Quaternary hydrotalcite-like compound, preparation method thereof and application of quaternary hydrotalcite-like compound in heavy metal adsorption

Abstract

The invention relates to the technical field of heavy metal adsorption treatment, in particular to quaternary hydrotalcite, a preparation method thereof and application of the quaternary hydrotalcite in heavy metal adsorption. The preparation method of the quaternary hydrotalcite-like compound comprises the following steps: weighing a magnesium salt, a manganese salt, an iron salt and a zirconium salt to prepare a mixed salt solution; the preparation method comprises the following steps: weighing Na2CO3, and adding water to prepare an alkali solution; dropwise adding the mixed salt solution into the alkali solution, stirring and reacting, aging and filtering the reaction solution, and cleaning and drying a filter cake to obtain the magnesium-iron-manganese-zirconium quaternary hydrotalcite. The magnesium-manganese-iron-zirconium quaternary hydrotalcite prepared by the preparation method is applied to adsorption of heavy metal antimony. In the quaternary hydrotalcite-like compound, iron and manganese have special affinity to antimony, and zirconium can cause hydrotalcite laminate defects, so that active adsorption sites are increased, and the adsorption to antimony is enhanced; the magnesium-iron-manganese-zirconium quaternary hydrotalcite is synthesized in one step, the preparation is simple, the cost is low, the material is applied to treatment of antimony-containing wastewater, the adsorption rate is high, the equilibrium reaching time is short, the applied pH value range is wide, the adsorption capacity is large, and the application prospect is wide.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal adsorption treatment, and particularly relates to a quaternary hydrotalcite, a preparation method thereof, and an application thereof in adsorbing heavy metals. Background Art

[0002] The processes of antimony ore mining, beneficiation, smelting, processing, etc. will cause antimony pollution in the water and soil environment; antimony has no known biological function, and in the "Opinions on Further Strengthening the Prevention and Control of Heavy Metal Pollution" issued in March 2022, antimony was again listed as a key pollutant for prevention and control.

[0003] At present, the methods for removing heavy metals from wastewater include adsorption method, precipitation method, redox method, electrochemistry method, biological method, etc.; the adsorption method has advantages such as convenient design and low cost, and is one of the most promising methods for treating heavy metal-containing wastewater. The design and development of adsorbents are the technical keys to realizing the adsorption method; different from heavy metals such as cadmium, lead, copper, zinc, nickel, mercury, etc., antimony mainly exists in the form of anions in the water environment, while hydrotalcite (LDH) is an anionic layered clay compound composed of positively charged lamellar metal ions and interlayer anions; the electrostatic attraction of the positive charges on its lamellae and the exchangeability of the interlayer anions enable it to be well applied in the treatment of wastewater containing anionic pollutants; however, the traditional binary hydrotalcite has a low heavy metal adsorption capacity. Introducing two or more metal ions to prepare a multi-component hydrotalcite compound and through the synergistic effect can greatly improve its saturated adsorption capacity for anionic pollutants.

[0004] In the existing technical system, for example, the technical solution disclosed in CN109570218A is to physically mix hydrotalcite with zirconium oxychloride, hydrotalcite, calcium oxide, ferrous sulfate, etc. to make an antimony stabilizer and apply it to the remediation of antimony-polluted soil; the technical solution disclosed in CN111100647A is to physically mix nano-zero-valent iron-modified hydrotalcite, calcium-based bentonite, alumina, and magnesia and then add them to the soil, and spray a zirconium salt solution to fix antimony and arsenic in the soil. CN109570218A and CN111100647A are both for the application of natural hydrotalcite.

[0005] The technical solution disclosed in CN110201629A is to prepare a ternary hydrotalcite adsorbent by adding a mixed solution of sodium hydroxide and sodium carbonate to a solution of magnesium nitrate, manganese nitrate or aluminum nitrate, zirconium nitrate. Its chemical formula is Mg6MZr(OH) 16 CO3·4H2O, where M is Mn or Al. This ternary hydrotalcite adsorbent can be used to adsorb phosphate in water, but its adsorption effect on antimony is unknown. Summary of the Invention

[0006] The present invention provides a quaternary hydrotalcite-like compound containing magnesium, iron, manganese, and zirconium, its preparation method, and its application in heavy metal adsorption, solving the technical problem of the relatively low adsorption capacity of hydrotalcite-like compounds for heavy metal antimony.

[0007] The first object of the present invention is to provide a preparation method of a quaternary hydrotalcite-like compound, comprising the following steps:

[0008] 1): Weigh magnesium salt, manganese salt, iron salt, and zirconium salt, and add water to prepare a mixed salt solution with a volume of V1.

[0009] 2): Weigh Na2CO3, and add water to prepare an alkali solution with a volume of V2.

[0010] 3): Drop the mixed salt solution in step 1) into the alkali solution in step 2) and stir for reaction to obtain a reaction solution.

[0011] 4): Age and filter the reaction solution in step 3), wash the filter cake and dry it to obtain the quaternary hydrotalcite-like compound.

[0012] In a specific embodiment of the present invention, in step 1), the molar ratio of magnesium salt to manganese salt is (10 - 16):(4 - 10), and the molar ratio of magnesium salt + manganese salt, iron salt, and zirconium salt is 20:(8 - 10):1.

[0013] In a specific embodiment of the present invention, the magnesium salt is any one or any combination of magnesium chloride, magnesium nitrate, magnesium sulfate, and their hydrates.

[0014] In a specific embodiment of the present invention, the manganese salt is any one or any combination of manganese chloride, manganese nitrate, manganese sulfate, and their hydrates.

[0015] In a specific embodiment of the present invention, the iron salt is any one or any combination of iron chloride, iron nitrate, iron sulfate, and their hydrates.

