A coordination unsaturated alumina material, its preparation method and application

Abstract

The application provides a kind of coordination unsaturated alumina material and its preparation method and application, which comprises the following steps: adding glacial acetic acid in the solution containing aluminum salt, then adding urea, carrying out hydrothermal reaction to obtain solid product;The solid product is heat treated at 200-600 DEG C to obtain the coordination unsaturated alumina material.The coordination unsaturated alumina material prepared by the application can selectively adsorb fluorine by chemical coordination, and its porous structure can provide a large number of adsorption sites, so as to realize high capacity adsorption of fluorine.

Description

Technical Field

[0001] This invention relates to the field of fluoride-containing wastewater treatment, and in particular to a coordination unsaturated alumina material, its preparation method, and its application. Background Technology

[0002] Fluorinated chemical raw materials are widely used in industries such as electronics, photovoltaics, high-speed rail, and chemicals. With the widespread use of these raw materials, a large amount of fluoride-containing wastewater is generated. When this wastewater is discharged into natural water bodies, it leads to increased fluoride concentrations, affecting water quality. High concentrations of fluoride can also inhibit the growth of aquatic organisms and disrupt the balance of aquatic ecosystems. Therefore, the removal of fluoride from wastewater is a significant environmental issue currently facing us.

[0003] Precipitation is a common method for defluoridation of wastewater. One type of precipitation method can recover fluorite or cryolite from wastewater and is widely used to treat high-concentration fluoride wastewater, but it is not suitable for low-concentration fluoride wastewater. Another precipitation method involves adding aluminum salts to the wastewater to achieve deep defluoridation through coordination and electrostatic interaction. However, this method may be a "pseudo" defluoridation method, as exchangeable and non-exchangeable fluoride are difficult to remove. In addition, the defluoridation rate of this method is not high. Therefore, the development of deep defluoridation technology is urgently needed.

[0004] Compared with precipitation, adsorption has the advantages of simple operation, wide applicability and stable operation, and has great application prospects in deep defluorination. Currently, commonly used adsorbents include activated carbon, alumina and natural materials (zeolite, kaolin, etc.). Among them, activated alumina adsorption is the most mature method for deep treatment of fluoride-containing wastewater, but it still has problems such as poor selectivity for fluoride adsorption and low adsorption capacity. Summary of the Invention

[0005] The main objective of this invention is to provide a coordination-unsaturated alumina adsorbent material, which aims to solve the technical problems of poor selectivity and low adsorption capacity of existing adsorbent materials.

[0006] In a first aspect, the present invention provides a method for preparing a coordination-unsaturated alumina material, comprising the following steps:

[0007] In a solution containing aluminum salt, glacial acetic acid is added, followed by urea, and a hydrothermal reaction is carried out to obtain a solid product.

[0008] The solid product is heat-treated at 200~600℃ to obtain the coordinated unsaturated alumina material.

[0009] Furthermore, the molar ratio of the aluminum salt to the glacial acetic acid is 1:0.5~5.

[0010] Furthermore, the molar ratio of the aluminum salt to urea is 1:0.1~2.

[0011] Furthermore, the hydrothermal reaction satisfies the following conditions: the reaction temperature is 80℃~240℃, and the reaction time is 2h~8h.

[0012] Furthermore, the heat treatment includes the following process: heating to 200-600°C at a heating rate of 1-5°C / min, and holding at that temperature for 30-180min.

[0013] Furthermore, in the solution containing aluminum salt, the aluminum salt includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride; the solvent is an organic solvent.

[0014] Furthermore, the organic solvent is isopropanol or ethylene glycol.

[0015] In a second aspect, the present invention provides a coordination-unsaturated alumina material, which is prepared by the preparation method described in the first aspect.

[0016] Thirdly, the present invention provides a method for removing fluoride, comprising the following steps: adding the coordination unsaturated alumina material of the second aspect to fluoride-containing wastewater and performing stirring treatment to remove fluoride ions from the fluoride-containing wastewater.

[0017] Furthermore, the fluoride ion concentration in the fluoride-containing wastewater is n, where n satisfies: 0 mg / L <n≤100 mg / L。

[0018] The preparation method provided by this invention can remove coordination-unsaturated components during the preparation process. , , At least one of the following can be introduced into an alumina material, and functional groups such as hydroxyl and carbonyl groups can be introduced on its surface to finally obtain a coordination unsaturated alumina material with good selectivity, high adsorption capacity and porous morphology.

