A modified molecular sieve and its preparation and application methods

Abstract

The purpose of this invention is to improve the adsorption properties of molecular sieves and chitosan, and to provide a modified molecular sieve and its preparation and use methods. This modified molecular sieve is obtained by inorganic modification, chitosan loading, and organic modification of a molecular sieve, and the specific surface area of ​​the molecular sieve is 621–846 m². 2 / g, pore size greater than 2nm. This invention, based on molecular theory, crosslinks organic solvents with functional groups in chitosan molecules to generate substances with stronger complexing properties. These substances interact with the active sites of molecular sieves, exhibiting stronger adsorption capacity and can be applied in fields such as heavy metal ion adsorption and organic matter adsorption. Furthermore, the preparation process is simple, the raw materials are widely available, and the prepared adsorbent has strong acid and alkali resistance, antioxidant capacity, and is convenient to use.

Description

Technical Field

[0001] This invention belongs to the field of adsorbent product preparation technology, and specifically relates to a modified molecular sieve and its preparation and use methods. Background Technology

[0002] Molecular sieve materials, due to their unique structural properties, play an important role in petrochemical, environmental protection, life sciences, and medical fields, possessing broad research potential and application prospects. As an excellent adsorbent, molecular sieves are characterized by their strong adsorption capacity for polar small molecules and selective adsorption capacity for molecules with different critical diameters, shapes, polarities, and degrees of unsaturation. However, when molecular sieves are used as adsorbents in organic compounds, the type and number of cations in the molecular sieve structure affect their activity; fewer active sites result in weaker activation ability and weaker binding performance with organic matter.

[0003] Chitosan is a substance produced from chitin through refining. It is insoluble in water but soluble in dilute acids. Its chemical structure is a cationic, alkaline polysaccharide polymer with unique physicochemical properties and bioactivation functions. Recent reports, both domestically and internationally, have mainly focused on its adsorption and flocculation applications. Within the chitin molecule, the interaction of internal and external hydrogen bonds forms an ordered macromolecular structure, resulting in poor solubility, which limits its applications in many areas.

[0004] However, there is currently limited research on the modification of chitosan molecular sieves using organic materials, and further research is needed to improve the adsorption properties of both and broaden their applications. Summary of the Invention

[0005] The purpose of this invention is to improve the adsorption performance of molecular sieves, providing a modified molecular sieve and its preparation and application methods. Based on molecular theory, this invention crosslinks organic solvents with the functional groups in chitosan molecules, generating substances with stronger complexing properties. These substances interact with the active sites of the molecular sieve, exhibiting stronger adsorption capacity and can be applied in fields such as heavy metal ion adsorption and organic matter adsorption. Furthermore, the preparation process is simple, the raw materials are widely available, and the prepared adsorbent has strong acid and alkali resistance, antioxidant capacity, and is convenient to use.

[0006] The technical solution of the present invention is as follows:

[0007] A modified molecular sieve is obtained by inorganic modification, chitosan loading, and organic modification of the molecular sieve.

[0008] Furthermore, the specific surface area of ​​the aforementioned molecular sieve is 621–846 m². 2 / g, pore size greater than 2nm.

[0009] This invention also provides a method for preparing the above-mentioned modified molecular sieve, specifically including the following steps:

[0010] 1) Inorganic modification

[0011] Take an inorganic modifier and prepare a two-component modifier solution with a mass concentration of 2-5%. Then mix it with a molecular sieve, stir for 1-2 hours, filter, wash the precipitate until the washing solution is neutral, and dry to obtain inorganic modified molecular sieve solid.

[0012] 2) Supported chitosan

[0013] Weigh the inorganic modified molecular sieve solid from step 1), mix it thoroughly with the chitosan solution, then add an alkaline reagent dropwise while stirring until a precipitate appears, stir until no more precipitate is produced, centrifuge, filter, wash the precipitate until the washing solution is neutral, and dry to obtain chitosan-supported molecular sieve solid.

