A method for preparing a cobalt-based semi-crystalline adsorbent

Abstract

A method for preparing a cobalt-based semi-crystalline adsorbent belongs to the field of nanomaterials and environmental materials preparation. This method, based on the addition of auxiliary reagents, effectively improves the electron-donating characteristics of the cobalt-based semi-crystalline adsorbent and enhances its adsorption capacity for heavy metal ions by simultaneously introducing electron-rich terephthalic acid and urea into the system. The invention utilizes auxiliary reagents to adjust the pH of the system while simultaneously promoting the deprotonation process of terephthalic acid and maintaining the coordination activity of urea. This facilitates the rapid self-assembly and assembly process between organic ligands and metal ions at room temperature, ensuring the sufficient introduction of organic ligands with abundant lone pair electrons into the cobalt-based semi-crystalline adsorbent, thereby improving its electron-donating capacity and enhancing its adsorption and removal capacity for heavy metal ions.

Description

Technical Field

[0001] This invention relates to the field of nanomaterials and environmental materials preparation, and particularly to a method for preparing a cobalt-based semi-crystalline adsorbent. Background Technology

[0002] Semi-crystalline materials are a special category of materials that fall between metal-organic frameworks (MOFs) and metal-organic gels (MOGs), exhibiting crystallinity between MOFs and MOGs. Compared to MOFs, semi-crystalline materials possess a variety of pore types, hierarchical porous structures, and more exposed active sites. Compared to MOGs, semi-crystalline materials exhibit relatively superior crystallinity and relatively more stable physicochemical properties. Based on these advantages, semi-crystalline materials can be used as adsorbents and have found widespread application in the field of adsorption.

[0003] To enhance the adsorption of heavy metal ions by semi-crystalline adsorbents, the electron-donating characteristics of the semi-crystalline adsorbents can be improved by introducing lone pairs of electrons. The empty orbitals of heavy metal ions can accommodate lone pairs of electrons in the semi-crystalline adsorbents, making it easier for the two to coordinate and thus quickly adsorb and remove heavy metal ions. Introducing electron-rich organic ligands is an effective means to directly regulate the electron-donating characteristics of the adsorbent.

[0004] The article titled "..." was published in the *Journal of Solid State Chemistry* in July 2024.

[0005] The article "MOF-525 and Fe-loaded MOF-525 for the selective adsorption removal of Cu(II) and Cr(VI)" (authors are Yun Kong, Hui Xu, Wenbin Hu, Bowen Huang, Renjuan Wang, Jin Shao, Qi Chen, Qiang Yang);

[0006] In May 2018, an article entitled "Immobilization of thiol-functionalized ionic liquids onto the surface of MlL-101(Cr) frameworks by S-Cr coordination bond for biodiesel production" was published in the journal Colloids and Surfaces A: Physicochemical and Engineering Aspects (authors: Mingjuan Han, Ying Li, Zheng Gu, Huali Shi, Chong Chen, Qiang Wang, Hui Wan, Guofeng Guan).

[0007] In September 2015, an article entitled "Adsorption of Uranyl lons on Amin-functionalization of MIL-101(Cr) Nanoparticles by aFacile Coordination-based Post-synthetic Strategy and X-ray Absorption Spectroscopy" was published in the journal SCIENTIFIC REPORTS (authors: Jian-Yong Zhang, Na Zhang, Linjuan Zhang, Yongzheng Fang, Wei Deng, Ming Yu, Ziqiang Wang, Lina Li, Xiyan Liu, Jingye Li).

[0008] All three articles above support the theory that heavy metal ions coordinate with materials that have lone pairs of electrons.

[0009] Currently, although many studies have shown that introducing electron-rich ligands into MOFs or MOGs can improve the adsorption and removal performance of adsorbents for heavy metal ions, there are still relatively few studies on semi-crystalline adsorbents.

[0010] Furthermore, semi-crystalline adsorbents can be prepared at room temperature. This preparation method is simple to operate, has low energy consumption, and high product yield. However, room temperature limits the solubility of ligands, thus affecting the structural stability of the material. To better achieve the preparation of semi-crystalline adsorbents at room temperature, it is necessary to add auxiliary reagents. On the one hand, this accelerates the dissolution of ligands; on the other hand, it adjusts the pH of the system. By selecting appropriate auxiliary reagents, the reactivity of nitrogen-containing ligands can be stimulated, and the deprotonation ability of carboxyl ligands can be promoted. Ultimately, this promotes the rapid self-assembly process between organic ligands and metal ions at room temperature, forming an electron-rich semi-crystalline adsorbent with good adsorption capacity for heavy metal ions. However, how to optimize the room temperature preparation method, introduce lone pairs of electrons into the semi-crystalline adsorbent, and improve its adsorption and removal capacity for heavy metal ions still requires further exploration. Summary of the Invention

[0011] The purpose of this invention is to solve the existing problems mentioned in the background art by proposing a method for preparing a cobalt-based semi-crystalline adsorbent. This method, based on the addition of auxiliary reagents, can effectively improve the electron-donating characteristics of the cobalt-based semi-crystalline adsorbent and enhance its adsorption capacity for heavy metal ions by simultaneously introducing electron-rich terephthalic acid and urea into the system.

