Magnesium-doped calcium carbonate adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a magnesium-doped calcium carbonate adsorbent and a preparation method and application thereof, the chemical formula of magnesium-doped calcium carbonate is as shown in the following formula (1): MgxCa1-x (CO3), x represents the molar ratio of magnesium to calcium, 0 lt; xlt; and 0.200%. Compared with pure calcium carbonate, the adsorption rate of the adsorbent based on the magnesium-doped calcium carbonate material provided by the invention is greatly improved, so that passivation of the pure calcium carbonate in the early stage of adsorption is relieved. Under the condition of the same phosphorus adsorption amount, the adsorption rate of the adsorbent is obviously improved. Alternatively, under the same adsorption time, the phosphorus adsorption amount of the adsorbent provided by the invention is obviously improved. The adsorbent provided by the invention has good adsorption selectivity (competitive ion interference resistance), so that the adsorbent has high practical application value. In addition, as the preparation is simple and convenient and the cost is low, the compound can be used as an agricultural fertilizer slow-release agent, can maintain the phosphorus content in farmland for a long time, and is more beneficial to the growth of crops.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and their preparation technology, and relates to a magnesium-doped calcium carbonate adsorbent, its preparation method and application. Background Technology

[0002] Excessive phosphorus levels in water are one of the key factors causing eutrophication. The eutrophication level of natural water bodies can be divided into three levels based on the total phosphorus content: TP > 20 mg / m³. 3 Eutrophication; TP = 10–20 mg / m³ 3 It is mesotrophic; TP < 10 mg / m³ 3 Eutrophication is a form of water degradation. While eutrophication can occur naturally, human activities (generally categorized as point sources (e.g., untreated sewage, other urban and industrial wastewater) and diffusion sources (e.g., agricultural fertilizer runoff, atmospheric deposition)) can significantly accelerate nutrient input, thus speeding up eutrophication. One major source of excessive phosphorus levels in eutrophic waters is agricultural fertilizer discharge. When phosphate fertilizer is applied to farmland, subsequent irrigation and rainwater runoff lead to its loss, reducing fertilizer utilization and increasing phosphorus concentration in surface water, thus causing eutrophication. Surveys have shown that the phosphorus content in water flowing near farmland is more than five times that of forest watersheds.

[0003] Currently, methods for treating phosphorus-containing wastewater can be categorized into precipitation, electrochemical, membrane separation, adsorption, and biological methods. Adsorption, in particular, has attracted significant research attention due to its ability to accumulate high levels of phosphorus, reduce sludge management, and ensure high compatibility with existing processes.

[0004] According to relevant literature, calcite is chemically stable, widely found in nature, and possesses efficient phosphate removal capabilities, making it a research hotspot. However, its effectiveness in removing phosphate and some heavy metals from wastewater still has limitations. Calcium carbonate (including calcite, aragonite, and granite) can remove phosphate ions and some heavy metal ions through physical adsorption, chemical co-precipitation, and crystallization. The principle of phosphate removal by calcium carbonate is based on the combination of dissolved calcium ions and phosphate ions to form a more stable calcium-phosphate phase apatite precipitate, thus achieving phosphate removal. However, under different pH conditions, phosphate exhibits different ionic forms, resulting in different phosphate removal mechanisms. Munir et al. prepared Mg-modified calcite, whose maximum phosphate adsorption capacity was only 43.33 mg P / g, far lower than the theoretical adsorption capacity of calcium carbonate (186 mg P / g, based on hydroxyapatite as the adsorption product). Existing literature, Synthesis and application of magnesium amorphous calcium carbonate for removal of high concentration of phosphate, Chemical Engineering Journal, 2014, reports a method for preparing magnesium calcium carbonate aragonite phase in ethylene glycol solvent. This method requires the use of ethylene glycol organic solvent, thus increasing production costs. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a magnesium-doped calcium carbonate material, its preparation method, and an adsorbent based on this material, which contains small or trace amounts of magnesium. The adsorbent of this invention, when used for phosphorus removal, has advantages such as high adsorption capacity and accelerated adsorption rate. Furthermore, the magnesium-doped calcium carbonate material of this invention can serve as a slow-release adsorbent for phosphate fertilizers. When the phosphorus concentration in the soil solution is too high, it can bind with phosphates; while when the phosphorus concentration is low, it releases phosphates, thus maintaining the phosphate fertilizer content in farmland soil for a long time, which is beneficial to crop growth.

