Preparation method of chlorine dioxide aqueous solution with stable concentration

Abstract

The invention discloses a preparation method of a chlorine dioxide aqueous solution with stable concentration, which comprises the following steps: Step 1: Add sodium chlorate solution and sodium chlorite solution into a reaction kettle, mix them evenly to obtain a mixed solution A; Step 2: Add a composite reducing agent and a catalyst into the reaction kettle, mix them evenly to obtain a mixed solution B; Step 3: Slowly add concentrated sulfuric acid into the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle. The reaction starts in the reaction kettle to generate chlorine dioxide gas; Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain a chlorine dioxide aqueous solution with stable concentration. The chlorine dioxide aqueous solution prepared by using the invention has high purity and stable concentration, and can still maintain the stability of the chlorine dioxide concentration at a high temperature of 40°C.

Description

Technical Field

[0001] The present invention relates to the field of chlorine dioxide products and preparation methods, and particularly relates to a preparation method of a chlorine dioxide aqueous solution with stable concentration. Background Art

[0002] Chlorine dioxide is an environmental disinfectant recommended by the World Health Organization as the fourth generation, and is also a disinfectant rated by the Food and Agriculture Organization of the United Nations as having a safety level of A1 (the same safety level as sugar and salt). Chlorine dioxide has the functions of sterilization, bleaching, deodorization, disinfection, and preservation, and can be used for disinfection, mold prevention, and food preservation of food, food processing, pharmaceuticals, hospitals, public environments, etc.

[0003] Chlorine dioxide is highly soluble in water to form a chlorine dioxide aqueous solution, which can be applied to bleaching, disinfection, and deodorization, especially in water treatment technology. Due to the extremely unstable chemical properties of chlorine dioxide, chlorine dioxide gas is easily released from the solution. A 1000 ppm chlorine dioxide aqueous solution will completely disappear within a few months when stored in an incompletely sealed container, which greatly affects the application of the chlorine dioxide aqueous solution. Summary of the Invention

[0004] Based on the problems existing in the background art, the present invention provides a preparation method of a chlorine dioxide aqueous solution with stable concentration. The chlorine dioxide aqueous solution prepared by the present invention has high purity and stable concentration, and can still maintain the stable concentration of chlorine dioxide at a high temperature of 40°C.

[0005] The present invention is implemented through the following technical solutions:

[0006] A preparation method of a chlorine dioxide aqueous solution with stable concentration, comprising the following steps:

[0007] Step 1: Add sodium chlorate solution and sodium chlorite solution to a reaction kettle, mix evenly to obtain a mixed solution A;

[0008] Step 2: Add a composite reducing agent and a catalyst to the reaction kettle, mix evenly to obtain a mixed solution B;

[0009] Step 3: Slowly add concentrated sulfuric acid to the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0010] Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain a chlorine dioxide aqueous solution with stable concentration.

[0011] The main reactions for generating chlorine dioxide gas in the present invention are:

[0012] C 12 H 22 O 11+48NaClO3 + 25H2SO4 → 48ClO2 + 12CO2 + 35H2O + 24Na2SO4

[0013] C 12 H 22 O 11 +H2O → C6H 12 O6 (glucose) + C6H 12 O6 (fructose)

[0014] C6H 12 O6 + 24NaClO3 + 12H2SO4 → 24ClO2 + 6CO2 + 18H2O + 12Na2SO4

[0015] 2NaClO3 + H2C2O4 + 2H2SO4 → 2ClO2 + CO2 + 2NaHSO4 + 2H2O

[0016] 5NaClO2 + 2H2SO4 → 4ClO2 + 2Na2SO4 + NaCl + 2H2O

[0017] NaClO2 + 2H2O + 4CO2 → 4ClO2 + 4NaHCO3 + NaCl

[0018] Furthermore, in step 1, the concentration of the sodium chlorate solution is 0.4 - 0.6 mol / L, the concentration of the sodium chlorite solution is 0.2 - 0.5 mol / L, and the mass ratio of the sodium chlorate solution to the sodium chlorite solution is 1:(0.1 - 0.4).

[0019] Furthermore, in step 2, the composite reducing agent is a mixture of oxalic acid and sucrose.

