A kind of promote Fe 3+ Reduced cocatalyst and method of making same

Abstract

This invention provides a method to promote Fe in the application of electro-Fenton. 3+ This invention relates to a reduction co-catalyst and its preparation method, and pertains to wastewater treatment. Sodium molybdate, thiourea, and coal gasification fine slag are uniformly dispersed in deionized water at a mass ratio of (0.30–2.5):(1.5–3.5) to obtain a mixed system. The mixed system is then subjected to heat treatment at 120–180°C. After thermal decomposition, sodium molybdate undergoes a reduction reaction with thiourea to obtain nanosheet-like clusters of molybdenum sulfide, yielding a reaction solution. The precipitate in the reaction solution is microwave-dried and then freeze-dried to obtain Fe, which promotes the application of electro-Fenton catalysts. 3+ The reducing co-catalyst can promote the reduction of Fe by utilizing the valence state change of molybdenum ions dissolved in solution and the unsaturation of sulfur. 3+ The reduction process enhances the Fenton reaction, generating strong oxidizing free radicals to treat organic wastewater.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment, specifically to a method for promoting Fe in the electro-Fenton process. 3+ The reduction co-catalyst and its preparation method. Background Technology

[0002] Electro-Fenton (EF) technology is a novel electrochemical advanced oxidation technology based on Fenton chemical reactions that has emerged in water treatment in recent years. EF uses electrical energy as a driving force to produce H₂O₂ in situ through the cathode oxygen reduction reaction (ORR), which in turn induces the generation of ·OH. It boasts advantages such as high oxidation efficiency, environmental friendliness, and controllability, making it a new technology for the efficient treatment of recalcitrant organic pollutants. The basic principle of EF, driven by electrical energy, is that dissolved oxygen on the surface of a suitable cathode material undergoes a two-electron oxygen reduction reaction to produce hydrogen peroxide (H₂O₂). The generated H₂O₂ can then react with Fe in the solution... 2+ The catalytic reaction generates a strong oxidizing agent, the hydroxyl radical (·OH), as shown in the following reaction equation:

[0003] H2O2 + Fe 2+ →Fe 3+ +·OH+OHˉ

[0004] EF removes recalcitrant organic matter by utilizing the non-selective strong oxidizing power of ·OH. It has advantages such as high oxidation efficiency, being green, and controllable, making it one of the most promising technologies for the efficient treatment of organic matter in water.

[0005] The divalent and trivalent cycles of iron ions play an important role in the generation of ·OH. 3+ +eˉ→Fe 2+ Fe 3+ Reduced to Fe 2+ The H2O2 catalysis process converts the hydrogen to OH, but in actual reactions, most EF cathodes have hydrophobic interfacial properties, which is unfavorable for Fe. 2+ The recycling and regeneration of Fe 3+ The reduction rate is low, and the treatment system is limited by the pH range (2-3). These factors are the main factors that restrict the treatment efficiency and application of this technology.

[0006] Currently, methods to enhance the regeneration of ferrous iron in electro-Fenton systems mainly include the addition of reducing agents (chelate ligands), heterogeneous metallic materials (due to the slow Fenton reaction rate and difficult recovery), and ultraviolet radiation. However, these methods are costly and prone to secondary pollution, and the Fe... 3+ The low reduction efficiency results in a lack of significant improvement in the processing effect of this technology. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method to promote Fe in the application of electro-Fenton. 3+ The reduction co-catalyst and its preparation method solve the problems of high cost, easy secondary pollution, and Fe in the ferrous iron recycling regeneration of enhanced electro-Fenton systems. 3+ The problem of low reduction efficiency was effectively addressed by promoting Fe... 3+ The cycle and the Fenton reaction proceed.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method to promote Fe in the application of electric Fenton 3+ The method for preparing the reducing co-catalyst includes the following steps:

[0010] S1, sodium molybdate, thiourea and coal gasification fine slag are uniformly dispersed in deionized water, with the mass ratio of sodium molybdate to thiourea being (0.30-2.5):(1.5-3.5), to obtain a mixed system;

[0011] S2, the mixed system is kept at 120-180℃, and sodium molybdate undergoes a reduction reaction with thiourea after thermal decomposition to obtain molybdenum sulfide in the form of nanosheet clusters, and the reaction solution is obtained.

