A modified nano-calcium hydroxide emulsion for water treatment and its preparation method

Abstract

This application relates to the field of water treatment technology, specifically to a modified nano-calcium hydroxide emulsion for water treatment and its preparation method. The preparation method includes the following steps: weighing calcium hydroxide and stirring it in water to obtain a saturated lime water solution; preparing a mixed solution by mixing calcium chloride, carboxyethyl cellulose, and water; adding a crystal form control agent and gradually adding sodium hydroxide solution dropwise while stirring until no new precipitate is formed; ultrasonically vibrating to obtain a slurry; centrifuging and washing the precipitate in the slurry 3-5 times with saturated lime water; vacuum drying at 100-110℃ for 10-15 hours to obtain modified calcium hydroxide powder; adding the modified calcium hydroxide powder and sodium polyacrylate dispersant to water, stirring and dissolving to obtain the modified nano-calcium hydroxide emulsion. By selecting specific raw materials and processes, the prepared modified nano-calcium hydroxide emulsion reduces nanoparticle aggregation while possessing a certain flocculation and adsorption capacity, thus improving the purification effect.

Description

Technical Field

[0001] This application relates to the field of water treatment technology, specifically to a modified nano-calcium hydroxide emulsion for water treatment and its preparation method. Background Technology

[0002] Water treatment refers to measures taken to treat domestic sewage, industrial wastewater, etc., to meet discharge standards or for reuse. Calcium hydroxide is simple to produce and low in cost, making it a commonly used wastewater treatment agent. It has high alkalinity and precipitating properties, and can be used to adjust pH values, remove heavy metal ions and organic matter, and soften water.

[0003] Currently, most calcium hydroxide supplied on the market is in solid powder form. In wastewater treatment, powdered calcium hydroxide is ineffective. Its strong hygroscopic properties can cause burns to human skin. Furthermore, its use generates significant dust, easily polluting the atmosphere. In addition, commercially available powdered calcium hydroxide often contains impurities such as undigested overburned calcium oxide, raw-burned calcium carbonate, and silica, which can easily clog pipes and cause severe wear and tear on wastewater treatment equipment. Meanwhile, nano-calcium hydroxide is widely favored due to its small particle size and good uniformity.

[0004] Calcium hydroxide emulsions are a better choice for water treatment because they can avoid dust and environmental pollution. However, the nanoparticles are prone to agglomeration during the preparation of nano-calcium hydroxide emulsions, which places high demands on their preparation. Summary of the Invention

[0005] This application aims to overcome at least one of the deficiencies of the prior art and provide a modified nano-calcium hydroxide emulsion for water treatment and its preparation method. By selecting specific raw materials and processes, the prepared modified nano-calcium hydroxide emulsion reduces the aggregation of nanoparticles while having a certain flocculation and adsorption capacity, thereby further improving its water purification effect in water treatment.

[0006] In a first aspect, embodiments of this application provide a method for preparing a modified nano-calcium hydroxide emulsion for water treatment, achieved through the following technical solution:

[0007] A method for preparing a modified nano-calcium hydroxide emulsion for water treatment includes the following steps:

[0008] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0009] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of (8-12):(1-2):(30-50) and then ultrasonically disperse it evenly.

[0010] (3) Add crystal form control agent, and gradually add sodium hydroxide solution while stirring until no new precipitate is produced. Ultrasonic vibration for 1-2 hours to obtain modified calcium hydroxide slurry.

[0011] (4) Use the saturated lime water described in step (1) to centrifuge and wash the precipitate in the modified calcium hydroxide slurry 3-5 times at a speed of 1500-2500 r / min; dry the washed precipitate under vacuum at a temperature of 100-110℃ for 10-15 hours to obtain modified calcium hydroxide powder.

[0012] (5) Heat deionized water to boiling and then cool it naturally to room temperature. Add the modified calcium hydroxide powder and sodium polyacrylate dispersant, stir to dissolve, and obtain modified nano calcium hydroxide emulsion.

