CN109589984B - Preparation method and application of double-reaction-channel photocatalyst - Google Patents

Preparation method and application of double-reaction-channel photocatalyst Download PDF

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CN109589984B
CN109589984B CN201811515378.XA CN201811515378A CN109589984B CN 109589984 B CN109589984 B CN 109589984B CN 201811515378 A CN201811515378 A CN 201811515378A CN 109589984 B CN109589984 B CN 109589984B
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ethanol
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CN109589984A (en
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逯子扬
何凡
于泽惠
宋旼珊
周国生
朱晓蝶
李武举
刘馨琳
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Jiangsu University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/80—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with zinc, cadmium or mercury
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0215—Coating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/341—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation
    • B01J37/343—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation making use of electric or magnetic fields, wave energy or particle radiation of ultrasonic wave energy
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/30—Treatment of water, waste water, or sewage by irradiation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/34—Organic compounds containing oxygen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/38—Organic compounds containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2305/00—Use of specific compounds during water treatment
    • C02F2305/10—Photocatalysts

Abstract

The invention belongs to the technical field of synthesis of environmental materials, and particularly relates to a preparation method and application of a double-reaction-channel photocatalyst. The method comprises the following specific steps: carboxylation of ZnFe2O4Adding into the mixed solution of water and ethanol, mechanically stirring, adding K2Cr2O7Performing ultrasonic treatment, adding 4-vinylpyridine, EGDMA and AIBN, performing ultrasonic treatment, transferring the solution into a quartz glass flask, adding P123, placing the quartz glass flask into a microwave reactor, stirring, washing and performing vacuum drying to obtain a solid product; then, removing P123, eluting hexavalent chromium ions by using EDTA, separating by using a magnet, rinsing and drying to obtain a product; the material of the invention can selectively reduce hexavalent chromium ions and degrade tetracycline.

Description

Preparation method and application of double-reaction-channel photocatalyst
Technical Field
The invention belongs to the technical field of synthesis of environmental materials, and particularly relates to a preparation method of a double-reaction-channel photocatalyst and selective reduction of Cr by using the same6+And the application of simultaneous photocatalytic degradation of tetracycline.
Background
Nowadays, environmental pollution is a topic which people find out to be hot, and is a difficult problem which people in various societies need to solve urgently, and it is a common goal of people to successfully research and widely use an environment-friendly, economical and efficient method to solve the problem of environmental pollution. As is well known, the pollutants in water environment are various and complex, and in recent years, human health problems and environmental problems caused by the overproof antibiotics and heavy metal ions remained in water are frequently reported. Tetracycline is a common antibiotic and is widely used in daily life of people, however, the abuse of tetracycline not only causes a large amount of residual pollutants to be discharged into water bodies, resulting in negative effects on the water environment, but also inhibits many water treatment progresses. Moreover, hexavalent chromium ions are considered to be one of the most toxic heavy metal ions, and have the characteristic of being biodegradable, so that the conventional sewage treatment process cannot efficiently remove the hexavalent chromium ions, and thus the hexavalent chromium ions are very easy to enter human bodies, and cause serious harm. The toxicity of the reduced chromium ions is far less than that of hexavalent chromium ions, so that the selective reduction of the hexavalent chromium ions and the simultaneous degradation of tetracycline have very important research significance in consideration of the environmental pollution and the harm of tetracycline and hexavalent chromium to human bodies. Therefore, it is challenging and innovative to design a material that can simultaneously selectively reduce hexavalent chromium ions and degrade tetracycline in water.
The photocatalytic technology is considered to be an effective environmental protection solution due to the advantages of energy conservation, environmental protection, low cost and the like. The photocatalytic degradation method oxidizes antibiotics into substances with low biological toxicity and easy biodegradation, and even converts the antibiotics into harmless compounds, and the degradation range and the effect of the photocatalytic degradation method are superior to those of a common sewage treatment process to a certain extent. The photocatalytic reduction method can reduce high-valence and high-toxicity metal ions into low-valence and low-toxicity ions, and can effectively control the high-valence and high-toxicity ions in the aspect of toxicity. The existing photocatalysts designed in the field of photocatalysis are various in types, but the defects of poor photocatalytic effect, poor light stability, short photoresponse interval, easy recombination of photoproduction electron holes and the like are difficult to avoid.
