Boehmite with high adsorption performance and preparation method thereof

Abstract

The invention specifically discloses boehmite with high adsorption performance and a preparation method thereof, and the preparation method comprises the following steps: adding a second aluminum salt into a prepared first aluminum salt solution, then adding a precipitant, transferring into a reaction kettle, and carrying out a hydrothermal reaction to obtain boehmite. The boehmite obtained by the invention has the advantages of small particle size, large specific surface area, good adsorbability, low production cost and the like, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic material preparation, and in particular to boehmite with high adsorption performance and a preparation method thereof. Background Art

[0002] In recent years, the printing and dyeing industry has developed rapidly, generating a large amount of wastewater. Congo red is a benzidine-type anionic dye widely used in papermaking, textile, leather, printing and dyeing industries; however, Congo red is a substance harmful to the environment and human body, and needs to be removed before industrial wastewater is discharged. The treatment methods for dye wastewater at home and abroad mainly include physical, biological and chemical methods, including adsorption, extraction, membrane separation, oxidation, coagulation and electrochemical methods. The extraction method is only suitable for treating a small amount of wastewater. It is not suitable for dye wastewater with complex components. It has high requirements for the extractant used and high cost. The membrane separation method requires frequent replacement of the membrane and has high cleaning costs. The oxidation method is unstable in operation, has poor applicability, and is greatly affected by external factors.

[0003] The adsorption method has the advantages of no or less use of organic solvents, easy operation, safety, simple equipment, small pH change in the production process, and low cost. The enrichment of pollutants on the surface of the adsorbent material can effectively reduce the concentration of pollutants in the water, or even completely remove them. It has good treatment effect, low cost, easy operation, and low energy consumption, so it is widely used to remove low-concentration pollutants. However, in industrial applications of wastewater treatment, adsorbents are usually limited by their low adsorption capacity and high preparation cost. Therefore, there is an urgent need to find a material with high adsorption capacity as an adsorbent. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a boehmite with high adsorption performance and a preparation method thereof. The boehmite is prepared by the method provided by the present invention, and the prepared boehmite has small particle size, good dispersibility and good adsorption.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A method for preparing boehmite with high adsorption performance comprises the following steps: adding a second aluminum salt to a prepared first aluminum salt solution, then adding a precipitant, and transferring the solution to a reactor for hydrothermal reaction to obtain the boehmite.

[0007] Among many methods, the hydrothermal method shows advantages in regulating the micromorphology and micro-nano size of nano-boehmite powder. It is simple to operate and environmentally friendly, and is hailed as the most promising method on the road to green synthesis.

[0008] Furthermore, the anions in the first aluminum salt solution are chloride ions or nitrate ions.

[0009] Furthermore, the anion in the second aluminum salt is a sulfate ion.

[0010] Furthermore, the molar ratio of the chloride ion or nitrate ion to the sulfate ion is 18:1-3:1.

[0011] Sulfate ions were introduced into the hydrothermal process of aluminum chloride / aluminum nitrate-urea to form a competitive system of sulfate ions and chloride ions, and sulfate ions and nitrate ions. By utilizing anion competition and changing the different ratios between ions, boehmite was synthesized from layered assembly to hollow sphere morphology.

[0012] Furthermore, the precipitant is urea.

[0013] Urea is widely used for uniform precipitation of metal ions and synthesis of oxides or dioxides. Due to rapid nucleation and supersaturation, the uniformity of particle size is regulated by pre-reaction. In the subsequent reaction process, urea can be hydrolyzed stably and continuously.

[0014] Furthermore, the hydrothermal reaction conditions are: heating to a pre-reaction temperature, introducing gas, and then heating to a reaction temperature to carry out the reaction.

[0015] Furthermore, the pre-reaction temperature is 100-160°C.

[0016] Furthermore, the reaction temperature is 180-250°C.

[0017] Through two high-temperature treatments, the crystal integrity and uniformity of the particle size distribution of the finally prepared boehmite particles can be improved. Compared with a single temperature increase treatment, the agglomeration of the crystal nuclei generated in the first pretreatment slurry can be avoided, thereby avoiding the increase in the particle size of the finally prepared boehmite particles; at the same time, by controlling the temperature of the second high-temperature treatment to be higher than the temperature of the first high-temperature treatment, the slow period of crystal nucleus growth can be avoided, and the crystal nuclei generated in the first pretreatment slurry can grow stably, and it is helpful to improve the reaction selectivity of the boehmite, thereby obtaining boehmite with high crystallinity, small particle size, good dispersibility, narrow particle size distribution, uniform morphology and high crystallinity.

[0018] Furthermore, the gas is a mixed gas.

[0019] Furthermore, the mixed gas is obtained by mixing at least one of oxygen, nitrogen and inert gas with carbon dioxide gas.

[0020] Furthermore, in the mixed gas, the volume proportion of the carbon dioxide gas is 20%-90%.

