A particulate aluminum chloride hydrogel adsorbent and a preparation method thereof, and a method for removing sulfate ions from water

Abstract

The application provides a granular aluminum chloride hydrogel adsorbent and a preparation method thereof and a method for removing sulfate ions in water, and relates to the technical field of water treatment. The granular aluminum chloride hydrogel adsorbent is introduced into water together with calcium ions, so that the sulfate ions to be removed in water combine with the introduced calcium ions into a solid with small solubility, and the solid is separated from water. The granular hydrogel is used to load small-particle aluminum chloride, and the granular hydrogel has large specific surface area, good adsorption and strong stability, so that the granular hydrogel is used as an adsorbent to adsorb the insoluble solid formed by the combination of calcium ions and sulfate ions, and the removal efficiency of the sulfate ions is further improved. Meanwhile, part of the sulfate ions combines with calcium ions and aluminum ions to form a complex such as Al2Ca3(SO4)6, and the complex is fixed on the surface and inside of the hydrogel colloid, so that the removal rate is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a granular aluminum chloride hydrogel adsorbent, its preparation method, and a method for removing sulfate ions from water. Background Technology

[0002] Currently, with the continuous acceleration of urbanization and the rapid development of industry and agriculture, the sulfate ion concentration in water bodies has increased significantly. Its main sources are human pollution, oxidation of sulfides, and dissolution of some sulfate sedimentary rocks, resulting in high permanent hardness and high mineralization in water. This has an increasing impact on water treatment and makes it a relatively difficult ion to remove.

[0003] Existing methods for sulfate ion removal mainly include membrane separation, ion exchange resins, biological treatment, and chemical precipitation. Among these, membrane separation and ion exchange resins are costly, biological treatment suffers from operational instability, and chemical precipitation is simple to operate and stable. However, general chemical precipitation methods have low sulfate ion removal rates, making it essential to find a chemical precipitation method with high removal efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a granular aluminum chloride hydrogel adsorbent, its preparation method, and a method for removing sulfate ions from water. Using the adsorbent provided by this invention, combined with a specific method, sulfate ions can be efficiently removed from water.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The present invention provides a granular aluminum chloride hydrogel adsorbent, comprising hydrogel particles and aluminum chloride particles loaded on the hydrogel particles; the hydrogel comprises gelatin and agar.

[0007] Preferably, the hydrogel particles have a particle size of 1.8–2.6 cm; the aluminum chloride particles have a particle size ≤1.3 mm.

[0008] Preferably, the mass ratio of the hydrogel particles to the aluminum chloride particles is (47.2-48.4):1.

[0009] Preferably, the mass ratio of gelatin to agar is (5.7-5.8):1.

[0010] This invention provides a method for preparing the granular aluminum chloride hydrogel adsorbent described above, comprising the following steps: dissolving gelatin and agar in water to obtain a mixture;

[0011] Aluminum chloride particles are dispersed into the mixture, and the resulting dispersion is poured into a mold to form a gel. After drying, the granular aluminum chloride hydrogel adsorbent is obtained.

[0012] This invention provides a method for removing sulfate ions from water, comprising the following steps: adding a calcium ion reagent to wastewater containing sulfate ions, then adjusting the pH of the wastewater to 7.8-9.2, and finally adding granular aluminum chloride hydrogel adsorbent, mixing and adsorbing under stirring conditions, allowing to stand, and separating the solid and liquid.

[0013] Preferably, the calcium ion agent is a calcium chloride solution, wherein the mass ratio of calcium chloride to sulfate in the wastewater is 1000:(192-375).

[0014] Preferably, the mass ratio of the granular aluminum chloride hydrogel adsorbent to sulfate ions in the wastewater is 1000:(1.6-2.0).

[0015] Preferably, the reagent used to adjust the pH of the wastewater to 7.8-9.2 is one or more of concentrated hydrochloric acid, sodium hydroxide, and magnesium hydroxide.

[0016] Preferably, the temperature of the reaction system in all steps is between 20 and 25°C.

[0017] This invention introduces calcium ions and granular aluminum chloride hydrogel adsorbent into water, causing the sulfate ions to be removed from the water to combine with the introduced calcium ions to form a solid with low solubility, facilitating separation from the water. The use of granular aluminum chloride hydrogel adsorbent accelerates the deposition rate of insoluble solids, causing small precipitates to aggregate into larger, more stable precipitates, thus reducing the difficulty of solid-liquid separation.