On the other hand, in order to selectively reduce hexavalent chromium ions, it is first necessary to achieve selective adsorption of the hexavalent chromium ions among numerous ions at high concentration, thereby introducing an ion imprinting technique. The ion imprinting technique is an extension of the molecular imprinting technique, which is a technique for generating recognition sites in a macromolecular matrix using template ions, in which a large number of imprinted cavities designed for the template ions are uniformly distributed, the cavities corresponding to the shape, size and functional groups of the template ions. Therefore, the ion imprinted polymer has a specific ion recognition ability and a high binding affinity for the template ion.
In the last years, researches on photocatalysts as selective adsorbents for treating organic pollutants and heavy metal ions in water and ion imprinted polymers as template ions have attracted wide attention, and the simultaneous realization of degradation of organic matters and reduction of heavy metal ions by utilizing a photocatalytic mechanism has great significance, however, researches on the effective combination of photocatalysis and ion imprinted technologies for treating various pollutants and reducing heavy metals in complex water environments are rarely reported. Furthermore, to our knowledge, the realization of selective reduction of heavy metal ions and simultaneous degradation of antibiotic residues based on dual reaction channels combined with photocatalytic and ion imprinting techniques is unprecedented.
Disclosure of Invention
In order to overcome the defect that a photo-generated electron hole generated by a photocatalyst is easy to recombine, the invention introduces the imprinting layer with conductivity, so that the photo-generated electron can be easily transferred, and meanwhile, the electron and the hole can respectively carry out photodegradation and reduction reactions in different reaction channels, thereby greatly improving the photocatalytic efficiency.
The invention firstly provides a double reaction channel photocatalyst which is ZnFe2O4Coating an ion imprinting layer on the surface of the photocatalyst serving as a matrix by using an ion imprinting technology; the ion imprinting layer is provided with a large number of mesoporous channels and hexavalent chromium ion imprinting holes; 0.05g of the double reaction channel photocatalyst is used for photocatalytic degradation of 100mL of 20mg/L tetracycline solution, and the degradation degree C/C is reduced under 1h of simulated sunlight irradiation0Is 0.416; in addition, 0.05g of the dual reaction channel photocatalyst was used for 100mL of 10mg/L Cr6+And Ag+In the mixed solution, the absorption capacity of the material to hexavalent chromium ions within 1 hour is up to 150.43mg/g, and six ions within 2 hoursThe reduction rate of the valence chromium ions can reach 92.67%.
The invention also provides a preparation method of the double-reaction-channel photocatalyst, which comprises the following steps:
step 1: ZnFe2O4The synthesis of (2):
first, FeCl is added3·6H2O and ZnCl2Dissolving in ethylene glycol, stirring by using a magnetic stirrer to obtain a clear solution, adding potassium acetate, continuously and mechanically stirring to be uniform, transferring the solution into an autoclave for reaction, collecting a black product by using a magnet, washing the black product by using distilled water and ethanol for a plurality of times, and finally, drying in vacuum at room temperature to obtain a final sample.
Step 2: ZnFe2O4Modification of carboxyl group (2):
firstly, ZnFe is mixed2O4Dispersing the powder in distilled water, performing ultrasonic treatment for a period of time, adding citric acid into the solution after forming a uniform solution, mechanically stirring for a period of time at a proper temperature in the atmosphere of nitrogen, separating the obtained precipitate with a magnet, washing with distilled water and ethanol for several times, and vacuum drying to obtain carboxylated ZnFe2O4。
And step 3: synthesis of a double reaction channel photocatalyst:
first, carboxylated ZnFe2O4Adding the mixture into an ethanol solution, and mechanically stirring at room temperature to obtain a solution A; at the same time, K is2Cr2O7Dissolving in ethanol solution, performing ultrasonic treatment, adding 4-vinylpyridine, EGDMA and AIBN after the solution is uniform, continuing ultrasonic dispersion until the solution is dissolved, and marking as solution B; finally, transferring the solution A and the solution B together into a quartz glass flask, adding P123, placing the quartz glass flask and the solution B into a microwave reactor for reaction, after the reaction is finished, cooling the container to room temperature, collecting the final product through magnet separation, washing the final product with absolute ethyl alcohol and deionized water to remove excessive solvent, performing vacuum drying, removing the P123 from the obtained solid product with acetone in a Soxhlet extractor, then eluting hexavalent chromium ions with EDTA, separating with a magnet, and rinsing the solid product with distilled water and ethanol to be neutralAnd vacuum drying to obtain the double reaction channel photocatalyst.
