Sulfydryl-modified sodium alginate calcium ion imprinted microspheres as well as preparation method and application thereof

Abstract

The invention discloses sulfydryl-modified sodium alginate calcium ion imprinted microspheres as well as a preparation method and application thereof, and belongs to the technical field of circulating cooling water treatment. The preparation method comprises the following steps: slowly dropwise adding a sodium alginate solution into a calcium salt solution, carrying out cross-linking solidification, collecting a solid, washing with deionized water, modifying with mercaptoacetic acid, completely eluting combined calcium ions with hydrochloric acid to obtain a modified sodium alginate calcium ion imprinting material, pre-freezing with liquid nitrogen, and carrying out vacuum freeze drying to obtain the required material. The calcium ion imprinted microspheres obtained by adopting sodium alginate as a raw material have rich pore structures, have very excellent adsorption capacity and selectivity on calcium ions, can effectively delay scaling of circulating cooling water, and are good in settling performance, easy to recover and free of any harm to the environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of circulating cooling water treatment, and particularly relates to a mercapto-modified sodium alginate calcium ion-imprinted microsphere, its preparation method and application. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Circulating cooling water is widely used in industrial production. It can recycle water resources and improve water utilization efficiency. However, with the increase of usage time, scale problems often occur in circulating cooling water. The accumulation of scale will reduce the efficiency of the circulating water system, increase energy consumption, and even cause equipment damage. Therefore, it is particularly important to solve the scale problem of circulating cooling water.

[0004] The main components of the scale in circulating cooling water are calcium carbonate, etc. If the calcium ions in the circulating cooling water can be removed in time, the formation of scale in the circulating cooling water can be effectively inhibited.

[0005] Ion imprinting technology is an adsorbent preparation technology developed on the basis of molecular imprinting technology in the past two decades. The adsorbent prepared by ion imprinting technology has the advantages of large adsorption capacity, selectivity, etc., and can be desorbed and regenerated, and still maintain quite stable performance after being reused multiple times. Patent CN115193425A discloses an ion-imprinted modified porous sodium alginate microsphere material, which is used to remove copper and tetracycline in water, rather than adsorb calcium ions, and cannot be used for scale inhibition of circulating cooling water.

[0006] Therefore, it is of great significance to develop an ion-imprinted modified microsphere material that can adsorb a large amount of calcium ions in water for scale inhibition of circulating cooling water. Summary of the Invention

[0007] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a mercapto-modified sodium alginate calcium ion-imprinted microsphere, its preparation method and application. The mercapto-modified sodium alginate calcium ion-imprinted microsphere provided by the present invention has a rich pore structure, a very large adsorption capacity for calcium ions, good sedimentation performance, and is easy to recycle when used as a calcium ion adsorbent.

[0008] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0009] In the first aspect of the present invention, a mercapto-modified sodium alginate calcium ion-imprinted microsphere is provided, which is obtained by mercapto-modifying a calcium alginate microsphere;

[0010] The calcium alginate microspheres are prepared by cross-linking sodium alginate and calcium salt.

[0011] In the present invention, ion imprinting technology is utilized. Calcium alginate microspheres are prepared by cross-linking sodium alginate and calcium salt. There are a large number of functional groups on the surface of the microspheres. Through mercapto modification, some hydroxyl groups are converted into mercapto groups, and mercapto-modified sodium alginate calcium ion imprinted microspheres with high calcium ion adsorption capacity are obtained. The mercapto-modified sodium alginate calcium ion imprinted microspheres provided by the present invention have a rich pore structure, have a very large adsorption capacity for calcium ions, have excellent scale inhibition effect, and have good sedimentation performance, and are easy to recover when used as a calcium ion adsorbent in circulating cooling water.

[0012] In some embodiments of the present invention, the particle size of the mercapto-modified sodium alginate calcium ion imprinted microspheres is 2 - 5 mm, preferably 3 - 4 mm.

[0013] In some embodiments of the present invention, the mercapto-modified sodium alginate calcium ion imprinted microspheres are of a porous structure and have wrinkles on the surface.

[0014] It can be understood that the pore and wrinkle structures endow the mercapto-modified sodium alginate calcium ion imprinted microspheres with a large specific surface area and improve their adsorption capacity for calcium ions.

