Chlorine dioxide releasing agent with low corrosiveness and flocculation function and preparation method thereof

Abstract

This invention belongs to the field of water treatment and disinfection technology, specifically relating to a chlorine dioxide releasing agent with both low corrosivity and flocculation functions, and its preparation method. The chlorine dioxide releasing agent is composed of the following raw materials in the indicated mass percentages: potassium ferrate 8-12%, sodium chlorite 16-22%, organic acid 15-23%, iron salt 12-14%, peroxide donor 10-20%, succinic acid 6-12%, with the balance being a desiccant. The activated solution of the chlorine dioxide releasing agent obtained by this invention has a near-neutral pH value, solving the problem of excessively low pH and strong corrosion in existing chlorine dioxide releasing tablets; it also effectively improves the conversion rate of sodium chlorite and the purity of chlorine dioxide. Furthermore, this releasing agent has dual functions of disinfection and flocculation of clean water, not only improving disinfection efficiency but also significantly reducing production costs.

Description

Technical Field

[0001] This invention belongs to the field of water treatment and disinfection technology, specifically relating to a chlorine dioxide releasing agent with both low corrosiveness and flocculation function and its preparation method. Background Technology

[0002] Chlorine dioxide is a widely used and highly effective disinfectant that can effectively kill various viruses, bacteria, and other pathogenic microorganisms. It is also suitable for a wider pH range, is unaffected by ammonia nitrogen, and produces virtually no organohalogenated compounds. Furthermore, it can degrade hydrogen sulfide, methanethiol, cyanide, and many other harmful pollutants. Currently, it is widely used in drinking water disinfection, sanitation disinfection, epidemic prevention and emergency response, air purification, aquaculture, and soil disinfection.

[0003] Because chlorine dioxide molecules cannot be compressed for storage and transportation, precursors such as sodium chlorite and solid acids are often compounded with desiccants and other excipients. These are then mixed and compressed into powder or tablet form of a solid chlorine dioxide release agent, which reacts with water to produce a chlorine dioxide disinfectant solution. Many formulations add excessive amounts of solid acids such as sodium bisulfate to increase the conversion rate of chlorite, resulting in a low pH (even pH < 2) in the compounded chlorine dioxide disinfectant solution, causing severe environmental corrosion. Summary of the Invention

[0004] One of the objectives of this invention is to provide a chlorine dioxide release agent that combines low corrosivity with flocculation function.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A chlorine dioxide release agent with both low corrosiveness and flocculation function is composed of the following raw materials in the following mass percentages: potassium ferrate 8-12%, sodium chlorite 16-22%, organic acid 15-23%, iron salt 12-14%, peroxide donor 10-20%, succinic acid 6-12%, and the balance being a desiccant.

[0007] The organic acid is at least one of tartaric acid, citric acid, malic acid, glycolic acid, and hydroxybutyric acid; the iron salt is at least one of ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate; and the peroxide donor is a sodium chloride-sodium sulfate-hydrogen peroxide adduct.

[0008] The sodium chlorite is a precursor of chlorine dioxide; the succinic acid is a synergist.

[0009] The organic acid is a mixture of tartaric acid, citric acid, malic acid, glycolic acid, and hydroxybutyric acid in any proportion; the iron salt is a mixture of ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate in any proportion; and the desiccant is a mixture of anhydrous sodium sulfate and magnesium sulfate in any proportion.

[0010] Further, the organic acid is obtained by mixing tartaric acid and hydroxybutyric acid in a mass ratio of 1:(1-2), or by mixing tartaric acid, citric acid and hydroxybutyric acid in a mass ratio of 2:(3-4):(8-10), or by mixing malic acid, citric acid and glycolic acid in a mass ratio of 8:(3-5):(8-10).

[0011] Furthermore, the organic acid is obtained by mixing tartaric acid and hydroxybutyric acid in a mass ratio of 1:1, or by mixing tartaric acid, citric acid, and hydroxybutyric acid in a mass ratio of 2:3:10, or by mixing malic acid, citric acid, and glycolic acid in a mass ratio of 8:5:10.