[0013] The crystal form control agent in step (3) includes styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide.

[0014] A method for preparing a modified nano-calcium hydroxide emulsion for water treatment according to an embodiment of this application has at least the following beneficial effects:

[0015] The preparation method of this application uses a liquid-phase method to prepare nano-calcium hydroxide. The raw materials are dispersed at the molecular level in the solution, which has the advantages of mild and easy-to-control reaction conditions, simple and easy-to-use equipment, and uniform composition and high purity of the obtained nanomaterials. Carboxyethyl cellulose and calcium ions are mixed in the liquid-phase system to form an inorganic-polymer homogeneous system. Carboxyethyl cellulose can enhance the steric hindrance and electrostatic repulsion to increase the distance between particles and weaken the effect of van der Waals attraction. Carboxyethyl cellulose polymer can form an interpenetrating network. At the same time, the coating and entanglement on the particle surface can also inhibit particle growth. The polar groups form a strong complexation and chelation effect with the metal ions, thereby more effectively controlling the aggregation of nanoparticles and improving the dispersibility of nano-calcium hydroxide particles.

[0016] In step (3) of the preparation method of this application, ultrasonic vibration is used. Ultrasonic waves can generate cavitation effect, which can destroy the large particles formed by agglomeration, making it easier for nano-calcium hydroxide particles to form monodisperse particles. This can reduce the agglomeration of nano-calcium hydroxide particles and improve the yield of modified nano-calcium hydroxide emulsion.

[0017] In the preparation method of this application, styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide are added as crystal form control agents in step (3). Styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide are preferentially adsorbed on different crystal faces of calcium hydroxide crystals, which can regulate the formation of calcium hydroxide crystals and make the particle size distribution of the prepared modified nano calcium hydroxide particles narrower.

[0018] The carboxyethyl cellulose added in step (2) of this application also has a flocculation effect, which can chelate with metal ions in wastewater and accelerate the precipitation of impurities in the water.

[0019] In step (5) of this application, the sodium polyacrylate dispersant forms a steric hindrance layer on the surface of the modified calcium hydroxide powder particles through intermolecular interactions. This steric hindrance effect can effectively prevent particle aggregation and significantly improve its dispersibility.

[0020] In step (4) of the preparation method of this application, washing with saturated lime water can not only better remove impurities, but also improve the purity of the modified nano calcium hydroxide emulsion, maintain the stability of the calcium hydroxide crystal form, and improve its water purification effect.

[0021] According to some embodiments of this application, the weight ratio of styrene-phenyl polyoxyethylene ether to N,N-methylenebisacrylamide is (2-4):1. Excessive styrene-phenyl polyoxyethylene ether content leads to an increase in the diameter of calcium hydroxide particles, while excessive N,N-methylenebisacrylamide content leads to changes in the morphology of calcium hydroxide. Controlling the content of both in an appropriate ratio is necessary to better regulate the formation of calcium hydroxide crystals.

[0022] According to some embodiments of this application, the concentration of the sodium hydroxide solution in step (3) is 0.5-1 g / L.

[0023] Furthermore, the dropping rate of the sodium hydroxide solution in step (3) is 1-3 mL / min. Controlling the dropping rate of the sodium hydroxide solution can make the formation of calcium hydroxide crystals more complete, the crystal form more controllable, and the particle size of the prepared nano-calcium hydroxide particles more uniform.

[0024] According to some embodiments of this application, the reaction temperature in step (3) is 15-20°C.

[0025] According to some embodiments of this application, the weight ratio of sodium polyacrylate dispersant to modified calcium hydroxide powder in step (5) is (1-2):(8-15). The properties of sodium polyacrylate dispersant not only further improve powder flowability but also enhance the stability of the modified nano-calcium hydroxide emulsion. However, excessive use of dispersant can lead to excessively high system viscosity and decreased leveling properties. The calcium hydroxide in this application, after a series of treatments, achieves good dispersion with only a small amount of sodium polyacrylate dispersant. A specific ratio can further balance the dispersibility and high viscosity of the emulsion, improving the water purification effect of the modified nano-calcium hydroxide emulsion.