[0019] The coordination-unsaturated alumina material provided by this invention can selectively adsorb fluorine through chemical coordination, and its porous structure can provide a large number of adsorption sites, thereby achieving high-capacity fluorine adsorption. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0021] Figure 1 These are microscopic characterization images of the alumina materials in Example 1 and Comparative Example 1.

[0022] In the figure, a is a microscopic characterization diagram of the alumina material in Example 1, and b is a microscopic characterization diagram of the alumina material from Example 1. Figure 1 Microscopic characterization diagram of the alumina material in Comparative Example 1;

[0023] Figure 2 The infrared spectra of the alumina materials in Example 1 and Comparative Example 1 are shown below.

[0024] Figure 3 A bar chart comparing the defluorination effects of the alumina materials in Example 1 and Comparative Example 1 in Test Example 1;

[0025] Figure 4 This is a bar chart comparing the defluorination effect of the alumina material from Example 1 in Test Example 2 on solutions with different fluoride concentrations. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] In this application, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0029] In this application, the terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0030] In this application, references to "an embodiment," "an example," or "an example" mean that a specific feature, structure, or characteristic described in connection with that embodiment, example, or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination.

[0031] To address the issues of poor selectivity and low adsorption capacity in the adsorption of fluorine by activated alumina, researchers have improved the fluorine removal capacity of activated alumina to some extent by introducing other substances (lanthanum, graphene, hydroxyapatite, etc.). However, the complex preparation process of surface modification and the high cost of materials such as lanthanum used in the modification process have increased the cost of fluorine removal from alumina to some extent.

[0032] Therefore, it is necessary to provide a high-efficiency, low-cost alumina adsorbent material to solve or at least alleviate the problems of poor fluoride removal selectivity and low capacity of existing alumina materials.

[0033] In a first aspect, the present invention provides a method for preparing a coordination-unsaturated alumina material, comprising the following steps:

[0034] In a solution containing aluminum salt, glacial acetic acid is added, followed by urea, and a hydrothermal reaction is carried out to obtain a solid product.

[0035] The solid product is heat-treated at 200~600℃ to obtain the coordinated unsaturated alumina material.

[0036] In this invention, aluminum salts and glacial acetic acid react to produce aluminum acetate. Adding urea yields partial aluminum urea and alumina particles. The aluminum acetate decomposes under heat treatment, generating alumina during the process. The heat treatment temperature affects the degree of decomposition, thus retaining some functional groups (such as hydroxyl and carboxyl groups) on the material surface. Simultaneously, the decomposition of aluminum urea and aluminum acetate produces gases such as carbon dioxide and ammonia, which contributes to the formation of a porous structure. Furthermore, a suitable heat treatment temperature also promotes… , , The formation of unsaturated aluminum species.

[0037] For example, the temperature of the heat treatment described above is any value or a range of any two of the following: 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C.

[0038] The present invention does not specifically limit the aluminum salts mentioned above, and for example, they can be aluminum chloride, aluminum nitrate, aluminum sulfate, etc.

[0039] In an optional embodiment, the molar ratio of the aluminum salt to the glacial acetic acid is 1:0.5~5.

[0040] For example, the molar ratio of the aluminum salt to the glacial acetic acid is 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0041] In an optional embodiment, the molar ratio of the aluminum salt to urea is 1:0.1~2.

[0042] Urea decomposes under hydrothermal conditions to produce ammonia, which gradually increases the pH value of the system. Therefore, the molar ratio of aluminum salt to urea determines the rate of pH change and the final pH level. This affects the hydrolysis of aluminum and the formation of alumina, thereby affecting the specific surface area and pore structure of alumina. The ratio described above may lead to a higher specific surface area and a more developed pore structure, which is beneficial for the adsorption of fluorine.

[0043] Coordinated unsaturated alumina materials typically require a high specific surface area. A suitable hydrothermal temperature is crucial to ensure the grain size, thereby guaranteeing the specific surface area. Therefore, controlling the hydrothermal reaction to maintain an appropriate grain size is key. Furthermore, the hydrothermal temperature also affects the pore structure of the coordinated unsaturated alumina material, including pore size and pore volume. Appropriate temperatures can promote the formation of pore structures, which is beneficial for its application in adsorption. Therefore, in an optional embodiment, the hydrothermal reaction satisfies the following conditions: the reaction temperature is 80℃~240℃, and the reaction time is 2h~8h.

