Molecularly imprinted cerium oxide / biochar composite material, and preparation method and application thereof

Abstract

The application discloses a kind of molecular imprinting cerium oxide / biochar composite material and its preparation method and application, comprising: cerium oxide / biochar composite material and solvent are mixed, ultrasonic, obtain first solution;At room temperature, first solution and imprinting polymer are mixed, stirring, obtain first mixture, imprinting polymer is the mixture of template molecule and functional monomer, template molecule is p-chlorophenol, and functional monomer is methyl methacrylic acid;First mixture is purged with N2, under sealed, ultraviolet light radiation polymerization 12-24h, obtain second mixture, second mixture is centrifuged, washes to detect no template molecule, clean, dry, obtain molecular imprinting cerium oxide / biochar composite material.Molecular imprinting cerium oxide / biochar composite material as catalyst in the application of photocatalytic removal of p-chlorophenol in water body shows higher specific selectivity and catalytic activity, and the removal efficiency of p-chlorophenol reaches 90%, with good anti-interference in complex water environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of environmental functional materials and water treatment, and particularly relates to a molecular imprinting cerium oxide / biochar composite material and a preparation method and application thereof. BACKGROUND

[0002] p-Chlorophenol is a kind of organic pollutant of refractory and toxic aromatic hydrocarbon. It widely exists in wastewater, and due to its characteristics of biological accumulation and anti-degradation stability in the environment, it can stimulate and induce the distortion and carcinogenesis of human organs, and cause adverse effects on human health. Even at a low concentration, it can seriously threaten human health. Therefore, many countries have listed p-chlorophenol as one of the priority control toxic pollutants.

[0003] Molecular imprinting technology is a method for targeted removal by preparing molecular imprinting polymers with specific recognition sites. In the process of preparing molecular imprinting polymers, the template molecule and the functional monomer are cross-linked and polymerized. This is very important for the formation of imprinting cavities with rigid structure, specific recognition sites and reusability. However, the current polymerization of template molecules and functional monomers is mostly based on chemical cross-linking method of organic reagents. This process inevitably leads to problems such as consumption of a large amount of organic reagents, time-consuming, uneven distribution of imprinting cavities and destruction of composite material structure. In addition, the generation of a large amount of organic solvent waste liquid will also cause the harm of secondary pollution.

[0004] Photocatalysis is an energy-saving, environmentally friendly and simple process. It is based on the absorption of light by the catalyst to produce high-energy electrons and holes, and a large number of ·OH, ·O2 - and H2O2. These substances can act on organic pollutants to completely mineralize them into harmless water, carbon dioxide and other inorganic ions. In the microbial reduction and dechlorination process of dichlorophenol and trichlorophenol, p-chlorophenol will also be an intermediate product. This substance is easy to accumulate and difficult to biodegrade, so it is necessary to study its oxidation or photocatalytic removal method as a potential elimination means. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of a molecular imprinting cerium oxide / biochar composite material. The preparation method prepares a cerium oxide / biochar composite material by a hydrothermal method, creates imprinting cavities on the surface of the cerium oxide / biochar composite material which match the size, shape and charge of p-chlorophenol, and is used for selective recognition and degradation of p-chlorophenol at a low concentration. The preparation method reduces chemical pollution in the preparation process through physical cross-linking.

[0006] Another object of the present application is to provide the molecular imprinting cerium oxide / biochar composite material obtained by the preparation method, wherein the molecular imprinting cerium oxide / biochar composite material comprises biochar and cerium oxide loaded on the biochar, the biochar with a mesoporous structure rich in defects can obtain a higher content of graphitic carbon or pyridine carbon, so as to provide more active key components for the cerium oxide and promote the catalytic oxidation behavior.

[0007] The object of the present application is achieved by the following technical solutions.

[0008] A preparation method of a molecular imprinting cerium oxide / biochar composite material, comprising the following steps:

[0009] S1, mixing cerium oxide / biochar composite material and solvent, ultrasonic, to obtain a first solution, the mass fraction of the cerium oxide / biochar composite material and the volume fraction of the solvent are in a ratio of 1:(100-130), the unit of the mass fraction is g, and the unit of the volume fraction is mL;

[0010] In S1, the cerium oxide / biochar composite material is biochar and cerium oxide loaded on the biochar.

[0011] In S1, the solvent is acetonitrile.

[0012] In S1, the ultrasonic time is 20-30 min.

[0013] S2, mixing the first solution and imprinting polymer at room temperature, stirring, to obtain a first mixture, the ratio of the cerium oxide / biochar composite material and the imprinting polymer is 1:(0.1-12) by mass fraction, the imprinting polymer is a mixture of a template molecule and a functional monomer, the template molecule is p-chlorophenol, and the functional monomer is methacrylic acid, the ratio of the template molecule and the functional monomer is 1:(2-8) by mole fraction;

[0014] In S2, the stirring time is 15-30 min.

