Preparation method and application of catalyst for high-salt phenolic wastewater treatment

Abstract

The present application relates to the technical field of catalyst, and discloses a preparation method and application of a catalyst for treating high-salt phenolic wastewater.The porous carrier is impregnated in an impregnation solution containing glucose, starch and active metal salt, and then calcined in an inert atmosphere according to the following steps: heating at 2-5 DEG C / min to 400-500 DEG C and keeping for 1-2 h, heating at 5-10 DEG C / min to 600-700 DEG C and keeping for 2-4 h, and heating at 10-15 DEG C / min to 750-850 DEG C and keeping for 1-2 h.The catalyst prepared by the method has high catalytic activity and stability, can efficiently activate persulfate to generate singlet oxygen free radicals, and has high degradation capacity for phenolic substances in wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a preparation method and application of a catalyst for treating high-salt phenolic wastewater. BACKGROUND

[0002] Industrial wastewater, especially the wastewater containing salt and phenol generated in the fields of coking, petrochemical, pharmaceutical, etc., has complex components and contains a large amount of organic matter difficult to be biodegraded and high-concentration salt (such as sodium sulfate and sodium chloride), and it is extremely difficult to be directly treated by biochemical treatment. At present, the advanced oxidation technology is an effective method for treating such wastewater, which utilizes strong oxidizing free radicals (such as ·OH, SO4· 2- 、 1 O2, etc.) to degrade pollutants, and the core difficulty lies in developing a high-stability and high-activity catalyst which can adapt to a high-salt environment and efficiently degrade high-boiling-point organic matter such as phenol. The existing advanced oxidation catalysts have the following disadvantages: a single active component catalyst is easy to be deactivated in a complex wastewater system and metal ions are easy to be lost; a conventional carrier has insufficient stability in a high-salt environment and weak anchoring capacity for active components. Therefore, it is of great significance to develop a catalyst for treating high-salt phenolic wastewater, which has high catalytic activity, high stability and high salt passivation resistance.

[0003] Carbon-doped metal salt catalysts have been proven to be useful in the catalytic advanced oxidation of organic pollutants in wastewater. Such catalysts are composed of a porous carbon matrix and active metal components, wherein the carbon material has good electrical conductivity, chemical stability and controllable pore structure, and the metal salt provides specific catalytic or adsorption active sites. At present, the methods for preparing carbon-doped metal salt catalysts mainly include impregnation method, coprecipitation method and high-temperature pyrolysis method, etc. Among them, the impregnation method is simple to operate, but the metal particles are easy to agglomerate, the dispersion is uneven, and the interaction between the carrier and the metal is weak, resulting in low utilization rate of active sites; the coprecipitation method can improve the dispersion, but the process is complex, impurity ions are easy to be left, and the pore structure of the carbon matrix is difficult to be accurately controlled. The high-temperature pyrolysis method (for example, patent CN109999753A) can solve the above-mentioned defects in the impregnation method and the coprecipitation method, but the graphitization degree of the carbon skeleton is negatively correlated with the exposure amount of the metal active sites, and it is difficult to simultaneously realize the high graphitization of the carbon skeleton and the high exposure of the metal active sites, resulting in low catalytic activity of the catalyst. SUMMARY

[0004] In order to solve the technical problem of low catalytic activity of the carbon-doped metal salt catalyst prepared by the existing method, the present application provides a preparation method and application of a catalyst for treating high-salt phenolic wastewater. The catalyst obtained by the preparation method of the present application has high catalytic activity and stability, can efficiently activate peroxymonosulfate to generate singlet oxygen free radicals (· 1 O2), and has high degradation capacity for phenolic substances in wastewater.

[0005] The specific technical scheme of the present application is:

[0006] In a first aspect, the present application provides a preparation method of a catalyst for high-salt phenolic wastewater treatment, comprising:

[0007] After impregnating the porous carrier in an impregnation solution containing glucose, starch and active metal salt, the following steps are carried out in an inert atmosphere: heating at 2-5℃ / min to 400-500℃ for 1-2h, heating at 5-10℃ / min to 600-700℃ for 2-4h, and heating at a rate of 10-15℃ / min to 750-850℃ for 1-2h.

[0008] The present application uses glucose and starch as carbon sources, and cooperates with a specific three-step calcination method, which can make the prepared catalyst have high catalytic activity, can efficiently activate persulfate, and can make it preferentially generate 1 O2, has high degradation efficiency for phenolic substances in wastewater, and at the same time, the prepared catalyst also has good stability and can maintain high catalytic activity after long-term use. The specific mechanism includes:

[0009] (1) The carbon layer formed by glucose after carbonization has high electronic conductivity, which is beneficial to electron transfer; starch slowly decomposes during carbonization, and its long-chain structure acts as a soft template to form a carbon layer rich in defect sites. These defect sites interact with metal active sites to form a "metal-carbon defect" interface. The "metal-carbon defect" interface can efficiently activate persulfate, and the high-electronic-conductivity carbon layer formed by glucose can promote the transfer of electrons from the metal active site to the carbon layer, optimize the decomposition path of persulfate, and preferentially generate 1 O2 rather than other free radicals. Since 1 O2 is a highly selective oxidant that preferentially oxidizes groups with high electron density (such as phenolic hydroxyl groups) through electrophilic attack on electron-rich regions, therefore, by the above method, persulfate preferentially generates 1 O2, which is beneficial to improve the degradation efficiency of phenolic substances.