[0018] This invention, based on the traditional chemical precipitation method, adds calcium ion reagents, which react well with sulfate ions in water to form insoluble solids, effectively removing sulfate ions from the water.

[0019] This invention utilizes granular hydrogel loaded with small-particle aluminum chloride. Due to its large specific surface area, good adsorption capacity, and strong stability, it acts as an adsorbent to adsorb the insoluble solids formed by calcium ions and sulfate ions, further improving the removal efficiency of sulfate ions. Simultaneously, some sulfate ions form complexes such as Al2Ca3(SO4)6 with calcium and aluminum ions, firmly fixed on the surface and interior of the hydrogel, greatly enhancing the removal rate.

[0020] This invention utilizes a polymeric material (i.e., hydrogel) loaded with a polymerizing agent (i.e., aluminum chloride) to overcome the shortcomings of traditional chemical precipitation methods, which result in poor aggregation and sedimentation after the formation of insoluble substances. This allows the generated calcium sulfate solid to rapidly aggregate and settle, facilitating subsequent solid-liquid separation. Simultaneously, it can also partially react to remove small amounts of residual sulfate ions in the water.

[0021] This invention improves upon the commonly used chemical precipitation method by optimizing the reagent addition method and increasing the removal rate of sulfate ions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the granular aluminum chloride hydrogel adsorbent described in this invention;

[0023] Figure 2 This is a partial schematic diagram of the granular aluminum chloride hydrogel adsorbent described in this invention. Detailed Implementation

[0024] like Figure 1 As shown, the present invention provides a granular aluminum chloride hydrogel adsorbent, comprising hydrogel particles and aluminum chloride particles loaded on the hydrogel particles; the hydrogel comprises gelatin and agar.

[0025] In this invention, the particle size of the hydrogel particles is preferably 1.8 to 2.6 cm, more preferably 2.0 to 2.4 cm; the particle size of the aluminum chloride particles is preferably ≤1.3 mm, more preferably 1.1 to 1.3 mm.

[0026] In this invention, the mass ratio of the hydrogel particles to the aluminum chloride particles is preferably (47.2-48.4):1, more preferably (47.5-48.0):1.

[0027] In this invention, the preferred mass ratio of gelatin to agar is (5.7-5.8):1.

[0028] This invention utilizes granular hydrogel to support small-particle aluminum chloride, which has the advantages of large specific surface area, good adsorption and strong stability.

[0029] Figure 2 This is a partial schematic diagram of the granular aluminum chloride hydrogel adsorbent described in this invention. Figure 2 As shown, when unfolded in a flat shape, aluminum chloride particles can be clearly seen bonded to the hydrogel particles.

[0030] This invention utilizes a polymeric material (i.e., hydrogel) loaded with a polymerizing agent (i.e., aluminum chloride) to overcome the shortcomings of traditional chemical precipitation methods, which result in poor aggregation and sedimentation after the formation of insoluble substances. This allows the generated calcium sulfate solid to rapidly aggregate and settle, facilitating subsequent solid-liquid separation. Simultaneously, it can also partially react to remove small amounts of residual sulfate ions in the water.

[0031] This invention provides a method for preparing the granular aluminum chloride hydrogel adsorbent described above, comprising the following steps: dissolving gelatin and agar in water to obtain a mixture;

[0032] Aluminum chloride particles are dispersed into the mixture, and the resulting dispersion is poured into a mold to form a gel. After drying, the granular aluminum chloride hydrogel adsorbent is obtained.

[0033] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0034] This invention dissolves gelatin and agar in water to obtain a mixture.

[0035] In this invention, the preferred mass ratio of gelatin to agar is (5.7-5.8):1; the preferred mass ratio of gelatin to water is 1:(9.0-9.3), more preferably 1:(9.1-9.2). In this invention, the water is preferably deionized water, and the agar serves as a curing agent.

[0036] In this invention, gelatin and agar are preferably dissolved in water at 46–56°C, ultrasonically dispersed for 15 minutes, and stirred until homogeneous to obtain a mixture.

[0037] After obtaining the mixture, the present invention disperses aluminum chloride particles into the mixture, pours the resulting dispersion into a mold to form a gel, and dries it to obtain the granular aluminum chloride hydrogel adsorbent.

[0038] The present invention does not have special requirements for the dispersion method, as long as the aluminum chloride particles are evenly dispersed. In an embodiment of the present invention, aluminum chloride particles are added to the mixed solution, mixed evenly, and then sonicated for 1 hour.

[0039] In this invention, the mold preferably contains multiple spherical structures, the size of which corresponds to the size of the hydrogel particles.

