A method of photocatalytic reduction of Cr(VI) based on an organic hybrid indium tin selenide catalyst

Abstract

The application relates to a method for photocatalytic reduction of Cr(VI) based on an organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 (Se4)2 as a catalyst for photocatalytic reduction of Cr(VI), belonging to the technical field of photocatalysis and heavy metal ion wastewater treatment. The application uses organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 (Se4)2 as a catalyst for photocatalysis. The material exhibits high photocatalytic activity in an acidic environment with pH=3, reduces Cr(VI) in wastewater into Cr(III), and has good reusability and cycle stability. Compared with other catalysts, the reduction rate is 26.3, 10.8 and 7.1 times that of P25, In2Se3 and SnSe2 respectively. Under sunlight irradiation, the material also shows good photocatalytic performance for Cr(VI) reduction.

Description

Technical Field

[0001] This invention relates to an organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 The method of photocatalytic reduction of Cr(VI) using (Se4)2 catalyst belongs to the field of photocatalysis and heavy metal ion wastewater treatment technology. Background Technology

[0002] Chromium salts, as a major series of products in my country's inorganic chemical industry, are widely used in electroplating, metallurgy, leather, paint, dyes, textiles, wood preservation, printing, and other fields. However, the emission of Cr(VI) can cause various adverse health effects and lead to serious ecological and environmental problems. Cr(VI) is a common and typical heavy metal pollutant in water bodies. Due to its relatively stable existence in water and its strong migration and diffusion capabilities, it poses a significant threat to the safety of the aquatic environment. Cr(VI) is usually present as an acid radical (Cr₂O₇). 2- / CrO4 2- / HCrO4 - Chromium exists in the form of chromium, and is a highly toxic substance, one of the eight most harmful chemical substances to the human body. It easily enters the human body, leading to cancer, deformities, gene mutations, and other problems, and also poses a persistent danger to the environment. Currently, my country has designated hexavalent chromium as one of the indicators subject to total quantity control; the content of hexavalent chromium in industrial wastewater cannot exceed 0.5 mg / L, and the chromium content in drinking water cannot exceed 0.05 mg / L.

[0003] Therefore, how to treat Cr(VI) wastewater simply, effectively, and at low cost has become a hot topic of common concern in academia and industry. Among these methods, photocatalytic reduction is a promising approach, aligning with the sustainable development trend of our times. It utilizes renewable solar energy to reduce Cr(VI) to Cr(III) at room temperature by using a semiconductor photocatalyst excited by light to generate photoelectrons. Furthermore, the photocatalyst can be recycled multiple times without generating secondary pollution, requires no other reducing agents, and is easy to operate. However, the key to the practical application of photocatalysts lies in developing highly active, highly stable, low-toxicity, long-lived, and inexpensive visible light-responsive photocatalysts. Summary of the Invention

[0004] The technical problem solved by this invention is to propose an organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 The method of using (Se4)2 as a photocatalyst for the reduction of Cr(VI) was successfully implemented. Under the reaction conditions of 1 g / L catalyst, pH 3, and 100 mg / L K2Cr2O7 solution, the reduction rate of Cr(VI) was 100% within 50 min, with a reduction rate constant of 0.0922 min.-1 The catalyst achieves a photocatalytic reduction of Cr(VI) of 2.0 mg / (g·min) per gram. Compared to other catalysts, its reduction rate is 26.3, 10.8, and 7.1 times that of P25, In2Se3, and SnSe2, respectively. After 5 cycles, the catalyst maintains a Cr(VI) reduction rate of over 97%, demonstrating good reusability and stability. Compared to other traditional pure inorganic catalysts, the organic hybrid indium tin selenide (Bmmim)8In8Sn8Se... 30 (Se4)2 has significant advantages as a photocatalyst for the catalytic reduction of Cr(VI).

