A catalyst for hydrogen production from spontaneous decomposition of formaldehyde in wastewater and a preparation method and application thereof

Abstract

The present application belongs to the technical field of wastewater treatment, and particularly relates to a catalyst for hydrogen production by spontaneous decomposition of formaldehyde in wastewater, and a preparation method and application thereof. The preparation method comprises the following steps: high-temperature calcination of cobalt nitrate hexahydrate powder to obtain a cobalt tetraoxide precursor; reduction treatment of the precursor with a sodium borohydride solution to obtain cobalt tetraoxide containing oxygen vacancies; and loading of ruthenium on the surface of the cobalt tetraoxide containing oxygen vacancies by a constant-voltage deposition process, to obtain a cobalt tetraoxide containing oxygen vacancies loaded with ruthenium catalyst. The catalyst preparation process is simple, the conditions are mild, and the synthesis cycle is short. When the catalyst is added to wastewater containing formaldehyde, the catalyst can catalyze the efficient decomposition of formaldehyde and generate energy hydrogen at normal temperature and pressure for a long time. No additional oxidizing agent or energy input is required, and the simultaneous realization of pollutant degradation and clean energy recovery has a broad application prospect in the field of industrial wastewater treatment containing formaldehyde.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, its preparation method, and its application. Background Technology

[0002] Formaldehyde is a carcinogen, toxic and irritating. Even trace amounts can cause nasopharyngeal carcinoma and leukemia. However, formaldehyde is widely used as a chemical raw material in chemical, pharmaceutical and other fields. The widespread use of formaldehyde has accelerated water pollution. Therefore, it is urgent to develop effective wastewater treatment methods to solve the formaldehyde pollution problem.

[0003] Currently, traditional methods for treating formaldehyde-containing wastewater include advanced oxidation methods (such as wet oxidation, photocatalytic oxidation, and Fenton oxidation), biological treatment methods, and electrocatalytic methods. Among them, advanced oxidation methods usually require light and oxidants; biological treatment methods have long cycles and poor tolerance to high concentrations of formaldehyde; electrocatalytic methods require an external voltage to drive the reaction. The above traditional methods generally suffer from high operating costs, high energy consumption, and harsh operating conditions. The most promising method for treating formaldehyde wastewater is the catalyst method, which is spontaneous and does not require additional energy. However, it is still in the development stage, and the application of existing catalysts is still limited. For example, the copper catalyst and platinum-modified copper catalyst described in reference [1] can catalytically decompose formaldehyde in solution and generate hydrogen. However, whether it is pure copper or platinum-modified copper catalyst, in the process of catalytically decomposing formaldehyde, there are generally problems of low decomposition efficiency and short effective action time. The reason is that pure copper is easily passivated, and platinum-modified copper catalysts have fewer active sites.

[0004] Given that existing methods are insufficient for the low-cost, low-energy, and gentle treatment of formaldehyde-containing wastewater, there is an urgent need to develop a catalyst and preparation technology that can efficiently and gently treat formaldehyde in wastewater without the need for external oxidants or additional energy input, so as to achieve efficient purification and resource utilization of formaldehyde-containing wastewater.

[0005] [1] Chen W, Chen J, Ma C, et al. Synergistic Mechanism for Unconventional Anodic Reaction of Aldehyde Oxidation for Hydrogen Production[J]. Angewandte Chemie International Edition, 2025, 64(26): e202425258. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, its preparation method, and its application, thus solving the problems of high cost, high energy consumption, and harsh operating conditions in existing methods for formaldehyde wastewater treatment.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, comprising the following steps:

[0009] Step 1: Place cobalt nitrate hexahydrate powder in a porcelain boat and calcine it at a high temperature of 400~500 ℃ for two hours to obtain cobalt tetroxide precursor;

[0010] Step 2: The cobalt tetroxide precursor is dispersed in a sodium borohydride solution for chemical reduction treatment, washing and vacuum drying to obtain cobalt tetroxide containing oxygen vacancies;

[0011] Step 3: Dissolve ruthenium trichloride hydrate in phosphate buffer solution with a pH of 6 to prepare a ruthenium-containing solution with a concentration of 0.05 mol / L;

[0012] Step 4: Place the oxygen-vacant cobalt tetroxide in the ruthenium-containing solution, and load ruthenium onto the surface of the oxygen-vacant cobalt tetroxide using a constant voltage deposition method under a three-electrode system to obtain an oxygen-vacant cobalt tetroxide-supported ruthenium catalyst.

