Method for preparing Mg-ZIF adsorbent based on normal-temperature water solvent method

Abstract

The invention discloses a method for preparing an Mg-ZIF adsorbent based on a normal-temperature water solvent method. The Mg-ZIF adsorbent is prepared from magnesium chloride and 2-methylimidazole under the conditions of normal temperature and normal pressure. The adsorbent has the following advantages that the prepared adsorbent has high adsorption capacity on ammonia nitrogen and organic pollutants in sewage, the highest adsorption capacity of the ammonia nitrogen can reach 1170 mg g <-1 >, and the highest adsorption capacity of the organic pollutants can reach 772.8 mg g <-1 >. Meanwhile, the content of ammonia nitrogen and COD (Chemical Oxygen Demand) in the sewage is smaller than 5 mg L <-1 > and 50 mg L <-1 >, and meets the first-grade A index requirements of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant GB18918-2002; the adsorbent has a good adsorption effect on ammonia nitrogen and organic pollutants in water under an alkaline condition. The method has the advantages of mild and controllable conditions, low production cost and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a method for preparing a Mg-ZIF adsorbent based on a normal-temperature water solvent method. Background Art

[0002] With the rapid development of industry, the discharge of various types of wastewater is increasing year by year. Wastewater containing ammonia nitrogen and organic pollutants exists in various types of wastewater. Currently, the mainstream technical methods for removing ammonia nitrogen and organic pollutants are mainly biochemical methods. In the biochemical system, the anaerobic unit hydrolyzes the macromolecular organic pollutants in water and decomposes them into easily degradable small-molecular organic pollutants. In addition, in the aerobic unit, aerobic bacteria further decompose the organic pollutants into CO2 and H2O. Ammonia nitrogen is oxidized to nitrate nitrogen and nitrite nitrogen and then refluxed to the anoxic unit for denitrification, and is discharged as nitrogen gas, ultimately achieving the removal of ammonia nitrogen and organic pollutants. The biochemical method for removing ammonia nitrogen and organic pollutants in water has good economy but is affected by environmental temperature and microbial activity, and the efficiency of removing ammonia nitrogen and organic pollutants is relatively low. In view of the above problems, developing adsorbent products with high adsorption capacity, simple preparation process, and low production cost for removing ammonia nitrogen and organic pollutants in sewage is the key to solving the industrial application of adsorption technology. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems in the related art to some extent. For this reason, an object of the present invention is to provide a Mg-ZIF adsorbent prepared from magnesium chloride and 2-methylimidazole under normal temperature and pressure conditions. The adsorbent has the following advantages: (1) The prepared adsorbent has a high adsorption capacity for ammonia nitrogen and organic pollutants in sewage. The maximum adsorption capacity of ammonia nitrogen can reach 1170 mg g -1 . At the same time, the ammonia nitrogen and COD contents in the sewage are less than 5 mg L -1 and 50 mg L -1 to meet the requirements of the first-class A index of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" GB18918-2002; (2) The adsorbent has good adsorption effects on ammonia nitrogen and organic pollutants in water under alkaline conditions. (3) It is prepared by a one-step method using a normal-temperature aqueous solution method, with the advantages of mild and controllable conditions and low production cost.

[0004] In one aspect of the present invention, a method for preparing a Mg-ZIF adsorbent based on a normal-temperature water solvent method is provided. According to an embodiment of the present invention, the method includes:

[0005] Dissolve magnesium chloride and 2-methylimidazole in 20 mL of deionized water respectively, and obtain solution A and solution B after complete dissolution;

[0006] Slowly add solution B to solution A, continue stirring and reacting for several hours, then place it in a centrifuge and centrifuge for several hours. After continuous centrifugation several times, a wet-based Mg-ZIF adsorbent is obtained.

[0007] Put the wet-based Mg-ZIF adsorbent into a constant-temperature drying oven and dry it at a certain temperature for several hours. After grinding, the Mg-ZIF adsorbent is obtained.