[0006] Specifically, the present invention achieves the stated objective through the following technical solutions:

[0007] A magnesium-doped calcium carbonate material has the following chemical formula (1):

[0008] Mg x Ca(CO3) (x+1) Equation (1)

[0009] In equation (1), x represents the molar ratio of magnesium to calcium, and 0 <x<0.200。

[0010] According to an embodiment of the present invention, the value range of x is 0 < x < 0.177; preferably 0.007 ≤ x ≤ 0.089. Exemplarily, x = 0.007, 0.008, 0.009, 0.010, 0.020, 0.025, 0.027, 0.030, 0.035, 0.040, 0.045, 0.050, 0.055, 0.060, 0.065, 0.070, 0.075, 0.080, 0.085, 0.089, 0.090, 0.095, 0.099, 0.100, 0.110, 0.120, 0.130, 0.140, 0.150, 0.160, or 0.170.

[0011] According to an embodiment of the present invention, the magnesium-doped calcium carbonate material has a crystalline form. Specifically, it is mainly calcite-type crystal, with some vaterite crystal. Further specifically, it has Figure 1 the X-ray diffraction pattern shown.

[0012] The present invention also provides a method for preparing the above magnesium-doped calcium carbonate material, which includes mixing a magnesium salt, a calcium salt with a water-soluble carbonate and / or a water-soluble bicarbonate, and preparing the magnesium-doped calcium carbonate material through a coprecipitation reaction.

[0013] According to an embodiment of the present invention, the preparation method further includes allowing the reaction solution after the coprecipitation reaction to stand. For example, the standing time can be 1 - 4 h, and exemplarily it is 1 h, 2 h, 3 h, 4 h.

[0014] According to an embodiment of the present invention, the preparation method further includes performing solid-liquid separation on the standing reaction solution to obtain the magnesium-doped calcium carbonate material. For example, the solid-liquid separation can adopt means known in the art, such as suction filtration.

[0015] According to an embodiment of the present invention, in the preparation method, after solid-liquid separation, the magnesium-doped calcium carbonate material is obtained through washing. For example, the solvent used for washing can be water. Also, for example, the number of washing times is not particularly limited, and it is only necessary to control the pH of the filtrate after washing to be 6 - 8, such as pH = 7. <​​​According to an embodiment of the present invention, the calcium salt, magnesium salt, and the water-soluble carbonate and / or water-soluble bicarbonate are all added to the reaction system in solution form. For example, aqueous solutions of the calcium salt, magnesium salt, and water-soluble carbonate and / or water-soluble bicarbonate are prepared separately, and then the solutions are mixed and subjected to a co-precipitation reaction to obtain the magnesium-doped calcium carbonate material.

[0018] According to an embodiment of the present invention, the calcium salt may be a soluble divalent calcium salt, such as at least one selected from calcium chloride, calcium nitrate or their hydrates, preferably anhydrous calcium chloride.

[0019] According to an embodiment of the present invention, the magnesium salt may be a soluble divalent magnesium salt, such as at least one selected from magnesium chloride, magnesium nitrate or their hydrates, preferably anhydrous magnesium chloride.

[0020] According to an embodiment of the present invention, the carbonate / bicarbonate solution may include a carbonate solution (CO3). 2- ), bicarbonate solution (HCO3) - (or a mixed salt solution of both)

[0021] According to an embodiment of the present invention, the carbonate / bicarbonate may be selected from at least one of the following substances: sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, and ammonium bicarbonate.