[0012] Tartaric acid: a dicarboxylic acid with a molecular weight of 150.09 g / mol. pKa1 = 3.04, pKa2 = 4.37; Hydroxybutyric acid: molecular weight of 104.11 g / mol. pKa ≈ 4.70.

[0013] When the organic acids tartaric acid and hydroxybutyric acid are in a 1:1 mass ratio, the pH of the reaction system is approximately 3.5-3.8. However, the two pKa values ​​of tartaric acid and one pKa value of hydroxybutyric acid cover a continuous pH range, preventing sudden pH changes. This means that the system has a buffering effect within the range of approximately 3.0 to 4.7. Around pH 3.0-3.5, the buffering is primarily provided by the first pKa of tartaric acid; around pH 3.5-4.5, the second pKa of tartaric acid and the pKa of hydroxybutyric acid work together to form an overlapping, ultra-strong buffer zone. Therefore, the system can stably maintain this pH range. This suitable pH environment not only ensures the stability of hydrogen peroxide and prolongs its effectiveness but also avoids corrosion problems caused by excessively low pH. Furthermore, it optimizes the generation efficiency of chlorine dioxide, preventing conversion loss due to excessively high pH.

[0014] Furthermore, the iron salt is obtained by mixing ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate in a mass ratio of (0-4):(1-12).

[0015] Furthermore, the iron salt is obtained by mixing ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate in a mass ratio of 4:3.

[0016] Furthermore, the desiccant is a mixture of anhydrous sodium sulfate and magnesium sulfate in a mass ratio of (4-7):(5-12).

[0017] Furthermore, the preparation method of the sodium chloride-sodium sulfate-hydrogen peroxide adduct is as follows:

[0018] A 30wt% sodium sulfate aqueous solution, a 30wt% sodium chloride aqueous solution, and a 30wt% hydrogen peroxide solution were mixed in a volume ratio of 1:1:1 and reacted at 5-10℃ for 20-40s. The reaction solution was then cooled at -5℃ to crystallize, filtered, and dried to obtain a sodium chloride-sodium sulfate-hydrogen peroxide adduct.

[0019] Potassium ferrate reacts with sodium chlorite under neutral conditions to produce Fe. 3+ Organic acids and Fe 3+ A redox cycle occurs.

[0020] 1) Hydrogen peroxide adducts release a small amount of ·OH;

[0021] 2) ·OH removes hydrogen from the carbon atom bonded to the hydroxyl group in an organic acid molecule, forming a carbon free radical;

[0022] 3) Carbon free radicals will... 3+ Reduced to Fe 2+ At the same time, superoxide anions (O3) are generated. 2- ·), O 2- Further reduction of Fe 3+ Fe 2+ This enables the recycling of iron ions;

[0023] 4) The synergists succinic acid and sodium iron ethylenediaminetetraacetate (EDTA sodium iron) can complex Fe through carboxyl groups. 3+ This indirectly enhances the decomposition efficiency of H2O2, that is, increases the efficiency of hydrogen peroxide adducts in releasing ·OH, and improves the stability of hydrogen peroxide.

[0024] 5) ·OH oxidizes chloride ions to form hypochlorous acid;

[0025] 6) Hypochlorous acid and sodium chlorite react to produce chlorine dioxide. Chlorine dioxide has a disinfecting effect, and the Fe produced in the reaction... 3+ It has a flocculation effect.

[0026] This invention selects ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate as iron salts. These iron salts can act as buffers, and at the same time, they can remove the influence of other transition metals through complexation.

[0027] This invention uses a sodium chloride-sodium sulfate-hydrogen peroxide adduct as a peroxide donor, which has a high active oxygen content and low raw material cost.

[0028] In addition to providing protons to activate sodium chlorite to generate chlorine dioxide, the synergist succinic acid of this invention also has a complexing effect, allowing iron and other transition metals to exist in a complexed state without affecting the stability of hydrogen peroxide.

[0029] The second objective of this invention is to provide a method for preparing a chlorine dioxide releasing agent that combines low corrosivity and flocculation function.