[0005] To solve the technical problem of this invention, the proposed technical solution is: a method based on organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 The method of using (Se4)2 as a catalyst for the photocatalytic reduction of Cr(VI), wherein the organic hybrid indium tin selenide photocatalyst material is (Bmmim)8In8Sn8Se. 30 (Se4)2 photocatalytically reduces Cr(VI) under pH=3 conditions.

[0006] Preferred, (Bmmim)8In8Sn8Se 30 The amount of (Se4)2 catalyst used is 1 g / L.

[0007] Preferably, the K2Cr2O7 solution is catalytically reduced at pH=3, with a K2Cr2O7 concentration of 100 mg / L.

[0008] Preferred, (Bmmim)8In8Sn8Se 30 The synthesis method of (Se4)2 is as follows: In powder (1.0 mmol, 0.115 g), Na2SnO3·3H2O (1.0 mmol, 0.267 g), Se powder (5.8 mmol, 0.460 g), (Bmmim)Cl (5.0 mmol, 0.960 g) and hydrazine hydrate (1 mL, 80% aqueous solution) are placed in a 20 mL polytetrafluoroethylene liner, mixed evenly, and sealed in a steel reactor; after heating and reacting at 150 °C for 6 days, the mixture is naturally cooled to room temperature. The product is washed several times with ethanol to obtain orange-red microcrystalline powder with a size of 10-50 μm.

[0009] Preferably, at pH=3, (Bmmim)8In8Sn8Se 30 When (Se4)2 is used as a catalyst at a dosage of 1 g / L, it can completely reduce 100 mg / L of Cr(VI) to Cr(III) within 50 minutes under visible light irradiation.

[0010] Beneficial effects

[0011] In photocatalytic materials, metal chalcogenides possess narrower band gaps than metal oxides, resulting in stronger absorption of visible light. Currently, the application of metal chalcogenides in the photocatalytic reduction of Cr(VI) mainly focuses on pure inorganic metal chalcogenides. The chemical structures of inorganic metal chalcogenides are often quite dense, necessitating the fabrication of these materials into various nanostructures to expose more active sites and ensure efficient catalytic activity. Unlike inorganic metal chalcogenides, crystalline organic hybrid metal chalcogenides possess richer structural chemistry due to the diverse combinations of organic ligands and metal chalcogenide fragments. The organic components in organic hybrid metal chalcogenides can act as structure-directing agents, inducing the metal-chalcogenide components to form more complex spatial structures. By altering the spatial structure, the band structure of the material can be effectively controlled, thereby improving its photocatalytic performance. Therefore, organic hybrid metal chalcogenides have broad application prospects in the field of photocatalysis. For example, they have demonstrated unique advantages in areas such as photocatalytic degradation of organic dyes and photocatalytic hydrogen production. However, there are few reports on the use of organic hybrid metal chalcogenides for photocatalytic reduction of Cr(VI).

[0012] This invention discloses a method for photocatalytic reduction of Cr(VI) based on an organic hybrid indium tin selenide catalyst, belonging to the field of photocatalysis and heavy metal ion wastewater treatment technology. This invention utilizes the organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 (Se4)2 was used as a photocatalyst. Compared with other catalysts, its reduction rate was 26.3, 10.8, and 7.1 times that of P25, In2Se3, and SnSe2, respectively. This product exhibited highly efficient photocatalytic activity in acidic environments. At pH=3, it could completely reduce 100 mg / L Cr(VI) within 50 minutes; and reduce 200 mg / L Cr(VI) by 67.2% within 50 minutes. Furthermore, the material maintained high catalytic activity in tap water, lake water, river water, and sunlight environments. It demonstrated high cycling stability in 5-cycle tests. The synthesis method of this material is also relatively simple. Figure 11 The product demonstrated high catalytic activity under sunlight.

