Biomass-iron-based organic framework composite material, and preparation method therefor and use thereof

Abstract

The present invention belongs to the technical field of the preparation and use of environmental materials. Disclosed are a biomass-iron-based organic framework composite material, and a preparation method therefor and the use thereof. The method comprises: adding chitosan, an iron-based organic framework, i.e. MIL-88(B), and a cross-linking agent into an acetic acid solution, mixing same until uniform, then heating the mixture in a water bath, and adding same into a mixed solution dropwise for reaction, so as to obtain a biomass-iron-based organic framework composite material. The phosphate adsorption capacity of the biomass-iron-based organic framework composite material prepared in the present invention can reach 1.1 mmol / g, the adsorption capacity is higher than that of a pure iron-based organic framework material and a single biomass-based material, and the loss of the iron-based organic framework material is less than 1% when same is close to the optimal adsorption pH condition.

Description

A biomass-based iron-based organic framework composite material and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of environmental material preparation and application, and specifically relates to a biomass-based-iron-based organic framework composite material and a preparation method and application thereof. Background Art

[0002] Phosphorus is one of the main elements causing eutrophication in water bodies. It can accelerate the growth of phytoplankton, leading to oxygen depletion and the death of fish and aquatic life. Electroplating is an essential industry for both industry and life. However, due to the large amount of phosphorus-containing wastewater discharged during the process, the electroplating industry has become one of the most dangerous chemical-intensive industries in the world. The production process uses a variety of phosphorus-containing agents, such as phosphoric acid, chelating agents, and reducing agents, generating large amounts of phosphorus-containing wastewater.

[0003] Treatment methods for inorganic phosphorus wastewater primarily include chemical and physical methods, including ion exchange, membrane separation, and adsorption. Ion exchange lacks selectivity for phosphorus and exhibits poor resistance to interference in complex aquatic environments. Membrane separation offers high selectivity for pollutants, but the membrane components require frequent replacement. Compared to these methods, adsorption offers lower preparation costs and fewer steps. It is suitable for enriching and recovering low-concentration phosphorus using solid functional groups, offering advantages such as simplicity, cost-effectiveness, and low carbon footprint.

[0004] Domestic and international literature research indicates that iron-based organic frameworks (IFs) are novel porous coordination polymer materials composed of iron and organic ligands assembled through coordination. They possess a unique structure, large specific surface area, and a uniform, controllable, and diverse pore structure. They are widely used in the adsorption field and have demonstrated strong phosphorus absorption and resistance to interference. Despite their excellent performance in phosphorus absorption, the use of fine particles in wastewater treatment can result in elemental loss and poor post-treatment recovery and reuse, leading to higher operating costs. Therefore, finding a suitable matrix to retain the adsorbent and facilitate its recycling and recovery is crucial.

[0005] Chinese patent number CN202210404779.8 discloses a preparation method and application of MIL-100 (Fe) / cellulose porous composite beads. The iron-based organic framework is added to the cellulose solution, stirred evenly, and then immersed in a metal ion solution to obtain a composite bead hydrogel. The hydrogel has the advantages of good mechanical properties, high porosity, and high adsorption efficiency. However, the preparation process does not accurately control whether the iron-based organic framework has a leakage risk.

[0006] A search revealed no patents or published literature demonstrating phosphate adsorption using biomass-based iron-based organic framework composites. Therefore, there is an urgent need to develop a method that effectively mitigates the loss of iron-based organic frameworks and ensures that the loaded materials maintain a high adsorption capacity during continuous operation, thus meeting practical application requirements. Summary of the Invention

[0007] In view of the above-mentioned problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing a biomass-based-iron-based organic framework composite material, which has the advantages of simple preparation process and easy industrial production. Another technical problem to be solved by the present invention is to provide a biomass-based-iron-based organic framework composite material prepared by the above-mentioned method. The rich functional groups in the biomass base have an electrostatic attraction effect on phosphate, which enhances the adsorption and removal ability of the iron-based organic framework material for phosphate. Another technical problem to be solved by the present invention is to provide the application of the above-mentioned biomass-based-iron-based organic framework composite material as an adsorbent in the adsorption of phosphate pollutants in water bodies.

