Cobalt-aluminum-zinc hydrotalcite assembled film as well as preparation method and application thereof

Abstract

The invention relates to a cobalt-aluminum-zinc hydrotalcite assembled membrane catalyst as well as a preparation method and application thereof. The catalyst is composed of an assembled film and cobalt-aluminum-zinc hydrotalcite, wherein the molar ratio of Co to Al to Zn in the cobalt-aluminum-zinc hydrotalcite is 1: (1-2): (1-2), and the mass ratio of the cobalt-aluminum-zinc hydrotalcite in the assembled membrane catalyst is 35%-55%. Through a specific vacuum-assisted flocculation assembly method, the characteristic of high specific surface area of the hydrotalcite material is maintained, and rich active sites are provided for the processes of catalytic reaction, adsorption separation and the like. The preparation process of the catalyst comprises preparation of CoAlZn-LDH and preparation of a CoAlZn-LDH assembled film, the process not only improves the catalytic efficiency, but also optimizes the mechanical strength and thermal stability of the catalyst through introduction of the assembled film, and can maintain the stability of the structure and performance under harsh conditions.

Description

Technical Field

[0001] The present invention relates to the fields of environmental engineering and water treatment, and relates to a cobalt-aluminum-zinc hydrotalcite assembled membrane, a preparation method and applications thereof, and in particular to a cobalt-aluminum-zinc hydrotalcite assembled membrane (CoAlZn-LDH assembled membrane) for activating peroxymonosulfate (PMS) to efficiently degrade antibiotics in water, and the preparation and applications thereof. Background Art

[0002] Since the 20th century, antibiotics have been widely used in agriculture, food processing, planting, medicine, and animal husbandry, offering promising development prospects. However, the natural degradation capacity of antibiotics in the environment is limited, resulting in their residues in water, soil, sediments, and biosolids, which in turn cause a series of environmental and health problems. Research has shown that traditional biological treatment methods often fail to effectively remove antibiotics, with removal rates typically below 40%. For example, the activated sludge process, a commonly used biological treatment method in wastewater treatment plants, has a low antibiotic degradation efficiency, typically only 10% to 30%. This is because the antimicrobial properties of some antibiotics inhibit the activity of microorganisms in the activated sludge, resulting in low degradation efficiency. Although biofilm processes are more stable than activated sludge processes, they are still limited by the antimicrobial properties of antibiotics and the degradation capacity of microorganisms. Studies have shown that adsorbents such as activated carbon or clay can effectively remove antibiotics from water. However, adsorption methods only transfer the contaminants and do not achieve true degradation, resulting in low removal efficiencies, typically below 20%. Given these issues, the development of new, cost-effective, and efficient technologies to address the problem of antibiotic contamination in aquatic environments is urgent.

[0003] In the field of hydrotalcite-activated PMS for antibiotic degradation, a research team prepared ultrathin nickel-aluminum hydrotalcite (NiAl-LDH) (thickness of about 4.3nm) and found that it has a super-adsorption phenomenon for sulfonamide antibiotics, which promotes the degradation of such pollutants in the PMS / ultrathin NiAl-LDH system, and its degradation rate is about 39 times that of the PMS / ordinary NiAl-LDH system. However, due to the high surface energy of ultrathin nanosheets, it is easy to restack through van der Waals forces, resulting in the masking of active sites, a decrease in specific surface area, and affecting performance. The researchers used a simple co-precipitation method to prepare layered ZnFe-LDH, using the amphoteric oxide ≡Zn(OH)2 in the hydrotalcite structure to exert a "sacrificial agent effect" and successfully constructed a "neutral microenvironment" with a buffering effect on the surface of the hydrotalcite. Under neutral or alkaline conditions, ≡Zn(OH)2 will compete to consume the OHˉ adsorbed on the catalyst surface, significantly reducing the ≡Fe 3+ The probability of hydrolysis reaction with adsorbed OHˉ increases ≡Fe 3+ The probability of activating PMS to generate ≡FeIV=O; under acidic conditions, ≡Zn(OH) can also compete and consume H+ adsorbed on the catalyst surface, effectively inhibiting the formation of ≡FeIV =O and H + Side reactions occur, promoting surface ≡Fe 3+ Catalyzes PMS to continuously generate ≡Fe IV =O, achieving efficient degradation of antibiotics in a wide pH range of 3.0 to 11.0. However, due to its low mechanical strength, ultra-thin thickness may weaken the mechanical stability of the material, and structural collapse may occur during cyclic use or under high pressure conditions.

