Composite catalyst-based ceramic membrane assembly, and preparation method therefor and use thereof

Abstract

Disclosed in the present invention are a composite catalyst-based ceramic membrane assembly, and a preparation method therefor and a use thereof. The ceramic membrane assembly comprises a ceramic membrane, a composite catalyst in a ceramic membrane channel, and a water discharging block and a closed block secured at two ends of the ceramic membrane; and one end of the water discharging block is provided with a water pumping hole communicated with a surface of the ceramic membrane. The composite catalyst in the ceramic membrane channel is formed by injecting a slurry into the ceramic membrane channel and then calcining same. The slurry is obtained by adding attapulgite and activated carbon to a copper nitrate solution and impregnating same. According to the present invention, a catalyst capable of activating persulfate can be packaged into the ceramic membrane channel; the obtained ceramic membrane assembly is combined with persulfate to achieve efficient removal of organic pollutants by catalytic oxidation while filtering. Compared with the ozone-activated carbon technology, the amount of activated carbon used can be reduced, the impact on the turbidity of the effluent is reduced, the removal rates of the odor, the permanganate index, the ammonia nitrogen can be increased, and the indicators such as disinfection by-products are reduced, and therefore advanced treatment of drinking water and sewage is implemented.

Description

A ceramic membrane assembly based on composite catalyst and its preparation method and application Technical Field

[0001] The present invention belongs to the technical field of water treatment, and in particular relates to a ceramic membrane component based on a composite catalyst, and a preparation method and application thereof. Background Art

[0002] With the rapid development of society and the economy, the contradiction between ever-improving living standards and increasingly severe environmental pollution is becoming increasingly prominent, and the water environment faces a serious pollution problem. Currently, organic water pollution is extremely serious and poses a significant threat to the living environment and health of the people. Therefore, the water treatment industry will face severe challenges for a long time to come. Membrane separation technology is an effective treatment technology for removing organic pollutants from water. In the current market, organic membranes still dominate the market. Due to their low preparation cost and high packing density, most water treatment industries use organic membranes as the primary separation unit. However, the physical properties of organic materials mean that organic membranes are prone to aging and cannot be used in strong acid and strong base media, organic solvents, or high temperature and high pressure environments, thus limiting the widespread application of membrane separation technology.

[0003] Advanced oxidation is an effective technology for degrading toxic and difficult-to-degrade organic pollutants. It uses the strong oxidizing free radicals generated by the reaction system to decompose organic pollutants in water into small molecules, and even mineralize them into CO2, H2O and corresponding inorganic ions, thus completely removing pollutants. Traditional advanced oxidation technologies such as Fenton and ozone catalytic oxidation degrade pollutants by producing hydroxyl radicals as the main active species, while persulfate activation technology produces sulfate radicals (SO4 • − , E 0 =2.5-3.1 V) is an advanced oxidation technology. Compared to traditional advanced oxidation technologies, persulfate systems offer advantages such as greater selectivity, a wider pH range, low energy consumption, strong oxidation effects, and reduced incorporation of secondary pollutants. However, existing catalysts for advanced oxidation are mostly amorphous powders, making them difficult to recycle and ensuring that all wastewater comes into contact with the catalyst. Summary of the Invention

[0004] The purpose of the present invention is to provide a ceramic membrane assembly based on a composite catalyst, a preparation method and application thereof, in response to the problem that new pollutants are frequently detected in water and are difficult to be effectively removed by conventional microfiltration and ultrafiltration membranes.

[0005] In its first aspect, the present invention provides a ceramic membrane assembly based on a composite catalyst, comprising a ceramic membrane, a composite catalyst immobilized within the ceramic membrane channels, and a water outlet block and a closure block respectively affixed to each end of the ceramic membrane; the water outlet block is provided with a water inlet connected to the surface of the ceramic membrane. The composite catalyst is generated and immobilized within the ceramic membrane channels by adding a catalyst precursor slurry to the ceramic membrane channels and then calcining the catalyst precursor slurry; the catalyst precursor slurry is prepared by adding attapulgite and activated carbon to a copper nitrate solution and impregnating the solution.

