CaO-co catalyst material and preparation method and application thereof

Abstract

The application discloses a CaO-C@Co catalyst material and a preparation method thereof, and the preparation method comprises the following steps: (1) adopting a solvent thermal reaction to synthesize a Ca-MOF precursor; (2) immersing a soluble cobalt salt solution into the Ca-MOF precursor, drying, and then calcining at 750-850 DEG C for 2-3 hours under an inert atmosphere to obtain the CaO-C@Co catalyst material. The CaO-C@Co catalyst material has excellent cycle stability while efficiently catalyzing ozone to degrade organic pollutants, has important significance for promoting the practical application of the technology, and can be applied to catalyzing ozone oxidation to degrade organic pollutants in water.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a CaO-C@Co catalyst material, its preparation method, and its application. Background Technology

[0002] Triclosan (TCS), a broad-spectrum antibacterial agent, is widely used in personal care products such as toothpaste, soap, and hand sanitizer, as well as medical disinfection products. Due to its poor biodegradability in traditional wastewater treatment processes, triclosan is frequently detected in environmental water bodies, sludge, and even organisms. Triclosan has been proven to have endocrine-disrupting activity, potentially causing photosensitive contact dermatitis, affecting muscle function, and exhibiting bioaccumulation, posing a potential threat to ecosystems and human health.

[0003] Advanced oxidation technologies (AOPs) are effective methods for removing recalcitrant organic pollutants from water. Among them, catalytic ozonation technology uses a solid catalyst to convert ozone (O3) into reactive oxygen species (ROS), such as hydroxyl radicals (·OH) and superoxide radicals (·O2). - These technologies, such as […], significantly improve the efficiency of oxidative removal of organic matter.

[0004] Alkaline metal oxides (such as CaO and MgO) exhibit good catalytic activity due to their strongly alkaline surface sites, which promote ozone decomposition. For example, Chinese patent document CN115055174B discloses a Ca-based ozone oxidation catalyst for the deep treatment of saline organic wastewater, which consists of a support and a metal active component supported on the support, wherein the metal active component is calcium oxide. Chinese patent document CN104437546B discloses a heterogeneous ozone catalyst and its preparation method, which includes 36.4%-52.4% water slag powder, 9.1%-14.3% magnesium oxide (MgO), 18.2%-23.8% magnesium chloride hexahydrate (MgCl2·6H2O), 4.8%-9% foaming agent, and 9.1%-19% catalytically active mixture.

[0005] However, this strong alkalinity also makes it extremely easy to react with water and undergo hydration to form hydroxides (such as Ca(OH)2), which causes damage to the catalyst structure, loss of active components and a sharp decline in catalytic performance. This is the main bottleneck limiting its practical application.

[0006] Currently, there is limited research on improving the stability of calcium-based oxides. Existing technologies mostly focus on regulating their basicity or introducing transition metals to construct composite oxides to enhance activity, but there is a lack of effective strategies on how to fundamentally inhibit their hydration process.

[0007] Therefore, developing a calcium-based catalytic ozonation catalyst that combines high catalytic activity and excellent stability is of great significance for promoting the practical application of this technology. Summary of the Invention

[0008] This invention provides a CaO-C@Co catalyst material and its preparation method. Through ingenious structural design, "dual confinement" protection of the CaO active center is achieved. The CaO-C@Co catalyst material exhibits excellent cycle stability while efficiently catalyzing the degradation of organic pollutants by ozone.

[0009] The technical solution of the present invention is as follows:

[0010] A method for preparing a CaO-C@Co catalyst material includes the following steps:

[0011] (1) The Ca-MOF precursor was synthesized by solvothermal reaction;

[0012] (2) The soluble cobalt salt solution was impregnated onto the Ca-MOF precursor, dried, and then calcined at 750-850℃ for 2-3 h under an inert atmosphere to obtain the CaO-C@Co catalyst material.

