Hydrogel with calcium ion adsorption function and preparation and application thereof

Abstract

The invention relates to the technical field of water softening, in particular to hydrogel with a calcium ion adsorption function and preparation and application thereof. The preparation method comprises the following steps: firstly, uniformly mixing sodium acrylate with sodium vinyl phosphate to obtain a first mixed solution; then adding a cross-linking agent, an initiator and styrene into the first mixed solution to obtain a second mixed solution; and finally, initiating a polymerization reaction of the second mixed solution to obtain the hydrogel with the calcium ion adsorption function. According to the hydrogel, sodium acrylate and vinyl phosphoric acid are used as functional monomers, and styrene is introduced in a polymerization process, so that the strength of the hydrogel is improved, and the hydrogel is prevented from being too soft and broken in a use process.

Description

Technical Field

[0001] The invention relates to the technical field of water softening, and in particular to a hydrogel with calcium ion adsorption function and the preparation and application thereof. Background Art

[0002] Natural water usually contains a large amount of calcium and magnesium ions. Long-term intake of water with high calcium and magnesium ion content by the human body can easily lead to adverse effects such as increased incidence of kidney stones, gastrointestinal disorders and skin damage. In addition, in the fields of biomedicine, food, and chemical industry, too hard water can cause equipment scaling and other problems that affect production efficiency. A large amount of softened water is needed to remove calcium and magnesium ions. Therefore, water softening is a very important step in the water treatment process.

[0003] At present, the commonly used water softening methods include boiling precipitation, lime-sodium carbonate softening method, ion exchange softening method, membrane separation method, etc. However, the boiling precipitation method will cause the formation of scale, affecting the use of equipment; the lime-sodium carbonate softening method requires the use of a large amount of lime, which is filtered after precipitation, so a large amount of solid pollutants will be produced and there will still be a lot of calcium and magnesium ions in the aqueous solution after treatment; and although the membrane separation method can better remove calcium and magnesium ions in water, the equipment investment and operating costs are high, and the processing capacity is limited. Therefore, the ion exchange softening method has a wider range of application scenarios due to its high ion removal ability, adsorbent regeneration ability and low cost. The ion exchange resin commonly used in the ion exchange softening method is usually a high molecular polymer containing carboxylic acid or sulfonic acid groups, which adsorbs calcium and magnesium ions in water through ion exchange. However, this method has a low adsorption of calcium and magnesium ions. Therefore, the development of an ion exchange resin that can adsorb a larger amount of calcium ions has become an important technical development direction in this field.

[0004] Patent CN 104338515A uses diammonium hydrogen phosphate and sodium alginate to react with a calcium chloride solution containing formaldehyde, and then reacts the obtained calcium alginate matrix with a sodium chloride solution to obtain a corresponding ion exchange adsorbent. However, the amount of calcium ions adsorbed by the adsorbent reported at room temperature is only 18 mg (calcium ion mass) / g (adsorbent mass); Patent CN 110711559 A uses alginate and citrate as raw materials, connects them through an amidation reaction with ethylenediamine, and then drops them into an alkaline earth metal ion solution for gelation, and then obtains an ion adsorbent through solid-liquid separation and drying. However, the amount of calcium ions adsorbed by the adsorbent is still relatively low, about 60 mg (calcium ion mass) / g (adsorbent mass).

[0005] In view of the above problems, developing a hydrogel that can quickly adsorb a large amount of calcium ions is a problem that needs to be solved by those skilled in the art. Summary of the invention

[0006] In order to solve the problem that traditional ion exchange resins have low adsorption capacity for calcium and magnesium ions in water, which affects the water softening efficiency, the purpose of the present invention is to provide a hydrogel with calcium ion adsorption function and its preparation and application; the hydrogel of the present invention can quickly adsorb a large amount of calcium ions to improve the water softening efficiency.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] The first object of the present invention is to provide a method for preparing a hydrogel having a calcium ion adsorption function, comprising the following steps:

[0009] (S1) mixing sodium acrylate and sodium vinyl phosphate to obtain a first mixed solution;

[0010] (S2) adding a crosslinking agent, an initiator and styrene to the first mixed solution obtained in step (S1) to obtain a second mixed solution;

[0011] (S3) initiating a polymerization reaction of the second mixed solution obtained in step (S2) to obtain a hydrogel having a calcium ion adsorption function.

[0012] In one embodiment of the present invention, the molar ratio of sodium acrylate, sodium vinyl phosphate and styrene is 1 to 6:1:1. The hydrogel prepared at this ratio absorbs more calcium ions than the hydrogel containing only sodium acrylate, and is therefore more suitable for absorbing calcium ions in water to soften water.

[0013] In one embodiment of the present invention, the molar ratio of sodium acrylate, sodium vinyl phosphate and styrene is 2:1:1.