[0026] Secondly, embodiments of this application provide a modified nano-calcium hydroxide emulsion for water treatment prepared using the above-described preparation method.

[0027] A modified nano-calcium hydroxide emulsion for water treatment according to an embodiment of this application has at least the following beneficial effects:

[0028] The modified nano-calcium hydroxide emulsion obtained in this application has fine particle size, low impurity content, is safe and pollution-free, and has a stable structure, making it suitable for use in water treatment.

[0029] According to some embodiments of this application, the mass concentration of calcium hydroxide in the modified nano calcium hydroxide emulsion is 20-25%.

[0030] According to some embodiments of this application, the specific surface area of ​​the modified nano-calcium hydroxide particles in the modified nano-calcium hydroxide emulsion is 50-60 m². 2 / g.

[0031] According to some embodiments of this application, the particle size of the modified nano-calcium hydroxide particles in the modified nano-calcium hydroxide emulsion is 200-300 nm.

[0032] Thirdly, this application provides the application of the modified nano-calcium hydroxide emulsion for water treatment. The modified nano-calcium hydroxide emulsion of this application, when applied to wastewater or water supply treatment, can adjust the pH value of industrial water and wastewater. Especially under acidic conditions, adding calcium hydroxide emulsion can neutralize the acidic environment, bringing the water's pH value to a suitable range, thereby preventing corrosion of equipment and pipes and protecting water treatment equipment. The nano-modified calcium hydroxide emulsion can react with heavy metal ions in wastewater to form precipitates, thereby reducing the concentration of heavy metal ions in the wastewater. Furthermore, the nano-modified calcium hydroxide can neutralize organic matter in wastewater, aiding in the precipitation and removal of these organic substances. Agricultural water typically contains high hardness and ions such as iron and manganese, which are harmful to crop growth. The nano-modified calcium hydroxide emulsion can be used for softening agricultural water, improving water quality and promoting healthy crop growth by adjusting water hardness and removing harmful ions. Additionally, the carboxyethyl cellulose in the modified nano-calcium hydroxide emulsion can provide flocculation, further enhancing the water treatment effect. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, a further detailed description will be provided below in conjunction with specific embodiments. The embodiments described herein are merely some examples of this application and should not be construed as limiting the scope of protection of this application.

[0034] Example 1

[0035] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0036] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0037] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 10:2:40 and then disperse it evenly by ultrasonication;

[0038] (3) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 3:1. At a temperature of 18°C, add 0.8 g / L sodium hydroxide solution dropwise at a rate of 2 mL / min while stirring until no new precipitate is produced. Then, ultrasonically vibrate for 1.5 h to obtain modified calcium hydroxide slurry.

[0039] (4) The precipitate in the modified calcium hydroxide slurry was washed four times by centrifugation at a speed of 2000 r / min using the saturated lime water described in step (1); the washed precipitate was dried at a temperature of 105℃ for 12 hours in a vacuum drying oven to obtain modified calcium hydroxide powder.

[0040] (5) Deionized water is heated to boiling and then cooled to room temperature naturally. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 2:12. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 20%.

[0041] Example 2

[0042] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0043] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0044] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 8:2:30 and then disperse it evenly by ultrasonication;

[0045] (3) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 4:1. At a temperature of 20°C, add 1 g / L sodium hydroxide solution dropwise at a rate of 1 mL / min while stirring until no new precipitate is produced. Then, sonicate for 1 h to obtain modified calcium hydroxide slurry.

[0046] (4) The precipitate in the modified calcium hydroxide slurry was washed three times by centrifugation at a speed of 2500 r / min using the saturated lime water described in step (1); the washed precipitate was dried in a vacuum drying oven at a temperature of 110℃ for 10 hours to obtain modified calcium hydroxide powder.

[0047] (5) Deionized water is heated to boiling and then cooled to room temperature naturally. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 2:8. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 25%.