[0010] (2) In the first step of calcination (ramp up to 400-500℃ at 2-5℃ / min and keep for 1-2h), glucose is carbonized to form a carbon layer with microporous basic structure and high electronic conductivity, and small molecule volatile substances are removed to avoid pore collapse at high temperature in the subsequent step; in the second step of calcination (ramp up to 600-700℃ at 5-10℃ / min and keep for 2-4h), starch is fully carbonized to form a carbon layer rich in defect sites and a mesoporous structure, and the active metal salt is converted into a catalytically active site anchored on the defect sites of the carbon layer to prevent agglomeration; due to the effect of the active metal, the temperature required for graphitization of the carbon layer can be reduced, so in the third step of calcination (ramp up to 750-850℃ at a rate of 10-15℃ / min and keep for 1-2h), the carbon layer is graphitized to improve the electronic conductivity of the carbon layer. The graphitization process of the carbon skeleton is prone to clumping, covering the metal active sites, so the degree of graphitization of the carbon skeleton is often negatively correlated with the exposure amount of the metal active sites. The three-step calcination process designed in the present application can balance the high degree of graphitization of the carbon skeleton and the high exposure amount of the metal active sites, thereby improving the activation efficiency of persulfate and promoting 1 O2 generation. At the same time, through the design of temperature, holding time and heating rate in the three-step calcination process, the catalyst formed can have high specific surface area and multi-level pore distribution, and the metal active sites can be uniformly dispersed and stably supported, thereby improving the catalytic activity of the catalyst and facilitating higher phenolic substance degradation efficiency.

[0011] As an optional implementation, the active metal salt includes manganese salt and iron salt, and the molar ratio of manganese element to iron element is 1:0.3-0.8.

[0012] The manganese species and iron species form a heterogeneous bimetallic site in the carbon matrix, wherein the manganese species has high affinity for persulfate and can activate persulfate to generate 1 O2 through electron transfer; the iron species not only stabilizes the manganese species, but also adjusts the electron density of the carbon layer, making the manganese species more likely to attack the O-O bond of persulfate, thereby selectively generating 1 O2. In addition, the present application adopts the method of loading manganese salt, iron salt, glucose and starch on a porous carrier and then calcining, which can form a "Mn-Fe-C" ternary composite structure on the porous carrier, and the charge redistribution in the structure can further enhance the 1 O2 generation path. Through the above method, the use of manganese salt and iron salt as active metal salt can improve the selectivity and yield of 1 O2, thereby improving the phenolic substance degradation efficiency, and also enhancing the stability of the catalyst in a high-salt environment.

[0013] As an optional implementation, the mass ratio of glucose to starch is 1:1-3.

[0014] When the mass ratio of glucose to starch is 1:1~3, combined with the specific three-step roasting process in the present application, the formed catalyst has a more ideal pore structure, and the carbon layer in the catalyst has more "metal-carbon defects" and higher electronic conductivity, which is conducive to the preferential generation of 1 O2, thereby improving the degradation efficiency of phenolic substances in wastewater to a greater extent.

[0015] As an optional embodiment, the mass ratio of the porous carrier to the impregnation solution is 1:0.5~3; the total content of glucose and starch in the impregnation solution is 5~40wt%, and the content of active metal salt is 1~20wt%; the impregnation time is 6~48h; and the porous carrier comprises one or more of activated carbon, activated carbon fiber, carbon nanotube, graphene, porous ceramic, molecular sieve and metal organic framework.

[0016] As an optional embodiment, the porous carrier is pretreated at 100~300℃ for 1~5h before the impregnation process.

[0017] Through the above pretreatment operation, impurities on the surface of the porous carrier can be removed, and the pore structure thereof can be enhanced.

[0018] As an optional embodiment, after the roasting process is completed, the roasting product is loaded onto the ceramic membrane by using gas pressure, and then calcined at 400~600℃ for 2~6h.

[0019] As an optional embodiment, after the roasting process is completed, the roasting product is subjected to pickling and then loaded onto the ceramic membrane; the pickling process comprises: soaking the roasting product in a dilute acid solution for 1~3h, washing with water, and drying; the dilute acid solution is a solution of HCl and / or H2SO4, and the concentration is 0.1~1mol / L.

[0020] Through the above pickling operation, unstable metal species on the surface of the catalyst can be removed.

[0021] In the second aspect, the present application provides an application of a catalyst in the treatment of high-salt phenolic wastewater, wherein the catalyst is prepared by the above preparation method.

[0022] The catalyst of the present application has good amorphism in high-salt wastewater and can effectively degrade the classified substances therein, thereby improving the biodegradability of such wastewater.

[0023] As an optional embodiment, the application comprises the following steps: contacting the wastewater to be treated after the addition of persulfate with the catalyst to perform a advanced oxidation reaction.

