A method for preparing a cordierite honeycomb ceramic catalyst and applications thereof

Abstract

The application discloses a preparation method of a cordierite honeycomb ceramic-based catalyst and application thereof. The method takes a cordierite honeycomb ceramic-based carrier, alumina as a coating, and a transition metal oxide as an active component, and adopts a coating impregnation precipitation method to prepare a monolithic catalyst which is used for catalytic wet oxidation degradation of azo dye wastewater under the condition of normal temperature, normal pressure and oxygen input. The monolithic catalyst obtained by the method can effectively prevent the problems of agglomeration and difficult recycling of powder catalyst, and has good catalytic activity and reusability for catalytic wet oxidation degradation of azo dye.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater treatment, and particularly relates to application of cordierite honeycomb ceramic-based monolithic catalyst in catalytic wet oxidation treatment of azo dye wastewater. BACKGROUND

[0002] At present, the dye output of China accounts for more than 70% of the total global output, and at the same time, about 160 million cubic meters of dye wastewater is discharged into the water environment every year, which is one of the main sources of water pollutants in China. Azo dyes become the largest production and the most widely used type of dyes due to the advantages of bright color, strong coloring power and easy production, and account for about 50% of the total amount of dye wastewater discharge. Dye wastewater is usually highly toxic and difficult to biodegrade, which causes significant damage to the ecological system and also endangers human health. The continuous decrease of environmental carrying capacity requires the continuous improvement of the discharge standard of printing and dyeing wastewater, and it is currently an urgent problem to find an economic and efficient dye wastewater treatment technology.

[0003] The treatment technologies of azo dye wastewater mainly include biological method, physical method and chemical method. Due to the characteristics of high toxicity and poor biodegradability of dye wastewater, the wastewater needs to be pretreated before being treated by biological method, so the biological method is difficult to be applied to the treatment of azo dye wastewater on a large scale. The physical treatment of azo dye wastewater can only transfer pollutants without destroying the structure of dye molecules, so the dye is not fundamentally removed. The application method of acid modified cordierite honeycomb ceramic adsorbent in dye wastewater treatment (publication number CN116282329A) can effectively adsorb organic cationic dyes in wastewater after the cordierite honeycomb ceramic adsorbent is modified by acid and is easy to recover. However, the adsorbent only adsorbs and transfers dye pollutants by physical method without destroying the structure of dye molecules, so the dye is not fundamentally degraded and secondary pollution to the environment may be caused. In the chemical method, catalytic wet oxidation method has good treatment effect on high-toxicity and difficult-to-degrade organic wastewater and will not cause secondary pollution to the environment. Catalytic wet oxidation technology is developed from wet oxidation technology. The method uses air or pure oxygen as oxidant to oxidize and degrade high-concentration organic pollutants under high temperature (398K-593K) and high pressure (0.5MPa-20MPa) conditions into small-molecule organic matter and inorganic matter such as CO2 and H2O, so as to achieve the purpose of treating dye wastewater. By adding catalyst, the required temperature and pressure of the reaction can be appropriately reduced, the reaction can be carried out under relatively mild reaction conditions, the reaction rate can be improved, and the operation cost can be reduced. So far, the catalyst used for treating dye wastewater by catalytic wet oxidation method is mostly in powder form, which has problems of large bed pressure drop and difficult recycling and reuse in the use process. At the same time, due to the difficulty of reaction under normal temperature and pressure, the reaction temperature and pressure need to be increased to improve the catalytic activity of the catalyst in the reaction process. Therefore, it is necessary to develop a kind of monolithic catalyst with high catalytic activity and easy separation and recovery. SUMMARY

[0004] The application provides an application method of cordierite honeycomb ceramic-based monolithic catalyst in azo dye wastewater treatment. The method uses cordierite honeycomb ceramic as carrier, alumina as coating and transition metal oxide as active component to prepare a monolithic catalyst for catalytic wet oxidation degradation of azo dye wastewater under the conditions of normal temperature and pressure and oxygen inlet. The monolithic catalyst obtained by the application can effectively prevent the agglomeration and difficult recycling of powder catalyst, and has good catalytic activity and reusability for catalytic wet oxidation degradation of azo dye.

