Copper-based layered metal catalyst rich in oxygen vacancies as well as preparation method and application of copper-based layered metal catalyst

Abstract

The invention belongs to the technical field of high-salt organic wastewater treatment, and particularly relates to a copper-based layered metal catalyst rich in oxygen vacancies as well as a preparation method and application of the copper-based layered metal catalyst. In order to efficiently degrade refractory organic pollutants, copper nitrate, cobalt nitrate and ferric nitrate are used as metal sources, urea is used as a structure regulating agent, and the catalyst with a layered structure is prepared through a hydrothermal method. And oxygen vacancies are introduced into crystal lattices through reducing gas generated by urea decomposition, so that the electron transfer capability of the catalyst and the persulfate activation performance are remarkably improved. In a high-salt environment, singlet oxygen (1O2) is generated by activating persulfate in a non-free radical path so as to degrade organic pollutants which are difficult to degrade.

Description

Technical Field

[0001] This invention belongs to the field of high-salt organic wastewater treatment technology, specifically relating to a copper-based layered metal catalyst rich in oxygen vacancies, its preparation method, and its application. Background Technology

[0002] High-salinity organic wastewater is widely found in industries such as petrochemicals, pharmaceuticals, printing and dyeing, and coal chemicals, and is often accompanied by high concentrations of inorganic salt ions (such as Na+). + Cl - SO4 2- This type of wastewater contains recalcitrant organic compounds (such as polycyclic aromatic hydrocarbons and heterocyclic compounds). Its complex composition and challenging treatment pose serious risks; direct discharge without treatment will severely harm the ecosystem. Although membrane processes and thermal concentration are widely used for the resource recovery of high-salinity wastewater, the presence of residual organic matter can cause membrane fouling or crystallization interference, reducing membrane lifespan and the purity of salt byproduct extraction. Therefore, efficiently removing recalcitrant organic matter before concentration is crucial for improving overall treatment efficiency.

[0003] Advanced oxidation processes (AOPs) are considered an effective means of removing recalcitrant organic pollutants (ROS) due to their ability to generate highly reactive reactive species (ROS). Among them, persulfate-based AOP systems (such as PMS) show significant advantages in treating recalcitrant organic pollutants due to their high oxidation potential and long lifetime of active species. However, in high-salt environments, common anions (such as SO42-) can cause adverse reactions. 2- NO3 - Cl - CO3 2- Radicals (such as ions) can rapidly quench free radicals, reduce system activity, and generate toxic byproducts. Therefore, exploring more selective and ion-resistant non-radical pathways has become a research hotspot.

[0004] In recent years, singlet oxygen ( 1 The O2-dominated non-radical mechanism has been proven to effectively bypass the quenching effect of inorganic ions on free radicals. Constructing a non-radical mechanism with oxygen vacancies (O2)... V Transition metal oxides with defects are the key to achieving... 1 Key strategies for efficient O2 generation. Oxygen vacancies not only enhance the catalyst's adsorption and electron transfer capabilities for persulfate, but also promote O–O bond breaking and induce… 1 Selective O2 release enables efficient degradation. Based on this, a copper-based substrate metal catalyst with oxygen vacancies is constructed using a urea-controlled hydrothermal method. The oxygen vacancies are introduced through reducing gases such as ammonia generated from urea decomposition under hydrothermal high temperature and high pressure conditions, providing an effective solution for non-radical oxidation in high-salt environments. Summary of the Invention

[0005] This invention addresses the aforementioned problems by providing a copper-based, oxygen-vacancy-rich, layered metal catalyst, its preparation method, and its applications. Based on a defect engineering strategy, a copper-based, layered metal oxide catalyst is constructed, which generates singlet oxygen via persulfate activation of a non-radical pathway in a high-salt environment. 1 O2 is used to degrade recalcitrant organic pollutants. During the catalyst synthesis process, a reducing gas is introduced through urea decomposition to regulate the generation of oxygen vacancies in the crystal structure, thereby increasing the electron density on the catalyst surface and the activation capacity of persulfate, achieving efficient oxidative degradation of recalcitrant organic pollutants in a high-salt environment.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a copper-based layered metal catalyst rich in oxygen vacancies, which has a radially aggregated layered structure with multiple lamellar bundles extending outward around the cluster core to form an open framework. This framework provides a large external surface area and constitutes interconnected mass transfer channels. Based on oxygen species obtained by XPS O 1s fitting, the oxygen vacancy content accounts for 70%~85% of the total oxygen species. It is prepared by hydrothermal reaction using copper, cobalt, and iron nitrates as metal precursors and urea as a ligand and reducing agent. Urea decomposes under high-temperature hydrothermal conditions to generate reducing gases such as ammonia, inducing the formation of oxygen vacancies in the catalyst lattice.