[0012] S3, the deposits in the reaction solution are microwave-dried and then freeze-dried to obtain Fe that promotes the application of electro-Fenton. 3+ A reducing co-catalyst.

[0013] A further improvement of the present invention is that:

[0014] The mass ratio of sodium molybdate to coal gasification slag in S1 is (0.30-2.5):(0.5-4).

[0015] S1 First, sodium molybdate and coal gasification fine slag are uniformly dispersed in deionized water to obtain mixed system a. Then, thiourea, citric acid aqueous solution and isopropanol are added and mixed evenly to obtain mixed system a.

[0016] S2 keeps the mixture at 120-180℃ for 4-8 hours to obtain the reaction solution.

[0017] S2 First, centrifuge the reaction solution, then remove the supernatant, and finally microwave dry it at 500-1500W.

[0018] The microwave drying is carried out under the condition of introducing N2, with a flow rate of 2-15 L / min.

[0019] The microwave drying process is carried out at 60-120℃ for 20-40 minutes.

[0020] The power consumption for S3 freeze drying is 500-1200W.

[0021] The freeze-drying described in S3 is carried out at -20 to -10°C for 10-30 minutes.

[0022] A method for promoting the application of Fe in the electro-Fenton process as described in any one of the above. 3+ The preparation method of the reduction co-catalyst obtained to promote the application of Fe in the electro-Fenton process 3+ The reduction co-catalyst is a porous nanosphere structure with a specific surface area of ​​1200-2500 g / cm³. 2 The porosity is 65%-85%, and the pore volume is 0.12-0.30 g / cm³. 3 .

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] This invention provides a method to promote Fe during the application of electro-Fenton. 3+ The preparation method of the reduction co-catalyst involves the thermal decomposition of sodium molybdate at 120-180℃ followed by a reduction reaction with thiourea to obtain molybdenum sulfide in the form of nanosheet clusters. Channels exist between the sheets. Different temperatures can adjust the particle size and interlayer spacing of the molybdenum sulfide. Excessive temperature will cause the collapse of the molybdenum sulfide sheet structure. Coal gasification slag has a porous structure. Through microwave radiation, molybdenum sulfide can be loaded onto the inside and outside of the pores of the fine coal gasification slag, encapsulating it to form a solid solution and a porous spherical structure. Subsequent freeze-drying yields a heterogeneous catalyst. The catalyst can promote the reduction of Fe by utilizing the valence state change of molybdenum ions dissolved in the solution and the unsaturation of sulfur. 3+ The reduction process enhances the Fenton reaction, generating strong oxidizing free radicals to treat organic wastewater. The electro-Fenton system containing this heterogeneous catalyst exhibits good treatment effects in acidic, neutral, and alkaline wastewater. This invention fully utilizes the molybdenum sulfide formed by the thermal decomposition of sodium molybdate and thiourea to release molybdenum ions, promoting the cycling of ferrous ions. Furthermore, it uses unsaturated sulfur atoms to regulate the solution pH, thus promoting the Fenton reaction. This invention employs coal gasification slag, a solid waste product from coal gasification heating. On one hand, its high specific surface area and porous structure are used to load and control the surface morphology of the molybdenum sulfide co-catalyst. On the other hand, it achieves high-value utilization of coal-based solid waste, reducing solid waste accumulation and realizing its resource-based treatment. This invention allows for the preparation of the co-catalyst using simple equipment, is easy to operate, and can be industrially promoted and applied. This makes EF a highly effective, economical, efficient, and environmentally friendly method for treating organic wastewater, and has significant theoretical and practical implications for promoting the industrial application of electro-Fenton technology.

[0025] The cocatalyst obtained by this invention has a porous nanosphere structure with a specific surface area of ​​1200-2500 g / cm³. 2The porosity is 65%-85%, and the pore volume is 0.12-0.30 g / cm³. 3 It can be used in EF systems, effectively improving EF treatment efficiency and enabling effective removal of pollutants under acidic, neutral, and alkaline conditions. The co-catalyst effectively improves the reduction efficiency of ferric iron to ferrous iron in EF systems. The surface structure of the co-catalyst remains stable before and after use, facilitating repeated use. Attached Figure Description

[0026] Figure 1 This is an electron microscope scan of the surface of the cocatalyst material prepared in Example 1 of the present invention.