[0030] To achieve the above objectives, the present invention adopts the following technical solution:

[0031] The present invention provides a method for preparing a chlorine dioxide release agent that combines low corrosivity and flocculation functions, comprising the following steps: mixing potassium permanganate, sodium chlorite and desiccant according to the stated mass percentages, then adding succinic acid, iron salt and organic acid for further mixing, and finally adding a peroxide donor for further mixing to obtain powder or tablets.

[0032] Furthermore, the mixing time is ≥15 min.

[0033] Furthermore, mixing can be performed using a V-type mixer, a square cone mixer, or a three-dimensional mixer.

[0034] Furthermore, during tablet preparation, a release agent is added simultaneously with the peroxide donor; the release agent is PEG4000 or PEG6000.

[0035] Furthermore, the amount of the release agent is 1-5% of the total mass of all raw materials.

[0036] The tablets and powders obtained by this invention should be packaged in double-layer aluminum foil bags, with the aluminum foil lined with PP film.

[0037] Compared with the prior art, the beneficial effects of this invention are as follows:

[0038] 1. This invention provides a chlorine dioxide releasing agent that combines low corrosivity and flocculation function. This chlorine dioxide releasing agent generates chlorine dioxide through two methods: direct oxidation with potassium ferrate and catalytic oxidation of sodium chlorite with hydroxyl radicals. It does not require the use of strong or medium-strong acids, and the pH value of the activated solution is stable within a suitable range. This solves the problems of excessively low pH and excessive corrosivity of existing chlorine dioxide releasing agents.

[0039] 2. The chlorine dioxide releasing agent provided by this invention has both low corrosivity and flocculation function, and has a high sodium chlorite conversion rate, which can reach more than 90%, thus reducing the production cost of the product; it solves the problems of slow reaction speed and low conversion rate of neutral formulations in traditional methods.

[0040] 3. The chlorine dioxide releasing agent provided by this invention, which combines low corrosivity and flocculation function, contains more free radicals and has dual functions of disinfection and flocculation of water, with a disinfection effect superior to similar chlorine dioxide releasing agents.

[0041] 4. The chlorine dioxide releasing agent provided by this invention has both low corrosivity and flocculation function, with a high chlorine dioxide content that can be adjusted within the range of 5% to 15%.

[0042] 5. Traditional neutral formulations are expensive, generally costing over 20,000 yuan per ton; however, the chlorine dioxide release agent provided by this invention, which combines low corrosivity and flocculation functions, uses hydrogen peroxide solid adducts, which are inexpensive, with a price of approximately 5,000-8,000 yuan per ton of powder. The raw material cost of the product is similar to that of traditional sodium bisulfate formulations, greatly reducing production costs. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the working principle of the chlorine dioxide releasing agent of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be further explained below with reference to specific embodiments, comparative examples, experimental examples and accompanying drawings.

[0045] Unless otherwise specified, the raw materials and preparation methods used in the following examples, comparative examples, and experimental cases are all conventional materials and techniques in the art.

[0046] The preparation method of the sodium chloride-sodium sulfate-hydrogen peroxide adduct of the present invention is as follows:

[0047] (1) Dissolve sodium sulfate (analytical grade ≥99.5%) in deionized water to prepare a sodium sulfate aqueous solution with a concentration of 30wt%. Dissolve sodium chloride (analytical grade ≥99.5%) in deionized water to prepare a sodium chloride aqueous solution with a concentration of 30%w / w. Hydrogen peroxide (industrial grade 30wt%, purchased from Tianjin Damao Chemical Reagent Factory).

[0048] (2) The sodium sulfate aqueous solution, sodium chloride aqueous solution, and hydrogen peroxide described in step (1) are fed into the microchannel reactor at a volume ratio of 1:1:1 using a high-precision metering pump, and reacted at 5°C for 30 seconds. Low temperature can significantly inhibit the decomposition of H2O2 and improve the solid yield. The microchannel reactor is equipped with an external cooling jacket, and the reaction temperature is maintained by real-time monitoring via built-in thermocouples to ensure that the temperature fluctuation is <1°C.