[0020] Furthermore, the mass ratio of the oxalic acid to the sucrose is 1:(2 - 5).

[0021] Furthermore, the addition amount of the composite reducing agent is 5 - 10% of the weight of the sodium chlorate and sodium chlorite.

[0022] Furthermore, in step 2, the catalyst is ferric chloride.

[0023] Furthermore, in step 3, the dropping rate of the concentrated sulfuric acid is 10 - 15 mL / min.

[0024] Furthermore, in step 3, the reaction temperature is 60 - 80 °C.

[0025] Furthermore, in step 4, the temperature of the condenser is 4 - 10 °C.

[0026] Further, in step 4, the absorbent liquid in the tertiary absorption tower is an alkaline solution added with a stabilizer, where the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate to carboxymethyl cellulose is 1:(0.1 - 0.3).

[0027] Further, the reaction kettle controls the reaction temperature through an automatic temperature control system, and the automatic temperature control system includes a temperature adjustment module, a temperature detection module, and an information processing module;

[0028] Among them, the temperature detection module includes a temperature sensor, and the temperature sensor transmits the temperature of the reaction kettle detected in real time to the information processing module.

[0029] The temperature adjustment module includes a PTC heating system and a thermoelectric cooler cooling system.

[0030] Turn on the control button and set the working temperature of the reaction kettle. The system control algorithm is as follows:

[0031]

[0032] Among them, t is the sampling period of the control system, w(t) is the output result, y(t) is the input deviation, and δ, γ, λ are the three parameters of the control system, which are 10.393, 12.451, and 2.282 respectively.

[0033] The sensor in the temperature detection module transmits the temperature of the reaction kettle detected in real time to the information processing module. The information processing module calculates and processes the temperature signal, transmits the result to the temperature adjustment module, starts the control algorithm program, and controls the heating system or the cooling system according to the result, so as to accurately control the temperature of the mold.

[0034] Advantages of the present invention:

[0035] 1. In the present invention, the raw material of chlorine dioxide gas is a mixed solution of sodium chlorate and sodium chlorite, and a composite reducing agent is used, which significantly improves the conversion rate of chlorine dioxide compared with traditional single reducing agents, has high raw material utilization rate, and reduces production costs.

[0036] 2. In the present invention, sodium chlorate reacts with the composite reducing agent to generate chlorine dioxide and by-product carbon dioxide. Carbon dioxide can continue to react with sodium chlorite, reducing carbon dioxide emissions, achieving pollution source control, and conforming to the concept of green development.

[0037] 3. In the present invention, a stabilizer is added to the aqueous chlorine dioxide solution, so that the concentration of chlorine dioxide in the aqueous chlorine dioxide solution can still be kept stable at a high temperature of 40°C. Specific embodiments

[0038] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0039] Example 1

[0040] A method for preparing a chlorine dioxide aqueous solution with stable concentration, comprising the following steps:

[0041] Step 1: Add sodium chlorate solution and sodium chlorite solution into a reaction kettle, mix evenly to obtain a mixed solution A;

[0042] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.35 L;

[0043] Step 2: Add a composite reducing agent and a catalyst into the reaction kettle, mix evenly to obtain a mixed solution B;

[0044] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose, the dosage of oxalic acid is 1 g, and the dosage of sucrose is 3.5 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1 g;

[0045] Step 3: Slowly add concentrated sulfuric acid into the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle at 70 °C. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0046] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0047] Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain a chlorine dioxide aqueous solution with stable concentration.

[0048] Among them, the temperature of the condenser is 4 °C, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer, the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate, carboxymethyl cellulose and water is 1:0.2:500.

[0049] After detection, the conversion rate of the raw materials is 98.6%, and the purity of chlorine dioxide in the chlorine dioxide aqueous solution is 99.5%.