[0016] In a specific embodiment of the present invention, the zirconium salt is any one or any combination of zirconium nitrate, zirconium sulfate, and their hydrates.

[0017] In a specific embodiment of the present invention, in step 1), the concentration of magnesium in the mixed salt solution is 0.10 - 0.16 mol / L.

[0018] In a specific embodiment of the present invention, in step 2), the volume V2 is equal to the volume V1.

[0019] In a specific embodiment of the present invention, in step 2), the concentration of Na2CO3 in the alkali solution is 0.01 - 0.02 mol / L.

[0020] In a specific embodiment of the present invention, in step 3), the temperature of the stirring reaction is 10 - 40°C, the time is 30 - 60 min; the pH value of the stirring reaction is controlled to be 10 - 12.

[0021] In a specific embodiment of the present invention, the pH value control is to dropwise add a 2 mol / L sodium hydroxide solution during the stirring reaction.

[0022] In a specific embodiment of the present invention, in step 4), the aging treatment is carried out in an oven at 70 - 90°C for 12 - 24 h; the drying temperature is 80 - 105°C.

[0023] In a specific embodiment of the present invention, in step 4), the particle size of the quaternary hydrotalcite is ≤100 mesh.

[0024] The second object of the present invention is to provide the quaternary hydrotalcite prepared by the above preparation method.

[0025] The third object of the present invention is to provide the application of the above quaternary hydrotalcite in adsorbing heavy metals, and the heavy metal is antimony.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The positive charge carried on the surface of the quaternary hydrotalcite of the present invention can adsorb antimonate ions through electrostatic interaction, and the anions such as OH - , CO3 2- between the layers can exchange antimonate ions. More importantly, the special affinity of iron and manganese introduced on the layer board for antimony and the lattice defects of the layer board caused by tetravalent zirconium can be utilized to increase the active adsorption sites and enhance the adsorption effect on antimony;

[0028] 2. The preparation method of the quaternary hydrotalcite of the present invention can prepare the quaternary hydrotalcite containing magnesium, iron, manganese and zirconium by one-step synthesis by controlling the molar ratio of the four metals and the reaction pH value, and the method is simple and the cost is low.

[0029] 3. The quaternary hydrotalcite of the present invention is applied to the treatment of antimony-containing wastewater, with a fast adsorption rate, a short equilibrium time, a wide pH value range for application, and a large adsorption capacity. Brief Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the equipment for preparing the quaternary hydrotalcite in a specific embodiment of the present invention;

[0031] Figure 2 It is the XRD spectrum of the quaternary hydrotalcite in Example 1 of a specific embodiment of the present invention;

[0032] Figure 3 It is the XPS full spectrum of the quaternary hydrotalcite in Example 1 of a specific embodiment of the present invention;

[0033] Figure 4 XRD patterns of the quaternary hydrotalcite-like compounds prepared at different pH values in Example 6 of the specific embodiments of the present invention;

[0034] Figure 5 Curves of antimony adsorption rate (R) and adsorption capacity (Qa) at different solid-liquid ratios of quaternary hydrotalcite-like compounds provided in Example 7 of the specific embodiments of the present invention;

[0035] Figure 6 Curves of antimony adsorption rate (R) and adsorption capacity (Qa) at different initial antimony concentrations provided in Example 7 of the specific embodiments of the present invention;

[0036] Figure 7 Curves of Fe and Mn dissolution amounts and antimony adsorption rate (R) at different solution pH values provided in Example 7 of the specific embodiments of the present invention;

[0037] Figure 8 Curve of antimony adsorption rate at different adsorption times provided in Example 7 of the specific embodiments of the present invention;

[0038] Figure 9 Curves of antimony adsorption rate at different adsorption temperatures and times provided in Example 7 of the specific embodiments of the present invention;

[0039] Figure 10 Curve of antimony adsorption rate under different competitive ions provided in Example 7 of the specific embodiments of the present invention;

[0040] Figure 11 Curve of antimony saturated adsorption capacity (Qe) of MgFeMnZr-LDH material at different Sb concentrations provided in Example 7 of the specific embodiments of the present invention. Specific embodiments

[0041] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention fall within the scope of protection of the present invention.

[0042] A preparation method of a quaternary hydrotalcite-like compound, comprising the following steps:

[0043] 1): Weigh magnesium salt, manganese salt, iron salt and zirconium salt, and add water to prepare a mixed salt solution with a volume of V1;

[0044] 2): Weigh Na2CO3, and add water to prepare an alkali solution with a volume of V2;

[0045] 3): Add the mixed salt solution in step 1) dropwise to the alkali solution in step 2) and stir to react to obtain a reaction solution;

[0046] 4): Age and filter the reaction solution in step 3), wash the filter cake and dry it to obtain a quaternary hydrotalcite-like compound.

[0047] In some examples, in step 1), the molar ratio of the magnesium salt to the manganese salt is (10 - 16):(4 - 10), and the molar ratio of the magnesium salt + manganese salt, iron salt, and zirconium salt is 20:(8 - 10):1.

[0048] In some examples, in step 1), the magnesium salt, manganese salt, iron salt, and zirconium salt can also be weighed and mixed according to the mass ratio of metal elements and dissolved in water to a volume V1, or the magnesium salt, manganese salt, iron salt, and zirconium salt can be weighed separately and dissolved in water respectively, and then the dissolved solutions are combined, and finally water is added to obtain a mixed salt solution with a volume of V1.

[0049] In some examples, the magnesium salt is any one or more of magnesium chloride, magnesium nitrate, magnesium sulfate, and their hydrates.

[0050] In some examples, the manganese salt is any one or more of manganese chloride, manganese nitrate, manganese sulfate, and their hydrates.

[0051] In some examples, the iron salt is any one or more of iron chloride, iron nitrate, iron sulfate, and their hydrates.