[0015] In the second aspect of the present invention, a preparation method of the above-mentioned mercapto-modified sodium alginate calcium ion imprinted microspheres is provided, including:

[0016] Dripping the sodium alginate solution into the calcium salt solution, and after the dripping is completed, mixing and reacting to obtain calcium alginate microspheres;

[0017] Placing the calcium alginate microspheres in thioglycolic acid, adding a catalyst, mixing and reacting, and after the reaction is completed, washing and freeze-drying to obtain mercapto-modified sodium alginate calcium ion imprinted microspheres.

[0018] In some embodiments of the present invention, the preparation method of the sodium alginate solution includes dissolving sodium alginate in water, stirring to completely dissolve it, and ultrasonically removing bubbles to obtain the sodium alginate solution.

[0019] In some embodiments of the present invention, the concentration of the sodium alginate solution is 1 - 5 wt%, specifically, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0020] In some embodiments of the present invention, the concentration of the calcium salt solution is 5 - 10 wt%, specifically, it can be 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.

[0021] The solvents of the sodium alginate solution and the calcium salt solution are both water, rather than organic solvents, which greatly reduces the cost and environmental hazards.

[0022] In some embodiments of the present invention, the mass ratio of the sodium alginate solution to the calcium salt solution is 0.9 - 1.1:0.9 - 1.1, preferably 1:1.

[0023] In some embodiments of the present invention, the calcium salt includes, but is not limited to, any one or more of calcium carbonate, calcium chloride, and dicalcium hydrogen phosphate.

[0024] In some embodiments of the present invention, the calcium salt is calcium chloride, preferably anhydrous calcium chloride.

[0025] In some embodiments of the present invention, the sodium alginate solution is added dropwise to the calcium salt solution. After the addition is complete, it is placed in a shaker at 25 - 35°C and reacted at 100 - 200 rpm for 20 - 25 h to obtain calcium alginate microspheres.

[0026] In some embodiments of the present invention, after the reaction is completed, the calcium alginate microspheres are filtered and the unbound calcium ions on the surface are removed with water.

[0027] In some embodiments of the present invention, the catalyst is concentrated sulfuric acid.

[0028] In some embodiments of the present invention, the calcium alginate microspheres are placed in mercaptoacetic acid. After adding the catalyst, it is placed in a shaker at 25 - 35°C and reacted at 100 - 200 rpm for 20 - 25 h. Then, it is eluted with hydrochloric acid solution three times, each time for 10 - 15 h. The obtained product is freeze-dried to obtain mercapto-modified sodium alginate calcium ion imprinted microspheres.

[0029] In some embodiments of the present invention, the mercaptoacetic acid is a 1 - 5 v% aqueous solution of mercaptoacetic acid.

[0030] It should be noted that the concentration of mercaptoacetic acid in the aqueous solution of mercaptoacetic acid is a volume percentage, that is, the volume of mercaptoacetic acid is 1 - 5% of the total volume of the aqueous solution of mercaptoacetic acid.

[0031] In some embodiments of the present invention, the concentration of the hydrochloric acid solution is 0.9 - 1.1 M.

[0032] The third aspect of the present invention provides an application of the above-mentioned mercapto-modified sodium alginate calcium ion imprinted microspheres or the mercapto-modified sodium alginate calcium ion imprinted microspheres prepared by the above-mentioned preparation method in scale inhibition of circulating cooling water.

[0033] In some embodiments of the present invention, the application is that the mercapto-modified sodium alginate calcium ion imprinted microspheres are used as adsorbents to adsorb calcium ions in circulating cooling water.

[0034] The beneficial effects of the present invention are as follows:

[0035] The present invention provides a mercapto-modified sodium alginate calcium ion imprinted microsphere, which has a rich pore structure, surface wrinkles, a large specific surface area, and a large number of mercapto functional groups on the surface. It has a very large adsorption capacity for calcium ions and is applied to the scale inhibition of circulating cooling water, which can effectively delay the scaling of circulating cooling water and has excellent scale inhibition effect. The microsphere has good sedimentation performance and is easy to recycle when used as an adsorbent for calcium ions, and has no harm to the environment.