[0049] (3) The reacted solution is introduced into a low-temperature condenser (-5℃) to immediately lower the temperature and promote solid crystallization. The solution is filtered using a microporous membrane (0.5µm), and the filtered solid is directly introduced into a vacuum drying chamber (35℃, 30min) to obtain white crystalline powder, which is the sodium chloride-sodium sulfate-hydrogen peroxide adduct. The filtered liquid (containing unreacted H2O2, Na2SO4, and NaCl) is monitored for online concentration (UV-Vis), and H2O2 is added proportionally before being reintroduced into the microchannel for recycling.

[0050] The organic acid described in this invention is at least one selected from tartaric acid, citric acid, malic acid, glycolic acid, and hydroxybutyric acid; the iron salt is at least one selected from ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate; the peroxide donor is a sodium chloride-sodium sulfate-hydrogen peroxide adduct. The desiccant is anhydrous sodium sulfate and magnesium sulfate.

[0051] Example 1

[0052] A chlorine dioxide releasing agent with both low corrosiveness and flocculation function is composed of the following raw materials in the following mass percentages: potassium ferrate 10%; sodium chlorite 18%; tartaric acid 10%; hydroxybutyric acid 10%; ferric ammonium citrate 8%; ferric sodium ethylenediaminetetraacetate (EDTA ferric sodium) 6%; sodium chloride-sodium sulfate-hydrogen peroxide adduct 15%; succinic acid 6%; anhydrous sodium sulfate 7%; and magnesium sulfate 10%.

[0053] This embodiment 1 also provides a method for preparing a chlorine dioxide releasing agent that combines low corrosivity and flocculation functions, including the following steps: A schematic diagram of the reaction mechanism of the chlorine dioxide releasing agent is shown below. Figure 1 As shown;

[0054] According to the stated mass percentages, potassium ferrate, sodium chlorite, and desiccant (anhydrous sodium sulfate, magnesium sulfate) are first mixed, then succinic acid, iron salts (ferric ammonium citrate, ferric sodium EDTA), and organic acids (tartaric acid, hydroxybutyric acid) are added and mixed, then sodium chloride-sodium sulfate-hydrogen peroxide adduct and release agent (PEG4000) are added and mixed. The amount of release agent is 3% of the total mass of each raw material. The mixing time is 30 minutes. After the above materials are mixed evenly, tablets are obtained by using a tableting machine.

[0055] Example 2

[0056] A chlorine dioxide releasing agent with both low corrosiveness and flocculation function is composed of the following raw materials in the following mass percentages: potassium ferrate 8%; sodium chlorite 16%; tartaric acid 2%; citric acid 3%; hydroxybutyric acid 10%; ferric ammonium citrate 6%; EDTA iron sodium 6%; sodium chloride-sodium sulfate-hydrogen peroxide adduct 20%; succinic acid 10%; anhydrous sodium sulfate 7%; and magnesium sulfate 12%.

[0057] This embodiment 2 also provides a method for preparing a chlorine dioxide releasing agent that combines low corrosivity and flocculation function, comprising the following steps: according to the stated mass percentage, first mix potassium ferrate, sodium chlorite and desiccant (anhydrous sodium sulfate, magnesium sulfate), then add succinic acid, iron salt (ferric ammonium citrate, EDTA iron sodium) and organic acid (tartaric acid, citric acid, hydroxybutyric acid) and mix, and finally add sodium chloride-sodium sulfate-hydrogen peroxide adduct and mix for 30 min; thus obtaining the powder.

[0058] Example 3

[0059] A chlorine dioxide releasing agent with both low corrosiveness and flocculation function is composed of the following raw materials in the following mass percentages: potassium ferrate 12%; sodium chlorite 22%; malic acid 8%, citric acid 5%, glycolic acid 10%; EDTA iron sodium 12%; sodium chloride-sodium sulfate-hydrogen peroxide adduct 10%; succinic acid 12%; anhydrous sodium sulfate 4%; magnesium sulfate 5%.