[0024] As an optional implementation, the amount of persulfate added to the wastewater to be treated is 3~5 g / L; the content of phenolic substances in the wastewater to be treated is 50~150 mg / L, and the conductivity is 4000~25000 μS / cm.

[0025] Thirdly, this invention provides a method to improve the catalytic formation of persulfate by a catalyst. 1 The method for improving O2 efficiency, wherein the catalyst is prepared using the above-described preparation method.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) This invention uses glucose and starch as carbon sources, and with a specific three-step calcination method, the catalyst can have high catalytic activity and stability, and can efficiently activate the preferential formation of persulfate. 1 O2 has a high efficiency in degrading phenolic substances in wastewater and can maintain high catalytic activity even after long-term use.

[0028] (2) This invention uses manganese salt and iron salt as active metal salts, combined with the specific catalyst preparation method of this invention (using manganese salt, iron salt, glucose and starch loaded together on a porous support and then calcined), which can improve... 1 The selectivity and yield of O2 can improve the degradation efficiency of phenolic substances, while also enhancing the stability of the catalyst in high-salt environments. Attached Figure Description

[0029] Figure 1 In the process of treating wastewater with catalyst in Example 1 1 Electron paramagnetic resonance spectrum of O2 generation.

[0030] Figure 2 The results are the catalyst specific surface area test results for Example 1. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] First, the present invention relates to a method for preparing a catalyst for treating high-salt phenolic wastewater, comprising:

[0033] After impregnating the porous carrier in an impregnation solution containing glucose, starch and active metal salts, it is calcined in an inert atmosphere according to the following steps: heating at 2~5℃ / min to 400~500℃ and holding for 1~2h, heating at 5~10℃ / min to 600~700℃ and holding for 2~4h, and heating at 10~15℃ / min to 750~850℃ and holding for 1~2h.

[0034] In some embodiments, the porous carrier is pretreated at 100-300℃ for 1-5h before the impregnation process.

[0035] In some embodiments, the active metal salt comprises manganese salt and iron salt, wherein the molar ratio of manganese element to iron element is 1:0.3-0.8.

[0036] In some embodiments, the mass ratio of glucose to starch is 1:1-3.

[0037] In some embodiments, the mass ratio of the porous carrier to the impregnation solution is 1:0.5-3; the total content of glucose and starch in the impregnation solution is 5-40wt%, and the content of the active metal salt is 1-20wt%; and the impregnation time is 6-48h.

[0038] In some embodiments, the porous carrier comprises one or more of activated carbon, activated carbon fiber, carbon nanotube, graphene, porous ceramic, molecular sieve and metal organic framework.

[0039] In some embodiments, after the calcination process, the calcination product is soaked in a dilute acid solution for 1-3h, washed with water, dried, loaded onto a ceramic membrane by using air pressure, and then calcined at 400-600℃ for 2-6h; the dilute acid solution is a solution of HCl and / or H2SO4 with a concentration of 0.1-1mol / L.

[0040] Secondly, the application relates to application of a catalyst in high-salt phenolic wastewater treatment, wherein the catalyst is prepared by the above method.

[0041] In some embodiments, the application comprises the following steps: contacting the wastewater to be treated after adding persulfate with the catalyst to perform a high-level oxidation reaction; the addition amount of the persulfate in the wastewater to be treated is 3-5g / L; the content of phenolic substances in the wastewater to be treated is 50-150mg / L, and the conductivity is 4000-25000μS / cm.

[0042] Thirdly, the application relates to a method for improving the efficiency of a catalyst in generating 1 O2 by catalyzing persulfate, wherein the catalyst is prepared by the above method.

[0043] The application is described below by means of specific examples and comparative examples. It should be understood that the examples are only used for describing the application and are not used for limiting the scope of the application.

[0044] Example 1

[0045] A catalyst for high-salt phenolic wastewater treatment is prepared according to the following steps:

[0046] S1. Pretreatment: The molecular sieve is pretreated at 200℃ for 3 hours to obtain pretreated molecular sieve.

[0047] S2. Impregnation Treatment: Starch, glucose, manganese acetate, and ferric nitrate are dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate, and ferric nitrate are 10 wt%, 10 wt%, 6.7 wt%, and 3.3 wt%, respectively. Pretreated molecular sieves are added to the impregnation solution, and the solid-liquid ratio is controlled at 1:1 (i.e., the mass ratio between the pretreated molecular sieves and the impregnation solution is 1:1). After impregnation for 24 hours, the catalyst precursor is obtained by filtration.

[0048] S3. Drying and Calcination: The catalyst precursor was air-dried at room temperature for 12 hours, and then dried at 80℃ for 8 hours. After drying, it was placed in a tube furnace and calcined in the following three steps under a N2 atmosphere: First, the temperature was increased to 400℃ at a heating rate of 2℃ / min and held for 2 hours; second, the temperature was increased to 700℃ at a heating rate of 5℃ / min and held for 2 hours; third, the temperature was increased to 850℃ at a heating rate of 15℃ / min and held for 1 hour. After calcination, it was naturally cooled to room temperature to obtain the carbon-doped composite catalyst.

[0049] S4. Post-treatment: The carbon-doped composite catalyst was soaked in 0.5 mol / L HCl solution for 2 hours, washed with deionized water until neutral, and dried at 80℃ for 4 hours to obtain catalyst powder.