[0015] In S2, the ratio of the cerium oxide / biochar composite material and the imprinting polymer is preferably 1:(4-8) by mass fraction, and more preferably 1:8.

[0016] S3, purging the first mixture with N2 to remove oxygen, polymerizing under the irradiation of ultraviolet light for 12-24h to obtain a second mixture, centrifuging the second mixture, washing with a detergent until no template molecules are detected, cleaning to remove the detergent, drying to obtain the molecularly imprinted cerium oxide / biochar composite material.

[0017] In S3, the purging time with N2 is 15-20min.

[0018] In S3, the power of the ultraviolet light irradiation is 8-15W.

[0019] In S3, the polymerization temperature is 50-80℃.

[0020] In S3, the polymerization is carried out under continuous stirring.

[0021] In S3, the detergent is a mixture of acetic acid and ethanol, and the ratio of the acetic acid to the ethanol is 1:(9-10) by volume fraction.

[0022] In S3, the cleaning is carried out alternately with anhydrous ethanol and water.

[0023] In S3, the drying temperature is 60-80℃, and the drying time is 10-14h.

[0024] In the above technical solution, the method for preparing the cerium oxide / biochar composite material is:

[0025] Step 1, mixing biochar, water and anhydrous ethanol, and ultrasonicating until uniform to obtain an A solution, mixing cerium salt and water, and stirring until uniform to obtain a B solution, wherein the ratio of the mass fraction of biochar in the A solution to the volume fraction of water and the volume fraction of anhydrous ethanol in the A solution is (1.5-2):20:20, and the ratio of the mass fraction of cerium salt in the B solution to the volume fraction of water in the B solution is 1:(4-6), the mass fraction is in g, and the volume fraction is in mL;

[0026] In Step 1, the cerium salt is one of cerium nitrate hexahydrate and cerium nitrate heptahydrate.

[0027] In Step 1, the method for obtaining biochar is: drying biochar raw materials at 60-80℃ for 24-36h, then pyrolyzing under N2 atmosphere at 500-600℃ for 1-3h, and cooling to room temperature to obtain biochar.

[0028] In Step 1, the biochar raw materials are one or more of straw, sawdust, animal manure and sludge.

[0029] In Step 1, the ultrasonicating time is 50-80min.

[0030] In step 1, the stirring speed is 450-500 rpm, and the stirring time is 15-20 min.

[0031] In step 2, the A solution and the B solution are mixed and stirred until uniform, and then hydrothermal treatment is performed at 140-180℃ for 10-12 h, and then cooled to room temperature, washed, dried, and calcined at 500-600℃ for 1-3 h under N2 atmosphere to obtain a cerium oxide / biochar composite material, wherein the ratio of biochar in the A solution to cerium salt in the B solution is 1:(2-4) by mass fraction.

[0032] In step 2, the stirring speed is 300-400 rpm, and the stirring time is 20-30 min.

[0033] In step 2, the washing is performed alternately using anhydrous ethanol and water.

[0034] In step 2, the drying temperature is 60-80℃, and the drying time is 10-12 h.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1. The present application successfully prepares a molecularly imprinted cerium oxide / biochar composite material through physical crosslinking, and has the advantages of simple preparation method, small chemical pollution, and low raw material cost.

[0037] 2. The molecularly imprinted cerium oxide / biochar composite material as a catalyst exhibits high specific selectivity and catalytic activity in the photocatalytic removal of p-chlorophenol in water, and the removal efficiency of the molecularly imprinted cerium oxide / biochar composite material for p-chlorophenol reaches 90%, and it has good anti-interference performance in complex water environments. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 XRD patterns of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 and the imprinted biochar prepared in Example 3;

[0039] Figure 2 Fourier infrared spectra of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, the conventional biochar prepared in Example 4, and the molecularly imprinted cerium oxide / biochar composite material prepared in Example 5;

[0040] Figure 3 XPS pattern of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1;

[0041] Figure 4(a) is the UV-Vis diffuse reflectance spectrum of the molecularly imprinted ceria / biochar composite material prepared in Example 1, the conventional ceria / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, and the conventional biochar prepared in Example 4;

[0042] Figure 4(b) is the band gap energy evaluation of the molecularly imprinted ceria / biochar composite material prepared in Example 1, the conventional ceria / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, and the conventional biochar prepared in Example 4;

[0043] Figure 5(a) is the result of the adsorption rate and photocatalytic degradation rate of p-chlorophenol in water by Examples 13-20;

[0044] Figure 5(b) is a trend chart of the effect of catalyst dosage on the removal efficiency of p-chlorophenol;

[0045] Figure 5(c) is a trend chart of the pH value of the p-chlorophenol solution on the removal efficiency of p-chlorophenol;