In step 1, the FeCl3·6H2O、ZnCl2The dosage ratio of the ethylene glycol to the potassium acetate is 4 mmol: 2 mmol: 15mL of: 40mmol, stirring time of magnetic stirring is 30min, the reaction temperature of the autoclave in a vacuum drying oven is 180 ℃, the reaction time is 24h, and the rotation speed of mechanical stirring is 600 rpm/min.
In step 2, the ZnFe2O4The dosage ratio of the powder, the citric acid and the distilled water is 2 g: 1 g: 50mL, and the ultrasonic time is 30 min; the mechanical stirring time is 1h, the reaction condition is 60 ℃, the reaction is carried out in an oil bath pan, and the rotating speed of the mechanical stirring is 600 rpm/min.
In the steps 1-2, the temperature of vacuum drying is 30 ℃, and the drying time is 12 h.
In step 3, in solution A, the carboxylated ZnFe2O4And the dosage ratio of the ethanol solution is 0.3 g: 40mL, wherein the volume ratio of water to ethanol in the ethanol solution is 5: 3.
in step 3, in the solution B, the K is2Cr2O7Ethanol, 4-vinylpyridine, EGDMA and AIBN were used in a ratio of 1 mmol: 10mL of: 5 mmol: 5 mmol: 0.04 g. K2Cr2O7And the dosage ratio of P123 is 1 mmol: 1.5 g.
Carboxylated ZnFe when solution A and solution B are mixed2O4、K2Cr2O7The dosage ratio of the components is 0.3 g: 1 mmol.
In the step 3, the ultrasonic time is 30 min.
In the step 3, the reaction power in the microwave reactor is 600W, the working temperature is 70 ℃, the working time is 90 minutes, and the stirring speed is 2000 rpm.
In step 3, the dosage ratio of the solid product to acetone is 0.5 g: 100 mL; the elution temperature was 60 ℃ and the elution time was 24 h.
In the step 3, the concentration of the EDTA is 0.5 g/L.
In the step 3, the temperature of the vacuum drying is 30 ℃, and the drying time is 12 h.
The dual-channel photocatalyst of the invention is ZnFe2O4The ion imprinting layer is coated with a selective ion imprinting layer, and the ion imprinting layer is provided with a large number of mesoporous channels and target ions Cr6+The imprinting holes form double channels, and meanwhile, the conductivity of the functional monomer can effectively separate electrons and holes, so that degradation reaction and reduction reaction are carried out in different reaction channels.
The double-reaction-channel photocatalyst prepared by the invention is used for selectively reducing Cr based on different reaction channels6+And the application of the simultaneous photocatalytic degradation of tetracycline.
The invention has the beneficial effects that:
(1) the prepared double-reaction-channel photocatalyst has the capability of selectively adsorbing hexavalent chromium ions due to the fact that a large number of hexavalent chromium ion imprinted holes exist in the imprinted layer, the adsorption capacity of the prepared double-reaction-channel photocatalyst for the hexavalent chromium ions can reach 150.43mg/g, is far higher than that of silver ions, is also far higher than that of other materials for the hexavalent chromium ions, and shows excellent selectivity.
(2) Due to the existence of the mesoporous and the conductive imprinting layer, the prepared double-reaction-channel photocatalyst can generate different reaction channels to realize the degradation of tetracycline and the reduction of copper ions at the same time.
(3) In the introduction process of the double-reaction-channel photocatalyst prepared by the invention, 4-vinylpyridine is used as a functional monomer, and because of the conductivity of the double-reaction-channel photocatalyst, photoproduction electrons can be freely transferred on the ion imprinting layer, and the recombination of the photoproduction electrons and cavities is inhibited, so that hexavalent chromium ions can be reduced on imprinting holes, and in addition, ZnFe2O4The generated cavity can degrade tetracycline entering through the mesopores, so that degradation reaction and reduction reaction are carried out in two different reaction channels, and the photocatalytic efficiency is improved.