[0040] Prior to drying, the present invention preferably further includes washing the gel with water. The washing process is not particularly demanding and can be any process well-known in the art.

[0041] In this invention, the drying temperature is preferably below 30°C, and there are no special requirements for the drying time, as long as the surface of the granular aluminum chloride hydrogel adsorbent is dried.

[0042] This invention provides a method for removing sulfate ions from water, comprising the following steps: adding a calcium ion reagent to wastewater containing sulfate ions, then adjusting the pH of the wastewater to 7.8-9.2, and finally adding granular aluminum chloride hydrogel adsorbent, mixing and adsorbing under stirring conditions, allowing to stand, and separating the solid and liquid.

[0043] This invention involves adding calcium ion reagents to wastewater containing sulfate ions.

[0044] This invention does not have specific requirements regarding the source of the wastewater; any wastewater containing sulfate ions well-known in the art is acceptable. This invention also does not have specific requirements regarding the pH value of the wastewater; any pH value is acceptable and can be adjusted subsequently using acid-base reagents. In this invention, the concentration of sulfate ions in the wastewater is preferably 200–500 mg / L, more preferably 250–450 mg / L.

[0045] In this invention, the calcium ion reagent is preferably a calcium chloride solution, and the mass ratio of calcium chloride to sulfate in the wastewater is preferably 1000:(192-375), more preferably 1000:(200-350), and even more preferably 1000:(250-300). This invention does not have special requirements on the concentration of the calcium chloride solution; any concentration is acceptable. The use of calcium chloride as the calcium ion reagent in this invention offers good economic advantages.

[0046] After the addition of calcium ion reagent, the calcium ions can react well with sulfate ions in the water to form an insoluble solid (calcium sulfate), effectively removing sulfate ions from the water.

[0047] After adding calcium ion reagent, the pH value of the wastewater is adjusted to 7.8-9.2 according to the present invention.

[0048] In this invention, the reagent used to adjust the pH of the wastewater to 7.8–9.2 is preferably one or more of concentrated hydrochloric acid, sodium hydroxide, and magnesium hydroxide. This invention adds calcium ion reagent first, then adjusts the pH, which is beneficial for improving precipitation efficiency. The solubility of precipitates and sparingly soluble substances varies at different pH values; this invention achieves the best precipitation efficiency by adjusting the wastewater pH to 7.8–9.2.

[0049] In this invention, after adjusting the pH value of the wastewater to the target value, the preferred method is to mix and react for 25-30 minutes, then add granular aluminum chloride hydrogel adsorbent, mix and adsorb under stirring conditions, let stand, and then separate the solid and liquid.

[0050] In this invention, the mass ratio of the granular aluminum chloride hydrogel adsorbent to sulfate ions in the wastewater is preferably 1000:(1.6-2.0), more preferably 1000:(1.7-1.8).

[0051] In this invention, the preferred mixing and adsorption time is 50–60 min; the preferred settling time is 55–60 min. During the mixing and adsorption process, the adsorbent and the sparingly soluble solid are in full contact, and during the settling process, the sparingly soluble solid rapidly aggregates and settles.

[0052] This invention utilizes granular aluminum chloride hydrogel adsorbents to overcome the shortcomings of traditional chemical precipitation methods, which result in poor aggregation and sedimentation of sparingly soluble substances. This allows the generated calcium sulfate solid to rapidly aggregate and settle, facilitating subsequent solid-liquid separation. Simultaneously, it can also partially remove trace amounts of residual sulfate ions from the water.

[0053] In this invention, the temperature of the reaction system in all the above steps is preferably maintained at 20–25°C. By controlling the temperature of the reaction system within this range, this invention can ensure a high precipitation rate while avoiding increased solubility of insoluble solids under low or high temperature conditions, thus achieving a better removal effect.

[0054] The present invention does not have any special requirements for the solid-liquid separation method; any solid-liquid separation method well known in the art can be used, such as filtration.

[0055] The method provided by this invention can be used to treat wastewater containing sulfate ions, and the sulfate ion removal rate can reach more than 86.7%.

[0056] The following detailed description, in conjunction with embodiments, of the granular aluminum chloride hydrogel adsorbent and its preparation method, as well as the method for removing sulfate ions from water provided by the present invention, should not be construed as limiting the scope of protection of the present invention.

[0057] The following examples illustrate the preparation of granular aluminum chloride hydrogel adsorbents:

[0058] Step 1: Dissolve 6.23g of gelatin and 1.08g of agar in 57mL of deionized water at 47℃, sonicate for 15min, and stir until homogeneous to form a uniform solution.