[0046] Figure 5(d) is a trend chart of the removal efficiency of p-chlorophenol under "dark reaction" and "under photocatalysis";

[0047] Figure 5(e) is a trend chart of the K value in the study of the photodegradation kinetics in the process of removing p-chlorophenol by the catalyst;

[0048] Figure 6(a) is a trend chart of the selective influence of different structural competitors on p-chlorophenol (p-chlorophenol and 2-chlorophenol);

[0049] Figure 6(b) is a trend chart of the removal efficiency of p-chlorophenol in different organic matter environments;

[0050] Figure 6(c) is a trend chart of the selective influence of different structural competitors on p-chlorophenol (p-chlorophenol and enrofloxacin). DETAILED DESCRIPTION

[0051] The technical solutions of the present application are further illustrated below in combination with specific examples.

[0052] The raw materials and their manufacturers involved in the following examples are as follows:

[0053]

[0054]

[0055] The instruments and their model information involved in the following examples are as follows:

[0056] Photochemical instrument: Phchem III, Beijing Nuubit Technology Co., Ltd., Beijing, China (the photochemical instrument is equipped with stirring, heating and light functions);

[0057] UV-Vis spectrophotometer: UV-1801, Beijing Fenrui Analytical Instruments Co., Ltd., Beijing, China;

[0058] Oven: DHG-9030A, Zhongyi Guoke (Beijing) Technology Co., Ltd.;

[0059] Vacuum atmosphere furnace: SQLF-1200, Shanghai Jujing Precision Instrument Manufacturing Co., Ltd., Shanghai, China;

[0060] Ultrasonic cleaner: KQ-500DB, Kunshan Ultrasonic Instrument Co., Ltd., Jiangsu, China;

[0061] Heated magnetic stirrer: HMS-203D, Shanghai Huxi Industrial Co., Ltd.;

[0062] pH meter: 0.01 grade, Mettler Toledo Instruments (Shanghai) Co., Ltd.

[0063] p-Chlorophenol removal efficiency (removal rate%) = (C0 - C) t )*100 / C0, where C0 is the concentration of p-chlorophenol before degradation, and C t The concentration of p-chlorophenol at time t represents the degradation time.

[0064] The method for obtaining the concentration of p-chlorophenol is as follows: Filter the test solution through a 0.22µm nylon syringe filter to obtain the filtrate. Perform a colorimetric reaction on the filtrate using ammonia-ammonium chloride buffer (pH=10), 4-aminoantipyridine, and potassium ferricyanide (colorimetric reaction steps: Take 5mL of filtrate, dilute it to 50mL with water in a colorimetric tube, add 0.5mL of ammonia-ammonium chloride buffer (pH=10), mix well, at which point the pH value is 10.0±0.2, add 1.0mL... A 4-aminoantipyridine aqueous solution (concentration of 4-aminoantipyridine in the aqueous solution is 20 g / L) was mixed well, and then 1.0 ml of potassium ferricyanide aqueous solution (concentration of potassium ferricyanide in the aqueous solution is 80 g / L) was added. After thorough mixing, the solution was sealed and left to stand for 10 min. Using a cuvette with a path length of 20 mm and deionized water as a reference, the absorbance value of p-chlorophenol was measured at 510 nm using a UV-Vis spectrophotometer within 30 min. This absorbance value was taken as the concentration of p-chlorophenol. The determination standard followed the spectrophotometric method for the determination of 4-aminoantipyridine in volatile phenols in water (HJ 503-2009).

[0065] The method for obtaining the biochar used in the following examples is as follows: 10 g of poplar sawdust (powder) with a particle size of 2 mm or less is screened as a biochar raw material, the poplar sawdust is dried in a ceramic crucible in an oven at 80°C for 24 h, the dried poplar sawdust is placed in a ceramic crucible, covered, and placed in a vacuum atmosphere furnace under an N2 atmosphere at 500°C for 2 h of limited oxygen pyrolysis, cooled to room temperature, and the biochar is obtained and stored in the dark for preservation.

[0066] The method for preparing the cerium oxide / biochar composite material in the following examples is as follows:

[0067] Step 1: The biochar, water, and anhydrous ethanol are mixed and ultrasonically treated for 1 h until uniform, to obtain an A solution, and the cerium salt and water are mixed and stirred at a speed of 480 rpm for 15 min until uniform, to obtain a B solution, wherein the ratio of the mass fraction of biochar in the A solution, the volume fraction of water in the A solution, and the volume fraction of anhydrous ethanol in the A solution is 1.65:20:20, and the ratio of the mass fraction of cerium salt in the B solution and the volume fraction of water in the B solution is 4.3:20, the unit of the mass fraction is g, the unit of the volume fraction is mL, and the cerium salt is cerium nitrate hexahydrate;

[0068] Step 2: The A solution and the B solution are mixed and stirred at a speed of 380 rpm for 30 min until uniform, are transferred to an autoclave, are hydrothermally treated at 160°C for 12 h, are cooled to room temperature, are washed with anhydrous ethanol and water alternately for 3 times each to remove impurities, are dried in an oven at 60°C for 12 h, and are limited oxygen calcined at 500°C under an N2 atmosphere for 2 h, to obtain the cerium oxide / biochar composite material, wherein the ratio of the biochar in the A solution and the cerium salt in the B solution is 1.65:4.3 in terms of mass fraction.

