Nitrogen-doped carbon nanotube-coated cobalt catalyst, and method for activating peroxyacetic acid to degrade antiviral drugs

Abstract

The present application relates to catalyst and wastewater treatment technology, specifically relates to a catalyst of nitrogen-doped carbon nanotube coated cobalt, and a method for degrading antiviral drugs by activating peroxyacetic acid.The preparation method of the catalyst is as follows: a polyamide acid solution is uniformly mixed with a carbon nanotube dispersion solution, heated to reflux reaction, the solid after reaction is collected, the solid is dispersed in a cobalt salt solution, heated to 70-90 DEG C for stirring, so that cobalt is introduced into the solid, and the solid with introduced cobalt is pyrolyzed under inert atmosphere conditions, and the catalyst is obtained.The catalyst of nitrogen-doped carbon nanotube coated cobalt provided by the present application can not only efficiently degrade ACV, but also effectively degrade lamivudine, ganciclovir and favipiravir and other antiviral drugs.

Description

TECHNICAL FIELD

[0001] The present application relates to catalysts and wastewater treatment technology, in particular to a nitrogen-doped carbon nanotube coated cobalt catalyst and a method for degrading antiviral drugs by activating peracetic acid. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] In recent years, due to the frequent occurrence of epidemic diseases, antiviral drugs are widely used to treat various diseases in humans. Among them, acyclovir (ACV) as a synthetic guanine drug has good therapeutic effect on treating herpes simplex virus and varicella-zoster virus. However, the oral bioavailability of ACV is very low, only 10-20%, and most of the ACV cannot be completely metabolized in the patient's body, and its metabolites can be excreted out of the body with the excreta. With the continuous accumulation of ACV in the environment, it may cause serious harm to human health, aquatic organisms and the like. Therefore, it is urgent to develop new treatment means to deeply remove antiviral drugs including ACV in the environment.

[0004] As a substitute for chlorine-containing disinfectants, peracetic acid (PAA) has small disinfection by-product toxicity and small ecotoxicological effect. PAA can be activated by UV radiation, heat activation, transition metal activation, etc., which can produce strong oxidizing free radicals such as ·OH and R-O· (R-O·: CH3C(O)O·, CH3C(O)OO·) to degrade organic pollutants. The operation condition of transition metal activation is mild and does not need additional energy input. Compared with other transition metals, Co has much higher efficiency in activating PAA. However, the use of transition metal ions for activation inevitably causes secondary pollution of heavy metal ions in water bodies when Co ion is used for homogeneous catalysis of PAA. The use of solid Co or Co will lead to uneven dispersion in water, affecting the catalytic activation efficiency of PAA, and thus making the degradation effect of organic matter unsatisfactory. SUMMARY

[0005] In order to solve the problems of the prior art, the purpose of the present application is to provide a nitrogen-doped carbon nanotube coated cobalt catalyst and a method for degrading antiviral drugs by activating peracetic acid. The nitrogen-doped carbon nanotube coated cobalt catalyst provided by the present application can not only efficiently degrade ACV, but also effectively degrade antiviral drugs such as lamivudine, ganciclovir and favipiravir.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0007] In one aspect, a catalyst of nitrogen-doped carbon nanotube coated cobalt is prepared by mixing a polyamide acid solution and a carbon nanotube dispersion solution, heating and refluxing, collecting the solid after reaction, dispersing the solid in a cobalt salt solution, heating to 70-90 DEG C and stirring, introducing cobalt into the solid, and pyrolyzing the cobalt-introduced solid under an inert atmosphere.

[0008] The addition ratio of the carbon nanotube, the polyamide acid and the cobalt salt is 50:85-95:1.5-4.5, mg:mg:mmol.

[0009] The present application utilizes the guidance of CNTs to make the polyamide acid condensation reaction on the surface of CNTs to form uniformly ordered polyimide nanosheets. After further loading of Co salt and pyrolysis at high temperature, the Co salt is converted into cobalt nanoparticles CoNPs, and the polyimide nanosheet is converted into a nitrogen-containing carbon layer, which coats the Co NPs on the CNTs to form Co@N-CNTs modified by cobalt.

[0010] In another aspect, a method for degrading an antiviral drug by activating peracetic acid is provided, which comprises adding peracetic acid and the catalyst of nitrogen-doped carbon nanotube coated cobalt to a solution containing the antiviral drug and mixing.

[0011] The antiviral drug is one or more of acyclovir, lamivudine, ganciclovir and favipiravir.

[0012] In a third aspect, the method for degrading an antiviral drug by activating peracetic acid is applied to treating wastewater containing the antiviral drug.

[0013] The present application has the following advantages:

[0014] The polyamide acid is used for N-doping of the carbon nanotube, pyridine N, pyrrole N and graphite N can be formed, the pyridine N and pyrrole N with redox property help the oxidation-reduction reaction to proceed and the electron transfer of the catalyst, the graphite N can promote the electron transfer of adjacent carbon atoms, increase the charge density of adjacent carbon and improve the catalytic capacity of the catalyst to PAA. The N-doping and cobalt-doping are simultaneously performed, the N1s XPS spectrum peak is offset to high bond energy, the advantages of the micro-morphology and large specific surface area of the carbon nanotube are cooperated, and the cobalt-doping exists in the form of zero-valent cobalt nanoparticles and a small amount of cobalt oxide, which is beneficial to further improve the catalytic capacity of the catalyst to PAA. The results of the catalyst provided by the present application for activating PAA to degrade ACV show that the catalyst provided by the present application can effectively activate PAA to degrade ACV, and the degradation efficiency of ACV can reach 98.25%. In addition, the catalyst provided by the present application can also effectively degrade lamivudine, ganciclovir and favipiravir, and the degradation efficiencies are 100%, 94.82% and 88.95% respectively, which can reduce the treatment cost of various antiviral drug pollution wastewater. BRIEF DESCRIPTION OF DRAWINGS

[0015] The drawings accompanying the specification of this application form a part thereof, serve to provide further understanding of the application, and together with the description of the exemplary embodiments of the application, explain the application, and do not limit the application.

