Composite environmental purification material and preparation method thereof

Abstract

The present application relates to a kind of adsorption-visible light catalytic type environmental purification material Bi2O2CO3 / MgAlBi-LDHs and preparation method thereof, belong to water environmental pollutant processing and functional material technical field.The Bi2O2CO3 / MgAlBi-LDHs composite material is by in-situ growth MgAlBi hydrotalcite on Bi2O2CO3, and the mass ratio of Bi2O2CO3 and MgAlBi-LDHs is 1 / 5~1 / 15.The composite material has the characteristics such as visible light catalytic degradation antibiotic, reduction heavy metal ions: under visible light, the catalytic reduction efficiency of Bi2O2CO3 / MgAlBi-LDHs-1 / 10 to Cr (VI) is 99.05% in 240 min, and the catalytic degradation efficiency to tetracycline hydrochloride is 99.48%.The adsorption-visible light catalytic composite material prepared in the present application has important application in the green, efficient treatment of actual mixed pollutants.

Description

Technical Field

[0001] This invention relates to an adsorption-visible photocatalytic environmental purification material, its preparation method and application, belonging to the technical field of water environment pollutant treatment and functional materials. Background Technology

[0002] Chromium (Cr) pollution is a serious form of water pollution. In wastewater, Cr exists primarily in two valence states: Cr(III) and Cr(VI). Cr(VI) is approximately 100 times more toxic than Cr(III) and is difficult to degrade naturally. Common methods for removing Cr(VI) and TC include membrane separation, adsorption, chemical precipitation, electrolysis, and photocatalytic degradation. Among these methods, adsorption is widely used due to its low cost and high efficiency; it is also one of the more economical and convenient methods for treating antibiotic wastewater.

[0003] Layered bimetallic hydroxides—hydrotalcite—are commonly used adsorbents. They are two-dimensional anionic clays with a structure similar to brucite, where the layers are composed of tunable divalent and trivalent metal cations, and the interlayers are balanced by exchangeable anions. Hydrotalcite has attracted considerable attention due to its large specific surface area, good ion exchange performance, and good thermal stability. Bi-based semiconductors have recently attracted great interest from researchers as an important class of photocatalysts, especially materials with Aurivilius-type layered structures that can induce internal electrostatic fields, thereby effectively promoting the separation and transfer of photogenerated carriers. Bismuth oxycarbonate (Bi₂O₂CO₃) is a representative material of Bi-based Aurivilius oxide semiconductors, consisting of alternating [Bi₂O₂]... 2+ Layers and [CO3] 2- Layered composition. Due to its unique layered structure and excellent physicochemical properties, Bi2O2CO3 has wide applications in photocatalysis, humidity sensors, supercapacitors, nonlinear optics, and medicine. Bi2O2CO3 has been shown to effectively photodegrade organic pollutants and photoreduce Cr(VI), and its photocatalytic performance can be further improved.

[0004] However, hydrotalcite, a mineral-based adsorbent, has drawbacks such as easy aggregation, low adhesion efficiency, poor cycleability, and limited adsorption sites. Moreover, it only adsorbs Cr(VI) and TC on the surface without destroying their structure, thus not reducing their potential environmental risks. The adsorbent still needs secondary treatment after use, which increases the cost. It also cannot completely remove Cr(VI) and TC. Therefore, researchers chose to combine photocatalysts with adsorbents with good adsorption effects to prepare adsorption-photocatalysis composite materials, so as to achieve the synergistic removal of Cr(VI) and TC mixed solutions by adsorption and photocatalysis.

[0005] Existing technologies have reported some materials that combine photocatalytic semiconductors with hydrotalcite for Cr(VI) removal. For example, Chinese patent document CN109529793A reports the preparation of magnetic ZnAl-LDHs followed by the combination of magnetic hydrotalcite and titanium dioxide to obtain a composite material. This method produces a composite material that only absorbs ultraviolet light and cannot utilize visible light for photocatalytic degradation of Cr(VI). Chinese patent document CN109569561A reports the combination of graphene and ZnAlTi-LDHs followed by calcination in air to obtain a composite material. This method produces a composite material with low Cr(VI) degradation concentration under visible light, resulting in limited effectiveness. Bin et al. (Chem.Eng.J., 2020, 380, 122600) used g- A composite material is obtained by combining C3N4 with CoFe-LDHs and then calcining it in air. This method produces a composite material with good adsorption and photocatalytic removal of Cr(VI). However, the photocatalytic degradation uses a 300W xenon lamp, resulting in high equipment power and energy consumption. Chinese patent document CN106076253A reports a hydrotalcite-modified biomass material for removing TC from water. This material modifies biomass using hydrotalcite and then carbonizes it through pyrolysis, but only adsorbs TC without utilizing photocatalytic degradation. Chinese patent document CN109133452A reports loading TiO2 onto magnesium aluminum hydrotalcite. This composite material only achieves excellent removal performance under ultraviolet light but cannot remove TC using photocatalytic technology. Dai et al. (Applied...) (ClayScience, 2021, 212, 106210) The composite material prepared by CdS and ZnCr-LDHs through hydrothermal reaction has a good effect on removing TC. However, the photocatalytic degradation uses a 500W xenon lamp, which consumes a lot of power.

