A carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst and its preparation method and application

Abstract

The present invention relates to a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst and its preparation method and application. The catalyst raw materials include iron tourmaline powder, lees and cerium nitrate, wherein the mass percentage of the iron tourmaline powder is 50% to 80%. The catalyst has good catalytic activity, stability and recovery performance through carbon-nitrogen doping and the interaction between cerium dioxide and tourmaline, and is conducive to wide promotion in the field of water treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and particularly relates to a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst and a preparation method and application thereof. Background Art

[0002] Ozone catalytic oxidation technology is a process for efficiently treating difficult-to-degrade organic wastewater. This technology is to add a suitable catalyst to the ozone oxidation process to achieve the purpose of reducing the amount of ozone used, improving the oxidation treatment effect, and accelerating the reaction rate. At present, the fixed bed form is mainly used in engineering applications. However, the fixed bed form has difficult-to-solve original problems, such as the easy formation of channel flow and dead zones in the fixed bed, and only a small amount of catalyst can contact the sewage and ozone, making the catalytic effect of the fixed bed not significant. On the other hand, ozone bubbles are intercepted by the fixed bed catalyst during the rising process, and then merged into large bubbles, resulting in low ozone utilization and increased operating costs.

[0003] Therefore, in order to overcome the above problems, technicians in this field have developed a series of fluidized bed ozone catalytic oxidation processes. Fluidized bed processes generally use powder catalysts to overcome the original problems of fixed beds, but at the same time, the long-term catalytic effect, separation and recovery performance, and wear resistance of the catalyst have become new problems. The existing technology mainly recovers the catalyst through membrane separation or cyclone separation, which adds additional operating costs; on the other hand, the powder material used in the fluidized bed is not strong enough, especially in continuous operation, it will be broken, and the tiny powder is difficult to separate. On the one hand, it will cause secondary pollution to the water body, and on the other hand, the performance of the catalyst will also be affected.

[0004] For example, the paper "Catalytic ozonation of hard COD in coking wastewater with Fe2O3 / Al2O3-SiC: From catalyst design to industrial application" discloses a Fe2O3 / Al2O3-SiO2 catalyst with good long-term usability and wear resistance, but it requires cyclone separation as a separation method, which increases electricity costs and labor maintenance costs, and is not conducive to engineering application. Invention patent CN 114471664A discloses a preparation method of a wood-based carbon modified protonated carbon nitride / wood structure cerium dioxide photocatalytic material, designs and constructs a wood-based carbon modified protonated carbon nitride / wood structure cerium dioxide photocatalytic material, which has a large specific surface area and good thermal and chemical stability, and has good photocatalytic performance. However, the material is mainly composed of carbonaceous materials and cerium dioxide, and its wear resistance and strength are insufficient. It will break during long-term use, thus causing secondary pollution. Invention patent CN112979021B discloses a FeO / TiO2-tourmaline catalyst for catalytic ozone oxidation degradation of shale gas fracturing return fluid. However, the elemental iron component contained in the catalyst is reductive. After long-term use, oxides will form on the surface, resulting in a decrease in catalytic effect, hindering its further application in actual engineering.

[0005] In summary, there is an urgent need to develop an efficient ozone oxidation catalyst that is strong, reusable, can be easily separated without the need for additional energy, and does not produce secondary pollution. Summary of the invention

[0006] Based on this, in order to solve at least one technical problem existing in the prior art, the present invention proposes to provide a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, aiming to solve the technical problems of poor catalyst strength, insufficient performance, difficulty in separation and the risk of secondary pollution.

[0007] The invention provides a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, the raw materials of which include iron tourmaline powder, vinasse and cerium nitrate, wherein the mass percentage of the iron tourmaline powder is 50% to 80%.