[0048] Example 3

[0049] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0050] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0051] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 12:1:50 and then disperse it evenly by ultrasonication;

[0052] (3) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 2:1. At a temperature of 15°C, add 0.5 g / L sodium hydroxide solution dropwise at a rate of 3 mL / min while stirring until no new precipitate is produced. Then, ultrasonically vibrate for 2 hours to obtain modified calcium hydroxide slurry.

[0053] (4) The precipitate in the modified calcium hydroxide slurry was washed five times by centrifugation at a speed of 1500 r / min using the saturated lime water described in step (1); the washed precipitate was dried at a temperature of 100℃ for 15 hours in a vacuum drying oven to obtain modified calcium hydroxide powder.

[0054] (5) Deionized water is heated to boiling and then naturally cooled to room temperature. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 1:15. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 23%.

[0055] Comparative Example 1

[0056] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0057] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0058] (2) Prepare a mixed solution by mixing calcium chloride and deionized water in a weight ratio of 10:2:40 and then disperse it evenly by ultrasonication;

[0059] (3) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 3:1. At a temperature of 18°C, add 0.8 g / L sodium hydroxide solution dropwise at a rate of 2 mL / min while stirring until no new precipitate is produced. Then, ultrasonically vibrate for 1.5 h to obtain modified calcium hydroxide slurry.

[0060] (4) The precipitate in the modified calcium hydroxide slurry was washed four times by centrifugation at a speed of 2000 r / min using the saturated lime water described in step (1); the washed precipitate was dried at a temperature of 105℃ for 12 hours in a vacuum drying oven to obtain modified calcium hydroxide powder.

[0061] (5) Deionized water is heated to boiling and then cooled to room temperature naturally. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 2:12. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 20%.

[0062] Comparative Example 2

[0063] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0064] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0065] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 10:2:40 and then disperse it evenly by ultrasonication;

[0066] (3) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 3:1. At a temperature of 18°C, add 0.8 g / L sodium hydroxide solution dropwise at a rate of 2 mL / min while stirring until no new precipitate is produced. Then, ultrasonically vibrate for 1.5 h to obtain modified calcium hydroxide slurry.

[0067] (4) The precipitate in the modified calcium hydroxide slurry was washed four times by centrifugation at a speed of 2000 r / min using the saturated lime water described in step (1); the washed precipitate was dried at a temperature of 105℃ for 12 hours in a vacuum drying oven to obtain modified calcium hydroxide powder.

[0068] (5) Heat deionized water to boiling and then cool it naturally to room temperature. Add the modified calcium hydroxide powder and stir to dissolve it to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 20%.

[0069] Comparative Example 3

[0070] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0071] (1) Heat 1L of deionized water to boiling and then cool it naturally to room temperature. Weigh 10g of calcium hydroxide and place it in the cooled water and stir for 0.5 hours to obtain a saturated lime water solution.

[0072] (2) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 10:2:40 and then disperse it evenly by ultrasonication;

[0073] (3) At a temperature of 18℃, 0.8 g / L sodium hydroxide solution was added dropwise at a rate of 2 mL / min while stirring until no new precipitate was produced. The mixture was then ultrasonically vibrated for 1.5 h to obtain modified calcium hydroxide slurry.

[0074] (4) The precipitate in the modified calcium hydroxide slurry was washed four times by centrifugation at a speed of 2000 r / min using the saturated lime water described in step (1); the washed precipitate was dried at a temperature of 105℃ for 12 hours in a vacuum drying oven to obtain modified calcium hydroxide powder.

[0075] (5) Deionized water is heated to boiling and then cooled to room temperature naturally. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 2:12. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 20%.

[0076] Comparative Example 4

[0077] Preparation of a modified nano-calcium hydroxide emulsion for water treatment:

[0078] (1) Prepare a mixed solution by mixing calcium chloride, carboxyethyl cellulose and deionized water in a weight ratio of 10:2:40 and then disperse it evenly by ultrasonication;

[0079] (2) Add styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide in a weight ratio of 3:1. At a temperature of 18°C, add 0.8 g / L sodium hydroxide solution dropwise at a rate of 2 mL / min while stirring until no new precipitate is produced. Then, sonicate for 1.5 h to obtain modified calcium hydroxide slurry.

