Preparation method of Schwertmannite with increased specific surface area

Abstract

The invention relates to the technical field of water pollution treatment, in particular to a preparation method of Schwertmannite with an increased specific surface area. The method comprises the following steps: (1) dissolving ferrous sulfate heptahydrate in distilled water to obtain a ferrous sulfate solution; and (2) adding a hydrogen peroxide solution into the ferrous sulfate solution obtained in the step (1) in an atomized form, stirring, filtering, washing, and then carrying out vacuum drying to obtain the Schwertmannite. The hydrogen peroxide solution is added into a reaction system in an atomization mode, and a traditional dropwise adding mode is replaced, so that the contact area of the hydrogen peroxide solution and the ferrous sulfate heptahydrate is increased, the reaction uniformity and efficiency are enhanced, the utilization rate of the hydrogen peroxide solution is increased, the utilization amount of the hydrogen peroxide solution is reduced, and the cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of water pollution treatment, and more particularly, to a method for preparing schwertmannite with an increased specific surface area. Background Art

[0002] Arsenic is a highly toxic and carcinogenic element that mainly exists in the form of sulfide minerals in nature and often enters water bodies due to natural and human activities, seriously affecting the natural environment and human health. Schwertmannite is an iron hydroxy sulfate mineral that is often used as an environmental remediation material for treating arsenic-containing wastewater due to its high specific surface area and good adsorption capacity for arsenic. Common methods for synthesizing schwertmannite include hydrogen peroxide oxidation method, dialysis method, biosynthesis method, etc. The hydrogen peroxide oxidation method is rapid, simple, and efficient, can be carried out at room temperature, and has low cost, but its specific surface area is relatively small; the dialysis method takes a long time, and the subsequent freeze-drying process is complex, and the obtained schwertmannite has a large particle size and good XRD signals; the biosynthesis method is considered a green and environmentally friendly method with wide material sources and environmental friendliness, but the process is relatively complex, the synthesis time is long, and some minerals may adhere to the reactor wall during the synthesis process, making it difficult to be applied on a large scale in practice. The common method for increasing the specific surface area of schwertmannite is surface modification method, such as acid washing, alkali washing or organic modification, to increase the surface activity of schwertmannite and thus improve its specific surface area.

[0003] Currently, common methods for increasing the specific surface area of schwertmannite usually rely on adding various chemical reagents. While these chemical reagents increase the specific surface area of the mineral, they also cause a certain degree of pollution and burden to the environment. Therefore, it is urgent to explore more sustainable alternative solutions. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing schwertmannite with an increased specific surface area, which improves the specific surface area of schwertmannite by optimizing the addition method of hydrogen peroxide solution, so that schwertmannite has higher adsorption performance in subsequent applications.

[0005] To achieve the above purpose, the present invention is implemented by adopting the following technical solutions:

[0006] The present invention provides a method for preparing schwertmannite with an increased specific surface area, the method comprising the following steps:

[0007] (1) Dissolve ferrous sulfate heptahydrate in distilled water to obtain a ferrous sulfate solution;

[0008] (2) Add hydrogen peroxide solution in an atomized form to the ferrous sulfate solution obtained in step (1), stir, filter, wash, and then vacuum dry to obtain schwertmannite.

[0009] Preferably, in step (1), in the ferrous sulfate solution, the concentration of ferrous sulfate heptahydrate is 0.06 - 0.08 mol / L.

[0010] Preferably, in step (2), the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide is (0.69 - 1.37):1.

[0011] Preferably, in step (2), the mass concentration of the hydrogen peroxide solution is 15% - 30%.

[0012] Preferably, in step (2), the rate of adding the hydrogen peroxide solution is 0.2 - 0.8 mL / min; the nozzle of the hydrogen peroxide solution atomizing pipe is placed at the bottom of the reaction vessel, or the nozzle of the hydrogen peroxide solution atomizing pipe is placed below the liquid level of the ferrous sulfate solution and close to the liquid level, so as to achieve full contact between the liquid mist and the solution, and make Fe 2+ uniformly oxidized.

[0013] Preferably, in step (2), the stirring time is 24 - 30 h.

[0014] Preferably, in step (2), the temperature of the vacuum drying is 45 - 60 °C, and the time is 6 - 12 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Based on the chemical synthesis of schwertmannite, no additional chemical reagents are added, saving resources and being environmentally friendly;

[0017] 2. The method process is simple and the operation is convenient. During the synthesis of schwertmannite, its specific surface area can be increased. Under the condition of the same addition rate of the hydrogen peroxide solution, the specific surface area of the schwertmannite prepared by the present invention is increased to 1.57 times that of the schwertmannite prepared by adding the hydrogen peroxide solution in droplets.

[0018] 3. In the present invention, the hydrogen peroxide solution is added to the reaction system in the form of atomization, replacing the traditional dropping method, thereby increasing the contact area between the hydrogen peroxide solution and ferrous sulfate heptahydrate, enhancing the uniformity and efficiency of the reaction, and avoiding the rapid hydrolysis of Fe 3+ to generate Fe(OH) 3 , improving the utilization rate of the hydrogen peroxide solution, reducing the amount of the hydrogen peroxide solution used, and saving costs.