[0050] S5. Membrane Loading: Using an ultrafiltration cup, 2g of catalyst powder was loaded onto a ceramic membrane under pressure at 0.5MPa. After loading, the membrane was dried at 90°C and then calcined at 600°C for 4 hours to obtain the catalyst of this embodiment. The specific surface area of ​​the catalyst prepared in this embodiment was tested using the BET method, and the results are as follows: Figure 2 As shown ( Figure 2 In the graph, the horizontal axis represents the calculation result obtained based on P / P0, and the vertical axis represents the calculation term after linearization of the BET equation, i.e., the calculation result obtained based on (P / P0) / (V×(1-P / P0)), where: P is the gas pressure at equilibrium during adsorption; P0 is the saturated vapor pressure of the gas at the test temperature; and V is the actual adsorption amount at the corresponding P / P0, in mL / g. Figure 2 The slope and intercept of the sample can be used to calculate its specific surface area, which was measured to be 175.55 m². 2 / g.

[0051] Example 2

[0052] A catalyst for treating high-salt phenolic wastewater was prepared by following these steps:

[0053] S1, pretreatment: the activated carbon was pretreated at 150℃ for 4 hours to obtain pretreated activated carbon.

[0054] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate were 7.5wt%, 7.5wt%, 5.3wt% and 2.7wt% respectively. The pretreated activated carbon was added into the impregnation solution, and the solid-liquid ratio was controlled to be 1.5:1 (i.e. the mass ratio between the pretreated activated carbon and the impregnation solution was 1.5:1). After impregnation for 18 hours, the catalyst precursor was separated by filtration.

[0055] S3, drying and calcination: the catalyst precursor was air-dried at room temperature for 10 hours, and then dried at 90℃ for 6 hours. After drying, the catalyst precursor was placed in a tube furnace and subjected to the following three-step calcination under N2 atmosphere: first step, heating to 500℃ at a heating rate of 5℃ / min and maintaining for 1 hour; second step, heating to 600℃ at a heating rate of 10℃ / min and maintaining for 3 hours; third step, heating to 750℃ at a heating rate of 10℃ / min and maintaining for 2 hours. After calcination, the catalyst was naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0056] S4, post-treatment: the carbon-doped composite catalyst was soaked in a 0.5mol / L H2SO4 solution for 1.5 hours, then washed with deionized water until neutral, and dried at 80℃ for 4 hours to obtain a catalyst powder.

[0057] S5, membrane loading: 2g of the catalyst powder was loaded onto a ceramic membrane using an ultrafiltration cup under the condition of 0.8MPa, and then dried at 75℃. Subsequently, the catalyst was calcined at 450℃ for 6 hours to obtain the catalyst of the present example.

[0058] Example 3

[0059] A catalyst for treating high-salt phenolic wastewater was prepared according to the following steps:

[0060] S1, pretreatment: the porous ceramic was pretreated at 250℃ for 2 hours to obtain pretreated porous ceramic.

[0061] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate were 18.75wt%, 6.25wt%, 6wt% and 6wt% respectively. The pretreated porous ceramic was added into the impregnation solution, and the solid-liquid ratio was controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution was 2:1). After impregnation for 30 hours, the catalyst precursor was separated by filtration.

[0062] S3, drying and calcination: the catalyst precursor was dried at room temperature for 15 hours, and then dried at 100°C for 5 hours. After drying, it was placed in a tube furnace and subjected to the following three-step calcination under N2 atmosphere: first step, heating to 450°C at a heating rate of 5°C / min, and maintaining for 1 hour; second step, heating to 600°C at a heating rate of 10°C / min, and maintaining for 4 hours; third step, heating to 850°C at a heating rate of 10°C / min, and maintaining for 2 hours. After calcination, it was naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0063] S4, post-treatment: the carbon-doped composite catalyst was soaked in a 0.5 mol / L HCl solution for 2 hours, washed with deionized water until neutral, and dried at 80°C for 4 hours to obtain a catalyst powder.

[0064] S5, membrane loading: 2 g of the catalyst powder was loaded onto a ceramic membrane using an ultrafiltration cup under a pressure of 0.3 MPa, and then dried at 65°C. After that, it was calcined at 500°C for 5 hours to obtain the catalyst of the present example.

[0065] Example 4

[0066] A catalyst for treating high-salt phenolic wastewater was prepared according to the following steps:

[0067] S1, pretreatment: carbon nanotubes were pretreated at 180°C for 3 hours to obtain a pretreated porous ceramic.

[0068] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate were 5wt%, 5wt%, 10wt% and 5wt%, respectively. The pretreated carbon nanotubes were added to the impregnation solution, and the solid-liquid ratio was controlled to be 1:1 (i.e. the mass ratio between the pretreated carbon nanotubes and the impregnation solution was 1:1). After impregnation for 30 hours, the catalyst precursor was separated by filtration.

