A micro-electrolysis synergistic ozone bifunctional catalyst and its preparation method and use

Abstract

The present invention belongs to the field of water treatment technology, and specifically relates to a preparation method of a micro-electrolysis synergistic ozone bifunctional catalyst and its application in treating organic amine wastewater. The present invention firstly modifies activated carbon by ultrasonic and cobalt loading to obtain modified activated carbon, mixes the modified activated carbon with an appropriate proportion of iron powder, pore-forming agent, etc. in water in a certain proportion, compacts and forms in a tablet pressing mold, sinters at high temperature under oxygen-isolated conditions after drying, and the cobalt ions are reduced to generate elemental cobalt or combined with iron to generate iron-cobalt oxide, which is quenched to form a high-strength micro-electrolysis ozone bifunctional catalyst. The role of the iron-cobalt metal bond improves the structural stability and strength of the material, and a ternary micro-electrolysis system is constructed with cobalt and activated carbon as dual cathodes to synergistically catalyze ozone oxidation to efficiently remove organic amines in wastewater. The micro-electrolysis synergistic ozone oxidation bifunctional catalyst is suitable for the enhanced treatment of a variety of wastewaters containing organic amines, such as printing and dyeing, chemical, textile, pharmaceutical and other wastewaters.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of micro-electrolysis and ozone oxidation bifunctional catalysts in the field of wastewater treatment, and specifically relates to a micro-electrolysis and ozone oxidation bifunctional catalyst for removing organic amines in wastewater, and a preparation method and use thereof. Background Art

[0002] Organic amines are highly toxic, difficult to degrade compounds with poor biodegradability. Substandard discharge of organic amine wastewater will seriously threaten the ecological environment and human health. There are two difficulties in removing organic amines from wastewater: one is the removal of nitrogen, and the other is the removal of toxic organic matter (COD). Most organic amines are difficult to be directly degraded by microorganisms. For example, N,N-dimethylformamide (DMF) is difficult to be biochemically treated because it contains hydrophobic methyl groups at both ends and is highly toxic.

[0003] Micro-electrolysis technology is widely used in sewage treatment due to its low cost and high efficiency. Micro-electrolysis reaction relies on the galvanic cell effect and is accompanied by the combined effects of adsorption, redox, flocculation, precipitation and other effects. It can effectively degrade the toxicity of pollutants and improve the biodegradability of wastewater. Introducing transition metals into the micro-electrolysis reaction to construct a ternary micro-electrolysis system can effectively improve the performance of micro-electrolysis in removing pollutants. Ozone is widely used in wastewater treatment due to its strong oxidizing properties and no secondary pollution. However, ozone oxidation has problems such as low utilization rate and inability to mineralize organic pollutants. Heterogeneous catalytic ozone oxidation not only significantly improves the removal and mineralization of pollutants by ozone, but also has the advantages of being cleaner, more environmentally friendly and more economical.

[0004] Patents have been introduced for treating organic amine wastewater using micro-electrolysis technology and ozone oxidation. For example, the Chinese patent document "A method for treating DMF wastewater using a composite advanced oxidation technology" with publication number CN113754156 A discloses a composite process of iron-carbon micro-electrolysis + flocculation precipitation + ultraviolet-activated persulfate oxidation treatment to treat DMF wastewater, which improves the biodegradability of wastewater and reduces the concentration of DMF. However, the process is complex, has high requirements for pH, requires constant pH adjustment, and requires a large amount of polyaluminum chloride, polyacrylamide, persulfate agent, and requires ultraviolet light activation, which undoubtedly increases costs and limits its industrial application. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing a micro-electrolysis-synergistic ozone bifunctional catalyst. The micro-electrolysis-synergistic ozone bifunctional catalyst prepared by the method can promote the combination of transition metal valence state transformation, electron transfer, and redox in the micro-electrolysis and catalytic ozone oxidation system to synergistically produce active oxygen such as hydroxyl free radicals, and efficiently remove organic amines in wastewater.