[0013] The CaO-C@Co material prepared in this invention possesses a unique "dual confinement" structure. The internal carbon framework, derived from MOF pyrolysis, provides spatial confinement for CaO. While it cannot completely prevent the transformation of CaO to Ca(OH)₂, it effectively slows down the dissolution and loss of Ca(OH)₂. The outer surface-loaded layer of metallic Co nanoparticles preferentially adsorbs and activates ozone due to its stronger nonpolar interaction with ozone than with water. Simultaneously, it acts as a "protective shell," physically blocking water molecules from contacting the internal CaO, thus significantly inhibiting the hydration process of CaO. Furthermore, the alkaline sites provided by CaO promote the dissociation of water molecules to form protonated hydroxyl groups, increasing the solution pH and jointly promoting ozone decomposition; while metallic Co acts as an electron transfer center, directly reacting with ozone to generate superoxide radicals (·O₂). - It mainly consists of reactive oxygen species, which efficiently oxidize and degrade organic pollutants.

[0014] Preferably, step (1) includes: dissolving the calcium salt and organic ligand in a solvent and reacting them in a sealed container at 100-150°C for 10-15 h; cooling after the reaction is completed, collecting the precipitate and washing it, and drying it to obtain the Ca-MOF precursor.

[0015] Preferably, in step (1), the calcium salt is calcium nitrate; the organic ligand is 1,4-naphthalenedicarboxylic acid; and the solvent is a mixed solvent of N,N-dimethylformamide and ethanol, with a volume ratio of N,N-dimethylformamide to ethanol of 1-2:1.

[0016] Preferably, in step (2), the mass ratio of the Ca-MOF precursor to the soluble cobalt salt is 1:0.3-0.5.

[0017] Calcination temperature has a significant impact on the catalytic performance of catalysts. When the calcination temperature is too low, the organic ligands are not calcined completely, and when the calcination temperature is too high, the C skeleton may collapse, resulting in poor crystallization of active ingredients. Ultimately, both of these conditions will lead to unsatisfactory catalyst performance.

[0018] Preferably, in step (2), calcination is carried out under an inert atmosphere, with the temperature increased to 750-850℃ at a rate of 1-5℃ / min and held for 2-3 hours.

[0019] The present invention also provides a CaO-C@Co catalyst material, which is prepared by the above preparation method.

[0020] Preferably, the CaO-C@Co catalyst material comprises CaO, elemental Co, and C, wherein the C exists in an amorphous form.

[0021] Preferably, the X-ray diffraction pattern of the CaO-C@Co catalyst material has characteristic diffraction peaks at 2θ diffraction angles of 32.2°, 37.1°, 44.2°, 51.5°, and 53.8°.

[0022] The CaO-C@Co catalyst material exhibits a micron-sized cuboid morphology, inheriting the structure of the Ca-MOF precursor. Transmission electron microscopy and elemental mapping show that CaO is uniformly distributed in the amorphous carbon framework, while metallic Co nanoparticles are enriched on the material surface to form a coating layer.

[0023] This invention also provides the application of the CaO-C@Co catalyst material in the catalytic ozone oxidation degradation of organic pollutants in water.

[0024] Preferably, the application includes: adding the CaO-C@Co catalyst material to wastewater containing organic pollutants, and then introducing ozone-containing gas for catalytic degradation;

[0025] In wastewater containing organic pollutants, the concentration of organic pollutants is 1-50 mg / L; the catalyst dosage is 0.05-0.5 g / L; in ozone-containing gas, the ozone concentration is 5-20 mg / L, the injection rate is 0.1-0.6 L / min; and the initial pH is 6-8.

[0026] Further preferred embodiments include wastewater containing organic pollutants with an organic pollutant concentration of 20 mg / L; catalyst dosage of 0.2 g / L; ozone concentration of 8-10 mg / L in ozone-containing gas with an injection rate of 0.1-0.3 L / min; and initial pH of 6-8.

[0027] Preferably, the reaction time is 2-30 min.

[0028] Preferably, the organic pollutant is triclosan.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) High activity: The CaO-C@Co catalyst material exhibits excellent catalytic ozone oxidation activity for organic pollutants under near-neutral conditions, which is significantly higher than that of comparative catalysts such as CaO and CaO-C;

[0031] (2) High stability: Thanks to the dual protection mechanism of "carbon skeleton spatial confinement" and "surface Co layer water molecule barrier", the CaO-C@Co catalyst material retains a high activity rate after several consecutive uses. 2+ Less dissolution;

