A method for catalytic microwave activation of persulfate to degrade organic wastewater

Abstract

The application provides a method for catalytic microwave activation of persulfate for degradation of organic wastewater, in which, lanthanide metal and eighth group transition metal oxide or composite oxide are used as catalysts, persulfate is catalytically activated under the action of microwaves, and organic pollutants in the organic wastewater are catalytically oxidized. The absorption rate of microwaves is improved, the catalytic activity of persulfate is synergistically enhanced by microwaves, the degradation effect on antibiotics and the like is further enhanced, and the treatment demand of people for the organic wastewater is met.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a method for catalytic microwave activation of persulfate to degrade organic pollutants in wastewater. Background Technology

[0002] Antibiotics are a class of chemical substances produced by microorganisms or higher plants and animals during their life processes, possessing antipathogenic or other activities. They have been widely used to prevent and treat human and animal diseases. However, due to improper disposal of excrement and waste drugs, as well as imperfect sewage treatment technologies, urban sewage, surface water, and groundwater contain organic pollutants such as antibiotics, causing harm to the environment, humans, and animals.

[0003] Persulfate (PS) mainly includes perdisulfate and permonsulfate. As a strong oxidant, PS has redox potentials of 2.01V and 1.82V, respectively. However, in degradation experiments, its direct reaction with organic pollutants suffers from low reaction rates and long reaction times. PS can currently be activated by various methods, such as heating, ultraviolet irradiation, alkaline activation, ultrasound, and metal ion activation. However, thermal activation requires very high amounts of heat energy. Metal ion activation is difficult to recover and prone to secondary pollution. Alkaline activation systems present problems such as wastewater retreatment and alteration of wastewater properties.

[0004] Microwave technology for environmental pollution control is a newly emerging research field in recent years, favored by researchers for its rapid, efficient, energy-saving, and pollution-free characteristics. Microwaves, as electromagnetic waves with strong penetrating power, offer several advantages. Firstly, their thermal effect enables microwave-activated persulfate methods to exhibit rapid heating, high degradation efficiency, short reaction time, and no secondary pollution. Secondly, the non-thermal effect of microwaves can cause the polar portion of the catalyst to oscillate rapidly, thereby weakening the chemical bonds in the molecule, lowering the activation energy of the reaction, and thus degrading organic pollutants, greatly improving the efficiency of microwave-activated persulfate. Currently, researchers have used microwave radiation to activate persulfate systems to degrade pollutants. However, the catalysts designed so far have not maximized the efficiency of microwave-activated persulfate, resulting in problems such as long treatment cycles and incomplete degradation of antibiotic wastewater.

[0005] Therefore, further development is needed to develop treatment methods that can rapidly and comprehensively catalytically oxidize and degrade wastewater containing organic pollutants such as antibiotics to meet current water treatment needs. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for catalytically activating persulfate to degrade organic wastewater. This method utilizes a catalyst to enhance microwave absorption, synergistically strengthening the catalytic activity against persulfate and improving its utilization rate. This further enhances the degradation effect on antibiotics and other substances, thus completing this invention.

[0007] The purpose of this invention is to provide a method for catalytically activating persulfate to degrade organic wastewater. In this method, a transition metal compound is used as a catalyst to catalytically activate persulfate under microwave action, thereby catalytically oxidizing organic pollutants in the organic wastewater.

[0008] The organic pollutant is selected from one or more of antibiotics and dyes, preferably one or more of quinolone antibiotics, tetracycline antibiotics and dyes, and more preferably one or more of ciprofloxacin, levofloxacin, tetracycline hydrochloride and rhodamine B.

[0009] The catalyst is selected from one or more of lanthanide metals and group VIII transition metal oxides or composite oxides, preferably one or more of lanthanum, iron, cobalt and nickel oxides or composite oxides, more preferably one or more of cobalt oxides and lanthanum-iron composite oxides, such as cobalt oxide or lanthanum ferrite LaFeO3.

[0010] The present invention also aims to provide a catalyst for the catalytic microwave activation of persulfate degradation of organic wastewater. The catalyst is obtained by dissolving a transition metal salt in a solvent, followed by a closed-loop high-temperature hydrothermal reaction under the action of a precipitant to obtain a catalyst precursor, which is then calcined.

[0011] The transition metal is selected from one or more of the lanthanides and Group VIII transition metals, preferably one or more of lanthanum, iron, cobalt and nickel, and more preferably one or more of cobalt, lanthanum and iron, such as lanthanum and iron, cobalt.

[0012] Another objective of this invention is to provide a method for preparing the catalytic microwave-activated persulfate degradation catalyst for organic wastewater. In this method, a transition metal salt is dissolved in a solvent, and under the action of a precipitant, a closed high-temperature hydrothermal reaction is carried out to obtain a catalyst precursor by sedimentation, which is then calcined to obtain the catalyst.

[0013] The method specifically includes the following steps:

[0014] Step 1: Dissolve the transition metal salt in a solvent, add a precipitant, and obtain a reaction solution;

[0015] Step 2: The reaction solution undergoes a hydrothermal reaction under closed high-temperature conditions, followed by separation, washing, and drying to obtain the catalyst precursor;

[0016] Step 3: Calcining the catalyst precursor to obtain the catalyst.

[0017] The method for catalytic microwave activation of persulfate degradation of organic wastewater provided by this invention has the following beneficial effects:

[0018] (1) In this invention, lanthanide metals and group VIII transition metal oxides or composite oxides are used as catalysts to improve the microwave activation performance of persulfate, increase the microwave absorption effect, and thus improve the removal effect of antibiotics, dyes, etc.