[0013] In the above technical solution, the heating rate of the high-temperature calcination is further 2~5 °C / min. -1 .

[0014] In the above technical solution, the concentration of the sodium borohydride solution is 0.1 mol / L, and the chemical reduction treatment time is 60 min.

[0015] In the above technical solution, the washing process further includes 4 to 6 water washes and alcohol washes, and the vacuum drying temperature is 60 to 80 ℃, and the drying time is 12 to 24 h.

[0016] In the above technical solution, the three-electrode system is further composed of cobalt tetroxide containing oxygen vacancies as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode.

[0017] In the above technical solution, the deposition potential of the constant voltage deposition method is -0.77 V, the reference for the deposition potential is a reversible hydrogen electrode, and the deposition time of the constant voltage deposition method is 5~25 min.

[0018] Secondly, the present invention provides a catalyst prepared by the above-mentioned method for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen.

[0019] Thirdly, the present invention provides an application of a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, characterized in that the catalyst prepared by the above method is added to formaldehyde-containing wastewater to decompose formaldehyde and obtain clean hydrogen gas at the same time.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The catalyst preparation process of the present invention is simple, the conditions are mild, the synthesis cycle is short and the efficiency is high.

[0022] (2) The catalyst of this invention can convert formaldehyde into hydrogen while decomposing formaldehyde in wastewater, combining pollutant degradation with clean energy production, which has significant economic and environmental benefits.

[0023] (3) The process of decomposing formaldehyde in wastewater by the catalyst of the present invention is spontaneous at normal temperature and pressure, without the need for external oxidant and energy input, with low energy consumption and simple operation.

[0024] (4) The catalyst of the present invention increases the number of active sites by introducing ruthenium and oxygen vacancies, thereby significantly improving the catalyst’s activity in decomposing formaldehyde, while making the catalyst less prone to passivation. Attached Figure Description

[0025] Figure 1 This is a morphology diagram of the catalyst in Example 1 of the present invention;

[0026] Figure 2 This is a gas chromatogram of the gas produced by the decomposition of formaldehyde in Example 1 of the present invention, wherein the characteristic peak at a retention time of 2.8 min corresponds to hydrogen gas. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0028] Example 1

[0029] Weigh 6 g of cobalt nitrate hexahydrate powder and place it in a porcelain boat. Transfer it to a muffle furnace and heat at 5 °C for 1 min. -1 The temperature was increased to 450 °C at a rate of 100 °C, and calcined at high temperature for two hours to obtain cobalt tetroxide precursor;

[0030] 200 mg of cobalt tetroxide precursor was dispersed in 40 mL of 0.1 mol / L sodium borohydride solution. After reacting for 60 min, the catalyst was washed with water and alcohol five times. The cleaned catalyst was placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain cobalt tetroxide containing oxygen vacancies.

[0031] Ruthenium trichloride hydrate was dissolved in phosphate buffer solution with a pH of 6 to prepare a ruthenium-containing solution with a concentration of 0.05 mol / L.

[0032] Take 12 mg of cobalt tetroxide containing oxygen vacancies, disperse it in 1000 μL of ethanol and 300 μL of deionized water, sonicate for 30 min, and after the sample is mixed evenly, drop it onto conductive glass. Use the conductive glass coated with cobalt tetroxide containing oxygen vacancies as the working electrode, the carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Place them together in a ruthenium-containing solution and deposit them at a constant voltage of -0.77 V (relative to the reversible hydrogen electrode) for 15 min to obtain a ruthenium catalyst supported on cobalt tetroxide containing oxygen vacancies.