[0006] To achieve the above object, the present invention adopts the following technical solution: a method for preparing a micro-electrolysis synergistic ozone bifunctional catalyst, comprising the following steps:

[0007] (1) ultrasonically mixing activated carbon with a cobalt nitrate solution, wherein the mass ratio of the activated carbon to the cobalt nitrate in the cobalt nitrate solution is (40-50):(50-60), and then drying and grinding into powder under oxygen-free conditions to obtain modified activated carbon;

[0008] (2) The modified activated carbon obtained in step (1) is mixed with iron powder and a pore-forming agent in a mass ratio of (20-30):(70-80):(0.5-1), and then ball-milled in a nitrogen atmosphere. After adding water to the ball-milled mixture and stirring, the mixture is pressed into tablets, dried, and then calcined at high temperature in an oxygen-free environment. After quenching, a high-strength iron-cobalt-carbon material, i.e., a micro-electrolysis synergistic ozone bifunctional catalyst, is obtained.

[0009] Further improvement of the preparation method of micro-electrolysis synergistic ozone bifunctional catalyst:

[0010] Preferably, in step (1), the ultrasonic mixing time of the activated carbon and the cobalt nitrate solution is 1-2 h, the stirring time is 8-12 h, the ultrasonic mixing temperature is 20-40° C., the drying temperature is 100-110° C., and the drying time is 24-36 h.

[0011] Preferably, the ball milling time in step (2) is 1-3 h.

[0012] Preferably, the tableting pressure in step (2) is 2-6 MPa.

[0013] Preferably, the temperature of high-temperature calcination in step (2) is 1000-1200° C., the calcination time is 60-180 min, and the negative pressure in the furnace during the calcination process is -0.1 to -0.3 MPa.

[0014] Preferably, in step (2), 1-3 wt % sodium hydroxide solution is used as the quenching medium.

[0015] Preferably, the pore-forming agent in step (2) is sodium carbonate or calcium carbonate, or a mixture of both.

[0016] Preferably, in step (2), the mixture after ball milling is added with water, stirred and then tableted, and the amount of water added is 50-200 mL / Kg.

[0017] The second object of the present invention is to provide a micro-electrolysis synergistic ozone bifunctional catalyst prepared by any of the above preparation methods.

[0018] The second object of the present invention is to provide the use of the above-mentioned micro-electrolysis synergistic ozone bifunctional catalyst in degrading organic amine pollutants in wastewater, wherein the organic amine pollutants are one or a combination of two or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and aniline, and the micro-electrolysis synergistic ozone bifunctional catalyst can improve the biodegradability of the wastewater.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The present invention provides a preparation method of a micro-electrolysis synergistic ozone bifunctional catalyst, firstly, the activated carbon is ultrasonically modified and loaded with cobalt to obtain modified activated carbon, the modified activated carbon is mixed with water in a certain proportion with an appropriate proportion of iron powder and a pore-forming agent, compacted and formed in a tableting mold, dried and sintered at high temperature under oxygen-isolated conditions, and quenched to form a high-strength iron-cobalt-carbon material, i.e., a micro-electrolysis ozone bifunctional catalyst. During the high-temperature calcination process, iron and cobalt are combined by the action of metal bonds. Due to the existence of iron-cobalt bonds, the structure is stable and the material is hard, which improves the hardness and stability of the material. At the same time, part of the cobalt ions are reduced to form elemental cobalt, and part of the cobalt ions are combined with iron to form iron-cobalt oxide. The micro-electrolysis dual cathode composed of zero-valent cobalt and activated carbon improves the wastewater treatment performance of micro-electrolysis. In the step (1), activated carbon loaded with cobalt ions is obtained, and in the step (2), part of the cobalt ions are reduced by iron powder to form elemental cobalt. The activated carbon serves as a carrier of elemental cobalt and forms a dual cathode of micro-electrolysis material with elemental cobalt to enhance the micro-electrolysis effect and accelerate electron transfer. Part of the cobalt ions is combined with iron to form iron-cobalt oxide, which is beneficial to catalytic ozone oxidation. The doping of cobalt and the synergistic effect of micro-electrolysis and catalytic ozone oxidation enable the bifunctional catalyst to efficiently treat organic amines in wastewater.

