Fe-Sr double hydroxide, preparation method thereof and application of Fe-Sr double hydroxide in photo-Fenton catalytic degradation of organic pollutants

Abstract

The invention belongs to the technical field of environmental pollution treatment and advanced oxidation, and particularly relates to a Fe-Sr double hydroxide, a preparation method thereof and application of the Fe-Sr double hydroxide in photo-Fenton catalytic degradation of organic pollutants. The preparation method comprises the following steps: dissolving a strontium source and an iron source in deionized water, adjusting the pH value to be alkaline, carrying out a hydrothermal reaction, cooling, centrifugally washing and drying to obtain Fe-Sr double hydroxides; in the prepared material, Fe and Sr elements form a stable composite structure, and the material has good dispersity and synergistic catalytic performance. Under the irradiation of visible light or ultraviolet light, the catalyst is used as a photo-Fenton reaction catalyst and has a synergistic effect with hydrogen peroxide to efficiently catalyze and degrade methylene blue in a water body. And the photocatalyst shows excellent photo-Fenton catalytic activity and degradation efficiency. The preparation method disclosed by the invention is simple in process, mild in condition and easily available in raw materials, and the product has good photoresponse performance, catalytic stability and reusability and has practical application potential of efficiently degrading pollutants under a near-neutral condition.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control and advanced oxidation technology, specifically relating to a Fe-Sr double hydroxide, its preparation method, and its application in photo-Fenton catalytic degradation of organic pollutants. Background Technology

[0002] With the rapid development of industries such as printing and dyeing, textiles, papermaking, and chemicals, large amounts of industrial wastewater containing organic dyes are being discharged into natural water bodies. Among them, methylene blue (MB), as a typical cationic dye, has characteristics such as stable chemical structure, poor biodegradability, phototoxicity, and potential carcinogenicity. If discharged directly without effective treatment, it will pose a serious threat to aquatic ecosystems and human health.

[0003] Traditional advanced oxidation techniques (such as the classic Fenton reaction) can, although through Fe 2+ The H2O2 system generates highly oxidizing hydroxyl radicals (·OH) to degrade organic pollutants, but it has problems such as a narrow pH range (usually requiring strong acidity), easy loss of iron ions, difficulty in catalyst recovery, and low H2O2 utilization.

[0004] In recent years, photo-Fenton technology has promoted the growth of Fe by introducing light conditions. 3+ / Fe 2+ Rapid recycling and regeneration, and accelerated decomposition of H2O2 to generate more reactive oxygen species, significantly improve degradation efficiency and broaden the applicable pH range. Heterogeneous photo-Fenton catalysts based on iron-based materials have attracted widespread attention due to their good stability and reusability. However, single iron-based materials often suffer from drawbacks such as narrow photoresponse range and high carrier recombination rate. Therefore, developing novel iron-based composite catalytic materials, by introducing other metal elements to form a synergistic effect, to improve light absorption capacity, photogenerated carrier separation efficiency, and Fenton activity, has significant research value and application prospects. Summary of the Invention

[0005] To address the problems of complex preparation processes, insufficient catalytic efficiency, and limited pH application range in existing photo-Fenton catalysts, this invention provides a method for preparing Fe-Sr double hydroxides and their application in the photo-Fenton reaction for the degradation of organic dyes such as methylene blue (MB). The prepared Fe-Sr double hydroxides exhibit good photoresponsiveness and catalytic stability, and can efficiently activate hydrogen peroxide under near-neutral conditions, achieving rapid degradation of organic dyes.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for preparing Fe-Sr double hydroxides, comprising the following steps:

[0007] Strontium and iron sources were completely dissolved in deionized water, and NaOH solution was added to adjust the pH to alkaline to form a suspension. The suspension was then transferred to a hydrothermal reactor, sealed, and subjected to a hydrothermal reaction. After the reaction was completed, the suspension was allowed to cool naturally, centrifuged, washed until the filtrate was neutral, and dried to obtain Fe-Sr double hydroxide.