[0019] In summary, the method of the present invention not only reduces the environmental impact of chemical reagents, but also reduces the production cost, reflecting the dual benefits of resource conservation and environmental protection. The present invention provides an environmentally friendly, efficient and sustainable schwertmannite treatment technology, providing new ideas for the development of related fields. Description of the Drawings

[0020] Figure 1 XRD patterns of schwertmannite prepared in Example 1 and Comparative Example 1 of the present invention;

[0021] Figure 2 Scanning electron micrograph of schwertmannite prepared in Example 1 of the present invention;

[0022] Figure 3 Scanning electron micrograph of schwertmannite prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0023] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Example 1

[0025] A method for preparing schwertmannite with an increased specific surface area, specifically including the following steps:

[0026] (1) Dissolve 0.06 mol of ferrous sulfate heptahydrate in 1 L of distilled water until it is completely dissolved to obtain a ferrous sulfate solution;

[0027] (2) Place the liquid mist nozzle of the hydrogen peroxide solution below the liquid surface of the ferrous sulfate solution near the liquid surface, and add the liquid mist of the hydrogen peroxide solution with a mass concentration of 30% to the solution at a rate of 0.2 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After adding the hydrogen peroxide solution, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0028] As Figure 1 in the XRD pattern of Example 1, obvious characteristic peaks of schwertmannite are present at 17.5°, 26.2°, 35.1°, 46.6°, 55.3°, and 61.3°, as Figure 2 is the scanning electron micrograph of the schwertmannite prepared in this example, showing a "sea urchin" shape with uniform size, about 1 micron.

[0029] Example 2

[0030] A method for preparing schwertmannite with an increased specific surface area, specifically including the following steps:

[0031] (1) Dissolve 0.07 mol of ferrous sulfate heptahydrate in 1 L of distilled water until it is completely dissolved to obtain a ferrous sulfate solution;

[0032] (2) Place the nozzle of the hydrogen peroxide solution atomizer below the liquid surface of the ferrous sulfate solution, close to the liquid surface. Add the atomized hydrogen peroxide solution with a mass concentration of 30% to the solution at a rate of 0.2 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After adding the hydrogen peroxide solution, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0033] Example 3

[0034] A method for preparing schwertmannite with an increased specific surface area, specifically including the following steps: (1) Dissolve 0.08 mol of ferrous sulfate heptahydrate in 1 L of distilled water to completely dissolve it, obtaining a ferrous sulfate solution;

[0035] (2) Place the nozzle of the hydrogen peroxide solution atomizer below the liquid surface of the ferrous sulfate solution, close to the liquid surface. Add the atomized hydrogen peroxide solution with a mass concentration of 30% to the solution at a rate of 0.2 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After adding the hydrogen peroxide solution, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0036] Example 4

[0037] A method for preparing schwertmannite with an increased specific surface area, specifically including the following steps:

[0038] (1) Dissolve 0.08 mol of ferrous sulfate heptahydrate in 1 L of distilled water to completely dissolve it, obtaining a ferrous sulfate solution;

[0039] (2) Place the nozzle of the hydrogen peroxide solution atomizer below the liquid surface of the ferrous sulfate solution, close to the liquid surface. Add the atomized hydrogen peroxide solution with a mass concentration of 30% to the solution at a rate of 0.8 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After adding the hydrogen peroxide solution, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0040] Example 5

[0041] A method for preparing schwertmannite with an increased specific surface area, specifically including the following steps:

[0042] (1) Dissolve 0.08 mol of ferrous sulfate heptahydrate in 1 L of distilled water until it is completely dissolved to obtain a ferrous sulfate solution;

[0043] (2) Place the nozzle of the hydrogen peroxide solution atomizer below the liquid level of the ferrous sulfate solution near the liquid surface, and add the hydrogen peroxide solution atomizer to the solution at a rate of 0.2 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 1.37:1. After adding the hydrogen peroxide solution with a mass concentration of 30%, stir and react for 24 hours until the reaction ends. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0044] Example 6

[0045] A preparation method of schwertmannite with an increased specific surface area, specifically including the following steps:

[0046] (1) Dissolve 0.08 mol of ferrous sulfate heptahydrate in 1 L of distilled water until it is completely dissolved to obtain a ferrous sulfate solution;

[0047] (2) Place the nozzle of the hydrogen peroxide solution atomizer at the bottom of the reaction vessel, and add the hydrogen peroxide solution atomizer to the solution at a rate of 0.2 mL / min according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 1.37:1. After adding the hydrogen peroxide solution with a mass concentration of 30%, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0048] Comparative Example 1

[0049] A preparation method of schwertmannite, specifically including the following steps:

[0050] Dissolve 0.06 mol of ferrous sulfate heptahydrate in 1 L of distilled water. After it is completely dissolved, add hydrogen peroxide solution droplets to the solution at a rate of 12 ml / h according to the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After adding the hydrogen peroxide solution with a mass concentration of 30%, stir and react for 24 hours until the reaction is complete. Subsequently, separate the solid by suction filtration, wash the obtained solid three times with distilled water to ensure the removal of unreacted substances, and finally place the washed solid in a vacuum drying oven and dry it at 60 °C for 12 hours to obtain schwertmannite.