[0016] Figure 1 The structure characterization diagram of the nitrogen-doped carbon nanotube coated cobalt catalyst prepared in the embodiments of the present application; (a) is the XRD diagram of N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3; (b) is the N2 adsorption-desorption isotherm and pore size distribution (embedded); (c) is the N1s high-resolution XPS spectrum; (d) is the Co 2p high-resolution XPS spectrum of Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3.

[0017] Figure 2 The morphology diagram of the catalyst of Co@N-CNTs-2 prepared in the embodiments of the present application; (a) is the HRTEM image at low magnification; (b) is the HRTEM image at medium magnification; (c) is the HRTEM image at high magnification; (d) is the element mapping diagram of C, N, O and Co in Co@N-CNTs-2.

[0018] Figure 3 The catalyst activation PAA degradation performance evaluation result diagram of ACV prepared in the embodiments of the present application; (a) is the degradation experiment of ACV by different catalyst systems; (b) is the adsorption experiment of ACV by N-CNTs and Co@N-CNTs; (c) is the degradation experiment of ACV by Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3. 2+Degradation of ACV by Co@N-CNTs-2 / PAA, Co@N-CNTs-2 / PAA against ACV; (d) is the degradation of other antiviral drugs by Co@N-CNTs-2 / PAA system; conditions: (a): [ACV]=10mg / L, [PAA]=0.25mM, [H2O2]=0.27mM, [Cat]=0.05g / L, pH0=7.0; (b): [ACV]=10mg / L, [Cat]=0.05g / L, pH0=7.0; (c): [ACV]=10mg / L, [PAA]=0.25mM, [Co 2+ ] = 0.25mg / L, [Cat]=0.05g / L, pH0=7.0; (d) [pollutants]=10mg / L, [PAA]=0.25mM, [Cat]=0.05g / L, pH0=7.0.

[0019] Figure 4 In the examples of the present application, the influence of TBA (a), p-CBA (b) on the degradation of ACV by Co@N-CNTs-2 / PAA system; the influence of TBA on the degradation of p-CBA by Co@N-CNTs-2 / PAA system (c); the influence of MeOH on the degradation of ACV by Co@N-CNTs-2 / PAA system (d); the degradation of ACV by Co@N-CNTs-2 / PAA system under different atmosphere conditions (e); the influence of 2,4-HD on the degradation of ACV by Co@N-CNTs-2 / PAA system (f). Conditions: [ACV]=10mg / L, [PAA]=0.25mM, [Cat]=0.05g / L, pH0=7.0 (except (c)); (c): [p-CBA]=20μM, [PAA]=0.25mM, [Cat]=0.05g / L, pH0=7.0

[0020] Figure 5 In the examples of the present application, the influence of TEMP- 1 O2(a); DMPO on · OH(b), R-O · (c) EPR spectrum of captured; conditions: [PAA]=0.25mM, [Cat]=0.05g / L, pH0=7.0, [DMPO]= [TEMP]=0.1M.

[0021] Figure 6 In the examples of the present application, the influence of PAA concentration (a), catalyst dosage (b), and initial pH of solution (c) on the degradation of ACV by Co@N-CNTs-2 / PAA; Zeta potential and isoelectric point pH of Co@N-CNTs-2 under different pH conditions IEP(d); Conditions: (a): [PAA]=0.05mM-0.5mM, [Cat]=0.05g / L, [ACV]=10mg / L, pH0=7.0; (b): [Cat]=0.01g / L-0.1g / L , [PAA]=0.25mM, [ACV]=10mg / L, pH0=7.0; (c): [PAA]=0.25mM, [ACV]=10mg / L, [Cat]=0.05g / L, pH0=3.0-11.

[0022] Figure 7 HCO3 in the embodiments of the present invention - (a) CO3 2- (b) Cl - (c) Effect of HA(d) on the degradation of ACV in the Co@N-CNTs-2 / PAA system; conditions: [PAA] = 0.25 mM, [ACV] = 10 mg / L, [Cat] = 0.05 g / L, pH 0 = 7.0.

[0023] Figure 8 The experiment (a) shows the cyclic use of Co@N-CNTs-2 in this embodiment of the invention; and the high-resolution XPS characteristic peak spectra of Co2p before and after use of Co@N-CNTs-2 (b).

[0024] Figure 9 This describes a possible degradation pathway for ACV degradation by the Co@N-CNTs-2 / PAA system in the embodiments of the present invention.

[0025] Figure 10 The acute toxicity (a) and chronic toxicity (b) of ACV and its degradation intermediates in the embodiments of the present invention are shown; from dark to light, they represent highly toxic, toxic, harmful and harmless, respectively. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] In order to remove the antiviral drugs including ACV in the environment efficiently, the application provides a catalyst of nitrogen-doped carbon nanotube coated with cobalt and a method for degrading antiviral drugs by activating peroxiacetic acid.