(4) The double-reaction-channel photocatalyst prepared by the invention can selectively reduce hexavalent chromium ions and synchronously degrade tetracycline, and no material synchronously used for photodegradation and selective reduction by utilizing photocatalysis and ion imprinting technologies is reported at present, so that the material prepared by the invention has uniqueness and innovation, and has the advantages of low cost, high utilization rate, strong pertinence and good effect.
Drawings
FIG. 1 shows XRD spectra of different samples, where a is ZnFe2O4B is carboxylated ZnFe2O4And c is a double reaction channel photocatalyst.
FIG. 2 shows FT-IR spectra of different samples, a is ZnFe2O4B is carboxylated ZnFe2O4And c is a double reaction channel photocatalyst.
FIG. 3 shows SEM (a), TEM (b), HR-TEM (c) and SAED (d) spectra of the dual reaction channel photocatalyst.
FIG. 4 shows the nitrogen adsorption-desorption isotherms of different samples, a being ZnFe2O4The nitrogen adsorption-desorption isotherm of the double reaction channel photocatalyst, b is the nitrogen adsorption-desorption isotherm of the double reaction channel photocatalyst, c is the nitrogen adsorption-desorption isotherm of the non-mesoporous non-imprinted polymer, d is ZnFe2O4The average pore size distribution curve of (a), e is the average pore size distribution curve of the double reaction channel photocatalyst, and f is the average pore size distribution curve of the non-mesoporous non-imprinted polymer.
FIG. 5 shows the magnetization curves of different samples, a being ZnFe2O4And b is a double reaction channel photocatalyst.
Fig. 6 shows a photocatalyst dispersion state a and a magnet attraction state b according to the present invention.
FIG. 7 is a graph of the photodegradation of tetracycline by different samples, wherein a is ZnFe2O4B is a double reaction channel photocatalyst, and c is a non-mesoporous non-imprinted polymer.
FIG. 8 is a diagram of different samples for selective reduction investigation of hexavalent chromium ions, wherein a is ZnFe2O4B is a double reaction channel photocatalyst, and c is a non-mesoporous non-imprinted photopolymer.
FIG. 9 is a graph for stability test of dual reaction channel photocatalyst.
Detailed Description
The invention is further illustrated by the following examples.
Evaluation of tetracycline adsorption Activity: in DW-01 model photochemical reaction instrument, 100mL 20mg/L tetracycline solution is added into the reactor and its initial value is measured, then 0.05g sample is added, without turning on light source, setting temperature at 30 deg.C, without turning on light irradiation, aerating (aeration amount is 2mL/min), turning on magnetic stirring (rotation speed is 600rpm/min), sampling and analyzing at an interval of 10min, its concentration is measured by UV-visible spectrophotometer, and by the formula: q ═ C0C) V/m calculating the adsorption capacity Q, where C0Is the initial concentration of tetracycline, C is the concentration of tetracycline solution at which adsorption equilibrium is reached, V is the volume of the solution, and m is the mass of the sample added.
Evaluation of hexavalent chromium ion adsorption activity: the method is carried out in a DW-01 photochemical reactor, 100mL of 10mg/L hexavalent chromium ion solution is added into a reactor and each initial value is measured, then 0.05g of sample is added, a light source is not started, the temperature is set to be 30 ℃, light irradiation is not started, air is introduced (the aeration amount is 2mL/min), magnetic stirring is started (the rotating speed is 600rpm/min), sampling analysis is carried out at intervals of 10min, the concentration of the hexavalent chromium ion solution is measured by a diphenylcarbazide method, and the formula is shown in the specification: q ═ C0C) V/m calculating the adsorption capacity Q, where C0Is the initial concentration of hexavalent chromium ions, C is the concentration of hexavalent chromium ions at which adsorption equilibrium is reached, V is the volume of the solution, and m is the mass of the sample added.
Evaluation of photocatalytic degradation Activity: adding 100mL of 20mg/L tetracycline solution into a reactor and measuring the initial value thereof in a DW-01 type photochemical reaction instrument, then adding 0.05g of sample, starting a light source, setting the temperature to be 30 ℃, starting light irradiation, introducing air (the aeration amount is 2mL/min), starting magnetic stirring (the rotating speed is 600rpm/min), after reaching the adsorption balance, irradiating by using simulated sunlight, starting the magnetic stirring (the rotating speed is 600rpm/min), starting an aeration device, introducing air (the flow is 2mL/min), setting the temperature to be 30 ℃, sampling and analyzing at an interval of 10min in the light irradiation process, measuring the concentration by using an ultraviolet-visible spectrophotometer, and measuring the concentration by using a formula：C/C0Calculating the degree of photodegradation of the polymer, wherein C0To obtain the concentration of the tetracycline solution at adsorption equilibrium, C is the concentration of the tetracycline solution measured at time t, and t is the reaction time.