[0006] Therefore, it is particularly important to develop a material that absorbs visible light, has good adsorption and photocatalytic effects, and consumes little energy during degradation for wastewater treatment. Summary of the Invention

[0007] The first technical problem solved by this invention is to provide an environmental purification material that uses adsorption-visible photocatalysis technology to synergistically remove Cr(VI) and TC from a mixed solution.

[0008] Bi2O2CO3 / MgAlBi-LDHs composite material: The Bi2O2CO3 / MgAlBi-LDHs composite material is prepared by in-situ growth of MgAlBi hydrotalcite on Bi2O2CO3. In the composite material, the mass ratio of Bi2O2CO3 to MgAlBi-LDHs is 1 / 5 to 1 / 15.

[0009] The Bi₂O₂CO₃ / MgAlBi-LDHs composite structure of this invention not only provides abundant adsorption sites but also exhibits strong photocatalytic reduction ability under visible light, reducing Cr(VI) to non-toxic Cr(III), significantly improving Cr(VI) removal capacity and greatly enhancing TC removal efficiency. The removal capacity of this invention for Cr(VI) and TC is superior to that of Bi₂O₂CO₃ and MgAlBi-LDHs alone.

[0010] The second technical problem solved by this invention is to provide a method for preparing an adsorption-photocatalytic environmental purification material Bi2O2CO3 / MgAlBi-LDHs.

[0011] The preparation method of Bi2O2CO3 / MgAlBi-LDHs adsorption-photocatalysis composite material includes the following steps:

[0012] a. Dissolve Bi(NO3)3·5H2O pentahydrate in nitric acid HNO3, add citric acid C6H8O7 and sonicate for 10 min, and control the pH of the solution with sodium hydroxide NaOH.

[0013] b. Transfer the white precursor formed in step a to a stainless steel autoclave lined with polytetrafluoroethylene and place it in an oven for a certain period of time. After cooling to room temperature, centrifuge, wash several times with distilled water and ethanol, and then vacuum dry at a certain temperature to obtain Bi2O2CO3.

[0014] c. Subsequently, magnesium nitrate hexahydrate Mg(NO3)2·6H2O and aluminum nitrate nonahydrate Al(NO3)3·9H2O were dissolved in water, and bismuth nitrate pentahydrate Bi(NO3)3·5H2O was dissolved in nitric acid HNO3 to obtain a mixed metal salt solution. Sodium hydroxide NaOH and sodium carbonate Na2CO3 were dissolved in water to obtain a mixed alkaline solution. The mixed metal salt solution and the mixed alkaline solution were simultaneously and slowly added dropwise to a three-necked flask containing Bi2O2CO3 using a constant pressure funnel. During the addition, the pH value in the three-necked flask was controlled by the mixed alkaline solution. After stirring for 60 min, the flask was placed in a drying oven for crystallization and then centrifuged to obtain the Bi2O2CO3 / MgAlBi-LDHs composite material.

[0015] In one embodiment, in step a, the pH value of the reaction solution is controlled to be 2 to 10; preferably, the pH value of the reaction solution is 6.

[0016] In one embodiment, in step b, the hydrothermal temperature is 120–180°C; preferably, the hydrothermal temperature is 160°C.

[0017] In one embodiment, the hydrothermal time in step b is 12 to 36 hours; preferably, the hydrothermal time is 24 hours.

[0018] In one embodiment, in step c, the pH value of the reaction solution is controlled to be 8 to 12; preferably, the pH value of the reaction solution is 10.