[0008] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0009] A method for preparing a biomass-based-iron-based organic framework composite material comprises adding chitosan, an iron-based organic framework MIL-88(B) and a cross-linking agent to an acetic acid solution, mixing them evenly and then heating them in a water bath, and then dropping the mixed solution into the solution and reacting to obtain the biomass-based-iron-based organic framework composite material.

[0010] Preferably, the g / g / mL ratio of the chitosan, the iron-based organic framework MIL-88(B) and the cross-linking agent is 0.6:1:0.154.

[0011] Preferably, the cross-linking agent is epichlorohydrin.

[0012] Preferably, the mixed solution is a mixed solution of sodium hydroxide, sodium sulfate, anhydrous ethanol and water, wherein the g / g / mL / mL ratio of sodium hydroxide, sodium sulfate, anhydrous ethanol and water is 16:12:2:300.

[0013] The method for preparing the biomass-based-iron-based organic framework composite material specifically comprises the following steps:

[0014] 1) Chitosan, iron-based organic framework MIL-88(B), and a crosslinker were weighed separately and added to an acetic acid solution. The mixture was evenly mixed and then heated in a water bath at 60°C for crosslinking for 2 h to obtain a mixture.

[0015] 2) adding a mixed solution containing sodium hydroxide, sodium sulfate, anhydrous ethanol and water dropwise into the mixed material obtained in step 1) to obtain hydrogel beads;

[0016] 3) The obtained hydrogel beads are placed in a diluted cross-linking agent to enhance the mechanical strength, washed and dried at room temperature to prepare a biomass-based-iron-based organic framework composite material.

[0017] The method for preparing the biomass-based-iron-based organic framework composite material prepares the biomass-based-iron-based organic framework composite material.

[0018] The biomass-based-iron-based organic framework composite material is used as an adsorbent in adsorbing phosphate pollutants in water bodies.

[0019] The application described above has an adsorption process as follows: adding the biomass-based iron-based organic framework composite material to a phosphate-containing water body, and performing oscillation adsorption at room temperature to adsorb the phosphate.

[0020] In the application, the phosphate adsorption time is 24 hours, and the adsorbable phosphate concentration is: 0.2~1.0 mg / L.

[0021] In the application, the adsorbed biomass-based-iron-based organic framework composite material is fully shaken and eluted in 100 mL of a mixed solution at 150 r / min for 12 hours, and then adsorbed again; wherein the mixed solution is a mixed solution of 0.1 mol / L sodium hydroxide and 5 mol / L sodium nitrate.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention utilizes the abundant functional groups in the biomass matrix to have an electrostatic attraction effect on phosphate, thereby enhancing the adsorption and removal ability of the iron-based organic framework material for phosphate in practical applications;

[0024] (2) The phosphate adsorption capacity of the biomass-based iron-based organic framework composite material prepared by the present invention can reach 1.1 mmol / g, which is higher than that of pure iron-based organic framework materials and single biomass-based materials. When the optimal adsorption pH condition is near, the loss of the iron-based organic framework material is less than 1%;

[0025] (3) The regeneration method of the biomass-based-iron-based organic framework composite material of the present invention is simple and easy to implement, saving the cost of wastewater treatment. After 6 adsorption-regeneration cycles, the adsorption efficiency can still be higher than 80%, and the regeneration efficiency is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 shows SEM images of MIL-88(B), chitosan, and MIL-88(B) / chitosan. (a) and (d) are MIL-88(B) at 10.0 μm and 1.00 μm, respectively; (b) and (e) are chitosan at 500 μm and 5.00 μm, respectively; and (c) and (f) are MIL-88(B) / chitosan at 500 μm and 5.00 μm, respectively.