[0019] (2) In the cobalt oxide catalyst of the present invention, Co 3+ and Co 2+ These sites serve as microwave-activated catalytic and redox-activated catalytic active centers, respectively. The increased number of microwave-activated active centers enhances the catalyst's microwave absorption performance, maximizing both the microwave "hotspot" effect and non-thermal effects. The increased redox-activated active centers improve the utilization rate of persulfate and promote the generation of active species. The catalyst, with rationally controlled content of these two catalytic active sites, exhibits optimal degradation performance and mineralization efficiency for antibiotics such as ciprofloxacin.

[0020] (3) In the organic pollutant removal method of the present invention, the catalyst has a stable structure and performance after multiple cycles of use, and can continuously degrade organic pollutants.

[0021] (4) The catalyst in this invention has good catalytic activation performance. Under microwave action, it can catalyze the activation of persulfate to generate active groups such as sulfate radicals, hydroxyl radicals, superoxide radicals and singlet oxygen, thereby further improving the degradation rate and degradation efficiency of pollutants and meeting the treatment requirements of wastewater containing organic pollutants such as dyes and antibiotics. Attached Figure Description

[0022] Figure 1 The XRD pattern of the cobalt carbonate precursor prepared in Example 1 of the present invention is shown.

[0023] Figure 2 The M prepared in Examples 1-4 of the present invention are shown. 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 XRD pattern;

[0024] Figure 3 The M prepared according to Embodiment 1 of the present invention is shown. 6.6 P 3.4 The corrected diagram of the Rietveld structure;

[0025] Figure 4 The M prepared in Examples 1-4 of the present invention are shown. 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 XPS graph;

[0026] Figure 5 The cobalt carbonate precursor and M prepared in Examples 1-4 of this invention are shown. 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 SEM image;

[0027] Figure 6 Comparative Example 1 (MW+PS) and Comparative Example 2 (MW+M) of the present invention are shown. 6.9 P 3.1 ) and in Example 9, M 6.9 P 3.1 For catalyst (MW+PS+M) 6.9 P 3.1 A graph showing the change in total organic carbon content (TOC) over time when treating CIP wastewater.

[0028] Figure 7 Comparative Example 1 (MW+PS) and Comparative Example 2 (MW+M) of the present invention are shown. 6.9 P 3.1 ) and in Example 9, M 6.9 P 3.1 For catalyst (MW+PS+M) 6.9 P 3.1 After treating CIP wastewater for 10 minutes, the NH4+ in the solution... + NO3 - F - SO4 2- The content;

[0029] Figure 8 The XRD pattern of lanthanum ferrite LaFeO3 prepared in Example 5 of the present invention is shown.

[0030] Figure 9 The XPS image of lanthanum ferrite LaFeO3 prepared in Example 5 of this invention is shown.

[0031] Figure 10The XPS analysis chromatogram of O1 s in lanthanum ferrite LaFeO3 prepared in Example 5 of the present invention is shown.

[0032] Figure 11 This illustrates the La3d content in lanthanum ferrite LaFeO3 prepared according to Example 5 of the present invention. 3 / 2 and La3d 5 / 2 XPS analysis chart;

[0033] Figure 12 This illustrates the Fe 2p content in lanthanum ferrite LaFeO3 prepared in Example 5 of the present invention. 1 / 2 and Fe2p 3 / 2 XPS analysis chart;

[0034] Figure 13 The image shows a SEM image of lanthanum ferrite LaFeO3 prepared in Example 5 of the present invention. Detailed Implementation

[0035] The present invention will now be described in detail through specific embodiments, and the features and advantages of the present invention will become clearer and more explicit with these descriptions.

[0036] This invention provides a method for catalytically activating persulfate to degrade organic wastewater using microwave. In this method, a transition metal compound is used as a catalyst to catalytically activate persulfate under microwave action, thereby catalytically oxidizing organic pollutants in the wastewater.

[0037] The organic pollutant is selected from one or more of antibiotics and dyes, preferably one or more of quinolone antibiotics, tetracycline antibiotics and dyes, and more preferably one or more of ciprofloxacin, levofloxacin, tetracycline hydrochloride and rhodamine B.

[0038] The persulfate is selected from one or more of perbissulfates and permonsulfates, preferably one or more of ammonium persulfate, metal perbissulfates and metal permonsulfates, and more preferably potassium persulfate and / or sodium persulfate.

[0039] The molar ratio of organic pollutants to persulfate is (0.3-4.5) g:(0.05-0.8) mol, preferably (0.4-3.5) g:(0.05-0.6) mol, and more preferably (0.5-2.5) g:(0.1-0.4) mol. As the amount of persulfate increases, the degradation rate of organic pollutants in the wastewater gradually increases, but the degradation rate and degradation speed will not increase indefinitely when the amount of persulfate is excessive.

[0040] The molar ratio of the catalyst to persulfate is (2-65):1, preferably (2-55):1, more preferably (5-45):1, such as (5-25):1 or (30-45):1. As the amount of catalyst increases, the degradation rate of organic pollutants in the wastewater gradually increases, but when the amount of persulfate is excessive, the degradation rate tends to reach equilibrium.

[0041] The microwave power is 200-900W, preferably 350-850W, and more preferably 500-800W. When the microwave power reaches 200W or above, the degradation rate of organic pollutants is significantly improved, but above 900W, the degradation rate tends to reach equilibrium.