[0005] The application is implemented by adopting the following technical scheme:

[0006] A preparation method of a cordierite honeycomb ceramic-based monolithic catalyst, comprising the following steps:

[0007] (1) cutting the cordierite honeycomb ceramic into particles, immersing in an acid solution at 303K-373K for 0.5h-2h, then washing with deionized water until the washing liquid is neutral, drying and calcining to complete the cordierite pretreatment;

[0008] The acid is hydrochloric acid, acetic acid, oxalic acid or nitric acid; the concentration is 5%-40%;

[0009] The volume of the acid solution is 1.8-4 times the volume of the cordierite honeycomb ceramic;

[0010] The particle size of the particles is 1-15cm;

[0011] (2) immersing the cordierite honeycomb ceramic particles after acid treatment into a coating solution for 0.1h-4h for coating, drying and calcining after coating, repeating the coating, drying and calcining process 1-5 times to coat the carrier multiple times to achieve the required loading amount;

[0012] The coating solution is an aluminum sol; the content of alumina is 10%-40%; the loading amount is 4%-38%;

[0013] (3) immersing the cordierite honeycomb ceramic after coating into a salt solution for 2h-6h, blowing off the excess immersion liquid in the cordierite pores with a hair dryer after immersion, then immersing it in an alkali solution for 2h-6h for precipitation, and then washing, drying and calcining the catalyst with deionized water after immersion and precipitation.

[0014] The catalyst is prepared by a coating, immersion and precipitation method;

[0015] The salt is Cu(NO3)2, Fe(NO3)3, Co(NO3)2, NiCl2 or Zn(NO3)2; the concentration of the salt solution is 0.1mol / L-10mol / L;

[0016] The alkali is NaOH, NH4OH or NH4HCO3; the concentration of the alkali solution is 0.1mol / L-10mol / L;

[0017] The drying temperature in steps (1)-(3) is 348K-373K; the drying time is 2h-6h;

[0018] The calcining temperature in steps (1)-(3) is 573K-873K; the calcining time is 1h-4h.

[0019] The application of the cordierite honeycomb ceramic catalyst prepared by the method is used for treating azo dye wastewater by a catalytic wet oxidation method.

[0020] Specifically, the method comprises the following steps:

[0021] First, oxygen is introduced into the dye wastewater for 5-10 minutes, then the cordierite honeycomb ceramic catalyst is added and oxygen is continuously introduced, and the reaction is carried out at normal temperature and pressure for 10-150 minutes to complete the treatment of the dye;

[0022] Among them, the normal temperature and pressure condition refers to a reaction pressure of 1 atm and a reaction temperature of room temperature (283-303 K);

[0023] The azo dye is basic red 46, methyl orange, reactive black 5, acid orange 7 or acid red 73;

[0024] The concentration of the azo dye in the wastewater is 5-500 mg / L;

[0025] The catalyst dosage is 5-100 g / L; and the oxygen aeration amount of each liter of solution is 10-400 L / h;

[0026] The degradation rate of the cordierite-based honeycomb ceramic catalyst on the azo dye is 10%-90%.

[0027] The substantial features of the present application are:

[0028] (1) The present application first applies a cordierite honeycomb ceramic-based monolithic catalyst for the degradation of azo dyes. The cordierite honeycomb ceramic has regular and parallel pores, which can be well tailored and cut into the required shape. The modified catalyst has a large specific surface area and excellent pore structure, which is beneficial to the generation of more free radicals by the catalytic oxidant;

[0029] (2) Compared with the traditional powder catalyst, the monolithic catalyst prepared by using cordierite honeycomb ceramic as the carrier in the present application has the advantages of small bed pressure drop, easy assembly, disassembly and recovery, and also avoids secondary pollution to the environment, so it is more suitable for the treatment of dye wastewater in industry;

[0030] (3) The cordierite honeycomb ceramic-based monolithic catalyst used in the present application is used for the degradation of azo dyes by catalytic wet oxidation technology, and the reaction conditions are mild. Under the condition of normal temperature and pressure and oxygen introduction, the degradation rate of azo dyes can reach 90.0% at most.

[0031] (4) The cordierite honeycomb ceramic-based monolithic catalyst of the present application has good reusability, after reaction, the catalyst is simply cleaned with water, dried, and calcined, and then the catalyst can be reused with good catalytic activity, and the decolorization rate of the catalyst on the azo dye wastewater is maintained at 50% or more after 5 times of reaction. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 XRD patterns of the cordierite honeycomb ceramic carrier, the cordierite after acid treatment, the cordierite coated with an aluminum sol coating, and the cordierite honeycomb ceramic-based monolithic catalyst.

[0033] Figure 2 UV-vis absorption spectrum of the cordierite honeycomb ceramic-based catalyst prepared in Example 9 for degrading dye wastewater. DETAILED DESCRIPTION

[0034] The loading rate of the cordierite honeycomb ceramic-based catalyst coating is calculated by weighing the mass of the carrier before and after coating. The loss rate of the cordierite honeycomb ceramic-based catalyst coating is calculated by placing the coated cordierite honeycomb ceramic into a beaker and treating it in an ultrasonic cleaner for 10 minutes, and then weighing the monolithic catalyst after treatment.