[0008] In the above-mentioned method for preparing Fe-Sr double hydroxide, the strontium source and iron source are strontium chloride and ferric chloride, respectively.

[0009] In the above-mentioned method for preparing Fe-Sr double hydroxide, the molar ratio of strontium chloride, ferric chloride, and NaOH is 1:2:8.

[0010] In the above-mentioned method for preparing Fe-Sr double hydroxide, the hydrothermal reaction temperature is 120℃ and the reaction time is 12h.

[0011] The Fe-Sr double hydroxide was prepared according to the above preparation method.

[0012] The above-mentioned Fe-Sr double hydroxides are used in the photo-Fenton reaction to degrade organic dye pollutants.

[0013] In the above application, the organic dye pollutant is methylene blue.

[0014] Under light irradiation, the Fe-Sr double hydroxide is added to an aqueous solution containing methylene blue (MB) or other organic dyes, along with an appropriate amount of hydrogen peroxide, to initiate a photo-Fenton reaction. Through light-promoted Fe³⁺ / Fe²⁺ cycling and the activation of H₂O₂ by the active sites on the material surface, a large number of hydroxyl radicals are generated, achieving efficient and rapid degradation of organic dye pollutants.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Simple preparation process and mild conditions: It adopts a one-step synthesis method combining co-precipitation and low temperature hydrothermal method. The raw materials are cheap and readily available. No complicated equipment or high temperature and high pressure are required, which is suitable for industrial scale-up production.

[0017] 2. Excellent photo-Fenton catalytic performance: Fe-Sr double hydroxide exhibits good photoresponse ability under visible or ultraviolet light irradiation, which can significantly promote the iron valence state cycle, improve the decomposition efficiency of H2O2, and realize the rapid degradation of organic dyes such as methylene blue.

[0018] 3. Wide pH range: It can still catalyze degradation efficiently under near-neutral or even weakly alkaline conditions, overcoming the limitation of the traditional Fenton reaction requiring a strong acid environment.

[0019] 4. The catalyst has good stability and can be reused: The material has a stable structure, low metal ion dissolution, and maintains high catalytic activity after multiple cycles, showing good potential for practical application.

[0020] 5. Environmentally friendly: The raw materials used are non-toxic, and the preparation and application processes do not introduce secondary pollution, making it suitable for actual organic pollutant treatment scenarios such as dyeing and printing wastewater. Attached Figure Description

[0021] Figure 1 This is the XRD pattern of Fe-Sr double hydroxide;

[0022] Figure 2 This is a time-dependent plot of photo-Fenton degradation of MB;

[0023] Figure 3 This is a time dependence plot of the peak intensity at 554 nm in the UV-Vis spectrum of MB. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] Example 1

[0026] Weigh 0.605 g (0.0025 mol) of SrCl2·6H2O and 0.811 g (0.005 mol) of anhydrous FeCl3, add them to 20 mL of deionized water, and stir magnetically for 10 min until completely dissolved to form a homogeneous yellow transparent solution.

[0027] While stirring continuously, 20.0 mL of 1 mol / L NaOH solution (total 0.02 mol) was added dropwise to the above solution. After the addition was complete, stirring was continued for 30 min to form a reddish-brown uniform suspension. At this time, the pH of the system was measured to be 9-10 using pH test paper.

[0028] The resulting suspension was transferred to a 50 mL polytetrafluoroethylene-lined hydrothermal reactor, and deionized water was added to bring the total volume to 35 mL (approximately 70% filling). The reactor was then sealed and placed in an oven at 120°C for 12 h.

[0029] After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The product was then centrifuged and washed repeatedly with deionized water and anhydrous ethanol until the supernatant was neutral. Subsequently, it was vacuum dried at 60°C for 6 h to obtain Fe-Sr double hydroxide powder (reddish-brown). XRD analysis is shown below. Figure 1 As shown.

[0030] Example 2

[0031] Take 20 mL of solution with a concentration of 2×10-6 A methylene blue (MB) solution of mol / L was used as a simulated pollutant (equivalent to approximately 0.64 mg / L, calculated based on the MB molecular weight of 319.85 g / mol). 20 mg of the Fe-Sr double hydroxide catalyst prepared in Example 1 (catalyst dosage of 1 g / L) was added, along with an appropriate amount of hydrogen peroxide (H2O2, typically optimized at 10 mmol / L, added according to actual experimental conditions).

