unnecessary side reactions. In the synthesis of sodium hypochlorite, although the direct free radical stabilization effect is not obvious, the presence of copper ions can help stabilize the chemical environment in the solution, reduce the free radical activity that may damage sodium hypochlorite, and indirectly ensure the stability of the product.

[0054] The concentration of the silver ion promoter is limited to between 0.01wt% and 0.05wt%, which is a relatively low concentration range designed to balance the promotion effect with potential side effects (such as increased side reactions or metal ion residue problems; too high a concentration may lead to over-catalysis, cause side reactions or affect the properties of the final product).

[0055] Step S4: placing the basic reaction medium obtained in step S3 into a pressure-resistant reaction container; the pressure-resistant reaction container needs to be sterilized by high-pressure steam before irradiation to ensure a sterile environment. The pressure-resistant reaction container is made of stainless steel, and a layer of radiation-resistant coating with a thickness of 50nm to 200nm is coated on the inner surface of the pressure-resistant reaction container. The coating is composed of a fluorine-containing polymer and nano-titanium dioxide composite, and is intended to enhance the resistance of the container to electron beam radiation and reduce radiation damage to the container material. At the same time, the coating can also effectively inhibit the recombination of free radicals in the reaction medium, further improving the yield and purity of sodium hypochlorite.

[0056] Step S5: Use an electron accelerator with an accelerating voltage of 2MeV to directly irradiate the basic reaction medium. The 2MeV accelerating voltage is in the middle of the recommended range of 0.5MeV to 5MeV, which can effectively excite water molecules to produce free radicals. At the same time, compared with higher energy, it can better control side reactions, reduce unnecessary energy consumption and potential radiation hazards; during the electron beam irradiation, the temperature of the basic reaction medium is maintained at 30°C. 30°C is a moderate temperature point that can promote the generation of free radicals and subsequent reactions. It is easy to control and maintain in an industrial environment. No additional complex cooling or heating system is required, which simplifies the operation process. At the same time, it avoids excessive temperature causing an increase in side reactions or product decomposition, and maintains the stability of the reaction system; the radiation dose is set at 20kGy. After experiments, a dose of 20kGy can ensure that the radiation energy penetrates and is evenly distributed in the reaction medium, promotes deep chemical reactions, and makes the generated sodium hypochlorite more evenly distributed. Specifically, the primary radiation process of the electron accelerator is: high-energy electrons directly hit water molecules, causing the water molecules to ionize and excite, and produce free radicals such as ·OH (hydroxyl radicals) and H· (hydrogen atom radicals). These highly reactive free radicals are key intermediates in radiation chemical reactions. The secondary process is: the generated free radicals further react with other solute molecules (sodium chloride NaCl). The ·OH free radicals can attack the chloride ions (Cl-) in the sodium chloride to form hypochlorite ions (ClO-): Cl - + ·OH→ClO - +H - At the same time, water molecules can also be excited to produce H+, which helps to balance the charge in the reaction. The formed hypochlorite ions (ClO-) combine with Na+ in the solution to form sodium hypochlorite (NaClO): Na + +ClO - →NaClO. The accelerating voltage range of the electron accelerator (0.5MeV to 5MeV) provides enough energy to excite water molecules, thereby starting this series of reactions and ultimately obtaining a sodium hypochlorite solution. Compared with traditional chemical synthesis methods, this method has the advantages of being environmentally friendly, fast in reaction speed, and high in product purity.

[0057] Step S6: Cooling the irradiated reaction medium (using a cooling device to cool the reaction medium temperature to room temperature within 5 minutes of irradiation). Rapid cooling can help reduce side reactions that may occur at high temperatures. These side reactions may produce unwanted products or reduce the purity and yield of the target product. Rapid cooling can prevent further undesirable chemical changes.

[0058] The cooled reaction medium is filtered and purified to obtain a sodium hypochlorite solution. In step S6, the cooled reaction medium is filtered and purified to obtain a sodium hypochlorite solution, which comprises:

[0059] Step S6-1: Use a filter membrane with a pore size of no more than 0.2 μm to remove suspended particles and incompletely reacted solid impurities in the reaction medium. After this step, the solution becomes clearer, reducing the clogging problem that may be encountered in subsequent steps, and also reducing the risk of contamination of the ion exchange column and reverse osmosis membrane.