[0060] This embodiment 3 also provides a method for preparing a chlorine dioxide releasing agent that has both low corrosivity and flocculation function, including the following steps: according to the said mass percentage, first mix potassium ferrate, sodium chlorite and desiccant (anhydrous sodium sulfate, magnesium sulfate), then add succinic acid, EDTA sodium iron and organic acid (malic acid, citric acid, glycolic acid) and mix, and finally add sodium chloride-sodium sulfate-hydrogen peroxide adduct and mix for 30 minutes to obtain powder.

[0061] Comparative Example 1

[0062] Comparative Example 1 is basically the same as Example 1, except that the addition of iron salts (ferric ammonium citrate, EDTA iron sodium) is omitted, and the amount of anhydrous sodium sulfate is changed to 21%. Otherwise, it is consistent with Example 1.

[0063] Comparative Example 2

[0064] Comparative Example 2 is basically the same as Example 1, except that tartaric acid is replaced with sodium bisulfate, while the rest is the same as Example 1.

[0065] Comparative Example 3

[0066] Comparative Example 3 is basically the same as Example 1, except that the sodium chloride-sodium sulfate-hydrogen peroxide adduct is replaced with sodium percarbonate, while the rest is the same as Example 1.

[0067] Comparative Example 4

[0068] Comparative Example 4 is basically the same as Example 1, except that succinic acid is replaced with tartaric acid, while the rest is the same as Example 1.

[0069] Test case

[0070] To test the performance of the products obtained in Examples 1-3 and Comparative Examples 1-4 of this invention, the chlorine dioxide releasing agents obtained in Examples 1-3 and Comparative Examples 1-4 were activated with water for 30 minutes at a ratio of 1g chlorine dioxide releasing agent to 100mL water to prepare a disinfectant solution.

[0071] 1. The chlorine dioxide content of the products obtained in Examples 1-3 and Comparative Examples 1-4 was determined according to Appendix A.2 of GB / T 26366-2021 "Hygienic Requirements for Chlorine Dioxide Disinfectants" using the five-step iodometric method;

[0072] 2. The conversion rate of sodium chlorite is calculated according to the following formula: Sodium chlorite conversion rate = (chlorine dioxide content measured per gram of sample × 1.34 / sodium chlorite added per gram of sample) × 100%.

[0073] 3. The pH values ​​of the disinfectant solutions obtained in Examples 1-3 and Comparative Examples 1-4 were measured using a PHS-25 pH meter;

[0074] 4. The disinfectant solutions obtained in Examples 1-3 and Comparative Examples 1-4 were used to treat 1 NTU of simulated wastewater prepared with activated carbon. The solution was used to treat the wastewater for 30 minutes at 100 r / min with a stirrer. The turbidity values ​​before and after treatment were measured with a turbidity meter. The turbidity removal rate was calculated according to the following formula: Turbidity removal rate = (turbidity before treatment - turbidity after removal) / turbidity before treatment × 100%.

[0075] 5. Corrosion was evaluated based on the corrosion rate, which was determined according to the full immersion corrosion test method in GB / T 38498-2020 "Evaluation Method for Corrosion of Metals in Disinfectants". The experimental results are recorded in Table 1.

[0076] Table 1

[0077]

[0078] As shown in Table 1, the chlorine dioxide releasing agents obtained in Examples 1-3 of this invention can ensure a high sodium chlorite conversion rate. The conversion rates of the chlorine dioxide releasing agents of all three examples are above 90%, and the pH value after activation is close to neutral. The purity of chlorine dioxide is maintained above 95%. Among them, the turbidity removal rate of the product obtained in Example 1 is as high as 56%.

[0079] Compared with Examples 1-3, the sodium chlorite conversion rate, chlorine dioxide purity, and turbidity removal rate of Comparative Examples 1-4 were relatively poor. Among them, the sodium chlorite conversion rate of Comparative Example 1 showed a particularly significant downward trend. The specific reason is that, lacking iron as a catalyst, only a small amount of weak acid could activate part of the sodium chlorite; the reaction would be significantly slowed down, and it would be impossible to convert all the sodium chlorite into chlorine dioxide.