[0022] According to an embodiment of the present invention, the preparation method further includes stirring the above-mentioned mixed liquid. For example, the mixing can be carried out by stirring at room temperature; or the stirring time is 1 to 72 hours, for example 12 to 24 hours; exemplary examples are 3 hours, 6 hours, 12 hours, 24 hours, and 36 hours.

[0023] According to an embodiment of the present invention, the molar ratio of calcium ions to magnesium ions in the reaction system is (1-100):1; preferably (9-90):1, with exemplary ratios of 4.5:1, 9:1, 18:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, and 90:1.

[0024] According to an embodiment of the present invention, the concentration of magnesium ions in the aqueous solution of the calcium and magnesium salts is 0.01 to 1 mol / L, preferably 0.2 to 0.8 mol / L; exemplary concentrations are 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.75 mol / L, 0.8 mol / L, 0.9 mol / L, and 1 mol / L.

[0025] According to an embodiment of the present invention, the calcium ion concentration in the aqueous solution of the calcium salt and magnesium salt is 0.1-5 mol / L, preferably 0.3-3 mol / L; exemplary concentrations are 0.1 mol / L, 0.2 mol / L, 0.5 mol / L, 0.75 mol / L, 0.8 mol / L, 0.9 mol / L, and 1 mol / L.

[0026] According to an embodiment of the present invention, the concentration of the carbonate / bicarbonate solution is 0.1 to 2 mol / L, for example 0.2 to 1 mol / L, and exemplary concentrations are 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.2 mol / L, 2 mol / L, and 3 mol / L.

[0027] The present invention also provides magnesium-doped calcium carbonate materials prepared by the above preparation method.

[0028] The present invention also provides an adsorbent, specifically an adsorbent for phosphorus adsorption in water, wherein the adsorbent comprises the above-mentioned magnesium-doped calcium carbonate material.

[0029] According to an embodiment of the present invention, the adsorbent can be used as an adsorbent and slow-release agent for phosphate fertilizer. Specifically, when the phosphorus concentration in the water is too high, it can bind with phosphate; while when the phosphorus concentration is low, it will release phosphate, thus maintaining the phosphate fertilizer content in farmland soil for a long time, which is beneficial to crop growth.

[0030] The present invention also provides the application of the above-mentioned magnesium-doped calcium carbonate material as an adsorbent, preferably in its application as an adsorbent and corrosion inhibitor for water dephosphorization or phosphate fertilizer. For example, its application in the adsorption and removal of phosphates in water.

[0031] The present invention also provides a method for removing phosphate by adsorption of the above-mentioned adsorbent, comprising contacting the above-mentioned adsorbent with a phosphate solution.

[0032] Preferably, the method for removing phosphate by adsorption of the above adsorbent includes adding the above adsorbent to a phosphate solution and shaking to adsorb for 1 to 120 hours.

[0033] According to an embodiment of the present invention, the phosphate solution is a neutral solution at room temperature, for example, with a pH of 6.5-7.5, preferably 7.

[0034] According to an embodiment of the present invention, the mass-to-volume ratio of the adsorbent to the phosphate solution is 1 mg:(1-10) mL, preferably 1 mg:6.25 mL.

[0035] According to an embodiment of the present invention, the phosphate content in the phosphate solution is 15-60 mg P / g.

[0036] According to an embodiment of the present invention, in the adsorption system, the pH of the phosphate solution is 2 to 11, preferably 5 to 8, and exemplarily 7.

[0037] For example, 16 mg of the above adsorbent was added to 100 mL of phosphate solution with pH = 7.0; it was then placed in a shaker at 180 r / min and 25 °C for 6–120 h; finally, the remaining phosphate content was determined by the molybdenum blue method to determine the adsorption performance of the adsorbent.

[0038] The beneficial effects of this invention are:

[0039] The adsorbent based on magnesium-doped calcium carbonate provided by this invention has the advantage of high adsorption capacity when used for phosphorus removal.

