Magnesium-based nano targeted cadmium removal material and preparation method thereof

Abstract

The invention discloses nano magnesium oxide for targeted adsorption of heavy metals and a preparation method thereof, the preparation method comprises the following steps: S1, adding a dispersion stabilizer into a magnesium solution, and stirring to obtain a solution A; s2, adding a regulator into the solution A under a stirring condition to obtain a solution B; and S3, after standing, stabilizing and aging, collecting a solid precipitate, and carrying out multi-stage heat treatment to prepare the ultra-dispersed nano magnesium oxide material. The nano magnesium oxide has a relatively high specific surface area and a nano targeting site, the heavy metal cadmium is removed under a complex background condition through the principles of ion exchange and interface inner ring complexing capture, the adsorption capacity can reach 2,400 mg / g or above, and the ultra-dispersed nano magnesium oxide is simple in preparation method, low in production cost and worthy of popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of functional materials, and in particular relates to a method for removing heavy metal cadmium by adsorbing nano magnesium oxide. Background Art

[0002] With the acceleration of industrialization, water pollution is becoming increasingly serious, especially the pollution of heavy metal cadmium. Heavy metal cadmium is extremely harmful to the environment and human health. Therefore, it is of great significance to develop effective cadmium ion removal technology. Traditional heavy metal removal methods such as chemical precipitation, ion exchange and membrane filtration have problems such as high cost, complex operation, and certain difficulties in large-scale application. And they usually lack targeted selectivity for cadmium. Since the environment may contain a variety of other metal ions and impurities, these substances often compete with cadmium, resulting in affected removal effects. Therefore, traditional methods are often difficult to remove cadmium efficiently under complex environmental conditions, especially in the case of multi-metal pollution.

[0003] In recent years, metal oxide adsorption materials have received widespread attention. Among them, nano magnesium oxide (MgO) has been widely studied for wastewater treatment due to its high specific surface area, good adsorption performance and non-toxic and harmless characteristics, especially showing great potential in removing heavy metal ions. The adsorption capacity of heavy metals by traditional synthetic magnesium oxide can easily exceed 500 mg / g, while the adsorption capacity of heavy metals by nano-magnesium oxide adsorbents synthesized in the laboratory can exceed 2000 mg / g. However, at present, the synthesis process of nano magnesium oxide materials with high adsorption capacity synthesized in the laboratory is complicated, and some of the synthesis processes still require the use of special instruments and equipment, and the production cost is still high.

[0004] Therefore, this study is dedicated to developing a method for preparing nano magnesium oxide materials with high heavy metal adsorption performance, which has simple preparation methods, low production costs, and targeted adsorption capabilities, so as to facilitate promotion. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing nano magnesium oxide for targeted adsorption of heavy metal cadmium in view of the shortcomings of the prior art. Compared with the prior art, the preparation process of the nano magnesium oxide of the present invention is simple and easy to expand production. The prepared nano magnesium oxide material has a large adsorption capacity.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing a nano magnesium oxide material comprises the following steps:

[0008] S1 adds a dispersing stabilizer to the magnesium solution, and obtains solution A after stirring;

[0009] S2 adds a regulator to solution A under stirring to obtain solution B;

[0010] S3 collects the solid precipitate after being allowed to stand for stable aging, and prepares the nano-magnesium oxide material through multi-stage heat treatment.

[0011] Preferably, as a better embodiment, the dispersing stabilizer in S1 includes but is not limited to a compound of different molecular weight PEG (400, 10000, 20000, 35000) and a polyhydroxy stabilizer: guar gum, xanthan gum or a polycarboxylic acid stabilizer: CMC, citric acid, and the compounding ratio depends on the molecular weight of PEG and the ratio of hydroxyl and carboxylic acid functional groups, and the preferred range is 1-3:0-5.