[0008] When the Mg-ZIF adsorbent adsorbs pollutants in water, add a certain mass of the Mg-ZIF adsorbent to the sewage. Under the conditions of sewage pH > 7 and magnetic stirring, after several hours of adsorption time, the best adsorption effect on ammonia nitrogen and organic pollutants in the sewage is achieved.

[0009] In the second aspect of the present invention, the present invention proposes a preparation method of a method for preparing a Mg-ZIF adsorbent based on a normal-temperature water solvent method. According to an embodiment of the present invention, the Mg-ZIF adsorbent is prepared by using the method described in the first aspect of the present invention.

[0010] The preparation method of the Mg-ZIF adsorbent provided by the present invention has the following advantages:

[0011] The prepared adsorbent has a high adsorption capacity for ammonia nitrogen and organic pollutants in sewage. The highest adsorption capacity of ammonia nitrogen can reach 1170 mg / g. -1 The highest adsorption capacity of organic pollutants can reach 772.8 mg / g. -1 At the same time, the ammonia nitrogen and COD contents in the sewage are less than 5 mg / L -1 and 50 mg / L -1 which meet the requirements of the first-class A indicators of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" GB18918-2002.

[0012] The adsorbent has good adsorption effects on ammonia nitrogen and organic pollutants in water under alkaline conditions.

[0013] It is prepared by a one-step method using a normal-temperature aqueous solution method, and has the advantages of mild and controllable conditions and low production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The above and / or additional aspects and advantages of the present invention will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, wherein:

[0015] Figure 1 is the XRD characterization diagram of the Mg-ZIF adsorbent obtained according to Example 1 of the present invention;

[0016] Figure 2 is the XPS characterization diagram of the Mg-ZIF adsorbent obtained according to Example 1 of the present invention.

[0017] Figure 3It is the FT-IR characterization diagram of the Mg-ZIF adsorbent obtained according to Embodiment 1 of the present invention;

[0018] Figure 4 It is the adsorption effect of the Mg-ZIF adsorbent obtained according to Embodiment 1 of the present invention when applied to sewage treatment. Detailed implementation manners

[0019] The embodiments of the present invention will be described in detail below. The examples are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] In addition, the terms "first", "second", "third", "fourth", "fifth", and "sixth" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first", "second", "third", "fourth", "fifth", and "sixth" may explicitly or implicitly include at least one of the features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0021] The effective substance contents of magnesium chloride and 2-methylimidazole in the present invention are both ≥ 99 wt%.

[0022] In one aspect of the present invention, the present invention provides a preparation method of a Mg-ZIF adsorbent based on a normal-temperature water solvent method. According to an embodiment of the present invention, the method includes:

[0023] S100: Dissolve magnesium chloride and 2-methylimidazole in 20 mL of deionized water respectively. After complete dissolution, solution A and solution B are obtained respectively.

[0024] In this step, magnesium chloride and 2-methylimidazole are dissolved in 20 mL of deionized water respectively, and after stirring evenly, solution A and solution B are obtained. The inventor found through experiments that magnesium chloride and 2-methylimidazole need to be separately prepared into solution A and solution B. Mixing and dissolving the AB solid reagents will greatly reduce the ability of Mg-ZIF to adsorb ammonia nitrogen and organic pollutants.

[0025] In some embodiments, the concentrations of magnesium chloride and 2-methylimidazole are respectively (0.05 - 0.15) mol:(0.01 - 0.05) mol. The inventor found that when the molar ratio of magnesium chloride and 2-methylimidazole conforms to this ratio range, a good Mg-ZIF material can be obtained.

[0026] S200: Slowly add solution B into solution A, continue stirring and reacting for several hours, then place it in a centrifuge for centrifugation for several hours. After continuous centrifugation for several times, a wet-based Mg-ZIF adsorbent is obtained.

[0027] In some embodiments, in this step, solution B is added to solution A and mixed to obtain a Mg-ZIF solution. The inventor found that the dosing order of solution A and solution B cannot be reversed, and only solution B can be added to solution A. Otherwise, the ability of the produced Mg-ZIF to adsorb ammonia nitrogen and organic pollutants will decrease to a certain extent, which is related to the fact that when Mg ions in solution A are added to the 2-methylimidazole solution, high-concentration Mg ions quickly form Mg-ZIF.