[0004] Professor Bian Zhaoyong's team used nanofiber Co3O4 and layered fluorine-free MXene (ff-Ti3C2Tx) to self-assemble to prepare nanofiber layered structure ff-Ti3C2Tx-Co3O4, which was used to activate PMS to degrade antibiotics. The material showed excellent performance in activating PMS to degrade antibiotics in the pH range of 4 to 10 and was resistant to ion interference. The efficiency of ff-Ti3C2Tx-Co3O4 membrane prepared by vacuum filtration remained above 95% within 90 minutes. Considering the fluorine-free MXene (ff-Ti3C2Tx x ) Although it avoids the surface defects caused by HF etching, it is still susceptible to oxidation (especially in high temperature, humidity or electrochemical cycling), which may lead to a decrease in conductivity. Summary of the Invention

[0005] The present invention provides a cobalt-aluminum-zinc hydrotalcite assembled film catalyst (CoAlZn-LDH assembled film). Another object is to provide a method for preparing the catalyst. Yet another object is to provide the use of the cobalt-aluminum-zinc hydrotalcite assembled film catalyst in activated polystyrene-sulfonate (PMS) for the efficient degradation of antibiotics in water. The present invention offers advantages such as ease of operation, low cost, and high degradation efficiency.

[0006] The technical solution of the present invention is: a hydrotalcite assembled film catalyst (CoAlZn-LDH assembled film), characterized in that the catalyst is composed of an assembled film and cobalt aluminum zinc hydrotalcite; wherein the molar ratio of Co:Al:Zn in the cobalt aluminum zinc hydrotalcite is 1:(1~2):(1~2), and the mass proportion of the cobalt aluminum zinc hydrotalcite in the assembled film catalyst is 35% to 55%.

[0007] The present invention also provides a method for preparing the above-mentioned hydrotalcite assembled film catalyst, the specific steps of which are as follows:

[0008] (1) Preparation of CoAlZn-LDH: Cobalt nitrate, aluminum nitrate, and zinc nitrate were weighed separately, dissolved in deionized water, and bubbled in nitrogen for a certain period of time to form a uniform solution; then the pH of the uniform solution was adjusted to 7-9 with hydrochloric acid and sodium hydroxide; the resulting suspension was transferred to a reactor, hydrothermally treated at a certain temperature for a period of time, and the bottom precipitate was collected; washed with deionized water and anhydrous ethanol, and dried in an oven to obtain CoAlZn-LDH;

[0009] (2) Preparation of CoAlZn-LDH assembled membrane: CoAlZn-LDH was dispersed in deionized water under ultrasonic conditions to obtain a suspension; the suspension was then vacuum filtered through a PES membrane substrate and dried in an oven to obtain a hydrotalcite assembled membrane catalyst (CoAlZn-LDH assembled membrane).

[0010] Preferably, the cobalt nitrate in step (1) is cobalt nitrate hexahydrate Co(N03)2·6H2O, the aluminum nitrate is aluminum nitrate nonahydrate Al(N03)3·9H2O, and the zinc nitrate is zinc nitrate tetrahydrate Zn(N03)2·4H2O; the molar ratio of cobalt nitrate hexahydrate, aluminum nitrate nonahydrate and zinc nitrate tetrahydrate is 1:(1-2):(1-2); the bubbling time in nitrogen is 10-40 min; the concentrations of hydrochloric acid and sodium hydroxide are both 5-15 M; the temperature of the hydrothermal treatment is 120°C-150°C, and the time of the hydrothermal treatment is 3-6 h; and the drying temperature in the oven is 50-75°C.