[0052] It should be noted that the iron in the iron salt is all trivalent iron.

[0053] In some examples, the zirconium salt is any one or more of zirconium nitrate, zirconium sulfate, and their hydrates.

[0054] In some examples, in step 1), the concentration of magnesium in the mixed salt solution is 0.10 - 0.16 mol / L; the concentrations of manganese, iron, and zirconium in the mixed salt solution are controlled according to the concentration of magnesium and the above molar ratio.

[0055] In some examples, in step 2), the volume V2 is equal to the volume V1.

[0056] In some examples, in step 2), the concentration of Na2CO3 in the alkali solution is 0.01 - 0.02 mol / L.

[0057] In some examples, in step 3), the temperature of the stirring reaction is 10 - 40 °C, and the time is 30 - 60 min; the pH value of the stirring reaction is controlled to be 10 - 12.

[0058] In some examples, the pH value is controlled by dropping 2 mol / L sodium hydroxide solution into the stirring reaction to control the pH value of the stirring reaction at 10 - 12.

[0059] In some examples, in step 4), the aging treatment is carried out in an oven at 70 - 90 °C for 12 - 24 h; the drying temperature is 80 - 105 °C.

[0060] In some examples, in step 4), the particle size of the quaternary hydrotalcite is ≤ 100 mesh; after the drying in step 4) is completed, grinding is carried out and then passing through a 100 - mesh sieve to obtain a quaternary hydrotalcite with a particle size ≤ 100 mesh.

[0061] The quaternary hydrotalcite prepared by the above - mentioned preparation method; this quaternary hydrotalcite contains magnesium, manganese, iron, and zirconium elements; the positive charge carried on the surface of this quaternary hydrotalcite can adsorb antimonate ions through electrostatic interaction, and the anions such as OH - 、CO3 2- etc. can exchange antimonate ions, and more importantly, it can utilize the special affinity of iron and manganese introduced on the layer board for antimony and the lattice defects caused by tetravalent zirconium on the layer board to increase the active adsorption sites for adsorbing antimonate ions.

[0062] The application of the above - mentioned quaternary hydrotalcite in adsorbing heavy metals, where the heavy metal is antimony; the adsorption of heavy metal antimony is completed in wastewater.

[0063] To further prove the role of the quaternary hydrotalcite of the present invention in improving the adsorption of heavy metal antimony, the following examples are provided:

[0064] Example 1

[0065] See the appendix Figure 1 , this example provides a preparation method of a quaternary hydrotalcite, and its preparation includes the following steps:

[0066] Weigh 4.1026 g of Mg(NO3)2·6H2O, 4.0400 g of Fe(NO3)3·9H2O, 0.6761 g of MnSO4·H2O, and 0.4293 g of Zr(NO3)4·5H2O into a beaker, then add 100 mL of distilled water and stir to dissolve; at the same time, weigh 0.1060 g of Na2CO3 into another beaker, add 100 mL of distilled water and stir to dissolve; under magnetic stirring, use a constant - flow pump to drop the metal mixed salt solution drop by drop into the beaker containing the alkali solution, and at the same time, drop 2 mol / L sodium hydroxide solution to control the pH value to remain at 10; after the dropping of the metal mixed salt solution is completed, continue to stir for 1 hour, place it in an 80 °C oven for aging for 24 h, carry out suction filtration, wash the obtained precipitate several times with deionized water, dry it at 80 °C and then grind it and pass through a 100 - mesh sieve to obtain a quaternary hydrotalcite containing magnesium, iron, manganese, and zirconium elements, denoted as MgFeMnZr - LDH.

[0067] Adsorption test: Weigh MgFeMnZr-LDH into a conical flask, then add 50 mL of antimony solution. Adjust the pH value of the solution with 0.1 mol / L NaOH and 0.1 mol / L HCl. Oscillate the solution at a constant temperature for a certain time. Transfer the supernatant and measure the concentration of antimony with a flame atomic absorption spectrometer. After determining that MgFeMnZr-LDH reaches the saturated adsorption capacity, filter the adsorbed saturated solution. Wash the filter residue and dry it to obtain the adsorbed saturated quaternary hydrotalcite-like compound for XPS analysis.

[0068] In the adsorption test, the removal rate (R) and the saturated adsorption capacity (Q e ) are calculated by the following formulas (1) and (2):

[0069] Formula (1):

[0070] Formula (2):

[0071] Wherein, C0 represents the initial mass concentration of heavy metals in the solution, mg / L; C e represents the mass concentration of heavy metals in the solution at equilibrium, mg / L; V represents the volume of the solution, L; m represents the mass of MgFeMnZr-LDH, g.

[0072] The schematic diagram of the equipment for the preparation method of the quaternary hydrotalcite-like compound in this example is as shown in the appendix Figure 1 as follows.

[0073] The X-ray diffraction analysis (XRD) pattern of the quaternary hydrotalcite-like compound in this example is as shown in the appendix Figure 2 as follows.

[0074] The XPS pattern of the Sb-adsorbed saturated quaternary hydrotalcite-like compound in this example is as shown in the appendix Figure 3 as follows.

[0075] See the appendix Figure 2, at diffraction angles 2θ of 10.8°, 22.6°, 33.7° and 60.4°, they respectively correspond to the diffraction crystal planes (003), (006), (009) and (110) of hydrotalcite-like compounds, indicating that the MgFeMnZr-LDH prepared in this example has the characteristic structure of hydrotalcite-like compounds; the characteristic peaks at 2θ = 19.20° and 2θ = 34.00° respectively correspond to the (002) and (311) crystal planes of MnOOH, which is consistent with the standard card PDF#18-0804; a characteristic diffraction peak of Mn(OH)2 appears at 2θ = 59.08°, which is consistent with PDF#18-0787; characteristic diffraction peaks of FeOOH appear at 2θ = 34.00° and 35.16°, and the corresponding crystal planes are (400) and (211) respectively, which is consistent with PDF#34-1266; crystal plane peaks of (003), (208), (217) of Fe(OH)2 and Mg(OH)2 appear at 2θ = 18.51°, 2θ = 59.56° and 2θ = 60.46°, which is consistent with the standard card PDF#15-0125; characteristic peaks of ZrO2 appear at 2θ = 34.21° and 2θ = 60.86°, which is consistent with the standard card PDF#49-1746; the results show that the material is a hydrotalcite-like material with Mg, Fe, Mn, and Zr as the lamellar.