[0008] This invention also provides a method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst, comprising the following steps:

[0009] Urea was added to a mixed solution of copper nitrate, cobalt nitrate, and ferric nitrate. After stirring in a water bath, a hydrothermal reaction was carried out. After the reaction was completed and cooled, the resulting precipitate was washed, vacuum dried, ground, and sieved to obtain a copper-based layered metal catalyst.

[0010] Furthermore, the total molar ratio of urea to copper nitrate, cobalt nitrate, and ferric nitrate is 1 to 12:1.

[0011] Furthermore, the molar ratio of copper nitrate, cobalt nitrate, and ferric nitrate is 1:1:1.

[0012] Furthermore, the hydrothermal reaction is carried out at a temperature of 110~130℃ for 10~14 hours.

[0013] Furthermore, the vacuum drying temperature is 60°C and the time is 12 hours.

[0014] This invention also provides an application of a copper-based, oxygen-vacancy-rich metal catalyst for activating persulfate degradation of recalcitrant organic pollutants.

[0015] Furthermore, the method for activating persulfate to degrade recalcitrant organic pollutants is as follows:

[0016] The reaction was carried out in a high-salt environment (inorganic salt concentration not less than 200 mM). The concentration of potassium persulfate (PMS) in the reaction system was 0.1–1.0 mM, and the catalyst dosage was 0.05–0.2 g·L⁻¹. Singlet oxygen was generated by activating PMS via a non-radical pathway. 1 O2) enables the oxidative degradation of organic pollutants.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] Compared to traditional methods that use hydrogen roasting or sodium borohydride reduction to create oxygen vacancies, this invention uses urea to regulate the release of reducing gas, inducing oxygen vacancies in situ during the hydrothermal process without secondary treatment. This significantly improves the electron transfer capacity and persulfate activation performance of the catalyst. It also offers advantages such as low material cost, low risk, and environmental friendliness.

[0019] Compared to typical free radical AOP systems, traditional systems show a significant decrease in efficiency in high-salt wastewater. However, the catalyst of this invention relies on singlet oxygen in a non-radical pathway for oxidation, avoiding the problem of free radical quenching by inorganic ions and maintaining high efficiency even under high-salt conditions. It can even operate in environments containing 200 mM inorganic salts (SO42-). 2- NO3 - Cl - CO3 2- Even in high-salt systems, this catalytic system maintains a phenol degradation efficiency of 77.6%–100%. It possesses advantages such as high reaction selectivity and strong salt tolerance, providing a novel, efficient, and stable catalytic oxidation pathway for the deep removal of recalcitrant pollutants from high-salt organic wastewater. Attached Figure Description

[0020] Figure 1 The X-ray photoelectron spectroscopy (XPS) O 1s spectrum of the oxygen vacancy content of the catalyst prepared in Example 1 of this invention and the electron paramagnetic resonance (EPR) spectrum used to detect the oxygen vacancy signal are shown.

[0021] Figure 2 The image shown is a scanning electron microscope (SEM) image of the catalyst obtained in Example 1 of this invention.

[0022] Figure 3 The degradation curve of phenol in Example 2 of this invention;

[0023] Figure 4 The graph shows the degradation effect of phenol on different types of inorganic salt (200mM) systems in Example 3 of the present invention.

[0024] Figure 5The free radical quenching experimental results of the catalyst prepared in Example 1 of this invention and the electron paramagnetic resonance (EPR) spectrum used to detect reactive oxygen species in the reaction are shown. Detailed Implementation

[0025] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0026] Example 1

[0027] Copper nitrate (Cu(NO3)2·3H2O), cobalt nitrate (Co(NO3)2·6H2O), and ferric nitrate (Fe(NO3)3·9H2O) in a molar ratio of 1:1:1, totaling 1 mmol, were dissolved in 60 mL of deionized water and magnetically stirred to form a homogeneous mixture. 3 mmol of urea was added, and the mixture was stirred in a water bath at 50°C for 30 min. The mixture was then transferred to a 100 mL stainless steel reactor lined with polytetrafluoroethylene (PTFE) and subjected to hydrothermal reaction at 120°C for 12 h in a homogeneous reactor. After the reaction was completed and cooled, the resulting precipitate was washed five times each with anhydrous ethanol and water until the supernatant was colorless. The washed product was vacuum dried at 60°C for 12 h and then ground through a 200-mesh sieve to obtain a copper-based layered metal catalyst (denoted as Urea-3).

[0028] By adjusting the molar ratio of urea to total metal (1, 3, 6, 12), samples Urea-1, Urea-3, Urea-6, and Urea-12 were obtained, respectively. With increasing urea concentration, the oxygen vacancy content first increased and then decreased, with Urea-3 exhibiting the highest oxygen vacancy content and a distinct layered structure. Figure 1 and Figure 2 Analysis showed that the oxygen vacancy content of Urea-3 accounted for 70%~85% of the total oxygen species. In the X-ray photoelectron spectroscopy (XPS) O 1s spectrum, the oxygen vacancy peak was located at approximately 531.3 eV, and in the electron paramagnetic resonance (EPR) signal, it was located at g=2.003.