[0027] Figure 2 The graph shows the EF treatment efficiency of organic wastewater using the co-catalyst prepared in Example 1 of this invention and the system without co-catalyst.

[0028] Figure 3 The figure shows the cyclic iron ion concentration of the co-catalyst prepared in Example 2 of this invention and the system without co-catalyst.

[0029] Figure 4 This is a comparison chart showing the treatment rate of organic wastewater by the co-catalyst prepared in Example 2 of the present invention under different pH conditions.

[0030] Figure 5 The images show X-ray diffraction patterns of the co-catalyst prepared in Example 3 of this invention before and after wastewater treatment. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0032] This invention provides a method to promote Fe during the application of electro-Fenton. 3+ The preparation method of the reduction co-catalyst is carried out according to the following steps:

[0033] Step 1: Weigh 0.30-2.5g of sodium molybdate and 0.5-4g of coal gasification fine slag, and ultrasonically disperse them in 50-100mL of deionized water to obtain a mixed system;

[0034] Step 2: Weigh 1.5-3.5g of thiourea, 4-10ml of citric acid aqueous solution and isopropanol and add them to the mixture in Step 1. Stir for 10-20 minutes. The volume ratio of citric acid aqueous solution to isopropanol is 30%:70% and the mass fraction of citric acid aqueous solution is 60%.

[0035] Step 3: Transfer the mixture obtained in Step 2 into a high-pressure reactor, set the temperature to 120-180℃, and the time to 4-8 hours;

[0036] Step 4: Place the reaction solution from Step 3 into a centrifuge, set the centrifugation speed to 2000-5000 rpm / min, and the centrifugation time to 5-10 minutes;

[0037] Step 5: Remove the supernatant, place the sediment in a microwave drying oven with a power of 500-1500W, introduce N2 at a flow rate of 2-15L / min, set the temperature to 60-120℃, and dry for 20-40 minutes. Then quickly place it in a freeze-drying oven with a power of 500-1200W, a drying temperature of -20 to -10℃, and a drying time of 10-30 minutes to obtain the nano-spherical cocatalyst material prepared in this invention.

[0038] The coal gasification slag is a solid waste emitted from the high-temperature gasification process in a coal gasification furnace at a thermal power plant in Yulin, Shaanxi Province. The specific surface area of ​​the catalyst material is 1200-2500 g / cm³. 2 The porosity is 65%-85%, and the pore volume is 0.12-0.30 g / cm³. 3 .

[0039] This invention also provides an effective method for treating organic wastewater, using commonly available carbon-based materials as cathodes (such as carbon felt, activated carbon fiber, carbon cloth, and graphite felt) (with an area of ​​20-200 cm²). 2 Using commercially available metal-coated stabilizing electrodes as anodes (DSA) (area 20-200 cm²) 2 Add ferrous sulfate (0.2-5 mmol) and the co-catalyst prepared in this invention (2-25 mg) to 50-1000 mL of organic wastewater. After electro-Fenton treatment, the removal rate of organic pollutants can reach 85-98% within 10-30 minutes, and good removal can be achieved at pH 3, 4, 5, 7 and 9. At the same time, due to the magnetic properties of iron and mineral components in the coal gasification slag, the co-catalyst is recyclable, which improves the effect of electro-Fenton water treatment technology and has important practical significance for the industrial application and promotion of electro-Fenton technology.

[0040] Example 1

[0041] Step 1: Weigh 0.35g of sodium molybdate and 1.0g of coal gasification fine slag, and ultrasonically disperse them in 55mL of deionized water;

[0042] Step 2: Weigh 1.5g of thiourea and slowly add it to the mixture obtained in Step 1, and stir for 10 minutes;

[0043] Step 3: Add 4 ml of citric acid aqueous solution and isopropanol to the mixture obtained in Step 2, wherein the volume ratio of citric acid aqueous solution to isopropanol is 30%:70%, and the mass fraction of citric acid aqueous solution is 60%.