[0027] Figure 2 is the FTIR images of MIL-88(B), chitosan, and MIL-88(B) / chitosan;

[0028] FIG3 is an XRD pattern of MIL-88(B), chitosan, and MIL-88(B) / chitosan;

[0029] FIG4 is a graph showing the removal effects of MIL-88(B), chitosan, and MIL-88(B) / chitosan on phosphate at different concentrations;

[0030] FIG5 is a graph showing the adsorption performance of phosphate and the loss of iron-based organic frameworks by MIL-88(B), chitosan, and MIL-88(B) / chitosan under different pH conditions;

[0031] Figure 6 shows the effect of MIL-88(B) / chitosan cyclic adsorption-desorption of a certain electroplating tail water with an initial phosphate concentration of 0.85 mg / L;

[0032] Figure 7 shows the adsorption effects of phosphate on MIL-88(B), chitosan, and MIL-88(B) / chitosan hydrogel at different adsorption times. DETAILED DESCRIPTION

[0033] Below in conjunction with specific embodiment, further illustrate the present invention, embodiment is implemented under the premise of technical solution of the present invention, should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the invention. In the following examples, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art. In the embodiment, those not indicating specific conditions are carried out according to the conditions of normal conditions or manufacturer's advice. Reagents used or instruments not indicating manufacturers are conventional products that can be obtained by commercial purchase.

[0034] The performance testing method adopted in the present invention is as follows:

[0035] 1. The test method for the adsorption and desorption performance of phosphate is: ammonium molybdate spectrophotometry (GB / T 11893-1989).

[0036] 2. The test method for the loss of iron-based organic framework is: flame atomic absorption spectrophotometry (GB / T 11911-1989). Example

[0037] 1 g of powdered MIL-88(B), 0.6 g of chitosan, and 0.154 mL of epichlorohydrin were added to 20 mL of 2% (v / v) acetic acid solution, respectively, and cross-linked at 60°C for 2 h. A 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of anhydrous ethanol was then added dropwise with a syringe to fully cross-link and form hydrogel beads. The beads were then cross-linked in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength. After washing and drying at room temperature, 6 g of MIL-88(B) / chitosan hydrogel was obtained, namely, a biomass-based-iron-based organic framework composite material.

[0038] As shown in the SEM and XRD images of Figures 1 and 3, there are many large pores on the surface of the MIL-88(B) / chitosan hydrogel prepared by the present invention. By further magnification, it can be found that these pores carry many small pores. MIL-88(B) maintains the same size and orderly shape. The appearance of iron element indicates the introduction of MIL-88(B), and the increase of N element indicates the appearance of chitosan. As shown in the FTIR image of Figure 2, the 1650 cm -1 There is a peak at 3354 cm -1 The strong peak nearby is related to the extended vibration of NH, which can be attributed to the effect of protonated amino groups.

[0039] Comparative Example 1

[0040] 4.32 g of ferric chloride hexahydrate and 2.66 g of terephthalic acid were added to 100 mL of N,N-dimethylformamide and completely dissolved. The mixture was kept at 150°C in an autoclave for 12 h, washed alternately with deionized water and methanol several times, and dried to obtain 2.51 g of pure iron-based organic framework material MIL-88(B).

[0041] Comparative Example 2

[0042] 0.6 g of chitosan and 0.154 mL of epichlorohydrin were added to 20 mL of 2% (v / v) acetic acid solution, respectively, and cross-linked at 60°C for 2 h. A 300 mL mixed solution containing 16 g of sodium hydroxide, 12 g of sodium sulfate, and 2 mL of anhydrous ethanol was added dropwise with a syringe to fully cross-link to form hydrogel beads. The beads were then cross-linked in 100 mL of distilled water containing 0.5 mL of epichlorohydrin for 2 h to enhance the mechanical strength. After washing, the beads were dried at room temperature to obtain 5.0 g of single biomass-based chitosan. Example

[0043] The MIL-88(B) / chitosan hydrogel prepared in Example 1, the MIL-88(B) prepared in Comparative Example 1, and the chitosan prepared in Comparative Example 2 were tested for their phosphate adsorption properties.

[0044] 50 mL of sodium dihydrogen phosphate solution with concentrations of 0.5, 1, 2, 4, and 8 mmol / L was prepared, and the pH value was adjusted to 7.0. 0.5 g of the adsorbent to be tested was added, and the mixture was shaken at room temperature (25°C) for 24 h. The phosphate concentration of the solution was determined by ammonium molybdate spectrophotometry (GB / T 11893-1989). The results are shown in Table 1.