Evaluation of selective adsorption: the method is carried out in a DW-01 type photochemical reactor, 100mL of 10mg/L mixed solution of hexavalent chromium ions and silver ions is added into a reactor and the initial value is measured, then 0.05g of sample is added, a light source is not started, the temperature is set to be 30 ℃, the irradiation is not started, air is introduced (the aeration amount is 2mL/min), magnetic stirring is started (the rotating speed is 600rpm/min), sampling analysis is carried out at 10min intervals in the process, the concentration of the hexavalent chromium ions is measured by a diphenylcarbazide method, the concentration of the silver ions is measured by ICP, and the formula is shown as follows: q ═ C0C) V/m calculation of the adsorption capacity of the respective ions, where C0Is the initial concentration of the particular ion, C is the concentration of the particular ion at which adsorption equilibrium is reached, V is the volume of the solution, and m is the mass of the sample added.
Evaluation of selective reduction: the method is carried out in a DW-01 type photochemical reactor, 100mL of 10mg/L mixed solution of hexavalent chromium ions and silver ions is added into a reactor, the initial value is measured, then 0.05g of sample is added, a light source is not started, the temperature is set to be 30 ℃, light irradiation is not started, air is introduced (the aeration amount is 2mL/min), magnetic stirring is started (the rotating speed is 600rpm/min), after adsorption balance is achieved, a lamp is started for irradiation for 2h, sampling analysis is carried out after irradiation is finished, the concentration of the hexavalent chromium ions is measured by a diphenylcarbazide method, ICP is used for measuring the concentration of the silver ions, and the formula is shown as follows: r ═ C0-C)/C0Calculating the reduction ratio of each ion, wherein C0The initial concentration of the specific ion, and C is the concentration of the specific ion after 2h of illumination.
Example 1:
(1)ZnFe2O4the synthesis of (2): 4.325g of FeCl3·6H2O and 1.09g ZnCl2Dissolved in 60mL of ethylene glycol and mixed well, 2.453g of potassium acetate was added to the solution and stirred for 30 minutes, after which the solution was transferred to an autoclave and kept at 180 ℃ for 24 h. Finally, the black product was collected with a magnet and washed several times with distilled water and ethanol, and finally, the sample was real at room temperatureDrying for 12h in air;
(2) carboxylated ZnFe2O4The synthesis of (2): first, 3g of ZnFe was mixed2O4Dispersing the powder in 100mL of deionized water, performing ultrasonic dispersion, adding 1.5g of citric acid into the solution after a uniform solution is formed, mechanically stirring for 1h at 60 ℃ under the protection of nitrogen, separating the obtained precipitate by using a magnet, washing the precipitate for several times by using deionized water and ethanol, and then performing vacuum drying for 12h at 30 ℃;
(3) synthesis of a double reaction channel photocatalyst: 0.6g of carboxylated ZnFe2O4The mixture was added to a mixture of 50mL of deionized water and 30mL of ethanol, and then stirred at room temperature for 30min continuously, which was designated as solution A. 0.5884g K will be mixed2Cr2O7Dissolved in 20mL of ethanol, and sonicated by adding 1.0514g of 4-vinylpyridine and 1.9893g of EGDMA, sonicated for 30min, followed by adding 0.08g of AIBN to the above solution and stirring at room temperature. Finally 3g P123 was added. The resulting mixture was transferred to a quartz glass container and placed in a microwave reactor. The working power is 600W, the working temperature is 70 ℃, the working time is 90min, the stirring speed is 2000 r/min, after the reaction is finished, after the container is cooled to the room temperature, the final product is separated and collected by a magnet, the excessive solvent is removed by washing with absolute ethyl alcohol and deionized water for three times, and then the solid product is dried in a vacuum oven at 30 ℃ for 12 h;
the dried solid product was extracted with acetone in a soxhlet extractor at 60 ℃ for 24h for P123 removal, after which the sample was rinsed with 100mL of 0.5g/L EDTA and transferred to a flask to elute hexavalent chromium ions, then mechanically stirred at 30 ℃ for 12h, the solid sample was separated with a magnet, then rinsed with distilled water and ethanol to neutrality (pH 7), and finally, the solid sample was dried in a vacuum oven at 30 ℃ for 12 h.