[0021] When the volume proportion of carbon dioxide in the mixed gas is too high, not only will the utilization rate of carbon dioxide decrease, but the excessively high concentration of carbon dioxide will cause the pH value of the local area around the bubble to drop to below 9 briefly at the moment of being blown into the reaction system. At this time, amorphous aluminum hydroxide will be generated around the bubble, which is not conducive to the growth of boehmite in the subsequent reaction system. When the volume proportion of carbon dioxide in the mixed gas is too low, the number of crystal nuclei generated in the reaction system is small, and the crystal size is easy to become larger, which will cause the particle size of the subsequently generated boehmite to become larger, which is not conducive to obtaining boehmite with small particle size, narrow particle size distribution and uniform morphology.

[0022] By controlling the volume concentration of carbon dioxide gas in the mixed gas, the particle size and morphology uniformity of pseudo-boehmite and gibbsite in the pretreatment reaction solution can be regulated, which is helpful for subsequently obtaining boehmite with small particle size and uniform particle size distribution.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Boehmite has the advantages of excellent physical and chemical properties, non-toxicity, and low raw material price. Hierarchical boehmite has unique chemical properties and pore structure, and has broad prospects in the fields of adsorbent, catalyst carrier, composite material, etc.

[0025] 2. By controlling the type and concentration of anions in the reaction raw materials, the morphology and structure of boehmite growth are regulated to achieve a hollow structure with the largest specific surface area and the strongest adsorption capacity.

[0026] 3. By controlling the volume concentration of carbon dioxide gas in the mixed gas, the particle size and morphology uniformity in the pretreatment reaction liquid can be regulated, which is helpful for obtaining boehmite with small particle size and uniform particle size distribution in the subsequent process.

[0027] 4. Through two temperature-raising reactions, the reaction product is adjusted to a specific particle size distribution range, so that the boehmite finally prepared has the advantages of good dispersibility and good adsorption. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not 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 are within the scope of protection of the present invention.

[0029] Reagent Description

[0030] Ethanol, aluminum chloride, aluminum nitrate, aluminum sulfate, and urea were analytically pure and were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0031] Example 1

[0032] Ethanol and water are mixed in a volume ratio of 2:1 to form a solvent. Measure 1L of solvent, add 0.18mol of aluminum chloride, stir evenly, add 0.1mol of aluminum sulfate, stir evenly, add 2mol of urea, add the prepared solution to an autoclave with a polytetrafluoroethylene liner, the filling degree is 70%, stir at a speed of 600r / min and heat to 120°C, at which time the pressure in the reactor is 0.22MPa, keep warm at this temperature for 2h, blow into it a mixed gas of carbon dioxide and nitrogen with a volume ratio of 60% of carbon dioxide, control the flow rate of the mixed gas to 6L / min, until the pH value of the reaction system is 10, stop passing the mixed gas. Continue to heat to 200°C, keep warm at this temperature for 3h, after the reaction is completed, filter the obtained slurry, wash the collected filter cake with pure water until the pH value is close to neutral, and dry the filter cake at a temperature of 120°C for 5h to obtain the boehmite finished product.

[0033] Example 2

[0034] The difference between this embodiment and embodiment 1 is that the amount of aluminum sulfate used is 0.2 mol.

[0035] The other parts are exactly the same as those in Example 1.

[0036] Example 3

[0037] The difference between this embodiment and embodiment 1 is that the amount of aluminum sulfate used is 0.3 mol.

[0038] The other parts are exactly the same as those in Example 1.

[0039] Example 4

[0040] The difference between this embodiment and embodiment 1 is that the amount of aluminum sulfate used is 0.4 mol.

[0041] The other parts are exactly the same as those in Example 1.

[0042] Example 5

[0043] The difference between this embodiment and embodiment 1 is that the amount of aluminum sulfate used is 0.5 mol.

[0044] The other parts are exactly the same as those in Example 1.

[0045] Example 6

[0046] The difference between this embodiment and embodiment 1 is that the amount of aluminum sulfate used is 0.6 mol.

[0047] The other parts are exactly the same as those in Example 1.

[0048] Example 7

[0049] The difference between this embodiment and embodiment 1 is that the first aluminum salt is aluminum nitrate.

[0050] The other parts are exactly the same as those in Example 1.

[0051] Example 8

[0052] The difference between this embodiment and embodiment 2 is that the first aluminum salt is aluminum nitrate.

[0053] The other parts are exactly the same as those in Example 2.

[0054] Example 9

[0055] The difference between this embodiment and embodiment 3 is that the first aluminum salt is aluminum nitrate.

[0056] The other parts are exactly the same as those in Example 3.

[0057] Example 10

[0058] The difference between this embodiment and embodiment 4 is that the first aluminum salt is aluminum nitrate.

[0059] The other parts are exactly the same as those in Example 4.

[0060] Embodiment 11

[0061] The difference between this embodiment and embodiment 5 is that the first aluminum salt is aluminum nitrate.