[0019] In one embodiment, in step c, the mass ratio of Bi2O2CO3 to MgAlBi-LDHs is 1 / 5 to 1 / 15; preferably, the mass ratio of Bi2O2CO3 to MgAlBi-LDHs is 1 / 10.

[0020] The third technical problem solved by this invention is to provide an application of the adsorption-photocatalytic environmental purification material Bi2O2CO3 / MgAlBi-LDHs, that is, to use it for the co-removal of Cr(VI) and TC in a mixed solution.

[0021] The beneficial effects of this invention are:

[0022] 1. The Bi2O2CO3 / MgAlBi-LDHs adsorption-photocatalysis composite material of the present invention, through the Bi in the structure 3+ The introduction of [the substance] increases the porosity of hydrotalcite and the number of adsorption sites, which can significantly improve the adsorption of Cr(VI) and TC. At the same time, through in-situ growth on Bi2O2CO3, the composite material exhibits excellent adsorption-photocatalytic synergistic degradation of Cr(VI) and TC under visible light, reducing Cr(VI) to non-toxic Cr(III), further enhancing the removal capacity of Cr(VI) and TC.

[0023] 2. The raw materials used in the preparation method of the present invention are widely available. Low-power LED lamps are used when photocatalytically degrading Cr(VI) and TC, resulting in low energy consumption and simple operation. Attached Figure Description

[0024] Figure 1 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 5 composite material obtained in Example 1.

[0025] Figure 2 The graph shows the removal efficiency of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 5 composite material obtained in Example 1.

[0026] Figure 3 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 10 composite material obtained in Example 2.

[0027] Figure 4 The graph shows the removal efficiency of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 10 composite material obtained in Example 2.

[0028] Figure 5 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 15 composite material obtained in Example 3.

[0029] Figure 6 The graph shows the removal efficiency of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 15 composite material obtained in Example 3. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0031] Photocatalytic activity test

[0032] The degradation target was a mixed solution of Cr(VI) and TC with a concentration of 10 mg / L and 10 mg / L respectively. Bi2O2CO3 / MgAlBi-LDHs adsorption-photocatalysis material was added to the reactor, and the mixture was stirred in the dark for 60 min to allow the reaction system in the solution to reach adsorption-desorption equilibrium. Then, a 40W LED lamp was turned on for photocatalytic degradation. Samples were taken every 15-30 min throughout the experiment, with 6 ml of sample taken each time. The supernatant was collected by centrifugation, and the Cr(VI) content was determined by diphenylcarbazide spectrophotometry, while the TC concentration was determined by UV-Vis spectrophotometry. The absorbance values ​​at wavelengths of 540 nm and 357 nm were measured, and the removal rates of Cr(VI) and TC were calculated.

[0033] Example 1

[0034] Synthesis process:

[0035] 1) Dissolve 1.4552g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O in 20mL of 1M nitric acid HNO3, add 2mmol of citric acid C6H8O7 to the solution, sonicate for 10min, stir magnetically for 60min, and then control the pH of the solution to 2 with sodium hydroxide NaOH solution.

[0036] 2) The white precursor formed in step 1) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven at 120°C for 12 hours. After cooling to room temperature, the Bi2O2CO3 precursor was separated by centrifugation and washed several times with distilled water and ethanol. Then, it was vacuum dried at a certain temperature to obtain Bi2O2CO3.

[0037] 3) Subsequently, 3.077g of magnesium nitrate hexahydrate Mg(NO3)2·6H2O and 1.4855g of aluminum nitrate nonahydrate Al(NO3)3·9H2O were dissolved in water, and 0.0388g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O was dissolved in nitric acid HNO3 to obtain a mixed metal salt solution. 1.28g of sodium hydroxide NaOH and 0.848g of sodium carbonate Na2CO3 were dissolved in water to obtain a mixed alkaline solution. The mixed metal salt solution and the mixed alkaline solution were simultaneously and slowly added dropwise to a three-necked flask containing Bi2O2CO3 and ultrasonically treated. During the addition, the pH value in the three-necked flask was controlled to 8 by the mixed alkaline solution. After the addition was completed, the mixture was stirred for 60 minutes and then placed in a drying oven at 60℃ for crystallization. The mixture was then centrifuged and dried to obtain the Bi2O2CO3 / MgAlBi-LDHs composite material.