[0014] 3) Organic modification

[0015] The chitosan-supported molecular sieve solid from step 2) is thoroughly mixed with the organic modifier solution, and then reacted in a constant temperature water bath. After the reaction is complete, the mixture is filtered and separated. The precipitate is washed until the washing solution is neutral and then dried to obtain the modified molecular sieve.

[0016] Furthermore, in step 1), the inorganic modifier is any two of sodium chloride, lithium chloride, copper chloride, and magnesium chloride; and the mass ratio of the two modifiers is 0.2 to 8:1.

[0017] Furthermore, in step 1), the liquid-to-solid ratio of the two-component modifier solution to the molecular sieve is 2-100 ml: 1 g.

[0018] Furthermore, in step 2), the chitosan solution uses an acetic acid solution with a mass concentration of 0.8-1.2% as a solvent, and the chitosan mass concentration is 1-15%.

[0019] Furthermore, in step 2), the alkaline reagent used is a sodium hydroxide solution with a concentration of 0.6–1.4 mol / L.

[0020] Furthermore, in step 2), the liquid-to-solid ratio of the chitosan solution to the inorganic modified molecular sieve is 10-200 ml: 1 g.

[0021] Furthermore, in step 3), the organic modifier is hexadecylpyridine bromide or N,N-dimethylaminoethyl methacrylate; the mass concentration of the organic modifier solution is 30-60 ppm, and the liquid-to-solid ratio of the organic modifier solution to the chitosan-supported molecular sieve is 10-250 ml: 1 g.

[0022] Furthermore, in step 3), the water bath reaction temperature is 30–70°C, and the reaction time is 12–48 h.

[0023] Furthermore, the present invention also provides a method for using the above-mentioned modified molecular sieve as a heavy metal ion adsorbent and an organic matter adsorbent.

[0024] Furthermore, when using the modified molecular sieve as an organic adsorbent in wastewater containing organic dyes, the dosage of the modified molecular sieve is 10–100 g / L, the concentration of the dye solution is 50–200 mg / L, the pH of the solution is 4–11, and the adsorption time is 1–4 h.

[0025] Furthermore, when the modified molecular sieve described above is used as a heavy metal ion adsorbent in the adsorption of nickel-containing wastewater, the dosage of the modified molecular sieve is 10–50 g / L, the nickel ion concentration is 20–100 mg / L, the solution pH is 7–12, and the adsorption time is 0.5–4 h.

[0026] In this invention, to improve the adsorption capacity of the molecular sieve, an inorganic modifier is added to activate its active sites, causing ion replacement. Specific atoms are introduced into the molecular sieve framework, altering its acidity and pore size, thereby changing its redox properties, catalytic activity, or other functions, thus improving adsorption performance. Furthermore, the molecular sieve surface has high acid strength, which can disrupt the hydrogen bond interactions in chitosan molecules, creating both acidic and basic centers. During adsorption, these basic and acidic sites react together, synergistically enhancing the stability and adsorption capacity of the molecular sieve. In addition, the regular arrangement of hydroxyl and amino groups in the chitosan structure limits its applications. Modification with organic matter disrupts the chitosan's group structure through specific functional groups, causing chain scission and yielding a soluble polymer, enhancing its chelating ability and making it easier to adsorb heavy metal ions. Moreover, the disruption of hydrogen bonds between chitosan molecules alters its crystalline structure, increasing solubility, and making the hydroxyl groups in the chitosan molecular chain more readily react with organic substances. After organic modification, the cross-linking between chitosan and molecular sieves becomes more stable, increasing not only the mechanical strength of chitosan but also the stability of the molecular sieves. After modification, the molecular sieve's structural framework contains inorganic metal ions and organic functional groups. The surface free energy of the adsorbed substance is greater than that of the adsorbent, leading to the breaking of chemical bonds and electron transfer. The adsorbate and adsorbent are then bound together by chemical bonds, or the adsorption process is achieved through the adsorption forces between the adsorbate and the adsorbed substance, such as van der Waals forces and electrostatic forces. Modified molecular sieves expand their application range, enabling the adsorption of inorganic heavy metal ions and organic matter.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] 1. This invention prepares a modified molecular sieve. The molecular sieve uses iron tailings as raw material, and the process is simple and the raw material is inexpensive and widely available.