[0029] In an exemplary embodiment of the application, a catalyst of nitrogen-doped carbon nanotube coated with cobalt is provided, and the preparation method comprises the following steps: uniformly mixing a polyamic acid solution and a carbon nanotube dispersion solution, heating and refluxing, collecting the solid after reaction, dispersing the solid in a cobalt salt solution, heating to 70-90 DEG C for stirring, introducing cobalt into the solid, and pyrolyzing the solid with introduced cobalt under an inert atmosphere.

[0030] In the application, the addition ratio of carbon nanotube, polyamic acid and cobalt salt is 50:85-95:1.5-4.5, mg:mg:mmol.

[0031] In some embodiments, the addition ratio of carbon nanotube and cobalt salt is 50:2.8-3.2, mg:mmol. The catalyst prepared under this condition has better efficiency in degrading antiviral drugs (especially ACV) by activating PAA.

[0032] In some embodiments, the heating and refluxing temperature is 145-155 DEG C.

[0033] In some embodiments, the heating temperature for stirring is 70-90 DEG C for 10-14 h.

[0034] In some embodiments, after introducing cobalt into the solid, the solid-liquid separation is followed by washing with DMF, anhydrous ethanol and ultrapure water, and then drying.

[0035] In some embodiments, the pyrolysis temperature is 550-650 DEG C.

[0036] In some embodiments, the pyrolysis time is 1.5-2.5 h.

[0037] In some embodiments, the preparation method of the polyamic acid solution comprises adding ethylenediamine and pyromellitic dianhydride into a solution for stirring. The stirring temperature is room temperature, and the room temperature in the application refers to the temperature of indoor environment, which is generally 15-30 DEG C.

[0038] In another embodiment of the application, a method for degrading antiviral drugs by activating peroxiacetic acid is provided, which comprises adding peroxiacetic acid and the above catalyst of nitrogen-doped carbon nanotube coated with cobalt to a solution containing antiviral drugs, and mixing.

[0039] The antiviral drugs are one or more of acyclovir, lamivudine, ganciclovir and favipiravir.

[0040] In some embodiments, the concentration of peroxoacetic acid in the mixed solution is 0.05-0.5 mmol / L, preferably 0.20-0.5 mmol / L, and more preferably 0.20-0.30 mmol / L.

[0041] In some embodiments, the amount of the catalyst coated with the nitrogen-doped carbon nanotube and cobalt added is 0.01-0.1 g / L, preferably 0.05-0.1 g / L, and more preferably 0.05-0.06 g / L.

[0042] In some embodiments, the temperature of the mixed solution is 24-26℃.

[0043] In some embodiments, peroxoacetic acid is added to the solution containing the antiviral drug, and the pH is adjusted to 6.8-7.2. Under this condition, PAA can better activate the degradation of the antiviral drug.

[0044] In a third embodiment of the present application, the application provides a use of the above-mentioned method for activating peroxoacetic acid to degrade antiviral drugs in treating wastewater containing antiviral drugs.

[0045] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0046] Embodiments

[0047] Reagents:

[0048] Acyclovir (ACV), cobalt nitrate hexahydrate (Co(NO3)2·6H2O), multi-walled carbon nanotubes (CNTs), 2,4-hexadienoic acid (2,4-HD), and humic acid (HA) were purchased from Aladdin Reagent Co., Ltd. Lamivudine, ganciclovir, and p-chlorobenzoic acid (p-CBA) were purchased from Bide Pharmaceutical. Tert-butyl alcohol (TBA), p-benzoquinone (p-BQ), methanol (MeOH), ethylenediamine (EDA), pyromellitic dianhydride (PMDA), N,N-dimethylformamide (DMF), furfuryl alcohol (FFA), sulfuric acid (H2SO4), sodium hydroxide, hydrogen peroxide (30% w / w), sodium carbonate, sodium chloride, sodium bicarbonate, and glacial acetic acid were purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd. Favipiravir was purchased from McKinley Chemical Reagent Co., Ltd.

[0049] Preparation of N-CNTs and Co@N-CNTs:

[0050] EDA (0.642 mL) and PMDA (2.121 g) were dissolved in 60 mL of DMF solution, and the solution was placed at room temperature and continuously stirred for 6 hours until the solution was transparent to obtain a polyamic acid solution.

[0051] CNTs (50 mg) were dispersed in DMF (200 mL) for about 10 min. Then the prepared polyamide acid solution (44.98 mg mL-1, 2 mL) was added and stirred for about 5 min. The reaction was refluxed in an oil bath at 150 °C in a three-necked round-bottom flask (500 mL) and stirred for 1 h. After cooling to room temperature, the product was washed with DMF, anhydrous ethanol, and ultrapure water three times, respectively, and dried at 60 °C overnight. The product was collected. -1 )2mL, stirred for about 5 min. The reaction was refluxed in an oil bath at 150 °C in a three-necked round-bottom flask (500 mL) and stirred for 1 h. After cooling to room temperature, the product was washed with DMF, anhydrous ethanol, and ultrapure water three times, respectively, and dried at 60 °C overnight. The product was collected.