[0042] The catalyst is selected from one or more of lanthanide metals and group VIII transition metal oxides or composite oxides, preferably one or more of lanthanum, iron, cobalt and nickel oxides or composite oxides, more preferably one or more of cobalt oxides and lanthanum-iron composite oxides, such as cobalt oxide or lanthanum ferrite LaFeO3.

[0043] Preferably, in the cobalt oxide, the molar ratio of divalent cobalt to trivalent cobalt is (6.4-7.2):(2.8-3.6), more preferably (6.6-7.0):(3.0-3.4), and even more preferably (6.85-6.95):(3.05-3.15). Extensive experiments have shown that by adjusting the calcination temperature, the content of divalent and trivalent cobalt in the cobalt oxide can be controlled. When the ratio of divalent to trivalent cobalt is (6.85-6.95):(3.05-3.15), the catalytic activation effect on persulfate is best under microwave conditions, the persulfate reflection loss value is highest, it exhibits good microwave absorption performance, and the degradation effect on pollutants is optimal.

[0044] The pH value of the organic wastewater is 2.5-11.5, preferably 6-8, and more preferably 6.5-7.5. Within the above pH range, the degradation rate of pollutants can reach more than 80%, and within the pH range of 6.5-7.5, the degradation rate of pollutants can reach more than 93%.

[0045] This invention also provides a catalyst for the catalytic microwave activation of persulfate degradation of organic wastewater. The catalyst is obtained by dissolving a transition metal salt in a solvent, followed by a closed-loop high-temperature hydrothermal reaction under the action of a precipitant to obtain a catalyst precursor, which is then calcined.

[0046] In the transition metal salt, the transition metal is selected from one or more of the lanthanides and Group VIII transition metals, preferably one or more of lanthanum, iron, cobalt and nickel, more preferably one or more of cobalt, lanthanum and iron, such as lanthanum and iron and cobalt.

[0047] Preferably, the catalyst is cobalt oxide (Co3O4) or lanthanum ferrite (LaFeO3). In the cobalt oxide (Co3O4), the molar ratio of divalent cobalt to trivalent cobalt is (6.4-7.2):(2.8-3.6), preferably (6.6-7.0):(3.0-3.4), and more preferably (6.85-6.95):(3.05-3.15).

[0048] The present invention also provides a method for preparing the catalytic microwave-activated persulfate degradation catalyst for organic wastewater. In the method, a transition metal salt is dissolved in a solvent, and a closed high-temperature hydrothermal reaction is carried out under the action of a precipitant to obtain a catalyst precursor by sedimentation, which is then calcined to obtain the catalyst.

[0049] The method specifically includes the following steps:

[0050] Step 1: Dissolve the transition metal salt in a solvent, add a precipitant, and obtain a reaction solution.

[0051] In the transition metal salt, the transition metal is selected from one or more of the lanthanides and Group VIII transition metals, preferably one or more of lanthanum, iron, cobalt and nickel, more preferably one or more of cobalt, lanthanum and iron, such as lanthanum and iron and cobalt.

[0052] The solvent is selected from one or more of water and alcohol solvents, preferably one or more of water and alcohol solvents containing C1-C5 carbon atoms, more preferably one or more of water, ethylene glycol, ethanol, propanol and isopropanol, such as a mixed solvent of water and ethylene glycol, or a mixed solvent of water and ethanol.

[0053] The molar volume ratio of the transition metal salt to the solvent is (1.5-3.5) mmol:(20-70) mL, preferably (1.5-3.5) mmol:(25-60) mL, and more preferably (1.5-3.5) mmol:(30-50) mL.

[0054] The precipitant is selected from one or more of hydroxides, carbonates, bicarbonates and urea, preferably one or more of bicarbonates and urea, and more preferably ammonium bicarbonate and / or urea.

[0055] The ratio of the total molar amount of the transition metal salt to the molar amount of the precipitant is 1:(0.4-24), preferably 1:(0.8-18), and more preferably 1:(1.2-12).

[0056] Step 2: The reaction solution undergoes a hydrothermal reaction under closed high-temperature conditions, followed by separation, washing, and drying to obtain the catalyst precursor.

[0057] The hydrothermal reaction temperature is 120-220℃, preferably 130-200℃, and more preferably 140-180℃. The reaction time is 8-28h, preferably 10-26h, and more preferably 12-24h.

[0058] Step 3: Calcining the catalyst precursor to obtain the catalyst.

[0059] The roasting is carried out in an oxygen-containing atmosphere, such as air or oxygen.

[0060] The calcination temperature is 120-220℃, preferably 130-200℃, and more preferably 350-800℃. The reaction time is 1-6h, preferably 1.5-5h, and more preferably 2-4h.

[0061] In a preferred embodiment of the present invention, the catalyst for catalytic microwave activation of persulfate degradation of organic wastewater is cobalt oxide (Co3O4) or lanthanum ferrite (LaFeO3).

[0062] The cobalt oxide (Co3O4) was prepared by the following method: Cobalt nitrate was dissolved in a mixture of methanol and deionized water. Then, NH4HCO3 was added and stirred until dissolved. The solution was transferred to a polytetrafluoroethylene reactor liner and placed in a high-temperature, high-pressure hydrothermal stainless steel reactor. The reactor was heated at 160-200℃ for 20-26 hours. After centrifugation and washing with deionized water and ethanol, the solution was dried in a 6°C oven to obtain the cobalt carbonate precursor. The precursor was then calcined at 350-650℃ under an oxygen-containing atmosphere for 2-4 hours to obtain cobalt oxide (Co3O4).