[0045] Table 1 Maximum adsorption capacity of MIL-88(B), chitosan, and MIL-88(B) / chitosan

[0046]

[0047] As shown in Table 1, the maximum adsorption capacity of MIL-88(B) / chitosan at room temperature is 1.10 mmol / g, which is better than that of pure iron-based organic framework material MIL-88(B) and single biomass-based material chitosan.

[0048] As shown in Figure 4 , the adsorption process of phosphate by MIL-88(B) / chitosan hydrogel was more consistent with the Friedrich isotherm than the Langmuir isotherm, which indicated that MIL-88(B) / chitosan removed phosphate by multilayer adsorption on the heterogeneous surface. Example

[0049] The MIL-88(B) / chitosan hydrogel prepared in Example 1, the MIL-88(B) prepared in Comparative Example 1, and the chitosan prepared in Comparative Example 2 were tested for their phosphate adsorption properties under different pH conditions.

[0050] 50 mL of 1 mmol / L sodium dihydrogen phosphate solution was prepared, and the pH values ​​of the solution were adjusted to 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0 with sodium hydroxide and hydrochloric acid, respectively. 0.5 g of the MIL-88(B) / chitosan hydrogel prepared in Example 1 was added, and the mixture was shaken at room temperature for 24 h. The phosphate concentration of the solution was determined by ammonium molybdate spectrophotometry (GB / T 11893-1989). The results are shown in Figure 5. The phosphate adsorption efficiency of MIL-88(B) / chitosan exceeded 80% at a pH of 4-8, the suitable pH range was 6-8, and the adsorption amount was the largest at pH 7, indicating that MIL-88(B) / chitosan can adapt to a wider range of acid and base conditions.

[0051] The MIL-88(B) / chitosan hydrogel prepared in Example 1 was used to test the loss of its iron-based organic framework. 1 mmol / L sodium dihydrogen phosphate solution was prepared at pH 4, 5, 6, 7, 8, 9, and 10, and 0.5 g of the MIL-88(B) / chitosan hydrogel prepared in Example 1 was added. The solution was shaken at room temperature for 24 hours, and the iron ion concentration of the solution was measured using flame atomic absorption spectrophotometry (GB / T 11911-1989). The results, shown in Figure 5, show that iron loss was consistently less than 1%, with loss less than 0.2% near the optimal pH of 6-8, demonstrating that biomass-based materials can help reduce loss and leakage of iron-based organic frameworks. Example

[0052] The MIL-88(B) / chitosan hydrogel prepared in Example 1 was subjected to adsorption of electroplating tail water with an initial phosphate concentration of 0.85 mg / L, followed by desorption and a cyclic operation.

[0053] 0.5 g of the MIL-88(B) / chitosan hydrogel prepared in Example 1 was added to 50 mL of wastewater and shaken at room temperature for 24 hours. A 100 mL mixture of 5 mol / L sodium nitrate and 0.1 mol / L sodium hydroxide was prepared as the eluent, to which 0.5 g of the phosphate-adsorbed MIL-88(B) / chitosan hydrogel beads were added. The mixture was shaken at room temperature for 12 hours to obtain the desorbed MIL-88(B) / chitosan hydrogel. This cycle was repeated six times, and the phosphate concentrations in the effluent and eluate were measured using ammonium molybdate spectrophotometry (GB / T 11893-1989). The results are shown in Figure 6 and Table 2. After six cycles, the phosphate concentration in the electroplating tail water remained consistently below 0.2 mg / L, with an adsorption efficiency consistently exceeding 80% and a recovery efficiency of at least 97%, demonstrating the stability and efficiency of this desorption method.

[0054] Table 2 Adsorption and desorption efficiencies of MIL-88(B) / chitosan cyclic adsorption-desorption of electroplating tail water with an initial phosphate concentration of 0.85 mg / L

[0055] Cycle number Adsorption efficiency (%) Desorption efficiency (%) 190.16-289.7099.48388.2998.43486.4297.88585.3698.78683.4997.81 Example

[0056] The MIL-88(B) / chitosan hydrogel prepared in Example 1, the MIL-88(B) prepared in Comparative Example 1, and the chitosan prepared in Comparative Example 2 were tested for the adsorption effect of phosphate at different adsorption times.