[0033] Take 25 mL of 1 mol / L sodium hydroxide solution in a beaker, add 368 μL of 38% (mass fraction) formaldehyde aqueous solution to obtain wastewater with a formaldehyde concentration of 0.1 mol / L, add 10 mg of cobalt tetroxide supported ruthenium catalyst with oxygen vacancies prepared by the above method to the wastewater, and spontaneously react under normal temperature and pressure conditions.

[0034] After the catalyst was added, dense bubbles were immediately observed to form on the catalyst surface. The gas generated during the reaction was injected into a gas chromatograph for analysis. The chromatogram showed a distinct characteristic peak at a retention time of 2.8 min. After comparison with standard hydrogen, the gas was confirmed to be hydrogen. One hour later, the formaldehyde degradation rate in the wastewater reached 80%.

[0035] Example 2

[0036] Weigh 6 g of cobalt nitrate hexahydrate powder and place it in a porcelain boat. Transfer it to a muffle furnace and heat at 5 °C for 1 min. -1 The temperature was increased to 450 °C at a rate of 100 °C, and calcined at high temperature for two hours to obtain cobalt tetroxide precursor;

[0037] 200 mg of cobalt tetroxide precursor was dispersed in 40 mL of 0.1 mol / L sodium borohydride solution. After reacting for 60 min, the catalyst was washed with water and alcohol five times. The cleaned catalyst was placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain cobalt tetroxide containing oxygen vacancies.

[0038] Ruthenium trichloride hydrate was dissolved in phosphate buffer solution with a pH of 6 to prepare a ruthenium-containing solution with a concentration of 0.05 mol / L.

[0039] Take 12 mg of cobalt tetroxide containing oxygen vacancies, disperse it in 1000 μL of ethanol and 300 μL of deionized water, sonicate for 30 min, and after the sample is mixed evenly, drop it onto conductive glass. Use the conductive glass coated with cobalt tetroxide containing oxygen vacancies as the working electrode, the carbon rod as the counter electrode, and Hg / HgO as the reference electrode. Place them together in a ruthenium-containing solution and deposit them at a constant voltage of -0.77 V (relative to the reversible hydrogen electrode) for 15 min to obtain a ruthenium catalyst supported on cobalt tetroxide containing oxygen vacancies.

[0040] Take 25 mL of 1 mol / L sodium hydroxide solution in a beaker, and add 10 mg of cobalt tetroxide supported ruthenium catalyst with oxygen vacancies prepared by the above method. No bubbles can be observed on the surface of the catalyst under normal temperature and pressure conditions, which further confirms that the hydrogen in this invention is generated by the spontaneous decomposition of formaldehyde by the catalyst.

[0041] Example 3

[0042] Weigh 6 g of cobalt nitrate hexahydrate powder and place it in a porcelain boat. Transfer it to a muffle furnace and heat at 5 °C for 1 min. -1 The temperature was increased to 450 °C at a rate of 100 °C, and calcined at high temperature for two hours to obtain cobalt tetroxide precursor;

[0043] 200 mg of cobalt tetroxide precursor was dispersed in 40 mL of 0.1 mol / L sodium borohydride solution. After reacting for 60 min, the catalyst was washed with water and alcohol five times. The cleaned catalyst was placed in a vacuum drying oven and dried at 60 °C for 12 h to obtain cobalt tetroxide containing oxygen vacancies.

[0044] Take 25 mL of 1 mol / L sodium hydroxide solution in a beaker, add 368 μL of 38% (mass fraction) formaldehyde aqueous solution to obtain wastewater with a formaldehyde concentration of 0.1 mol / L, add 10 mg of cobalt tetroxide catalyst with oxygen vacancies prepared by the above method to the wastewater, and spontaneously react under normal temperature and pressure conditions.

[0045] The results show that the rate of bubble generation on the surface of the cobalt tetroxide catalyst with oxygen vacancies is slow, and the hydrogen production rate is lower than that in Example 1. This indicates that the combined effect of ruthenium loading and oxygen vacancies in this invention is the key to achieving spontaneous decomposition of formaldehyde and efficient hydrogen generation.