[0028] In some embodiments, the stirring reaction time is (2 - 5) h. For example, 2 h, 2.5 h, 3 h, 4 h, 5 h, etc. If the stirring time is too short, the specific surface area of the Mg-ZIF material formed by solution B and solution A is small, resulting in a decrease in the ability to adsorb ammonia nitrogen and organic pollutants in water; if the stirring time is too long, the volume of the Mg-ZIF material formed by the reaction of solution B and solution A is too large, and the pore structure also increases accordingly, resulting in a decrease in the ability to adsorb ammonia nitrogen and organic pollutants.

[0029] In some embodiments, the rotation speed of the magnetic stirrer is 200 - 600 r / min. For example, 200 r / min, 250 r / min, 300 r / min, 400 r / min, 500 r / min, etc. At a low rotation speed, solution B cannot react with solution A uniformly to form a Mg-ZIF material; at a high rotation speed, due to the too fast rotation speed, the solution turbulence intensifies, which is not conducive to the uniform formation of the Mg-ZIF material.

[0030] In some embodiments, the stirring reaction temperature of the magnetic stirrer is (10 - 80) °C. For example, 10 °C, 15 °C, 20 °C, 30 °C, 50 °C, etc. At a low temperature reaction, the reaction rate of Mg ions and 2-methylimidazole decreases, and the specific surface area of the synthesized Mg-ZIF is small, and the ability to adsorb pollutants is low. At a high temperature reaction, the intermolecular thermal motion intensifies, the reaction rate accelerates, resulting in incomplete reaction, which also has a negative impact on the adsorption capacity of the adsorbent.

[0031] In some embodiments, the rotation speed of the centrifuge is 500 - 4000 r / min. For example, 500 r / min, 550 r / min, 700 r / min, 1100 r / min, 4000 r / min, etc.

[0032] In some embodiments, the centrifugation time of the centrifuge is 1 - 30 min. For example, 1 min, 3 min, 10 min, 12 min, 30 min, etc.

[0033] In some embodiments, the number of centrifugations of the centrifuge is (1 - 5) times. For example, 1 time, 2 times, 3 times, 4 times, 5 times, etc.

[0034] S300: Put the wet-based Mg-ZIF adsorbent into a constant-temperature drying oven, dry it for several hours at a certain temperature, and obtain the Mg-ZIF adsorbent after grinding.

[0035] In some embodiments, put the wet-based Mg-ZIF adsorbent into a constant-temperature dryer, and the constant-temperature drying temperature is (50 - 200) °C. For example, 50 °C, 65 °C, 100 °C, 110 °C, 200 °C, etc. If the constant-temperature drying temperature is too high, the water in the wet-based Mg-ZIF adsorbent evaporates rapidly, damaging the pore structure of Mg-ZIF and reducing the adsorption capacity for pollutants; if the constant-temperature drying temperature is too low, the wet-based Mg-ZIF adsorbent is not easily dried.

[0036] In some embodiments, the time for constant-temperature drying of the wet-based Mg-ZIF adsorbent is 1 - 8 h. For example, 1 h, 1.5 h, 2 h, 4 h, 6 h, etc.

[0037] S400: When adsorbing pollutants in water, add a certain mass of Mg-ZIF adsorbent to the sewage. Under the conditions of sewage pH > 7 and magnetic stirring, after several hours of adsorption time, the best adsorption effect on ammonia nitrogen and organic pollutants in the sewage is achieved.

[0038] In some embodiments, add the Mg-ZIF adsorbent to the sewage with an alkaline pH for the adsorption performance experiment, and the sewage pH is 7.5 - 14.0. For example, 7.5, 8.0, 9.0, 10.0, 11.0, etc. When the pH is lower, the charge adsorption effect of the alkali metal Mg ions on the sewage is reduced.

