Nitrogen-doped calcium-aluminum composite material and preparation method thereof

Abstract

The invention discloses a preparation method of a nitrogen-doped calcium-aluminum composite material. The preparation method comprises the following steps: step 1, preparing a NaAlO2 solution; step 2, adding a NaAlO2 solution into the Ca (OH) 2 emulsion to obtain a reaction solution; step 3, doping a nitrogen source, gradually dropwise adding an ammonium bicarbonate or ammonium carbonate solution into the reaction solution, and stirring at room temperature after dropwise adding is completed; 4, after the reaction in the step 3 is completed, filtering reaction liquid, drying a filter cake, and preserving heat; and step 5, roasting the product obtained in the step 4 to obtain the nitrogen-doped calcium-aluminum composite material. The nitrogen-doped calcium-aluminum composite material obtained by the preparation method of the nitrogen-doped calcium-aluminum composite material is used for efficiently removing anions in industrial discharged water, so that the concentration of Cl <-> and other ions in the industrial discharged water reaches the standard, and the recycling of industrial sewage is realized.

Description

Technical Field

[0001] This invention belongs to the field of safe, environmentally friendly, energy-saving and water-saving materials technology, specifically relating to a method for preparing nitrogen-doped calcium-aluminum composite materials, and also relating to the nitrogen-doped calcium-aluminum composite materials prepared by this method. Background Technology

[0004] To achieve the reuse of industrial water, the chloride ion concentration (Cl) must be reduced. - Concentration. High chloride ion levels can harm drinking water, irrigation, equipment, and the ecological environment. When chloride ion concentrations in drinking water exceed 250 mg / L (GB5749-2006), the water tastes bitter or salty, and in severe cases, can cause poisoning. When chloride ion concentrations in irrigation water exceed 350 mg / L (HJ332-2006), it can seriously affect crop growth. Limiting the concentrations of chloride and sulfate ions and implementing zero-emission policies are inevitable future trends. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing nitrogen-doped calcium-aluminum composite materials for efficiently removing anions from industrial wastewater, thereby reducing the Cl content in industrial wastewater. - The plasma concentration meets the standards, enabling the reuse of industrial water.

[0006] To achieve the above objectives, the technical solution adopted in this invention is: a method for preparing nitrogen-doped calcium-aluminum composite materials, specifically implemented according to the following steps:

[0007] Step 1: Prepare NaAlO2 solution;

[0008] Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution;

[0009] Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir at room temperature after the addition is complete;

[0010] Step 4: After the reaction in Step 3 is complete, filter the reaction solution, dry the filter cake, and keep it warm.

[0011] Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

[0012] As a preferred embodiment of the present invention, the preparation of the NaAlO2 solution in step 1 is specifically as follows:

[0013] Al2O3 was placed in a round-bottom flask at room temperature and water was added, followed by the addition of NaOH and stirring to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH was 1:2.4.

[0014] In a preferred embodiment of the present invention, in step 2, the molar ratio of Ca(OH)2 to NaAlO2 is 1:2.

[0015] As a preferred embodiment of the present invention, in step 3, the molar ratio of Ca(OH)2 to ammonium bicarbonate or ammonium carbonate is 1:0.1.

[0016] As a preferred technical solution of the present invention, in step 4, the heat preservation temperature is 800℃~1000℃ and the heat preservation time is 4h.

[0017] As a preferred embodiment of the present invention, the stirring time in step 3 is 30 minutes.

[0018] The technical solution of the present invention also includes a nitrogen-doped calcium-aluminum composite material, which is obtained using the preparation method of the nitrogen-doped calcium-aluminum composite material of the present invention.

[0019] The beneficial effects of this invention are: the nitrogen-doped calcium-aluminum composite material obtained by this invention can effectively control the concentration of Cl in complex industrial wastewater. - SO4 2- Both methods exhibit good removal effects, meeting the requirements for the recycling of industrial wastewater. The raw materials involved in this invention are inexpensive and readily available; the synthesized nitrogen-doped calcium-aluminum composite material can efficiently reduce Cl in wastewater. - SO4 2- S 2- PO4 3- Anions have significant technical value. Attached Figure Description

[0020] Figure 1 The adsorption capacity of the nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention for chloride ions under different pH conditions;

[0021] Figure 2 The nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention exhibits different effects on Cl at different calcination temperatures. - Adsorption effect diagram;

[0022] Figure 3 The nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention shows the effect of different dosages on Cl. - Adsorption effect diagram;