[0036] In the preparation process of the microsphere provided by the present invention, water is used as the main solvent, which greatly reduces the cost and reduces the environmental harm. At the same time, sodium alginate, as the main material, can be completely degraded, is a green biodegradable material, and has environmental friendliness. Description of the Drawings

[0037] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0038] Figure 1 are scanning electron microscope images of the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1 of the present invention at different magnification multiples;

[0039] Figure 2 are the adsorption kinetic curves of the microspheres obtained in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention; among them, A is the adsorption kinetic curve of the microspheres obtained in Comparative Example 1 and Comparative Example 2, B is the adsorption kinetic curve of the microspheres obtained in Example 1 and Comparative Example 1; C is the adsorption kinetic curve of the microspheres obtained in Example 1 at different initial calcium ion concentrations; D is the adsorption kinetic curve when the dosage of the microspheres obtained in Example 1 is changed;

[0040] Figure 3 shows the selective adsorption of the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1 of the present invention in a multi-ion mixed solution;

[0041] Figure 4 shows the change of the titration scale formation point after the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1 of the present invention simulates the treatment of circulating cooling water; among them, A is the titration experimental curve of circulating cooling water at 1-fold concentration, B is the titration experimental curve of circulating cooling water at 2-fold concentration, C is the titration experimental curve of circulating cooling water at 3-fold concentration, D is the titration experimental curve of circulating cooling water after being treated with SA-TGA-Ca at 1-fold concentration, E is the titration experimental curve of circulating cooling water after being treated with SA-TGA-Ca at 2-fold concentration, and F is the titration experimental curve of circulating cooling water after being treated with SA-TGA-Ca at 3-fold concentration. Detailed implementation manners

[0042] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0043] Among them, the raw materials or reagents used in the following examples are all purchased commercially.

[0044] Example 1

[0045] A preparation method of a mercapto-modified sodium alginate calcium ion imprinted microsphere, comprising the following steps:

[0046] (1) Dissolve 2 g of sodium alginate in 98 mL of deionized water, and mechanically stir until the sodium alginate is completely dissolved to obtain a 2 wt% sodium alginate solution, and then ultrasonically treat for 2 h to remove the bubbles in the solution. Then dissolve 7 g of anhydrous calcium chloride in 93 mL of water to prepare a 7 wt% calcium ion cross-linking solution.

[0047] (2) Slowly drop the 2 wt% sodium alginate solution into the 7 wt% calcium ion cross-linking solution with a 10 mL syringe. After the dropping is completed, place it in a shaker at 30 °C and react at 150 rpm for 24 h to obtain calcium alginate microspheres, and then wash with deionized water to fully remove the unbound calcium ions on the surface of the microspheres.

[0048] (3) Place the obtained 20 g of calcium alginate microspheres in 100 mL of a 4 v% aqueous solution of mercaptoacetic acid, and add 40 μL of concentrated sulfuric acid as a catalyst. Place it in a shaker at 30 °C and react at 150 rpm for 24 h. Then elute with 100 mL of 1 M hydrochloric acid solution three times, each time for 12 h. The obtained product is pre-frozen with liquid nitrogen and freeze-dried to obtain a mercapto-modified sodium alginate calcium ion imprinted microsphere, which is named SA-TGA-Ca.

[0049] Figure 1 It is a scanning electron microscope picture of the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1. From Figure 1 it can be seen that the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1 is a microsphere with surface wrinkles and has a very rich pore structure. The particle size of the mercapto-modified sodium alginate calcium ion imprinted microsphere prepared in Example 1 is between 3 - 4 mm.

[0050] Example 2

[0051] A preparation method of a mercapto-modified sodium alginate calcium ion imprinted microsphere, which is different from Example 1 in that the concentration of the sodium alginate solution is 1 wt%, and the remaining steps are the same as those in Example 1.

[0052] Example 3

[0053] A preparation method of mercapto-modified sodium alginate calcium ion imprinted microspheres, which is different from Example 1 in that the concentration of the sodium alginate solution is 5 wt%, and the remaining steps are the same as those in Example 1.

[0054] Example 4

[0055] A preparation method of mercapto-modified sodium alginate calcium ion imprinted microspheres, which is different from Example 1 in that the concentration of the calcium ion cross-linking solution is 5 wt%, and the remaining steps are the same as those in Example 1.

[0056] Example 5

[0057] A preparation method of mercapto-modified sodium alginate calcium ion imprinted microspheres, which is different from Example 1 in that the concentration of the calcium ion cross-linking solution is 10 wt%, and the remaining steps are the same as those in Example 1.

[0058] It was verified that the particle size of the mercapto-modified sodium alginate calcium ion imprinted microspheres obtained in Examples 2-5 was 1-5 mm, and the performance was similar to that of the microspheres obtained in Example 1. They all had excellent calcium ion adsorption performance and could be used as calcium ion adsorbents in circulating cooling water.