[0039] In some embodiments, the stirring speed of the Mg-ZIF adsorbent when adsorbing pollutants in the sewage is (300 - 500) r / min. For example, 300 r / min, 350 r / min, 400 r / min, 500 r / min, etc. At a low rotation speed, the contact probability between the Mg-ZIF adsorbent and the pollutants in the water is relatively small, resulting in a decrease in the adsorption capacity; at a higher rotation speed, the pollutants adsorbed by the Mg-ZIF adsorbent are easily desorbed by strong turbulence, reducing the adsorption capacity of the pollutants.

[0040] In some embodiments, the adsorption time of the Mg-ZIF adsorbent when adsorbing pollutants in the sewage is (2 - 8) h. For example, 2 h, 2.5 h, 3 h, 6 h, 8 h, etc.

[0041] In the second aspect of the present invention, the present invention proposes a method for preparing a Mg-ZIF adsorbent based on a normal-temperature water solvent method. According to an embodiment of the present invention, the Mg-ZIF adsorbent is prepared by the above method. The adsorbent is Mg-ZIF prepared from magnesium chloride and 2-methylimidazole under normal temperature and pressure conditions. Under normal temperature and pressure conditions, using water as a solvent, a Mg-ZIF adsorbent with the ability to adsorb ammonia nitrogen and organic pollutants in water is prepared in one step. It has a good adsorption effect on ammonia nitrogen and organic pollutants in sewage under alkaline conditions, and is suitable for removing ammonia nitrogen and organic pollutants in water in cooperation with microorganisms in the aerobic unit of the biochemical system or for separately removing ammonia nitrogen and organic pollutants in alkaline sewage. In summary, the Mg-ZIF adsorbent of the present invention has the following advantages: (1) The prepared adsorbent has a high adsorption capacity for ammonia nitrogen and organic pollutants in sewage. The highest adsorption capacity for ammonia nitrogen can reach 1170 mg g -1 , and the highest adsorption capacity for organic pollutants can reach 772.8 mg g -1 . At the same time, the ammonia nitrogen and COD content in the sewage are less than 5 mg L -1 and 50 mg L -1 , meeting the requirements of the first-class A index of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants" GB18918-2002; (2) The adsorbent has a good adsorption effect on ammonia nitrogen and organic pollutants in water under alkaline conditions. 3 It is prepared by a one-step normal-temperature aqueous solution method, with the advantages of mild and controllable conditions and low production cost.

[0042] It should be noted that the characteristics and advantages described above for the method of preparing the Mg-ZIF adsorbent also apply to this adsorbent and will not be elaborated here.

[0043] Next, with reference to specific embodiments, the present invention will be described. It should be noted that these embodiments are only descriptive and do not limit the present invention in any way.

[0044] As used in the present invention, the "molar concentration" refers to the ratio of the mass of the added substance to the molecular weight of the substance.

[0045] Example 1

[0046] (1) Dissolve 0.09 mol of magnesium chloride and 0.03 mol of 2-methylimidazole in 20 mL of deionized water respectively. After complete dissolution, solution A and solution B are obtained respectively;

[0047] 2 Slowly add solution B to solution A. After reacting for 187 min on a magnetic stirrer at 29 °C and 380 r / min, place it in a centrifuge and centrifuge for 30 min at 4000 r / min. After continuous centrifugation 5 times, a wet-based Mg-ZIF adsorbent is obtained.

[0048] 3. The wet-based Mg-ZIF adsorbent was placed in a constant-temperature drying oven and dried at a certain temperature of 120 °C for 5 hours. After grinding, the Mg-ZIF adsorbent was obtained.

[0049] The XRD characterization results of the Mg-ZIF adsorbent obtained in Example 1 are as Figure 1 shown, and the XPS characterization results are as Figure 2 shown. Among them, Figure 2 the existing form of Mg element in the Mg-ZIF adsorbent, Figure 2 the changes of N and C elements in the Mg-ZIF adsorbent before and after adsorption. According to Figure 1 and 2 , it can be seen that the Mg-ZIF adsorbent prepared in Example 1 has good adsorption capacity. At the same time, Mg-ZIF was successfully synthesized, and the increase in the peak intensity of N and C elements after adsorption shows that the adsorbent has an obvious adsorption effect on ammonia nitrogen and organic pollutants.

