Application of polysilicate ferric zirconium flocculant in removal of phosphate and fluorine in sewage

Abstract

The invention discloses application of a polysilicate ferric zirconium flocculant in removal of phosphate and fluorine in sewage, and the polysilicate ferric zirconium flocculant is prepared by dissolving water glass with ultrapure water, adjusting the pH value of the water glass solution to 2-5, stirring and activating at room temperature for 1-24 hours to prepare a polysilicate solution, adding soluble ferric salt and zircon salt into the polysilicate solution, stirring and activating at room temperature for 1-24 hours to obtain the polysilicate ferric zirconium flocculant. And stirring and polymerizing. The preparation time is short and the cost is low; the polysilicate ferric zirconium flocculant is a faint yellow transparent liquid, is fast in flocculation and sedimentation in water, and has a deep purification effect on phosphate and fluorine ions of polluted water.

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 in sewage. Background Art

[0002] As the challenge of global water scarcity grows day by day, treating and recycling industrial wastewater is one of the sustainable development methods. Effectively removing pollutants such as fluoride and phosphate from wastewater is an important challenge. High concentrations of fluoride intake can cause fluorosis and bone fluorosis. Although phosphate is an essential element for the growth of plants and animals, excessive phosphate load can lead to eutrophication of lakes and rivers, resulting in algal blooms. This seriously affects the health of aquatic ecosystems. In addition, excessive discharge of many pollutants such as levofloxacin and COD can also affect the aquatic ecological environment.

[0003] Polysilicate flocculants have been widely studied since the 1980s. The type and properties of flocculants have an important impact on the effect of flocculation. The most widely used iron salt and aluminum salt flocculants are not very effective in removing fluoride. In addition, the residual metal concentration of aluminum-based flocculants is high, which has certain environmental hazards. In addition, the deep treatment effect of iron-based flocculants on micro-polluted water bodies needs to be improved. Therefore, it is necessary to develop a method to remove high levels of phosphate and F in sewage. - The new technology has also become one of the innovative directions of water treatment today. Summary of the invention

[0004] The invention provides a new use of a polysilicate iron zirconium flocculant, namely, use of the 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, adding soluble iron salt and zirconium salt to the polysilicate solution, stirring and polymerizing the solution, and obtaining the polysilicate iron zirconium flocculant. 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 a water body.

[0005] The specific preparation of the polysilicate iron zirconium flocculant of the present invention is as follows: (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; (2) After adding acid to the water glass solution to adjust the pH value to 2-5, stirring and activating at room temperature for 1-24 hours, a polysilicic acid solution is obtained; the acid is a hydrochloric acid solution, a sulfuric acid solution or a nitric acid solution with a mass concentration of 30%-50%; (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; The soluble iron salt is selected from ferric chloride and ferric nitrate, and the zirconium salt is selected from zirconium nitrate and zirconium oxychloride.

[0006] Compared with the prior art, the present invention has the following beneficial effects: The invention adopts metal iron and zirconium as modifiers of polysilicate, and prepares polysilicate iron zirconium flocculant by copolymerization, which has simple preparation process, low cost, no waste acid and waste alkali are generated, and no secondary pollution.

[0007] The polyzirconium iron silicate flocculant prepared by the invention is a light yellow transparent liquid, is easy to use, has a small amount of use, has fast flocculation and sedimentation, has a deep purification effect on phosphate and fluoride in water bodies, and the wastewater after treatment can meet the GB8978-1996 discharge standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the effect of the polysilicate iron zirconium flocculant of the present invention on phosphate removal; Figure 2 This is a schematic diagram of the effect of the polysilicate iron zirconium flocculant of the present invention on fluorine removal; Figure 3 The results of phosphate removal in treating fluorine- and phosphorus-containing wastewaters with different pH values ​​using polysilicate iron zirconium flocculants and polysilicate iron flocculants; Figure 4 The results of fluoride removal in treating fluoride- and phosphorus-containing wastewaters with different pH values ​​using polysilicate iron zirconium flocculant and polysilicate iron flocculant. DETAILED DESCRIPTION