[0060] Step S6-2: Use a reverse osmosis membrane to further remove small molecule organic impurities and residual inorganic salts in the reaction medium to ensure that the purity of the sodium hypochlorite solution reaches at least 99.5%. Reverse osmosis is a high-pressure driven membrane separation technology that can effectively remove small molecule organic impurities and inorganic salts in aqueous solutions. In this link, it is mainly used to further purify the reaction medium and remove small molecule pollutants that cannot be blocked by the pore size filter membrane. It can significantly improve the purity of the sodium hypochlorite solution and ensure that it contains no or very little organic matter and residual inorganic salts, thereby achieving a purity requirement of at least 99.5%;

[0061] Step S6-3: Use an ion exchange column to deeply purify cations and anions to remove transition metal ions that affect product stability. Cations include copper ions, iron ions, manganese ions, nickel ions, and chromium ions. Anions include bromide ions, iodide ions, sulfate ions, carbonate ions, and bicarbonate ions. Ion exchange is the principle of selectively exchanging active ions on the resin with specific ions in the solution to remove specific cation and anion impurities. Through deep purification, factors that may cause sodium hypochlorite degradation and instability are effectively eliminated. In particular, the removal of transition metal ions is crucial to improving the stability of the product for long-term storage. The resulting sodium hypochlorite solution is not only of high purity, but also of good chemical stability, and is suitable for high-end applications where the impurity content needs to be strictly controlled.

[0062] Step S7: The concentration of the sodium hypochlorite solution is adjusted to 5wt% to 15wt%. Specifically, the purified sodium hypochlorite solution can be diluted by adding deionized water until the target concentration is reached (this process requires precise measurement, and the concentration can be monitored by tools such as a specific gravity bottle, a refractometer or a conductivity meter to ensure accuracy). The purified sodium hypochlorite solution is adjusted to a specific concentration range, i.e., 5wt% to 15wt%. The main purpose is to meet the specific requirements of different application fields for the concentration of sodium hypochlorite solution. Adapt to the concentration requirements of different uses: Different application scenarios have different concentration requirements for sodium hypochlorite solutions. Low-concentration sodium hypochlorite solutions (such as 5wt%) are more suitable for daily cleaning and disinfection, surface disinfection in the food processing industry, etc., while higher-concentration solutions (such as 15wt%) are used in industrial water treatment, pulp bleaching, textile disinfection and other fields that require stronger oxidation capacity. By adjusting to an appropriate concentration, the storage stability and safety of the sodium hypochlorite solution can be optimized.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing sodium hypochlorite based on electron beam radiation, characterized in that: The following steps are involved: Step S1: preparing an aqueous solution containing sodium chloride with a mass concentration of 0.5 wt % to 5 wt % as a basic reaction medium; Step S2: adding disodium hydrogen phosphate and sodium dihydrogen phosphate to the basic reaction medium, and adjusting the pH value to 7.0 to 8.5; Step S3: adding no more than 1 wt % of a silver ion promoter and ethylene glycol to the basic reaction medium obtained in step S2; Step S4: placing the basic reaction medium obtained in step S3 into a pressure-resistant reaction container; Step S5: directly irradiating the reaction medium using an electron accelerator with an acceleration voltage of 0.5 MeV to 5 MeV, with the radiation dose set at 5 kGy to 50 kGy; Step S6: cooling the irradiated reaction medium, filtering and purifying the cooled reaction medium to obtain a sodium hypochlorite solution; Step S7: adjusting the concentration of the sodium hypochlorite solution to 5wt% to 15wt%.

2. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: The concentration of the silver ion promoter added in step S3 is 0.01 wt % to 0.05 wt %.

3. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: The amount of ethylene glycol added in step S3 is 0.1 wt % to 0.5 wt % of the total mass of the reaction medium.

4. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: The pressure-resistant reaction container in step S4 is made of stainless steel, and the inner surface of the pressure-resistant reaction container is coated with a radiation-resistant coating with a thickness of 50 nm to 200 nm, which is a composite of fluorine-containing polymer and nano-titanium dioxide.

5. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: During the electron beam irradiation in step S5, the temperature of the basic reaction medium is maintained in the range of 20°C to 40°C.

6. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: In step S6, the temperature of the reaction medium within 5 minutes of irradiation is lowered to room temperature by a cooling device.

7. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 1, characterized in that: The step S6 of filtering and purifying the cooled reaction medium to obtain a sodium hypochlorite solution comprises: Step S6-1: using a filter membrane with a pore size of no more than 0.2 μm to remove suspended particles and incompletely reacted solid impurities in the reaction medium; Step S6-2: further removing small molecular organic impurities and residual inorganic salts in the reaction medium through a reverse osmosis membrane or a nanofiltration membrane to ensure that the purity of the sodium hypochlorite solution reaches at least 99.5%; Step S6-3: Use an ion exchange column to deeply purify cations and anions to remove transition metal ions that affect product stability.

8. A method for synthesizing sodium hypochlorite based on electron beam radiation according to claim 7, characterized in that: The cations in step S6-3 include copper ions, iron ions, manganese ions, nickel ions, and chromium ions, and the anions include bromide ions, iodide ions, sulfate ions, carbonate ions, and bicarbonate ions.