[0076] See the appendix Figure 3 , an Mg1s peak appears at the 1303 eV position for MgFeMnZr-LDH, Mn2p peaks appear at the 642 eV and 653 eV positions respectively, Fe2p peaks appear at the 713 eV and 726 eV positions, and Zr3d peaks appear at the 181 eV and 183 eV positions, which is consistent with the XRD measurement results, indicating that Mg, Fe, Mn, and Zr are the main elements of the material; after MgFeMnZr-LDH adsorbs antimony, an Sb3d peak appears at the 539 eV position in the full spectrum, indicating that MgFeMnZr-LDH has successfully adsorbed antimony in the solution.

[0077] Study on the Adsorption Performance of Binary, Ternary and Quaternary Hydrotalcite-like Compounds on Antimony in Example 2

[0078] The preparation method of the hydrotalcite-like compound in this example is as follows:

[0079] Prepare the MgAl mixed salt solution: Weigh 5.1282 g of Mg(NO3)2·6H2O and 3.7513 g of Al(NO3)3·9H2O in a beaker, then add 100 mL of distilled water and stir to dissolve to obtain the MgAl mixed salt solution;

[0080] Preparation of MgFe mixed salt solution: Weigh 5.1282 g of Mg(NO3)2·6H2O and 4.04 g of Fe(NO3)3·9H2O into a beaker, then add 100 mL of distilled water and stir to dissolve, obtaining the MgFe mixed salt solution;

[0081] Preparation of MgFeMn mixed salt solution: Weigh 4.1026 g of Mg(NO3)2·6H2O, 4.0400 g of Fe(NO3)3·9H2O, and 0.6761 g of MnSO4·H2O into a beaker, then add 100 mL of distilled water and stir to dissolve, obtaining the MgFeMn mixed salt solution;

[0082] Preparation of MgFeMnZr mixed salt solution: Weigh 4.1026 g of Mg(NO3)2·6H2O, 4.0400 g of Fe(NO3)3·9H2O, 0.6761 g of MnSO4·H2O, and 0.4293 g of Zr(NO3)4·5H2O into a beaker, then add 100 mL of distilled water and stir to dissolve, obtaining the MgFeMnZr mixed salt solution;

[0083] Preparation of Na2CO3 alkaline solution: Weigh 2.1200 g of Na2CO3 into a beaker, add 100 mL of distilled water and stir to dissolve, obtaining 100 mL of Na2CO3 alkaline solution; Repeat to prepare a total of four groups of 100 mL of Na2CO3 alkaline solution for standby;

[0084] Under magnetic stirring, use a constant-current pump to drip the MgAl mixed salt solution, MgFe mixed salt solution, MgFeMn mixed salt solution, and MgFeMnZr mixed salt solution into four groups of Na2CO3 alkaline solutions respectively. At the same time, drip 2 mol / L sodium hydroxide solution to control the pH value to remain at 10; After the dripping is completed, continue stirring for 1 hour, place it in an 80°C oven for aging for 24 h, filter by suction, wash the obtained precipitate several times with deionized water, dry at 80°C, and then grind through a 100-mesh sieve to obtain magnesium-aluminum hydrotalcite (denoted as S2-1), magnesium-iron hydrotalcite (denoted as S2-2), magnesium-iron-manganese hydrotalcite (denoted as S2-3), and magnesium-iron-manganese-zirconium hydrotalcite (denoted as S2-4) respectively.

[0085] According to the adsorption test in Example 1, detect the removal rates (%) of magnesium-aluminum hydrotalcite, magnesium-iron hydrotalcite, magnesium-iron-manganese hydrotalcite, and magnesium-iron-manganese-zirconium hydrotalcite for heavy metal antimony in water; Adsorption test conditions: Hydrotalcite sample: 0.05 g; Adsorption liquid volume: 50 mL; Initial concentration of antimony in the adsorption liquid: 150 mg / L; Temperature: 25°C; Adsorption time: 4 h.

[0086] The result statistics of the adsorption test in this example are shown in Table 1.

[0087] Table 1

[0088] Number Hydrotalcite type Sb removal rate (%) S2-1 Magnesium-aluminum 8.19 S2-2 Magnesium-iron 43.49 S2-3 Magnesium-iron-manganese 61.50 S2-4 Magnesium-iron-manganese-zirconium 79.94

[0089] Example 3 Mn 2+ Study on the Adsorption Performance of Ternary Hydrotalcite-like Compounds with Different Addition Amounts

[0090] The steps for preparing the ternary hydrotalcite-like compounds in this example are as follows:

[0091] Weigh iron salt (Fe(NO3)3·9H2O), different masses of magnesium salt (Mg(NO3)2·6H2O) and different masses of manganese salt (MnSO4·H2O) into a small beaker (keep Mg 2+ +Mn 2+ = 0.02 mol, Fe 3+ = 0.01 mol), then add 100 mL of distilled water, stir to dissolve, and obtain 9 groups of mixed salt solutions with different dosages of Mg and Mn (denoted as A3-1 to A3-9);

[0092] The dosage statistics of each raw material in A3-1 to A3-9 are shown in Table 2.