[0069] S3, drying and calcination: the catalyst precursor was dried at room temperature for 15 hours, and then dried at 100°C for 5 hours. After drying, it was placed in a tube furnace and subjected to the following three-step calcination under N2 atmosphere: first step, heating to 450°C at a heating rate of 5°C / min, and maintaining for 1 hour; second step, heating to 600°C at a heating rate of 10°C / min, and maintaining for 4 hours; third step, heating to 850°C at a heating rate of 10°C / min, and maintaining for 2 hours. After calcination, it was naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0070] S4, post-treatment: the carbon-doped composite catalyst was soaked in 0.5 mol / L H2SO4 solution for 1 hour, then washed with deionized water until neutral, and dried at 80°C for 4 hours to obtain catalyst powder.

[0071] S5, membrane loading: 2 g of catalyst powder was loaded onto the ceramic membrane using an ultrafiltration cup under the condition of 0.5 MPa by means of air pressure, and then dried at 90°C after loading was completed, followed by calcination at 400°C for 4 hours to obtain the catalyst of the present example.

[0072] Example 5

[0073] The difference between the present example and Example 3 is only that in step S2, the mass ratio of starch to glucose is changed from 3:1 to 1:1.5; the rest of the raw materials and preparation steps are the same as those of Example 3. Specifically, a catalyst for treating high-salinity phenolic wastewater is prepared according to the following steps:

[0074] S1, pretreatment: the porous ceramic was pretreated at 250°C for 2 hours to obtain pretreated porous ceramic.

[0075] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate were 10wt%, 15wt%, 6wt% and 6wt%, respectively. The pretreated porous ceramic was added to the impregnation solution, and the solid-liquid ratio was controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution was 2:1). After impregnation for 30 hours, the catalyst precursor was separated by filtration.

[0076] S3, drying and calcination: the catalyst precursor was air-dried at room temperature for 15 hours, and then dried at 100°C for 5 hours. After drying, it was placed in a tube furnace and subjected to the following three-step calcination under N2 atmosphere: first step, heating to 450°C at a heating rate of 5°C / min, and keeping for 1 hour; second step, heating to 600°C at a heating rate of 10°C / min, and keeping for 4 hours; third step, heating to 850°C at a heating rate of 10°C / min, and keeping for 2 hours. After calcination, it was naturally cooled to room temperature to obtain the carbon-doped composite catalyst.

[0077] S4, post-treatment: the carbon-doped composite catalyst was soaked in 0.5 mol / L H2SO4 solution for 1 hour, then washed with deionized water until neutral, and dried at 80°C for 4 hours to obtain catalyst powder.

[0078] S5, membrane loading: 2 g of catalyst powder was loaded onto the ceramic membrane using an ultrafiltration cup under the condition of 0.5 MPa by means of air pressure, and then dried at 90°C after loading was completed, followed by calcination at 400°C for 4 hours to obtain the catalyst of the present example.

[0079] Example 6

[0080] The difference between this example and Example 3 is that in step S2, the mass ratio of starch and glucose is changed from 3:1 to 4:1; the rest of the raw materials and preparation steps are the same as those of Example 3. Specifically, a catalyst for treating high-salt phenolic wastewater is prepared according to the following steps:

[0081] S1, pretreatment: the porous ceramic is pretreated at 250°C for 2 hours to obtain pretreated porous ceramic.

[0082] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate are dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate are 20wt%, 5wt%, 6wt% and 6wt% respectively. The pretreated porous ceramic is added to the impregnation solution, and the solid-liquid ratio is controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution is 2:1). After 30 hours of impregnation, the catalyst precursor is separated by filtration.

[0083] S3, drying and calcination: the catalyst precursor is dried at room temperature for 15 hours, and then dried at 100°C for 5 hours. After drying, it is placed in a tube furnace and calcined in N2 atmosphere in the following three steps: first step, heating to 450°C at a rate of 5°C / min and keeping for 1 hour; second step, heating to 600°C at a rate of 10°C / min and keeping for 4 hours; third step, heating to 850°C at a rate of 10°C / min and keeping for 2 hours. After calcination, it is naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0084] S4, post-treatment: the carbon-doped composite catalyst is soaked in 0.5mol / L HCl solution for 2 hours, then washed with deionized water until neutral, and dried at 80°C for 4 hours to obtain catalyst powder.

[0085] S5, membrane loading: 2g of catalyst powder is loaded onto the ceramic membrane using an ultrafiltration cup under the condition of 0.3MPa by means of air pressure, and then dried at 65°C after loading is completed. After that, it is calcined at 500°C for 5 hours to obtain the catalyst of this example.

[0086] Example 7

[0087] The difference between this example and Example 3 is that in step S2, manganese acetate is replaced by an equal amount of copper acetate; the rest of the raw materials and preparation steps are the same as those of Example 3. Specifically, a catalyst for treating high-salt phenolic wastewater is prepared according to the following steps:

[0088] S1, pretreatment: the porous ceramic was pretreated at 250℃ for 2 hours to obtain a pretreated porous ceramic.

[0089] S2, impregnation treatment: starch, glucose, copper acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, copper acetate and ferric nitrate were 18.75wt%, 6.25wt%, 6wt% and 6wt% respectively. The pretreated porous ceramic was added into the impregnation solution, and the solid-liquid ratio was controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution was 2:1). After impregnation for 30 hours, the catalyst precursor was separated by filtration.

