Preparation method of ZIF-8 modified ammonia removal resin

Abstract

The invention discloses a preparation method of ZIF-8 modified ammonia removal resin, which comprises the following steps: carrying out ion exchange on cation exchange resin and zinc salt to obtain a precursor loaded with the zinc salt, and carrying out coordination and reaction on 2-methylimidazole and metal salt under certain conditions to obtain in-situ growth ZIF-8. According to the invention, on one hand, a large number of physical adsorption sites are provided for adsorption of ammonia molecules by using the high specific surface area and porous structure of the ZIF-8, so that the ammonia molecules can be fixed in pores of the ZIF-8 through Van der Waals' force, thereby improving the ion exchange efficiency; on the other hand, zinc ions in the ZIF-8 can be used as Lewis acid sites to form coordinate bonds with nitrogen atoms in ammonia molecules, so that the ammonia molecules are stably adsorbed in the structure of the ZIF-8 in the form of complexes. By utilizing the two action mechanisms, the adsorption capacity of the resin on ammonia gas is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of ammonia removal, and in particular to a method for preparing a ZIF-8 modified ammonia removal resin. Background Art

[0002] Ammonia (NH3) is an important chemical raw material and is widely used in agriculture, refrigerants, textiles, pharmaceuticals and other fields. However, ammonia is also a harmful gas with a strong pungent odor, which has a significant impact on human health and the environment. Long-term exposure to an ammonia environment may cause respiratory diseases, eye irritation, and skin allergies. Therefore, the development of efficient ammonia removal technology is of great significance to protecting the environment and human health.

[0003] Existing ammonia removal technologies mainly include physical adsorption and chemical adsorption. Physical adsorption mainly relies on the surface force of the adsorbent to adsorb ammonia to the surface of the adsorbent. Commonly used adsorption materials include activated carbon and molecular sieves. Chemical adsorption converts ammonia into other harmless substances through chemical reactions. Common chemical adsorbents include acidic substances (such as sulfuric acid, phosphoric acid) and transition metal oxides (such as MnO2, CuO). For example, patent CN117942935A introduces a method for adsorbing ammonia using acid-treated activated carbon, which improves its adsorption capacity for ammonia by acid modification and metal impregnation of activated carbon. However, the impregnation-modified adsorbent has poor stability and is prone to secondary pollution during use. Moreover, the adsorption capacity of activated carbon is limited, and it is easy to be saturated in a high-concentration ammonia environment, requiring frequent replacement or regeneration of the adsorbent, which increases operating costs and complexity. The use of cation exchange resins for ammonia removal is considered to be another effective means, using cations to exchange ions with NH4+ to achieve the purpose of removing ammonia. However, compared with activated carbon, the specific surface area and porosity of cation exchange resin are lower, which affects the ion exchange efficiency. To address this problem, patent CN105174243B uses a saponification-free emulsion polymerization method to prepare a polystyrene microsphere, which increases the specific surface area of ​​the resin to a certain extent, but it is still difficult to meet the removal efficiency in a high-concentration ammonia environment.

[0004] In view of this, it is necessary to develop an ammonia removal adsorbent with high adsorption capacity and stable chemical properties to achieve efficient removal of high-concentration environmental ammonia while ensuring that no secondary pollution is caused to the environment. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a method for preparing a ZIF-8 modified ammonia-removing resin.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: a preparation method of ZIF-8 modified ammonia removal resin, comprising the following steps:

[0007] S1: Precursor preparation,

[0008] First, weigh 5-10g of zinc salt, dissolve it in 50-100mL of organic solvent under magnetic stirring to prepare a metal salt solution A with a concentration of 0.5M, then weigh 10-20g of adsorption resin, and evenly disperse it in the above metal salt solution A under magnetic stirring to obtain dispersion B, and finally place it at room temperature for 2-12h to allow zinc ions to exchange with cations in the resin;

[0009] S2: Preparation of ZIF-8 modified resin,

[0010] Weigh 5-40g of 2-methylimidazole, dissolve it in 50-100mL of an organic solvent under magnetic stirring to prepare an organic ligand solution C with a concentration of 1-8M, uniformly mix the solution C and the dispersion B at a ratio of 1:1 under magnetic stirring, add 0.5-1g of a nucleating agent, react at 40-120°C for 2-12h, and obtain a ZIF-8 modified resin after suction filtration;

[0011] S3: Drying treatment,

[0012] The ZIF-8 modified resin prepared in step S2 is treated in a constant temperature drying oven at 30-120° C. for 1-24 hours to obtain a ZIF-8 modified ammonia removal special resin having a water content of 30-50%.

[0013] As a further description of the above technical solution:

[0014] The zinc salt in step S1 is one of zinc sulfate, zinc chloride, zinc nitrate and zinc acetate.

[0015] As a further description of the above technical solution:

[0016] The organic solvent in step S1 and the organic solvent in step S2 are both one of methanol, ethanol, DMAc, DMF and deionized water.

[0017] As a further description of the above technical solution:

[0018] The nucleating agent in step S2 is one of hexadecyltrimethylammonium bromide, ammonium dodecylbenzenesulfonate, polyethylene and pyrrolidone.