[0059] Step 2: Add 1.34g of fine aluminum chloride particles (1.2mm in diameter) to the solution, mix thoroughly, and sonicate for 1 hour. Then pour it into a mold and wait for the gelatin and aluminum chloride particles to completely form a gel.

[0060] Step 3: Rinse the obtained hydrogel with deionized water, and then dry it at a temperature below 30°C to obtain granular aluminum chloride hydrogel adsorbent with a diameter of 2.3 cm.

[0061] Example 1

[0062] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 294 mg / L and a pH of 5.3.

[0063] Add 25 mL of calcium ion reagent (22.2 g / L calcium chloride solution) to the sulfate-containing wastewater. Then add sodium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 7.8. Maintain the temperature at 22°C, mix uniformly, and react for 25 minutes.

[0064] 84.0 g of granular aluminum chloride hydrogel adsorbent was added to the wastewater, mixed uniformly, reacted for 45 min, then allowed to stand for 1 h, and filtered. The sulfate ion concentration in the solution was measured to be 39.1 mg / L, with a removal rate of 86.7%.

[0065] Example 2

[0066] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 345 mg / L and a pH of 4.7.

[0067] Add 22 mL of calcium ion reagent (29.6 g / L calcium chloride solution) to the sulfate-containing wastewater. Then add sodium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 8.3. Maintain the temperature at 22℃, mix uniformly, and react for 25 minutes.

[0068] 106.2 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 44.5 mg / L, with a removal rate of 87.1%.

[0069] Example 3

[0070] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 267 mg / L and a pH of 5.0.

[0071] Add 24 mL of calcium ion reagent (28.1 g / L calcium chloride solution) to the sulfate-containing wastewater. Then add sodium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 8.0. Maintain the temperature at 23°C, mix uniformly, and react for 25 minutes.

[0072] 76.6 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 35.2 mg / L, with a removal rate of 86.8%.

[0073] Example 4

[0074] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 392 mg / L and a pH of 6.7.

[0075] Add 24 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 30.9 g / L calcium chloride solution at a mass ratio of 1.2:1. Then, add magnesium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 8.5. Maintain the temperature at 23℃, mix at a uniform rate, and react for 25 minutes.

[0076] 110.2 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed at a uniform rate, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 50.2 mg / L, with a removal rate of 87.2%.

[0077] Example 5

[0078] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 284 mg / L and a pH of 7.1.

[0079] Add 20 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 26.7 g / L calcium chloride solution at a mass ratio of 1.14:1. Then, add magnesium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 8.4. Maintain the temperature at 23℃, mix at a uniform rate, and react for 25 minutes.

[0080] 80.9 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 36.9 mg / L, with a removal rate of 87.0%.

[0081] Example 6

[0082] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 284 mg / L and a pH of 7.8.

[0083] Add 25 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 18.9 g / L calcium chloride solution at a mass ratio of 1.06:1. Then, add magnesium hydroxide, an alkalinity adjuster, to the wastewater to adjust the pH to 8.6. Maintain the temperature at 24℃, mix at a uniform rate, and react for 25 minutes.

[0084] 72.0 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 37.2 mg / L, with a removal rate of 86.9%.

[0085] Example 7

[0086] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 431 mg / L and a pH of 8.3.

[0087] Add 25 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a 1:1 mass mixture of 32.6 g / L calcium chloride solution. Maintain the pH of the wastewater at 8.3, control the temperature at 23℃, mix at a uniform rate, and react for 25 min.

[0088] 122.4 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 55.6 mg / L, with a removal rate of 87.1%.

[0089] Example 8

[0090] The 500 mL wastewater used in the performance test contained a sulfate ion concentration of 363 mg / L and a pH of 9.8.

[0091] Add 24 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 28.5 g / L calcium chloride solution at a mass ratio of 1.2:1. Then, add concentrated hydrochloric acid, an acidity adjuster, to the wastewater to adjust the pH to 8.3. Maintain the temperature at 22℃, mix at a uniform rate, and react for 25 minutes.

[0092] 103.6 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed at a uniform rate, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 47.2 mg / L, with a removal rate of 87.0%.

[0093] Example 9

[0094] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 376 mg / L and a pH of 11.3.

[0095] Add 20 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 35.5 g / L calcium chloride solution at a mass ratio of 1.34:1. Then, add concentrated hydrochloric acid, an acidity adjuster, to the wastewater to adjust the pH to 8.7. Maintain the temperature at 23℃, mix at a uniform rate, and react for 25 minutes.