[0012] Preferably, as a preferred embodiment, the magnesium solution precursor in step S1 includes but is not limited to one or more of an inorganic magnesium source: magnesium nitrate, magnesium chloride, an organic magnesium source: magnesium acetate, and particulate magnesium oxide. Depending on the type of dispersant, the weight ratio of magnesium content to dispersion stabilizer is 2-5:1-10.

[0013] Preferably, as a better embodiment, the regulator in step S2 includes but is not limited to one or more of sodium hydroxide, sodium carbonate, sodium sulfide, and sodium thiosulfate.

[0014] Preferably, as a better implementation, the stable aging in step S3 is performed at a temperature of 50 to 80° C. for 6 to 12 hours.

[0015] Preferably, as a preferred embodiment, the heat treatment in step S3 is carried out in a protective atmosphere, the heat treatment is heated to 100-300°C at 5-20°C / min and calcined for 0-3h, and then heated to 500-700°C at 5-20°C / min and calcined for 1-3h.

[0016] Another object of the present invention is to provide an application of the nano magnesium oxide material for removing heavy metal pollution.

[0017] Preferably, as a preferred embodiment, the heavy metal is cadmium.

[0018] Preferably, as a preferred embodiment, the adsorption capacity of the nano-magnesium oxide material of the present invention for adsorbing heavy metal cadmium can be as high as 2487 mg / g.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The nano magnesium oxide material of the present invention adopts polyhydroxy and polycarboxylic acid-based dispersants, and the material can be better distributed in the matrix during the dispersion process, and has excellent dispersibility and stability.

[0021] (2) The nano-magnesium oxide material of the present invention has multiple active sites for targeted adsorption of heavy metals, which can not only enhance the adsorption capacity of heavy metal ions, but also effectively improve the adaptability and adsorption efficiency of the material in complex environments.

[0022] (3) The adsorption capacity of the nano-magnesium oxide of the present invention for heavy metal cadmium is as high as 2487 mg / g;

[0023] (4) The nano magnesium oxide material preparation method of the present invention is simple, has low production cost, and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The following is a flow chart showing the preparation process of nano magnesium oxide according to a preferred embodiment of the present invention;

[0025] Figure 2 The XRD diagram of nano magnesium oxide prepared in the embodiment of the present invention is shown.

[0026] Figure 3 The figure shows the adsorption effect of nano magnesium oxide prepared in Example 3 of the present invention in the presence of coexisting cations. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The following specific implementation methods further describe the present invention.

[0028] Unless otherwise specified, the chemical substances of the present invention can be purchased from the market.

[0029] 1. Preparation Example

[0030] 1. Embodiment 1

[0031] A method for preparing a nano magnesium oxide material comprises the following steps:

[0032] (1) Weigh 4.75 g of magnesium nitrate and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 1 g of PEG10000 and 4 g of xanthan gum in 100 ml of ultrapure water. Mix the two well to obtain solution A, and stir solution A for 30 min.

[0033] (2) Dissolve 4 g of sodium hydroxide in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0034] (3) removing the supernatant and aging at 50°C for 12 h; heating the precipitate to 100°C for 1 h at a heating rate of 10°C / min under a nitrogen atmosphere, and then heating to 600°C at a heating rate of 10°C / min for 2 hours to obtain the final product, nano-magnesium oxide material.

[0035] 2. Embodiment 2

[0036] A method for preparing a nano magnesium oxide material comprises the following steps:

[0037] (1) Weigh 4.75 g of magnesium acetate and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 1 g of PEG20000 and 3 g of guar gum in 100 ml of ultrapure water. Mix the two well to obtain solution A, and stir solution A for 30 min.

[0038] (2) Dissolve 4 g of sodium sulfide in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0039] (3) removing the supernatant and aging at 50°C for 12 h; heating the precipitate to 200°C in a nitrogen atmosphere at a heating rate of 10°C / min and calcining for 1 h, and then heating to 600°C at a heating rate of 10°C / min and calcining for 2 hours to obtain the final product, nano-magnesium oxide material.