[0013] Figure 5 The catalytic activity of the product under acidic, neutral, and alkaline conditions was demonstrated. At pH 3, 50 mg / L of Cr(VI) was completely reduced within 5 minutes. After 40 minutes of illumination, the reduction rates of Cr(VI) in the solution were 92.2%, 84.7%, 60.9%, and 46.0%, respectively, at solution pH values ​​of 4, 5.6, 7, and 9.

[0014] Figure 6The product's catalytic reduction activity for different concentrations of Cr(VI) in an acidic environment was demonstrated. The material can completely reduce 50 mg / L of Cr(VI) within 5 minutes, completely reduce 100 mg / L of Cr(VI) within 50 minutes, and reduce 200 mg / L of Cr(VI) by 67.2% within 50 minutes. Attached Figure Description

[0015] Figure 1 Organic hybrid indium tin selenide (Bmmim)8In8Sn8Se was obtained as described in Example 1. 30 (Se4)2 physical image (a), XRD pattern (b), SEM image (cd).

[0016] Figure 2 The XRD pattern (a) and SEM image (bc) of In2Se3 obtained in Example 2 and the XRD pattern (d) and SEM image (ef) of SnSe2 obtained in Example 3 are shown.

[0017] Figure 3 This is a graph showing the photocatalytic reduction of Cr(VI) by different catalysts in an acidic environment (pH=3) in Example 5.

[0018] Figure 4 The first-order kinetic diagram is fitted to the photocatalytic Cr(VI) reduction performance curves of different catalysts in Example 5.

[0019] Figure 5 The graph shows the photocatalytic reduction of Cr(VI) in different acidic and alkaline environments (pH = 3, 4, 5, 6, 7 and 9) in Example 6.

[0020] Figure 6 This is a photocatalytic reduction curve of the product for different concentrations (50, 100, 150, 200 mg / L) of Cr(VI) in an acidic environment (pH=3) as shown in Example 7.

[0021] Figure 7 This is a graph showing the photocatalytic reduction of Cr(VI) at different product dosages (0, 20, 50, 80 mg) in an acidic environment (pH=3) in Example 8.

[0022] Figure 8 The graph shows the photocatalytic reduction curve of Cr(VI) by the product in 5 cycles of testing in Example 9.

[0023] Figure 9 The image shows the XRD patterns of the product before and after the cyclic reaction in Example 9, after 5 cycles of testing.

[0024] Figure 10Example 10 shows the photocatalytic reduction curves of the product on an acidic (pH=3) Cr(VI) solution (100 mg / L) in tap water, Nanjing Xuanwu Lake water, and Yangtze River water in Nanjing. Figure 11 The photocatalytic reduction curve of the product on an acidic (pH=3) Cr(VI) solution (100 mg / L) under sunlight conditions is shown in Example 11. Detailed Implementation

[0025] Example 1:

[0026] (Bmmim)8In8Sn8Se 30 Synthesis of (Se4)2: In powder (1.0 mmol, 0.115 g), Na2SnO3·3H2O (1.0 mmol, 0.267 g), Se powder (5.8 mmol, 0.460 g), (Bmmim)Cl (5.0 mmol, 0.960 g), and hydrazine hydrate (1 mL, 80% aqueous solution) were placed in a 20 mL polytetrafluoroethylene liner, mixed thoroughly, and sealed in a steel reactor. The mixture was heated at 150 °C for 6 days and then naturally cooled to room temperature. The product was washed several times with ethanol to obtain orange-red microcrystalline powder with a size of 10-50 μm.

[0027] Example 2:

[0028] Synthesis of In₂Se₃: InCl₃ (1.6 mmol, 0.354 g) was weighed and dissolved in a beaker containing 30 ml of H₂O. After complete dissolution, Se powder (2.4 mmol, 0.190 g) was added and stirred thoroughly. Then, 30 ml of ethylenediamine was added, and the mixture was stirred for 15 min. The mixture was then transferred to a 100 ml reactor and reacted at 180 °C for 24 h. After natural cooling to room temperature, the product was removed, washed four times with water and ethanol, and dried at 50 °C for 8 h to obtain a yellow product. The yellow product was placed in a magnetic boat and heated in a tube furnace under N₂ atmosphere from 30 °C to 500 °C at a heating rate of 5 °C / min and held for 2 h. After cooling to room temperature, black In₂Se₃ powder was obtained.