[0059] Comparative Example 1

[0060] A preparation method of sodium alginate calcium ion imprinted microspheres includes the following steps:

[0061] (1) Dissolve 2 g of sodium alginate in 98 mL of deionized water, and mechanically stir until the sodium alginate is completely dissolved to prepare a 2 wt% sodium alginate solution. Then, ultrasonicate for 2 h to remove the bubbles in the solution. Then dissolve 7 g of anhydrous calcium chloride in 93 mL of water to prepare a 7 wt% calcium ion cross-linking solution;

[0062] (2) Slowly drop the 2 wt% sodium alginate solution into the 7 wt% calcium ion cross-linking solution with a 10 mL syringe. After the dropping is completed, place it in a shaker at 30 °C and incubate at 150 rpm for 24 h to obtain calcium alginate microspheres. After filtration, use deionized water to remove the unbound calcium ions on the surface of the microspheres;

[0063] (3) Elute with 100 mL of 1 M hydrochloric acid solution three times, each time for 12 h. The obtained product is pre-frozen with liquid nitrogen and freeze-dried to obtain sodium alginate calcium ion imprinted microspheres, which are named SA-Ca.

[0064] Comparative Example 2

[0065] A preparation method of non-ion imprinted sodium alginate microspheres includes the following steps:

[0066] (1) Dissolve 2 g of sodium alginate in 98 mL of deionized water, and mechanically stir until the sodium alginate is completely dissolved to obtain a 2 wt% sodium alginate solution. Then, ultrasonicate for 2 h to remove the bubbles in the solution.

[0067] (2) Slowly drip the 2 wt% sodium alginate solution into 100 mL of 1 M hydrochloric acid solution using a 10 mL syringe. After the dripping is completed, place it in a shaker at 30 °C and oscillate at 150 rpm for 24 h to obtain sodium alginate microspheres. Then, remove the unbound hydrochloric acid on the surface of the microspheres with deionized water. After filtration, elute with 100 mL of 1 M hydrochloric acid solution three times, 12 h each time. The obtained product is pre-frozen in liquid nitrogen and freeze-dried to obtain non-ion imprinted sodium alginate microspheres, which are named SA-H.

[0068] Experimental Example 1

[0069] Verification of SA-TGA-Ca modification

[0070] Copper ions can combine with free mercaptoacetic acid in water, causing the solution to change color. Although the mercapto groups successfully grafted on the surface of SA-TGA-Ca can combine with copper ions, they will not cause the solution color to change. Based on this characteristic, after drying the SA-TGA-Ca prepared in Example 1 in this experimental example, take 0.01 g of the dried SA-TGA-Ca and place it in 100 mL of 1 M copper chloride aqueous solution. It was found that the solution did not change color, indicating that SA-TGA-Ca has been washed clean and its surface does not contain free mercaptoacetic acid, and the surface functional groups of the prepared SA-TGA-Ca have been modified to mercapto groups.

[0071] Experimental Example 2

[0072] Detection of the maximum adsorption capacity and adsorption rate of calcium ions

[0073] Use the microspheres obtained in Example 1, Comparative Example 1, and Comparative Example 2 as adsorbents to conduct adsorption kinetics experiments. Accurately weigh multiple portions of 0.1 g of SA-TGA-Ca, SA-Ca, and SA-H using a high-precision electronic balance, and place them in 50 mL centrifuge tubes respectively. Then, add 30 mL of calcium ion solution with a concentration of 100 mg / L in sequence. The adsorption time is set to 10, 30, 60, 120, 240, 480, 600, 960, 1440 min. After adsorption, filter the solution through a 0.45 μm filter membrane, detect the concentration of calcium ions in the filtrate with an ICP-OES instrument, and calculate the adsorption capacity of the calcium ion imprinted polymer.

[0074] The adsorption rates and maximum adsorption capacities of SA-TGA-Ca, SA-Ca, and SA-H are as Figure 2As shown in Figures A and B, SA-H has no obvious calcium ion adsorption performance, the adsorption capacity of SA-Ca is about 13 mg / g, and the adsorption capacity of SA-TGA-Ca is increased to 16 mg / g.