[0040] Furthermore, compared to pure calcium carbonate, the adsorbent based on magnesium-doped calcium carbonate provided by this invention exhibits a significantly improved adsorption rate, thus alleviating the passivation that occurs during the early adsorption phase of pure calcium carbonate. Under the same phosphorus adsorption capacity, the adsorption rate of the adsorbent of this invention is significantly increased. Alternatively, under the same adsorption time, the phosphorus adsorption capacity of the adsorbent of this invention is significantly increased. Moreover, the adsorbent of this invention possesses good adsorption selectivity (resistance to competing ion interference), thus demonstrating high practical application value.

[0041] In addition, due to its simple production and low cost, it can be used as a slow-release fertilizer in agriculture, which can maintain the phosphorus content in farmland for a long time and further promote crop growth. Attached Figure Description

[0042] Figure 1 The X-ray diffraction patterns are for samples from Comparative Examples 1-2 and Examples 1-4.

[0043] Figure 2 This is a line graph showing the adsorption kinetics of the sample in Example 3.

[0044] Figure 3 The bar chart shows the phosphorus adsorption test results of the samples of Example 3 and Comparative Example 2 in the presence of competing ions at different concentrations.

[0045] Figure 4 (a) and (b) are scanning electron microscope images of the samples from Comparative Example 2 and Example 3, respectively.

[0046] Figure 5 The Fourier transform infrared spectra of the samples from Example 3 and Comparative Example 2 are shown.

[0047] Figure 6 The graph shows the relationship between adsorption amount and time for samples from Comparative Examples 1-2 and Examples 1-4.

[0048] Figure 7The bar chart shows the adsorption amount versus time for samples from Comparative Example 2 and Example 3 over 24 hours.

[0049] Figure 8 The image shows the phosphate concentration in the leachate of samples from Comparative Examples 1-2 and Example 3. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Comparative Example 1

[0053] Untreated AR-grade commercial calcium carbonate purchased from Shanghai Titan Company, Adamas Group.

[0054] Comparative Example 2

[0055] Add 10g of CaCl2 to 100mL of water and stir at room temperature for 3 hours to obtain a calcium ion solution. Prepare 100mL of 1.2mol / L Na2CO3 solution and add 100mL of Na2CO3 solution dropwise to the calcium ion solution. Continue stirring at room temperature for 12 hours, then let stand for 3 hours. Filter the resulting solution and wash repeatedly with deionized water until the filtrate is neutral. Dry the filter cake in a 100℃ drying oven for 24 hours to obtain calcium carbonate material, which is Comparative Example 2.

[0056] Example 1

[0057] The preparation of an adsorbent based on magnesium-doped calcium carbonate material is as follows: 0.1 g MgCl2 and 10 g CaCl2 are added to 100 mL of water and stirred at room temperature for 3 hours to obtain a calcium-magnesium mixed solution; 100 mL of 1.2 mol / L Na2CO3 solution is prepared and added dropwise to the calcium-magnesium mixed solution, and stirring is continued at room temperature for 12 hours, followed by standing for 3 hours. The resulting solution is filtered and repeatedly washed with deionized water until the filtrate is neutral. The filter cake is dried in a 100℃ drying oven for 24 hours to obtain magnesium-doped calcium carbonate material with the structural formula shown in formula (1), where x = 0.007.

[0058] Example 2

[0059] The preparation of an adsorbent based on magnesium-doped calcium carbonate material is as follows: 0.5 g MgCl2 and 10 g CaCl2 are added to 100 mL of water and stirred at room temperature for 3 hours to obtain a calcium-magnesium mixed solution; 100 mL of 1.2 mol / L Na2CO3 solution is prepared and added dropwise to the calcium-magnesium mixed solution, and stirring is continued at room temperature for 12 hours, followed by standing for 3 hours. The resulting solution is filtered and repeatedly washed with deionized water until the filtrate is neutral. The filter cake is dried in a 100℃ drying oven for 24 hours to obtain magnesium-doped calcium carbonate material with the structural formula shown in formula (1), where x = 0.027.