[0044] Step 4: Place the mixture obtained in the above steps into a high-pressure reactor, set the temperature to 120℃, and the time to 4 hours;

[0045] Step 5: Transfer the reaction solution after step 4 to a centrifuge, set the centrifugation speed to 2000 rpm / min, and the centrifugation time to 5 minutes;

[0046] Step 6: Remove the supernatant, place the sediment in a microwave drying oven with a power of 1000W, introduce N2 at a flow rate of 4L / min, set the temperature to 80℃, and dry for 20 minutes. Then quickly place it in a freeze-drying oven with a power of 1000W, a drying temperature of -10℃, and a drying time of 10 minutes to obtain the cocatalyst material prepared in this invention.

[0047] Surface morphology of the co-catalyst, such as Figure 1 As shown, the porous nanosphere structure can regulate the dissolution of metal ions and effectively catalyze reactions. The specific surface area of ​​the co-catalyst material is 1200 g / cm³. 2 The porosity is 65%, and the pore volume is 0.15 g / cm³. 3 .

[0048] The co-catalyst prepared by this invention can improve the treatment effect of the Fenton reaction on phenol-containing organic wastewater discharged from a chemical plant. For example... Figure 2 As shown, the COD removal rate of the catalyst-assisted system reached 100% within 30 minutes, while that of the system without catalyst was 33%. Specifically, a carbon felt cathode (with an area of ​​40 cm²) was used. 2 Using a metal-coated shaped stable electrode as the anode (40cm) 2 The mixture was treated with ferrous sulfate catalyst (0.4 mmol) and the co-catalyst prepared in this invention (10 mg). After treatment with this invention, the COD removal rate reached 85% within 30 minutes, which is 2.5 times that of the system without the co-catalyst.

[0049] The cocatalyst prepared in this invention can effectively improve Fe 2+ The generated wastewater is recycled. The co-catalyst prepared by this invention can rapidly and efficiently treat organic wastewater under acidic, neutral, and alkaline conditions. The co-catalyst prepared by this invention can be recovered and reused multiple times.

[0050] Example 2

[0051] Step 1: Weigh 0.40g of sodium molybdate and 0.80g of coal gasification fine slag, and ultrasonically disperse them in 70mL of deionized water;

[0052] Step 2: Weigh 2g of thiourea and slowly add it to the mixture obtained in Step 1, and stir for 15 minutes;

[0053] Step 3: Add 5 ml of citric acid aqueous solution and isopropanol to the mixture obtained in Step 2, wherein the volume ratio of citric acid aqueous solution to isopropanol is 30%:70%, and the mass fraction of citric acid aqueous solution is 60%.

[0054] Step 4: Transfer the mixture obtained in the above steps into a high-pressure reactor, set the temperature to 120℃, and the time to 5 hours;

[0055] Step 5: Place the reaction solution from Step 4 into a centrifuge, set the centrifugation speed to 3000 rpm, and the centrifugation time to 6 minutes.

[0056] Step 6: Remove the supernatant, place the sediment solution in a microwave drying oven with a power of 1200W, introduce N2 at a flow rate of 5L / min, set the temperature to 80℃, and dry for 25 minutes. Then quickly place it in a freeze-drying oven with a power of 1000W, a drying temperature of -12℃, and a drying time of 15 minutes to obtain the cocatalyst material prepared in this invention.

[0057] The specific surface area of ​​the co-catalyst material is 1500 g / cm². 2 The porosity is 72%, and the pore volume is 0.20 g / cm³. 3 .

[0058] The co-catalyst prepared by this invention can improve the treatment efficiency of organic wastewater by electro-Fenton technology. The co-catalyst prepared by this invention can effectively increase Fe... 2+ The cycle is generated. For example... Figure 3 As shown, in the co-catalyst system, at a reaction time of 5 min, Fe 2+ The concentration began to rise again, 20 min Fe 2+ The concentration reached the same level as the amount added, but no co-catalyst was added to the system, Fe 2+ The concentration continued to decrease, indicating poor iron cycling performance.

[0059] The co-catalyst prepared by this invention can effectively treat organic wastewater under acidic, neutral, and alkaline conditions. For example... Figure 4 As shown, the electro-Fenton treatment technology with added co-catalyst can effectively remove COD at pH 3, 4, 5, 7, and 9. Compared with the system without added co-catalyst, the COD removal efficiency and removal rate are significantly improved, and the treatment rate (Kmin) is [not specified]. -1 It can increase by up to 7-8 times.