[0021] 2) The iron-cobalt-carbon micro-electrolysis material prepared by the present invention is placed in an ozone reaction system, and the micro-electrolysis effect and catalytic ozone oxidation work synergistically, which can efficiently treat organic amines in wastewater and improve the biodegradability of wastewater. The present invention does not require the regulation of reaction conditions such as pH, is simple to operate, and saves costs. When used for catalytic degradation of organic amine pollutants with a concentration of 10-50 mg / L in wastewater, the removal rate of organic amines in wastewater is 75-100%, the removal rate of COD is 40-65%, and the chromaticity is reduced. This is because the doping of cobalt accelerates the electron transfer between the anode and the cathode and enhances the catalytic ozone oxidation in the reaction, and the micro-electrolysis and catalytic ozone oxidation produce more ·OH due to the six reaction mechanisms of heterogeneous catalytic ozone oxidation, perozonation reaction, ozone electroreduction, electrochemical oxidation, ozone and OH-reaction, and Fenton-like reaction, which reflects a significant synergistic effect, thereby accelerating the degradation of organic amine wastewater and improving the biodegradability of organic amine wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1This is a SEM spectrum of the iron-cobalt-carbon material prepared in Example 1, i.e., a micro-electrolysis-coordinated ozone oxidation bifunctional catalyst;

[0023] Figure 2 The XRD pattern of the iron-cobalt-carbon micro-electrolysis-ozone bifunctional catalyst prepared in Example 1;

[0024] Figure 3 This is a graph of five repeated experiments of degrading DMF using the iron-cobalt-carbon micro-electrolysis-ozone bifunctional catalyst prepared in Example 1;

[0025] Figure 4 This is a graph of the concentration of ozone dissolved in the solution during the ozone and micro-electrolysis synergistic ozone (ME-O3) process in Example 2;

[0026] Figure 5 This is a graph showing the production of hydroxyl radicals during the ozone and micro-electrolysis synergistic ozone (ME-O3) process in Example 3. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific examples, but the essence of the present invention is not limited to the following examples. The methods are conventional methods unless otherwise specified, and the materials can be obtained from public commercial channels unless otherwise specified. Those skilled in the art should know that any simple transformation or substitution based on the essence of the present invention belongs to the protection scope claimed by the present invention.

[0028] Example 1

[0029] This embodiment provides a method for preparing a micro-electrolysis synergistic ozone bifunctional catalyst, which specifically includes the following steps:

[0030] (1) Preparation of modified activated carbon. Weigh 145 g of cobalt nitrate to prepare 1000 mL of cobalt nitrate solution. Take 145 g of activated carbon and immerse it in the cobalt nitrate solution, mix it by ultrasonic for 1 h, stir it at 25 °C for 8 h, and dry it under anaerobic conditions at 110 °C for 30 h.

[0031] (2) Preparation of iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst. Take 790g of iron powder, 200g of modified activated carbon, and 10g of calcium carbonate, mix them and ball-mill them under nitrogen atmosphere for 1h, add 80ml of water and mix them homogenously, and then press them into shape with a tablet press at a pressure of 3Mpa. After drying, isolate them from oxygen and sinter them at high temperature at 1000℃. During the sintering process, the negative pressure in the furnace is 0.3Mpa. The sintering time is 2h. Take them out and quench them in 1wt% sodium hydroxide solution for 1min to form an iron-cobalt-carbon material, i.e., a micro-electrolysis synergistic ozone oxidation bifunctional catalyst.

[0032] Figure 1The SEM spectrum of the iron-cobalt-carbon material prepared above, i.e., the micro-electrolysis synergistic ozone oxidation bifunctional catalyst, was scanned using a FEI-Quanta 200 scanning electron microscope. Figure 1 The left picture shows that the Fe and Co nanoparticles are wrapped by activated carbon and evenly dispersed, with a particle size of 30-250nm. This indicates that activated carbon provides attachment sites for Fe and Co nanoparticles, which is conducive to the formation of dispersed Fe and Co nanoparticles. The right picture shows the surface morphology of the iron-cobalt-carbon bulk material. It can be seen that the surface of the iron-cobalt-carbon bulk material is rough, and there are nanosheets of about 200nm in size, which may be Fe or Co metal oxide nanosheets. From the appearance of the catalyst, it can be seen that the material has a regular appearance and a hard texture.

[0033] Figure 2 The XRD pattern of the iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst prepared above; Material composition (X'Pert, PANalytical, Cu-Ka, 10°-80°, 10° / min (XRD)), from Figure 2 It can be seen that the main components of the material are Fe, CoFe2O4 and Fe2O3.