[0035] The calculation formula of the loading rate ω% and the loss rate η% of the cordierite honeycomb ceramic-based catalyst coating is as follows:

[0036]

[0037] Wherein m0, m1, m2 are the masses of the cordierite before coating, after coating, and after ultrasonic treatment, respectively.

[0038] The activity of the catalyst is indicated by the decolorization rate of the simulated dye wastewater before and after reaction, and the specific steps are as follows:

[0039] Prepare a standard simulated dye wastewater with a certain concentration, and determine the standard curve. Add a certain amount of cordierite-based, stir at normal temperature and pressure, and after a certain time of degradation, use deionized water as a reference solution to measure the absorbance of the dye solution at each time, and calculate the concentration at this time through the standard curve to obtain the decolorization rate R%.

[0040] The calculation formula of the dye decolorization rate R% is as follows:

[0041]

[0042] Wherein C0, C t are the initial concentration of the dye solution and the concentration of the dye solution at time t, respectively.

[0043] The following are specific embodiments of the present application. The following examples are only used to illustrate the present application, but not to limit the scope of the present application.

[0044] Example 1

[0045] The preparation method of the cordierite honeycomb ceramic-based monolithic catalyst is as follows: the cordierite honeycomb ceramic is cut into particles with a particle size of 1.5 cm, immersed in 20 mL of an oxalic acid solution with a mass concentration of 20% (the volume ratio of the solution to the cube is 2:1), heated at 358 K for 2 h, washed with deionized water until the washing solution is neutral after acid treatment, placed in a blast drying oven, dried at 353 K for 2 h, and then transferred to a muffle furnace for calcination at 673 K for 2 h, and the cordierite pretreatment is completed.

[0046] The pretreated cordierite honeycomb ceramic is immersed in 20 mL of an alumina sol solution with a mass content of 21% alumina, ultrasonically immersed at room temperature for 0.2 h, dried at 353 K for 4 h, and then calcined at 773 K for 4 h in a muffle furnace. The single coating of the carrier coating can reach a coating rate of 4.5%, and the coating loss rate is 2.7%.

[0047] The cordierite honeycomb ceramic after coating is immersed in 20 mL of a 0.5 mol / L copper nitrate solution for 4 h, then immersed in 20 mL of a 0.5 mol / L sodium hydroxide solution for 4 h for precipitation, washed with deionized water after the immersion and precipitation are completed, dried at 353 K for 6 h, and then calcined at 623 K for 3 h to obtain the cordierite honeycomb ceramic-based monolithic catalyst.

[0048] Example 2

[0049] The degradation experiment of simulated alkaline red 46 dye wastewater is as follows: 200 mL of simulated azo dye wastewater with a concentration of 50 mg / L of alkaline red 46 is taken in a beaker, air in the container is exhausted by blowing in oxygen for 10 min before reaction, 2 g of catalyst is added, the oxygen aeration amount is controlled at 16 L / h, and the reaction is carried out at normal temperature and pressure for 90 min. The highest dye decolorization rate can reach 53%.

[0050] Example 3

[0051] The other steps of the preparation of the cordierite honeycomb ceramic-based monolithic catalyst are the same as in Example 1, except that the immersion time for coating is 1 h, the coating rate of the carrier reaches 18.2%, the coating loss rate is 1.8%, and the degradation experiment of simulated dye wastewater is the same as in Example 2. The highest dye decolorization rate can reach 58%.

[0052] Example 4

[0053] The other steps of the preparation of the cordierite honeycomb ceramic-based monolithic catalyst are the same as those of Example 3, except that the number of times of repeating the "coating, drying, and calcining" process is 2, the coating rate of the coating of the carrier is 36%, the carrier loss rate is 2.1%, the degradation experiment of the simulated dye wastewater is the same as that of Example 2, and the highest dye decolorization rate is 65%.

[0054] Example 5

[0055] The other steps of the preparation of the cordierite honeycomb ceramic-based monolithic catalyst are the same as those of Example 4, except that the concentration of oxalic acid is 5%, the coating rate of the coating of the carrier is 5.7%, the carrier loss rate is 8.3%, the degradation experiment of the simulated dye wastewater is the same as that of Example 2, and the highest dye decolorization rate is 13%.

[0056] Example 6

[0057] The other steps of the preparation of the cordierite honeycomb ceramic-based monolithic catalyst are the same as those of Example 5, except that the concentrations of the copper nitrate impregnation solution and the sodium hydroxide precipitator are 0.4 mol / L, the degradation experiment of the simulated dye wastewater is the same as that of Example 2, and the highest dye decolorization rate is 73%.

[0058] Example 7

[0059] The preparation of the cordierite honeycomb ceramic-based monolithic catalyst is the same as that of Example 6, and the other steps of the degradation experiment of the simulated dye wastewater are the same as those of Example 2, except that the target pollutant is methyl orange, and the highest dye decolorization rate is 38.4%.