[0006] Preferably, the ceramic membrane is an alumina flat ceramic membrane with a membrane pore size of 300-700 nm and a membrane channel cross-sectional size of 4×4 mm.

[0007] Preferably, the mass ratio of attapulgite to activated carbon is (10-50):1.

[0008] Preferably, the concentration of the copper nitrate solution is 10 g / L to 50 g / L.

[0009] Preferably, the outlet block and the closing block respectively seal the ends of the channels used in the ceramic membrane. Grooves are formed on opposing sides of the outlet block and the closing block. The ends of the ceramic membrane are respectively inserted into the grooves of the outlet block and the closing block.

[0010] In a second aspect, the present invention provides a method for preparing a ceramic membrane assembly based on a composite catalyst, comprising the following steps:

[0011] Step 1: Add attapulgite and activated carbon to a copper nitrate solution for immersion to obtain a catalyst precursor slurry. The mass ratio of attapulgite to activated carbon is (10-50):1. The concentration of the copper nitrate solution is 10g / L to 50g / L.

[0012] Step 2: inject the catalyst precursor slurry obtained in step 1 into the channel of the ceramic membrane and dry it.

[0013] Step 3: calcining the product obtained in step 2 to obtain a ceramic membrane containing catalyst in the channel.

[0014] Step 4: Fix a water outlet block and a sealing block at both ends of the ceramic membrane obtained in step 3; the water outlet block is provided with a water inlet connected to the surface of the ceramic membrane.

[0015] Preferably, the activated carbon is powdered activated carbon.

[0016] Preferably, in step 1, attapulgite and activated carbon are added to the copper nitrate solution and ultrasonically mixed for 2 h to 6 h.

[0017] Preferably, in step 1, the immersion time is greater than or equal to 12 hours.

[0018] Preferably, the specific process of drying in step 2 is to heat-treat the ceramic membrane injected with the catalyst precursor slurry at a temperature of 60° C. to 100° C. for 6 h to 8 h.

[0019] Preferably, the calcination conditions in step three are: heating to 300° C. to 500° C. in an air atmosphere, calcining time is 3 h, and the heating rate is 5° C. / min to 10° C. / min.

[0020] In a second aspect, the present invention provides a method for treating organic wastewater, the process of which is as follows: adding persulfate to the organic wastewater to be treated; connecting the water suction port of the aforementioned ceramic membrane assembly to a negative pressure source through a pipe and immersing the ceramic membrane assembly into the organic wastewater to be treated; starting the negative pressure source to pump out the treated organic wastewater through the ceramic membrane assembly; the treated organic wastewater undergoes a catalytic oxidation reaction in the ceramic membrane assembly, so that organic pollutants are degraded and removed.

[0021] The present invention has the following beneficial effects:

[0022] 1. This invention encapsulates a persulfate-activating catalyst within ceramic membrane channels to create a catalyst-encapsulated ceramic membrane assembly. This ceramic membrane assembly, while simultaneously filtering, works with persulfate to efficiently remove organic pollutants through catalytic oxidation. Compared to ozone-activated carbon technology, this technology reduces the amount of activated carbon used, minimizing the impact on effluent turbidity, improving odor, permanganate index, and ammonia nitrogen removal rates, and reducing disinfection byproducts, thereby achieving advanced drinking water treatment.

[0023] 2. The ceramic membrane assembly provided by the present invention not only achieves a filtering effect but also serves as a flow channel for wastewater, so that all organic wastewater is fully in contact with the composite catalyst in the ceramic membrane assembly, thereby achieving the effect of fully removing soluble organic pollutants.

[0024] 3. The present invention utilizes the advantages of ceramic membranes such as good chemical stability, which can effectively alleviate membrane pollution, increase membrane service life, and achieve deep removal of organic pollutants in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of the preparation process of the ceramic membrane assembly in Example 1 of the present invention;

[0026] FIG2 is a schematic diagram of an effect test performed in Example 1 of the present invention;

[0027] FIG3 is a comparison diagram of the degradation effects of Examples 1-3 of the present invention and Comparative Example 1 on bisphenol A. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the accompanying drawings.