[0012] A method for preparing a cobalt-based semi-crystalline adsorbent includes the following steps:

[0013] Step 1: Weigh out the Co salt, dissolve it in an ethanol solution, and name it Solution A. Make the molar concentration of the Co salt in Solution A range from 0.1 to 1 mol / L.

[0014] Step 2: Weigh out terephthalic acid and add it to deionized water, naming it solution B, so that the molar concentration of terephthalic acid in solution B is in the range of 0.1-1 mol / L;

[0015] Step 3: Weigh out urea and add it to deionized water, naming it solution C, so that the molar concentration of urea in solution C is in the range of 0.2-4 mol / L;

[0016] Step 4: At room temperature, mix solutions A, B, and C to make a volume ratio of 1:1:1 to 1:1:2. After stirring evenly, add auxiliary reagents to adjust the pH of the system to 7-9 and name it solution D.

[0017] Step 5: Stir solution D under uniform stirring conditions until solution D becomes a flowable gel state, to obtain colloidal substance E;

[0018] Step 6: Wash the colloidal substance E with sufficient ethanol, centrifuge at 10,000 rpm to remove excess ion solution and ligands, and dry in an oven to obtain powdered cobalt-based semi-crystalline adsorbent.

[0019] The Co salt used in step one is cobalt nitrate, cobalt sulfate, or cobalt chloride.

[0020] The room temperature conditions in step four are 20-35℃, and the stirring speed is 100-250 rpm.

[0021] The auxiliary reagent in step four is trimethylamine or triethylamine.

[0022] In step five, the stirring speed is 100-250 rpm.

[0023] In step six, the amount of ethanol used is 6-8 times the volume of solution A in step four.

[0024] In step six, the oven drying process involves a heating rate of 5-7 degrees Celsius per minute, raising the temperature to 45-80 degrees Celsius, and holding the temperature for 3-6 hours.

[0025] The beneficial effects of this invention are:

[0026] (1) This invention is carried out at room temperature, which significantly reduces the requirements for preparation temperature and simplifies the preparation conditions and process of cobalt-based semi-crystalline adsorbent.

[0027] (2) This invention utilizes auxiliary reagents to adjust the pH in the system, while also promoting the deprotonation process of terephthalic acid and maintaining the coordination activity of urea. This facilitates the rapid self-assembly and assembly process between organic ligands and metal ions at room temperature, ensuring that organic ligands with abundant lone pair electrons are fully introduced into the cobalt-based semi-crystalline adsorbent, thereby improving the electron-donating ability of the cobalt-based semi-crystalline adsorbent and enhancing its adsorption and removal capacity for heavy metal ions. Attached Figure Description

[0028] Figure 1 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0029] Example 1.

[0030] Please see Figure 1 As shown;

[0031] A method for preparing a cobalt-based semi-crystalline adsorbent includes the following steps:

[0032] Step 1: Weigh 1 mol of cobalt nitrate, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 1 mol / L.

[0033] Step 2: Weigh 1 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 1 mol / L.

[0034] Step 3: Weigh 2 mol of urea and add it to 1 L of deionized water, name it solution C, and the molar concentration of solution C is 2 mol / L;

[0035] Step 4: At room temperature (25℃), mix 50 mL of solution A, 50 mL of solution B, and 50 mL of solution C in a volume ratio of 1:1:1. Stir the mixture at 100 rpm and add trimethylamine as an auxiliary reagent to adjust the pH of the system to 7.5. Name the solution D.

[0036] Step 5: Stir solution D at a constant speed of 100 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0037] Step 6: Wash the colloidal substance E with 300 mL of ethanol, centrifuge at 10000 rpm to remove excess ion solution and ligands, heat the oven at a rate of 5 °C / min to 45 °C, and keep it at that temperature for 3 hours to obtain a powdered cobalt-based semi-crystalline adsorbent.

[0038] Example 2.