[0060] Example 3

[0061] The preparation of an adsorbent based on magnesium-doped calcium carbonate material is as follows: 1.0 g MgCl2 and 10 g CaCl2 are added to 100 mL of water and stirred at room temperature for 3 hours to obtain a calcium-magnesium mixed solution; 100 mL of 1.2 mol / L Na2CO3 solution is prepared and added dropwise to the calcium-magnesium mixed solution, and stirring is continued at room temperature for 12 hours, followed by standing for 3 hours. The resulting solution is filtered and repeatedly washed with deionized water until the filtrate is neutral. The filter cake is dried in a 100℃ drying oven for 24 hours to obtain magnesium-doped calcium carbonate material with the structural formula shown in formula (1), where x = 0.089.

[0062] Example 4

[0063] The preparation of an adsorbent based on magnesium-doped calcium carbonate material is as follows: 2.0 g MgCl2 and 10 g CaCl2 are added to 100 mL of water and stirred at room temperature for 3 hours to obtain a calcium-magnesium mixed solution; 100 mL of 1.2 mol / L Na2CO3 solution is prepared and added dropwise to the calcium-magnesium mixed solution, and stirring is continued at room temperature for 12 hours, followed by standing for 3 hours. The resulting solution is filtered and repeatedly washed with deionized water until the filtrate is neutral. The filter cake is dried in a 100℃ drying oven for 24 hours to obtain magnesium-doped calcium carbonate material with the structural formula shown in formula (1), where x = 0.177.

[0064] like Figure 1 As shown, the magnesium-doped calcium carbonate material prepared by this invention has a crystalline morphology, specifically, mainly calcite-type crystalline morphology, with some spheroidal crystalline morphology.

[0065] Test case

[0066] 1.1 Phosphorus adsorption test results of comparative and example samples

[0067] 100 mL of KH₂PO₄ solution (phosphorus concentration 30 mg P / L) was taken into each Erlenmeyer flask, and the pH of the solution was adjusted to 7. 16 mg of the adsorbent from Comparative Examples 1-2 and Examples 1-4 was added to each flask, and the flasks were placed in a shaker at 180 rpm for adsorption. After 60 h, the solution was filtered through a 0.045 μm filter membrane, and the phosphorus content in the sample was determined according to the molybdenum blue method (GB11893-89), thereby calculating the phosphorus adsorption capacity of the adsorbent. The test results are shown in Table 1 and... Figure 6 As shown.

[0068] Table 1. Phosphorus adsorption test results of adsorbent samples from Comparative Examples 1-2 and Examples 1-4

[0069]

[0070] As can be seen from the data in Table 1, compared with Comparative Examples 1-2, the adsorption capacity of the magnesium-doped calcium carbonate materials prepared in Examples 1-3 of the present invention is significantly improved; while in Example 4, when the magnesium ion doping amount is too high, the adsorption performance of the magnesium-doped calcium carbonate material for phosphate is significantly reduced.

[0071] 1.2 X-ray diffraction patterns of adsorbent samples from Comparative Examples 1-2 and Examples 1-4

[0072] The adsorbent samples from Comparative Examples 1-2 and Examples 1-4 were characterized by X-ray diffraction, and the test results are as follows: Figure 1 As shown, the diffraction peaks of the adsorbent samples in Examples 1-4 are basically the same as the X-ray diffraction peaks of Comparative Example 1, which indicates that the adsorbent samples prepared by the method of the present invention and the sample of Comparative Example 1 are all amorphous calcium carbonate phases.