[0093] Table 2

[0094]

[0095] Meanwhile, weigh 2.1200 g of Na2CO3 into a beaker, add 100 mL of distilled water, stir to dissolve; repeat to prepare 9 groups of alkali solutions for standby;

[0096] Under magnetic stirring, use a constant flow pump to dropwise add the mixed salt solutions of A3-1 to A3-9 into the beaker containing the alkali solution one by one. At the same time, add 2 mol / L sodium hydroxide solution to control the pH value at 10; after the addition is completed, continue to stir for 1 hour, place it in an 80°C oven for aging for 24 h, filter by suction, wash the obtained precipitate several times with deionized water, dry at 80°C, and then grind it through a 100-mesh sieve to obtain magnesium-manganese-iron ternary hydrotalcite-like compounds (denoted as S3-1 to S3-9).

[0097] Based on the adsorption test in Example 1, detect the removal rate (%) of heavy metal antimony in water by S3-1 to S3-9 in this example; the conditions for the adsorption test are: S3-1 to S3-9: 0.05 g; adsorption liquid volume: 50 mL; initial concentration of antimony in the adsorption liquid: 150 mg / L; temperature: 25°C; adsorption time: 4 h.

[0098] The result statistics of the adsorption test of S3-1 to S3-9 in this example are shown in Table 3.

[0099] Table 3

[0100] Number <![CDATA[Mn 2+ Addition amount (mol)]]> Sb removal rate (%) S3-1 0 43.49 S3-2 0.0002 44.57 S3-3 0.0006 48.19 S3-4 0.001 50.08 S3-5 0.002 54.36 S3-6 0.003 56.09 S3-7 0.004 61.50 S3-8 0.005 62.79 S3-9 0.010 64.25

[0101] As can be seen from Table 3, as the Mn content in the hydrotalcite-like compound increases from 0 to 0.010 mol, the removal rate of antimony increases from 43.49% to 64.25%. When the Mn content is less than 0.004 mol, the removal rate of antimony increases rapidly. When the Mn content is greater than 0.004 mol, the removal rate of antimony increases slowly and reaches equilibrium, with a maximum increase of 21% compared to the case without addition. Hydrotalcite is a layered metal hydroxide, and the layer board is mainly composed of metal ions. Mn has a good adsorption effect on antimony. Replacing part of Mg with Mn can effectively increase the removal rate of heavy metal antimony. However, the precipitation of Mn may cause pollution. Therefore, the optimal addition amount of Mn in the hydrotalcite-like compound is 0.004 mol. 2+ As the addition amount of Mn increases from 0 to 0.010 mol, the removal rate of antimony increases from 43.49% to 64.25%. When the addition amount of Mn 2+ is less than 0.004 mol, the removal rate of antimony increases rapidly. When the addition amount of Mn 2+ is greater than 0.004 mol, the removal rate of antimony increases slowly and reaches equilibrium, with a maximum increase of 21% compared to the case without addition. Hydrotalcite is a layered metal hydroxide, and the layer board is mainly composed of metal ions. Mn 2+ has a good adsorption effect on antimony. Adding Mn 2+ to replace part of Mg 2+ can effectively increase the removal rate of heavy metal antimony. However, the precipitation of Mn 2+ may cause pollution. Therefore, the optimal addition amount of Mn in the hydrotalcite-like compound is 0.004 mol. 2 +

[0102] Example 4 Study on the Adsorption Performance of Quaternary Hydrotalcite-like Compounds with Different Zr Addition Amounts 4+ The steps for preparing the quaternary hydrotalcite-like compound in this example are as follows:

[0103] Weigh magnesium salt (Mg(NO3)2·6H2O), iron salt (Fe(NO3)3·9H2O), manganese salt (MnSO4·H2O) and different masses of zirconium salt (Zr(NO3)4·5H2O) into a beaker, then add 100 mL of distilled water and stir to dissolve to obtain 9 groups of mixed salt solutions (denoted as A4-1 to A4-9).

[0104] The usage statistics of each raw material in the 9 groups of mixed salt solutions are shown in Table 4.

[0105]

[0106] Table 4

[0107]

[0108] At the same time, weigh 2.1200 g of Na2CO3 into a beaker, add 100 mL of distilled water and stir to dissolve to obtain an alkali solution; repeat the operation to prepare 9 groups of alkali solutions for standby;

[0109] Under magnetic stirring, use a constant flow pump to drop the A4-1 to A4-9 mixed salt solutions into the beaker containing the alkali solution drop by drop. At the same time, add 2 mol / L sodium hydroxide solution to control the pH value at 10. After the dropping is completed, continue to stir for 1 hour, place it in an 80°C oven for aging for 24 hours, perform suction filtration, wash the obtained precipitate with deionized water several times, dry it at 80°C and then grind it through a 100-mesh sieve to obtain the magnesium-iron-manganese-zirconium quaternary hydrotalcite-like compound (denoted as S4-1 to S4-9).

[0110] Based on the adsorption test of Example 1, the removal rate (%) of heavy metal antimony in water by S4-1 to S4-9 of this example was detected; the conditions of the adsorption test were: S4-1 to S4-9: 0.05 g; adsorption liquid volume: 50 mL; initial concentration of antimony in the adsorption liquid 150 mg / L; temperature: 25 °C; adsorption time: 4 h.

[0111] The results of the adsorption test of S4-1 to S4-9 of this example are statistically shown in Table 5.