[0052] The dried solid was dispersed in DMF (150 mL) containing Co(NO3)2·6H2O (0 g, 0.437 g, 0.873 g, and 1.31 g) by ultrasonication, stirred at 80 °C in an oil bath for 12 h, cooled to room temperature, and washed with DMF, anhydrous ethanol, and ultrapure water three times, respectively, and dried at 60 °C overnight. Finally, the samples were pyrolyzed at 600 °C for 2 h in an argon atmosphere, washed with water twice after cooling and collection, and dried to obtain four kinds of N-doped carbon nanotube-coated cobalt catalysts, which were named N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2, and Co@N-CNTs-3, respectively, according to the different cobalt contents.

[0053] Preparation of PAA:

[0054] Hydrogen peroxide (30%, w / w) and glacial acetic acid were mixed in a volume ratio of 3:2, and 0.3 mol / L H2SO4 was added to catalyze the reaction. The mixture was placed in a 40 °C water bath for 24 h, immediately placed in a refrigerator after cooling to room temperature, and stored at 4 °C. The reaction equation is shown in formula (1).

[0055]

[0056] The concentration of the prepared PAA was determined by the national standard method (GB / T 19104-2021). After analysis and determination, the concentration of the prepared PAA was 1.64 mol / L.

[0057] Degradation experiment:

[0058] First, 3.81 μL of PAA was added to a beaker containing 25 mL of ACV solution (10 mg / L), and the initial pH of the reaction system was adjusted using NaOH solution or H2SO4 solution. Then, 1.25 mg of catalyst was added, ultrasonically dispersed, and immediately timed. The reaction temperature was maintained at 25 ± 1 °C. At certain time intervals, 1.0 mL of the reaction solution was mixed with 0.3 mL of methanol to quench the reaction. The catalyst was removed by filtration through a 0.22 μm polytetrafluoroethylene membrane. The residual concentration of ACV was detected by high-performance liquid chromatography.

[0059] Results and discussion:

[0060] 1. Structure and morphology study:

[0061] The phase composition of the four catalysts was investigated by XRD, as shown in Figure 1 (a). N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 all appeared diffraction peaks at 23.1° and 43.9°, corresponding to the (002) and (100) crystal planes of carbon. This indicated that graphite frameworks were formed in N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 by high-temperature pyrolysis. In addition, Co@N-CNTs-2 had a weak peak of CoO at 36.6°, indicating that the surface of Co@N-CNTs-2 was slightly oxidized. The specific surface area and pore size distribution of N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 were investigated by N2adsorption-desorption isotherms. As shown in Figure 1 (b), the Brunauer-Emmett-Teller (BET) surface area (S BET ) of N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 were 172.44 m 2 / g, 196.43 m 2 / g, 203.84 m 2 / g and 209.99 m 2 / g, respectively. By observing the four isotherms, they were in line with typical type II isotherms, which was consistent with the pore size distribution (see the inset of 1(b)).

[0062] The surface state and chemical composition of N-CNTs, Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 were further investigated by XPS. The XPS spectra of N 1s were as shown in Figure 1(c) shows that the N 1s high-resolution peak of N-CNTs can be deconvoluted into pyridine N (398.40 eV), pyrrolic N (399.56 eV) and graphitic N (400.81 eV). The binding energies of pyridine N, pyrrolic N and graphitic N of Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 are 398.56 eV, 399.85 eV and 401.07 eV, respectively. This indicates that the doping of cobalt causes the N 1s XPS spectrum peak to shift to high bond energy. With the addition of cobalt content, the content of the three nitrogen species changes, in which pyridine N and pyrrolic N account for 68.54% of the nitrogen species in Co@N-CNTs-2. Pyridine N and pyrrolic N with redox properties help the progress of redox reaction and the electron transfer of Co@N-CNTs-2. Graphitic N can promote the electron transfer of adjacent carbon atoms, increase the charge density of adjacent carbon, and improve the catalytic ability of Co@N-CNTs-2 to PAA.

[0063] As shown in Figure 1 (d), the Co 2p high-resolution peak in Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 is respectively attributed to Co 0 (780.55 eV), Co 2+ (783.99 eV) and satellite peak (788.14 eV). In Co@N-CNTs-2, Co 0 accounts for 77.90% of Co species, Co 2+ has a relative percentage content of 22.10%, indicating that in Co@N-CNTs-2, the cobalt species mainly exists in the form of Co NPs.

[0064] The morphology of Co@N-CNTs was studied by high-resolution transmission electron microscopy (HRTEM), as shown in Figure 2 (a) and (b), after high-temperature pyrolysis, the nitrogen-containing carbon layer wraps CNTs inside, and cobalt ions are converted into cobalt nanoparticles encapsulated in the carbon layer, which will avoid excessive loss of cobalt during the reaction. After high-temperature pyrolysis, Figure 2 (c), the carbon layer and the lattice fringes of cobalt can be clearly seen. The lattice fringe spacing of cobalt is 0.191 nm and 0.216 nm, respectively, corresponding to the (101), (100) crystal planes of cobalt. Figure 2 (d) shows the element mapping of Co@N-CNTs-2, which clearly shows the distribution of C, N, O and Co elements, indicating that Co is successfully embedded. Part of the O element gathers at the location of the Co element, forming CoO particles, which is consistent with the XRD result analysis.