[0090] S3, drying and calcination: the catalyst precursor was air-dried at room temperature for 15 hours, and then dried at 100℃ for 5 hours. After drying, the catalyst precursor was placed in a tube furnace and calcined in N2 atmosphere in the following three steps: first step, the temperature was raised to 450℃ at a rate of 5℃ / min and maintained for 1 hour; second step, the temperature was raised to 600℃ at a rate of 10℃ / min and maintained for 4 hours; third step, the temperature was raised to 850℃ at a rate of 10℃ / min and maintained for 2 hours. After calcination, the catalyst was naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0091] S4, post-treatment: the carbon-doped composite catalyst was soaked in 0.5mol / L HCl solution for 2 hours, then washed with deionized water until neutral, and dried at 80℃ for 4 hours to obtain a catalyst powder.

[0092] S5, membrane loading: 2g of catalyst powder was loaded onto a ceramic membrane using an ultrafiltration cup under the condition of 0.3MPa, and then dried at 65℃. After that, the catalyst was calcined at 500℃ for 5 hours to obtain the catalyst of the present embodiment.

[0093] Comparative Example 1

[0094] A catalyst for treating high-salt phenolic wastewater was prepared according to the following steps:

[0095] S1, impregnation treatment: manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of manganese acetate and ferric nitrate were 6.7wt% and 3.3wt% respectively. The molecular sieve was added into the impregnation solution, and the solid-liquid ratio was controlled to be 1:1 (i.e. the mass ratio between the molecular sieve and the impregnation solution was 1:1). After impregnation for 24 hours, the catalyst precursor was separated by filtration.

[0096] S2, drying and calcination: the catalyst precursor was air-dried at room temperature for 12 hours, and then dried at 80℃ for 8 hours. Then, the catalyst precursor was calcined in N2 atmosphere at a rate of 10℃ / min to 750℃ and maintained for 6 hours. After that, the catalyst was naturally cooled to room temperature to obtain a catalyst powder.

[0097] S3: Membrane loading: 2 g of the catalyst powder was loaded onto the ceramic membrane by using an ultrafiltration cup under the condition of 0.5 MPa, and then dried at 90 °C. After that, the catalyst was calcined at 600 °C for 4 hours to obtain the catalyst of the present comparative example. It was detected that the specific surface area of the catalyst prepared in the present comparative example was 137.53 m2 / g. 2

[0098] Comparative Example 2

[0099] The present comparative example was different from Example 3 only in that starch was replaced by glucose with the same mass in step S2, and the other raw materials and preparation steps were the same as those of Example 3. Specifically, a catalyst for treating high-salinity phenolic wastewater was prepared according to the following steps:

[0100] S1, Pretreatment: The porous ceramic was pretreated at 250 °C for 2 hours to obtain the pretreated porous ceramic.

[0101] S2, Impregnation treatment: Glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of glucose, manganese acetate and ferric nitrate were 25 wt%, 6 wt% and 6 wt% respectively. The pretreated porous ceramic was added into the impregnation solution, and the solid-liquid ratio was controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution was 2:1). After impregnation for 30 hours, the catalyst precursor was separated by filtration.

[0102] S3, Drying and calcination: The catalyst precursor was dried at room temperature for 15 hours, and then dried at 100 °C for 5 hours. After drying, the catalyst precursor was placed in a tube furnace and calcined in N2 atmosphere in the following three steps: first step, the temperature was increased to 450 °C at a rate of 5 °C / min and maintained for 1 hour; second step, the temperature was increased to 600 °C at a rate of 10 °C / min and maintained for 4 hours; third step, the temperature was increased to 850 °C at a rate of 10 °C / min and maintained for 2 hours. After calcination, the carbon-doped composite catalyst was naturally cooled to room temperature.

[0103] S4, Post-treatment: The carbon-doped composite catalyst was soaked in 0.5 mol / L HCl solution for 2 hours, washed with deionized water until neutral, and dried at 80 °C for 4 hours to obtain the catalyst powder.

[0104] S5, Membrane loading: 2 g of the catalyst powder was loaded onto the ceramic membrane by using an ultrafiltration cup under the condition of 0.3 MPa, and then dried at 65 °C. After that, the catalyst was calcined at 500 °C for 5 hours to obtain the catalyst of the present comparative example.

[0105] Comparative Example 3

[0106] ​The only difference between the present comparative example and Example 3 is that in step S2, glucose is replaced by starch with the same mass; the rest of the raw materials and preparation steps are the same as those of Example 3. Specifically, the present comparative example prepares a catalyst for treating high-salinity phenolic wastewater according to the following steps:

[0107] S1, pretreatment: the porous ceramic is pretreated at 250°C for 2 hours to obtain pretreated porous ceramic.

[0108] S2, impregnation treatment: starch, manganese acetate and ferric nitrate are dissolved in water to obtain an impregnation solution, wherein the contents of starch, manganese acetate and ferric nitrate are 25wt%, 6wt% and 6wt% respectively. The pretreated porous ceramic is added to the impregnation solution, and the solid-liquid ratio is controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution is 2:1). After 30 hours of impregnation, the catalyst precursor is separated by filtration.