[0014] In one embodiment of the present invention, the mass ratio of the first mixed liquid, the cross-linking agent, and the initiator is 1:0.002-0.02:0.001-0.003.

[0015] In one embodiment of the present invention, the crosslinking agent is selected from one of N,N'-methylenebisacrylamide and N-hydroxymethylacrylamide; preferably, the crosslinking agent is N,N'-methylenebisacrylamide. The initiator can generate free radicals to cause polymerization between olefin molecules. Too high a concentration of initiator will cause free radicals to be generated too quickly, resulting in a decrease in the degree of polymerization.

[0016] In one embodiment of the present invention, the initiator is selected from one or more of ammonium persulfate, sodium persulfate or potassium persulfate. The cross-linking agent is used to connect two molecular chains to form a network structure to form a hydrogel. Too low a content causes the hydrogel to be unformed, and too high a content causes the hydrogel network to be too tight, affecting the adsorption of calcium ions.

[0017] In one embodiment of the present invention, in step (S3), during the polymerization reaction, the temperature is 50-70° C. (under this temperature condition, the free radical polymerization reaction can proceed at a certain speed to avoid the reaction being too fast or too slow), and the time is 60-120 min;

[0018] Preferably, during the polymerization reaction, the temperature is 65° C. and the time is 60 min.

[0019] The second object of the present invention is to provide a hydrogel having calcium ion adsorption function prepared by the above method;

[0020] In the hydrogel, sodium acrylate and sodium vinyl phosphate, as functional monomers, have a good adsorption effect on calcium ions;

[0021] Styrene is used to increase the hardness of the hydrogel and facilitate its use.

[0022] The third object of the present invention is to provide a hydrogel with calcium ion adsorption function for use in water softening.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The hydrogel preparation method provided by the present invention uses sodium acrylate and sodium vinyl phosphate as functional monomers in a specific ratio, thereby achieving a better adsorption effect on calcium ions and improving water softening efficiency.

[0025] (2) The present invention uses a specific ratio of styrene and functional monomers to copolymerize, thereby improving the strength of the hydrogel, avoiding breakage caused by the hydrogel being too soft during use, and improving the convenience of use. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a hydrogel having a calcium ion adsorption function, comprising the following steps:

[0027] (S1) mixing sodium acrylate and sodium vinyl phosphate to obtain a first mixed solution;

[0028] (S2) adding a crosslinking agent, an initiator and styrene to the first mixed solution obtained in step (S1) to obtain a second mixed solution;

[0029] (S3) initiating a polymerization reaction of the second mixed solution obtained in step (S2) to obtain a hydrogel having a calcium ion adsorption function.

[0030] Furthermore, the molar ratio of sodium acrylate, sodium vinyl phosphate and styrene is 1 to 6:1:1.

[0031] Furthermore, the molar ratio of sodium acrylate, sodium vinyl phosphate and styrene is 2:1:1.

[0032] Furthermore, the mass ratio of the first mixed liquid, the cross-linking agent, and the initiator is 1:0.002-0.02:0.001-0.003.

[0033] In one embodiment of the present invention, the crosslinking agent is selected from one of N,N'-methylenebisacrylamide and N-hydroxymethylacrylamide; preferably, the crosslinking agent is N,N'-methylenebisacrylamide. The initiator can generate free radicals to cause polymerization between olefin molecules. Too high a concentration of initiator will cause free radicals to be generated too quickly, resulting in a decrease in the degree of polymerization.

[0034] Furthermore, the initiator is selected from one or more of ammonium persulfate, sodium persulfate or potassium persulfate. The cross-linking agent is used to connect two molecular chains to form a network structure to form a hydrogel. Too low a content causes the hydrogel to be unformed, and too high a content causes the hydrogel network to be too tight, affecting the adsorption of calcium ions.

[0035] Furthermore, in step (S3), during the polymerization reaction, the temperature is 50-70° C. (under this temperature condition, the free radical polymerization reaction can proceed at a certain speed to avoid the reaction being too fast or too slow), and the time is 60-120 min;

[0036] Preferably, during the polymerization reaction, the temperature is 65° C. and the time is 60 min.

[0037] The present invention provides a hydrogel with calcium ion adsorption function prepared by the above method;

[0038] In the hydrogel, sodium acrylate and sodium vinyl phosphate, as functional monomers, have a good adsorption effect on calcium ions;

[0039] Styrene is used to increase the hardness of the hydrogel and facilitate its use.

[0040] The invention provides application of a hydrogel with calcium ion adsorption function in water softening.

[0041] The present invention is described in detail below with reference to specific embodiments.

[0042] In the following examples, unless otherwise specified, all reagents used are commercially available reagents, and all detection means and methods used are conventional detection means and methods in the art.