[0065] 2, evaluation of the degradation performance of the activated PAA catalyst on ACV:

[0066] The degradation performance of N-CNTs / PAA, Co@N-CNTs / PAA systems on ACV was evaluated with ACV as a pollution model. As shown in Figure 3 (a), only 1.94% of ACV was degraded in the presence of PAA alone. When N-CNTs activated PAA, only 4.02% of ACV was degraded. When Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 cooperated with PAA respectively, the degradation efficiency of ACV within 10 minutes was 85.08%, 98.25% and 66.13% respectively. This means that Co@N-CNTs containing cobalt elements has stronger catalytic ability on PAA compared with N-CNTs without cobalt, and the doping of cobalt elements improves the catalytic performance of nitrogen-doped carbon materials. However, the degradation effect of Co@N-CNTs-2 / PAA system is significantly higher than that of Co@N-CNTs-3 / PAA system, indicating that the amount of cobalt in Co@N-CNTs-2 reaches the optimal ratio. Since the PAA solution inevitably contains H2O2, 0.25 mM PAA corresponds to 0.27 mM H2O2, in order to exclude the influence of H2O2 on degradation, the degradation experiment of Co@N-CNTs-2 / H2O2 system on ACV was carried out under the same conditions, as shown in Figure 3 (a), only 3.02% of ACV was degraded, so the effect of H2O2 can be ignored. When Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 exist alone, the removal rate of ACV does not exceed 3.89%, indicating that the adsorption effect of Co@N-CNTs-1, Co@N-CNTs-2 and Co@N-CNTs-3 on ACV can be ignored (3(b)), and the removal of ACV by Co@N-CNTs / PAA system mainly comes from degradation.

[0067] At the same time, a small amount of cobalt ions (0.25 mg / L) was released during the degradation process. Co 2+ The contribution of activated PAA to the degradation of ACV is 57.73% ( Figure 3 (c)). Since the leaching amount of Co 2+ increases continuously with the reaction, the removal of ACV mainly comes from Co@N-CNTs-2 / PAA system.

[0068] As shown in Figure 3 (d), Co@N-CNTs-2 / PAA system can also effectively degrade lamivudine, ganciclovir and favipiravir, with degradation efficiency of 100%, 94.82% and 88.95% respectively. This shows that Co@N-CNTs-2 / PAA system has wide applicability in treating water bodies contaminated with antiviral drugs.

[0069] 3. Identification of active species:

[0070] To determine the active species present in the system, quenching experiments were conducted using several different free radical scavengers. Tert-butanol (TBA) is a typical ·OH scavenger, with a reaction rate of k = (3.8-7.6) × 10⁻⁶ with ·OH. 8 M -1 s -1 .like Figure 4 As shown in (a), when 5 mM TBA was added to the system, the removal rate of ACV was 92.38%. When the amount of TBA was further increased to 25 mM, the removal rate of ACV was 96.45%. Compared with the system without added TBA, TBA had little inhibitory effect on the degradation of ACV. · OH contributes negligibly to the degradation of ACV. p-Chlorobenzoic acid (p-CBA) can act as a quencher for ·OH and a free radical probe (second-order rate constant k = 5 × 10⁻⁶). 9 M -1 S -1 This allows for further identification of ·OH. For example... Figure 4 As shown in (b), in the Co@N-CNTs-2 / PAA system, when 0.25 mM p-CBA was added as a quencher, the removal rate of ACV was 91.46%, and only 6.79% was inhibited. Figure 4 As shown in (c), when p-CBA was used as a ·OH probe, 11.5% of p-CBA was consumed within 10 minutes. In the presence of 25 mMMTBA, the consumption of p-CBA was essentially completely suppressed. Furthermore, the calculated steady-state concentration of ·OH was 2.26 × 10⁻⁶. -12 Therefore, under the activation of Co@N-CNTs-2, ·OH is not the main active free radical generated by PAA.

[0071] Methanol (MeOH) can simultaneously quench ·OH and RO·. When the amount of MeOH increased from 0 mM to 25 mM, the removal rate of ACV decreased from 98.25% to 20.33%. Figure 4 (d) indicates that RO· is the major active free radical in the Co@N-CNTs-2 / PAA system. To further determine the major RO· in this system, such as... Figure 4 As shown in (e), to eliminate the influence of ·OH on degradation and to more accurately determine the effects of ·CH3 and CH3OO· on the degradation system, an additional N2 experiment was conducted in the presence of TBA (concentration of 10 mM). Compared with the aerobic experiment without quencher, the degradation efficiency of ACV remained essentially unchanged. Furthermore, CH3C(O)O· can self-decompose to produce ·CH3, and ·CH3 can react rapidly with O2 to generate CH3OO·, which has a weaker oxidizing ability (equations (6)-(7)). Therefore, introducing O2 into the system, such as...Figure 4 (e) As shown in Figure 2e, the removal of ACV was not significantly promoted under the condition of oxygen-rich, which indicated that the dissolved oxygen had little effect on the system, and the effects of CH3and CH3OO· on the degradation system could be excluded. Since peroxyl radicals are prone to attack C=C, 2,4-hexadienoic acid (2,4-HD) is often used as a quencher of acetyl (aldehyde) oxy radical. As shown in Figure 2f, when only 0.5 mM of 2,4-HD was added to the system, the degradation efficiency of ACV by Co@N-CNTs-2 / PAA decreased to 12.31%. This means that CH3C(O)OO· and CH3C(O)O· are the main R-O· in the Co@N-CNTs-2 / PAA system. Figure 4 (f), When only 0.5 mM of 2,4-HD was added to the system, the degradation efficiency of ACV by Co@N-CNTs-2 / PAA decreased to 12.31%. This means that CH3C(O)OO· and CH3C(O)O· are the main R-O· in the Co@N-CNTs-2 / PAA system.