[0050] Example 2

[0051] A method for preparing a chlorine dioxide aqueous solution with stable concentration, comprising the following steps:

[0052] Step 1: Add sodium chlorate solution and sodium chlorite solution into a reaction kettle, mix evenly to obtain a mixed solution A;

[0053] Among them, the concentration of sodium chlorate is 0.6 mol / L, the concentration of sodium chlorite is 0.3 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.24 L;

[0054] Step 2: Add the composite reducing agent and the catalyst into the reactor, mix evenly to obtain the mixed solution B;

[0055] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose. The dosage of oxalic acid is 1.2 g, and the dosage of sucrose is 4.1 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1.2 g;

[0056] Step 3: Slowly add concentrated sulfuric acid into the reactor, start the vacuum system, and control the temperature of the reactor at 70 °C. The reaction starts in the reactor to produce chlorine dioxide gas;

[0057] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 36 mL, and the dropping rate is 10 mL / min;

[0058] Step 4: Pass the chlorine dioxide gas through the condenser, and after passing through the separator, it is absorbed by the three-stage absorption tower to obtain a chlorine dioxide aqueous solution with a stable concentration.

[0059] Among them, the temperature of the condenser is 4 °C, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer. The stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate, carboxymethyl cellulose and water is 1:0.2:500.

[0060] After detection, the conversion rate of the raw materials is 98.8%, and the purity of chlorine dioxide in the chlorine dioxide aqueous solution is 99.6%.

[0061] Example 3

[0062] A preparation method of a chlorine dioxide aqueous solution with a stable concentration, comprising the following steps:

[0063] Step 1: Add the sodium chlorate solution and the sodium chlorite solution into the reactor, mix evenly to obtain the mixed solution A;

[0064] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of the sodium chlorate solution is 1 L, and the dosage of the sodium chlorite solution is 0.35 L;

[0065] Step 2: Add the composite reducing agent and the catalyst into the reactor, mix evenly to obtain the mixed solution B;

[0066] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose. The dosage of oxalic acid is 1 g, and the dosage of sucrose is 3.5 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1 g;

[0067] Step 3: Slowly add concentrated sulfuric acid into the reactor, start the vacuum system, and control the temperature of the reactor at 70 °C. The reaction starts in the reactor to produce chlorine dioxide gas;

[0068] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0069] Step 4: Pass the chlorine dioxide gas through a condenser, and then through a separator to a three-stage absorption tower for absorption to obtain a chlorine dioxide aqueous solution with a stable concentration.

[0070] Among them, the temperature of the condenser is 4°C, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer, the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate, carboxymethyl cellulose and water is 1:0.3:500.

[0071] After detection, the conversion rate of the raw materials is 98.4%, and the purity of chlorine dioxide in the chlorine dioxide aqueous solution is 99.5%.

[0072] Comparative Example 1

[0073] A method for preparing a chlorine dioxide aqueous solution with a stable concentration, comprising the following steps:

[0074] Step 1: Add sodium chlorate solution and sodium chlorite solution to a reaction kettle, mix evenly to obtain a mixed solution A;

[0075] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.35 L;

[0076] Step 2: Add a reducing agent and a catalyst to the reaction kettle, mix evenly to obtain a mixed solution B;

[0077] Among them, the reducing agent is sucrose, and the dosage of sucrose is 5 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1.2 g;

[0078] Step 3: Slowly add concentrated sulfuric acid to the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle at 70°C. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0079] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0080] Step 4: Pass the chlorine dioxide gas through a condenser, and then through a separator to a three-stage absorption tower for absorption to obtain a chlorine dioxide aqueous solution.

[0081] Among them, the temperature of the condenser is 4°C, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer, the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate, carboxymethyl cellulose and water is 1:0.2:500.

[0082] After detection, the conversion rate of the raw materials is 94.2%, and the purity of chlorine dioxide in the aqueous chlorine dioxide solution is 99.2%.

[0083] Comparative Example 2

[0084] A method for preparing an aqueous chlorine dioxide solution with stable concentration, comprising the following steps:

[0085] Step 1: Add sodium chlorate solution and sodium chlorite solution into the reaction kettle, mix evenly to obtain mixture A;

[0086] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.35 L;

[0087] Step 2: Add a composite reducing agent into the reaction kettle, mix evenly to obtain mixture B;

[0088] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose, the dosage of oxalic acid is 1 g, and the dosage of sucrose is 3.5 g;

[0089] Step 3: Slowly add concentrated sulfuric acid into the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle at 70 °C. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0090] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0091] Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain an aqueous chlorine dioxide solution.