[0075] Experimental Example 3

[0076] Determination of the maximum adsorption capacity of SA-TGA-Ca at different initial calcium ion concentrations

[0077] Using the microspheres obtained in Example 1 as adsorbents, adsorption kinetics experiments were carried out. Multiple portions of 0.1 g of SA-TGA-Ca were accurately weighed using a high-precision electronic balance and placed in 50 mL centrifuge tubes respectively. 30 mL of calcium ion solutions with different concentrations were added successively. The initial concentrations of calcium ions were set to 0, 100, 200, 400, 600, 800, 1000 mg / L. The adsorbed solutions were filtered through a 0.45 μm filter membrane, and the concentration of calcium ions in the filtrate was detected by an ICP-OES instrument, and the adsorption capacity of the calcium ion imprinted polymer was calculated through calculation.

[0078] In calcium ion solutions with different concentrations, the maximum adsorption capacity of SA-TGA-Ca is as Figure 2 shown in Figure C. When the initial concentration of calcium ions is 200 mg / L, the maximum adsorption capacity of SA-TGA-Ca is 17 mg / g. As the initial concentration increases from 100 mg / L to 1000 mg / L, the adsorption capacity increases from 15 mg / g to 22 mg / g.

[0079] Experimental Example 4

[0080] The maximum adsorption capacity of the adsorbent at different dosages of SA-TGA-Ca

[0081] Using the microspheres obtained in Example 1 as adsorbents, adsorption kinetics experiments were carried out. Multiple portions of 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14 g of SA-TGA-Ca were accurately weighed using a high-precision electronic balance and placed in 50 mL centrifuge tubes respectively. 20 mL of 100 mg / L calcium ion solution was added successively to obtain calcium ion solutions with different adsorbent concentrations. The concentrations of the adsorbents were converted to 1, 2, 3, 4, 5, 6, 7 g / L respectively. The adsorbed solutions were filtered through a 0.45 μm filter membrane, and the concentration of calcium ions in the filtrate was detected by an ICP-OES instrument, and the adsorption capacity of the calcium ion imprinted polymer was calculated through calculation.

[0082] In calcium ion solutions with different adsorbent concentrations, the maximum adsorption capacity of SA-TGA-Ca is as Figure 2As shown in Figure D, when the concentration of SA-TGA-Ca was 1 g / L, the maximum adsorption capacity was 32.2 mg / g. As the concentration of SA-TGA-Ca increased, the adsorption capacity of SA-TGA-Ca gradually decreased, and the removal efficiency of calcium ions increased from 32% to 56%.

[0083] Experimental Example 5

[0084] Selective adsorption test of SA-TGA-Ca

[0085] Using the SA-TGA-Ca obtained in Example 1 as an adsorbent, an adsorption kinetics experiment was conducted. 0.2 g of SA-TGA-Ca was accurately weighed using a high-precision electronic balance and placed in a 50 mL centrifuge tube. 30 mL of a multi-ion mixed solution containing sodium, potassium, calcium, and magnesium ions with a concentration of 100 mg / L for each ion was added. After adsorption for 24 h, the adsorbed solution was filtered through a 0.45 μm filter membrane, and the concentrations of various ions in the filtrate were detected using an ICP-OES instrument, and the adsorption capacity of each ion-imprinted polymer was calculated.

[0086] The results are as Figure 3 shown. SA-TGA-Ca can selectively adsorb calcium ions, and its adsorption capacity for calcium ions is much higher than that of other ions.

[0087] Experimental Example 6

[0088] From the perspectives of economy and environmental protection, the SA-TGA-Ca obtained in Example 1 was selected as an adsorbent to simulate the scale inhibition experiment of circulating cooling water.

[0089] Referring to GB / T 18175—2014, circulating cooling water was prepared. The concentration of the un-concentrated circulating cooling water was set at 1.0C. Subsequently, circulating cooling water with concentrations of 2.0C and 3.0C was prepared and added to a 500 mL conical flask. The amount of circulating cooling water used was 250 mL, and 3.0 g of SA-TGA-Ca was added as an adsorbent for treatment. It was oscillated at 150 rpm at 30 °C for 24 h. After solid-liquid separation, a titration method was used, and 0.1 M Na2CO3 was used to infer the scale formation points of circulating cooling water under different conditions.