(4) Synthesis of a non-mesoporous non-imprinted photocatalyst: in accordance with the method of (3), the steps of adding P123 and removing P123 and adding K are omitted2Cr2O7And a step of eluting hexavalent chromium ions.
Fig. 1 shows XRD spectra of different samples, from which it can be seen that: ZnFe2O4Are located at 29.91 °,35.23 °,42.81 °,53.10 °,56.60 ° and 62.14 °, respectively, which correspond to ZnFe, respectively2O4The (220), (311), (400), (422), (511) and (440) crystal planes of (a). Further comparison of carboxylated ZnFe2O4And the XRD spectrogram of the double-reaction-channel photocatalyst can find that no redundant peak is increased or reduced, which indicates that the ion imprinting layer is successfully coated on ZnFe2O4Surface, and does not change the crystal form of the raw material.
FIG. 2 is a FT-IR spectrum of various samples, from which it can be seen that: carboxylated ZnFe2O4Compared with ZnFe2O4The peak of-COOH was increased, indicating that the surface was successfully grafted with carboxyl groups. As can be seen by comparing the dual reaction channel photocatalyst, the peak thereof not only contains ZnFe2O4Further analysis of the characteristic peaks revealed that C-O, C ═ C and C-N, indicating the presence of EGDMA and 4-vinylpyridine, further confirmed the presence of the ion imprinted layer, indicating that the dual reaction channel photocatalyst has been successfully synthesized.
FIG. 3 is an SEM spectrum (a), a TEM spectrum (b), an HR-TEM spectrum (c) and an SAED spectrum (d) of the dual reaction channel photocatalyst, from which it can be seen that: the double reaction channel photocatalyst is prepared uniformly, the particle size is about 370nm, HR-TEM picture shows that the surface of the double reaction channel photocatalyst is coated by an organic layer, and the crystal comparison can be carried out by SAED, which proves that ZnFe2O4Again, this indicates that the dual reaction channel photocatalyst has been successfully synthesized.
FIG. 4 is a nitrogen adsorption and desorption isotherm of different samples, and it can be seen from the graph that the dual reaction channel photocatalyst has the largest specific surface area, and benefits from a large number of mesoporous channels and imprinted pores on the surface, and in addition, the average pore diameter is smaller than that of ZnFe2O4And a non-mesoporous non-imprinted photocatalyst, which again proves the existence of mesoporous channels and imprinted pores.
Fig. 5 is magnetization curves of different samples, and it can be seen that the dual-reaction-channel photocatalyst still has good magnetic saturation strength after being coated with the imprinting layer, and the magnetic saturation strength value is 49.27emu/g, which indicates that the dual-reaction-channel photocatalyst has good magnetic separation characteristics.
In FIG. 6, a shows a state in which the photocatalyst of the present invention is naturally dispersed in water, and b shows a state after magnetic attraction.
FIG. 7 is a graph of the photodegradation of tetracycline by different samples, from which it can be seen that: ZnFe2O4The degradation degree of the double reaction channel photocatalyst to the tetracycline is the highest, and the degradation degree of the double reaction channel photocatalyst to the tetracycline is slightly lower than that of ZnFe2O4Thus, it was demonstrated that the coating of the imprinted layer did not affect the photodegradation activity of the photocatalyst. In addition, C/C of dual reaction channel photocatalyst was compared with that of non-mesoporous non-imprinted photocatalyst0It can be known that the material with the mesoporous and imprinted pore dual reaction channels shows better tetracycline degradation activity.