[0063] Lanthanum ferrite LaFeO3 was prepared by the following method: Ferric nitrate, lanthanum nitrate, and anhydrous citric acid were dissolved in a mixture of water and ethanol. Urea was added and the mixture was stirred until dissolved. The solution was then transferred to a 100 mL sealed reactor and hydrothermally heated at 120-160 °C for 10-14 h. After centrifugation, washing, and drying, the mixture was calcined at 780-820 °C for 2-4 h under an oxygen atmosphere. It was then acid-washed with dilute hydrochloric acid, washed with deionized water, and dried to obtain lanthanum ferrite LaFeO3.

[0064] This invention uses lanthanide metals and Group VIII transition metal oxides or composite oxides as catalysts to catalyze the activation of persulfate to generate active groups such as sulfate radicals, hydroxyl radicals, superoxide radicals, and singlet oxygen, thereby improving the microwave activation performance of persulfate, increasing microwave absorption, and ultimately enhancing the removal efficiency of antibiotics, dyes, etc. In this method, the catalyst maintains a stable structure and performance after multiple cycles, allowing for continuous degradation of organic pollutants, reducing treatment costs, and meeting the treatment requirements for wastewater containing organic pollutants such as dyes and antibiotics.

[0065] Example

[0066] The composition and structure of different materials were characterized using an X-ray diffractometer (D8 Advance), and the results were obtained at 5°·min. -1 The scanning speed is within the range of 5° to 90°. The irradiation voltage of the α target is 40 kV, and the current density is 100 mA.

[0067] Rietveld structure correction was performed on the samples using TOPAS, and the crystal structure and coordination composition of samples with different catalytic active sites were analyzed.

[0068] The specific surface area of ​​the sample after degassing at 150℃ was determined using a specific surface area and porosity analyzer (ASAP2460).

[0069] X-ray photoelectron spectroscopy (XPS, EscaLab 250Xi) is used to determine the chemical composition, molecular structure, valence, and other chemical information of the analyte.

[0070] The total carbon and total organic carbon contents were determined using a TOC-L analyzer (Shimadzu, Japan).

[0071] The ion concentration of the solution after the reaction was determined using an ion chromatograph (ICS3000).

[0072] Microwave reflection loss was measured using a vector network analyzer (Agilent N5230C).

[0073] Example 1

[0074] 3 mmol of Co(NO3)2·6H2O was dissolved in a mixture of 30 mL of ethylene glycol (CH2OH)2 and 10 mL of deionized water, and stirred for 40 min. Then, 30 mmol of NH4HCO3 was added, and the mixture was stirred for another 40 min to dissolve it. The solution was transferred to a polytetrafluoroethylene reactor liner and placed in a high-temperature, high-pressure hydrothermal stainless steel reactor. It was heated in an oven at 180 °C for 24 h, centrifuged with deionized water and ethanol, and then dried in an oven at 60 °C for 12 h to obtain the cobalt carbonate precursor. XRD analysis was performed on the cobalt carbonate precursor, and its XRD pattern (e.g., [image of XRD pattern]) is shown below. Figure 1 The diagram shown matches the standard card for CoCO3, indicating that the precursor is CoCO3.

[0075] The cobalt carbonate precursor was placed in a tube furnace and calcined at 350°C under an oxygen atmosphere for 2 hours to obtain cobalt oxide I, abbreviated as M. 6.6 P 3.4 , of which Co 2+ With Co 3+ The molar ratio M / P is 6.6:3.4. For cobalt oxide IM 6.6 P 3.4Perform XRD testing, and its XRD pattern (e.g.) Figure 2 The peaks at relative positions of 19.0° (111), 31.3° (220), 36.8° (311), 38.5° (222), 44.8° (400), 55.6° (422), 59.4° (511), and 65.2° (440) of the Co3O4 standard card (JCPDS:42-1467) were matched with those of other impurity peaks, indicating that a high-purity Co3O4 phase was prepared.

[0076] For M 6.6 P 3.4 XRD patterns were used to refine the Rietveld structure to determine the content of dual catalytic active sites in Co3O4. 6.6 P 3.4 The structural refinement fitting results are as follows Figure 3 As shown. From Figure 3 It can be observed that the fitted data basically matches the original data, R wp (Weighted full spectrum factor), R exp (Expectation factor) and R p The full-spectrum factors reached 4.92, 1.03, and 3.64, respectively, indicating that the M calcined in an oxygen-rich atmosphere... 6.6 P 3.4 The cubic space group was preserved. Additionally, the fitted Co... 3+ With Co 2+ The occupancy rates were 0.9490 and 0.9623, respectively, and the corresponding Co... 2+ With Co 3+ The M / P ratio is 1.97, specifically as follows: Figure 3 As shown.

[0077] Microwave Vector Network Analyzer Test M 6.6 P 3.4 Its microwave reflectivity is -7.34dB.

[0078] Example 2

[0079] Cobalt oxide II, abbreviated as M, was prepared according to the method in Example 1. 6.7 P 3.3 The only difference is that the roasting temperature is 450℃.

[0080] Cobalt oxide IIM 6.7 P 3.3 XDR testing was performed, and the spectrum is as follows: Figure 3 As shown in Table 1, the Rietveld structure was refined and fitted.

[0081] Microwave Vector Network Analyzer Test M 6.7 P 3.3Its microwave reflectivity is -10.26dB.

[0082] Example 3

[0083] Cobalt oxide III, abbreviated as M, was prepared according to the method in Example 1. 6.9 P 3.1 The only difference is that the roasting temperature is 550℃.