[0040] 3. Embodiment 3

[0041] A method for preparing a nano magnesium oxide material comprises the following steps:

[0042] (1) Weigh 4.75 g of magnesium chloride and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 3 g of PEG20000 in 100 ml of ultrapure water. Mix the two well to obtain solution A. Stir solution A for 30 min.

[0043] (2) Dissolve 4 g of sodium hydroxide in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0044] (3) removing the supernatant and aging at 50° C. for 12 h; calcining the precipitate at 600° C. for 2 h under a nitrogen atmosphere at a heating rate of 10° C. / min to obtain the final product, nano-magnesium oxide.

[0045] 4. Embodiment 4

[0046] A method for preparing a nano magnesium oxide material comprises the following steps:

[0047] (1) Weigh 4.75 g of magnesium chloride and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 1 g of PEG35000 and 2 g of citric acid in 100 ml of ultrapure water. Mix the two well to obtain solution A, and stir solution A for 30 min.

[0048] (2) Dissolve 4 g of sodium thiosulfate in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0049] (3) removing the supernatant and aging at 50°C for 12 h; heating the precipitate to 300°C in a nitrogen atmosphere at a heating rate of 10°C / min and calcining for 1 h, and then heating to 600°C at a heating rate of 10°C / min and calcining for 2 hours to obtain the final product, nano-magnesium oxide material.

[0050] 5. Embodiment 5

[0051] A method for preparing a nano magnesium oxide material comprises the following steps:

[0052] (1) Weigh 4.75 g of magnesium oxide, dissolve 1 g of PEG20000 and 5 g of CMC in 100 ml of ultrapure water, mix the two well to obtain solution A, and stir solution A for 30 min;

[0053] (2) Dissolve 4 g of sodium carbonate in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0054] (3) removing the supernatant and aging at 50°C for 12 h; heating the precipitate to 200°C in a nitrogen atmosphere at a heating rate of 10°C / min and calcining for 1 h, and then heating to 600°C at a heating rate of 10°C / min and calcining for 2 hours to obtain the final product, nano-magnesium oxide material.

[0055] 6. Embodiment 6

[0056] A method for preparing a nano magnesium oxide material comprises the following steps:

[0057] (1) Weigh 4.75 g of magnesium chloride and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 3 g of PEG20000 in 100 ml of ultrapure water. Mix the two well to obtain solution A. Stir solution A for 30 min.

[0058] (2) Dissolve 4 g of sodium hydroxide in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0059] (3) removing the supernatant and aging at 50° C. for 12 h; heating the precipitate to 500° C. in a nitrogen atmosphere at a rate of 10° C. / min and calcining for 2 h to obtain the final product, nano-magnesium oxide material.

[0060] 7. Embodiment 7

[0061] A method for preparing a nano magnesium oxide material comprises the following steps:

[0062] (1) Weigh 4.75 g of magnesium chloride and dissolve it in 100 ml of ultrapure water. Similarly, dissolve 3 g of PEG20000 in 100 ml of ultrapure water. Mix the two well to obtain solution A. Stir solution A for 30 min.

[0063] (2) Dissolve 4 g of sodium hydroxide in 100 ml of ultrapure water to obtain solution B, and slowly add solution B to solution A under stirring conditions, and stir for 15 min;

[0064] (3) removing the supernatant and aging at 50° C. for 12 h; heating the precipitate to 700° C. in a nitrogen atmosphere at a rate of 10° C. / min and calcining for 2 h to obtain the final product, nano-magnesium oxide material.

[0065] 2. Application Examples

[0066] The specific operation of the adsorption experiment is as follows: the initial Cd(II) concentration is 3000 mg / L, pH = 6, T = 25°C. Add 50 ml of Cd(II) solution to a centrifuge tube, weigh 50 mg of MgO material and add it to the centrifuge tube, and oscillate the centrifuge tube for 24 hours (speed 200 rpm). After the adsorption reaction is completed, the supernatant is extracted and filtered through a 0.22 um filter membrane, and the remaining cadmium in the solution of the centrifuge tube is quantitatively analyzed using an atomic absorption spectrometer.