FIG. 8 is a diagram of the selective reduction investigation of hexavalent chromium ions by different samples, from which it can be seen that: the reduction rate of the double-reaction-channel photocatalyst to hexavalent chromium ions is as high as 92.67%, which is far higher than the reduction effect of other materials to hexavalent chromium ions, and the result shows that a large number of hexavalent chromium ion imprinted pores on the surface of the double-reaction-channel photocatalyst material play a crucial role in selective adsorption of hexavalent chromium ions and are beneficial to further reduction. In addition, it can be seen that the reduction effect of the double reaction channel photocatalyst on hexavalent chromium ions is obviously better than that of silver ions. As can be seen from the comparison, the imprinted pores of hexavalent chromium ions on the surface of the dual reaction channel photocatalyst represent specific recognition of hexavalent chromium ions, so that hexavalent chromium ions can be selectively adsorbed in the mixed solution and reduced to trivalent chromium ions. While other materials do not exhibit the same properties.
Fig. 9 is a stability investigation of the dual reaction channel photocatalyst, and it can be seen from the figure that, five times of experiments of photodegrading tetracycline and selectively reducing hexavalent chromium ions are performed respectively, neither the degradation rate nor the reduction rate is greatly reduced, which indicates that the dual reaction channel photocatalyst has better stability and can be recycled for multiple times.

Claims (10)

1. A preparation method of a double reaction channel photocatalyst is characterized by comprising the following steps:
ZnFe is mixed with water2O4Dispersing the powder in distilled water, performing ultrasonic treatment for a period of time, adding citric acid into the solution after forming a uniform solution, mechanically stirring in nitrogen atmosphere, separating the obtained precipitate with magnet, washing with distilled water and ethanol for several times, and vacuum drying to obtain carboxylated ZnFe2O4；
Carboxylation of ZnFe2O4Adding the mixture into an ethanol solution, and mechanically stirring at room temperature to obtain a solution A;
at the same time, K is2Cr2O7Dissolving in ethanol solution, performing ultrasonic treatment, adding 4-vinylpyridine, EGDMA and AIBN after the solution is uniform, continuing ultrasonic dispersion until the solution is dissolved, and marking as solution B;
and finally, transferring the solution A and the solution B together into a quartz glass flask, adding P123, placing the quartz glass flask and the solution B into a microwave reactor for reaction, after the reaction is finished, cooling the container to room temperature, separating and collecting a final product through a magnet, washing the final product with absolute ethyl alcohol and deionized water to remove excessive solvent, performing vacuum drying, removing the P123 from the obtained solid product in a Soxhlet extractor through acetone, eluting hexavalent chromium ions through EDTA, separating the hexavalent chromium ions through the magnet, rinsing the hexavalent chromium ions to be neutral through distilled water and ethanol, and performing vacuum drying to obtain the double-reaction-channel photocatalyst.
2. The method of claim 1, wherein the carboxylated ZnFe is in solution A2O4And the dosage ratio of the ethanol solution is 0.3 g: 40mL, wherein the volume ratio of water to ethanol in the ethanol solution is 5: 3.
3. the method of claim 1, wherein the K is in solution B2Cr2O7Ethanol, 4-vinylpyridine, EGDMA and AIBN were used in a ratio of 1 mmol: 10mL of: 5 mmol: 5 mmol: 0.04 g;K2Cr2O7and the dosage ratio of P123 is 1 mmol: 1.5 g.
4. The method of claim 1, wherein the carboxylated ZnFe is mixed with the solution A and the solution B2O4、K2Cr2O7The dosage ratio of the components is 0.3 g: 1 mmol.
5. The method for preparing a dual reaction channel photocatalyst as claimed in claim 1, wherein the ultrasonic time is 30 min.
6. The method for preparing a dual reaction channel photocatalyst as claimed in claim 1, wherein the reaction power in the microwave reactor is 600W, the operating temperature is 70 ℃, the operating time is 90 minutes, and the stirring speed is 2000 rpm.
7. The method for preparing a dual reaction channel photocatalyst as claimed in claim 1, wherein the solid product and acetone are used in a ratio of 0.5 g: 100mL, the elution temperature is 60 ℃, and the elution time is 24 h.
8. The method for preparing a dual reaction channel photocatalyst as claimed in claim 1, wherein the concentration of EDTA is 0.5 g/L.
9. The method for preparing a dual reaction channel photocatalyst as claimed in claim 1, wherein the temperature of the vacuum drying is 30 ℃ and the time is 12 hours.
10. Use of the double reaction channel photocatalyst obtained by the preparation method of any one of claims 1 to 9 in selective Cr reduction based on different reaction channels6+And the application of the simultaneous photocatalytic degradation of tetracycline.
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