[0029] Example 3:

[0030] Synthesis of SnSe2: 1 mmol (0.351 g) of SnCl4·5H2O and 1 mmol (0.111 g) of SeO2 were weighed and added to a 200 ml beaker. Then, 85 ml of oleylamine and 2.5 ml of oleic acid were added sequentially. The mixture was heated to 70 °C and stirred for 30 min to ensure homogeneity. 10 ml of the homogeneous solution was added to a 25 ml reaction vessel and reacted at 180 °C for 36 h. After cooling to room temperature, the mixture was washed three times with a 1:2 (v / v) mixture of toluene and ethanol. The resulting SnSe2 black powder was obtained after drying in a 60 °C oven for 5 h.

[0031] Example 4:

[0032] The concentration of Cr(VI) in aqueous solution was analyzed using a diphenylcarbazide spectrophotometric method. The specific procedure was as follows: 1 mL of the supernatant was taken, and 0.5 mL of a 1:1 mixture of sulfuric acid and phosphoric acid was added. Then, 2 mL of the colorimetric reagent was added, mixed thoroughly, and allowed to stand for 10 min before UV-Vis absorption spectroscopy. The colorimetric reagent was prepared by dissolving 0.2 g of diphenylcarbazide in 50 mL of acetone solution. After complete dissolution, the solution was transferred to a 100 mL volumetric flask and diluted to 100 mL with water. The analysis was performed using a UV-Vis spectrophotometer. The maximum absorbance was obtained at λ = 540 nm. The reduction rate was calculated using the formula: η = C t / C0×100%, where C t C is the instantaneous concentration of the solution, and C0 is the initial concentration of the solution.

[0033] Example 5:

[0034] At room temperature, four 50 mL aliquots of a 100 mg / L K₂Cr₂O₇ solution (using deionized water) were taken, and their pH was adjusted to 3 using hydrochloric acid. 50 mg of (Bmmim)₈In₈Sn₈Se₂ prepared in Example 1 was weighed out. 30 (Se4)2, In2Se3 prepared in Example 2, SnSe2 prepared in Example 3, and commercially available P25 were added to the above solution. The mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was turned on, and the photocatalytic reduction of Cr(VI) was performed under visible light irradiation. 1 mL of the reaction solution was added to the colorimetric reagent prepared in Example 4, and the Cr(VI) concentration was analyzed using a UV-Vis spectrophotometer.

[0035] Figure 3 The (Bmmim)8In8Sn8Se obtained in Example 1 is shown. 30 (Se4)2 performs significantly better than In2Se3 obtained in Example 2 and SnSe2 obtained in Example 3, combined with Figure 4 The fitted first-order kinetic plot proves (Bmmim)8In8Sn8Se 30 (Se4)2 exhibits superior performance, with reduction rates 26.3, 10.8, and 7.1 times that of P25, In2Se3, and SnSe2, respectively.

[0036] Example 6:

[0037] At room temperature, five 50 mL aliquots of 50 mg / L K₂Cr₂O₇ solution (using deionized water) were taken, and their pH values ​​were adjusted to 3, 4, 5.6, 7, and 9, respectively, using dilute hydrochloric acid or sodium hydroxide solution. 50 mg of (Bmmim)₈In₈Sn₈Se₂O₇ prepared in Example 1 was weighed out. 30 (Se4)2 was added to the above solution, and the mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was turned on, and the photocatalytic reduction of Cr(VI) was carried out under visible light irradiation. 1 mL of the reaction solution was added to the colorimetric reagent prepared in Example 4, and the concentration of Cr(VI) was analyzed using a UV-Vis spectrophotometer.