[0044] For example, the temperature of the hydrothermal reaction is any value or a range of any two of the following: 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, etc., and the reaction time of the hydrothermal reaction is any value or a range of any two of the following: 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0045] The parameters of heat treatment affect the specific surface area of ​​alumina. Generally speaking, heat treatment with a high heating rate will lead to rapid grain growth and a decrease in specific surface area. Moreover, the heating program and holding time of heat treatment will affect the pore size, pore volume and pore distribution of alumina material. Therefore, selecting appropriate heat treatment parameters to maintain a high specific surface area is relatively important for adsorption applications. In an optional embodiment, the process includes the following steps: heating to 200-600°C at a heating rate of 1-5°C / min and holding for 30-180min.

[0046] The heat treatment process described above can regulate parameters such as the specific surface area, pore size, pore volume, and pore distribution of alumina materials, thereby further improving the adsorption properties of alumina materials.

[0047] In an optional embodiment, the aluminum salt in the solution includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride; and the solvent is an organic solvent.

[0048] In an alternative embodiment, the organic solvent is isopropanol or ethylene glycol.

[0049] In a second aspect, the present invention provides a coordination-unsaturated alumina material, which is prepared by the preparation method described in the first aspect.

[0050] Thirdly, the present invention provides a method for removing fluoride, comprising the following steps: adding the coordination unsaturated alumina material of the second aspect to fluoride-containing wastewater and performing stirring treatment to remove fluoride ions from the fluoride-containing wastewater.

[0051] In an optional embodiment, the fluoride ion concentration in the fluoride-containing wastewater is n, where n satisfies: 0 mg / L <n≤100mg / L。

[0052] In some embodiments, the fluoride ion concentration in the fluoride-containing wastewater is n, where n satisfies: 1.5 mg / L <n≤100 mg / L。

[0053] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Unless otherwise specified, all reagents involved in the embodiments of this invention are commercially available products and can be purchased through commercial channels.

[0055] Example 1

[0056] This example provides a coordination-unsaturated alumina material, the preparation method of which includes the following steps:

[0057] Dissolve 50 mmol of aluminum sulfate in 50 mL of ethylene glycol, add 5 mL (87 mmol) of glacial acetic acid dropwise while stirring, then add 20 mmol of urea and stir well. Transfer the solution into a polytetrafluoroethylene liner and hydrothermally react at 180 °C for 4 h. After cooling, wash with ethanol and ultrapure water 3 to 5 times respectively to obtain a white powder.

[0058] The white powder was placed in a quartz boat in a tube furnace and heated to 400°C at a heating rate of 2°C / min, held for 60 min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain sample 1.

[0059] Microscopic characterization of sample 1 as follows Figure 1 As shown in Figure a, by Figure 1 It can be seen that the surface of sample 1 has a porous structure;

[0060] The infrared spectrum of sample 1 is as follows Figure 2 As shown, by Figure 2 It can be seen that the surface of sample 1 contains hydroxyl groups, carboxyl groups and unsaturated aluminum.

[0061] Example 2

[0062] This example provides a coordination-unsaturated alumina material, the preparation method of which includes the following steps:

[0063] Dissolve 50 mmol of aluminum sulfate in 50 mL of ethylene glycol, add 5 mL (87 mmol) of glacial acetic acid dropwise while stirring, then add 5 mmol of urea and stir well. Transfer the solution into a polytetrafluoroethylene liner and hydrothermally react at 180 °C for 4 h. After cooling, wash with ethanol and ultrapure water 3 to 5 times respectively to obtain a white powder.

[0064] The white powder was placed in a quartz boat in a tube furnace and heated to 400°C at a heating rate of 2°C / min, held for 60 min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain sample 1-1.

[0065] Example 3

[0066] This example provides a coordination-unsaturated alumina material, the preparation method of which includes the following steps:

[0067] Dissolve 50 mmol of aluminum sulfate in 50 mL of ethylene glycol, add 5 mL (87 mmol) of glacial acetic acid dropwise while stirring, then add 100 mmol of urea and stir well. Transfer the solution into a polytetrafluoroethylene liner and hydrothermally react at 180 °C for 4 h. After cooling, wash with ethanol and ultrapure water 3 to 5 times respectively to obtain a white powder.