[0034] The prepared iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst was tested, and the crushing strength was measured to be 1500N. 200g of the prepared catalyst was put into a 15L / d small test device, and ozone was introduced at a flow rate of 1L / min to treat the wastewater of a pharmaceutical production line with N,N-dimethylformamide (DMF) as the solvent. The inlet DMF concentration was 200mg / L, the outlet DMF concentration was 45mg / L, the inlet COD was reduced from 6300mg / L, and the outlet COD was reduced to 3500mg / L, and the B / C was increased from 0.06 to 0.35. The DMF removal effect was obvious, and the biodegradability was significantly improved. COD can be fully degraded by microorganisms in the later stage.

[0035] Figure 3 This is a graph showing five repeated experiments of DMF degradation using the iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst prepared above. The results show that after five repeated experiments, the DMF degradation rate decreased from 77.5% to 73.3%, with a decrease rate of 5.42%, indicating that the material has good reusability. ICP tests were performed on water samples after five repeated experiments of DMF degradation using the iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst prepared above. The results showed that the solubility of Fe ions and Co ions in the solution were 0.298 mg / L and 0.272 mg / L, respectively, which shows that the material still has good chemical stability after repeated use, and there is no obvious hardening on the surface.

[0036] Example 2

[0037] This embodiment provides a method for preparing a micro-electrolysis synergistic ozone bifunctional catalyst, which specifically includes the following steps:

[0038] (1) Preparation of modified activated carbon. Weigh 210 g of cobalt nitrate to prepare 1000 mL of cobalt nitrate solution. Take 160 g of activated carbon and immerse it in the cobalt nitrate solution, ultrasonicate for 1.5 h, stir for 12 h at 25 °C, and dry for 36 h under anaerobic conditions at 110 °C.

[0039] (2) Preparation of iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst. Take 700g of iron powder, 293g of modified activated carbon, and 7g of calcium carbonate, ball mill for 1.5h, add 90mL of water and mix homogenously, and then press into shape with a tablet press at a pressure of 4Mpa. After drying, sinter at a high temperature of 1100℃. The negative pressure in the furnace during the sintering process is 0.2Mpa. The sintering time is 1.5h. Take it out and quench it in 1% sodium hydroxide solution for 30s to form an iron-cobalt-carbon material, i.e., a micro-electrolysis synergistic ozone oxidation bifunctional catalyst.

[0040] The iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst prepared under this condition was measured to have a crushing strength of 1700N. 200g of the prepared catalyst was placed in a 15L / d pilot device, and ozone was introduced at a flow rate of 0.5L / min to treat the wastewater of a pesticide production line with N,N-dimethylacetamide (DMAC) as a solvent. The inlet DMAC concentration was 280mg / L, the outlet DMAC concentration was 54mg / L, the inlet COD decreased from 5800mg / L to 3200mg / L, and the B / C increased from 0.05 to 0.30. The DMAC removal effect was obvious, and the biodegradability of the wastewater was significantly improved.

[0041] Figure 4 This is a graph of the concentration of ozone dissolved in the solution during the ozone and micro-electrolysis synergistic ozone (ME-O3) process. 5 minutes after the reaction started, the concentration of ozone dissolved in the solution during the ME-O3 process was greater than that in the ozone process, indicating that the presence of the catalyst is conducive to the dissolution of ozone in the solution and improves the mass transfer efficiency of ozone. Subsequently, the presence of the micro-electrolysis material made the concentration of ozone in the solution significantly lower than that in the ozone oxidation process, indicating that the catalyst promotes the decomposition of ozone into active oxygen.

[0042] Example 3

[0043] This embodiment provides a method for preparing a micro-electrolysis synergistic ozone bifunctional catalyst, which specifically includes the following steps:

[0044] (1) Preparation of modified activated carbon. Weigh 79 g of cobalt nitrate to prepare 500 mL of cobalt nitrate solution. Take 70 g of activated carbon and immerse it in the cobalt nitrate solution, ultrasonicate it for 1 h, stir it at 25 °C for 8 h, and dry it under anaerobic conditions at 100 °C for 24 h.