[0072] The existence and role of the above active radicals were further identified and distinguished by EPR. Since 1 O2can be generated from the spontaneous decomposition of PAA by attacking the central C atom with a peroxyl group (Equation (8)). 2,2,6,6-tetramethyl-4-piperidone (TEMP) is often used as a 1 O2trap. Figure 5 (a) As shown in Figure 2a, no 1:1:1 triplet EPR signal of TEMP- 1 O2was detected in the system with only PAA, which indicated that PAA did not decompose to generate 1 O2without the catalysis of Co@N-CNTs-2. When Co@N-CNTs-2 coexisted with PAA in the system, the EPR spectrum peak signal of TEMP- 1 O2was obviously detected. With the extension of the reaction time or the addition of ACV in the system, the signal of TEMP- 1 O2did not change significantly, which indicated that 1 O2was not involved in the degradation of ACV. 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) is often used as a ·OH trap in EPR technology to identify the existence of ·OH and R-O·. As shown in Figure 2b, no EPR characteristic signal of DMPO-·OH was detected in the PAA and Co@N-CNTs-2 / PAA systems, which may be due to the low concentration of ·OH in the system, which is consistent with the quenching experiment results, and ·OH is not the active radical for ACV degradation. Figure 5 (b) As shown in Figure 2b, no EPR characteristic signal of DMPO-·OH was detected in the PAA and Co@N-CNTs-2 / PAA systems, which may be due to the low concentration of ·OH in the system, which is consistent with the quenching experiment results, and ·OH is not the active radical for ACV degradation. Figure 5 (c) As shown in Figure 2c, according to the research of Chen et al., a more obvious EPR signal of DMPO-CH3C(O)OO· was detected in the ethanol system with a larger viscosity, and according to the quenching experiment and EPR technology, it can be determined that the main active radicals for ACV degradation in the Co@N-CNTs-2 / PAA system are CH3C(O)OO· and CH3C(O)O·.

[0073]

[0074] CH3CO3H + CH3C(O)O· → CH3C(O)OO· + CH3C(O)OH (4)

[0075]

[0076] CH3CO3H + CH3CO3 - → CH3CO2H + CH3CO2 - + 1 O2 (7)

[0077] 4、Experimental conditions on the degradation of ACV:

[0078] As shown in Figure 6 (a), when the concentration of PAA increased from 0.05 mM to 0.5 mM, the degradation efficiency of ACV by Co@N-CNTs-2 / PAA system increased from 25.09% to 99.88%. This is probably because the more the concentration of PAA, the more active species generated. Similarly, as shown in Figure 6 (b), when the dosage of catalyst increased from 0.01 g / L to 0.05 g / L, the corresponding degradation efficiency of ACV increased from 83.20% to 98.25%. However, when the dosage of catalyst further increased to 0.1 g / L, the degradation efficiency of ACV decreased to 95.75%, which is probably due to the rapid activation of PAA by excessive catalyst to generate a large amount of free radicals, which accumulated and self-quenched in a short time. Therefore, considering the degradation effect and economic cost, the concentration of PAA was selected as 0.25 mM and the dosage of catalyst was selected as 0.05 g / L as the subsequent experimental conditions.

[0079] In addition, the initial pH of the solution has a very important influence on the Co@N-CNTs-2 / PAA system, not only affecting the existence form of PAA molecules in the solution, but also affecting the surface properties of the catalyst surface. As shown in Figure 6 (c), under different initial pH conditions, the removal rate of ACV by Co@N-CNTs-2 / PAA system was in the order of pH = 7 (98.25%) > pH = 5 (46.02%) > pH = 9 (42.84%) > pH = 11 (14.98%) > pH = 3 (5.49%), which indicates that the removal effect of ACV by Co@N-CNTs-2 / PAA system is best under neutral conditions. This result can be analyzed from the following points: first, the dissociation constant pK a of PAA is 8.2, so under alkaline conditions, PAA -As a conjugated form of the PAA molecule, Co@N-CNTs-2 exists in solution. The isoelectric point pH of Co@N-CNTs-2 was determined. IEP It is 8.13 ( Figure 6 (d) This means that Co@N-CNTs-2 carries a negative charge under alkaline conditions, similar to PAA, which also carries a negative charge. - Electrostatic repulsion occurs, causing PAA - Difficulty in coupling with Co@N-CNTs-2 hinders PAA - Activation. When the solution is under acidic conditions, PAA mainly exists as neutral molecules. 0 However, compared to PAA, PAA exists. 0 It is much more stable than PAA, thus inhibiting the activation of PAA. Furthermore, under acidic conditions, Co@N-CNTs-2 also electrostatically repels PAA, because Co@N-CNTs-2 carries a positive charge, while PAA reacts with H+. + Due to hydrogen bonding, they also carry a positive charge. Therefore, based on the above analysis, Co@N-CNTs-2 combined with PAA is more practically significant for wastewater treatment when the solution is at a neutral pH.