[0046] Example 4

[0047] Weigh 6 g of cobalt nitrate hexahydrate powder and place it in a porcelain boat. Transfer it to a muffle furnace and heat at 5 °C for 1 min.-1 The temperature was increased to 480 °C at a rate of 100 °C, and calcined at high temperature for two hours to obtain cobalt tetroxide precursor;

[0048] 200 mg of cobalt tetroxide precursor was dispersed in 40 mL of 0.1 mol / L sodium borohydride solution. After reacting for 60 min, the catalyst was washed with water and alcohol four times. The cleaned catalyst was placed in a vacuum drying oven and dried at 70 °C for 12 h to obtain cobalt tetroxide containing oxygen vacancies.

[0049] Ruthenium trichloride hydrate was dissolved in phosphate buffer solution with a pH of 6 to prepare a ruthenium-containing solution with a concentration of 0.05 mol / L.

[0050] 12 mg of cobalt tetroxide containing oxygen vacancies was dispersed in 1000 μL of ethanol and 300 μL of deionized water and sonicated for 30 min. After the sample was mixed evenly, it was dropped onto a conductive glass. The conductive glass coated with cobalt tetroxide containing oxygen vacancies was used as the working electrode, the carbon rod as the counter electrode, and Hg / HgO as the reference electrode. They were placed together in a ruthenium-containing solution and deposited at a constant voltage of -0.77 V (relative to the reversible hydrogen electrode) for 25 min to obtain a ruthenium catalyst supported on cobalt tetroxide containing oxygen vacancies.

[0051] Take 25 mL of 1 mol / L sodium hydroxide solution in a beaker, add 368 μL of 38% (mass fraction) formaldehyde aqueous solution to obtain wastewater with a formaldehyde concentration of 0.1 mol / L. Add 10 mg of cobalt tetroxide supported ruthenium catalyst with oxygen vacancies prepared by the above method to the wastewater. Bubbles were still observed on the catalyst surface under normal temperature and pressure conditions, and GC confirmed that the gas was hydrogen.

[0052] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, characterized in that, The preparation method includes the following steps: Step 1: Place cobalt nitrate hexahydrate powder in a porcelain boat and calcine it at a high temperature of 400~500 ℃ for two hours to obtain cobalt tetroxide precursor; Step 2: The cobalt tetroxide precursor is dispersed in a sodium borohydride solution for chemical reduction treatment, washing and vacuum drying to obtain cobalt tetroxide containing oxygen vacancies; Step 3: Dissolve ruthenium trichloride hydrate in phosphate buffer solution with a pH of 6 to prepare a ruthenium-containing solution with a concentration of 0.05 mol / L; Step 4: Place the oxygen-vacant cobalt tetroxide in the ruthenium-containing solution, and load ruthenium onto the surface of the oxygen-vacant cobalt tetroxide using a constant voltage deposition method under a three-electrode system to obtain an oxygen-vacant cobalt tetroxide-supported ruthenium catalyst.

2. The method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen according to claim 1, characterized in that, The heating rate for the high-temperature calcination is 2~5 °C / min. -1 .

3. The method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen according to claim 1, characterized in that, The concentration of the sodium borohydride solution is 0.1 mol / L, and the chemical reduction treatment time is 60 min.

4. The method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen according to claim 1, characterized in that, The washing process includes 4 to 6 water washes and alcohol washes, and the vacuum drying temperature is 60 to 80 ℃, with a drying time of 12 to 24 h.

5. The method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen according to claim 1, characterized in that, The three-electrode system consists of cobalt tetroxide with oxygen vacancies as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode.

6. The method for preparing a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen according to claim 1, characterized in that, The deposition potential of the constant voltage deposition method is -0.77 V, the reference for the deposition potential is a reversible hydrogen electrode, and the deposition time of the constant voltage deposition method is 5~25 min.

7. A catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

8. The application of a catalyst for the spontaneous decomposition of formaldehyde in wastewater to produce hydrogen, characterized in that, The catalyst described in claim 8 is added to formaldehyde-containing wastewater to decompose formaldehyde and obtain clean hydrogen gas.

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