[0032] (3) Clear mechanism: The alkaline sites of CaO and the acidic / electron transfer sites of Co in the CaO-C@Co catalyst material work synergistically to promote the decomposition of ozone to generate O2. - The active oxygen species, mainly composed of reactive oxygen species, enable the efficient degradation of organic pollutants;

[0033] (4) Simple preparation and low cost: The MOF derivatization combined with the equal volume impregnation method is adopted. The process is simple and controllable, and no expensive raw materials or complex equipment are required. It is easy to prepare on a large scale. Attached Figure Description

[0034] Figure 1 The XRD pattern of the CaO-C@Co catalyst prepared in Example 1;

[0035] Figure 2 Scanning electron microscope (SEM) image of the CaO-C@Co catalyst prepared in Example 1;

[0036] Figure 3 Transmission electron microscopy (TEM) image of the CaO-C@Co catalyst prepared in Example 1;

[0037] Figure 4 Elemental mapping image of the CaO-C@Co catalyst prepared in Example 1;

[0038] Figure 5The graph shows a comparison of the removal performance of triclosan by ozone alone under the conditions of Example 1, Comparative Examples 1-6, and without catalyst.

[0039] Figure 6 The graph shows the changes in the triclosan removal rate of the four catalysts in Example 1 and Comparative Examples 1-3 during five cycles of use. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0041] Example 1: Preparation of CaO-C@Co catalyst

[0042] 16 mmol of calcium nitrate (Ca(NO3)2·4H2O) and 16 mmol of 1,4-naphthalenedicarboxylic acid were dissolved in a mixed solvent of 40 mL N,N-dimethylformamide and 20 mL ethanol, and the solution was sonicated for 30 minutes to form a clear solution. The solution was transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and reacted in an oven at 120 °C for 12 hours. After naturally cooling to room temperature, the white precipitate was collected by centrifugation, washed several times with ethanol until the supernatant was colorless, dried under vacuum at 80 °C for 12 hours, and then ground to obtain the Ca-MOF precursor.

[0043] A 1 mL ethanol solution containing 0.35 g of Co(NO3)2·6H2O was impregnated into 1.0 g of the above Ca-MOF powder using an equal-volume impregnation method. After standing at room temperature for 10 hours, the powder was dried under vacuum at 80 °C for 8 hours. The dried powder was then placed in a tube furnace and calcined at 800 °C under a nitrogen atmosphere at a rate of 5 °C / min for 2 hours. After natural cooling, black CaO-C@Co catalyst powder was obtained.

[0044] Equal volume impregnation refers to the impregnation method in which the volume of the impregnation liquid is equal to the pore volume of the solid support to prepare the supported catalyst.

[0045] Comparative Example 1: Preparation of CaO-C Catalyst

[0046] The Ca-MOF precursor prepared in Example 1 was placed directly in a tube furnace and calcined at 800 °C for 2 hours under a nitrogen atmosphere at a rate of 5 °C / min to obtain the CaO-C catalyst.

[0047] Comparative Example 2: Commercial CaO Catalyst

[0048] Commercially available analytical grade CaO powder was used directly as the catalyst.

[0049] Comparative Example 3: Preparation of CaCo-C Catalyst

[0050] 16 mmol of calcium nitrate (Ca(NO3)2·4H2O), 16 mmol of cobalt nitrate (Co(NO3)2·6H2O), and 16 mmol of 1,4-naphthalenedicarboxylic acid were dissolved in a mixed solvent of 40 mL N,N-dimethylformamide and 20 mL ethanol, and sonicated for 30 minutes to form a transparent solution. The solution was transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and reacted in an oven at 120 °C for 12 hours. After naturally cooling to room temperature, the white precipitate was collected by centrifugation, washed several times with ethanol until the supernatant was colorless, dried under vacuum at 80 °C for 12 hours, and ground to obtain the CaCo-MOF precursor. The prepared CaCo-MOF precursor was directly placed in a tube furnace and calcined at 800 °C for 2 hours under a nitrogen atmosphere at a rate of 5 °C / min to obtain the CaCo-C catalyst.