[0019] The present invention has the following beneficial effects:

[0020] Compared with the prior art, the present invention utilizes cation exchange resin to exchange ions with zinc salt to obtain a precursor of loaded zinc salt, coordinates 2-methylimidazole with metal salt under certain conditions, and reacts to obtain ZIF-8 grown in situ. In the present invention, on the one hand, the high specific surface area and porous structure of ZIF-8 are used to provide a large number of physical adsorption sites for the adsorption of ammonia molecules, so that ammonia molecules can be fixed in the pores of ZIF-8 by van der Waals forces, thereby improving the ion exchange efficiency; on the other hand, the zinc ions in ZIF-8 can be used as Lewis acid sites to form coordination bonds with nitrogen atoms (with lone pairs of electrons) in ammonia molecules, so that ammonia molecules are stably adsorbed in the structure of ZIF-8 in the form of complexes. The present invention utilizes the above two aspects of the mechanism of action to significantly improve the resin's adsorption capacity for ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the infrared spectra of Examples 1 to 3 of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0023] Example 1

[0024] S1: Precursor preparation,

[0025] First, weigh 4.4 g of zinc salt and dissolve it in 50 mL of ethanol under magnetic stirring to prepare a metal salt solution A with a concentration of 0.5 M. Then weigh 15 g of styrene resin and evenly disperse it in the above metal salt solution under magnetic stirring to obtain dispersion B. Finally, place it at room temperature for 6 hours to allow the zinc ions to exchange with the cations in the resin.

[0026] S2: Preparation of ZIF-8 modified resin,

[0027] 16.42 g of 2-methylimidazole was weighed and dissolved in 50 mL of ethanol under magnetic stirring to prepare a 2-methylimidazole solution C with a concentration of 4 M. Under magnetic stirring, solution C and dispersion B were uniformly mixed in a ratio of 1:1, and 0.5 g of CTAB was added. The mixture was reacted at 60 °C for 6 h, and ZIF-8 modified resin was obtained after filtration.

[0028] S3: Drying treatment,

[0029] The ZIF-8 modified resin prepared in step 2 was treated in a 60° C. constant temperature drying oven for 4 hours to obtain a ZIF-8 modified ammonia removal special resin with a water content of 45%.

[0030] Example 2

[0031] The concentration of 2-methylimidazole in step S2 of Example 1 was adjusted to 3M.

[0032] Example 3

[0033] The concentration of 2-methylimidazole in step S2 of Example 1 was adjusted to 2M.

[0034] Structural characterization and performance testing

[0035] 1. Infrared spectrum test, see the attached Figure 1 .

[0036] 2. BET and NH3 adsorption performance test

[0037] (1) Analytical testing: The BET surface area and pore structure of the material were tested by gas adsorption testing at -195 °C using a Belsorp MAXⅡ analyzer using N2 adsorption and desorption. The total surface area was determined using the Brunauer-Emmett-Taylor (BET) equation.

[0038] (2) NH3 adsorption performance test: Use UTEST static adsorption device to test the gas (NH3) adsorption of the material. Initial efficiency: control the test air volume (12L / min), test resistance (100pa), test concentration (600ppb); pollutant holding capacity: control the test air volume (15L / min), test resistance (100pa), test concentration (10ppm).

[0039] Table 1 BET and NH3 adsorption properties of different resin samples

[0040] sample BET(m2 / g) Initial efficiency (%) Mass adsorption ratio (mg / g) Pure resin 12 87.8 1.83％ Example 1 1201 96.4 4.32％ Example 2 1244 95.2 3.81％ Example 3 1236 92.8 3.36％

[0041] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a ZIF-8 modified ammonia removal resin, characterized in that: The following steps are included: S1: Precursor preparation, First, weigh 5-10g of zinc salt, dissolve it in 50-100mL of organic solvent under magnetic stirring to prepare a metal salt solution A with a concentration of 0.5M, then weigh 10-20g of adsorption resin, and evenly disperse it in the above metal salt solution A under magnetic stirring to obtain dispersion B, and finally place it at room temperature for 2-12h to allow zinc ions to exchange with cations in the resin; S2: Preparation of ZIF-8 modified resin, Weigh 5-40g of 2-methylimidazole, dissolve it in 50-100mL of an organic solvent under magnetic stirring to prepare an organic ligand solution C with a concentration of 1-8M, uniformly mix the solution C and the dispersion B at a ratio of 1:1 under magnetic stirring, add 0.5-1g of a nucleating agent, react at 40-120°C for 2-12h, and obtain a ZIF-8 modified resin after suction filtration; S3: Drying treatment, The ZIF-8 modified resin prepared in step S2 is treated in a constant temperature drying oven at 30-120° C. for 1-24 hours to obtain a ZIF-8 modified ammonia removal special resin having a water content of 30-50%.

2. The method for preparing a ZIF-8 modified ammonia-removing resin according to claim 1, wherein: The zinc salt in step S1 is one of zinc sulfate, zinc chloride, zinc nitrate and zinc acetate.

3. The method for preparing a ZIF-8 modified ammonia-removing resin according to claim 1, wherein: The organic solvent in step S1 and the organic solvent in step S2 are both one of methanol, ethanol, DMAc, DMF and deionized water.

4. The method for preparing a ZIF-8 modified ammonia-removing resin according to claim 1, wherein: The nucleating agent in step S2 is one of hexadecyltrimethylammonium bromide, ammonium dodecylbenzenesulfonate, polyethylene and pyrrolidone.

Images