[0008] The ozone oxidation catalyst of the present invention uses tourmaline as a base material, which improves wear resistance and facilitates precipitation and separation. In addition, tourmaline can generate a micro-electric field, thereby increasing the mass transfer rate of ozone from the gas phase to the liquid phase, and improving the catalytic oxidation effect and ozone utilization rate. In addition, the catalyst of the present invention also uses wine lees as a raw material to introduce carbon and nitrogen doping, which can establish an electron transfer bridge, increase the electron transfer rate between ozone molecules and catalysts, and increase the yield of active free radicals, thereby improving the removal rate of pollutants. In addition, cerium ions are introduced by cerium nitrate, Ce 4+ / Ce 3+ Fe contained in tourmaline 2+ / Fe 3+ The electron pairs are transferred and transmitted, which can ensure that the catalyst material has a long-term high-efficiency catalytic ability. Therefore, the catalyst of the present invention is highly efficient, wear-resistant, and has a long-term catalytic ability.

[0009] In one embodiment, the catalyst has a particle size of 100-150 mesh, has better sedimentation and wear resistance, and is more conducive to recovery.

[0010] Another aspect of the present invention also provides a method for preparing the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, comprising the following steps: fully grinding and mixing cerium nitrate, vinasse and iron tourmaline powder, roasting, grinding and screening to obtain the final product.

[0011] In one embodiment, the mass ratio of the cerium nitrate, the vinasse and the tourmaline powder is 10-50:15-50:100.

[0012] In one embodiment, the particle size of the tourmaline powder is in the range of 75 to 150 μm.

[0013] In one of the embodiments, the calcination temperature is 500° C. to 700° C., and the calcination time is 2 hours.

[0014] Another aspect of the present invention also provides the use of the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst in treating oxalic acid in sewage.

[0015] In one embodiment, the steps include:

[0016] S1. putting the obtained catalyst into the bottom of the reaction zone of the reactor, wherein the reactor further comprises a precipitation separation zone connected to the reaction zone, water first enters the reaction zone from the outside, then overflows from the top of the reaction zone to the bottom of the precipitation separation zone, and then rises and flows out of the reactor;

[0017] S2. The ozone is introduced into the reaction zone from the bottom through a titanium microporous aeration disk;

[0018] S3. Water is continuously introduced into and discharged from the reactor, and the catalyst precipitated at the bottom of the precipitation separation zone is recovered and returned to the reaction zone.

[0019] Through this method, the catalyst can be recycled to avoid secondary pollution of water bodies.

[0020] In one of the embodiments, the concentration of oxalic acid in the influent water is 100-300 mg / L; the concentration of the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst in the reaction zone is 0.5-1.5 g / L.

[0021] In one embodiment, the residence time of the influent water in the reaction zone is 60 to 90 minutes, the residence time in the sedimentation separation zone is 30 to 60 minutes, and the rising speed of the water flow in the sedimentation separation zone is 6 to 12 m / h.

[0022] Compared with the prior art, the ozone oxidation catalyst of the present invention has the following beneficial effects:

[0023] (1) The ozone oxidation catalyst uses tourmaline as a carrier. The Mohs strength of tourmaline is 7, which is much better than common metal oxides and activated carbon. Tourmaline as a catalyst carrier can greatly enhance the wear resistance of the catalyst, and its true density is large, which is easy to precipitate and separate;

[0024] (2) Tourmaline can spontaneously generate a micro-electric field, which can reduce the degree of association of water molecules, shrink the water molecule clusters, and greatly increase the speed of ozone mass transfer from the gas phase to the liquid phase, thereby improving the catalytic oxidation effect and ozone utilization rate;

[0025] (3) Carbon-nitrogen doping can establish a bridge for electron transfer, increase the rate of electron transfer between ozone molecules and catalysts, increase the yield of active free radicals, and thus improve the removal rate of pollutants. The present invention uses wine lees as a carbon source and a nitrogen source, which is different from other methods that use expensive chemicals as a nitrogen source. The catalyst is easy to prepare and has a low cost, which is conducive to wide promotion;

[0026] (4) Introduction of cerium ions, Ce 4+ / Ce 3+ Electron pairs and Fe contained in tourmaline 2+ / Fe 3+ The transfer of electron pairs can ensure that the catalyst material has long-term and efficient catalytic ability;