[0084] Cobalt oxide IIIM 6.9 P 3.1 XDR testing was performed, and the spectrum is as follows: Figure 3 As shown in Table 1, the Rietveld structure was refined and fitted.

[0085] Microwave Vector Network Analyzer Test M 6.9 P 3.1 Its microwave reflectivity is -14.21dB.

[0086] Example 4

[0087] Cobalt oxide VI, abbreviated as M, was prepared according to the method in Example 1. 7.0 P 3.0 The only difference is that the roasting temperature is 650℃.

[0088] Cobalt oxide VIM 7.0 P 3.0 XDR testing was performed, and the spectrum is as follows: Figure 3 As shown in Table 1, the Rietveld structure was refined and fitted.

[0089] Microwave Vector Network Analyzer Test M 7.0 P 3.0 Its microwave reflectivity is -16.26 dB.

[0090] Table 1:

[0091]

[0092]

[0093] This shows that the space group remains basically unchanged after the regulation of the dual-catalytic active sites, Co 3+ The occupancy rate gradually increased from 0.9490 to 0.9756, and vice versa. 2+ The occupancy rate decreased from 0.9623 to 0.8408, while the corresponding M / P ratio increased from 1.97 to 2.32. Therefore, the dual catalytic active sites of Co3O4 can be successfully modulated by heat treatment at different temperatures, i.e., microwave catalytic active sites (Co... 3+ ) and redox active sites (Co 2+ They show a negative correlation.

[0094] Example 5

[0095] 1 mmol of ferric nitrate, 1 mmol of lanthanum nitrate, and 2 mmol of anhydrous citric acid were dissolved in a 40 mL mixture of distilled water and ethanol (volume ratio 19:1). After stirring for 40 min, 3 mmol of urea was added, and stirring was continued for another 40 min. The stirred solution was transferred to a 100 mL container lined with a polytetrafluoroethylene reactor and then placed in a high-temperature, high-pressure hydrothermal stainless steel reactor. The reactor was hydrothermally heated at 140 °C for 12 h. After washing and drying, the hydrothermally heated product was calcined in a muffle furnace at 800 °C for 2 h under air atmosphere. The product was then acid-washed with 0.5 M hydrochloric acid, washed with deionized water, and dried to obtain lanthanum ferrite (LaFeO3).

[0096] The XRD pattern of lanthanum ferrite LaFeO3 is as follows: Figure 8 As shown, the obtained lanthanum ferrite LaFeO3 belongs to the orthorhombic crystal system, with cell parameters a = 5.5669, b = 7.8547, c = 5.553, and α = β = γ = 90.0°.

[0097] XPS test results of lanthanum ferrite LaFeO3 are as follows: Figure 9 , Figure 10 , Figure 11 and Figure 12 As shown, both lanthanum and iron in the obtained lanthanum ferrite LaFeO3 exist in two oxidation states: lanthanum at +3 and +4, and iron at +2 and +3. Therefore, the redox cycle can proceed more efficiently during the reaction, thereby accelerating the rate of free radical generation.

[0098] The prepared lanthanum ferrite LaFeO3 was subjected to SEM analysis, and the SEM image is shown below. Figure 13 As shown.

[0099] The microwave absorption performance of lanthanum ferrite (LaFeO3) was characterized using a vector network analyzer. The composite ratio of paraffin / lanthanum ferrite (LaFeO3) was 3:7, and the thickness of the sample (prepared as a hollow cylinder with an inner diameter of 3.04 mm and an outer diameter of 7.0 mm) was 6.5 mm. The test results showed that the reflection loss value of the lanthanum ferrite sample was as high as -20 dB, indicating good microwave absorption performance.

[0100] Example 6

[0101] M prepared in Examples 1-4 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0X-ray photoelectron spectroscopy (XPS) was performed, and the specific spectrum is as follows: Figure 4 As shown.

[0102] Figure 4 The Co2p core level spectrum of Co3O4 with different M / P values ​​shows two main peaks near 779.5 eV and 794.5 eV, which correspond to the Co2p1 / 2 and Co2p3 / 2 spin-orbit components of the Co2p peak of Co3O4, respectively.

[0103] For M with different M / P 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 The Co2p core level spectrum was fitted, and the results are shown in Table 2. For example, M... 6.6 P 3.4 There are two coexisting Co valence states, with binding energies of 779.33 and 794.46 eV, belonging to the CoO6 octahedral Co. 3+ The ion and binding energies of 780.97 and 796.15 eV, respectively, belong to the CoO4 tetrahedral Co. 2+ Ions. Furthermore, the two broad peaks near 788.5 eV and 803.5 eV represent Co ions. 2+ (2p1 / 2) and Co 2+ (2p3 / 2) satellite peak.

[0104] M obtained after different heat treatment temperatures 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 Co 3+ The peak position and peak area are gradually increasing, while Co 2+ The peak position also shifts towards higher binding energies, but the peak area gradually decreases, indicating that calcination temperature and oxygen-enriched atmosphere synergistically regulate the concentration of Co in Co3O4. 3+ With Co 2+ The content of [specific element] was determined, and the construction of two catalytic active sites was achieved.

[0105] To more clearly reveal the changes in valence state, the percentage of peak area calculated from the deconvolution spectrum was used to calculate and compare the Co content in Co3O4 treated under different conditions. 2+ / Co 3+ The atomic ratios are shown in Table 2. The results reveal that increasing the heat treatment temperature in an oxygen-rich atmosphere leads to a decrease in the Co content. 3+The content of Co increased. 2+ The decrease in the content of [a specific substance] indicates an increase in microwave catalytic active sites, while the decrease in persulfate redox catalytic active sites leads to an increase in the M / P ratio. These conclusions are consistent with the results of Rietveld structure refinement.