[0038] Figure 5 The catalytic activity of the product under acidic, neutral, and alkaline conditions was demonstrated. At pH 3, 50 mg / L of Cr(VI) was completely reduced within 5 minutes. After 40 minutes of illumination, the reduction rates of Cr(VI) in the solution were 92.2%, 84.7%, 60.9%, and 46.0%, respectively, at solution pH values ​​of 4, 5.6, 7, and 9.

[0039] Example 7:

[0040] At room temperature, 50 mL of K₂Cr₂O₇ solutions (50, 100, 150, and 200 mg / L, respectively) were measured using deionized water as the solvent, and the pH was adjusted to 3 with hydrochloric acid solution. Subsequently, 50 mg of (Bmmim)₈In₈Sn₈Se prepared in Example 1 was added to each of the above solutions. 30 (Se4)2 was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was turned on, and the photocatalytic reduction of Cr(VI) was carried out under visible light irradiation. 1 mL of the reaction solution was added to the colorimetric reagent prepared in Example 4, and the Cr(VI) concentration was analyzed using a UV-Vis spectrophotometer.

[0041] Figure 6 The product demonstrated its catalytic activity in reducing different concentrations of Cr(VI) in an acidic environment. It can completely reduce 50 mg / L of Cr(VI) within 5 minutes, completely reduce 100 mg / L of Cr(VI) within 50 minutes, and reduce 200 mg / L of Cr(VI) by 67.2% within 50 minutes.

[0042] Example 8:

[0043] At room temperature, four 50 mL aliquots of 100 mg / L K₂Cr₂O₇ solution (using deionized water) were taken, and their pH was adjusted to 3 using hydrochloric acid solution. Different doses (0, 20, 50, and 80 mg) of (Bmmim)₈In₈Sn₈Se prepared in Example 1 were weighed out. 30 (Se4)2 was added to the above solution, and the mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was turned on, and the photocatalytic reduction of Cr(VI) was carried out under visible light irradiation. 1 mL of the reaction solution was added to the colorimetric reagent prepared in Example 4, and the concentration of Cr(VI) was analyzed using a UV-Vis spectrophotometer.

[0044] Example 9:

[0045] At room temperature, 50 mL of a 100 mg / L K₂Cr₂O₇ solution (using deionized water) was measured and its pH was adjusted to 3 with hydrochloric acid. 50 mg of (Bmmim)₈In₈Sn₈Se prepared in Example 1 was weighed. 30 (Se4)2 was added to the above solution, and the mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was then turned on, and the photocatalytic reduction of Cr(VI) was performed under visible light irradiation. 1 mL of the reacted solution was added to the colorimetric reagent prepared in Example 4, and the Cr(VI) concentration was analyzed using a UV-Vis spectrophotometer. The reacted (Bmmim)8In8Sn8Se 30 (Se4)2 was washed twice each with nitric acid solution (pH=2.8), water, and ethanol, and then dried. The dried product was then used to repeat the above process, which is the second cycle test. This process was repeated for a total of 5 cycles to verify the repeatability of the product performance. Figure 9 This demonstrates the product's excellent cycle stability.

[0046] Example 10:

[0047] At room temperature, 50 mL of a 100 mg / L K₂Cr₂O₇ solution (using tap water, water from Xuanwu Lake in Nanjing, and water from the Yangtze River near Nanjing, respectively) was taken and its pH was adjusted to 3 with hydrochloric acid solution. 50 mg of (Bmmim)₈In₈Sn₈Se prepared in Example 1 was weighed. 30 (Se4)2 was added to the above solution, and the mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. A 300W xenon lamp equipped with a 420nm filter was turned on, and the photocatalytic reduction of Cr(VI) was carried out under visible light irradiation. 1 mL of the reaction solution was added to the colorimetric reagent prepared in Example 4, and the concentration of Cr(VI) was analyzed using a UV-Vis spectrophotometer.