[0080] 5. The influence of water-based substrate:

[0081] Actual water samples typically contain inorganic anions and organic matter, which significantly influence the degradation process. Therefore, this example explores the role of HCO3. - CO3 2- Cl - And the effect of humic acid (HA) on the degradation of ACV in the Co@N-CNTs-2 / PAA system. Figure 7 As shown in (a), HCO3 - It inhibits the degradation of ACV. When HCO3 in the system - As the concentration increased from 0 mM to 0.2 mM, the degradation efficiency of ACV decreased from 98.25% to 67.71%. When HCO3... - When the concentration increased to 1.0 mM, the removal rate of ACV was only 31.56%, indicating that regardless of the low concentration of HCO3... - Still a high concentration of HCO3 - All of these significantly inhibited the degradation of ACV by the Co@N-CNTs-2 / PAA system. Based on previous reports on transition metal / PAA studies, HCO3-... - This not only affects the solution pH but may also form inactive metal bicarbonate complexes on the catalyst surface, hindering the interaction between the catalyst and PAA. Similarly, CO32-... 2- The presence of [certain substances] can also have a negative effect on the removal of ACVs. For example... Figure 7(b) shows that when CO3 2- The degradation efficiency of ACV decreased from 98.25% to 16.85% when the concentration of CO3 2- was increased from 0 mM to 1.0 mM. According to previous studies, CO3 · can react with CH3C(O)OO · to generate CO3 ·- with weaker oxidation ability to ACV (equations (8)-(9)).

[0082] Cl - also has a very important impact on the PAA system. As shown in Figure 7 (c), whether it is a low concentration of Cl - or a high concentration of Cl - , it has an inhibitory effect on the removal of ACV. When the concentration of Cl - increases from 0 mM to 10 mM, the removal rate of ACV decreases from 98.25% to 54.14%. Cl - can react with active radicals to generate Cl · , Cl2 ·- and other radicals (equations (10)-(12)). However, Cl · , Cl2 ·- has high oxidation selectivity and different removal effects on different organic pollutants. Obviously, chlorine-containing radicals have low reactivity in the degradation of ACV.

[0083] In addition, this embodiment also evaluates the effect of humic acid (HA) on the degradation of ACV by Co@N-CNTs-2 / PAA. As shown in Figure 7 (d), HA has a strong inhibitory effect on the degradation of ACV. When the amount of HA is 10 mM, the degradation efficiency of ACV is only 17.45%. This may be due to the fact that on the one hand, HA can act as a radical scavenger, reducing the steady-state concentration of active radicals in the system, such as HA can scavenge R-O · with a second-order rate constant of 10 4 L mg -1 s -1 . On the other hand, some organic functional groups in HA, such as carboxyl (-COOH) and phenolic (-OH), can be adsorbed on the surface of the catalyst, occupying active sites and hindering the activation of PAA. Therefore, the presence of HA inhibits the degradation of ACV by Co@N-CNTs-2 / PAA.

[0084] CO3 2- +CH3C(O)O·→CO3 ·- +CH3C(O)O - (8)

[0085] CO3 2- +CH3C(O)OO·→CO3 ·- +CH3C(O)O - (9)

[0086] CH3C(O)OO·+Cl - +H + →Cl·+CH3C(O)OOH (10)

[0087] CH3C(O)O·+Cl - +H + →Cl·+CH3C(O)OOH (11)

[0088] Cl·+Cl - →Cl2 ·- (12)

[0089] 6. Cyclic stability of Co@N-CNTs-2 and its activation mechanism for PAA:

[0090] The reusability of a catalyst is an important indicator for evaluating its practicality. Four recovery experiments were conducted, in which the catalyst was thoroughly washed with anhydrous ethanol and ultrapure water, dried, and reused in degradation experiments to evaluate the catalytic performance of Co@N-CNTs-2. Figure 8 As shown in (a), the degradation efficiency of fresh Co@N-CNTs-2-activated PAA for ACV was 98.25%. After the second and third uses, the removal rates of ACV were 87.58% and 80.11%, respectively, which were significantly lower than the catalytic effect of the first use, but the catalytic effect could still reach over 80%. When used for the fourth time, the degradation efficiency of Co@N-CNTs-2-activated PAA for ACV decreased to 67.60%. This may be due to the loss of some metal ions during use and washing. Nevertheless, Co@N-CNTs-2 still showed good catalytic effect on PAA in four repeated uses, and has certain application prospects in the removal of ACV.

[0091] To investigate the catalytic mechanism of Co@N-CNTs-2 activating PAA, XPS analysis was performed on fresh and used Co@N-CNTs-2 to compare the changes in catalyst surface elemental composition and valence state before and after the reaction. Figure 8 As shown in (b), after Co@N-CNTs-2 is used, Co 0 Co 2+ The relative percentage content decreased from 77.90% and 22.10% to 71.11% and 10.87%, respectively, indicating that Co 0 and Co 2+is the catalytic site of PAA activation, and the Co 2p XPS peak appears at 782.94 eV 3+ The deconvolution peak of Co 2p XPS is at 782.94 eV, and the Co species undergoes a change from low valence to high valence during the catalytic process. Metal nanoparticles have high surface energy, making the nanoparticles have high activity, so Co 0 can effectively activate PAA in coordination with the carbon skeleton to produce active free radicals. In addition, PAA is reported to act as an electron acceptor, accepting electrons from the surface of the catalyst to form an electron-bearing donor, which provides electrons for Co 3+ , thereby promoting the decomposition of PAA to produce CH3C(O)O· and CH3C(O)OO·. In summary, the activation mechanism of Co@N-CNTs-2 for PAA is shown in equations (13)-(16), and the active species (ROS) produced attack the ACV molecule, ultimately converting the pollutants into CO2 and H2O.