[0060] The co-catalyst prepared by this invention can be recycled and reused multiple times.

[0061] Example 3

[0062] Step 1: Weigh 1.5g of sodium molybdate and 2.0g of coal gasification fine slag, and ultrasonically disperse them in 85mL of deionized water;

[0063] Step 2: Weigh 2.5g of thiourea and slowly add it to the mixture obtained in Step 1, and stir for 18 minutes;

[0064] Step 3: Add 6 ml of citric acid aqueous solution and isopropanol to the mixture obtained in Step 2, wherein the volume ratio of citric acid aqueous solution to isopropanol is 30%:70%, and the mass fraction of citric acid aqueous solution is 60%.

[0065] Step 4: Transfer the mixture obtained in the above steps into a high-pressure reactor, set the temperature to 150℃, and the time to 5.5 hours;

[0066] Step 5: Place the reaction solution from Step 4 into a centrifuge, set the centrifugation speed to 3800 rpm / min, and the centrifugation time to 8 minutes;

[0067] Step 6: Remove the supernatant, place the sediment solution in a microwave drying oven with a power of 1300W, introduce N2 at a flow rate of 6L / min, set the temperature to 85℃, and dry for 24 minutes. Then quickly place it in a freeze-drying oven with a power of 1000W, a drying temperature of -15℃, and a drying time of 15 minutes to obtain the cocatalyst material prepared in this invention.

[0068] The specific surface area of ​​the co-catalyst material prepared by this invention is 1800 g / cm². 2 The porosity is 72%, and the pore volume is 0.23 g / cm³. 3 .

[0069] The co-catalyst prepared by this invention can improve the COD treatment effect of the Fenton reaction on organic wastewater discharged from a chemical plant. 2+ The wastewater is generated in a cycle. The co-catalyst prepared by this invention can rapidly and efficiently treat organic wastewater under acidic, neutral, and alkaline conditions. The co-catalyst prepared by this invention can be recovered and reused multiple times. Figure 5 As shown, X-ray scanning of the co-catalyst before use and after 20 consecutive runs revealed that its elemental composition and structure remained stable, indicating that the co-catalyst prepared by this invention has good performance in treating organic wastewater and can be reused multiple times. The co-catalyst prepared by this invention saves raw materials and is suitable for industrial application.

[0070] In summary, the method for preparing the co-catalyst of this invention is simple, and Fe 3+ It has high reduction efficiency, expands the pH range of EF technology, and can efficiently and stably treat organic wastewater.

Claims

1. A method to promote Fe in the application of electro-Fenton. 3+ A method for preparing a reducing co-catalyst, characterized in that, Includes the following steps: S1. First, sodium molybdate and coal gasification fine slag are uniformly dispersed in deionized water to obtain mixed system a. Then, thiourea, citric acid aqueous solution and isopropanol are added and mixed evenly. The mass ratio of sodium molybdate to thiourea is (0.30-2.5):(1.5-3.5), and the mass ratio of sodium molybdate to coal gasification fine slag is (0.30-2.5):(0.5-4) to obtain the mixed system. S2, the mixture is kept at 120-180 ℃ for 4-8 hours to obtain the reaction solution; S3. First, centrifuge the reaction solution, then remove the supernatant. The resulting precipitate is microwave-dried at 500-1500 W and 60-120 °C for 20-40 min, with N2 introduced at a flow rate of 2-15 L / min. Then, it is freeze-dried at -20 to -10 °C for 10-30 min at 500-1200 W to obtain Fe, which promotes the application of electro-Fenton. 3+ The reduction co-catalyst is a porous nanosphere structure with a specific surface area of ​​1200-2500 g / cm³. 2 The porosity is 65%-85%, and the pore volume is 0.12-0.30 g / cm³. 3 .

2. A method for promoting the application of Fe in the electro-Fenton process as described in claim 1 3+ The preparation method of the reduction co-catalyst obtained to promote the application of Fe in the electro-Fenton process 3+ A reducing co-catalyst.

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