[0023] Figure 4 The different nitrogen contents (molar ratios) obtained in the nitrogen-doped calcium-aluminum composite material examples of this invention affect the Cl content. - The effect of adsorption;

[0024] Figure 5These are XRD comparison images of different nitrogen contents obtained from the nitrogen-doped calcium-aluminum composite material examples of the present invention;

[0025] Figure 6 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs ClO4. - Electron micrograph;

[0026] Figure 7 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs I - Electron micrograph;

[0027] Figure 8 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs PO4. 3- Electron micrograph;

[0028] Figure 9 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs Cl. - Electron micrograph;

[0029] Figure 10 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs SO4. 2- Electron micrograph;

[0030] Figure 11 This is an infrared comparison image of the nitrogen-doped calcium-aluminum composite material prepared according to the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This invention uses cheaper raw materials such as CaO, Al₂O₃, NaOH, ammonium bicarbonate, or ammonium carbonate to synthesize nitrogen-doped calcium-aluminum composite materials. The optimal anion removal effect is achieved when the molar ratio of these four materials is 1:1:2.4:0.1. Standard sodium chloride solution was tested at room temperature to remove Cl₂. - The adsorption capacity was 740 mg / g. Comparison of scanning electron microscopy images before and after adsorption showed that the material structure recovered to a layered structure. Further research revealed that this material exhibits high adsorption capacity for SO42-. 2- PO4 3- The standard aqueous solution also exhibits good adsorption effect; when the material usage is at an adsorbate / adsorbent mass ratio of 1:10, the material effectively adsorbs SO42-. 2- PO4 3- The adsorption capacities were 850 mg / g and 760 mg / g, respectively; compared with the adsorption of SO3 2- With adsorption of SO4 2- The electron micrographs show that the material has been restored to a well-defined layered structure, indicating its ability to adsorb SO3. 2- SO4 2-It subsequently recovered a good and stable structure, and also demonstrated excellent performance in terms of adsorption capacity.

[0033] The nitrogen-doped calcium-aluminum composite material of this invention can effectively remove anions from wastewater, and its high efficiency and low cost provide a basis for industrial applications. Traditional ultra-high calcium-aluminum dechlorination methods and hydrotalcite dechlorination methods are very costly, and the treated wastewater has high pH and high conductivity, and introduces other anions, making them of limited industrial application value. The nitrogen-doped calcium-aluminum composite material of this invention achieves high efficiency in adsorbing Cl... - SO4 2- S 2- PO4 3- While absorbing anions, it can also absorb acidic gases such as CO2, SO2, and H2S, solving the problems of carbon emissions and acidic gas emissions. In addition, it also has a good removal effect on cations and suspended solids in wastewater.

[0034] During the calcination and preparation process, ammonium ions partially decompose, increasing the gaps between the bimetallic layers in the material structure. This results in a larger specific surface area and pore volume, significantly increasing the number of ion exchange sites. The ammonium ions also enhance the material's high-temperature resistance and anti-sintering ability, preventing the bimetallic layer structure from collapsing during high-temperature calcination. Undecomposed ammonium ions and anions during calcination increase the buffering capacity of the solution, facilitating the smooth exchange of chloride and sulfate ions. The adsorption time is significantly shorter than that of traditional calcium-aluminum bimetallic materials. Traditional calcium-aluminum bimetallic materials adsorb Cl from wastewater... - SO4 2- The usual process takes about 60 minutes, but the novel nitrogen-doped calcium-aluminum composite material of this invention completes adsorption in just 2 minutes. - SO4 2- This makes it easier to release, enabling the repeated regeneration and reuse of the drug, and achieving Cl... - SO4 2- Plasma enrichment and recovery.

[0035] The method for removing anionic pollutants from industrial wastewater using nitrogen-doped calcium-aluminum composite material is as follows: Prepare 100 mL of 500 mg / L sodium chloride solution in the laboratory, add 0.5 g of the prepared nitrogen-doped calcium-aluminum composite material; stir at 20-25℃ for 2 min, remove the filter residue, and a clear liquid with qualified dechlorination can be obtained.

[0036] The nitrogen-doped calcium-aluminum composite material of the present invention, when tested with standard solutions at room temperature, showed that CaO, Al2O3, NaOH, ammonium bicarbonate, or ammonium carbonate, at a molar ratio of 1:1:2.4:0.1, exhibited good adhesion to Cl-. -The removal effect is optimal. This invention screened the material preparation temperature and found that 800–1000℃ was optimal for Cl removal. - It exhibits excellent adsorption performance; by varying the amount of the material used in this invention, it was found that as the amount of the material increases, Cl... - The remaining amount is constantly decreasing, so the amount of material used can be flexibly controlled according to the needs.