[0092] Co 0 @N-CNTs-2 + CH3CO3H → Co 2+ @N-CNTs-2 + CH3C(O)O· + OH - (13)

[0093] Co 2+ @N-CNTs-2 + CH3CO3H → Co 3+ @N-CNTs-2 + CH3C(O)O· + OH - (14)

[0094] Co 3+ @N-CNTs-2 + C2H4O3H → Co 2+ @N-CNTs-2 + CH3C(O)OO· + H + (15)

[0095] ROS + ACV → intermediates → CO2 + H2O (16)

[0096] 7. Degradation pathway and toxicity analysis of intermediates:

[0097] ACV and its degradation products were identified by high performance liquid chromatography-time of flight mass spectrometer (HPLC-QTOF-MS, Japan SHIMADZU, LC-MS 9030), as Figure 9 shown, 6 intermediates (m / z = 186, 214, 205, 91, 167, 165) were identified. Under the attack of ROS, ACV is directly cleaved to generate P1, and its [M+H] +The peak is located at m / z = 186. The six-membered heterocyclic ring of ACV is opened by the attack of active radicals, and the single-sided carbon chain terminal hydroxyl group is oxidized to carboxyl group, forming P2, which [M+H] + The peak is located at m / z = 214. Similarly, P3 ([M+H] + The peak is located at m / z = 205) is caused by the rupture of the purine ring of ACV under the oxidation of ROS. The ACV molecule is composed of guanine and a branched chain. According to previous reports, ACV can be oxidized to guanine-9-hydroxyacetic acid during oxidation, and then converted to guanine, while the branched chain is broken to produce methoxyacetic acid (P4, m / z = 91). Guanine can also be further oxidized to P5 ([M+H] + The peak is located at m / z = 167), and then under the attack of free radicals, P5 undergoes six-membered ring rupture, decarboxylation, nitration, and finally forms 1,1,2-trinitroethane (P6, m / z = 165). Finally, these intermediates will be converted to CO2 and H2O under the continuous oxidation of ROS.

[0098] According to the quantitative structure-activity relationship (QSAR), the ECOSAR program is used to predict the chronic and acute toxicity of ACV and degradation intermediates to aquatic organisms (fish, water flea, green algae). As shown in Figure 10 The ACV molecule is green and non-toxic to fish, water flea, and green algae in terms of acute toxicity, but is harmful to water flea in terms of chronic toxicity. Among the degradation products, P1 is only non-toxic to fish in terms of acute toxicity. Unlike P1, P2 and P4 only show low acute toxicity to fish. P3 is green and non-toxic to water flea in terms of acute and chronic toxicity, and shows chronic non-toxicity to green algae. P5 shows low toxicity to green algae in terms of acute or chronic toxicity. P6 shows harmful or low toxicity to fish, water flea, and green algae. In summary, ACV is converted to harmless or less harmful intermediates after degradation by the Co@N-CNTs-2 / PAA system, further demonstrating the practical application ability of Co@N-CNTs-2 in water treatment.

[0099] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A catalyst comprising a cobalt-coated nitrogen-doped carbon nanotube, characterized in that, The preparation method is: mixing the polyamide acid solution and the carbon nanotube dispersion liquid uniformly, heating and refluxing, collecting the solid after reaction, dispersing the solid in a cobalt salt solution, heating to 70-90 ℃ and stirring, introducing cobalt into the solid, and pyrolyzing the cobalt-introduced solid under an inert atmosphere to obtain the product. The addition ratio of the carbon nanotube, the polyamide acid and the cobalt salt is 50:85-95:1.5-4.5, mg: mg: mmol. The pyrolysis temperature is 550-650 ℃, and the pyrolysis time is 1.5-2.5 h. The preparation method of the polyamide acid solution is: adding ethylenediamine and pyromellitic dianhydride into a solution and stirring.

2. The catalyst coated with cobalt and nitrogen-doped carbon nanotubes according to claim 1, wherein the nitrogen-doped carbon nanotubes are grown on the surface of the cobalt particles. The addition ratio of the carbon nanotube and the cobalt salt is 50:2.8-3.2, mg: mmol.

3. The catalyst coated with cobalt and nitrogen-doped carbon nanotubes according to claim 1, wherein the nitrogen-doped carbon nanotubes are grown on the surface of the cobalt particles. The heating reflux temperature is 145-155 ℃. The stirring time at 70-90 ℃ is 10-14 h.

4. A method of activating a peroxi acetic acid-degrading antiviral drug, characterized by, The solution containing the antiviral drug is added with peracetic acid and the nitrogen-doped carbon nanotube coated cobalt catalyst according to any one of claims 1-3, mixed and treated, and the pH is adjusted to 5-11. The antiviral drug is one or more of acyclovir, lamivudine, ganciclovir and favipiravir.

5. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The concentration of peracetic acid in the mixed solution is 0.05-0.5 mmol / L.

6. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The concentration of peracetic acid in the mixed solution is 0.20-0.5 mmol / L.

7. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The concentration of peracetic acid in the mixed solution is 0.20-0.30 mmol / L.

8. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The addition amount of the nitrogen-doped carbon nanotube coated cobalt catalyst is 0.01-0.1 g / L.

9. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The addition amount of the nitrogen-doped carbon nanotube coated cobalt catalyst is 0.05-0.1 g / L.

10. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The addition amount of the nitrogen-doped carbon nanotube coated cobalt catalyst is 0.05-0.06 g / L.

11. The method for activating peracetic acid to degrade antiviral drugs as described in claim 4, characterized in that, The solution containing the antiviral drug is added with peracetic acid, and the pH is adjusted to 6.8-7.

2.

12. The use of the method for degrading the antiviral drug by activating peracetic acid according to any one of claims 4-11 in treating wastewater containing the antiviral drug.

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