[0027] The ozone oxidation catalyst of the present invention has long-term high catalytic capacity, is easy to prepare, has low raw material cost, has good wear resistance, is easy to precipitate, separate and recycle, and is conducive to wide promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the reactor structure;

[0029] Figure 2 The comparison of catalyst particle changes before and after 30 consecutive days in Example 1 is shown below: Figure 2 a: Before use; Figure 2 b: After use;

[0030] Figure 3 This is a comparison chart of the catalytic degradation of oxalic acid in different experimental groups. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0033] The raw material cerium nitrate in the embodiment of the present invention is cerium nitrate hexahydrate, and the molecular formula is Ce(NO3)3·6H2O.

[0034] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the art can be used for the experiments; the materials used in the preparation process are all conventional reagent products that can be obtained commercially.

[0035] Example 1

[0036] A carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, the raw materials of which are composed of the following components: 10g of iron tourmaline powder, 3g of commercially available lees, and 5g of hexahydrated cerium nitrate, wherein the particle size of the iron tourmaline powder is 75μm. The preparation method thereof is as follows:

[0037] The above raw materials are weighed, ground and mixed evenly, and then vacuum calcined at 600° C. for 2 h. After grinding, the mixture is sieved to obtain particles with a size between 100 and 150 meshes; thus, a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst is obtained.

[0038] Place the prepared catalyst into Figure 1 At the bottom of the reaction zone of the reactor shown, the reactor includes a reaction zone and a sedimentation separation zone connected to the reaction zone. Water first enters the reaction zone from the outside, then overflows from the top of the reaction zone to the bottom of the sedimentation separation zone, and then rises and flows out of the reactor.

[0039] Ozone is introduced into the reaction zone from the bottom through a titanium microporous aeration disk; water can flow in and out of the reactor continuously, and the catalyst precipitated at the bottom of the precipitation separation zone is recovered to the reaction zone through a peristaltic pump.

[0040] Artificial simulated oxalic acid wastewater was used as the experimental wastewater, and the process was run in a continuous flow. The influent oxalic acid concentration was 200 mg / L, the catalyst dosage in the reaction zone was 1 g / L, the influent residence time in the reaction zone was 60 min, the residence time in the sedimentation separation zone was 30 min, and the water flow rate in the sedimentation separation zone was 12 m / h. The influent and effluent water of the reaction zone were respectively measured for total organic carbon concentration, and the influent and effluent water of the sedimentation separation zone were measured for SS concentration. In particular, the catalyst sample of Example 1 after continuous operation for 30 days was taken for particle size analysis.

[0041] Example 2

[0042] A carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, the raw materials of which are composed of the following components: 10g of tourmaline, 4g of commercially available lees, 4g of hexahydrated cerium nitrate, wherein the particle size of the iron tourmaline powder is 90μm. The preparation method thereof is as follows:

[0043] The above raw materials are weighed, ground and mixed evenly, and then vacuum calcined at 600° C. for 2 h. After grinding, the mixture is sieved to obtain particles with a size between 100 and 150 meshes; thus, a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst is obtained.

[0044] Place the prepared catalyst into Figure 1 At the bottom of the reaction zone of the reactor shown, the reactor includes a reaction zone and a sedimentation separation zone connected to the reaction zone. Water first enters the reaction zone from the outside, then overflows from the top of the reaction zone to the bottom of the sedimentation separation zone, and then rises and flows out of the reactor.

[0045] Ozone is introduced into the reaction zone from the bottom through a titanium microporous aeration disk; water can flow in and out of the reactor continuously, and the catalyst precipitated at the bottom of the precipitation separation zone is recovered to the reaction zone through a peristaltic pump.

[0046] Artificial simulated oxalic acid wastewater was used as the experimental wastewater, and it was operated in the form of continuous flow. The influent oxalic acid was 200 mg / L, the catalyst dosage was 1 g / L, the reaction zone residence time was 60 min, the sedimentation separation zone residence time was 30 min, and the water flow rising speed in the sedimentation separation zone was 12 m / h. The inlet and outlet water of the reaction zone were taken to measure their total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone were taken to measure their SS concentration.