[0060] Example 8

[0061] The preparation of the cordierite honeycomb ceramic-based monolithic catalyst and the other steps of the degradation experiment of the simulated dye wastewater are the same as those of Example 7, except that the amount of the catalyst is 6 g, and the highest dye decolorization rate is 76%.

[0062] Example 9

[0063] The preparation of the cordierite honeycomb ceramic-based monolithic catalyst and the other steps of the degradation experiment of the simulated dye wastewater are the same as those of Example 8, except that the aeration amount of the oxidant is 24 L / h. As shown in the figure, the absorption peak of the conjugated system formed by the azo double bond in the basic red 46 dye is located in the visible light region at 530 nm, which is the maximum absorption wavelength of the dye. According to the standard curve and the measured absorbance before and after the degradation of the dye, the concentration of the dye is converted, and the highest dye decolorization rate after 90 min of the degradation reaction is 90%. Figure 2 Example 10

[0064]

[0065] ​The preparation of the cordierite honeycomb ceramic monolithic catalyst and other steps of the degradation experiment of the simulated dye wastewater were the same as those of Example 9, except that the initial concentration of the dye was 150 mg / L, and the highest dye decolorization rate was up to 59.1%.

[0066] As can be seen from the above examples, the cordierite honeycomb ceramic monolithic catalyst prepared by the present application can be effectively used for the catalytic wet oxidation technology to degrade azo dye wastewater at normal temperature and pressure. The process has the advantages of simple preparation method of the catalyst, easy separation and recycling, and can be used for catalytic degradation of azo dyes at normal temperature and pressure.

[0067] The above only describes several preferred embodiments of the present application, but the present application is not limited to the above several specific embodiments. The above specific embodiments are illustrative rather than restrictive, and researchers in the field can make improvements and refinements under the inspiration of the present application, while following the spirit and principles of the present application, which are all within the protection scope of the present application.

[0068] The details of the present application are well known.

Claims

1. Use of a cordierite honeycomb ceramic monolith catalyst, characterized in that The preparation method of the catalyst comprises the following steps: (1) cut the cordierite honeycomb ceramics into particles, immerse them in an acid solution at 303 K-373 K for 0.5 h-2 h, then wash them with deionized water until the washing liquid is neutral, dry and calcine to complete the cordierite pretreatment; the acid is acetic acid or oxalic acid; the mass concentration is 5%-40%; (2) immerse the cordierite honeycomb ceramic particles treated by the acid into a coating solution for 0.1 h-4 h for coating, dry and calcine after coating, repeat the coating, drying and calcining process 1-5 times, and coat the carrier multiple times to achieve the required loading amount; the coating solution is an aluminum sol; the mass content of alumina is 10%-40%; and the loading amount is 4%-38%; (3) immerse the coated cordierite honeycomb ceramics in a salt solution for 2 h-6 h, blow off the excess immersion liquid in the cordierite pores with a hair dryer, immerse them in an alkali solution for 2 h-6 h for precipitation, and then wash, dry and calcine the catalyst with deionized water; the salt is Cu(NO3)2; the concentration of the salt solution is 0.1 mol / L-10 mol / L; the alkali is NaOH or NH4OH; the concentration of the alkali solution is 0.1 mol / L-10 mol / L; the volume of the acid solution is 1.8-4 times the volume of the cordierite honeycomb ceramics; the particle size in step (1) is 1-15 cm; the cordierite honeycomb ceramic-based catalyst prepared by the method is used for treating azo dye wastewater by the catalytic wet oxidation method.

2. Use of a cordierite honeycomb ceramic monolith catalyst according to claim 1, characterized in that The drying temperature in steps (1)-(3) is 348 K-373 K; and the drying time is 2 h-6 h; The calcining temperature in steps (1)-(3) is 573 K-873 K; and the calcining time is 1 h-4 h.

3. Use of a cordierite honeycomb ceramic monolith catalyst according to claim 1, characterized in that The application comprises the following steps: first, pass oxygen into the dye wastewater for 5-10 minutes, then add the cordierite honeycomb ceramic-based catalyst and continuously pass oxygen, and react at normal temperature and pressure for 10 min-150 min to complete the treatment of the dye; the azo dye is basic red 46, methyl orange, reactive black 5, acid orange 7 or acid red 73; the concentration of the azo dye in the wastewater is 5 mg / L-500 mg / L.

4. Use of a cordierite honeycomb ceramic monolith catalyst according to claim 3, characterized in that The catalyst dosage is 5 g / L-100 g / L; and the oxygen aeration amount per liter of reaction solution is 10 L / h-400 L / h; the degradation rate of the cordierite-based honeycomb ceramic catalyst on azo dyes is 10%-90%.

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