[0106] Table 2

[0107]

[0108] Furthermore, as the M / P ratio increases, the Co2p peak shifts towards higher binding energies, further indicating changes in the dual-catalytic active sites and the presence of oxygen vacancies. The high binding band shift of Co2p may be attributed to the band shift caused by the localized built-in electric field generated by oxygen vacancies in Co3O4 with different M / P ratios.

[0109] In the O1s core level spectrum of XPS, an asymmetric broad peak exists, indicating the presence of multiple oxygen valence state environments. The O1s core level spectrum is decomposed into two main fitting peaks, attributed to adsorbed oxygen (Oads.) at 529.7 eV and lattice oxygen (Olat.) at 531.10 eV, respectively. Adsorbed oxygen is generally considered to be adsorbed onto oxygen vacancies; therefore, the ratio of adsorbed oxygen to lattice oxygen can serve as an indicator of the relative abundance of oxygen vacancies. Table 3 shows that the regulation of dual catalytic active sites can cause changes in oxygen vacancies in the crystal. 3+ and Co 2+ The regulation of the two catalytically active sites will generate a corresponding amount of oxygen vacancies. The presence of oxygen vacancies can create an internal electric field within the crystal, which in turn greatly promotes ion diffusion and charge transfer rates, thus enhancing reaction kinetics.

[0110] Table 3

[0111]

[0112] Example 7

[0113] For the cobalt carbonate precursors prepared in Examples 1-4, M 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 Scanning electron microscopy (SEM) tests were performed, specifically as follows: Figure 5 (b) Figure 5 (c) Figure 5 (d) Figure 5 (e) Figure 5 As shown in (f).

[0114] As the temperature rises, the bulk carbonate particles of the cobalt carbonate precursor are decomposed, and then gradually further decomposed into nanoscale spherical particles. Finally, the nanoscale spherical particles aggregate into larger spherical particles. Throughout the entire morphological change process, the size of the spherical particles remains between 5 and 8 μm.

[0115] Example 8

[0116] M prepared in Examples 1-4 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 Perform physical adsorption tests (ASAP2460).

[0117] Measured: M 6.6 P 3.4 Specific surface area is 104.80 cm². 2 / g, with an average pore size of 6.54nm; M 6.7 P 3.3 Specific surface area is 41.87 cm² 2 / g, with an average pore size of 20.62nm; M 6.9 P 3.1 Specific surface area is 16.33 cm² 2 / g, with an average pore size of 53.45nm; M 7.0 P 3.0 Specific surface area is 7.56 cm² 2 / g, with an average pore size of 119.90nm.

[0118] The specific surface area of ​​the catalyst gradually decreases while the pore size gradually increases with increasing temperature.

[0119] Example 9

[0120] The M prepared in Examples 1-4 were respectively 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 The catalyst was added to a solution containing sodium persulfate and ciprofloxacin (CIP) and microwaved at 800 W. The catalyst dosage was 1.0 g / L. -1 The sodium persulfate concentration is 0.2 mM·L. -1 The initial concentration of CIP was 2.5 mg·L⁻¹. -1 The pH value is approximately 7.0.

[0121] Joining M 6.6 P 3.4 M 6.7 P 3.3 M 6.9 P 3.1 M 7.0 P 3.0 After 5 minutes of treatment, the CIP removal rates were 40%, 75%, 81%, and 72%, respectively; after 10 minutes of treatment, the CIP removal rates were 46%, 79%, 83%, and 80%, respectively.

[0122] Example 10

[0123] Following the method in Example 9, the M prepared in Example 3 was... 6.9 P 3.1 Add to a solution containing 0.4 mM·L -1 Sodium persulfate and 2.5 mg·L -1 The only difference in the ciprofloxacin (CIP) solution is that the pH values ​​are adjusted to approximately 3.0, 5.0, 7.0, 9.0, and 11.0, respectively.

[0124] After 5 minutes of treatment, the CIP removal rates were 78%, 83%, 92%, 63%, and 66%, respectively; after 10 minutes of treatment, the CIP removal rates were 80%, 85%, 93%, 73%, and 71%, respectively.

[0125] As the pH increased from 3 to 11, the degradation efficiency of CIP first increased from 80% to 93% and then decreased to 81%, while the reaction rate also decreased from 0.4083 g·mL⁻¹. -1 ·min -1 Increased to 1.3865 g·mL -1 ·min -1 Reduce to 0.2410 g·mL -1 ·min -1 This is because, under acidic conditions, hydrogen ions readily react with ·OH and SO4 produced during the degradation process. ·- The reaction reduces the number of active species in the solution, thus decreasing the degradation efficiency of CIP; under alkaline conditions, SO4 ·- It will turn into SO4 2- When combined with less reactive ·OH groups, the degradation efficiency of CIP will also become slower.

[0126] Example 11

[0127] Ciprofloxacin (CIP) was degraded according to the method in Example 10, with the only differences being that the pH value was approximately 7 and the amount of catalyst added was 0 g·L⁻¹. -1 0.2 g·L -1 0.25 g·L -1 1.0 g·L-1 .

[0128] After 5 minutes of treatment, the CIP removal rates were 76%, 83%, 87%, and 92%, respectively; after 10 minutes of treatment, the CIP removal rates were 81%, 87%, 90%, and 93%, respectively.