[0109] S3, drying and calcination: the catalyst precursor is air-dried at room temperature for 15 hours, and then dried at 100°C for 5 hours. After drying, it is placed in a tube furnace and subjected to the following three-step calcination under N2 atmosphere: first step, heating to 450°C at a heating rate of 5°C / min, holding for 1 hour; second step, heating to 600°C at a heating rate of 10°C / min, holding for 4 hours; third step, heating to 850°C at a heating rate of 10°C / min, holding for 2 hours. After calcination, it is naturally cooled to room temperature to obtain a carbon-doped composite catalyst.

[0110] S4, post-treatment: the carbon-doped composite catalyst is soaked in 0.5mol / L HCl solution for 2 hours, then washed with deionized water until neutral, and dried at 80°C for 4 hours to obtain a catalyst powder.

[0111] S5, membrane loading: 2g of catalyst powder is loaded onto a ceramic membrane using an ultrafiltration cup under the condition of 0.3MPa by means of air pressure, and then dried at 65°C after loading is completed. Subsequently, it is calcined at 500°C for 5 hours to obtain the catalyst of the present comparative example.

[0112] Comparative Example 4

[0113] The only difference between the present comparative example and Example 3 is that in step S3, the three-step calcination method is replaced by a one-step calcination method; the rest of the raw materials and preparation steps are the same as those of Example 3. Specifically, the present comparative example prepares a catalyst for treating high-salinity phenolic wastewater according to the following steps:

[0114] S1, pretreatment: the porous ceramic is pretreated at 250°C for 2 hours to obtain pretreated porous ceramic.

[0115] S2, impregnation treatment: starch, glucose, manganese acetate and ferric nitrate were dissolved in water to obtain an impregnation solution, wherein the contents of starch, glucose, manganese acetate and ferric nitrate were 18.75wt%, 6.25wt%, 6wt% and 6wt% respectively. The pretreated porous ceramic was added into the impregnation solution, and the solid-liquid ratio was controlled to be 2:1 (i.e. the mass ratio between the pretreated porous ceramic and the impregnation solution was 2:1). After impregnation for 30 hours, the catalyst precursor was obtained by filtration separation.

[0116] S3, drying and calcination: the catalyst precursor was air-dried at room temperature for 15 hours, and then dried at 100℃ for 5 hours. After drying, the catalyst precursor was placed in a tube furnace, and heated to 850℃ at a heating rate of 10℃ / min under N2 atmosphere, and kept for 6 hours. After calcination, the catalyst precursor was naturally cooled to room temperature to obtain the carbon-doped composite catalyst.

[0117] S4, post-treatment: the carbon-doped composite catalyst was soaked in 0.5mol / L HCl solution for 2 hours, and then washed with deionized water until neutral. The catalyst powder was obtained by drying at 80℃ for 4 hours.

[0118] S5, membrane loading: 2g of the catalyst powder was loaded onto the ceramic membrane by using an ultrafiltration cup under the condition of 0.3MPa, and then dried at 65℃. Subsequently, the catalyst was calcined at 500℃ for 5 hours to obtain the catalyst of the present comparative example.

[0119] Application Example

[0120] The catalysts prepared according to the methods of the examples and comparative examples were used to treat simulated high-salinity and low-salinity phenolic wastewater (in the high-salinity phenolic wastewater, the concentration of phenol was 100mg / L, and the conductivity was 25000μS / cm; in the low-salinity phenolic wastewater, the concentration of phenol was 100mg / L, and the conductivity was 4000μS / cm). The method was as follows: first, 4g / L of sodium persulfate was added to the low-salinity phenolic wastewater as an oxidant; then, the wastewater was circulated through the ceramic membrane loaded with 2g of catalyst powder in cross-flow filtration mode by using a centrifugal pump; finally, the reaction was carried out for 30 minutes under the condition of continuous circulation, and the removal rate of total organic carbon (TOC) was determined. The results are shown in Table 1.

[0121] During the treatment of wastewater by the catalyst of Example 1, 2,2,6,6-tetramethylpiperidine was used as an O2 trapping agent for electron paramagnetic resonance (EPR) test, and the obtained spectrum is shown in Figure 1, which shows that O2 was generated in the wastewater. 1 Figure 1 1

[0122] ​​​Following the above method, the catalysts of each embodiment and comparative example were repeatedly used in the treatment of high-salt phenolic wastewater five times, and the TOC removal rate was tested on the fifth use. The results are shown in Table 1.

[0123] Table 1. Results of TOC removal rate test in wastewater

[0124]

[0125] Analysis of test results:

[0126] (1) When using the catalyst of Comparative Example 1, although it can reduce the TOC value of low-salt phenolic wastewater to a certain extent, the treatment effect on high-salt phenolic wastewater is very poor. In comparison, the catalysts of Examples 1-7 significantly improve the TOC removal rate of high-salt phenolic wastewater. The above results show that, compared with the catalysts prepared by the traditional impregnation method, the catalysts prepared by the method of the present invention can effectively improve the degradation efficiency of phenolic substances in high-salt phenolic wastewater.