[0038] Figure 1 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 5 adsorption-photocatalytic composite material obtained in Example 1 of this invention. Figure 1 It can be seen that the XRD results of Bi2O2CO3 prepared in Example 1 are consistent with the standard diffraction peaks, and no other impurity peaks are observed. The obtained composite sample has good crystallinity and its crystal structure is not damaged. Both samples show diffraction peaks of Bi2O2CO3 and LDHs, and no other impurity peaks are observed, indicating that the composite structure was successfully constructed under these growth conditions.

[0039] Figure 2 This is a graph showing the removal efficiency of a mixed solution of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 5 adsorption-photocatalytic composite material obtained in Example 1 of this invention. Figure 2 It can be seen that the Bi2O2CO3 / MgAlBi-LDHs-1 / 5 composite material obtained in Example 1 achieved removal rates of 79.67% and 89.35% for Cr(VI) solution and TC solution with a concentration of 10 mg / L within 240 min, respectively, which effectively removed heavy metals and organic pollutants from the aquatic environment.

[0040] Example 2

[0041] Synthesis process:

[0042] 1) Dissolve 1.4552g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O in 20mL of 1M nitric acid HNO3, add 2mmol of citric acid C6H8O7 to the solution, sonicate for 10min, stir magnetically for 60min, and then control the pH of the solution to 6 with sodium hydroxide NaOH solution.

[0043] 2) The white precursor formed in step 1) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven at 160°C for 24 hours. After cooling to room temperature, the Bi2O2CO3 precursor was separated by centrifugation and washed several times with distilled water and ethanol. Then, it was vacuum dried at a certain temperature to obtain Bi2O2CO3.

[0044] 3) Subsequently, 3.077g of magnesium nitrate hexahydrate Mg(NO3)2·6H2O and 1.4705g of aluminum nitrate nonahydrate Al(NO3)3·9H2O were dissolved in water, and 0.0388g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O was dissolved in nitric acid HNO3 to obtain a mixed metal salt solution. 1.28g of sodium hydroxide NaOH and 0.848g of sodium carbonate Na2CO3 were dissolved in water to obtain a mixed alkaline solution. The mixed metal salt solution and the mixed alkaline solution were simultaneously and slowly added dropwise to a three-necked flask containing Bi2O2CO3 and ultrasonically treated. During the addition, the pH value in the three-necked flask was controlled to 10 by the mixed alkaline solution. After the addition was completed, the mixture was stirred for 60 minutes and then placed in a drying oven at 60℃ for crystallization. The mixture was then centrifuged and dried to obtain the Bi2O2CO3 / MgAlBi-LDHs composite material.

[0045] Figure 3 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 10 adsorption-photocatalytic composite material prepared in Example 2 of this invention. Figure 3 It can be seen that the XRD results of Bi2O2CO3 prepared in Example 2 are consistent with the standard diffraction peaks, and no other impurity peaks are observed. The XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs composite photocatalyst material shows both diffraction peaks of Bi2O2CO3 and diffraction peaks of MgAlBi-LDHs, indicating that the composite structure was successfully constructed under these growth conditions.

[0046] Figure 4 This is a graph showing the removal efficiency of a mixed solution of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 10 adsorption-photocatalytic composite material obtained in Example 2 of this invention. Figure 4 It can be seen that the Bi2O2CO3 / MgAlBi-LDHs-1 / 10 composite material obtained in Example 2 achieved removal rates of 99.05% and 99.48% for Cr(VI) solution and TC solution with a concentration of 10 mg / L within 240 min, respectively, realizing the complete removal of heavy metals and organic pollutants in the aquatic environment.

[0047] Example 3

[0048] Synthesis process:

[0049] 1) Dissolve 1.4552g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O in 20mL of 1M nitric acid HNO3, add 2mmol of citric acid C6H8O7 to the solution, sonicate for 10min, stir magnetically for 60min, and then control the pH of the solution to 10 with sodium hydroxide NaOH solution.

[0050] 2) The white precursor formed in step 1) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven at 180°C for 36 hours. After cooling to room temperature, the Bi2O2CO3 precursor was separated by centrifugation and washed several times with distilled water and ethanol. Then, it was vacuum dried at a certain temperature to obtain Bi2O2CO3.