[0092] Among them, the temperature of the condenser is 4 °C, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer, the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of sodium carbonate, carboxymethyl cellulose and water is 1:0.2:500.

[0093] After detection, the conversion rate of the raw materials is 90.3%, and the purity of chlorine dioxide in the aqueous chlorine dioxide solution is 99.0%.

[0094] Comparative Example 3

[0095] A method for preparing an aqueous chlorine dioxide solution with stable concentration, comprising the following steps:

[0096] Step 1: Add sodium chlorate solution and sodium chlorite solution into the reaction kettle, mix evenly to obtain mixture A;

[0097] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.35 L;

[0098] Step 2: Add a composite reducing agent and a catalyst to the reaction kettle, mix evenly to obtain a mixed solution B;

[0099] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose, the dosage of oxalic acid is 1 g, and the dosage of sucrose is 3.5 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1 g;

[0100] Step 3: Slowly add concentrated sulfuric acid to the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle at 70 °C. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0101] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0102] Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain an aqueous chlorine dioxide solution.

[0103] Among them, the temperature of the condenser is 4 °C, and the absorption liquid in the three-stage absorption tower is pure water.

[0104] After testing, the conversion rate of the raw materials is 98.3%, and the purity of chlorine dioxide in the aqueous chlorine dioxide solution is 99.6%.

[0105] Comparative Example 4

[0106] A method for preparing an aqueous chlorine dioxide solution with stable concentration, comprising the following steps:

[0107] Step 1: Add a sodium chlorate solution and a sodium chlorite solution to the reaction kettle, mix evenly to obtain a mixed solution A;

[0108] Among them, the concentration of sodium chlorate is 0.5 mol / L, the concentration of sodium chlorite is 0.2 mol / L, the dosage of sodium chlorate solution is 1 L, and the dosage of sodium chlorite solution is 0.35 L;

[0109] Step 2: Add a composite reducing agent and a catalyst to the reaction kettle, mix evenly to obtain a mixed solution B;

[0110] Among them, the composite reducing agent is a mixture of oxalic acid and sucrose, the dosage of oxalic acid is 1 g, and the dosage of sucrose is 3.5 g; the catalyst is ferric chloride, and the dosage of ferric chloride is 1 g;

[0111] Step 3: Slowly add concentrated sulfuric acid to the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle at 70 °C. The reaction starts in the reaction kettle to generate chlorine dioxide gas;

[0112] Among them, the concentrated sulfuric acid is 98% sulfuric acid, the dropping amount is 30 mL, and the dropping rate is 10 mL / min;

[0113] Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain an aqueous chlorine dioxide solution.

[0114] Among them, the temperature of the condenser is 4°C, the absorption liquid in the three-stage absorption tower is a sodium carbonate solution, and the mass ratio of sodium carbonate to water is 1:500.

[0115] After detection, the conversion rate of the raw materials is 98.4%, and the purity of chlorine dioxide in the aqueous chlorine dioxide solution is 99.3%.

[0116] Test Example

[0117] Place the chlorine dioxide solutions prepared in Examples 1-3 and Comparative Examples 1-4 in an oven at 40°C for 90 days, and record the chlorine dioxide content before (day 0) and after (day 90) placing the samples. The specific results are shown in Table 1.

[0118] Table 1

[0119] Group mg / L before placement mg / L after placement Chlorine dioxide decline rate % Example 1 2053.3 2003.4 2.4 Example 2 2157.9 2043.6 5.3 Example 3 2006.8 1943.0 3.2 Comparative Example 1 1852.4 1743.5 5.9 Comparative Example 2 1626.1 1586.9 2.4 Comparative Example 3 2014.5 1134.7 43.7 Comparative Example 4 2036.7 1534.6 24.7

[0120] It can be seen from the experimental results in Table 1 that for the chlorine dioxide solution prepared by the present invention at 40°C, the decline rate of the chlorine dioxide content is 2.4 - 5.3%, meeting the requirement that the decline rate of the active ingredient content in the accelerated test is less than 10%, and the shelf life of the chlorine dioxide solution can reach two years. In Comparative Example 3, the absorption liquid is pure water, and the volatilization rate of chlorine dioxide is fast at 40°C. After 90 days, the content of chlorine dioxide remains only 56.3%. In Comparative Example 4, sodium carbonate is added to the absorption liquid, which effectively improves the stability of the chlorine dioxide solution compared with Comparative Example 3. However, after being stored at 40°C for 90 days, the chlorine dioxide content decreases by 24.7%, which is significantly higher than that of Examples 1-3.

