High-efficiency phosphorus removal flocculant and preparation method thereof

Abstract

The present application relates to the technical field of phosphorus removal agent, and provides a high-efficiency phosphorus removal flocculant and a preparation method thereof.The polymeric ferric sulfate reaction solution and the ferric chloride are mixed under certain temperature conditions, so that the polymeric ferric sulfate and the ferric chloride are heat compounded, the stability of the ferric chloride is improved, and then the adding proportion of the ferric chloride is improved; and the polymeric ferric sulfate and the ferric chloride are compounded, the phosphorus removal effect of the polymeric ferric sulfate is improved, and the flocculation of the ferric chloride is improved.The results of examples show that the phosphorus removal rate of the high-efficiency phosphorus removal flocculant can reach more than 78%, which is obviously higher than the phosphorus removal rate of the polymeric ferric sulfate and the ferric chloride mixedly used.

Description

Technical Field

[0001] This invention relates to the field of phosphorus removal flocculant technology, and in particular to a high-efficiency phosphorus removal flocculant and its preparation method. Background Technology

[0002] Polyferric sulfate is a macromolecular inorganic compound formed by the polymerization of ferric ions through hydroxyl groups. It exhibits high polymerizability, and its hydrolysis products include polynuclear complexes and other products with highly efficient flocculation effects. Its flocculation effect is 3 to 15 times better than that of ferric chloride. As a high-molecular polymer, it is less affected by temperature differences and pH values, has wide applicability, high treatment efficiency, and low overall cost.

[0003] Ferric chloride, upon dissolving, generates ferric ions (Fe3+). These ferric ions react with water to form ferric hydroxide colloids, which have adsorption properties. These colloidal substances adsorb and coagulate suspended solids in water, making them excellent coagulants. Additionally, iron ions (Fe3+)... 3+ With phosphate ions PO4 3- Ferric chloride undergoes a complexation reaction to form a precipitate, effectively removing phosphorus from wastewater and making it an effective phosphorus removal agent. However, ferric chloride is a traditional iron salt with strong corrosiveness, and the treated water often exhibits an iron-like color, resulting in excessive color in the effluent. Ferric chloride also lacks basicity and has poor stability.

[0004] There are reports in the existing technology of using polyferric sulfate and ferric chloride in combination, but they all involve directly mixing the two. In this method, the stability of ferric chloride is still relatively poor, so the proportion added is small, usually not exceeding 10%, otherwise crystallization is likely to occur. Furthermore, in this method, polyferric sulfate and ferric chloride are simply mixed, and the improvement in phosphorus removal effect is not significant. Summary of the Invention

[0005] In view of this, the present invention provides a highly efficient phosphorus removal flocculant and its preparation method. The present invention utilizes the residual heat of the polyferric sulfate reaction solution to thermally combine polyferric sulfate and ferric chloride, which improves the stability of ferric chloride and thus increases its addition ratio, resulting in a significantly improved phosphorus removal effect of the obtained phosphorus removal flocculant.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A method for preparing a high-efficiency phosphorus removal flocculant includes the following steps:

[0008] The ferrous salt is dissolved in water to obtain a ferrous salt solution;

[0009] The ferrous salt solution, concentrated sulfuric acid, and oxidant are mixed and subjected to an oxidation reaction to obtain a polyferric sulfate reaction solution.

[0010] The polyferric sulfate reaction solution is mixed with ferric chloride to form a composite of polyferric sulfate and ferric chloride, thereby obtaining the high-efficiency phosphorus removal flocculant; the mixing temperature is 45-65℃.

[0011] Based on the total mass of the raw materials being 100%, the mass fraction of ferric chloride is 15-25%.

[0012] Preferably, based on the total mass of the raw materials being prepared (100%), the mass fraction of each raw material is as follows: water 15-25%, ferrous salt 40-55%, concentrated sulfuric acid 1-6%, oxidant 1-5%, and ferric chloride 15-25%.

[0013] Preferably, based on the total mass of the raw materials being prepared (100%), the mass fraction of each raw material is as follows: water 19-21%, ferrous salt 50-53%, concentrated sulfuric acid 4.5-5.5%, oxidant 3-4%, and ferric chloride 20-22%.

[0014] Preferably, the ferrous salt includes one or more of ferrous sulfate and ferrous chloride; the oxidant includes one or more of sodium chlorate, potassium chlorate and hydrogen peroxide.

[0015] Preferably, mixing the polyferric sulfate reaction solution and ferric chloride specifically includes: mixing the polyferric sulfate reaction solution with ferric chloride while it is hot, and using the residual heat of the polyferric sulfate reaction solution to make the polyferric sulfate and ferric chloride composite.