[0129] Example 12

[0130] Ciprofloxacin (CIP) was degraded according to the method in Example 10, with the only differences being: the pH value was approximately 7, and the concentrations of sodium persulfate were 0.1, 0.2, 0.3, and 0.5 mM·L, respectively. -1 .

[0131] After 5 minutes of treatment, the CIP removal rates were 25%, 62%, 82%, and 92%, respectively; after 10 minutes of treatment, the CIP removal rates were 32%, 67%, 85%, and 93%, respectively.

[0132] Example 13

[0133] Ciprofloxacin (CIP) was degraded according to the method in Example 10, with the only differences being: the pH value was approximately 7, and the initial concentrations of ciprofloxacin were 0.25, 1.0, and 2.5 mg·L⁻¹. -1 .

[0134] After 5 minutes of treatment, the CIP removal rates were 94%, 77%, and 11%, respectively; after 10 minutes of treatment, the CIP removal rates were 94%, 80%, and 12%, respectively.

[0135] Example 14

[0136] Ciprofloxacin (CIP) was degraded according to the method in Example 10, with the only difference being that the pH value was approximately 7 and the microwave power was 200, 350, 500, and 650 MW, respectively.

[0137] After 5 minutes of treatment, the CIP removal rates were 28%, 67%, 87%, and 90%, respectively; after 10 minutes of treatment, the CIP removal rates were 51%, 91%, 92%, and 92%, respectively.

[0138] Example 15

[0139] Ciprofloxacin (CIP) was degraded according to the method in Example 10, the only difference being that the pH value was 7 and M was recycled. 6.9 P 3.1 Five times, each treatment lasting 10 minutes.

[0140] The degradation rates of CIP were 93%, 85%, 83%, 81%, and 81%, respectively.

[0141] M after being used five times 6.9 P 3.1 XRD analysis and Rietveld structure refinement revealed no significant changes in its space group, atomic occupancy, or content, indicating that the catalyst maintained the integrity of its crystal structure throughout the degradation process. Therefore, it can be concluded that M... 6.9 P 3.1 It exhibits stable catalytic activity and excellent reusability.

[0142] Example 16

[0143] 20 mg, 50 mg, and 50 mg of lanthanum ferrite LaFeO3 prepared in Example 5 were added to 50 mL of solutions with concentrations of 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B, respectively. Then, 5 mL of 2 mM / L sodium persulfate solution was added, and catalytic oxidation degradation was carried out under microwave power of 800 W. The degradation results are shown in Table 4.

[0144] Table 4

[0145]

[0146] Testing SO4 in solutions before and after degradation 2- F - The specific results are shown in Table 5.

[0147] Table 5

[0148]

[0149] Example 17

[0150] The lanthanum ferrite LaFeO3 prepared in Example 5 was added to a 10 mg / L levofloxacin solution. The lanthanum ferrite LaFeO3 was recycled for degradation three times, each time for 10 minutes. The degradation rate was 92% in the first iteration, 83% in the second, and 75% in the third.

[0151] Comparative Example

[0152] Comparative Example 1

[0153] Ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7 and M was not added. 6.9 P 3.1 .

[0154] After 5 minutes of treatment, the CIP removal rate was 78%; after 10 minutes of treatment, the CIP removal rate was 80%.

[0155] Comparative Example 2

[0156] Ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7 and sodium persulfate was not added.

[0157] After 5 minutes of treatment, the CIP removal rate was 30%; after 10 minutes of treatment, the CIP removal rate was 35%.

[0158] Comparative Example 3

[0159] Ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7 and the process was not carried out under microwave conditions.

[0160] After 5 minutes of treatment, the CIP removal rate was 35%; after 10 minutes of treatment, the CIP removal rate was 36%.

[0161] Comparative Example 4

[0162] Ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7, the process was not carried out under microwave conditions, and M was not added. 6.9 P 3.1 .

[0163] After 5 minutes of treatment, the CIP removal rate was 5%; after 10 minutes of treatment, the CIP removal rate was 6%.

[0164] Comparative Example 5

[0165] The ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7, the process was not carried out under microwave conditions, and sodium persulfate was not added.

[0166] After 5 minutes of treatment, the CIP removal rate was 7%; after 10 minutes of treatment, the CIP removal rate was 7%.

[0167] Comparative Example 6

[0168] Ciprofloxacin (CIP) was degraded according to the method in Example 10, except that the pH value was approximately 7 and sodium persulfate and M were not added. 6.9 P 3.1 .

[0169] After 5 minutes of treatment, the CIP removal rate was 0%; after 10 minutes of treatment, the CIP removal rate was 0%.

[0170] Comparative Example 7

[0171] 5 mL of 2 mM / L sodium persulfate solution was added to 50 mL of solutions containing 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B, respectively, and the solutions were allowed to degrade for 10 min. After degradation, the concentrations of levofloxacin, tetracycline hydrochloride, and rhodamine B were 9.2 mg / L, 84 mg / L, and 6.6 mg / L, respectively.

[0172] Comparative Example 8

[0173] 50 mL of solutions containing 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B were placed in a microwave oven at 800 W for 10 min to degrade the compounds. After degradation, the concentrations of levofloxacin, tetracycline hydrochloride, and rhodamine B were 10 mg / L, 68 mg / L, and 10 mg / L, respectively.

[0174] Comparative Example 9

[0175] 5 mL of 2 mM / L sodium persulfate solution was added to 50 mL of solutions containing 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B, respectively. The solutions were then placed under microwave conditions at 800 W for 10 min to degrade the compounds. After degradation, the concentrations of levofloxacin, tetracycline hydrochloride, and rhodamine B were 2.6 mg / L, 49 mg / L, and 2.5 mg / L, respectively.