[0011] Preferably, in step (2), the mass ratio of CoAlZn-LDH to deionized water is 1:(150-400); and the temperature of the oven is 50-80°C.

[0012] The present invention also provides the use of the above-mentioned hydrotalcite assembled film catalyst in the degradation of antibiotics in wastewater, which specifically comprises the following steps: adding CoAlZn-LDH assembled film catalyst and PMS to simulated antibiotic wastewater, adjusting the antibiotic concentration to 10-40 mg·L -1 The pH of the simulated wastewater was adjusted to 3.00-11.00, placed in a constant temperature shaking bed, the speed was set to 150-250 rpm, and the shaking reaction was carried out at 20-55°C for 25-35 minutes.

[0013] The preferred PMS dosage concentration is 0.1-0.4 g·L -1 The catalyst dosage is 0.1~0.4g·L -1 .

[0014] The present invention provides the use of the above catalyst-activated PMS for selective oxidation and removal of antibiotics in wastewater. The specific steps are: adding CoAlZn-LDH assembled membrane catalyst and PMS to simulated antibiotic wastewater, wherein the pH of the simulated wastewater is adjusted to 3.00-11.00 and the antibiotic concentration is 10-40 mg·L -1 , PMS dosage concentration is 0.1~0.4g·L -1 The catalyst dosage is 0.1~0.4g·L -1 Place the plate in a constant temperature shaking bed, set the speed to 150-250 rpm, and shake at 20-55°C for 25-35 minutes.

[0015] Beneficial effects:

[0016] (1) The catalyst of the present invention is green and environmentally friendly, can be synthesized on a large scale, can be recycled and reused, and has high economic benefits.

[0017] (2) High specific surface area and abundant active sites: The hydrotalcite material itself has a high specific surface area, and this advantage is retained after being assembled into a thin film, providing abundant active sites for catalytic reactions, adsorption separation and other processes.

[0018] (3) Excellent mechanical properties and stability: The CoAlZn-LDH assembled film has good mechanical strength and thermal stability, and can maintain the stability of structure and performance under harsh conditions.

[0019] (4) The catalyst preparation process of the present invention is simple, the reaction conditions and process are easy to control, and the operation is convenient. DETAILED DESCRIPTION

[0020] In order to better understand the present invention, the present invention is further described below by way of examples. The examples are only used for explanation and do not constitute any limitation to the present invention.

[0021] Example 1:

[0022] (1) Prepare simulated wastewater containing ofloxacin, with an ofloxacin concentration of 10 mg·L -1 The pH was adjusted to 11 using 0.1 M NaOH and HCl.

[0023] (2) Preparation of catalyst, the steps are as follows:

[0024] (a) Preparation of CoAlZn-LDH: 0.291 g of Co(NO3)2·6H2O (0.001 mol), 0.375 g of Al(NO3)3·9H2O (0.001 mol), and 0.587 g of Zn(NO3)2·4H2O (0.002 mol) were weighed and dissolved in deionized water. The mixture was bubbled with nitrogen for 20 min to form a homogeneous solution. The pH of the homogeneous solution was then adjusted to 9 with 10 M hydrochloric acid and 15 M sodium hydroxide. The resulting suspension was transferred to a reactor and hydrothermally treated at 150°C for 5 h. The bottom precipitate was collected. After washing with deionized water and anhydrous ethanol, the mixture was dried in an oven at 75°C to obtain CoAlZn-LDH.

[0025] (b) Preparation of CoAlZn-LDH assembled membranes: 0.12 g of CoAlZn-LDH was dispersed in 18 mL of deionized water under ultrasonication. The suspension was then vacuum filtered through a 0.1 g PES membrane substrate to form a CoAlZn-LDH assembled membrane. The assembled membranes were dried in an oven at 65°C for subsequent use.