[0051] 3) Subsequently, 3.077g of magnesium nitrate hexahydrate Mg(NO3)2·6H2O and 1.4255g of aluminum nitrate nonahydrate Al(NO3)3·9H2O were dissolved in water, and 0.0388g of bismuth nitrate pentahydrate Bi(NO3)3·5H2O were dissolved in HNO3 to obtain a mixed metal salt solution. 1.28g of sodium hydroxide NaOH and 0.848g of sodium carbonate Na2CO3 were dissolved in water to obtain a mixed alkaline solution. The mixed metal salt solution and the mixed alkaline solution were simultaneously and slowly added dropwise to a three-necked flask containing Bi2O2CO3 and ultrasonically treated. During the addition, the pH value in the three-necked flask was controlled to 11 by the mixed alkaline solution. After the addition was completed, the mixture was stirred for 60 minutes and then placed in a drying oven at 60℃ for crystallization. The mixture was then centrifuged and dried to obtain the Bi2O2CO3 / MgAlBi-LDHs composite material.

[0052] Figure 5 The image shows the XRD pattern of the Bi2O2CO3 / MgAlBi-LDHs-1 / 15 adsorption-photocatalytic composite material prepared in Example 3 of this invention. Figure 5 It can be seen that the XRD results of Bi2O2CO3 prepared in Example 3 are consistent with the standard diffraction peaks, and no other impurity peaks appear. The XRD pattern of Bi2O2CO3 / MgAlBi-LDHs composite photocatalyst material shows both diffraction peaks of Bi2O2CO3 and diffraction peaks of MgAlBi-LDHs, indicating that the composite structure was successfully constructed under these growth conditions.

[0053] Figure 6 This is a graph showing the removal efficiency of a mixed solution of Cr(VI) and TC in the Bi2O2CO3 / MgAlBi-LDHs-1 / 15 adsorption-photocatalytic composite material obtained in Example 3 of this invention. Figure 6 It can be seen that the Bi2O2CO3 / MgAlBi-LDHs-1 / 15 composite material obtained in Example 3 achieved removal rates of 84.48% and 89.75% for Cr(VI) solution and TC solution with a concentration of 10 mg / L within 240 min, respectively, which effectively removed heavy metals and organic pollutants from the aquatic environment.

Claims

1. An application of an adsorption-visible photocatalytic environmental purification material, characterized in that: The material has a structure of Bi2O2CO3 / MgAlBi-LDHs, where the mass ratio of Bi2O2CO3 to MgAlBi-LDHs is 1 / 5 to 1 / 15. It is used for the co-removal of Cr(VI) and tetracycline hydrochloride in a mixed solution.

2. The application of the adsorption-visible photocatalytic environmental purification material as described in claim 1, wherein the preparation method of Bi2O2CO3 / MgAlBi-LDHs includes the following steps: a. Dissolve Bi(NO3)3·5H2O pentahydrate in nitric acid HNO3, add citric acid C6H8O7 and sonicate for 10 min, and control the pH of the solution with sodium hydroxide NaOH; b. The white precursor formed in step a is transferred to a stainless steel autoclave lined with polytetrafluoroethylene and placed in an oven for a certain period of time. After cooling to room temperature, it is centrifuged, washed several times with distilled water and ethanol, and then vacuum dried at a certain temperature to obtain Bi2O2CO3. c. Subsequently, magnesium nitrate hexahydrate Mg(NO3)2·6H2O and aluminum nitrate nonahydrate Al(NO3)3·9H2O were dissolved in water, and bismuth nitrate pentahydrate Bi(NO3)3·5H2O was dissolved in nitric acid HNO3 to obtain a mixed metal salt solution. Sodium hydroxide NaOH and sodium carbonate Na2CO3 were dissolved in water to obtain a mixed alkaline solution. The mixed metal salt solution and the mixed alkaline solution were simultaneously and slowly added dropwise to a three-necked flask containing Bi2O2CO3 using a constant pressure funnel. During the addition, the pH value in the three-necked flask was controlled by the mixed alkaline solution. After stirring for 60 min, the mixture was placed in a drying oven for crystallization and then centrifuged to obtain the Bi2O2CO3 / MgAlBi-LDHs composite material.

3. The application of the adsorption-visible photocatalytic environmental purification material according to claim 2, characterized in that: In step a, the pH of the reaction solution is controlled to be between 2 and 10.

4. The application of the adsorption-visible photocatalytic environmental purification material according to claim 2, characterized in that: In step b, the temperature inside the oven is 120~180 ℃.

5. The application of the adsorption-visible photocatalytic environmental purification material according to claim 2, characterized in that, In step b, the time spent in the oven is 12 to 36 hours.

6. The application of the adsorption-visible photocatalytic environmental purification material according to claim 2, characterized in that, In step c, the pH value of the solution in the three-necked flask is 8~11.

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