[0029] 2. The present invention obtains a modified molecular sieve by treating the molecular sieve with a modifier and chitosan. The modified molecular sieve is applied to the adsorption of solutions containing nickel heavy metal ions and solutions containing Congo red organic wastewater, and the effect is better. Therefore, the modified molecular sieve can be used for the adsorption of heavy metal ions and organic matter, and the adsorption effect is strong.

[0030] 3. This invention utilizes modified molecular sieves to overcome the limitations of traditional molecular sieves in adsorbing heavy metal ions and organic matter. The prepared adsorbent has strong acid and alkali resistance, strong antioxidant capacity, and is easy to use. Attached Figure Description

[0031] Figure 1 Electron micrograph of the modified molecular sieve prepared in Example 1. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0033] The molecular sieve used in this invention has a specific surface area of ​​621–846 m². 2 / g, pore size greater than 2nm; prepared according to the technical solution in patent application No. 2023114065975.

[0034] The molecular weight of chitosan is 1526.4539;

[0035] The CAS number for hexadecylpyridine bromide is 140-72-7;

[0036] N,N-dimethylaminoethyl methacrylate is sourced from Shandong Yinglang Chemical Co., Ltd.

[0037] Example 1

[0038] A modified molecular sieve is obtained by inorganic modification, chitosan loading, and organic modification of the molecular sieve. Its preparation method includes the following steps:

[0039] (1) Weigh copper chloride and magnesium chloride (mass ratio of 3:1), prepare 100ml of 4% two-component modifier solution, add 4g of molecular sieve to the two-component modifier solution, adjust the stirrer speed to 1200rpm, stir for 2h, filter, wash with distilled water until pH is about 7.0, dry at 70±2℃ to obtain inorganic modified molecular sieve.

[0040] (2) Prepare a 1% acetic acid solution, add chitosan to make 100ml of a 2% chitosan solution, add 2g of modified molecular sieve, add 1mol / L sodium hydroxide solution dropwise in 16ml, a precipitate will appear, stir until no more precipitate will be formed, put it in a centrifuge and set the centrifugation speed to 2800rpm for 1.5h, filter, wash with distilled water until the pH is about 7.0, dry at 70±2℃ to obtain solid chitosan-supported molecular sieve.

[0041] (3) Prepare a 50 ppm solution of hexadecylpyridine bromide. Take 100 ml of the hexadecylpyridine bromide solution, add 1 g of chitosan-supported molecular sieve, place it in an ultrasonic device, set the ultrasonic temperature to 35±2℃ and the ultrasonic time to 30 min, then transfer it to a water bath reaction apparatus, set the water bath temperature to 60±2℃ and the water bath time to 24 h, filter, wash with distilled water until the pH is about 7.0, and dry at 50±2℃ to obtain the modified molecular sieve. See [link to modified molecular sieve description]. Figure 1 electron micrograph

[0042] The method of using the above-mentioned modified molecular sieve is as follows:

[0043] 1) Weigh 20g of modified molecular sieve and place it in 1L of Congo red solution with a concentration of 100mg / L. Adjust the pH to about 7.0 with acid and base solution. Place the solution on a shaker and shake for 2h. Let it stand for 2h. Take the clear liquid in the upper layer and determine that its adsorption rate of Congo red is 86.79%.

[0044] 2) Weigh 10g of modified molecular sieve and place it in 1L of nickel ion solution with a concentration of 100mg / L. Adjust the pH to about 8.0 with acid and base solution. Place the solution on a shaker and shake for 2h. Let it stand for 2h. Take the clear liquid in the upper layer and determine that its adsorption rate of nickel ions is 79.58%.

[0045] The remaining embodiments follow the same methods as the comparative examples and Example 1, except for the different experimental conditions. The experimental conditions for the embodiments and comparative examples are shown in Table 1.

[0046] Application examples

[0047] 1) The adsorption conditions and application effects of using modified molecular sieves to adsorb Congo red solution are shown in Table 2.