[0009] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 protection scope of the present invention; The phosphate content in the examples is determined by referring to the method in GB8978-1996; Example 1: Preparation and application of polysilicate iron zirconium flocculant 1. Preparation of polysilicate iron zirconium flocculant (1) Dissolving water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.05 mol / L; (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; (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 obtain a polysilicate iron zirconium flocculant; At the same time, a polysilicate iron flocculant was prepared as a control according to the above method except that zirconium oxychloride was not added; 2. Treatment of fluorine-containing and phosphorus-containing wastewater with polysilicate iron zirconium flocculant (1) Prepare a phosphorus- and fluorine-containing wastewater mother liquor containing 1000 mg / L phosphate and 500 mg / L fluorine. Then take a certain amount of the mother liquor and dilute it to 200 mg / L phosphate and 100 mg / L fluorine in the experiment and adjust the wastewater pH to 5; (2) Use a 250mL beaker to fill 200mL of phosphorus- and fluoride-containing wastewater, and add 1, 2, 3, 5, 10, 15, and 20mL of polysilicate iron zirconium flocculant to the phosphorus- and fluoride-containing wastewater respectively; after stirring at 500rpm for 20min, let it stand for 24h and take 25mL of supernatant; determine the residual phosphate and fluoride content of the supernatant, and calculate the removal rate of phosphate and fluoride; 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%; 3. Treatment of fluorine-containing and phosphorus-containing wastewater with different pH values ​​by polysilicate iron zirconium flocculant and control polysilicate iron flocculant The method is the same as above, except that the pH of the fluorine-containing and phosphorus-containing wastewater is adjusted to 3 or 4, 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 in wastewater with a pH of 4 or 5, the removal effect of the polysilicate iron zirconium flocculant of the present invention is better than that of the control polysilicate iron flocculant. 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%.

[0010] Example 2: Preparation and application of polysilicate iron zirconium flocculant 1. Preparation of polysilicate iron zirconium flocculant (1) Dissolving water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.1 mol / L; (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; (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 obtain a polysilicate iron zirconium flocculant; 2. Treatment of fluorine-containing and phosphorus-containing wastewater with polysilicate iron zirconium flocculant (1) Prepare phosphorus- and fluoride-containing wastewater containing 200 mg / L phosphate and 100 mg / L fluoride, and adjust the pH of the wastewater to 5; (2) Use a 250-mL beaker to fill 200 mL of phosphorus- and fluorine-containing wastewater, and add 10 mL of polysilicate iron zirconium flocculant to the phosphorus- and fluorine-containing wastewater respectively; after stirring at 500 rpm for 20 min, let it stand for 24 h and take the supernatant; determine the residual phosphate and fluoride content of the supernatant, and calculate the removal rates of phosphate and fluoride; the results showed that the removal rates of phosphate and fluoride were 99.9% and 90.9% respectively.

[0011] Example 3: Preparation and application of polysilicate iron zirconium flocculant 1. Preparation of polysilicate iron zirconium flocculant (1) Dissolving water glass in ultrapure water to prepare a water glass solution with a SiO2 molar concentration of 0.2 mol / L; (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; (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 obtain a polysilicate iron zirconium flocculant; 2. Treatment of fluorine-containing and phosphorus-containing wastewater with polysilicate iron zirconium flocculant (1) Prepare phosphorus- and fluoride-containing wastewater containing 200 mg / L phosphate and 100 mg / L fluoride, and adjust the pH of the wastewater to 5; (2) Use a 250-mL beaker to fill 200 mL of phosphorus- and fluorine-containing wastewater, and add 10 mL of polysilicate iron zirconium flocculant to the phosphorus- and fluorine-containing wastewater respectively; after stirring at 500 rpm for 20 min, let it stand for 24 h and take the supernatant; determine the residual phosphate and fluoride content of the supernatant, and calculate the removal rates of phosphate and fluoride; the results showed that the removal rate of phosphate was 99.8%, and the removal rate of fluoride was 82.27%.

Claims

1. Application of a polysilicate iron zirconium flocculant in removing phosphate and fluoride from sewage.

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 at room temperature for 1-24 hours to obtain a polysilicate solution, and adding soluble iron salt and zirconium salt to the polysilicate solution, stirring and polymerizing.

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 for adjusting 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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