[0062] The other parts are exactly the same as those in Example 5.

[0063] Example 12

[0064] The difference between this embodiment and embodiment 6 is that the first aluminum salt is aluminum nitrate.

[0065] The other parts are exactly the same as those in Example 6.

[0066] Embodiment 13

[0067] The difference between this embodiment and embodiment 1 is that the carbon dioxide content in the mixed gas is 20%.

[0068] The other parts are exactly the same as those in Example 1.

[0069] Embodiment 14

[0070] The difference between this embodiment and embodiment 1 is that the carbon dioxide accounts for 90% of the mixed gas.

[0071] The other parts are exactly the same as those in Example 1.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that the carbon dioxide accounts for 100% in the mixed gas.

[0074] The other parts are exactly the same as those in Example 1.

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 1 is that the proportion of carbon dioxide in the mixed gas is 0%.

[0077] The other parts are exactly the same as those in Example 1.

[0078] Tests and Results

[0079] The prepared boehmite was dispersed in 200 mL of 50 mg·L -1 After sealing with plastic wrap, start stirring (stirring speed 400r·min -1 , 25°C), sampled after 2 hours, centrifuged and the supernatant was taken to measure its absorbance, and then the solution was poured back. The adsorption amount was calculated, and the results are shown in Table 1.

[0080] Table 1

[0081] project <![CDATA[Adsorption capacity (mg·g -1 )]]> Example 1 332 Example 2 453 Example 3 564 Example 4 613 Example 5 640 Example 6 645 Example 7 352 Example 8 403 Example 9 450 Example 10 593 Embodiment 11 639 Example 12 652 Embodiment 13 368 Embodiment 14 353 Comparative Example 1 351 Comparative Example 2 303

[0082] It can be seen from Examples 1-6 in Table 1 that as the amount of sulfate ions increases, the hydrothermally generated boehmite gradually changes into a hollow sphere due to a change in appearance, and its specific surface area also increases continuously, and the adsorption amount increases accordingly.

[0083] It can be seen from Examples 1-12 in Table 1 that when aluminum nitrate is used as the first aluminum salt, as the molar ratio of sulfate ions to nitrate ions increases from 18:1 to 18:3, the change in the adsorption of boehmite is not as large as when aluminum chloride is used as the first aluminum salt. However, when the ratio increases to 18:4, the adsorption amount suddenly increases, which may be related to the competitiveness between sulfate ions and aluminum chloride ions and nitrate ions in the ability to regulate the morphology of boehmite.

[0084] It can be seen from Example 1, Examples 13-14 and Comparative Examples 1-2 in Table 1 that different amounts of carbon dioxide also affect the adsorption effect of boehmite. When the volume proportion of carbon dioxide in the mixed gas is too high, not only will the utilization rate of carbon dioxide decrease, but also the excessively high concentration of carbon dioxide will cause the pH value of the local area around the bubble to temporarily decrease at the moment of being bubbled into the reaction system, which is not conducive to the growth of boehmite in the subsequent reaction system; when the volume proportion of carbon dioxide in the mixed gas is too low, the number of crystal nuclei generated in the reaction system is small, and the crystal size is easy to increase, causing the particle size of the subsequently generated boehmite to increase, which is not conducive to obtaining boehmite with small particle size.

[0085] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing boehmite with high adsorption performance, characterized in that: The method comprises the following steps: adding a second aluminum salt to a prepared first aluminum salt solution, then adding a precipitant, and transferring the solution to a reactor for hydrothermal reaction to obtain the boehmite.

2. The method for preparing boehmite with high adsorption performance according to claim 1, characterized in that: The anions in the first aluminum salt solution are chloride ions or nitrate ions.

3. The method for preparing boehmite with high adsorption performance according to claim 1, characterized in that: The anion in the second aluminum salt is a sulfate ion.

4. The method for preparing boehmite with high adsorption performance according to claim 2 or 3, characterized in that: The molar ratio of the chloride ion or nitrate ion to the sulfate ion is 18:1-3:

1.

5. The method for preparing boehmite with high adsorption performance according to claim 1, characterized in that: The precipitant is urea.

6. The method for preparing boehmite with high adsorption performance according to claim 1, characterized in that: The hydrothermal reaction conditions are as follows: heating to a pre-reaction temperature, introducing a mixed gas, and then heating to a reaction temperature to carry out the reaction.

7. The method for preparing boehmite with high adsorption performance according to claim 6, characterized in that: The pre-reaction temperature is 100-160°C.

8. The method for preparing boehmite with high adsorption performance according to claim 6, characterized in that: The reaction temperature is 180-250°C.

9. The method for preparing boehmite with high adsorption performance according to claim 6, characterized in that: The mixed gas is obtained by mixing at least one of oxygen, nitrogen and inert gas with carbon dioxide gas.

10. Boehmite with high adsorption performance prepared by the preparation method according to any one of claims 1 to 9.