[0121] Example 4

[0122] The reaction kettle controls the reaction temperature through an automatic temperature control system, and the automatic temperature control system includes a temperature adjustment module, a temperature detection module, and an information processing module;

[0123] Among them, the temperature detection module includes a temperature sensor, and the temperature sensor transmits the reaction kettle temperature detected in real time to the information processing module.

[0124] The temperature adjustment module includes a PTC heating system and a thermoelectric cooler cooling system.

[0125] Turn on the control button and set the working temperature of the reaction kettle. Its system control algorithm is as follows:

[0126]

[0127] Among them, t is the sampling period of the control system, w(t) is the output result, y(t) is the input deviation, and δ, γ, and λ are the three parameters of the control system, which are 10.393, 12.451, and 2.282 respectively.

[0128] The sensor in the temperature detection module transmits the temperature of the reaction kettle detected in real time to the information processing module. The information processing module calculates and processes the temperature signal, transmits the result to the temperature adjustment module, and the control algorithm program starts to control the heating system or the cooling system according to the result, so as to accurately control the temperature of the mold.

[0129] In the present invention, solid heating and solid cooling elements are adopted, which reduces the transition time of temperature adjustment and improves the efficiency. And through the control of the automatic program, the accuracy of the temperature adjustment of the reaction kettle is improved.

[0130] Finally, it should be noted that the above embodiments only represent several implementation manners of the present invention and are not intended to limit the present invention. For those of ordinary skill in the art, any modifications, equivalent replacements, improvements, etc. made without departing from the concept of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for preparing an aqueous solution of chlorine dioxide with stable concentration, characterized in that, It includes the following steps: Step 1: Add sodium chlorate solution and sodium chlorite solution into the reaction kettle, mix evenly to obtain mixture A; Step 2: Add a composite reducing agent and a catalyst into the reaction kettle, mix evenly to obtain mixture B; Step 3: Slowly add concentrated sulfuric acid into the reaction kettle, start the vacuum system, and control the temperature of the reaction kettle. The reaction starts in the reaction kettle to produce chlorine dioxide gas; Step 4: Pass the chlorine dioxide gas through a condenser, and after passing through a separator, absorb it in a three-stage absorption tower to obtain a chlorine dioxide aqueous solution with a stable concentration; In Step 1, the concentration of the sodium chlorate solution is 0.4 - 0.6 mol / L, the concentration of the sodium chlorite solution is 0.2 - 0.5 mol / L, and the mass ratio of the sodium chlorate solution to the sodium chlorite solution is 1:(0.1 - 0.4); In Step 2, the composite reducing agent is a mixture of oxalic acid and sucrose, and the mass ratio of the oxalic acid to the sucrose is 1:(2 - 5); In Step 4, the absorption liquid in the three-stage absorption tower is an alkaline solution added with a stabilizer, and the stabilizer is a mixed solution of sodium carbonate and carboxymethyl cellulose, and the mass ratio of the sodium carbonate to the carboxymethyl cellulose is 1:(0.1 - 0.3).

2. The method for preparing an aqueous solution of chlorine dioxide with stable concentration according to claim 1, characterized in that, The addition amount of the composite reducing agent is 5 - 10% of the weight of sodium chlorate and sodium chlorite.

3. The method for preparing an aqueous solution of chlorine dioxide with stable concentration according to claim 1, characterized in that, In Step 2, the catalyst is ferric chloride.

4. The method for preparing an aqueous solution of chlorine dioxide with stable concentration according to claim 1, characterized in that, In Step 3, the dropping rate of the concentrated sulfuric acid is 10 - 15 mL / min.

5. The method for preparing an aqueous solution of chlorine dioxide with stable concentration according to claim 1, characterized in that, In Step 3, the reaction temperature is 60 - 80 °C.

6. The method for preparing an aqueous solution of chlorine dioxide with stable concentration according to claim 1, characterized in that, In Step 4, the temperature of the condenser is 4 - 10 °C.

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