[0096] 107.5 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed at a uniform rate, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 49.3 mg / L, with a removal rate of 86.9%.

[0097] Example 10

[0098] The 500 mL wastewater used for performance testing contained a sulfate ion concentration of 282 mg / L and a pH of 12.1.

[0099] Add 25 mL of calcium ion reagent to the sulfate-containing wastewater. The reagent is a mixture of 21.3 g / L calcium chloride solution at a mass ratio of 1.4:1. Then, add concentrated hydrochloric acid, an acidity adjuster, to the wastewater to adjust the pH to 9.2. Maintain the temperature at 24℃, mix at a uniform rate, and react for 25 minutes.

[0100] 80.8 g of granular aluminum chloride hydrogel adsorbent prepared according to Example 1 was added to the wastewater, mixed uniformly, and reacted for 45 min. The mixture was then allowed to stand for 1 h and filtered. The sulfate ion concentration in the solution was measured to be 36.7 mg / L, with a removal rate of 87.0%.

[0101] Comparative Example 1

[0102] Same as Example 1, except that instead of adding granular aluminum chloride hydrogel adsorbent to the wastewater, 13.01 g of aluminum chloride granules were added. The removal rate of sulfate ions in the treated solution was 32.8%.

[0103] Comparative Example 2

[0104] Similar to Example 1, the only difference is that instead of adding granular aluminum chloride hydrogel adsorbent to the wastewater, 84g of granular hydrogel was added, and the removal rate of sulfate ions in the treated solution was 24.4%.

[0105] Comparative Example 3

[0106] Same as Example 1, except that no alkalinity adjuster was added to the wastewater. The removal rate of sulfate ions in the treated solution was 35.4%.

[0107] Comparative Example 4

[0108] Same as Example 9, except that the acidity adjuster was no longer added to the wastewater. The removal rate of sulfate ions in the treated solution was 46.9%.

[0109] Comparative Example 5

[0110] Same as Example 1, except that calcium ion reagent was no longer added to the wastewater. The removal rate of sulfate ions in the treated solution was 21.4%.

[0111] As can be seen from the above embodiments and comparative examples, the present invention provides a method for removing sulfate ions from water. This invention introduces calcium ions and granular aluminum chloride hydrogel adsorbent into the water, causing the sulfate ions to be removed to combine with the introduced calcium ions to form a solid with low solubility, facilitating separation from the water. The use of granular aluminum chloride hydrogel adsorbent accelerates the deposition rate of the insoluble solids, causing the small precipitates to aggregate into larger and more stable precipitates, further improving the sulfate ion removal efficiency.

[0112] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for removing sulfate ions from water, characterized in that, The process includes the following steps: adding calcium ion reagent to wastewater containing sulfate ions, then adjusting the pH of the wastewater to 7.8~9.2, and finally adding granular aluminum chloride hydrogel adsorbent, mixing and adsorbing under stirring conditions, allowing it to stand, and then separating the solid and liquid components. The granular aluminum chloride hydrogel adsorbent comprises hydrogel particles and aluminum chloride particles loaded on the hydrogel particles; the hydrogel comprises gelatin and agar. The mass ratio of the hydrogel particles to the aluminum chloride particles is (47.2~48.4):1; The preparation method of the granular aluminum chloride hydrogel adsorbent includes the following steps: dissolving gelatin and agar in water to obtain a mixture; Aluminum chloride particles are dispersed into the mixture, and the resulting dispersion is poured into a mold to form a gel. After drying, the granular aluminum chloride hydrogel adsorbent is obtained.

2. The method according to claim 1, characterized in that, The hydrogel particles have a particle size of 1.8~2.6cm; the aluminum chloride particles have a particle size ≤1.3mm.

3. The method according to claim 1, characterized in that, The mass ratio of gelatin to agar is (5.7~5.8):

1.

4. The method according to claim 1, characterized in that, The calcium ion reagent is a calcium chloride solution, and the mass ratio of calcium chloride to sulfate in the wastewater is 1000:(192~375).

5. The method according to claim 1, characterized in that, The mass ratio of the granular aluminum chloride hydrogel adsorbent to sulfate ions in the wastewater is 1000:(1.6~2.0).

6. The method according to claim 1, characterized in that, The reagents used to adjust the pH of the wastewater to 7.8-9.2 are one or more of concentrated hydrochloric acid, sodium hydroxide, and magnesium hydroxide.

Images