[0029] Example 1

[0030] As shown in Figure 1, a ceramic membrane module based on a composite catalyst is prepared as follows:

[0031] Step 1: Add 50g of attapulgite and 1g of activated carbon to 20mL of a 50g / L copper nitrate solution and ultrasonically mix for 6h. Then, soak for 24h to obtain a viscous catalyst precursor slurry. Powdered activated carbon was used.

[0032] Step 2: Use a syringe to inject the catalyst precursor slurry obtained in Step 1 into the channels of the flat ceramic membrane. Heat the membrane in a 60°C oven for 6 hours to dry out the water in the slurry. The ceramic membrane is an alumina flat ceramic membrane with a pore size of 300-700 nm and a membrane channel cross-sectional size of 4×4 mm.

[0033] Step 3: The product from Step 2 was calcined in a muffle furnace to produce a ceramic membrane containing a composite catalyst in its channels. Calcination conditions were: heating to 500°C in an air atmosphere for 3 hours at a heating rate of 10°C / min. The composite catalyst consisted of copper oxide-loaded attapulgite and activated carbon.

[0034] Step 4: Encapsulate accessories at both ends of the ceramic membrane obtained in step 3 to obtain a ceramic membrane assembly encapsulating the catalyst. The accessories include a water outlet and a closing block. Grooves are provided on the opposite sides of the water outlet block and the closing block. The two ends of the ceramic membrane are respectively inserted into the grooves on the water outlet block and the closing block. A through hole connected to the grooves is provided on the water outlet block; the through hole serves as the water suction port of the ceramic membrane assembly; when negative pressure is applied to the water suction port, the treated wastewater is sucked into the ceramic membrane through the pores on the surface of the ceramic membrane, and reaches the water suction port through the dense pores inside the ceramic membrane and is then discharged; in this process, the full contact between the wastewater and the ceramic membrane assembly helps the catalytic oxidation reaction to proceed.

[0035] The test results of catalytic oxidation degradation of organic wastewater by the ceramic membrane assembly obtained in this example are as follows:

[0036] As shown in FIG2 , a dye (Rhodamine B) solution with a concentration of 5 mg / L was prepared as simulated wastewater; the ceramic membrane assembly prepared in this example was immersed in the simulated wastewater; and peroxymonosulfate was added to the simulated wastewater so that the concentration of peroxymonosulfate in the simulated wastewater reached 10 mg / L; a peristaltic pump was connected to the water inlet of the ceramic membrane assembly; the peristaltic pump was started to provide negative pressure to the water inlet of the ceramic membrane assembly, and the simulated wastewater was sucked out through the ceramic membrane assembly; during this process, the simulated wastewater entered the membrane channel of the ceramic membrane, and the monosulfate in the simulated wastewater fully contacted with the composite catalyst in the ceramic membrane, generating a large amount of active substances (sulfate radicals, hydroxyl radicals, etc.), which efficiently degraded the dye molecules in the solution and caused the simulated wastewater to fade.

[0037] As can be seen from FIG. 2 , the color of the water outputted by the ceramic membrane assembly completely disappears, indicating that the ceramic membrane assembly provided in this embodiment has excellent ability to catalyze and oxidize the degradation of dye wastewater.

[0038] Example 2

[0039] A ceramic membrane module based on a composite catalyst is prepared as follows:

[0040] Step 1: Add 50g of attapulgite and 1g of activated carbon to 20mL of a 10g / L copper nitrate solution and ultrasonically mix for 6h. Then, soak for 24h to obtain a viscous catalyst precursor slurry. Powdered activated carbon was used.

[0041] Step 2: Inject the catalyst precursor slurry obtained in step 1 into the flat ceramic membrane channel using a syringe, and place the flat ceramic membrane with the slurry injected into the channel in a 60° C. oven for heat treatment for 6 hours to dry the moisture in the slurry.