[0045] (2) Preparation of iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst. Take 360g of iron powder, 88g of modified activated carbon, and 2g of calcium carbonate, ball mill for 1h, add 40ml of water and mix homogeneously, and then press into shape with a tablet press at a pressure of 3Mpa. After drying, sinter at a high temperature of 1100℃. The negative pressure in the furnace during the sintering process is 0.2Mpa. The sintering time is 1.5h. Take it out and quench it in 1% sodium hydroxide solution for 30s to form an iron-cobalt-carbon material, i.e., a micro-electrolysis synergistic ozone oxidation bifunctional catalyst.

[0046] The iron-cobalt-carbon micro-electrolysis synergistic ozone oxidation bifunctional catalyst prepared under this condition was measured to have a crushing strength of 1600N. 150g of the prepared catalyst was placed in a 15L / d small test device, and ozone was introduced at a flow rate of 0.5L / min to treat a chemical wastewater containing aniline. The inlet aniline concentration was 480mg / L, the effluent aniline concentration was 110mg / L, the inlet COD decreased from 7000mg / L to 3400mg / L, the aniline removal effect was obvious, the biodegradability was significantly improved, the B / C increased from 0.05 to 0.25, and the chromaticity decreased.

[0047] Figure 5 This is the hydroxyl radical production diagram in the process of ozone and micro-electrolysis synergistic ozone (ME-O3), which shows that there is a synergistic effect of micro-electrolysis and ozone in the generation of hydroxyl radicals. The presence of the catalyst significantly increases the production of hydroxyl radicals and improves the oxidation capacity.

[0048] Those skilled in the art should understand that the above are only some specific embodiments of the present invention, rather than all embodiments. It should be noted that for those of ordinary skill in the art, many modifications and improvements can be made, and all modifications or improvements that do not exceed the scope of protection of the present invention should be regarded as the scope of protection of the present invention.

Claims

1. A use of a micro-electrolysis synergistic ozone bifunctional catalyst for degrading organic amine pollutants in wastewater, characterized in that: The organic amine pollutant is one or a combination of two or more of N,N-dimethylformamide, N,N-dimethylacetamide, and aniline, and the amount of the micro-electrolysis synergistic ozone bifunctional catalyst added to the wastewater is 5-15 g / L, and ozone is introduced into the wastewater at the same time; The preparation method of the micro-electrolysis synergistic ozone bifunctional catalyst comprises the following steps: (1) ultrasonically mixing activated carbon with a cobalt nitrate solution, wherein the mass ratio of the activated carbon to the cobalt nitrate in the cobalt nitrate solution is (40-50):(50-60), and then drying and grinding into powder under oxygen-free conditions to obtain modified activated carbon; (2) The modified activated carbon obtained in step (1) is mixed with iron powder and a pore-forming agent in a mass ratio of (20-30):(70-80):(0.5-1), and then ball-milled in a nitrogen atmosphere. After adding water to the ball-milled mixture and stirring, the mixture is pressed into tablets, dried, and then calcined at high temperature in an oxygen-free environment. After quenching, a high-strength iron-cobalt-carbon material, i.e., a micro-electrolysis synergistic ozone bifunctional catalyst, is obtained.

2. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: In step (1), the activated carbon and the cobalt nitrate solution are ultrasonically mixed for 1-2 hours, the ultrasonic mixing temperature is 20-40° C., the drying temperature is 100-110° C., and the drying time is 24-36 hours.

3. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: The ball milling time in step (2) is 1-3h.

4. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: The tableting pressure in step (2) is 2-6 MPa.

5. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: The temperature of high-temperature calcination in step (2) is 1000-1200° C., the calcination time is 60-180 min, and the negative pressure in the furnace during the calcination process is -0.1 to -0.3 Mpa.

6. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: In step (2), 1-3 wt % sodium hydroxide solution is used as the quenching medium.

7. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: The pore-forming agent in step (2) is sodium carbonate or calcium carbonate, or a mixture of the two.

8. The use of the micro-electrolysis synergistic ozone bifunctional catalyst according to claim 1 for degrading organic amine pollutants in wastewater, characterized in that: In step (2), water is added to the mixture after ball milling, and then the mixture is stirred and pressed into tablets, and the amount of water added is 50-200 mL / Kg.

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