[0067] As shown in Table 1, Table 1 shows the effect of the addition of dispersion stabilizer and temperature on the adsorption capacity of nano-magnesium oxide material. It can be seen from Table 1 that the magnesium oxide material prepared by adding dispersion stabilizer has excellent adsorption capacity, and the heat treatment temperature has a certain effect on the adsorption capacity of nano-magnesium oxide material. When the addition amount of dispersant PEG20000 is 3g and the heat treatment temperature is 600℃, the prepared nano-magnesium oxide material has the best adsorption performance, up to 2487mg / g.

[0068] Table 1 Comparison of the effects of dispersion stabilizer and temperature on the adsorption capacity of nano magnesium oxide materials

[0069]

[0070] like Figure 3 As shown, it can be seen that Ca in the solution 2+ , K + 、Na+ The presence of Ca has little effect on the adsorption of Cd(II) on MgO. 2+ , K + 、Na + As the concentration increases from 100 mg / l to 300 mg / l, the adsorption efficiency of MgO prepared in Example 3 for Cd(II) remains at 2300 mg / g, while Cu 2+ The increase in concentration reduced the Cd(II) removal efficiency of MgO (down to 1800 mg / g). Although these cations had a certain impact on the adsorption performance of MgO by competing for adsorption sites, the MgO material still showed efficient targeted removal of cadmium ions.

[0071] The above embodiments are preferred implementation schemes of the present invention. In addition, the present invention may also be implemented in other ways. Any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for preparing a nano magnesium oxide material, characterized in that: The steps include: S1 adds a dispersion stabilizer to the magnesium solution, and obtains solution A after stirring; S2 adds a regulator to solution A under stirring to obtain solution B; S3 collects solid precipitates after standing still for stable aging, and obtains ultra-dispersed nano-magnesium oxide materials through multi-stage heat treatment.

2. The method for preparing a nano magnesium oxide material according to claim 1, characterized in that: The dispersing stabilizer in S1 includes but is not limited to a combination of PEG with different molecular weights (400, 10000, 20000, 35000) and polyhydroxy stabilizers: guar gum, xanthan gum or polycarboxylic acid stabilizers: CMC, citric acid. The combination ratio depends on the ratio of PEG molecular weight to hydroxyl or carboxylic acid functional groups, preferably in the range of 1-3:0-5.

3. The method for preparing a nano magnesium oxide material according to claim 1, characterized in that: The magnesium solution precursor in step S1 includes but is not limited to one or more of an inorganic magnesium source: magnesium nitrate, magnesium chloride, an organic magnesium source: magnesium acetate, and particulate magnesium oxide. Depending on the type of dispersion stabilizer, the weight ratio of magnesium content to dispersion stabilizer is 2-5:1-10.

4. The method for preparing a nano magnesium oxide material according to claim 1, characterized in that: The regulator in step S2 includes, but is not limited to, one or more of sodium hydroxide, sodium carbonate, sodium sulfide, and sodium thiosulfate.

5. The method for preparing a nano magnesium oxide material according to claim 1, characterized in that: The stable aging in step S3 is carried out at a temperature of 50 to 80° C. for 6 to 12 hours.

6. The method for preparing a nano magnesium oxide material according to claim 1, characterized in that: The heat treatment is carried out in a protective atmosphere. The heat treatment in step S3 is to heat the material to 100-300° C. at a rate of 5-20° C. / min and calcine for 0-3 h, and then heat the material to 500-700° C. at a rate of 5-20° C. / min and calcine for 1-3 h.

7. Use of the nano magnesium oxide material according to any one of claims 1 to 6 for removing heavy metals.

8. The use according to claim 7, characterized in that: The heavy metal is cadmium.

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