[0127] (2) Compared with Examples 5, 6, Comparative Examples 2 and 3, the catalyst of Example 3 showed a higher TOC removal rate when treating high-salt phenolic wastewater. The above results indicate that, compared with using glucose or starch alone, combining these two carbon sources can improve the catalytic activity of the catalyst, and the ratio between the two carbon sources affects the catalytic activity. The reason for this is that the carbon layer formed by glucose after carbonization has high electronic conductivity, facilitating electron transfer; starch decomposes slowly during carbonization, and its long-chain structure acts as a soft template, forming a carbon layer rich in defect sites. These defect sites interact with metal active sites, forming a "metal-carbon defect" interface. The "metal-carbon defect" interface can efficiently activate persulfate, and combined with the highly electronically conductive carbon layer formed by glucose, it can promote the transfer of electrons from metal active sites to the carbon layer, optimizing the decomposition path of persulfate and preferentially generating... 1 O2, rather than other free radicals, improves the degradation efficiency of phenolic substances.

[0128] (3) Compared with Comparative Example 4, the catalyst used in Example 3 showed a higher TOC removal rate and stronger stability when treating high-salt phenolic wastewater. These results indicate that, compared with the one-step calcination method, the three-step calcination method of this invention can produce a catalyst with higher catalytic activity and stability. The reason for this is that the three-step calcination process of this invention can balance the high graphitization degree of the carbon skeleton with the high exposure of metal active sites, thereby improving the activation efficiency of persulfate and promoting… 1O2 is generated; meanwhile, through the temperature, holding time and heating rate design in the three-step calcination process, the catalyst formed can have high specific surface area and multi-stage pore distribution, and realize uniform dispersion and stable immobilization of metal active sites, thereby improving the catalytic activity of the catalyst and being beneficial to realize higher degradation efficiency of phenolic substances.

[0129] (4) Compared with Example 7, the TOC removal rate of the catalyst of Example 3 is higher and the stability is stronger when treating high-salt phenolic wastewater. The above results show that the selection of active metal salt in the preparation process of the catalyst will affect the catalytic activity and stability of the obtained catalyst. The reason is that manganese species and iron species form a heterogeneous bimetallic site in the carbon matrix, wherein the manganese species has high affinity for persulfate and can activate persulfate to generate 1 O2 through electron transfer; the iron species not only stabilizes the manganese species, but also makes the manganese species more easily attack the O-O bond of persulfate by adjusting the electron density of the carbon layer, thereby selectively generating 1 O2; in addition, the manganese salt, iron salt, glucose and starch are loaded on the porous carrier and then calcined in the present application, which can form a ternary composite structure of "Mn-Fe-C" on the porous carrier, and the charge redistribution in the structure can further enhance 1 the generation path of O2.

Claims

1. A method for preparing a catalyst for treating high-salt phenolic wastewater, characterized in that, include: The porous carrier is impregnated in an impregnation solution containing glucose, starch, and active metal salts, and then calcined in an inert atmosphere according to the following steps: heating at 2-5℃ / min to 400-500℃ and holding for 1-2 hours, heating at 5-10℃ / min to 600-700℃ and holding for 2-4 hours, and heating at 10-15℃ / min to 750-850℃ and holding for 1-2 hours; the active metal salts include manganese salts and iron salts, wherein the molar ratio of manganese to iron is 1:0.3-0.8; the mass ratio of glucose to starch is 1:1-3; the mass ratio of porous carrier to impregnation solution is 1:0.5-3; in the impregnation solution, the total content of glucose and starch is 5-40 wt%, and the content of active metal salts is 1-20 wt%.

2. The preparation method according to claim 1, characterized in that, The soaking time is 6 to 48 hours.

3. The preparation method according to claim 1, characterized in that, The porous support includes one or more of activated carbon, activated carbon fiber, carbon nanotubes, graphene, porous ceramics, molecular sieves, and metal-organic frameworks.

4. The preparation method according to claim 1, characterized in that, Before the impregnation process, the porous carrier is pretreated at 100~300℃ for 1~5h.

5. The preparation method according to claim 1, characterized in that, After the calcination process is completed, the calcined product is loaded onto a ceramic film using air pressure, and then calcined at 400~600℃ for 2~6 hours.

6. The preparation method according to claim 5, characterized in that, After the calcination process is completed, the calcined product is acid-washed and then loaded onto a ceramic membrane. The acid-washing process includes: soaking the calcined product in a dilute acid solution for 1-3 hours, washing with water, and drying.

7. The preparation method according to claim 6, characterized in that, The dilute acid solution is a solution of HCl and / or H2SO4 with a concentration of 0.1~1 mol / L.

8. The application of a catalyst in the treatment of high-salt phenolic wastewater, characterized in that, The catalyst is prepared by the preparation method described in any one of claims 1 to 7.

9. The application according to claim 8, characterized in that, Includes the following steps: The wastewater to be treated after the addition of persulfate is contacted with the catalyst to carry out an advanced oxidation reaction.

10. A method to improve the catalytic formation of persulfate by catalysts 1 The method for improving O2 efficiency is characterized by... The catalyst is prepared by the preparation method described in any one of claims 1 to 7.

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