[0026] (3) Weigh 0.01 g of the catalyst CoAlZn-LDH assembled membrane prepared in this example, measure 100 ml of the simulated wastewater containing ofloxacin prepared in step (1), and put the CoAlZn-LDH assembled membrane into the simulated wastewater. The PMS dosage is 0.1 g·L -1 The reaction was incubated at 25°C with constant shaking for 35 minutes at a shaking speed of 250 rpm. High-performance liquid chromatography (HPLC) was used to determine the ofloxacin concentration. At a pH of 11, the OFL removal rate was 99.14%. The catalyst was recovered and reused five times under the same conditions, achieving a removal rate of 93.68%.

[0027] Example 2:

[0028] (1) Prepare simulated wastewater containing sulfamethoxazole, with a sulfamethoxazole concentration of 40 mg·L -1 , the pH was adjusted to 7 using 0.1 M NaOH and HCl.

[0029] (2) Preparation of catalyst, the steps are as follows:

[0030] (a) Preparation of CoAlZn-LDH: 0.291 g of Co(NH3)2·6H2O (0.001 mol), 0.75 g of Al(NH3)3·9H2O (0.002 mol), and 0.294 g of Zn(NH3)2·4H2O (0.001 mol) were weighed and dissolved in deionized water. The mixture was bubbled with nitrogen for 10 min to form a homogeneous solution. The pH of the homogeneous solution was then adjusted to 7 with 5 M hydrochloric acid and 10 M sodium hydroxide. The resulting suspension was transferred to a reactor and hydrothermally treated at 120°C for 6 h. The bottom precipitate was collected. After washing with deionized water and anhydrous ethanol, the mixture was dried in an oven at 65°C to obtain CoAlZn-LDH.

[0031] (b) Preparation of CoAlZn-LDH assembled membranes: 0.186 g of CoAlZn-LDH was dispersed in 45 mL of deionized water under ultrasonication. The suspension was then vacuum filtered through a 0.1 g PES membrane substrate to form a CoAlZn-LDH assembled membrane. The assembled membranes were dried in an 80°C oven for subsequent use.

[0032] (3) Weigh 0.04 g of the catalyst CoAlZn-LDH assembled membrane prepared in this example, measure 100 ml of the simulated wastewater containing sulfamethoxazole prepared in step (1), and put the CoAlZn-LDH assembled membrane into the simulated wastewater. The PMS dosage is 0.2 g·L -1 The reaction was then stirred at 55°C for 30 minutes with a shaking speed of 150 rpm. High-performance liquid chromatography (HPLC) was used to measure the sulfamethoxazole concentration. At a pH of 7, the SMX removal rate was 96.34%. The catalyst was recovered and reused five times under the same conditions, achieving a removal rate of 90.35%.

[0033] Example 3

[0034] (1) Prepare simulated wastewater containing tetracycline, with a tetracycline concentration of 20 mg·L -1 , the pH was adjusted to 3 using 0.1 M NaOH and HCl.

[0035] (2) Preparation of catalyst, the steps are as follows:

[0036] (a) Preparation of CoAlZn-LDH: 0.291 g of Co(N03)2·6H2O (0.001 mol), 0.563 g of Al(N03)3·9H2O (0.0015 mol), and 0.441 g of Zn(N03)2·4H2O (0.0015 mol) were weighed, dissolved in deionized water, and bubbled in nitrogen for 40 min to form a homogeneous solution. The pH of the homogeneous solution was then adjusted to 8 with 15 M hydrochloric acid and 5 M sodium hydroxide. The resulting suspension was transferred to a reactor, hydrothermally treated at 135 ° C for 3 h, and the bottom precipitate was collected. After washing with deionized water and anhydrous ethanol, CoAlZn-LDH was obtained after drying in a 50 ° C oven.

[0037] (b) Preparation of CoAlZn-LDH assembled membranes: 0.15 g of CoAlZn-LDH was dispersed in 60 mL of deionized water under ultrasonication. The suspension was then vacuum filtered through a 0.1 g PES membrane substrate to form a CoAlZn-LDH assembled membrane. The assembled membrane was dried in an oven at 50°C for subsequent use.