[0029] Example 2

[0030] Take 10 mg·L -1 100 mL of phenol solution was placed in a 250 mL beaker, and 0.65 mM PMS and 0.1 g·L⁻¹ were added. -1 Urea-1, Urea-3, Urea-6, and Urea-12 catalysts were used. The reaction was carried out at 25°C under magnetic stirring. Samples were taken every 5 minutes, filtered (using a 0.22 μm filter membrane), and the residual phenol concentration was measured. The results are as follows: Figure 3As shown, the Urea-3 catalyst can achieve 91.2% phenol degradation within 30 min. The catalytic performance of the samples with different urea ratios is in the order of Urea-3 > Urea-6 > Urea-1 > Urea-12, which is consistent with the trend of oxygen vacancy content.

[0031] Example 3

[0032] Take 10 mg·L -1 100 mL of phenol solution was placed in a 250 mL beaker. Inorganic salts were added to the beaker to bring the concentration of the corresponding inorganic anions in the solution to 200 mM. The inorganic anions included SO42-. 2- NO3 - Cl - CO3 2- (Each inorganic salt system was prepared separately as an independent control experiment). Then, 0.65 mM PMS and 0.1 g·L⁻¹ were added. -1 The Urea-3 catalyst was used. The reaction conditions were the same as in Example 2. The results are as follows: Figure 4 As shown, the phenol removal rate remained within the range of 77.6% to 100% within 30 minutes in all salt ion systems, demonstrating that the catalyst of this invention maintains excellent activity and salt resistance even under high ionic strength conditions.

[0033] Example 4

[0034] Based on Example 2, different quenchers were added to the reaction system: methanol (MeOH, 300 mM), tert-butanol (TBA, 300 mM), p-benzoquinone (p-BQ, 5 mM), and L-histidine (L-His, 10 mM). All other conditions remained the same. Results Figure 5 As shown, the degradation rate decreased from 91.2% to 33.4% after the addition of MeOH, was slightly affected by the addition of TBA to 88.6%, moderately decreased to 45.3% after the addition of p-BQ, and almost completely inhibited to 9.1% after the addition of L-His. This indicates that the main reactive oxygen species in the system is singlet oxygen.

[0035] Electron paramagnetic resonance (EPR) was used to analyze the reaction system. DMPO–O2 was detected in methanol solution using DMPO as a spin trapping agent. •- Characteristic signal, typical of SO42- detected in aqueous solution. - / •OH quartet signal (1:2:2:1); when TEMP is used as a spin trap, a 1:1:1 triplet signal is observed, indicating the presence of singlet oxygen in the system. 1 O2).

[0036] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0037] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A copper-based, layered metal catalyst rich in oxygen vacancies, characterized in that, The catalyst has a radially aggregated layered structure, with multiple lamellar bundles extending outward around the cluster core to form an open framework. This framework provides a large external surface area and constitutes interconnected mass transfer channels. Based on the oxygen species obtained by XPS O 1s fitting, the oxygen vacancy content accounts for 70%~85% of the total oxygen species. It is prepared by hydrothermal reaction using copper, cobalt, and iron nitrates as metal precursors and urea as a ligand and reducing agent.

2. The method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst according to claim 1, characterized in that, Includes the following steps: Urea was added to a mixed solution of copper nitrate, cobalt nitrate, and ferric nitrate. After stirring in a water bath, a hydrothermal reaction was carried out. After the reaction was completed and cooled, the resulting precipitate was washed, vacuum dried, ground, and sieved to obtain a copper-based layered metal catalyst.

3. The method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst according to claim 2, characterized in that, The total molar ratio of urea to copper nitrate, cobalt nitrate, and ferric nitrate is 1~12:

1.

4. The method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst according to claim 3, characterized in that, The molar ratio of copper nitrate, cobalt nitrate, and ferric nitrate is 1:1:

1.

5. The method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst according to claim 2, characterized in that, The hydrothermal reaction is carried out at a temperature of 110~130℃ for 10~14 hours.

6. The method for preparing a copper-based, oxygen-vacancy-rich, layered metal catalyst according to claim 2, characterized in that, The vacuum drying temperature is 60°C and the time is 12 hours.

7. The application of the oxygen-vacancy-rich copper-based layered metal catalyst according to claim 1, characterized in that, It is used to activate persulfate to degrade recalcitrant organic pollutants.

8. The application of the oxygen-vacancy-rich copper-based layered metal catalyst according to claim 7, characterized in that, The method for activating persulfate to degrade recalcitrant organic pollutants is as follows: The reaction is carried out in a high-salt environment, with the concentration of persulfate in the reaction system being 0.1–1.0 mM and the catalyst dosage being 0.05–0.2 g·L⁻¹. Persulfate is activated through a non-radical pathway to generate singlet oxygen, thereby achieving the oxidative degradation of organic pollutants.

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