[0080] (3) The precipitate in the modified calcium hydroxide slurry was washed four times by centrifugation at 2000 r / min using deionized water; the washed precipitate was dried in a vacuum drying oven at 105℃ for 12 hours to obtain modified calcium hydroxide powder.

[0081] (4) Deionized water is heated to boiling and then cooled to room temperature naturally. Sodium polyacrylate dispersant and the modified calcium hydroxide powder are added at a weight ratio of 2:12. The mixture is stirred and dissolved to obtain a modified nano calcium hydroxide emulsion with a calcium hydroxide mass concentration of 20%.

[0082] Experimental Example

[0083] Modified nano-calcium hydroxide emulsions for water treatment prepared in Examples 1-3 and Comparative Examples 1-4 were used, and the average particle size and average specific surface area of ​​the nano-calcium hydroxide particles were measured respectively. Potassium dihydrogen phosphate solution with an initial phosphorus concentration of 20 mg / L, ferric chloride solution with an iron ion concentration of 0.1 mol / L, and wastewater solution with a pH of 3.0 were prepared respectively. Equal amounts of the modified nano-calcium hydroxide emulsions for water treatment prepared in Examples 1-3 and Comparative Examples 1-4 were added to each solution. After treatment at room temperature for 24 h, the phosphate removal rate, iron ion removal rate, and pH value of the treated wastewater were measured respectively. The test data are shown in Table 1 below:

[0084] Table 1

[0085]

[0086]

[0087] As can be seen from Table 1, the modified nano-calcium hydroxide emulsions for water treatment prepared in Examples 1-3 of this application have fine particle size, large specific surface area, and high purification efficiency for phosphate, iron ions, and acidic wastewater.

[0088] In Comparative Example 1, no carboxyethyl cellulose was added, but all other steps were the same as in Example 1. The modified nano-calcium hydroxide emulsion prepared in Comparative Example 1 for water treatment had an increased particle size, and its removal efficiency for phosphate and iron ions was significantly worse, as was its effect on regulating acidic wastewater. This indicates that the addition of carboxyethyl cellulose in this application is very important. It can not only more effectively control the aggregation of nanoparticles and improve the dispersibility of nano-calcium hydroxide particles, but also has a flocculation effect and can chelate with impurity ions in wastewater, accelerating the precipitation of impurities in the water.

[0089] In Comparative Example 2, sodium polyacrylate dispersant was not used in the preparation materials, and all other aspects were the same as in Example 1. The modified nano-calcium hydroxide emulsion prepared in Comparative Example 2 for water treatment had an increased particle size, and the removal effect on phosphate and iron ions was significantly worse, as was the effect on regulating acidic wastewater. This indicates that the sodium polyacrylate dispersant in this application forms a steric hindrance layer on the surface of the modified calcium hydroxide powder particles through intermolecular interactions. This steric hindrance effect can effectively prevent particle aggregation and significantly improve its dispersibility, thereby improving its wastewater purification efficiency.

[0090] In Comparative Example 3, no crystal form control agent was used in the preparation materials, and all other aspects were the same as in Example 1. The modified nano-calcium hydroxide emulsion prepared in Comparative Example 3 for water treatment had an increased particle size, and the removal effect on phosphate and iron ions was significantly worse, as was the effect on regulating acidic wastewater. This indicates that the addition of styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide as crystal form control agents in this application allows styrene-phenyl polyoxyethylene ether and N,N-methylenebisacrylamide to preferentially adsorb on different crystal faces of calcium hydroxide crystals, thereby controlling the formation of calcium hydroxide crystals and making the particle size distribution of the prepared modified nano-calcium hydroxide particles narrower and the particle size smaller, thus improving the purification effect of the modified nano-calcium hydroxide emulsion on water quality.