[0016] Or it may include: mixing polyferric sulfate reaction solution and ferric chloride under heating conditions to make polyferric sulfate and ferric chloride composite;

[0017] Preferably, the oxidation reaction of mixing the ferrous salt solution, concentrated sulfuric acid, and oxidant specifically includes: mixing the ferrous salt solution and concentrated sulfuric acid, and then adding an oxidant to carry out the oxidation reaction.

[0018] Preferably, the oxidation reaction takes 0.5 to 1.5 hours.

[0019] Preferably, the compounding time is 0.2 to 1 hour.

[0020] Preferably, after the compounding is completed, the resulting solution system is filtered, and the resulting filtrate is the high-efficiency phosphorus removal flocculant.

[0021] The present invention also provides a highly efficient phosphorus removal flocculant prepared by the preparation method described above.

[0022] This invention provides a method for preparing a highly efficient phosphorus removal flocculant, comprising the following steps: dissolving ferrous salt in water to obtain a ferrous salt solution; mixing the ferrous salt solution, concentrated sulfuric acid, and an oxidant to conduct an oxidation reaction to obtain a polyferric sulfate reaction solution; mixing the polyferric sulfate reaction solution with ferric chloride to achieve a composite reaction, thereby obtaining the highly efficient phosphorus removal flocculant; the mixing temperature is 45–65°C; and the mass fraction of ferric chloride is 15–25% based on the total mass of the raw materials (100%). This invention mixes the polyferric sulfate reaction solution and ferric chloride at a certain temperature, allowing for thermal composite reaction, which improves the stability of ferric chloride and thus increases its addition ratio. Furthermore, this invention combines polyferric sulfate and ferric chloride, improving the phosphorus removal effect of polyferric sulfate while enhancing the flocculation effect of ferric chloride. Example results show that the phosphorus removal rate of the highly efficient phosphorus removal flocculant of this invention can reach over 78%, significantly higher than the phosphorus removal rate achieved by using a mixture of polyferric sulfate and ferric chloride. Detailed Implementation

[0023] This invention provides a method for preparing a highly efficient phosphorus removal flocculant, comprising the following steps:

[0024] The ferrous salt is dissolved in water to obtain a ferrous salt solution;

[0025] The ferrous salt solution, concentrated sulfuric acid, and oxidant are mixed and subjected to an oxidation reaction to obtain a polyferric sulfate reaction solution.

[0026] The polyferric sulfate reaction solution is mixed with ferric chloride to form a composite of polyferric sulfate and ferric chloride, thereby obtaining the highly efficient phosphorus removal flocculant; the mixing temperature is 45-65℃.

[0027] In this invention, the total mass of the raw materials (i.e., the total mass of water, ferrous salt, concentrated sulfuric acid, oxidant and ferric chloride) is taken as 100%, wherein the mass fraction of ferric chloride is 15-25%.

[0028] In this invention, based on the total mass of the raw materials (i.e., the total mass of water, ferrous salt, concentrated sulfuric acid, oxidant, and ferric chloride) as 100%, the preferred mass fractions of each raw material are: water 15-25%, more preferably 19-21%; ferrous salt 40-55%, more preferably 50-53%; concentrated sulfuric acid 1-6%, more preferably 4.5-5.5%; oxidant 1-5%, more preferably 3-4%; and ferric chloride 15-25%, more preferably 20-22%.

[0029] In this invention, the water is preferably pure water; the ferrous salt preferably includes one or more of ferrous sulfate and ferrous chloride; the oxidant preferably includes one or more of sodium chlorate, potassium chlorate and hydrogen peroxide; and the concentrated sulfuric acid is commercially available concentrated sulfuric acid with a concentration of 98%.

[0030] The preparation method is described in detail below.

[0031] This invention first involves dissolving ferrous salt in water to obtain a ferrous salt solution. The method of dissolution is not particularly important; any method well-known to those skilled in the art that can completely dissolve the ferrous salt is acceptable.

[0032] After obtaining the ferrous salt solution, the present invention mixes the ferrous salt solution, concentrated sulfuric acid, and an oxidant to carry out an oxidation reaction to obtain a polyferric sulfate reaction solution. In the present invention, the preferred method for carrying out the oxidation reaction by mixing the ferrous salt solution, concentrated sulfuric acid, and oxidant is to first mix the ferrous salt solution and concentrated sulfuric acid, and then add the oxidant to carry out the oxidation reaction; the preferred method for mixing the ferrous salt solution and concentrated sulfuric acid is stirring, and the present invention does not have special requirements for the stirring time, as long as it is stirred until completely mixed; the oxidant is preferably added slowly; the preferred time for the oxidation reaction is 0.5–1.5 h, more preferably 1 h; the oxidation reaction is preferably carried out at room temperature, and the oxidation reaction is exothermic, with the system temperature gradually increasing during the reaction.