[0051] Comparative Example 4: Preparation of Co-C Catalyst

[0052] 16 mmol of cobalt nitrate (Co(NO3)2·6H2O) and 16 mmol of 1,4-naphthalenedicarboxylic acid were dissolved in a mixed solvent of 40 mL N,N-dimethylformamide and 20 mL ethanol, and sonicated for 30 minutes to form a transparent solution. The solution was transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene and reacted in an oven at 120 °C for 12 hours. After naturally cooling to room temperature, the white precipitate was collected by centrifugation, washed several times with ethanol until the supernatant was colorless, dried under vacuum at 80 °C for 12 hours, and ground to obtain the Co-MOF precursor. The prepared Co-MOF precursor was placed directly in a tube furnace and calcined at 800 °C for 2 hours under a nitrogen atmosphere at a rate of 5 °C / min to obtain the Co-C catalyst.

[0053] Comparative Examples 5-6: Preparation of catalysts using different calcination temperatures

[0054] The preparation process was the same as in Example 1. In Comparative Examples 5 and 6, only the calcination temperature in the second step was changed to 700℃ and 900℃, respectively, resulting in catalysts labeled CaO-C@Co-700 and CaO-C@Co-900.

[0055] The CaO-C@Co catalyst material prepared in Example 1 was characterized using a Smartlab SE intelligent multi-functional X-ray diffractometer from Rigaku Corporation. The test conditions were as follows: target source Cu, scanning speed of 2° / min, and scanning angle of 5-90°.

[0056] Surface morphology (SEM) was measured using a ZEISS Sigma 300 scanning electron microscope. The accelerating voltage during morphology imaging was 3 kV. The sample preparation method involved directly attaching the sample to conductive adhesive. The testing mode was secondary electron.

[0057] TEM and mapping elemental images were obtained using a FEI Talos F200x transmission electron microscope. The morphology was captured using a voltage of 200 kV, and the sample was prepared by placing the sample on a copper mesh.

[0058] Figure 1 The image shows the X-ray diffraction pattern of the CaO-C@Co catalyst material prepared in Example 1. As can be seen from the figure, the peaks of CaO-C@Co are obvious and sharp, indicating good crystallinity. Characteristic diffraction peaks of CaO (ICDD PDF#04-010-5778) appear at 2θ diffraction angles of 32.2°, 37.1°, and 53.8°, while characteristic diffraction peaks of metallic Co (ICDD PDF#04-004-8491) appear at 2θ diffraction angles of 44.2° and 51.5°. No obvious Ca(OH)₂ diffraction peaks are observed. The material is mainly composed of CaO, metallic Co, and trace amounts of CoO, with carbon existing in an amorphous form.

[0059] Figure 2 The image shows a scanning electron microscope (SEM) image of the CaO-C@Co catalyst material prepared in Example 1. The CaO-C@Co catalyst material exhibits a micron-sized cuboid morphology, inheriting the structure of the Ca-MOF precursor.

[0060] Figure 3 and Figure 4 These are transmission electron microscopy (TEM) images and elemental distribution mapping diagrams. CaO is uniformly distributed within the amorphous carbon framework, while metallic Co nanoparticles are enriched on the material surface to form a coating layer.

[0061] Application Example 1: Performance Test of Catalytic Ozonation Degradation of Triclosan

[0062] In a 250 mL glass reactor, a 20 mg / L triclosan solution (prepared with deionized water) was added, and the initial pH was adjusted to 7.0. A catalyst was added to bring the catalyst concentration to 0.2 g / L. Ozone (generated from oxygen via an ozone generator, gas phase concentration 10 mg / L) was introduced at a flow rate of 0.2 L / min, and the reaction was magnetically stirred for 6 minutes. Samples were taken at regular intervals, filtered through a 0.22 μm filter membrane, and the residual concentration of triclosan in the solution was determined by high-performance liquid chromatography (HPLC).

[0063] The removal efficiency of the catalysts prepared in Example 1 and Comparative Examples 1-6 for triclosan was tested according to the above method, and the results are as follows: Figure 5As shown, the CaO-C@Co catalyst in Example 1 exhibited the best performance, achieving a triclosan removal rate of 90.75% in 6 minutes.

[0064] Application Example 2: Catalyst Stability Cyclic Testing

[0065] The four catalysts from Application Example 1 and Comparative Examples 1-3, after reaction, were recovered by centrifugation, washed twice with deionized water, dried at 60°C, and directly used in the next triclosan degradation experiment. This process was repeated 5 times. The experimental conditions were exactly the same as in Application Example 1 each time.