[0037] To verify the broad applicability of the material of this invention, experiments were conducted on the industrial wastewater of a chemical enterprise in Lanzhou using the material of this invention. Good results were achieved, and the treatment effect was not affected by other ions in the wastewater. The wastewater quality of this enterprise is Ca... 2+ Concentration 256 mg / L, Mg 2+ Concentration 101 mg / L, Fe 3+ / Fe 2+ Concentration 0.016 mg / L, SO4 2- Concentration 390 mg / L, Cl - The concentration was 585 mg / L, total alkalinity was 377 mg / L, and turbidity was 3 (NTU). After treating this wastewater using the material of this invention, SO42-... 2- The concentration dropped to 14 mg / L, Cl - The concentration was reduced to 39 mg / L, meeting the minimum discharge concentration for chloride ions, and the turbidity of the wastewater was below 10 mg / L. To achieve industrial wastewater treatment, this invention was applied to scale-up tests (10x, 50x, 100x, and 1000x). The adsorption efficiency remained stable, and the turbidity was reduced by 0.2 NTU while adsorbing anions.

[0038] Traditional calcium-aluminum bimetallic materials suffer from problems such as structural damage during calcination, low adsorption rate, and long adsorption time. This invention, by doping the original calcium-aluminum bimetallic material with a nitrogen source (urea, ammonium bicarbonate, ammonium carbonate, etc.), yields a novel nitrogen-doped calcium-aluminum composite material, which exhibits better Cl-removal performance compared to the original undoped material. - SO4 2- The effect is improved, and the adsorption time is greatly shortened. Depending on the amount of material added, Cl - SO4 2- The removal rate can reach over 90%.

[0039] Comparison of the treatment effects of the nitrogen-doped calcium-aluminum composite material of this invention on industrial wastewater:

[0040] The synthetic composite material was applied to treat chemical wastewater from a chemical plant in Lanzhou. The results are compared below (water samples were tested and analyzed by the Chemical Product Quality Inspection Center of Lanzhou Chemical Research Center of China National Petroleum Corporation, which has CNAS and CMA accreditations):

[0041] The following is a comparison of the quality of raw water and treated water:

[0042] Table 1 Comparison of raw water and treated water quality

[0043]

[0044] Figure 1 The adsorption capacity of the nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention for chloride ions under different pH conditions; the pH of industrial wastewater will fluctuate to a certain extent, so we studied the adsorption performance of the material under different conditions. The experiment found that the composite material exhibits excellent performance in treating alkaline solutions.

[0045] Figure 2 The nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention exhibits different effects on Cl at different calcination temperatures. - Adsorption effect diagram; from Figure 2 It can be seen that as the calcination temperature increases during the material preparation process, the adsorption performance of the material first increases and then decreases, with 800℃ being the optimal temperature for material preparation.

[0046] Figure 3 The nitrogen-doped calcium-aluminum composite material obtained in the embodiments of the present invention shows the effect of different dosages on Cl. - Adsorption effect diagram; Figure 3 Cl after reaction treatment - The change in Cl content with the amount of synthetic material added. The higher the amount of synthetic material added, the higher the Cl content after treatment. - The lower the content, the better. Considering cost factors, the optimal amount of material added is selected as 10 times the mass of the adsorbate, that is, adsorbate / adsorbent material = 1 / 10 (mass ratio). In this invention, 0.1L of a 500mg / L sodium chloride solution was used to treat chloride ions, that is, 0.5g of the prepared nitrogen-doped calcium-aluminum composite material was added.

[0047] Figure 4 The different nitrogen contents (molar ratios) obtained in the nitrogen-doped calcium-aluminum composite material examples of this invention affect the Cl content. - The adsorption effect. By changing NH4 + The proportion of Cl in the material - Significant changes occurred in the adsorption of NH4. Experiments revealed that when NH4... + When the content is 0.1 equivalent, Cl - The maximum adsorption capacity is 740 mg / g. With the adsorption of NH4... + The increase and decrease in content, Cl - The adsorption capacity of NH4 is significantly reduced. This can be clearly reflected in the figure. + The effect of content on adsorption performance.

