Use of a polysilicate iron zirconium flocculant in removing phosphate from sewage

Abstract

The invention discloses an application of a polysilicate iron zirconium flocculant in removing phosphate and fluoride from sewage. The polysilicate iron zirconium flocculant is prepared by dissolving water glass in ultrapure water, adjusting the pH value of the water glass solution to 2-5, stirring and activating the solution at room temperature for 1-24 hours to obtain a polysilicate solution, and adding a soluble iron salt and a zirconium salt to the polysilicate solution, stirring and polymerizing the solution. The preparation time is short and the cost is low. The polysilicate iron zirconium flocculant is a light yellow transparent liquid, flocculates and settles quickly in water, and has a deep purification effect on phosphate and fluoride ions that pollute water bodies.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment flocculants, and specifically relates to application of a polysilicate iron zirconium flocculant in removing phosphate and fluoride from sewage. Background Art

[0002] As the challenge of global water scarcity grows, treating and recycling industrial wastewater is a sustainable approach. Effectively removing pollutants such as fluoride and phosphate from wastewater is a major challenge. High fluoride intake can lead to conditions such as dental fluorosis and bone fluorosis. While phosphate is essential for plant and animal growth, excessive phosphate loading can lead to eutrophication in lakes and rivers, causing algal blooms and severely impacting the health of aquatic ecosystems. Furthermore, excessive discharge of pollutants such as levofloxacin and COD can also impact aquatic ecosystems.

[0003] Polysilicic acid flocculants have been widely studied since the 1980s. The type and properties of flocculants have a significant impact on the effectiveness of flocculation. The most widely used iron salt and aluminum salt flocculants are not very effective in removing fluoride. Moreover, the aluminum-based flocculants have a high concentration of residual metals and have certain environmental risks. In addition, the deep treatment effect of iron-based flocculants on slightly polluted water bodies needs to be improved. Therefore, the development of a method to remove high levels of phosphate and F in sewage has become a hot topic. - The new technology has also become one of the innovative directions of water treatment today. Summary of the Invention

[0004] The present invention provides a new use of a polysilicate iron zirconium flocculant, namely, its use in removing phosphate and fluoride from sewage. The polysilicate iron zirconium flocculant is prepared by dissolving water glass in ultrapure water, adjusting the pH value of the water glass solution to 2-5, stirring and activating the solution at room temperature for 1-24 hours to obtain a polysilicate solution, and then adding a soluble iron salt and a zirconium salt to the polysilicate solution, stirring and polymerizing the solution. The polysilicate iron zirconium flocculant is a light yellow transparent liquid, flocculates and settles quickly in water, and has a deep purification effect on phosphate and fluoride ions that pollute water bodies.

[0005] The specific preparation of the polyzirconium iron silicate flocculant of the present invention is as follows:

[0006] (1) Take a certain amount of water glass and dissolve it in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.05-0.2 mol / L;

[0007] (2) Acid is added to the water glass solution to adjust the pH value to 2-5, and the solution is stirred and activated at room temperature for 1-24 hours to obtain a polysilicic acid solution; the acid is a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution with a mass concentration of 30%-50%;

[0008] (3) adding soluble iron salt and zirconium salt to the polysilicic acid solution at a molar ratio of Fe:Si of 1:0.3-2 and a molar ratio of Fe:Zr of 1:0.5-2, stirring and polymerizing to obtain a polysilicate iron zirconium flocculant;

[0009] The soluble iron salt is selected from ferric chloride and ferric nitrate, and the zirconium salt is selected from zirconium nitrate and zirconium oxychloride.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The invention adopts metallic iron and zirconium as modifiers of polysilicate and prepares polysilicate iron zirconium flocculant by copolymerization. The preparation process is simple, the cost is low, no waste acid or waste alkali is generated, and there is no secondary pollution.