[0176] Comparative Example 10

[0177] 5 mL of 2 mM / L sodium persulfate solution was added to 50 mL of solutions containing 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B, respectively. Then, 20 mg, 50 mg, and 50 mg of lanthanum ferrite (LaFeO3) prepared in Example 5 were added, respectively, and the solutions were allowed to degrade for 10 min. After degradation, the concentrations of levofloxacin, tetracycline hydrochloride, and rhodamine B were 7.2 mg / L, 32 mg / L, and 6 mg / L, respectively.

[0178] Comparative Example 11

[0179] The lanthanum ferrite LaFeO3 prepared in Example 5 was added to 50 mL of solutions containing 10 mg / L levofloxacin, 100 mg / L tetracycline hydrochloride, and 10 mg / L rhodamine B, with added amounts of 20 mg, 50 mg, and 50 mg, respectively. The solution was then placed under microwave conditions at 800 W for 10 min for degradation. After degradation, the concentrations of levofloxacin, tetracycline hydrochloride, and rhodamine B were 6.7 mg / L, 30 mg / L, and 10 mg / L, respectively.

[0180] Experimental Example

[0181] Experimental Example 1

[0182] Comparative Example 1 (MW+PS) and Comparative Example 2 (MW+M) 6.9 P 3.1 ) and in Example 9, M 6.9 P 3.1 For catalyst (MW+PS+M) 6.9 P 3.1 The change in total organic carbon (TOC) content over time during the treatment of CIP wastewater is shown in the test results. Figure 6 As shown.

[0183] In Comparative Example 1 (MW+PS), the total organic carbon content exceeded that in the original solution at 2 min, and then gradually decreased with increasing time; in Comparative Example 2 (MW+M 6.9 P 3.1 The total organic carbon content in Example 9 (MW+PS+M) showed only a slight change after 5 minutes; while in Example 9 (MW+PS+M)... 6.9 P 3.1 The total organic carbon content in the sample decreased over time, indicating that it effectively mineralized ciprofloxacin.

[0184] Experiment Example 2

[0185] Comparative Example 1 (MW+PS) and Comparative Example 2 (MW+M) 6.9 P 3.1 ) and in Example 9, M 6.9 P 3.1 For catalyst (MW+PS+M) 6.9 P 3.1 After treating CIP wastewater for 10 minutes, the NH4+ in the solution... + NO3 - F - SO4 2- The value, the test results are as follows Figure 7 As shown.

[0186] The ion concentrations in the solution after degradation and the leaching concentrations of cobalt ions after cyclic degradation were 0.695, 0.576, 0.438, 0.411, and 0.403 mg·L, respectively. -1 All of these indicate that M has two catalytic active sites. 6.9 P 3.1 The catalyst exhibits excellent structural stability throughout the degradation system and can achieve the mineralization of ciprofloxacin without secondary pollution from ion leaching. It is a high-performance catalyst for microwave-activated persulfate degradation of antibiotics.

[0187] The present invention has been described in detail above with reference to specific embodiments and / or exemplary examples, as well as the accompanying drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for catalytic microwave activation of persulfate to degrade organic wastewater, wherein a transition metal compound is used as a catalyst to catalytically activate persulfate under microwave irradiation, thereby catalytically oxidizing organic pollutants in the wastewater. The organic pollutant is one or more of quinolone antibiotics, tetracycline antibiotics, and dye-based organic compounds. The catalyst is a cobalt oxide. In the cobalt oxide, the molar ratio of divalent cobalt to trivalent cobalt is (6.4-7.2):(2.8-3.6). The preparation method of the catalyst specifically includes the following steps: Step 1: Dissolve the transition metal salt in a solvent, add a precipitant, and obtain a reaction solution; Step 2: The reaction solution undergoes a hydrothermal reaction under closed high-temperature conditions, followed by separation, washing, and drying to obtain the catalyst precursor; Step 3: Calcining the catalyst precursor to obtain the catalyst; The persulfate is one or more of ammonium persulfate, metal perdisulfate, and metal permonsulfate. The molar ratio of the organic pollutant to persulfate is (0.4-3.5) g:(0.05-0.6) mol; The molar ratio of the catalyst to persulfate is (2-55):1; The microwave power is 350-850W; The pH value of the organic wastewater is 6-8.

2. The method according to claim 1, characterized in that, The persulfate is potassium persulfate and / or sodium persulfate.

3. The method according to claim 1, characterized in that, The organic pollutant is one or more of ciprofloxacin, levofloxacin, tetracycline hydrochloride, and rhodamine B.

4. The method according to claim 1, characterized in that, In the cobalt oxide, the molar ratio of divalent cobalt to trivalent cobalt is (6.6-7.0):(3.0-3.4).

5. The method according to claim 4, characterized in that, In the cobalt oxide, the molar ratio of divalent cobalt to trivalent cobalt is (6.85-6.95):(3.05-3.15).

6. The method according to claim 1, characterized in that, The molar ratio of the organic pollutant to persulfate is (0.5-2.5) g:(0.1-0.4) mol; The molar ratio of the catalyst to persulfate is (5-45):

1.

7. The method according to claim 6, characterized in that, The molar ratio of the catalyst to persulfate is (5-25):1 or (30-45):

1.

8. The method according to claim 1, characterized in that, The microwave power is 500-800W; The pH value of the organic wastewater is 6.5-7.5.

Images