[0042] Step 3: The product from Step 2 was calcined in a muffle furnace to produce a ceramic membrane containing a composite catalyst in its channels. Calcination conditions were: heating to 500°C in an air atmosphere for 3 hours at a heating rate of 10°C / min. The composite catalyst consisted of copper oxide-loaded attapulgite and activated carbon.

[0043] Step 4: Encapsulate accessories at both ends of the ceramic membrane obtained in step 3 to obtain a ceramic membrane assembly encapsulating the catalyst. The accessories include a water outlet and a closing block. Grooves are provided on the opposite sides of the water outlet block and the closing block. The two ends of the ceramic membrane are respectively inserted into the grooves on the water outlet block and the closing block. A through hole connected to the grooves is provided on the water outlet block; the through hole serves as the water suction port of the ceramic membrane assembly; when negative pressure is applied to the water suction port, the treated wastewater is sucked into the ceramic membrane through the pores on the surface of the ceramic membrane, and reaches the water suction port through the dense pores inside the ceramic membrane and is then discharged; in this process, the full contact between the wastewater and the ceramic membrane assembly helps the catalytic oxidation reaction to proceed.

[0044] Example 3

[0045] A ceramic membrane module based on a composite catalyst is prepared as follows:

[0046] Step 1: Add 10g of attapulgite and 1g of activated carbon to 20mL of a 50g / L copper nitrate solution and ultrasonically mix for 6h. Then, soak for 24h to obtain a viscous catalyst precursor slurry. Powdered activated carbon was used.

[0047] Step 2: Inject the catalyst precursor slurry obtained in step 1 into the flat ceramic membrane channel using a syringe, and place the flat ceramic membrane with the slurry injected into the channel in a 60° C. oven for heat treatment for 6 hours to dry the moisture in the slurry.

[0048] Step 3: The product from Step 2 was calcined in a muffle furnace to produce a ceramic membrane containing a composite catalyst in its channels. Calcination conditions were: heating to 500°C in an air atmosphere for 3 hours at a heating rate of 10°C / min. The composite catalyst consisted of copper oxide-loaded attapulgite and activated carbon.

[0049] Step 4: Encapsulate accessories at both ends of the ceramic membrane obtained in step 3 to obtain a ceramic membrane assembly encapsulating the catalyst. The accessories include a water outlet and a closing block. Grooves are provided on the opposite sides of the water outlet block and the closing block. The two ends of the ceramic membrane are respectively inserted into the grooves on the water outlet block and the closing block. A through hole connected to the grooves is provided on the water outlet block; the through hole serves as the water suction port of the ceramic membrane assembly; when negative pressure is applied to the water suction port, the treated wastewater is sucked into the ceramic membrane through the pores on the surface of the ceramic membrane, and reaches the water suction port through the dense pores inside the ceramic membrane and is then discharged; in this process, the full contact between the wastewater and the ceramic membrane assembly helps the catalytic oxidation reaction to proceed.

[0050] Comparative Example 1

[0051] A ceramic membrane assembly. The difference between this embodiment and embodiment 1 is that: no composite catalyst is immobilized, and it only includes a ceramic membrane, and closing blocks and water outlet blocks at both ends of the ceramic membrane.

[0052] The ceramic membrane modules prepared in Example 1, Example 2, Example 3 and Comparative Example 1 were subjected to comparative experiments on an aqueous solution contaminated with bisphenol A (BPA) as the target:

[0053] Each experiment used 100 mL of a 5 mg / L BPA solution as simulated wastewater. The corresponding ceramic membrane assembly was immersed in the simulated wastewater. Peroxymonosulfate was added to the simulated wastewater, bringing the concentration to 10 mg / L. A peristaltic pump was connected to the inlet of the ceramic membrane assembly. The pump was activated, applying negative pressure to the inlet, drawing the simulated wastewater through the assembly. Samples were taken at regular intervals after the operation to determine the concentration. The results are shown in Figure 3.