[0047] Example 3

[0048] A carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst, the raw materials of which are composed of the following components: 10g tourmaline, 5g commercially available lees, 4g hexahydrated cerium nitrate, wherein the particle size of the iron tourmaline powder is 150μm. The preparation method thereof is as follows:

[0049] The above raw materials are weighed, ground and mixed evenly, and then vacuum calcined at 600° C. for 2 h. After grinding, the mixture is sieved to obtain particles with a size between 100 and 150 meshes; thus, a carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst is obtained.

[0050] Place the prepared catalyst into Figure 1 At the bottom of the reaction zone of the reactor shown, the reactor includes a reaction zone and a sedimentation separation zone connected to the reaction zone. Water first enters the reaction zone from the outside, then overflows from the top of the reaction zone to the bottom of the sedimentation separation zone, and then rises and flows out of the reactor.

[0051] Ozone is introduced into the reaction zone from the bottom through a titanium microporous aeration disk; water can flow in and out of the reactor continuously, and the catalyst precipitated at the bottom of the precipitation separation zone is recovered to the reaction zone through a peristaltic pump.

[0052] Artificial simulated oxalic acid wastewater was used as the experimental wastewater, and it was operated in the form of continuous flow. The influent oxalic acid was 200 mg / L, the catalyst dosage was 1 g / L, the reaction zone residence time was 60 min, the sedimentation separation zone residence time was 30 min, and the water flow rising speed in the sedimentation separation zone was 12 m / h. The inlet and outlet water of the reaction zone were taken to measure their total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone were taken to measure their SS concentration.

[0053] Comparative Example 1

[0054] This comparative example provides an ozone catalytic oxidant, the raw materials of which are composed of the following components: 10g of tourmaline. The preparation method thereof is as follows:

[0055] The product is vacuum calcined at 600° C. for 2 h, ground and sieved to obtain particles with a size between 100 and 150 meshes; and an ozone catalytic oxidant is obtained.

[0056] Place the prepared catalyst into Figure 1 The reactor shown uses artificial simulated oxalic acid wastewater as experimental wastewater and operates in the form of continuous flow. The influent oxalic acid is 200 mg / L, the catalyst dosage is 1 g / L, the reaction zone residence time is 60 min, the sedimentation separation zone residence time is 30 min, and the water flow rise rate in the sedimentation separation zone is 12 m / h. The inlet and outlet water of the reaction zone are taken to measure the total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone are taken to measure the SS concentration.

[0057] Comparative Example 2

[0058] This comparative example provides an ozone catalytic oxidant, the raw materials of which are composed of the following components: 10g of tourmaline and 3g of commercially available lees. The preparation method thereof is as follows:

[0059] The above raw materials are weighed, ground and mixed evenly, and then vacuum-baked at 600° C. for 2 h. After grinding, the mixture is sieved to obtain particles with a size between 100 and 150 meshes; thus, an ozone catalytic oxidant is obtained.

[0060] Place the prepared catalyst into Figure 1 The reactor shown uses artificial simulated oxalic acid wastewater as experimental wastewater and operates in the form of continuous flow. The influent oxalic acid is 200 mg / L, the catalyst dosage is 1 g / L, the reaction zone residence time is 60 min, the sedimentation separation zone residence time is 30 min, and the water flow rise rate in the sedimentation separation zone is 12 m / h. The inlet and outlet water of the reaction zone are taken to measure the total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone are taken to measure the SS concentration.

[0061] Comparative Example 3

[0062] This comparative example provides an ozone catalytic oxidant, the raw materials of which are composed of the following components: 9 g of commercially available wine grains and 15 g of cerium nitrate hexahydrate.

[0063] The above raw materials are weighed, ground and mixed evenly, and then vacuum-baked at 600° C. for 2 h. After grinding, the mixture is sieved to obtain particles with a size between 100 and 150 meshes; thus, an ozone catalytic oxidant is obtained.