[0080] In Comparative Example 2, when tartaric acid was replaced with sodium bisulfate, the pH value of the disinfectant dropped sharply. The specific reason is that although sodium percarbonate can activate some sodium chlorite to generate chlorine dioxide, it greatly reduces the pH value of the system, thus increasing the corrosiveness of the entire product.

[0081] In Comparative Example 3, when the sodium chloride-sodium sulfate-hydrogen peroxide adduct was replaced with sodium percarbonate, the conversion rate of sodium chlorite decreased significantly. The specific reason for this was that the conversion rate of sodium chlorite decreased greatly due to the lack of peroxide.

[0082] In Comparative Example 4, succinic acid was replaced with tartaric acid. Due to the lack of succinic acid, the stability of hydrogen peroxide decreased, which led to a decrease in the activation rate of sodium chlorite and a reduction in the turbidity removal rate.

[0083] In summary, the chlorine dioxide releasing agent obtained by this invention is prepared using potassium ferrate, sodium chlorite, organic acids, iron salts, peroxide donors, succinic acid, etc. The pH value of the activated solution is close to neutral, and the conversion rate of sodium chlorite is effectively improved. It has the dual functions of disinfection and flocculation of water, which not only improves cleaning efficiency and effectiveness, but also greatly reduces production costs.

[0084] The above are merely preferred embodiments of the present invention and are not limited to the examples described above. Those skilled in the art will recognize that various modifications and variations can be made based on the principles of the present invention. Any modifications or improvements made should be considered within the scope of protection of the present invention.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A chlorine dioxide releasing agent that combines low corrosivity and flocculation functions, characterized in that, It is composed of the following raw materials by mass percentage: potassium ferrate 8-12%, sodium chlorite 16-22%, organic acid 15-23%, iron salt 12-14%, peroxide donor 10-20%, succinic acid 6-12%, and the balance is desiccant. The organic acid is at least one of tartaric acid, citric acid, malic acid, glycolic acid, and hydroxybutyric acid; the iron salt is at least one of ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate; and the peroxide donor is a sodium chloride-sodium sulfate-hydrogen peroxide adduct.

2. The chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 1, characterized in that, The organic acid is obtained by mixing tartaric acid and hydroxybutyric acid in a mass ratio of 1:(1-2), or by mixing tartaric acid, citric acid and hydroxybutyric acid in a mass ratio of 2:(3-4):(8-10), or by mixing malic acid, citric acid and glycolic acid in a mass ratio of 8:(3-5):(8-10).

3. The chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 1, characterized in that, The iron salt is obtained by mixing ferric ammonium citrate and ferric sodium ethylenediaminetetraacetate in a mass ratio of (0-4):(1-12).

4. The chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 1, characterized in that, The desiccant is a mixture of anhydrous sodium sulfate and magnesium sulfate in a mass ratio of (4-7):(5-12).

5. The chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 1, characterized in that, The preparation method of the sodium chloride-sodium sulfate-hydrogen peroxide adduct is as follows: A 30wt% sodium sulfate aqueous solution, a 30wt% sodium chloride aqueous solution, and a 30wt% hydrogen peroxide solution were mixed in a volume ratio of 1:1:1 and reacted at 5-10℃ for 20-40s. The reaction solution was then cooled at -5℃ to crystallize, filtered, and dried to obtain a sodium chloride-sodium sulfate-hydrogen peroxide adduct.

6. The method for preparing the chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: potassium ferrate, sodium chlorite and desiccant are mixed according to the mass percentage, succinic acid, iron salt and organic acid are added and mixed, and finally a peroxide donor is added and mixed to obtain powder or tablets.

7. The method for preparing the chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 6, characterized in that, When preparing tablets, a release agent is added at the same time as the peroxide donor; the release agent is PEG4000 or PEG6000.

8. The method for preparing the chlorine dioxide releasing agent with both low corrosiveness and flocculation function according to claim 7, characterized in that, The amount of the release agent is 1-5% of the total mass of all raw materials.

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