[0068] The white powder was placed in a quartz boat in a tube furnace and heated to 400°C at a heating rate of 2°C / min, held for 60 min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain samples 1-2.

[0069] Example 4

[0070] This example provides a coordination-unsaturated alumina material, the preparation method of which includes the following steps:

[0071] Dissolve 50 mmol of aluminum sulfate in 50 mL of ethylene glycol, add 5 mL (87 mmol) of glacial acetic acid dropwise while stirring, then add 20 mmol of urea and stir until homogeneous. Transfer the solution into a polytetrafluoroethylene liner and hydrothermally react at 100 °C for 5 h. After cooling, wash with ethanol and ultrapure water 3 to 5 times respectively to obtain a white powder.

[0072] The white powder was placed in a quartz boat in a tube furnace and heated to 400°C at a heating rate of 2°C / min, held for 60 min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain samples 1-3.

[0073] Example 5

[0074] This example provides a coordination-unsaturated alumina material, the preparation method of which includes the following steps:

[0075] Dissolve 50 mmol of aluminum sulfate in 50 mL of ethylene glycol, add 5 mL (87 mmol) of glacial acetic acid dropwise while stirring, then add 20 mmol of urea and stir well. Transfer the solution into a polytetrafluoroethylene liner and hydrothermally react at 180 °C for 4 h. After cooling, wash with ethanol and ultrapure water 3 to 5 times respectively to obtain a white powder.

[0076] The white powder was placed in a quartz boat in a tube furnace and heated to 250°C at a heating rate of 2°C / min, held for 100 min, and then cooled to room temperature at a cooling rate of 2°C / min to obtain samples 1-4.

[0077] Comparative Example 1

[0078] Commercially available nano-alumina particles, purchased directly, were used as a comparison and designated as Sample 2.

[0079] Microscopic characterization of sample 2 as follows Figure 1 As shown in b, by Figure 1 It can be seen that there is no porous structure on the surface of sample 2;

[0080] The infrared spectrum of sample 2 is as follows Figure 2 As shown, by Figure 2It can be seen that the surface of sample 1 does not contain hydroxyl groups, carboxyl groups, or unsaturated aluminum.

[0081] Test Example 1

[0082] The removal rate of fluorine by the coordinated unsaturated alumina materials of the above examples and comparative examples was tested. The test method includes the following steps:

[0083] Simulated fluoride-containing wastewater was prepared using sodium fluoride and sodium sulfate, with a fluoride ion concentration of 20 mg / L and a sulfate ion concentration of 100 mg / L. Multiple 150 mL beakers were used, each containing 100 mL of the fluoride-containing wastewater, followed by the addition of different coordinated unsaturated alumina materials at a concentration of 0.5 g / L. The mixture was reacted at a stirring rate of 300 rpm for 30 min. Samples were filtered through a 0.45 μm filter, and the fluoride ion concentration in the solution was measured using a fluoride ion electrode. The experimental results for samples 1 and 2 are shown below. Figure 3 As shown, by Figure 3 It can be seen that after 30 min of reaction, the removal rates of fluorine for sample 1 and sample 2 were 89.6% and 33.3%, respectively.

[0084] Furthermore, the fluorine removal rate of sample 1-1 was 80.2%, that of sample 1-2 was 73.4%, that of sample 1-3 was 85.4%, and that of sample 1-4 was 82.6%.

[0085] Test Example 2

[0086] The selective removal of fluorine by the coordinated unsaturated alumina materials of the above embodiments and comparative examples was tested. The test method includes the following steps:

[0087] 1) Testing for chloride ion interference: Sodium chloride, sodium fluoride and water were mixed to prepare a solution containing 100 mg / L chloride ions and 20 mg / L fluoride ions. Multiple 150 mL beakers were used, and equal amounts of the above mixture were added to each beaker. Then, different samples were added to each beaker at a concentration of 0.5 g / L. The mixture was stirred at 300 rpm for 30 min. The samples were filtered through a 0.45 μm filter and the fluoride ion concentration in the solution was tested using a fluoride ion electrode.

[0088] Test results: The fluoride removal rate of sample 1 reached 92.1%; the fluoride removal rate of sample 2 was 40.2%.