[0048] Figure 5These are XRD comparison images of different nitrogen contents obtained from the nitrogen-doped calcium-aluminum composite material examples of the present invention. The XRD patterns of the nitrogen-doped calcium-aluminum composite materials are as follows: Figure 5 As shown in the figure, the XRD crystal surface exhibits sharp, high-intensity, and well-symmetrical diffraction peaks with a stable spectral baseline and no excessive diffraction peaks from other impurities. This indicates that the synthesized material possesses good crystallinity and a typical bimetallic layered structure. The strong intensity of the diffraction peaks on the crystal plane in the figure indicates good crystallinity. The basic characteristic diffraction peaks at 2θ = 18.1°, 32.3°, 33.3°, 37.4°, 41.1°, and 53.9° are clearly visible, and the diffraction peak shapes are relatively sharp and symmetrical, indicating relatively good crystallinity and purity of the material. By changing the nitrogen source content, the diffraction peak shapes are basically maintained, indicating that the material retains its original layered structure. There is a clear, broad peak at 2θ = 21°, indicating the change in nitrogen source introduction in the material.

[0049] Figures 6-10 These are electron micrographs of the nitrogen-doped calcium-aluminum composite material prepared in this invention, showing the adsorption of different ions. (The text repeats itself here.) Figure 6 , Figure 7 It can be observed that the material of the present invention has a plate-like hexagonal (layered structure) with a relatively uniform particle size. The sample thickness is about 10-15 nm, the structure is flat, the particle size is relatively uniform, the diameter of each hexagon is about 2-3 μm, the thickness is about 200 nm, and the flower-like structure is composed of irregular and intersecting hydrotalcite nanosheets. Figure 8 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs PO4. 3- The electron microscope image shows that the material structure has changed significantly, but it still retains its layered structure.

[0050] Figure 9 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs Cl. - The subsequent electron micrographs show that the material has a lamellar structure, and the material aggregation phenomenon can be corroborated by XPS.

[0051] Figure 10 The nitrogen-doped calcium-aluminum composite material prepared in this invention adsorbs SO4. 2- The electron micrographs show a clear three-dimensional structure. Comparison of electron micrographs of the composite material after adsorption of different anions clearly shows that the morphology changes significantly after adsorption of different anions, providing a foundation for future material updates.

[0052] Figure 11 By comparing the infrared absorption of LDHs-NCA-Cl, LDHs-NCA-100, and LDHs-NCA-800, it was found that the materials exhibit different infrared absorption peaks under temperature changes and interlayer ion exchange conditions, with a peak at 3600 cm⁻¹. -1This is manifested as an absorption peak of hydroxyl groups in the main structure of the material; LDHs-NCA-800 shows an absorption peak at 824 cm⁻¹. -1 There are obvious absorption peaks; LDHs-NCA-Cl and LDHs-NCA-100 show a peak at 546 cm⁻¹. -1 The presence of distinct absorption peaks can provide evidence of structural changes in the material during the absorption process.

[0053] Table 2 Zeta potentials of the invented material after adsorption of different ions.

[0054] Material Name zeta potential (mV) LDHS-NCA-Cl 23.70 LDHS-NCA-ClO 8.14 <![CDATA[LDHS-NCA-ClO2]]> 8.49 <![CDATA[LDHS-NCA-ClO3]]> 18.93 <![CDATA[LDHs-NCA-ClO4]]> 45.48 LDHS-NCA-F 25.14 LDHS-NCA-Br 23.20 LDHS-NCA-I 31.64

[0055] The zeta potentials in Table 2 demonstrate that the nitrogen-doped calcium-aluminum composite material prepared in this invention exhibits good stability after halogen adsorption, providing direction for further material optimization. We also investigated the zeta potentials for other oxidation states of Cl, including ClO4. - The zeta potential is the highest. Comparing the zeta potentials of different halogens in the same oxidation state, the potential first decreases and then increases with increasing ionic radius.

[0056] Example 1

[0057] The preparation method of the nitrogen-doped calcium-aluminum composite material of the present invention is specifically implemented according to the following steps:

[0058] Step 1: Place Al2O3 in a round-bottom flask at room temperature and add water, then add NaOH and stir to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH is 1:2.4.

[0059] Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution; wherein the molar ratio of Ca(OH)2 to NaAlO2 is 1:2;

[0060] Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir for 30 minutes at room temperature after the addition is complete; wherein the molar ratio of ammonium bicarbonate or ammonium carbonate to Ca(OH)2 is 0.1:1;

[0061] Step 4: After the reaction in Step 3 has proceeded for 20 minutes, the reaction solution is filtered, the filter cake is dried, and the solution is kept at a temperature of 800℃ for 4 hours.