[0091] In Comparative Example 4, deionized water was used instead of saturated lime water for washing, and the rest was the same as in Example 1. The modified nano-calcium hydroxide emulsion for water treatment prepared in Comparative Example 4 had an increased particle size, and the removal effect on phosphate and iron ions was significantly worse, as was the effect on regulating acidic wastewater. This indicates that the preparation methods in this application are carefully designed. Washing with saturated lime water can not only better remove impurities, but also improve the purity of the modified nano-calcium hydroxide emulsion, maintain the stability of the calcium hydroxide crystal form, and improve its purification effect on water quality.

[0092] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions or alterations can be made to these embodiments without departing from the principles and spirit of this application, and the technical solutions resulting from such changes, modifications, substitutions or alterations will all fall within the protection scope of this application.

Claims

1. A method for the preparation of modified nano calcium hydroxide emulsion for water treatment, characterized by, The method comprises the following steps: (1) 1 L of deionized water is heated to boiling and then naturally cooled to room temperature, 10 g of calcium hydroxide is weighed and placed in the cooled water and stirred for 0.5 hours to prepare a saturated lime water solution; (2) calcium chloride, carboxymethyl cellulose and deionized water are prepared into a mixed solution according to the weight ratio (8-12):(1-2):(30-50) and ultrasonically dispersed uniformly; (3) a crystal form control agent is added, sodium hydroxide solution is gradually added while stirring until no new precipitate is produced, ultrasonic oscillation is performed for 1-2 hours to obtain modified calcium hydroxide slurry; (4) the precipitate in the modified calcium hydroxide slurry is centrifuged and washed 3-5 times at a speed of 1500-2500 r / min using the saturated lime water prepared in step (1); the washed precipitate is vacuum dried at a temperature of 100-110℃ for 10-15 hours to obtain modified calcium hydroxide powder; (5) deionized water is heated to boiling and then naturally cooled to room temperature, the modified calcium hydroxide powder and a sodium polyacrylate dispersant are added and stirred and dissolved to obtain a modified nano calcium hydroxide emulsion; The crystal form control agent in step (3) comprises styryl phenyl polyoxyethylene ether and N,N-methylene bisacrylamide.

2. A process for the preparation of modified nano calcium hydroxide emulsion for water treatment as claimed in claim 1, wherein, The weight ratio of the styryl phenyl polyoxyethylene ether and the N,N-methylene bisacrylamide is (2-4):

1.

3. A method for preparing modified nano calcium hydroxide emulsion for water treatment according to claim 1, characterized in that, The concentration of the sodium hydroxide solution in step (3) is 0.5-1 g / L.

4. A method for preparing modified nano calcium hydroxide emulsion for water treatment according to claim 3, characterized in that, The dropwise adding speed of the sodium hydroxide solution in step (3) is 1-3 mL / min.

5. The method for preparing modified nano calcium hydroxide emulsion for water treatment according to claim 1, characterized in that, The weight ratio of the sodium polyacrylate dispersant to the modified calcium hydroxide powder in step (5) is (1-2):(8-15).

6. A method for preparing modified nano calcium hydroxide emulsion for water treatment according to claim 1, characterized in that, The reaction temperature in step (3) is 15-20℃.

7. A modified nano calcium hydroxide emulsion for water treatment prepared by the method according to any one of claims 1 to 6.

8. The modified nano calcium hydroxide emulsion for water treatment according to claim 7, characterized in that, The mass concentration of calcium hydroxide in the modified nano calcium hydroxide emulsion is 20-25%.

9. The modified nano calcium hydroxide emulsion for water treatment according to claim 7, characterized in that, The specific surface area of the modified nano calcium hydroxide particles in the modified nano calcium hydroxide emulsion is 50-60 m 2 / g, and the particle size of the modified nano calcium hydroxide particles in the modified nano calcium hydroxide emulsion is 200-300 nm.

10. Use of the modified nano calcium hydroxide emulsion for water treatment according to any one of claims 7 to 9 in water purification.

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