[0112] Table 5

[0113] Number <![CDATA[Zr 4+ Addition amount (mol)]]> Sb removal rate (%) S4-1 0 64.06 S4-2 0.0001 65.74 S4-3 0.0003 73.41 S4-4 0.0005 73.98 S4-5 0.0007 75.04 S4-6 0.001 79.94 S4-7 0.0012 81.53 S4-8 0.0015 82.06 S4-9 0.002 81.77

[0114] As can be seen from Table 5, as the addition amount of Zr 4+ increases from 0 to 0.002 mol, the removal rate of antimony increases from 64.06% to 81.77%; when the addition amount of Zr 4+ is less than 0.001 mol, the removal rate of antimony increases rapidly. When the addition amount of Zr 4+ is greater than 0.001 mol, the removal rate of antimony increases slowly and reaches equilibrium. The maximum removal rate of antimony increases by 18% compared with when Zr 4+ is not added; therefore, Zr 4+ has a good adsorption effect on antimony. Adding Zr 4+ can effectively increase the removal rate of heavy metal Sb, but when the addition amount of Zr 4 + exceeds 0.001 mol, the increase in the removal rate is small, and it may damage the hydrotalcite structure. Therefore, it is optimal to control the addition amount of Zr 4+ at 0.001 mol.

[0115] Study on the Adsorption Performance of Quaternary Hydrotalcite by Na2CO3 Concentration in Example 5

[0116] The steps for preparing the quaternary hydrotalcite in this example are as follows:

[0117] Weigh 4.1026 g of magnesium salt (Mg(NO3)2·6H2O), 4.0400 g of iron salt (Fe(NO3)3·9H2O), 0.6761 g of manganese salt (MnSO4·H2O) and 0.4293 g of zirconium salt (Zr(NO3)4·5H2O) into a 100 mL small beaker, then add 100 mL of distilled water, stir and dissolve to obtain a mixed salt solution; repeat to prepare 9 groups of mixed salt solutions for standby;

[0118] Weigh 9 different masses of Na2CO3 (0 g, 0.0530 g, 0.1060 g, 0.2120 g, 0.3180 g, 0.5300 g, 0.7419 g, 1.0599 g, 2.1198 g respectively) into a 250 mL beaker, add 100 mL of distilled water, stir to dissolve, and obtain alkaline solutions with different Na2CO3 concentrations (denoted as A5-1 to A5-9);

[0119] Under magnetic stirring, use a constant flow pump to drop the mixed salt solution into the beaker containing the alkaline solution drop by drop. At the same time, add 2 mol / L sodium hydroxide solution to control the pH value at 10; continue to stir for 1 hour after the dropping is completed, place it in an 80°C oven for aging for 24 h, perform suction filtration, wash the obtained precipitate several times with deionized water, dry it at 80°C, and then grind it through a 100-mesh sieve to obtain magnesium-iron-manganese-zirconium hydrotalcite (denoted as S5-1 to S5-9).

[0120] Based on the adsorption test in Example 1, detect the removal rate (%) of heavy metal antimony in water by S5-1 to S5-9 in this example; the conditions for the adsorption test are: S5-1 to S5-9: 0.05 g; adsorption liquid volume: 50 mL; initial concentration of antimony in the adsorption liquid: 150 mg / L; temperature: 25°C; adsorption time: 4 h.

[0121] The results of the adsorption test of S5-1 to S5-9 in this example are statistically shown in Table 7.

[0122] Table 7

[0123]

[0124]

[0125] As can be seen from Table 7, the removal rate of antimony by S4-1 to S4-9 first increases and then decreases with the increase of the Na2CO3 concentration; when the Na2CO3 concentration is 0.01 mol / L, the removal rate of the prepared hydrotalcite for antimony is the highest, which is 81.49%.

[0126] Study on the effect of pH value of stirring reaction in Example 6 on the adsorption performance of quaternary hydrotalcite

[0127] The steps for preparing quaternary hydrotalcite in this example are as follows:

[0128] Weigh 4.1026 g of magnesium salt (Mg(NO3)2·6H2O), 4.0400 g of iron salt (Fe(NO3)3·9H2O), 0.6761 g of manganese salt (MnSO4·H2O), and 0.4293 g of zirconium salt (Zr(NO3)4·5H2O) into a beaker, then add 100 mL of distilled water, stir to dissolve, and obtain a mixed salt solution; repeat to obtain 8 groups of mixed salt solutions for standby;

[0129] Weigh 0.1060 g of Na2CO3 into another beaker, add 100 mL of distilled water, stir to dissolve, and obtain an alkali solution; repeat to obtain 8 groups of alkali solutions for standby;

[0130] Dropwise add 2 mol / L sodium hydroxide solution to adjust the pH values of the solutions to 7, 7.5, 8, 9, 9.5, 10, 10.5, 11, 12, and 13 respectively; continue to stir for 1 hour after the addition, place in an 80 °C oven for aging for 24 h, perform suction filtration, wash the obtained precipitate with deionized water several times, dry at 80 °C, and grind through a 100-mesh sieve to obtain a magnesium-iron-manganese-zirconium quaternary hydrotalcite-like material (denoted as S6-1 to S6-10).

[0131] Based on the adsorption test of Example 1, detect the removal rates (%) of heavy metal antimony in water by S6-1 to S6-10 in this example; the conditions for the adsorption test are: S6-1 to S6-10: 0.05 g; adsorption liquid volume: 50 mL; initial concentration of antimony in the adsorption liquid: 150 mg / L; temperature: 25 °C; adsorption time: 4 h.

[0132] The results of the adsorption tests of S6-1 to S6-9 in this example are statistically shown in Table 8.

[0133] Table 8

[0134] Number pH value Sb removal rate (%) S6-1 7 57.02 S6-2 7.5 70.03 S6-3 8 95.68 S6-4 9 94.35 S6-5 9.5 90.33 S6-6 10 86.88 S6-7 10.5 85.65 S6-8 11 83.44 S6-9 12 80.02 S6-10 13 77.70

[0135] As can be seen from Table 8, the removal rates of antimony by S6-1 to S6-8 first increase and then decrease with the increase of the reaction pH value; when the pH value is 8, the highest removal rate of the prepared hydrotalcite material for antimony is 95.68%.