[0050] When adsorbing pollutants in water, 0.1 g / L of Mg-ZIF adsorbent was added to the sewage. The pH of the sewage was 12.0, and the magnetic stirring speed was 450 r / min. After 6.5 hours of adsorption, the best adsorption effect on ammonia nitrogen and organic pollutants in the sewage was achieved.

[0051] Example 2

[0052] 0.05 mol of magnesium chloride was added, and other conditions were the same as in Example 1.

[0053] Example 3

[0054] 0.15 mol of magnesium chloride was added, and other conditions were the same as in Example 1.

[0055] Experimental Example 1

[0056] An industrial application test of the Mg-ZIF adsorbent was carried out in a sewage treatment facility in a certain village and town in Panjin City. During the application process, the adsorbent was added to the aerobic tank of the sewage biochemical unit, and the dosage of the adsorbent was 0.1 g / L. Before the application of the adsorbent, the ammonia nitrogen content in the sewage was between 20 - 30 mg / L, and the COD content was between 200 - 300 mg / L. After one-year on-site application, it was proved that the treatment indexes of the Mg-ZIF adsorbent for ammonia nitrogen and COD in the sewage were better than the technical indexes before adding the Mg-ZIF adsorbent.

[0057] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a Mg-ZIF adsorbent based on a room-temperature water solvent method, characterized in that, The method includes: Dissolve magnesium chloride and 2-methylimidazole in 20 mL of deionized water respectively. After complete dissolution, solution A and solution B are obtained respectively. Slowly add solution B to solution A. After continuously stirring and reacting for several hours, put it into a centrifuge for centrifuging for several hours. After continuous centrifuging for several times, a wet-based Mg-ZIF adsorbent is obtained. Put the wet-based Mg-ZIF adsorbent into a constant temperature drying oven and dry it at a certain temperature for several hours. After grinding, a Mg-ZIF adsorbent is obtained. When adsorbing pollutants in water, add a certain mass of Mg-ZIF adsorbent to the sewage. Under the conditions that the pH of the sewage > 7 and magnetic stirring, after an adsorption time of several hours, the best adsorption effect on ammonia nitrogen and organic pollutants in the sewage is achieved.

2. The method according to claim 1, wherein In step 1, the concentrations of the magnesium chloride and 2-methylimidazole are respectively (0.05 - 0.15) mol : (0.01 - 0.05) mol.

3. The method according to claim 1, wherein In step 2, the rotation speed of the magnetic stirrer is (200 - 600) r / min.

4. The method according to claim 1, wherein In step 2, the stirring reaction time is (2 - 5) h.

5. The method according to claim 1, characterized in that, In step 2, the stirring reaction temperature is (10 - 80) °C.

6. The method according to claim 1, characterized in that In step 2, the rotation speed of the centrifuge is (500 - 4000) r / min, the centrifugation time of the centrifuge is (1 - 30) min, and the number of centrifugation times of the centrifuge is (1 - 5) times.

7. The method according to claim 1, characterized in that, In step 3, put the wet-based Mg-ZIF adsorbent into a constant temperature drying oven for drying. Among them, the constant temperature drying temperature is (50 - 200) °C, and the constant temperature drying time is (1 - 8) h.

8. The method according to claim 1, characterized in that, In step 4, add the Mg-ZIF adsorbent to the sewage for adsorption, and the pH value of the sewage is 7.5 - 14.

0.

9. The method according to claim 1, wherein In step 4, add the Mg-ZIF adsorbent to the sewage for adsorption, and the magnetic stirring rotation speed during adsorption is (300 - 500) r / min.

10. The method according to claim 1, wherein In step 4, add the Mg-ZIF adsorbent to the sewage for adsorption, and the adsorption time is (2 - 8) h.

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