[0048] 2) The adsorption conditions and application effects of modified molecular sieves for adsorbing nickel-containing heavy metal ion solutions are shown in Table 3.

[0049] Note: Inorganic modifiers sodium chloride, lithium chloride, copper chloride, and magnesium chloride are designated as 1, 2, 3, and 4, respectively; organic modifiers hexadecylpyridine bromide and N,N-dimethylaminoethyl methacrylate are designated as A and B, respectively.

[0050] Table 1. Experimental conditions for examples and comparative examples

[0051]

[0052]

[0053] Table 2. Adsorption conditions and application effects of the examples and comparative examples.

[0054]

[0055] Table 3. Adsorption conditions and application effects of the examples and comparative examples.

[0056]

Claims

1. A modified molecular sieve characterized by, The modified molecular sieve is obtained by inorganic modification, loading chitosan and organic modification of the molecular sieve; The specific surface area of the molecular sieve is 621-846 m 2 / g, and the pore size is greater than 2 nm. In the inorganic modification, the inorganic modifier is any two of sodium chloride, lithium chloride, copper chloride and magnesium chloride; and in the organic modification, the modifier is poly (N,N-dimethylaminoethyl methacrylate).

2. The method of making a modified molecular sieve of claim 1, characterized by, The method comprises the following steps: 1) Inorganic modification An inorganic modifier is prepared into a two-component modifier solution with a mass concentration of 2-5%, and then mixed with the molecular sieve, stirred for 1-2 h, filtered, washed until the washing liquid is neutral, and dried to obtain a modified molecular sieve solid; In the step 1), the inorganic modifier is any two of sodium chloride, lithium chloride, copper chloride and magnesium chloride; and the mass ratio of the two modifiers is 0.2-8:1; The liquid-solid ratio of the two-component modifier solution to the molecular sieve is 2-100 ml:1 g; 2) Loading chitosan The modified molecular sieve solid in the step 1) is mixed with a chitosan solution, and then an alkaline reagent is added dropwise under stirring until precipitation occurs, and then stirring is continued until no more precipitation occurs, centrifugal separation, filtration, washing until the washing liquid is neutral, and drying to obtain a chitosan-loaded molecular sieve solid; 3) Organic modification The chitosan-loaded molecular sieve solid in the step 2) is mixed with an organic modifier solution, and then reacted in a constant-temperature water bath, filtered and separated after the reaction, washed until the washing liquid is neutral, and dried to obtain a modified molecular sieve; The organic modifier is poly (N,N-dimethylaminoethyl methacrylate), the mass concentration of the organic modifier solution is 30-60 ppm, and the liquid-solid ratio of the organic modifier solution to the chitosan-loaded molecular sieve is 10-250 ml:1 g.

3. The method for preparing a modified molecular sieve according to claim 2, characterized in that, In the step 2), the chitosan solution is prepared with acetic acid as the solvent, the mass concentration of the chitosan solution is 0.8-1.2%, and the mass concentration of the chitosan is 1-15%; The alkaline reagent used is a sodium hydroxide solution with a concentration of 0.6-1.4 mol / L; The liquid-solid ratio of the chitosan solution to the modified molecular sieve is 10-200 ml:1 g.

4. The method of making a modified molecular sieve of claim 2, wherein, In the step 3), the water bath reaction temperature is 30-70°C, and the reaction time is 12-48 h.

5. The method of using the modified molecular sieve of claim 1, characterized by, The modified molecular sieve is used as a heavy metal ion adsorbent and an organic matter adsorbent; As an organic matter adsorbent, the modified molecular sieve is used in organic dye-containing wastewater, the dosage of the modified molecular sieve is 10-100 g / L, the concentration of the dye solution is 50-200 mg / L, the solution pH is 4-11, and the adsorption time is 1-4 h; As a heavy metal ion adsorbent, the modified molecular sieve is used in the adsorption of nickel ion-containing wastewater, the dosage of the modified molecular sieve is 10-50 g / L, the concentration of the nickel ions is 20-100 mg / L, the solution pH is 7-12, and the adsorption time is 0.5-4 h.

Images