[0073] 1.3 Adsorption kinetics test of sample in Example 3

[0074] Adsorption kinetics tests were conducted on the adsorbent samples from Examples 1-4 and Comparative Examples 1-2. The test conditions were as follows: 16 mg adsorbent, 100 mL KH₂PO₄ solution (phosphorus concentration 30 mg P / L), pH adjusted to 7, and adsorption was performed on a shaker at 180 rpm. Samples were taken at different times and filtered through a 0.045 μm filter membrane to determine the phosphorus content (molybdenum blue method (GB11893-89)). The adsorption capacity of the adsorbent was calculated. The phosphorus adsorption capacity test results of the magnesium-doped calcium carbonate material prepared in Example 3 are shown below. Figure 2 Table 2; Figure 6 The graph shows the relationship between adsorption amount and time for samples from Comparative Examples 1-2 and Examples 1-4.

[0075] Table 2. Phosphorus adsorption test results of the adsorbent sample in Example 3.

[0076] Time h Phosphorus adsorption capacity (mg P / g) 2 4.6 8 11.4 12 34.3 24 91.4 36 119.6 48 130.3 60 141.2 72 142.4 84 146.0 96 146.2 120 146.5

[0077] From Table 2 and Figure 2 It can be seen that the magnesium-doped calcium carbonate material prepared in Example 3 reaches saturation within 60 hours of adsorption. This indicates that the magnesium-doped calcium carbonate adsorbent of the present invention has a fast adsorption rate.

[0078] 1.4 Competitive Ion Testing of Samples from Example 3

[0079] Competitive ion testing was performed on the samples of Example 3. The testing method is as follows: Using the phosphorus content in the KH₂PO₄ solution (phosphorus concentration 30 mg P / L) as the standard (competitive ion concentration 0), competitive ions (Cl₂) were added at competitive ion concentration: phosphorus concentration (molar amount) ratios of 1:1, 5:1, and 10:1. - SO4 2- NO3 - The test conditions were as follows: 16 mg of adsorbent and 100 mL of phosphorus solution containing competing ions were added to a 100 mL Erlenmeyer flask, which was then placed in a shaker and shaken. Sampling was performed after 60 hours of adsorption. The test results are as follows. Figure 3 As shown, from Figure 3 As can be seen, the magnesium-modified calcium carbonate adsorbent of Example 3 has excellent resistance to competitive ion interference.

[0080] 1.5 Fourier transform infrared spectra of the sample from Example 3

[0081] The Fourier transform infrared spectra of the samples from Example 3 and Comparative Example 2 are shown below. Figure 5 As can be seen from the figure: at 870cm -1 An absorption peak for CaCO3 is shown at 1377 cm⁻¹. -1 CO3 appears 2- The absorption peak indicates that the product is CaCO3.

[0082] 1.6 SEM images of samples from Comparative Example 2 and Example 3

[0083] SEM tests were performed on samples from Comparative Example 2 and Example 3, and the results are as follows: Figure 4 As shown in (a) and (b) in the figure, it can be seen from the figure that compared with the comparative example 2, the sample is in the form of thin sheets and the surface of the adsorbent is rough and porous, which is conducive to the adsorption of phosphate.

[0084] 1.7 Slow-release experiments of phosphate fertilizer in soil columns were conducted on pure soil, comparative examples 1 and 2, and the adsorbent samples of example 3.

[0085] A slow-release phosphate fertilizer column experiment was conducted on pure soil, and the adsorbent samples from Comparative Examples 1, 2, and 3. The test method was as follows: Untreated soil (purchased from Mianyang, Sichuan, natural sandy soil) was slowly added to four phosphate fertilizer columns to a depth of 25 cm. Then, 2 g of pure soil (purchased from Mianyang, Sichuan, natural sandy soil), 2 g of a mixture of magnesium carbonate and calcium carbonate from Comparative Example 1 at a molar ratio of 1:10, 2 g of a mixture of magnesium carbonate and calcium carbonate from Comparative Example 2 at a molar ratio of 1:10, and 2 g of the magnesium-doped calcium carbonate adsorbent material prepared in Example 3 were added to each column to a depth of 5 cm. After backfilling, deionized water was added to the column to saturate the soil moisture content. At the start of the experiment, 5 mL of a 30 mg P / L solution was added to the column on the first day, and 30 mL of deionized water was added from the second day onwards for 6 consecutive days. The leachate was filtered, and the phosphate concentration was measured. The test results are as follows: Figure 8 As shown in the figure, compared to pure soil and the adsorbents in Comparative Examples 1 and 2, which showed high phosphorus release on the first day, the magnesium-doped calcium carbonate material prepared in Example 3 showed relatively low phosphorus release, with phosphorus release starting on the third day. This indicates that the magnesium-doped calcium carbonate material prepared according to this invention has the potential to serve as a phosphate slow-release agent.