[0089] 2) Testing for interference from nitrate: Sodium nitrate, sodium fluoride, and water were mixed to prepare a solution containing 100 mg / L of nitrate ions and 20 mg / L of fluoride ions. Multiple 150 mL beakers were used, and equal volumes of the above mixture were added to each beaker. Then, different samples were added to each beaker at a concentration of 0.5 g / L. The mixture was stirred at 300 rpm for 30 min. The samples were filtered through a 0.45 μm filter and the concentration of fluoride ions in the solution was measured using a fluoride ion electrode.

[0090] Test results: The fluoride removal rate of sample 1 reached 87.5%; the fluoride removal rate of sample 2 was 36.4%.

[0091] 3) Testing for interference from sulfate, nitrate, and copper ions: Sodium sulfate, sodium nitrate, sodium fluoride, copper sulfate pentahydrate, and water were mixed to prepare a solution containing 100 mg / L sulfate ions, 125 mg / L nitrate ions, 10 mg / L copper ions, and 20 mg / L fluoride ions. Multiple 150 mL beakers were used, and equal volumes of the above mixture were added to each. Different samples were then added at a concentration of 0.5 g / L. The mixture was stirred at 300 rpm for 30 min. Samples were filtered using a 0.45 μm filter, and the fluoride ion concentration in the solution was measured using a fluoride ion electrode.

[0092] Test results: The fluoride removal rate of sample 1 reached 88.5%; the fluoride removal rate of sample 2 was 21.64%.

[0093] Test Example 3

[0094] The method for testing the fluoride removal rate of the coordination unsaturated alumina material in Example 1 above for solutions with different fluoride contents includes the following steps:

[0095] Simulated fluoride-containing wastewater was prepared using sodium fluoride and sodium sulfate, with fluoride ion concentration gradients of 10, 20, and 30 mg / L, and sulfate concentration of 100 mg / L for all samples. Three 150 mL beakers were used, each containing 100 mL of the fluoride-containing wastewater, followed by the addition of 0.5 g / L of the sample solution. The mixture was reacted at 300 rpm for 30 min. Samples were filtered through a 0.45 μm filter, and the fluoride ion concentration in the solution was measured using a fluoride ion electrode.

[0096] Experimental results are as follows Figure 4 As shown, after 30 minutes of reaction, the fluoride ion concentrations in the three beakers were 10, 20, and 30 mg / L, respectively. Calculations showed that the fluoride removal rates in the wastewater were 89.6%, 89.8%, and 86.4%, respectively.

[0097] Summary: Based on the above tests, Figure 1 and Figure 2It is known that traditional alumina is a nanoparticle, which does not have a porous structure and has few adsorption sites. Its adsorption capacity for fluoride ions is much lower than that of the coordinated unsaturated alumina material of the present invention. Furthermore, the selectivity of traditional nano-alumina particles in adsorbing fluoride ions is also poor.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a coordination-unsaturated alumina material, characterized in that, Includes the following steps: In a solution containing aluminum salt, glacial acetic acid is added dropwise under stirring to produce aluminum acetate. Urea is then added, and a hydrothermal reaction is carried out to obtain a solid product. The molar ratio of aluminum salt to glacial acetic acid is 1:0.5~5, and the molar ratio of aluminum salt to urea is 1:0.1~2. The solid product is heat-treated at 200~600℃ to obtain the coordinated unsaturated alumina material; the heat treatment includes the following process: heating to 200~600℃ at a heating rate of 1~5℃ / min and holding at that temperature for 30~180min. The hydrothermal reaction satisfies the following conditions: the reaction temperature is 80℃~240℃, and the reaction time is 2h~8h; In the solution containing aluminum salt, the solvent is an organic solvent; The organic solvent is isopropanol or ethylene glycol.

2. The preparation method according to claim 1, characterized in that, The aluminum salt in the solution includes at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride.

3. A coordination-unsaturated alumina material, characterized in that, It is prepared by the preparation method described in claim 1 or 2.

4. A method for defluorination, characterized in that, The process includes the following steps: adding the coordinated unsaturated alumina material of claim 3 to fluoride-containing wastewater and stirring it to remove fluoride ions from the fluoride-containing wastewater.

5. The method according to claim 4, characterized in that, The fluoride ion concentration in the fluoride-containing wastewater is n, where n satisfies: 0 mg / L <n≤100 mg / L。

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