[0012] The polyzirconium iron silicate flocculant prepared by the invention is a light yellow transparent liquid, is easy to use, requires a small amount, has fast flocculation and sedimentation, has a deep purification effect on phosphate and fluoride in water bodies, and the treated wastewater can meet the GB8978-1996 emission standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic diagram of the phosphate removal effect of the polyzirconium iron silicate flocculant of the present invention;

[0014] Figure 2 Schematic diagram of the fluorine removal effect of the polysilicic acid zirconium flocculant of the present invention;

[0015] Figure 3 The results of phosphate removal in treating fluorine- and phosphorus-containing wastewater with different pH values ​​using polysilicate iron zirconium flocculants and polysilicate iron flocculants are shown;

[0016] Figure 4 The results of fluoride removal in fluorine-containing and phosphorus-containing wastewater with different pH values ​​using polysilicate iron zirconium flocculant and polysilicate iron flocculant. DETAILED DESCRIPTION

[0017] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described 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 making any creative work are within the scope of protection of the present invention.

[0018] The phosphate content in the examples was determined by the method in GB8978-1996;

[0019] Example 1: Preparation and application of polyzirconium iron silicate flocculant

[0020] 1. Preparation of polysilicate iron zirconium flocculant

[0021] (1) Dissolve water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.05 mol / L;

[0022] (2) adding a 30% mass concentration hydrochloric acid solution to the water glass solution to adjust the pH value to 5, stirring and activating at room temperature for 4 hours to obtain a polysilicic acid solution;

[0023] (3) Adding ferric chloride and zirconium oxychloride to the polysilicic acid solution at a molar ratio of Fe:Si of 1:1 and a molar ratio of Fe:Zr of 1:1, stirring and polymerizing for 24 hours to prepare a polysilicate iron zirconium flocculant;

[0024] At the same time, a polyferric silicate flocculant was prepared as a control by the above method except that zirconium oxychloride was not added;

[0025] 2. Treatment of fluorine- and phosphorus-containing wastewater with polysilicate iron zirconium flocculant

[0026] (1) Prepare a phosphorus- and fluorine-containing wastewater mother liquor containing 1000 mg / L of phosphate and 500 mg / L of fluorine. Subsequently, a certain amount of the mother liquor was taken and diluted to 200 mg / L of phosphate and 100 mg / L of fluorine in the experiment, and the pH of the wastewater was adjusted to 5;

[0027] (2) Use a 250 mL beaker to fill 200 mL of phosphorus- and fluoride-containing wastewater, and add 1, 2, 3, 5, 10, 15, and 20 mL of polysilicate iron zirconium flocculant to the phosphorus- and fluoride-containing wastewater respectively; after stirring at 500 rpm for 20 minutes, let it stand for 24 hours, and take 25 mL of the supernatant; determine the residual phosphate and fluoride content of the supernatant, and calculate the phosphate and fluoride removal rates;

[0028] See the results Figure 1 、 2 ,from Figure 1 It can be seen that when the addition amount of polysilicate iron zirconium flocculant is 3mL, the removal rate of phosphate in wastewater is 97.47%. Figure 2 It can be seen that when the addition amount of polysilicate iron zirconium flocculant is 10mL, the removal rate of fluoride in wastewater is 93.3%;

[0029] 3. Treatment of fluorine- and phosphorus-containing wastewater with different pH values ​​by polysilicate iron zirconium flocculant and control polysilicate iron flocculant

[0030] The method is the same as above, except that the pH of the fluorine-containing and phosphorus-containing wastewater is adjusted to 4 or 5, and the amount of flocculant added is 6 mL. The results are shown in Figure 3 、 4 It can be seen from the figure that the removal effect of the polysilicate iron zirconium flocculant of the present invention is better than that of the control polysilicate iron flocculant in wastewater with a pH of 4 or 5. When the addition amount of the control polysilicate iron flocculant is 6 mL, the phosphate removal rate is 99.5%, and the fluoride removal rate is only 9.23%.