[0032] First, adsorption experiments were conducted under dark conditions (no light). Samples were taken after stirring for 10, 20, and 30 minutes, and the absorbance change of methylene blue at its characteristic absorption peak of approximately 664 nm was measured using a UV-Vis spectrophotometer. The results showed that under dark conditions, the absorbance of methylene blue decreased slowly over time, mainly due to the physical adsorption of the catalyst. At 30 minutes, the absorbance remained at approximately 70%–80% of its initial value (corresponding to the dark 0 min to dark 30 min curve in the figure). Subsequently, a light source (simulating sunlight, a 300W xenon lamp with a filter) was turned on to conduct the photo-Fenton degradation reaction. Samples were taken at 3, 6, 9, 12, and 15 minutes of illumination, and the absorbance change was measured. Figure 2 As shown.

[0033] The results of ultraviolet-visible absorption spectroscopy tests show that:

[0034] Dark adsorption phase (0~30 min): The intensity of the characteristic absorption peak (around 664 nm) gradually decreases (e.g.) Figure 3 ), showing limited adsorption removal;

[0035] After the light was turned on, the intensity of the absorption peak dropped sharply: the peak value was significantly reduced after 3 minutes of light exposure (to about 40% to 50% of the initial value), it further decreased after 6 minutes of light exposure, the peak value was greatly weakened after 9 minutes of light exposure, it was close to the baseline after 12 minutes of light exposure, and the characteristic absorption peak almost completely disappeared after 15 minutes of light exposure (the absorbance dropped to close to 0), and the solution changed from blue to nearly colorless.

[0036] The above spectral changes indicate that the Fe-Sr double hydroxide prepared in this invention exhibits excellent catalytic activity in the photo-Fenton system, achieving near-complete degradation of methylene blue within 15 minutes of light irradiation. This degradation efficiency is significantly higher than that of the simple dark adsorption process, fully demonstrating the significant promoting effect of light irradiation on the iron valence cycle and H2O2 activation. This performance is also observed at low concentrations of MB (2×10⁻⁶). -6 Even under conditions of mol / L, it still exhibits highly efficient and rapid removal capabilities, demonstrating the material's application potential in the treatment of organic pollutants in dilute solutions.

Claims

1. A method for preparing Fe-Sr double hydroxide, characterized in that, Includes the following steps: Strontium and iron sources were completely dissolved in deionized water, and NaOH solution was added to adjust the pH to alkaline to form a suspension. The suspension was then transferred to a hydrothermal reactor, sealed, and subjected to a hydrothermal reaction. After the reaction was completed, the suspension was allowed to cool naturally, centrifuged, washed until the filtrate was neutral, and dried to obtain Fe-Sr double hydroxide.

2. The method for preparing Fe-Sr double hydroxide according to claim 1, characterized in that, The strontium source and iron source are strontium chloride and ferric chloride, respectively.

3. The method for preparing Fe-Sr double hydroxide according to claim 2, characterized in that, The molar ratio of strontium chloride, ferric chloride, and NaOH is 1:2:

8.

4. The method for preparing Fe-Sr double hydroxide according to claim 1, characterized in that, The hydrothermal reaction temperature is 120℃, and the reaction time is 12h.

5. The Fe-Sr double hydroxide prepared according to the preparation method of any one of claims 1-4.

6. The application of the Fe-Sr double hydroxide according to claim 5 in the photo-Fenton reaction degradation of organic dye pollutants.

7. The application according to claim 6, characterized in that, The organic dye pollutant mentioned is methylene blue.

8. The application according to claim 7, characterized in that, The method is as follows: Fe-Sr double hydroxide and hydrogen peroxide are added to a methylene blue solution, and a photo-Fenton degradation reaction is carried out under simulated sunlight conditions to catalyze the degradation of methylene blue.

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