[0062] Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

[0063] Example 2

[0064] The preparation method of the nitrogen-doped calcium-aluminum composite material of the present invention is specifically implemented according to the following steps:

[0065] Step 1: Place Al2O3 in a round-bottom flask at room temperature and add water, then add NaOH and stir to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH is 1:2.4.

[0066] Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution; wherein the molar ratio of Ca(OH)2 to NaAlO2 is 1:2;

[0067] Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir for 30 minutes at room temperature after the addition is complete; wherein the molar ratio of ammonium bicarbonate or ammonium carbonate to Ca(OH)2 is 0.1:1;

[0068] Step 4: After the reaction in Step 3 has proceeded for 20 minutes, the reaction solution is filtered, the filter cake is dried, and the solution is kept at a temperature of 900℃ for 4 hours.

[0069] Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

[0070] Example 3

[0071] The preparation method of the nitrogen-doped calcium-aluminum composite material of the present invention is specifically implemented according to the following steps:

[0072] Step 1: Place Al2O3 in a round-bottom flask at room temperature and add water, then add NaOH and stir to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH is 1:2.4.

[0073] Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution; wherein the molar ratio of Ca(OH)2 to NaAlO2 is 1:2;

[0074] Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir for 30 minutes at room temperature after the addition is complete; wherein the molar ratio of ammonium bicarbonate or ammonium carbonate to Ca(OH)2 is 0.1:1;

[0075] Step 4: After the reaction in Step 3 has proceeded for 20 minutes, the reaction solution is filtered, the filter cake is dried, and the solution is kept at a temperature of 950℃ for 4 hours.

[0076] Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

[0077] Example 4

[0078] The preparation method of the nitrogen-doped calcium-aluminum composite material of the present invention is specifically implemented according to the following steps:

[0079] Step 1: Place Al2O3 in a round-bottom flask at room temperature and add water, then add NaOH and stir to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH is 1:2.4.

[0080] Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution; wherein the molar ratio of Ca(OH)2 to NaAlO2 is 1:2;

[0081] Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir for 30 minutes at room temperature after the addition is complete; wherein the molar ratio of ammonium bicarbonate or ammonium carbonate to Ca(OH)2 is 0.1:1;

[0082] Step 4: After the reaction in Step 3 has proceeded for 20 minutes, the reaction solution is filtered, the filter cake is dried, and the solution is kept at a temperature of 1000℃ for 4 hours.

[0083] Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

Claims

1. A method for preparing nitrogen-doped calcium-aluminum composite materials, characterized in that, The specific steps are as follows: Step 1: Prepare NaAlO2 solution; Step 2: Add NaAlO2 solution to Ca(OH)2 emulsion to obtain reaction solution; Step 3: Gradually add ammonium bicarbonate or ammonium carbonate solution dropwise to the reaction solution, and stir at room temperature after the addition is complete; Step 4: After the reaction in Step 3 is complete, filter the reaction solution, dry the filter cake, and keep it at a warm temperature. Step 5: Calcine the product obtained in step 4 to obtain nitrogen-doped calcium-aluminum composite material.

2. The method for preparing nitrogen-doped calcium-aluminum composite material according to claim 1, characterized in that, In step 1, the preparation of the NaAlO2 solution is as follows: Al2O3 was placed in a round-bottom flask at room temperature and water was added, followed by the addition of NaOH and stirring to obtain a NaAlO2 solution; the molar ratio of Al2O3 to NaOH was 1:2.

4.

3. The method for preparing nitrogen-doped calcium-aluminum composite material according to claim 2, characterized in that, In step 2, the molar ratio of Ca(OH)2 to NaAlO2 is 1:

2.

4. The method for preparing nitrogen-doped calcium-aluminum composite material according to claim 3, characterized in that, In step 3, the molar ratio of ammonium bicarbonate or ammonium carbonate to Ca(OH)2 is 0.1:

1.

5. The method for preparing nitrogen-doped calcium-aluminum composite material according to claim 4, characterized in that, In step 4, the heat preservation temperature is 800℃-1000℃, and the heat preservation time is 4 hours.

6. The method for preparing nitrogen-doped calcium-aluminum composite material according to claim 5, characterized in that, The stirring time in step 3 is 30 minutes, and the reaction time in step 4 is 20 minutes.

7. A nitrogen-doped calcium-aluminum composite material, characterized in that, The nitrogen-doped calcium-aluminum composite material was prepared using the preparation method described in any one of claims 1-6.

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