[0054] The removal rate of bisphenol A in the effluent water of the ceramic membrane assemblies prepared in Examples 1-3 is approximately over 90%, while the removal rate of bisphenol A in the effluent water of the ceramic membrane assemblies prepared in Comparative Example 1 is only about 40%, indicating that the membrane assemblies prepared in Examples 1-3 can effectively remove organic pollutants dissolved in water.

[0055] In Example 1, the amount of catalyst added was the largest, the copper nitrate concentration was the highest, and the effect was the best. In Example 2, the amount of catalyst added remained unchanged, the copper nitrate concentration was reduced, and the effect was second best. In Example 3, the amount of catalyst added was reduced, and the copper nitrate concentration remained unchanged, and the effect was the worst compared to Example 12. The main influencing factor is the catalyst content in the ceramic.

Claims

1. A ceramic membrane assembly based on a composite catalyst, characterized in that: It includes a ceramic membrane, a composite catalyst immobilized in the channel of the ceramic membrane, and a water outlet block and a closing block respectively fixed at both ends of the ceramic membrane; the water outlet block is provided with a water inlet connected to the channel in the ceramic membrane; the process of generating the composite catalyst and immobilizing it in the channel of the ceramic membrane is as follows: after adding the catalyst precursor slurry to the channel of the ceramic membrane blank, calcining is performed; the catalyst precursor slurry is obtained by adding attapulgite and activated carbon into a copper nitrate solution and impregnating them.

2. A ceramic membrane assembly based on a composite catalyst according to claim 1, characterized in that: The mass ratio of the attapulgite to the activated carbon is (10-50):1; the concentration of the copper nitrate solution is 10g / L-50g / L.

3. A ceramic membrane assembly based on a composite catalyst according to claim 1, characterized in that: The ceramic membrane is an alumina flat ceramic membrane with a membrane pore size of 300-700 nm and a membrane channel of 4×4 mm.

4. A ceramic membrane assembly based on a composite catalyst according to claim 1, characterized in that: The opposite sides of the water outlet block and the closing block are provided with grooves; the two ends of the ceramic membrane are respectively inserted into the grooves on the water outlet block and the closing block.

5. A method for preparing a ceramic membrane assembly based on a composite catalyst, characterized in that: The following steps are involved: Step 1: adding attapulgite and activated carbon into a copper nitrate solution for immersion to obtain a catalyst precursor slurry; The mass ratio of attapulgite to activated carbon is (10-50):1; the concentration of the copper nitrate solution is 10g / L-50g / L; Step 2: injecting the catalyst precursor slurry obtained in step 1 into the channel of the ceramic membrane and drying it; Step 3, calcining the product obtained in step 2 to obtain a ceramic membrane containing a catalyst in the channel; Step 4: Fix a water outlet block and a sealing block at both ends of the ceramic membrane obtained in step 3; the water outlet block is provided with a water inlet connected to the surface of the ceramic membrane.

6. The preparation method according to claim 5, characterized in that: The activated carbon is powdered activated carbon.

7. The preparation method according to claim 5, characterized in that: In step 1, the immersion time is greater than or equal to 12 hours.

8. The preparation method according to claim 5, characterized in that: The specific process of drying described in step 2 is to heat-treat the ceramic membrane blank injected with the catalyst precursor slurry at a temperature of 60° C. to 100° C. for 6 h to 8 h.

9. The preparation method according to claim 5, characterized in that: The calcination conditions in step three are: heating to 300°C to 500°C in an air atmosphere, calcination time is 3h, and heating rate is 5°C / min to 10°C / min.

10. A method for treating organic wastewater, characterized in that: The treatment process is as follows: adding persulfate to the treated organic wastewater; connecting the water inlet of the ceramic membrane assembly as described in any one of claims 1 to 4 to a negative pressure source through a pipeline and immersing the ceramic membrane assembly into the treated organic wastewater; starting the negative pressure source to pump out the treated organic wastewater through the ceramic membrane assembly; the treated organic wastewater undergoes a catalytic oxidation reaction in the ceramic membrane assembly, so that the organic pollutants are degraded and removed.

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