[0033] After obtaining the polyferric sulfate reaction solution, the present invention mixes the polyferric sulfate reaction solution with ferric chloride to composite the polyferric sulfate and ferric chloride, thereby obtaining the highly efficient phosphorus removal flocculant; the mixing temperature is 45-65℃. In the present invention, mixing the polyferric sulfate reaction solution and ferric chloride specifically includes: mixing the polyferric sulfate reaction solution with ferric chloride while hot, utilizing the residual heat of the polyferric sulfate reaction solution to composite the polyferric sulfate and ferric chloride; when using this method for composite formation, the system temperature at the beginning of the composite formation is preferably 60±5℃, and the system temperature at the end of the composite formation is preferably 50±5℃.

[0034] Alternatively, mixing the polyferric sulfate reaction solution and ferric chloride specifically includes: mixing the polyferric sulfate reaction solution and ferric chloride under heating conditions to make the polyferric sulfate and ferric chloride composite; the heating temperature is 45-65°C, preferably 50-60°C.

[0035] In this invention, the compounding time is preferably 0.2 to 1 hour, more preferably 0.5 to 0.7 hours; after the compounding is completed, the invention preferably further includes filtering the obtained solution system, and the obtained filtrate is the high-efficiency phosphorus removal flocculant.

[0036] This invention also provides a highly efficient phosphorus removal flocculant prepared by the method described above. The highly efficient phosphorus removal flocculant provided by this invention exhibits good stability and high ferric chloride content, resulting in excellent flocculation and phosphorus removal effects, and has broad application prospects.

[0037] The high-efficiency phosphorus removal flocculant of the present invention is used for the removal of phosphorus from phosphorus-containing wastewater. The total phosphorus content in the phosphorus-containing wastewater is preferably 0.5-3.5 mg / L, and the amount of high-efficiency phosphorus removal flocculant added (calculated by the ratio of the mass of high-efficiency phosphorus removal flocculant to the mass of phosphorus-containing wastewater) is preferably 40-150 ppm, more preferably 40-100 ppm.

[0038] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0039] Example 1

[0040] Take 1940 kg of water, stir, add 5250 kg of ferrous sulfate to the water, and after the ferrous sulfate dissolves, continue stirring, add 510 kg of concentrated sulfuric acid, mix completely, slowly add 300 kg of sodium chlorate oxidant, react for 1 hour, add 2000 kg of ferric chloride, and compound with residual heat for 0.5 hours, filter, and obtain the high-efficiency phosphorus removal flocculant product.

[0041] Example 2

[0042] Take 200 kg of water, stir, add 500 kg of ferrous sulfate to the water, and after the ferrous sulfate dissolves, continue stirring, add 50 kg of concentrated sulfuric acid, mix completely, slowly add 30 kg of potassium chlorate oxidant, react for 1.2 hours, add 210 kg of ferric chloride, and compound with residual heat for 0.7 hours, filter, and obtain the high-efficiency phosphorus removal flocculant product.

[0043] Comparative Example 1

[0044] The other conditions were the same as in Example 1, except that after the oxidation reaction was completed, the reaction solution was cooled and then ferric chloride was added. As a result, ferric chloride crystallized.

[0045] Test Example 1

[0046] The high-efficiency phosphorus removal flocculants prepared in Examples 1 and 2 were used to remove phosphorus from phosphorus-containing wastewater (from a wastewater treatment plant in an industrial park) with a total phosphorus content of 1.54 mg / L. The dosage of the flocculants was 100 ppm in each case. Three comparative experiments were also conducted: Group 1 used ferric chloride as the phosphorus removal agent at a dosage of 100 ppm; Group 2 used polyferric sulfate as the phosphorus removal agent at a dosage of 100 ppm; and Group 3 added both ferric chloride and polyferric sulfate at 50 ppm each. The specific experimental method was as follows: 1 L of phosphorus-containing wastewater was added to a beaker, and different agents were added. The mixture was treated using a coagulation stirring apparatus under the following conditions: rapid stirring at 250 rpm for 2 minutes, followed by slow stirring at 40 rpm for 20 minutes, and sedimentation for 20 minutes. The total phosphorus content of the supernatant was then measured.

[0047] The test results of total phosphorus content in the treated wastewater are shown in Table 1.