[0039] Please see Figure 1 As shown;

[0040] A method for preparing a cobalt-based semi-crystalline adsorbent includes the following steps:

[0041] Step 1: Weigh 0.3 mol of cobalt sulfate, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 0.3 mol / L.

[0042] Step 2: Weigh 0.3 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 0.3 mol / L.

[0043] Step 3: Weigh 0.9 mol of urea and add it to 1 L of deionized water, name it solution C, and the molar concentration of solution C is 0.9 mol / L;

[0044] Step 4: At room temperature (20℃), mix 100mL of solution A, 100mL of solution B, and 100mL of solution C in a volume ratio of 1:1:1. Stir the mixture at 120rpm and add trimethylamine as an auxiliary reagent to adjust the pH of the system to 8. Name the solution D.

[0045] Step 5: Stir solution D at a constant speed of 120 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0046] Step 6: Wash the colloidal substance E with 600 mL of ethanol, centrifuge at 10000 rpm to remove excess ion solution and ligands, heat the oven at a rate of 6 °C / min to 50 °C, and hold for 3.5 hours to obtain a powdered cobalt-based semi-crystalline adsorbent.

[0047] Example 3.

[0048] Please see Figure 1 As shown;

[0049] A method for preparing a cobalt-based semi-crystalline adsorbent includes the following steps:

[0050] Step 1: Weigh 0.5 mol of cobalt chloride, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 0.5 mol / L.

[0051] Step 2: Weigh 0.5 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 0.5 mol / L.

[0052] Step 3: Weigh 2 mol of urea and add it to 1 L of deionized water, name it solution C, and the molar concentration of solution C is 2 mol / L;

[0053] Step 4: At room temperature (30℃), mix 50 mL of solution A, 50 mL of solution B, and 100 mL of solution C in a volume ratio of 1:1:2. Stir the mixture at 150 rpm and add triethylamine as an auxiliary reagent to adjust the pH of the system to 9. Name the solution D.

[0054] Step 5: Stir solution D at a constant speed of 200 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0055] Step 6: Wash the colloidal substance E with 400 mL of ethanol, centrifuge at 10000 rpm to remove excess ion solution and ligands, heat the oven at a rate of 7℃ / min until it reaches 70℃, and keep it at that temperature for 6 hours to obtain a powdered cobalt-based semi-crystalline adsorbent.

[0056] Comparative Example 1:

[0057] A method for preparing a cobalt-based adsorbent includes the following steps:

[0058] Step 1: Weigh 1 mol of cobalt nitrate, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 1 mol / L.

[0059] Step 2: Weigh 1 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 1 mol / L.

[0060] Step 3: Weigh 2 mol of urea and add it to 1 L of deionized water, name it solution C, and the molar concentration of solution C is 2 mol / L;

[0061] Step 4: At room temperature (25℃), mix 50 mL of solution A, 50 mL of solution B, and 50 mL of solution C in a volume ratio of 1:1:1, and stir at 100 rpm. This mixture is then named solution D.

[0062] Step 5: Stir solution D at a constant speed of 100 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0063] Step 6: Wash the colloidal substance E with 300 mL of ethanol, centrifuge at 10000 rpm to remove excess ion solution and ligands, heat the oven at a rate of 5 °C / min to 45 °C, and keep it at that temperature for 3 hours to obtain powdered cobalt-based adsorbent.

[0064] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not use auxiliary reagents, while the other components, preparation steps and parameters were the same.

[0065] Comparative Example 2:

[0066] A method for preparing a cobalt-based adsorbent includes the following steps:

[0067] Step 1: Weigh 0.3 mol of cobalt sulfate, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 0.3 mol / L.

[0068] Step 2: Weigh 0.3 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 0.3 mol / L.

[0069] Step 3: Weigh 0.9 mol of urea and add it to 1 L of deionized water, name it solution C, and the molar concentration of solution C is 0.9 mol / L;

[0070] Step 4: At room temperature (20℃), mix 100mL of solution A, 100mL of solution B, and 100mL of solution C in a volume ratio of 1:1:1. Stir the mixture at 120rpm and add trimethylamine as an auxiliary reagent to adjust the pH of the system to 12. Name the solution D.

[0071] Step 5: Stir solution D at a constant speed of 120 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0072] Step 6: Wash the colloidal substance E with 600 mL of ethanol, centrifuge at 10000 rpm to remove excess ion solution and ligands, heat the oven at a rate of 6 °C / min until it reaches 50 °C, and hold for 3.5 hours to obtain powdered cobalt-based adsorbent.

[0073] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 uses trimethylamine as an auxiliary reagent and adjusts the pH of the system to 12, while the other components, preparation steps and parameters are the same.