[0038] (3) Weigh 0.02 g of the catalyst CoAlZn-LDH assembled membrane prepared in this example, measure 100 ml of the tetracycline-containing simulated wastewater prepared in step (1), and put the CoAlZn-LDH assembled membrane into the simulated wastewater. The PMS dosage is 0.4 g·L -1 The reaction was then incubated at 20°C for 25 minutes with a constant shaking speed of 250 rpm. High-performance liquid chromatography (HPLC) was used to measure tetracycline concentration. At a pH of 3, the tetracycline removal rate was 99.14%. The catalyst was recycled and reused five times under the same conditions, achieving a removal rate of 92.61%.

Claims

1. A hydrotalcite assembled film catalyst, characterized in that The catalyst consists of an assembled membrane and cobalt-aluminum-zinc hydrotalcite; the molar ratio of Co:Al:Zn in the cobalt-aluminum-zinc hydrotalcite is 1:(1-2):(1-2), and the mass proportion of the cobalt-aluminum-zinc hydrotalcite in the assembled membrane catalyst is 35% to 55%.

2. A method for preparing the hydrotalcite assembled film catalyst according to claim 1, wherein the specific steps are as follows: (1) Preparation of CoAlZn-LDH: Cobalt nitrate, aluminum nitrate, and zinc nitrate were weighed separately, dissolved in deionized water, and bubbled in nitrogen for a certain period of time to form a uniform solution; then the pH of the uniform solution was adjusted to 7-9 with hydrochloric acid and sodium hydroxide; the resulting suspension was transferred to a reactor, hydrothermally treated at a certain temperature for a period of time, and the bottom precipitate was collected; washed with deionized water and anhydrous ethanol, and dried in an oven to obtain CoAlZn-LDH; (2) Preparation of CoAlZn-LDH assembled membrane: CoAlZn-LDH was dispersed in deionized water under ultrasonic conditions to obtain a suspension; the suspension was then vacuum filtered through a PES membrane substrate and dried in an oven to obtain a hydrotalcite assembled membrane catalyst (CoAlZn-LDH assembled membrane).

3. The method according to claim 2, characterized in that The cobalt nitrate in step (1) is cobalt nitrate hexahydrate Co(N03)2·6H2O, the aluminum nitrate is aluminum nitrate nonahydrate Al(N03)3·9H2O, and the zinc nitrate is zinc nitrate tetrahydrate Zn(N03)2·4H2O; the molar ratio of cobalt nitrate hexahydrate, aluminum nitrate nonahydrate and zinc nitrate tetrahydrate is 1:(1-2):(1-2); the bubbling time in nitrogen is 10-40 minutes; the concentrations of hydrochloric acid and sodium hydroxide are both 5-15M; the temperature of the hydrothermal treatment is 120°C-150°C, and the time of the hydrothermal treatment is 3-6 hours; and the drying temperature in the oven is 50-75°C.

4. The method according to claim 2, characterized in that In step (2), the mass ratio of CoAlZn-LDH to deionized water is 1:(150-400); and the temperature of the oven is 50-80°C.

5. Use of the hydrotalcite assembled membrane catalyst as claimed in claim 1 in degrading antibiotics in wastewater.

6. The use according to claim 5, wherein the specific steps are: adding CoAlZn-LDH assembled membrane catalyst and PMS to simulated antibiotic wastewater, adjusting the antibiotic concentration to 10-40 mg·L -1 The pH of the simulated wastewater was adjusted to 3.00-11.00, placed in a constant temperature shaking bed, the speed was set to 150-250 rpm, and the shaking reaction was carried out at 20-55°C for 25-35 minutes.

7. The use according to claim 5, characterized in that The PMS dosage concentration is 0.1~0.4g·L -1 The catalyst dosage is 0.1~0.4g·L -1 .