[0043] Specifically, the compounds used in the following examples are as follows:

[0044] Acrylic acid (CAS No. 79-10-7), sodium hydroxide (CAS No. 1310-73-2), sodium vinyl phosphate (CAS No. 1746-03-8), potassium persulfate (CAS No. 7727-21-1), N,N'-methylenebisacrylamide (CAS No. 110-26-9), styrene (CAS No. 100-42-5), Tween 80 (CAS No. 9005-65-6).

[0045] The determination method of calcium ion adsorption by hydrogel is as follows:

[0046] 0.1 g of crushed hydrogel particles was placed in 20 ml of 0.1 mol / L calcium chloride solution, mixed and shaken for 30 minutes, and then the calcium ion concentration in the solution was measured using a calcium ion potentiometer to obtain the amount of calcium ions adsorbed by the hydrogel.

[0047] Example 1

[0048] This embodiment provides a hydrogel with calcium ion adsorption function and a preparation method thereof, comprising the following steps:

[0049] 1.7 g of acrylic acid and 2.5 g of vinyl phosphoric acid were mixed, and 8.8 ml of 8 mol / L sodium hydroxide solution was added for neutralization to obtain a functional monomer solution. Then, 0.1 g of N,N'-methylenebisacrylamide and 0.1 g of potassium persulfate were added and dissolved to form a mixed solution. Subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 2.4 g of styrene were added, the mixture was evenly mixed, and the mixture was heated in a 65°C water bath to initiate a free radical polymerization reaction. After reacting for 1 hour, the mixture was washed to obtain a hydrogel with calcium ion adsorption function.

[0050] The hydrogel obtained in this example has an adsorption capacity of calcium ions of 91 mg / g.

[0051] Example 2

[0052] This embodiment provides a hydrogel with calcium ion adsorption function and a preparation method thereof, comprising the following steps:

[0053] After mixing 2.7 g of acrylic acid and 2.0 g of vinyl phosphoric acid, 9.4 ml of 8 mol / L sodium hydroxide solution was added for neutralization to obtain a functional monomer solution, and then 0.1 g of N, N'-methylenebisacrylamide and 0.1 g of potassium persulfate were added and dissolved to form a mixed solution; subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 1.9 g of styrene were added, mixed evenly, and heated in a 65°C water bath to induce a free radical reaction. After reacting for 1 hour, the mixture was washed to obtain the desired hydrogel.

[0054] The hydrogel obtained in this example has an adsorption capacity of 112 mg / g for calcium ions.

[0055] In this embodiment, the molar ratio of acrylic acid to vinyl phosphate is 2:1. The carboxyl groups of two acrylic acids are similar to one phosphate group, thereby obtaining a diphosphate structure. The hydrogel formed by this structure can significantly improve the adsorption capacity of calcium ions.

[0056] Example 3

[0057] This embodiment provides a hydrogel with calcium ion adsorption function and a preparation method thereof, comprising the following steps:

[0058] After mixing 3.8 g of acrylic acid and 1.4 g of vinyl phosphoric acid, 10 ml of 8 mol / L sodium hydroxide solution was added for neutralization to obtain a functional monomer solution, and then 0.1 g of N, N'-methylenebisacrylamide and 0.1 g of potassium persulfate were added and dissolved to form a mixed solution; subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 1.4 g of styrene were added, mixed evenly, and then heated in a 65°C water bath to induce a free radical reaction. After reacting for 1 hour, the mixture was washed to obtain the desired hydrogel.

[0059] The hydrogel obtained in this example has an adsorption capacity of 103 mg / g for calcium ions.

[0060] Example 4

[0061] This embodiment provides a hydrogel with calcium ion adsorption function and a preparation method thereof, comprising the following steps:

[0062] 4.5 g of acrylic acid and 1.1 g of vinyl phosphoric acid were mixed, and then 10.4 ml of 8 mol / L sodium hydroxide solution was added for neutralization. Then, 0.1 g of N,N'-methylenebisacrylamide and 0.1 g of potassium persulfate were added and dissolved to form a mixed solution. Subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 1.1 g of styrene were added, the mixture was evenly mixed, and the mixture was heated in a 65°C water bath to induce a free radical reaction. After the reaction lasted for 1 hour, the mixture was washed to obtain the desired hydrogel.

[0063] The hydrogel obtained in this example has an adsorption capacity of 87 mg / g for calcium ions.

[0064] Comparative Example 1 (without sodium vinyl phosphate)

[0065] This comparative example provides a hydrogel and a preparation method thereof, comprising the following steps:

[0066] To 3.9 g of acrylic acid, 6.7 ml of 8 mol / L sodium hydroxide solution was added to neutralize to obtain a functional monomer solution, and then 0.1 g of N,N'-methylenebisacrylamide and 0.1 g of potassium persulfate were dissolved to form a mixed solution; subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 2.8 g of styrene were added, the mixture was evenly mixed and heated in a 65°C water bath to induce a free radical reaction. After reacting for 1 hour, the mixture was washed to obtain the desired hydrogel.