[0048] Figure 10 The product still exhibits high catalytic activity despite interference from various anions and cations in tap water, Xuanwu Lake water in Nanjing, and the Yangtze River water in Nanjing.

[0049] Example 11:

[0050] Take 50 mL of a 100 mg / L K₂Cr₂O₇ solution (using deionized water) and adjust its pH to 3 with hydrochloric acid. Weigh 50 mg of (Bmmim)₈In₈Sn₈Se prepared in Example 1. 30 (Se4)2 was added to the above solution, and the mixture was stirred in the dark for 2 hours to reach adsorption-desorption equilibrium. Subsequently, a photocatalytic reduction of Cr(VI) was performed under sunlight at an ambient temperature of 38°C. 1 mL of the reacted solution was added to the colorimetric reagent prepared in Example 4, and the Cr(VI) concentration was analyzed using a UV-Vis spectrophotometer. Figure 11 The product demonstrated high catalytic activity under sunlight.

Claims

1. A method based on organic hybrid indium tin selenide (Bmmim)8In8Sn8Se 30 A method for photocatalytic reduction of Cr(VI) using (Se4)2 as a catalyst, characterized in that: The organic hybrid indium tin selenide photocatalyst material is (Bmmim)8In8Sn8Se. 30 (Se4)2, photocatalytic reduction of Cr(VI) at pH = 3; (Bmmim)8In8Sn8Se 30 The synthesis method of (Se4)2 is as follows: In powder, Na2SnO3·3H2O, Se powder, (Bmmim)Cl and hydrazine hydrate are packed into a polytetrafluoroethylene liner, mixed evenly and sealed in a steel reactor; after heating and reacting at 150 °C for 6 days, the mixture is naturally cooled to room temperature, and the product is washed with ethanol several times to obtain orange-red microcrystalline powder with a size of 10-50 μm.

2. The organic hybrid indium tin selenide (Bmmim)8In8Sn8Se according to claim 1 30 A method for photocatalytic reduction of Cr(VI) using (Se4)2 as a catalyst, characterized in that: (Bmmim)8In8Sn8Se 30 The amount of (Se4)2 catalyst used is 1 g / L.

3. The organic hybrid indium tin selenide (Bmmim)8In8Sn8Se as described in claim 1 30 A method for photocatalytic reduction of Cr(VI) using (Se4)2 as a catalyst, characterized in that: The K2Cr2O7 solution was catalytically reduced at pH = 3, with a K2Cr2O7 concentration of 100 mg / L.

4. The organic hybrid indium tin selenide (Bmmim)8In8Sn8Se as described in claim 1 30 A method for photocatalytic reduction of Cr(VI) using (Se4)2 as a catalyst, characterized in that: (Bmmim)8In8Sn8Se 30 The synthesis method of (Se4)2 is as follows: 1.0 mmol In powder, 1.0 mmol Na2SnO3·3H2O, 5.8 mmol Se powder, 5.0 mmol (Bmmim)Cl and 1 mL of hydrazine hydrate in 80% aqueous solution are placed in a 20 mL polytetrafluoroethylene liner, mixed evenly and sealed in a steel reactor; after heating and reacting at 150 °C for 6 days, the mixture is naturally cooled to room temperature. The product is washed several times with ethanol to obtain orange-red microcrystalline powder with a size of 10-50 μm.

5. The organic hybrid indium tin selenide (Bmmim)8In8Sn8Se according to claim 1 30 A method for photocatalytic reduction of Cr(VI) using (Se4)2 as a catalyst, characterized in that: At pH = 3, (Bmmim)8In8Sn8Se 30 When (Se4)2 is used as a catalyst at a concentration of 1 g / L, it can completely reduce 100 mg / L of Cr(VI) to Cr(III) within 50 minutes under visible light irradiation.

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