[0086] 1.8 The magnesium-doped calcium carbonate materials prepared in Examples 1-4 were subjected to ICP-OES testing, and the results are shown in Table 3.

[0087] Table 3. ICP test results of magnesium-doped calcium carbonate materials in Examples 1-4

[0088] Adsorbent Example 1 Example 2 Example 3 Example 4 Mg content (wt.%) 0.17 0.64 2.03 3.75 Ca content (wt.%) 39.81 39.15 37.23 34.84 Mg:Ca (molar ratio) 0.007 0.027 0.089 0.177

[0089] As shown in Table 3, the magnesium-doped calcium carbonate material prepared in this invention contains a small amount of Mg, and the Mg:Ca molar ratio is 0. <x≤0.177。

[0090] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A magnesium-doped calcium carbonate material, characterized in that, The chemical formula is shown in the following formula (1): Mg x Ca1(CO3) (x+1) Formula (1) In formula (1), x represents the molar ratio of magnesium to calcium, 0 < x < 0.

200.

2. The magnesium-doped calcium carbonate material according to claim 1, characterized in that, The magnesium-doped calcium carbonate material has a crystalline form.

3. Process for the preparation of a magnesium-doped calcium carbonate material according to claim 1 or 2, characterized in that The preparation method comprises mixing a magnesium salt, a calcium salt, a water-soluble carbonate and / or a water-soluble bicarbonate, and preparing the magnesium-doped calcium carbonate material through a co-precipitation reaction.

4. The production method according to claim 3, wherein The calcium salt, the magnesium salt, and the water-soluble carbonate and / or water-soluble bicarbonate are all added to the reaction system in the form of a solution. Preferably, the calcium salt is selected from at least one of calcium chloride, calcium nitrate, or a hydrate thereof. Preferably, the magnesium salt is selected from at least one of magnesium chloride, magnesium nitrate, or a hydrate thereof. Preferably, the carbonate / bicarbonate solution comprises a carbonate solution (CO3 2- ), a bicarbonate solution (HCO3 - ) or a mixed salt solution of both. Preferably, the carbonate / bicarbonate is selected from at least one of sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, rubidium bicarbonate, cesium bicarbonate, ammonium bicarbonate.

5. The production method according to claim 3 or 4, characterized by, In the reaction system, the molar ratio of calcium ions to magnesium ions is (1-100):

1.

6. The production method according to any one of claims 3 to 5, wherein In the water solution of the calcium salt and the magnesium salt, the concentration of magnesium ions is 0.01-1 mol / L. Preferably, in the water solution of the calcium salt and the magnesium salt, the concentration of calcium ions is 0.1-5 mol / L. Preferably, the concentration of the carbonate / bicarbonate solution is 0.1-2 mol / L.

7. The magnesium-doped calcium carbonate material prepared by the preparation method of any one of claims 3-6.

8. An adsorbent, characterized by, The adsorbent comprises the magnesium-doped calcium carbonate material of claim 1 or 7.

9. The magnesium-doped calcium carbonate material of claim 1 or 7 as an adsorbent.

10. A method for removing phosphates, characterized by, The adsorbent comprises the magnesium-doped calcium carbonate material of claim 1 or 7.

9. The magnesium-doped calcium carbonate material of claim 1 or 7 as an adsorbent. The adsorbent comprises the magnesium-doped calcium carbonate material of claim 1 or 7.

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