[0074] Comparative Example 3:

[0075] A method for preparing a cobalt-based adsorbent includes the following steps:

[0076] Step 1: Weigh 0.5 mol of cobalt chloride, dissolve it in 1 L of ethanol solution, and name it solution A. The molar concentration of solution A is 0.5 mol / L.

[0077] Step 2: Weigh 0.5 mol of terephthalic acid and add it to 1 L of deionized water, naming it solution B. The molar concentration of solution B is 0.5 mol / L.

[0078] Step 3: At room temperature (30℃), mix 50 mL of solution A and 50 mL of solution B at a volume ratio of 1:1, stir at 150 rpm, add triethylamine as an auxiliary reagent, adjust the pH of the system to 9, and name it solution D.

[0079] Step 4: Stir solution D at a constant speed of 200 rpm until solution D becomes a flowable gel, thus obtaining colloidal substance E;

[0080] Step 5: Wash the colloidal substance E with 400 mL of ethanol, centrifuge at 10000 rpm to remove excess ionic solution and ligands, heat the oven at a rate of 7℃ / min until it reaches 70℃, and keep it at that temperature for 6 hours to obtain powdered cobalt-based adsorbent.

[0081] The difference between Comparative Example 3 and Example 3 is that no urea was added in Comparative Example 3, while the other components, preparation steps and parameters were the same.

[0082] Adsorption performance test of heavy metal Cr(VI) solution:

[0083] The cobalt-based semi-crystalline adsorbents prepared by Examples 1-3 and the cobalt-based adsorbents prepared by Comparative Examples 1-3 were used to conduct adsorption experiments on the same Cr(VI) solution. The concentration of the remaining Cr(VI) in the solution was determined by the diphenylcarbazide spectrophotometric method in GB 7467-87.

[0084] The adsorption capacity of the above adsorbents for Cr(VI) is shown in Table 1.

[0085] Table 1 (Unit: mg / g)

[0086] Cr(VI) adsorption capacity Example 1 47.9 Example 2 48.1 Example 3 49.6 Comparative Example 1 2.7 Comparative Example 2 28.8 Comparative Example 3 10.2

[0087] As can be seen from the test results in Table 1, compared with Comparative Examples 1-3, the cobalt-based semi-crystalline adsorbents prepared in Examples 1-3 of the present invention have better adsorption capacity for heavy metal ions.

Claims

1. A method for preparing a cobalt-based semi-crystalline adsorbent, characterized in that, Includes the following steps: Step 1: Weigh out the Co salt, dissolve it in an ethanol solution, and name it Solution A. Make the molar concentration of the Co salt in Solution A range from 0.1 to 1 mol / L. Step 2: Weigh out terephthalic acid and add it to deionized water, naming it solution B, so that the molar concentration of terephthalic acid in solution B is in the range of 0.1-1 mol / L; Step 3: Weigh out urea and add it to deionized water, naming it solution C, so that the molar concentration of urea in solution C is in the range of 0.2-4 mol / L; Step 4: At room temperature, mix solutions A, B, and C to make a volume ratio of 1:1:1 to 1:1:

2. After stirring evenly, add auxiliary reagents to adjust the pH of the system to 7-9 and name it solution D. Step 5: Stir solution D under uniform stirring conditions until solution D becomes a flowable gel state, to obtain colloidal substance E; Step 6: Wash the colloidal substance E with sufficient ethanol, centrifuge at 10,000 rpm to remove excess ion solution and ligands, and dry in an oven to obtain powdered cobalt-based semi-crystalline adsorbent. The auxiliary reagent in step four is trimethylamine or triethylamine.

2. The method for preparing a cobalt-based semi-crystalline adsorbent according to claim 1, characterized in that: The Co salt used in step one is cobalt nitrate, cobalt sulfate, or cobalt chloride.

3. The method for preparing a cobalt-based semi-crystalline adsorbent according to claim 1, characterized in that: The room temperature conditions in step four are 20-35℃, and the stirring speed is 100-250 rpm.

4. The method for preparing a cobalt-based semi-crystalline adsorbent according to claim 1, characterized in that: In step five, the stirring speed is 100-250 rpm.

5. The method for preparing a cobalt-based semi-crystalline adsorbent according to claim 1, characterized in that: In step six, the amount of ethanol used is 6-8 times the volume of solution A in step four.

6. The method for preparing a cobalt-based semi-crystalline adsorbent according to claim 1, characterized in that: In step six, the oven drying process involves a heating rate of 5-7°C / minute, raising the temperature to 45-80°C, and holding the temperature for 3-6 hours.

Images