[0048] Table 1. Results of phosphorus removal efficiency test

[0049]

[0050]

[0051] As can be seen from the data in Table 1, the phosphorus removal flocculant of the present invention has a higher phosphorus removal rate compared with ferric chloride, polyferric sulfate, and ferric chloride + polyferric sulfate. This may be because ferric chloride attaches to the long chain of polyferric sulfate during the waste heat compounding process, forming a composite iron, thereby improving the flocculation and phosphorus removal effect, while also improving the stability of ferric chloride.

[0052] Test Example 2

[0053] The high-efficiency phosphorus removal flocculants prepared in Examples 1 and 2 were used to remove phosphorus from phosphorus-containing wastewater (from a wastewater treatment plant in an industrial park) with a total phosphorus content of 0.82 mg / L. The specific test methods and conditions were the same as in Example 1, except that the dosage of the agent was changed. Specifically, the dosage of the agent in Examples 1 and 2 was 40 ppm. Three sets of comparative experiments were set up. In the first set, ferric chloride was used as the phosphorus removal agent and the dosage was 40 ppm. In the second set, polyferric sulfate was used as the phosphorus removal agent and the dosage was 40 ppm. In the third set, ferric chloride and polyferric sulfate were added at the same dosage, with ferric chloride and polyferric sulfate each added at 20 ppm.

[0054] The test results of total phosphorus content in the treated wastewater are shown in Table 2.

[0055] Table 2. Results of phosphorus removal efficiency test

[0056]

[0057] As can be seen from the data in Table 2, when the amount of the high-efficiency phosphorus removal flocculant added in this invention is 40 ppm, the phosphorus removal effect can still reach about 78%, which is significantly better than the ferric chloride group, the polyferric sulfate group, and the ferric chloride + polyferric sulfate group.

[0058] In addition, experimental results show that the color of the water in the experimental group using the high-efficiency phosphorus removal flocculant of this invention remained basically unchanged before and after treatment.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-efficiency phosphorus removal flocculant, characterized in that, Includes the following steps: The ferrous salt is dissolved in water to obtain a ferrous salt solution; The ferrous salt solution, concentrated sulfuric acid, and oxidant are mixed and subjected to an oxidation reaction to obtain a polyferric sulfate reaction solution. The polyferric sulfate reaction solution is mixed with ferric chloride to form a composite of polyferric sulfate and ferric chloride, thereby obtaining the high-efficiency phosphorus removal flocculant; the mixing temperature is 45-65℃. Based on the total mass of the raw materials being 100%, the mass fraction of ferric chloride is 15-25%.

2. The preparation method according to claim 1, characterized in that, Based on the total mass of the raw materials being 100%, the mass fraction of each raw material is as follows: water 15-25%, ferrous salt 40-55%, concentrated sulfuric acid 1-6%, oxidant 1-5%, and ferric chloride 15-25%.

3. The preparation method according to claim 1 or 2, characterized in that, Based on the total mass of the raw materials being 100%, the mass fraction of each raw material is as follows: water 19-21%, ferrous salt 50-53%, concentrated sulfuric acid 4.5-5.5%, oxidant 3-4%, and ferric chloride 20-22%.

4. The preparation method according to claim 1, characterized in that, The ferrous salt includes one or more of ferrous sulfate and ferrous chloride; the oxidant includes one or more of sodium chlorate, potassium chlorate and hydrogen peroxide.

5. The preparation method according to claim 1, characterized in that, The specific steps of mixing the polyferric sulfate reaction solution and ferric chloride include: mixing the polyferric sulfate reaction solution with ferric chloride while it is hot, and using the residual heat of the polyferric sulfate reaction solution to make the polyferric sulfate and ferric chloride composite. Or it may include: mixing polyferric sulfate reaction solution and ferric chloride under heating conditions to make polyferric sulfate and ferric chloride composite.

6. The preparation method according to claim 1, characterized in that, The oxidation reaction of the ferrous salt solution, concentrated sulfuric acid and oxidant specifically includes: mixing the ferrous salt solution and concentrated sulfuric acid, and then adding an oxidant to carry out the oxidation reaction.

7. The preparation method according to claim 1 or 6, characterized in that, The oxidation reaction takes 0.5 to 1.5 hours.

8. The preparation method according to claim 1, characterized in that, The compounding time is 0.2 to 1 hour.

9. The preparation method according to claim 1, characterized in that, After the compounding process is completed, the resulting solution system is filtered, and the resulting filtrate is the high-efficiency phosphorus removal flocculant.

10. The high-efficiency phosphorus removal flocculant prepared by the preparation method according to any one of claims 1 to 9.

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