[0090] The experimental results obtained are as Figure 4 shown in Figures D, E, and F. The titration experiment results of the circulating cooling water without SA-TGA-Ca treatment are as Figure 4 shown in Figures A, B, and C. At a circulating cooling water concentration of 1 times ( Figure 4 Figure A), only 4 mL of sodium carbonate was added, and the entire system showed scale formation, and the scale formation trend was very obvious. For the circulating cooling water without SA-TGA-Ca treatment, as the concentration increased, the amount of sodium carbonate added decreased from the initial 4 mL to 2 mL (Figure 4 In B and Figure 4 In C), it shows that higher concentration of circulating cooling water is more prone to scaling. At 1-fold concentration, the dropping amount of sodium carbonate in the circulating cooling water after being treated with SA-TGA-Ca is 34 mL ( Figure 4 In D), which is 8.5 times that of the circulating cooling water without adsorbent treatment, and its scaling tendency is significantly weaker than that of the circulating cooling water without adsorbent treatment. As Figure 4 shown in Figures D, E and F in it, with the increase of the concentration of circulating cooling water, the dropping amount of sodium carbonate in the circulating cooling water after being treated with SA-TGA-Ca decreases from 34 mL to 16 mL, but its scaling tendency is significantly weaker than that of the circulating cooling water without SA-TGA-Ca treatment. At 3-fold concentration of circulating cooling water ( Figure 4 In F), the dropping amount of sodium carbonate in the circulating cooling water after being treated with SA-TGA-Ca is 8 times that of the untreated circulating cooling water, indicating that SA-TGA-Ca still has excellent scale inhibition effect even in high-concentration circulating cooling water.

[0091] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thiol-modified sodium alginate calcium ion imprinted microsphere, characterized in that, It is obtained by thiol modification of calcium alginate microspheres; The calcium alginate microspheres are prepared by cross-linking sodium alginate and calcium salts.

2. The thiol-modified sodium alginate calcium ion imprinted microspheres according to claim 1, characterized in that, The particle size of the thiol-modified sodium alginate calcium ion imprinted microspheres is 2 - 5 mm.

3. The thiol-modified sodium alginate calcium ion imprinted microspheres according to claim 1, wherein The thiol-modified sodium alginate calcium ion imprinted microspheres have a porous structure and wrinkles on the surface.

4. A method for preparing the mercapto-modified sodium alginate calcium ion imprinted microspheres according to any one of claims 1-3, characterized in that, It includes: Drop the sodium alginate solution into the calcium salt solution. After dropping, mix and react to obtain calcium alginate microspheres; Place the calcium alginate microspheres in thioglycolic acid, add a catalyst, mix and react. After the reaction, wash and freeze-dry to obtain thiol-modified sodium alginate calcium ion imprinted microspheres.

5. The preparation method according to claim 4, characterized in that, The preparation method of the sodium alginate solution includes dissolving sodium alginate in water, stirring to completely dissolve it, and ultrasonically removing bubbles to obtain the sodium alginate solution.

6. The preparation method according to claim 4, characterized in that, The concentration of the sodium alginate solution is 1 - 5 wt%; Preferably, the concentration of the calcium salt solution is 5 - 10 wt%; Preferably, the mass ratio of the sodium alginate solution to the calcium salt solution is 0.9 - 1.1:0.9 - 1.

1.

7. The preparation method according to claim 4, characterized in that, The calcium salt includes any one or more of calcium carbonate, calcium chloride, and dibasic calcium phosphate; Preferably, the calcium salt is calcium chloride.

8. The preparation method according to claim 4, wherein, Drop the sodium alginate solution into the calcium salt solution. After dropping, place it in a shaker at 25 - 35 °C and react at 100 - 200 rpm for 20 - 25 h to obtain calcium alginate microspheres; Preferably, after the reaction, filter and use water to remove the unbound calcium ions on the surface of the calcium alginate microspheres.

9. The preparation method according to claim 4, characterized in that, The catalyst is concentrated sulfuric acid; Preferably, place the calcium alginate microspheres in thioglycolic acid, add a catalyst, then place it in a shaker at 25 - 35 °C and react at 100 - 200 rpm for 20 - 25 h, and then elute with hydrochloric acid solution three times, each time for 10 - 15 h. The obtained product is freeze-dried to obtain thiol-modified sodium alginate calcium ion imprinted microspheres; Preferably, the thioglycolic acid is a 1 - 5 v% aqueous solution of thioglycolic acid; Preferably, the concentration of the hydrochloric acid solution is 0.9 - 1.1 M.

10. Application of the thiol-modified sodium alginate calcium ion imprinted microspheres according to any one of claims 1 - 3 or the thiol-modified sodium alginate calcium ion imprinted microspheres prepared by the preparation method according to any one of claims 4 - 9 in scale inhibition of circulating cooling water; Preferably, the application is that the thiol-modified sodium alginate calcium ion imprinted microspheres are used as adsorbents to adsorb calcium ions in circulating cooling water.

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