[0067] The adsorption capacity of calcium ions by the hydrogel obtained in this comparative example is 73 mg / g.

[0068] The amount of calcium ion adsorption by the hydrogel obtained in this comparative example is less than that in the above-mentioned embodiments, especially significantly less than the amount of calcium ion adsorption by the hydrogel in Example 2, which is 112 mg / g.

[0069] Comparative Example 2 (Excess Styrene)

[0070] This comparative example provides a hydrogel with calcium ion adsorption function and a preparation method thereof, comprising the following steps:

[0071] After mixing 2.1 g of acrylic acid and 1.6 g of vinyl phosphoric acid, 7.3 ml of 8 mol / L sodium hydroxide solution was added for neutralization to obtain a functional monomer solution, and then 0.1 g of N, N'-methylenebisacrylamide and 0.1 g of potassium persulfate were dissolved to form a mixed solution; subsequently, Tween 80 (the mass percentage was 0.5% of the functional monomer solution) and 3 g of styrene were added, the mixture was evenly mixed and heated in a 65°C water bath to induce a free radical reaction. After reacting for 1 hour, the mixture was washed to obtain the desired hydrogel.

[0072] The adsorption capacity of calcium ions by the hydrogel obtained in this comparative example is 95 mg / g.

[0073] In this comparative example, the molar ratio of acrylic acid: vinyl phosphoric acid: styrene is 2:1:2. Compared with the molar ratio of 2:1:1 in Example 2, styrene is excessive. Since styrene is only slightly soluble in aqueous acrylic acid solution, the addition of too much styrene will affect the polymerization of acrylic acid and vinyl phosphoric acid to a certain extent, thereby reducing the adsorption of calcium ions by the formed hydrogel.

[0074] Comparative Example 3 (no styrene)

[0075] This comparative example provides a hydrogel and a preparation method thereof, comprising the following steps:

[0076] After mixing 3.8 g of acrylic acid and 2.9 g of vinyl phosphoric acid, 13.3 ml of 8 mol / L sodium hydroxide solution was added for neutralization to obtain a functional monomer solution, and then 0.1 g of N,N'-methylenebisacrylamide and 0.1 g of potassium persulfate were dissolved to form a mixed solution; then, it was placed in a 65°C water bath and heated to induce a free radical reaction; after reacting for 1 hour, it was washed to obtain the desired hydrogel.

[0077] The adsorption capacity of calcium ions by the hydrogel obtained in this comparative example is 104 mg / g.

[0078] Although the hydrogel obtained in this comparative example has a high calcium ion adsorption function, the hydrogel is not formed, which affects its use.

[0079] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the explanation of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a hydrogel having calcium ion adsorption function, It is characterized in that The following steps are involved: (S1) mixing sodium acrylate and sodium vinyl phosphate to obtain a first mixed solution; (S2) adding a crosslinking agent, an initiator and styrene to the first mixed solution obtained in step (S1) to obtain a second mixed solution; (S3) initiating a polymerization reaction of the second mixed solution obtained in step (S2) to obtain a hydrogel having a calcium ion adsorption function.

2. A method for preparing a hydrogel having calcium ion adsorption function according to claim 1, It is characterized in that In step (S1), the molar ratio of sodium acrylate to sodium vinyl phosphate is 1 to 6:

1.

3. A method for preparing a hydrogel having calcium ion adsorption function according to claim 2, It is characterized in that The molar ratio of sodium acrylate to sodium vinyl phosphate is 2:

1.

4. The method for preparing a hydrogel having calcium ion adsorption function according to claim 1, It is characterized in that In step (S2), the mass ratio of the first mixed solution, the cross-linking agent, and the initiator is 1:0.002-0.02:0.001-0.003; The molar ratio of styrene to sodium acrylate is 1:1-6.

5. The method for preparing a hydrogel having calcium ion adsorption function according to claim 3, It is characterized in that The cross-linking agent is selected from one of N,N'-methylenebisacrylamide and N-hydroxymethylacrylamide.

6. The method for preparing a hydrogel having calcium ion adsorption function according to claim 3, It is characterized in that The initiator is selected from one or more of ammonium persulfate, sodium persulfate or potassium persulfate.

7. The method for preparing a hydrogel having calcium ion adsorption function according to claim 1, It is characterized in that In step (S3), during the polymerization reaction, the temperature is 50-70° C. and the time is 60-120 min.

8. The method for preparing a hydrogel having calcium ion adsorption function according to claim 7, It is characterized in that During the polymerization reaction, the temperature was 65°C and the time was 60 min.

9. A hydrogel having calcium ion adsorption function prepared by the method according to any one of claims 1 to 8.

10. Use of the hydrogel with calcium ion adsorption function as claimed in claim 9 in water softening.