[0051] As Figure 1The XRD spectrum of Comparative Example 1 has obvious characteristic peaks of Schmidtite at 17.5°, 26.2°, 35.1°, 46.6°, 55.3°, and 61.3°, such as Figure 3 This is a scanning electron microscope photograph of the Schreiber mineral prepared in Comparative Example 1, which is in the shape of a "sea urchin". Compared with Example 1, the sizes of the Schreiber mineral are uneven, and the sphericity of the Schreiber mineral particles is poor, and some of them have flat surfaces, indicating that the reaction is more uneven than that in Example 1.

[0052] Comparative Example 2

[0053] A method for preparing Schmidt mineral comprises the following steps:

[0054] 0.08 mol of ferrous sulfate heptahydrate was dissolved in 1 L of distilled water. After it was completely dissolved, a hydrogen peroxide solution with a mass concentration of 30% was added dropwise at a rate of 12 mL / h according to a molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide of 0.69:1. After the addition of the hydrogen peroxide solution, the reaction was stirred for 24 hours until the reaction was complete. Subsequently, the solid was separated by suction filtration, and the obtained solid was washed three times with distilled water to ensure that unreacted substances were removed. Finally, the washed solid was placed in a vacuum drying oven and dried at 60° C. for 12 hours to obtain Schmidt mineral.

[0055] Table 1 Conditions of Examples 1-6 and Comparative Examples 1-2 and specific surface areas of corresponding products

[0056]

[0057]

[0058] As shown in Table 1, by comparing Examples 1, 2, and 3, with the increase in the concentration of ferrous sulfate heptahydrate, the yield of the Schmidtite increases, but the specific surface area decreases. This is because after the concentration of ferrous sulfate heptahydrate increases, the concentration of ferrous ions per unit volume of the solution increases, the reaction of hydrogen peroxide molecules with ferrous ions accelerates, and the oxidation rate of ferrous ions is increased, resulting in a decrease in the specific surface area of ​​the Schmidtite. By comparing Example 1 with Comparative Example 1, it can be obtained that after the addition method of the hydrogen peroxide solution is changed from droplets to liquid mist, the specific surface area of ​​the Schmidtite increases from 16.341 m 2 / g increases to 25.727m 2 / g, increased to 1.57 times, and the size of the prepared Schmidt mineral was uniform, and the particle sphericity was complete; Comparing Example 5 with Example 6, on the basis of adding hydrogen peroxide solution in the form of liquid mist, by changing the placement position of the liquid mist nozzle, not only the specific surface area of ​​the Schmidt mineral was increased, but also the yield of the Schmidt mineral was improved. This is because the addition of hydrogen peroxide solution liquid mist at the bottom of the container can be accompanied by stirring to make hydrogen peroxide and ferrous ions fully contact, the reaction is more uniform, and the specific surface area of ​​the Schmidt mineral is increased to 29.631m 2 / g, and the addition amount of the hydrogen peroxide solution will also be reduced, saving production costs; comparing Example 3 and Example 4, the specific surface area of schwertmannite can be increased by reducing the addition rate of the hydrogen peroxide solution.

[0059] The above embodiments are only the preferred embodiments of the present invention and are not limitations on the implementation manners. The protection scope of the present invention should be subject to the scope defined by the claims. Other different forms of changes or modifications can be made on the basis of the above description. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a Schmidtite with an increased specific surface area, characterized in that: The method comprises the following steps: (1) dissolving ferrous sulfate heptahydrate in distilled water to obtain a ferrous sulfate solution; (2) adding a hydrogen peroxide solution in an atomized form to the ferrous sulfate solution obtained in step (1), stirring, filtering, washing, and then vacuum drying to obtain Schroeder mineral.

2. The preparation method according to claim 1, characterized in that: In step (1), the concentration of ferrous sulfate heptahydrate in the ferrous sulfate solution is 0.06-0.08 mol / L.

3. The preparation method according to claim 1, characterized in that: In step (2), the molar ratio of ferrous sulfate heptahydrate to hydrogen peroxide is (0.69-1.37):

1.

4. The preparation method according to claim 1, characterized in that: In step (2), the mass concentration of the hydrogen peroxide solution is 15%-30%.

5. The preparation method according to claim 1, characterized in that: In step (2), the rate of adding hydrogen peroxide solution is 0.2-0.8 mL / min; the hydrogen peroxide solution mist pipe port is placed at the bottom of the reaction container or the hydrogen peroxide solution mist pipe port is placed below the liquid surface of the ferrous sulfate solution and close to the liquid surface.

6. The preparation method according to claim 1, characterized in that: In step (2), the stirring time is 24-30 hours.

7. The preparation method according to claim 1, characterized in that: In step (2), the vacuum drying is carried out at a temperature of 45-60° C. and for a time of 6-12 hours.

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