[0064] Place the prepared catalyst into Figure 1 The reactor shown uses artificial simulated oxalic acid wastewater as experimental wastewater and operates in the form of continuous flow. The influent oxalic acid is 200 mg / L, the catalyst dosage is 1 g / L, the reaction zone residence time is 60 min, the sedimentation separation zone residence time is 30 min, and the water flow rise rate in the sedimentation separation zone is 12 m / h. The inlet and outlet water of the reaction zone are taken to measure the total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone are taken to measure the SS concentration.

[0065] Comparative Example 4

[0066] This comparative example does not add a catalyst, and uses Figure 1 The reactor shown uses artificial simulated oxalic acid wastewater as experimental wastewater and operates in the form of continuous flow. The influent oxalic acid is 200 mg / L, the catalyst dosage is 1 g / L, the reaction zone residence time is 60 min, the sedimentation separation zone residence time is 30 min, and the water flow rise rate in the sedimentation separation zone is 12 m / h. The inlet and outlet water of the reaction zone are taken to measure the total organic carbon concentration, and the inlet and outlet water of the sedimentation separation zone are taken to measure the SS concentration.

[0067] Table 1 Comparison of SS effects of precipitated water

[0068]

[0069] from Figure 2 It can be seen that the particle size of the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst of Example 1 did not change significantly after 30 days of operation, proving its stability during use and not generating a large amount of tiny powders and causing secondary pollution. It can be seen from Table 2 that the catalyst containing the iron tourmaline component will not be lost with the effluent after simple sedimentation, and the effluent SS meets the 10 mg / L standard of the first level a. Figure 3 It can be seen that the average total organic carbon removal rates of Example 1, Example 2 and Example 3 are 92.9%, 89.1% and 84.8%, while those of Comparative Examples 1, 2, 3 and 4 are 44.6%, 59.4%, 58.9% and 21.6%, respectively. The examples are significantly improved over the comparative examples. It can be seen that the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst of the embodiment of the present invention has good catalytic activity, stability and recovery performance through carbon-nitrogen doping and the interaction of cerium dioxide / tourmaline.

[0070] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A carbon-nitrogen doped ceria / tourmaline ozone oxidation catalyst, characterized in that: The raw materials include: tourmaline powder, distiller's grains and cerium nitrate, wherein the mass percentage of tourmaline powder is 50% to 80%; The preparation method of the catalyst comprises the following steps: fully grinding and mixing cerium nitrate, vinasse and tourmaline powder, roasting, grinding and screening to obtain a final product; the mass ratio of cerium nitrate, vinasse and tourmaline powder is 10-50:15-50:100; the roasting temperature is 500-700°C, and the roasting time is 2h.

2. The ozone oxidation catalyst according to claim 1, characterized in that The particle size of the catalyst is 100-150 mesh.

3. The ozone oxidation catalyst according to claim 1, characterized in that The particle size of the ferro-tourmaline powder is in the range of 75 to 150 μm.

4. Use of the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst as claimed in claim 1 in treating oxalic acid in sewage.

5. The use according to claim 4, characterized in that: The following steps are involved: S1. putting the obtained catalyst into the bottom of the reaction zone of the reactor, wherein the reactor further comprises a precipitation separation zone connected to the reaction zone, water first enters the reaction zone from the outside, then overflows from the top of the reaction zone to the bottom of the precipitation separation zone, and then rises and flows out of the reactor; S2. The ozone is passed through a titanium microporous aeration disk from the bottom into the reaction zone; S3. Water is continuously introduced into and discharged from the reactor, and the catalyst precipitated at the bottom of the precipitation separation zone is recovered and returned to the reaction zone.

6. The use according to claim 5, characterized in that: The concentration of oxalic acid in the influent water is 100-300 mg / L; the concentration of the carbon-nitrogen doped cerium dioxide / tourmaline ozone oxidation catalyst in the reaction zone is 0.5-1.5 g / L.

7. The use according to claim 6, characterized in that: The residence time of the influent in the reaction zone is 60-90 min, the residence time in the sedimentation and separation zone is 30-60 min, and the water flow rising velocity in the sedimentation and separation zone is 6-12 m / h.

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