[0066] The results are as follows Figure 6 As shown in Table 1.

[0067] Table 1. Concentrations of calcium and cobalt ions in triclosan solution during stability testing.

[0068]

[0069] In Table 1, the cumulative ion dissolution rate is the cumulative mass m of ions dissolved from the catalyst over multiple dissolutions. 离子 With the initial mass m of the catalyst 催化剂 The percentage.

[0070] The CaO-C@Co catalyst prepared in Example 1 still maintained a triclosan removal rate of 87.32% after the 5th cycle, and the cumulative dissolution rate of Ca²⁺ in the reaction solution was only 4.51%, which was much lower than that of CaO-C (12.76%) and CaO (34.83%), demonstrating its excellent stability.

[0071] The raw material of this invention is mainly inexpensive calcium salt, which can be synthesized through simple processes such as hydrothermal treatment, calcination, and impregnation, without the need for precious metals or complex equipment. The CaO-C@Co catalyst material, through innovative structural design, effectively solves the key problem of easy hydration and deactivation of calcium-based oxides in catalytic ozonation, achieving efficient and stable removal of triclosan from water. Its stability stems from the "dual-confined" structure of CaO-C@Co. Its activity originates from surface alkaline sites, the electron transfer reaction between metallic Co and ozone, the increased specific surface area of ​​CaO-C@Co, and its ability to generate free radicals on the surface. Experiments show that the CaO-C@Co prepared by this invention achieves a removal rate of over 90% for 20 mg / L triclosan. This low-cost and high-activity characteristic makes it highly promising for application in the field of water treatment.

[0072] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a CaO-C@Co catalyst material, characterized in that, Includes the following steps: (1) The Ca-MOF precursor was synthesized by solvothermal reaction; (2) The soluble cobalt salt solution was impregnated onto the Ca-MOF precursor, dried, and then calcined at 750-850 °C for 2-3 h under an inert atmosphere to obtain the CaO-C@Co catalyst material.

2. The method for preparing the CaO-C@Co catalyst material according to claim 1, characterized in that, Step (1) includes: dissolving calcium salt and organic ligand in solvent and reacting in a sealed container at 100-150℃ for 10-15h; cooling after the reaction is completed, collecting the precipitate and washing it, and drying it to obtain the Ca-MOF precursor.

3. The method for preparing the CaO-C@Co catalyst material according to claim 2, characterized in that, In step (1), the calcium salt is calcium nitrate; the organic ligand is 1,4-naphthalenedicarboxylic acid; and the solvent is a mixed solvent of N,N-dimethylformamide and ethanol, with a volume ratio of N,N-dimethylformamide to ethanol of 1-2:

1.

4. The method for preparing the CaO-C@Co catalyst material according to claim 1, characterized in that, In step (2), the mass ratio of Ca-MOF precursor to soluble cobalt salt is 1:0.3-0.

5.

5. The method for preparing the CaO-C@Co catalyst material according to claim 1, characterized in that, In step (2), calcination is carried out under an inert atmosphere, with the temperature increased to 750-850 ℃ at a rate of 1-5 ℃ / min and held for 2-3 h.

6. A CaO-C@Co catalyst material, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The CaO-C@Co catalyst material according to claim 6, characterized in that, The CaO-C@Co catalyst material comprises CaO, elemental Co, and C, wherein the C exists in an amorphous form.

8. The CaO-C@Co catalyst material according to claim 6 or 7, characterized in that, The X-ray diffraction pattern of the CaO-C@Co catalyst material has characteristic diffraction peaks at 2θ diffraction angles of 32.2°, 37.1°, 44.2°, 51.5°, and 53.8°.

9. The application of the CaO-C@Co catalyst material according to any one of claims 6-8 in the catalytic ozone oxidation degradation of organic pollutants in water.

10. The application according to claim 9, characterized in that, include: The CaO-C@Co catalyst material was added to wastewater containing organic pollutants, and ozone-containing gas was introduced for catalytic degradation. In wastewater containing organic pollutants, the concentration of organic pollutants is 1-50 mg / L; the catalyst dosage is 0.05-0.5 g / L; in ozone-containing gas, the ozone concentration is 5-20 mg / L, the injection rate is 0.1-0.6 L / min; and the initial pH is 6-8.

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