[0136] Perform XRD characterization on the quaternary hydrotalcite-like materials of S6-3, S6-4, S6-5, S6-6, and S6-7, and the results are as follows Figure 4 shown.

[0137] See the appendix Figure 4 , when the pH value ≤ 9.5, the prepared quaternary hydrotalcite-like materials do not have the characteristic peaks corresponding to hydrotalcite-like at diffraction angles 2θ of 10.8°, 22.6°, 33.7°, and 60.4°, indicating that S6-3, S6-4, and S6-5 are not hydrotalcite-like; when the pH value ≥ 10, S6-6 and S6-7 have the characteristic structure of hydrotalcite-like; when the pH value is 10, the removal rate of antimony at this time is 86.88%.

[0138] Study on the adsorption performance of the quaternary hydrotalcite in Example 7

[0139] In this example, the MgFeMnZr-LDH material of Example 1 is used as the object for studying the adsorption performance.

[0140] I. Research on the Adsorption Conditions of Antimony

[0141] 1. Study the effect of the dosage of MgFeMnZr-LDH material on the removal of antimony

[0142] Weigh 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10 g of MgFeMnZr-LDH material respectively, add them to 50 mL of 200 mg / L antimony solution, and conduct adsorption experiments at 25 °C.

[0143] The curves of antimony adsorption rate (R) and adsorption capacity (Qa) of the MgFeMnZr-LDH material in Example 1 under different solid-liquid ratios are as shown in the appendix Figure 5 where the solid-liquid ratio refers to the ratio of the mass of the MgFeMnZr-LDH material to the volume of the antimony solution.

[0144] See the appendix Figure 5 . As the addition amount of the MgFeMnZr-LDH material increases, the adsorption capacity for antimony gradually decreases, but the removal rate of antimony gradually increases; when the dosage of the MgFeMnZr-LDH material is low, the adsorption active sites on the material are limited and it is easy to reach the saturated adsorption state; as the dosage of the MgFeMnZr-LDH material increases, the number of adsorption active sites increases, and a large number of active sites are in the unsaturated adsorption state, so that the removal rate of antimony by the hydrotalcite increases and the equilibrium adsorption amount decreases.

[0145] 2. Study the effect of the initial concentration of antimony on the removal of antimony

[0146] Weigh 0.05 g of MgFeMnZr-LDH material and add it to 50 mL of antimony solutions with concentrations of 20, 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 mg / L respectively, and conduct adsorption experiments at 25 °C.

[0147] The curves of antimony adsorption rate (R) and adsorption capacity (Qa) of the MgFeMnZr-LDH material in Example 1 under different initial antimony concentrations are as shown in the appendix Figure 6 as shown.

[0148] See the appendix Figure 6 . As the initial concentration of antimony increases, the adsorption capacity gradually increases and the removal rate of antimony gradually decreases; when the mass of the MgFeMnZr-LDH material is the same, a higher concentration of antimony solution can increase the driving force of antimony from the aqueous phase to the solid phase to overcome its mass transfer resistance, so that more antimony enters the interlayer of the hydrotalcite; at the same time, the higher the mass transfer force of the higher antimony concentration makes antimony fully combine with the adsorption sites on the hydrotalcite, and the adsorption amount increases significantly.

[0149] 3. Study the effect of the pH value of the antimony solution on antimony removal

[0150] Weigh 0.05 g of the MgFeMnZr-LDH material and add it to 50 mL of an antimony solution with a concentration of 200 mg / L. Adjust the pH values of the solution to 2.0, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, and 7.0 respectively, and conduct the adsorption experiment at 25 °C.

[0151] The curves of the dissolution amounts of Fe and Mn and the antimony adsorption rate (R) of the MgFeMnZr-LDH material in Example 1 under different pH values of the antimony solution are as shown in the appendix Figure 7 as follows.

[0152] See the appendix Figure 7 . Except when the pH value of the antimony solution is 2, as the pH value of the antimony solution increases, the removal rate of antimony by the MgFeMnZr-LDH material remains basically unchanged; since the MgFeMnZr-LDH material is a layered metal hydroxide, when the pH value of the antimony solution is 2, its strong acidity may dissolve the MgFeMnZr-LDH material, causing partial precipitation of iron and manganese ions, and thus leading to a decrease in the adsorption amount of antimony by the MgFeMnZr-LDH material. Therefore, the MgFeMnZr-LDH material cannot adsorb antimony under strong acidic (pH value ≤ 2) conditions; when the pH value of the antimony solution is greater than 2, no iron or manganese is detected in the solution after adsorption, and the material is stable; within the range of pH values of 3-6 for the antimony solution, the MgFeMnZr-LDH material has a very high adsorption efficiency for antimony, and the applicable pH value range of the material is wide.

[0153] 4. Study the effect of adsorption time on antimony removal

[0154] Weigh 0.30 g of the MgFeMnZr-LDH material and add it to 300 mL of an antimony solution with a concentration of 200 mg / L. Adjust the solution pH = 4.5 and conduct the adsorption experiment at 25 °C. Take the supernatant for determination at 5, 10, 20, 30, 40, 50, 60, 80, 100, 120, 150, 180, 210, 300, and 360 min respectively during the adsorption experiment.

[0155] The antimony adsorption rate curves of the MgFeMnZr-LDH material in Example 1 at different adsorption times are as shown in the appendix Figure 8 as follows.

[0156] See the appendix Figure 8 . After 150 min of adsorption, the adsorption has basically reached equilibrium, and the antimony removal rate is 89.65%.