[0031] Example 2: Preparation and application of polyzirconium iron silicate flocculant

[0032] 1. Preparation of polysilicate iron zirconium flocculant

[0033] (1) Dissolve water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.1 mol / L;

[0034] (2) adding a 30% mass concentration hydrochloric acid solution to the water glass solution to adjust the pH value to 2, stirring and activating at room temperature for 4 hours to obtain a polysilicic acid solution;

[0035] (3) Adding ferric chloride and zirconium oxychloride to the polysilicic acid solution at a molar ratio of Fe:Si of 1:1 and a molar ratio of Fe:Zr of 1:1.5, stirring and polymerizing for 24 hours to prepare a polysilicate iron zirconium flocculant;

[0036] 2. Treatment of fluorine- and phosphorus-containing wastewater with polysilicate iron zirconium flocculant

[0037] (1) Prepare phosphorus- and fluoride-containing wastewater containing 200 mg / L of phosphate and 100 mg / L of fluoride, and adjust the pH of the wastewater to 5;

[0038] (2) A 250 mL beaker was filled with 200 mL of phosphorus- and fluorine-containing wastewater, and 10 mL of polysilicate iron zirconium flocculant was added to the phosphorus- and fluorine-containing wastewater, respectively. The mixture was stirred at 500 rpm for 20 min, and then allowed to stand for 24 h to collect the supernatant. The residual phosphate and fluoride contents in the supernatant were determined, and the removal rates of phosphate and fluoride were calculated. The results showed that the removal rates of phosphate and fluoride were 99.9% and 90.9% respectively.

[0039] Example 3: Preparation and application of polyzirconium iron silicate flocculant

[0040] 1. Preparation of polysilicate iron zirconium flocculant

[0041] (1) Dissolve water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.2 mol / L;

[0042] (2) adding a 30% mass concentration hydrochloric acid solution to the water glass solution to adjust the pH value to 2, stirring and activating at room temperature for 4 hours to obtain a polysilicic acid solution;

[0043] (3) Adding ferric chloride and zirconium oxychloride to the polysilicic acid solution at a molar ratio of Fe:Si of 1:2 and a molar ratio of Fe:Zr of 1:1, stirring and polymerizing for 24 hours to prepare a polysilicate iron zirconium flocculant;

[0044] 2. Treatment of fluorine- and phosphorus-containing wastewater with polysilicate iron zirconium flocculant

[0045] (1) Prepare phosphorus- and fluoride-containing wastewater containing 200 mg / L of phosphate and 100 mg / L of fluoride, and adjust the pH of the wastewater to 5;

[0046] (2) A 250 mL beaker was filled with 200 mL of phosphorus- and fluorine-containing wastewater, and 10 mL of polysilicate iron zirconium flocculant was added to the phosphorus- and fluorine-containing wastewater, respectively. The mixture was stirred at 500 rpm for 20 min, and then allowed to stand for 24 h to collect the supernatant. The residual phosphate and fluoride contents in the supernatant were determined, and the removal rates of phosphate and fluoride were calculated. The results showed that the removal rates of phosphate and fluoride were 99.8% and 82.27% respectively.

Claims

1. Application of a polysilicate iron zirconium flocculant in removing phosphate from sewage, characterized in that: The pH of sewage is 4-5.

2. The use according to claim 1, characterized in that: The polysilicate iron zirconium flocculant is prepared by dissolving water glass in ultrapure water, adjusting the pH value of the water glass solution to 2-5, stirring and activating the solution at room temperature for 1-24 hours to obtain a polysilicate solution, and then adding soluble iron salt and zirconium salt to the polysilicate solution, stirring and polymerizing the solution.

3. The use according to claim 1, characterized in that: The molar concentration of SiO2 in water glass solution is 0.05-0.2 mol / L.

4. The use according to claim 1, characterized in that: The acid used to adjust the pH is a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution with a mass concentration of 30%-50%.

5. The use according to claim 1, characterized in that: The soluble iron salt is selected from ferric chloride and ferric nitrate, and the zirconium salt is selected from zirconium nitrate and zirconium oxychloride.

6. The use according to claim 1, characterized in that: The Fe:Si molar ratio is 1:0.3-2, and the Fe:Zr molar ratio is 1:0.5-2.

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