[0057] Prepare 200 mL of 1 mmol / L sodium dihydrogen phosphate solution and adjust the pH to 7.0. Add 0.5 g of the adsorbent to be tested. Sampling was performed at 0, 15, 30, 60, 90, 120, 180, 240, 360, and 1440 min, and the phosphate concentration of the solution was determined using the ammonium molybdate spectrophotometric method (GB / T 11893-1989). The results are shown in Figure 7. The pseudo-second-order kinetic model is more suitable for the process of phosphate adsorption by the MIL-88(B) / chitosan hydrogel prepared by the present invention than the pseudo-first-order kinetic model. The MIL-88(B) / chitosan hydrogel prepared by the present invention inherits the high efficiency of phosphate adsorption by the single iron-based organic framework MIL-88(B). In just 180 minutes, more than 90% of the phosphate in the solution is adsorbed. Its adsorption efficiency is not greatly affected by the low phosphate adsorption rate of the single biomass-based chitosan, which proves that MIL-88(B) / chitosan adsorbs phosphate faster and has higher adsorption efficiency.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a biomass-based-iron-based organic framework composite material, characterized in that: Chitosan, iron-based organic framework MIL-88 (B) and a cross-linking agent are added to an acetic acid solution, mixed evenly and then heated in a water bath, and then the mixed solution is dropped into the solution and reacted to obtain a biomass-based iron-based organic framework composite material.

2. The method for preparing the biomass-based-iron-based organic framework composite material according to claim 1, characterized in that: The g / g / mL ratio of the chitosan, the iron-based organic framework MIL-88 (B) and the cross-linking agent is 0.6:1:0.

154.

3. The method for preparing the biomass-based-iron-based organic framework composite material according to claim 1, characterized in that: The cross-linking agent is epichlorohydrin.

4. The method for preparing the biomass-based-iron-based organic framework composite material according to claim 1, characterized in that: The mixed solution is a mixed solution of sodium hydroxide, sodium sulfate, anhydrous ethanol and water, wherein the g / g / mL / mL of sodium hydroxide, sodium sulfate, anhydrous ethanol and water is 16:12:2:

300.

5. The method for preparing the biomass-based-iron-based organic framework composite material according to claim 1, characterized in that: The specific steps include: 1) Chitosan, iron-based organic framework MIL-88(B) and cross-linking agent were weighed separately and added into acetic acid solution, mixed evenly and heated in a water bath at 60°C for cross-linking for 2 h to obtain a mixed material; 2) dropping a mixed solution containing sodium hydroxide, sodium sulfate, anhydrous ethanol and water into the mixed material obtained in step 1) to obtain hydrogel beads; 3) placing the obtained hydrogel beads into a diluted cross-linking agent to enhance the mechanical strength, washing and drying at room temperature to obtain a biomass-based-iron-based organic framework composite material.

6. The method for preparing the biomass-based-iron-based organic framework composite material according to any one of claims 1 to 5, wherein the biomass-based-iron-based organic framework composite material is prepared.

7. Use of the biomass-based-iron-based organic framework composite material according to claim 6 as an adsorbent in adsorbing phosphate pollutants in water bodies.

8. The use according to claim 7, characterized in that: The adsorption process is as follows: adding the biomass-based-iron-based organic framework composite material into the phosphate-containing water body, and oscillating and adsorbing at room temperature to adsorb the phosphate.

9. The use according to claim 8, characterized in that: The phosphate adsorption time is 24 h, and the adsorbable phosphate concentration is: 0.2 ~1.0 mg / L.

10. The use according to claim 7, characterized in that: The adsorbed biomass-based-iron-based organic framework composite material was fully shaken and eluted in 100 mL of mixed solution at 150 r / min for 12 h, and then adsorbed again; wherein the mixed solution was a mixed solution of 0.1 mol / L sodium hydroxide and 5 mol / L sodium nitrate.

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