[0157] 5. Study the effect of adsorption temperature on antimony removal

[0158] Weigh 0.30 g of the MgFeMnZr-LDH material separately and add it to 300 mL of an antimony solution with a concentration of 200 mg / L. Adjust the pH to 4.5 for the adsorption experiment. Conduct the adsorption experiments at 25 °C, 35 °C, and 45 °C respectively, and take the supernatant for measurement at 5, 10, 20, 30, 40, 50, 60, 80, 100, 120, 150, 180, 210, 240, 300, 360 min at each adsorption temperature.

[0159] The curves of the antimony adsorption rate of the MgFeMnZr-LDH material in Example 1 at different adsorption temperatures and times are as shown in the appendix Figure 9 as follows.

[0160] See the appendix Figure 9 . As the adsorption temperature increases from 25 °C to 45 °C, when the adsorption equilibrium is reached, the change in the antimony removal rate is not obvious, and the temperature has a minimal impact.

[0161] 6. Study the influence of competitive ions on the removal of antimony

[0162] Weigh 0.05 g of the MgFeMnZr-LDH material separately and add it to 50 mL of an antimony solution with a concentration of 200 mg / L. Then add 0, 0.02, 0.05, 0.10, 0.20, 0.30, 0.50 mol / L of KNO3, K2SO4, KCl, NaHCO3, or KH2PO4 as competitive ions respectively for the adsorption experiment.

[0163] The curves of the antimony adsorption rate of the MgFeMnZr-LDH material in Example 1 under different concentrations of competitive ions are as shown in the appendix Figure 10 as follows.

[0164] See the appendix Figure 10 . When KNO3, K2SO4, and KCl are used as competitive ions, the increase in anions and cations has basically no effect on the removal of antimony by the material. When NaHCO3 is used as a competitive ion, as the ionic strength of anions and cations increases, the removal rate of antimony by the material slightly decreases. When the concentration of NaHCO3 reaches 0.50 mol / L, the maximum decrease in the removal rate is 11%. When KH2PO4 is used as a competitive ion, as the ionic strength of anions and cations increases, the removal rate of antimony by the material gradually decreases. When the concentration reaches 0.50 mol / L, the maximum decrease in the removal rate is 32%. This is because P and Sb are in the same main group and have similar properties. H2PO4 - as a competitive ion competes with antimony for the adsorption sites of the material, resulting in a decrease in the removal rate of the MgFeMnZr-LDH material.

[0165] 7. Study on the saturation capacity of the MgFeMnZr-LDH material for antimony

[0166] Antimony solutions with concentrations of 50, 100, 200, 300, 400, 500, 600, 700, and 800 mg / L were prepared respectively. 50 mL of the solution was taken and 0.05 g of the MgFeMnZr-LDH material was added, followed by shaking and adsorbing for 4 h at 25 °C.

[0167] The curves of the saturated adsorption capacity (Qe) of the MgFeMnZr-LDH material for antimony at different Sb concentrations in Example 1 are shown in the appendix Figure 11 as follows.

[0168] See the appendix Figure 11 . As the antimony concentration increases, the saturated adsorption amount of the MgFeMnZr-LDH material for antimony continuously increases. When the concentration of the antimony solution is 500 mg / L, it basically reaches equilibrium. At this time, the saturated adsorption capacity of MgFeMnZr-LDH for antimony is 207.35 mg / g.

Claims

1. A preparation method of a quaternary hydrotalcite-like compound, characterized in that, It includes the following steps: 1): Weigh magnesium salt, manganese salt, iron salt and zirconium salt, and add water to prepare a mixed salt solution with a volume of V1; 2): Weigh Na2CO3, and add water to prepare an alkali solution with a volume of V2; 3): Drop the mixed salt solution in step 1) into the alkali solution in step 2) and stir for reaction to obtain a reaction solution; 4): Age and filter the reaction solution in step 3), wash the filter cake and dry it to obtain a quaternary hydrotalcite-like material.

2. The preparation method according to claim 1, characterized in that: In step 1), the molar ratio of magnesium salt to manganese salt is (10 - 16):(4 - 10), and the molar ratio of magnesium salt + manganese salt, iron salt, zirconium salt is 20:(8 - 10):1; Preferably, the magnesium salt is any one or any combination of magnesium chloride, magnesium nitrate, magnesium sulfate and their hydrates; Preferably, the manganese salt is any one or any combination of manganese chloride, manganese nitrate, manganese sulfate and their hydrates; Preferably, the iron salt is any one or any combination of iron chloride, iron nitrate, iron sulfate and their hydrates; The zirconium salt is any one or any combination of zirconium nitrate, zirconium sulfate and their hydrates.

3. The preparation method according to claim 2, wherein: In step 1), the concentration of magnesium in the mixed salt solution is 0.10 - 0.16 mol / L.

4. The preparation method according to claim 1, wherein: In step 2), the volume V2 is equal to the volume V1.

5. The preparation method according to claim 1, characterized in that: In step 2), the concentration of Na2CO3 in the alkali solution is 0.01 - 0.02 mol / L.

6. The preparation method according to claim 1, characterized in that: In step 3), the temperature of the stirring reaction is 10 - 40 °C, and the time is 30 - 60 min; the pH value of the stirring reaction is controlled to be 10 - 12; Preferably, the pH value control is to drop a 2 mol / L sodium hydroxide solution during the stirring reaction.

7. The preparation method according to claim 1, characterized in that: In step 4), the aging treatment is carried out in an oven at 70 - 90 °C for 12 - 24 h; the drying temperature is 80 - 105 °C.

8. The preparation method according to claim 1, characterized in that: In step 4), the particle size of the quaternary hydrotalcite-like material is ≤100 mesh.

9. A quaternary hydrotalcite-like material prepared by the preparation method according to any one of claims 1 - 8.

10. Use of the quaternary hydrotalcite described in claim 9 for adsorbing heavy metals, characterized in that, The heavy metal is antimony.

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