[0069] The water in the following examples is deionized water.

[0070] The p-chlorophenol solution in the following examples is a mixture of p-chlorophenol and water.

[0071] Example 1

[0072] A method for preparing a molecularly imprinted cerium oxide / biochar composite material, comprising the following steps:

[0073] S1: The cerium oxide / biochar composite material and the solvent are mixed and ultrasonically treated for 20 min, to obtain a first solution, wherein the ratio of the mass fraction of the cerium oxide / biochar composite material and the volume fraction of the solvent is 0.2:25, the unit of the mass fraction is g, and the unit of the volume fraction is mL, and the solvent is acetonitrile;

[0074] S2, at room temperature, the first solution and imprint polymer were mixed, stirred for 30 min, to obtain the first mixture, the ratio of cerium oxide / biochar composite and imprint polymer was 0.2:1.6 by mass fraction, the imprint polymer was a mixture of template molecules and functional monomers, the template molecule was p-chlorophenol, and the functional monomer was methacrylic acid, the ratio of the template molecule and the functional monomer was 1:4 by mole fraction;

[0075] S3, the first mixture was purged with N2 for 20 min to remove oxygen, and then the reaction bottle containing the first mixture was sealed and placed in a water bath at 60℃, and polymerized under ultraviolet light radiation for 20 h (under continuous stirring), the power of the ultraviolet light radiation was 10 W, to obtain the second mixture, the second mixture was centrifuged, washed with a mixture of acetic acid and ethanol as a washing agent (the ratio of acetic acid and ethanol was 1:9 by volume fraction), and washed until no template molecule was detected, then washed with anhydrous ethanol and water alternately for 3 times each to remove the washing agent, and dried in an oven at 60℃ (the heating rate from room temperature to 60℃ was 5℃ / min) for 12 h, to obtain the molecularly imprinted cerium oxide / biochar composite.

[0076] Example 2

[0077] A method for preparing a conventional cerium oxide / biochar composite, which was basically the same as the method for preparing a molecularly imprinted cerium oxide / biochar composite in Example 1, the only difference was that the “imprint polymer” in Example 1 was replaced by “functional monomer” and the functional monomer in this embodiment was methacrylic acid, and in this embodiment, the ratio of cerium oxide / biochar composite and functional monomer was 0.2:1.16 by mass fraction (i.e. no template molecule was added in this embodiment).

[0078] Example 3

[0079] A method for preparing an imprinted biochar, which was basically the same as the method for preparing a molecularly imprinted cerium oxide / biochar composite in Example 1, the only difference was that the “cerium oxide / biochar composite” in Example 1 was replaced by “biochar” in this embodiment.

[0080] Example 4

[0081] A method for preparing a conventional biochar, which was basically the same as the method for preparing a conventional cerium oxide / biochar composite in Example 2, the only difference was that the “cerium oxide / biochar composite” in Example 2 was replaced by “biochar” in this embodiment.

[0082] Example 5

[0083] A preparation method of a molecularly imprinted cerium oxide / biochar composite material, which is basically the same as the "preparation method of a molecularly imprinted cerium oxide / biochar composite material" in embodiment 1, the only difference is that after centrifugation of the second mixture, it is not washed with a mixed solution of acetic acid and ethanol, but directly dried at 60℃ for 12h, and stored at room temperature in the dark. (That is, the template molecule is not removed in this embodiment).

[0084] Embodiments 6-12

[0085] A preparation method of a molecularly imprinted cerium oxide / biochar composite material, comprising the following steps:

[0086] S1, mix cerium oxide / biochar composite material and solvent, ultrasonic for 20min, to get the first solution, the mass fraction of cerium oxide / biochar composite material and the volume fraction of solvent is 0.2:25, the unit of mass fraction is g, the unit of volume fraction is mL, the solvent is acetonitrile;

[0087] S2, mix the first solution and the imprinting polymer at room temperature, stir for 30min, to get the first mixture, the ratio of cerium oxide / biochar composite material and imprinting polymer is X by mass fraction, the imprinting polymer is a mixture of template molecule and functional monomer, the template molecule is p-chlorophenol, the functional monomer is methacrylic acid, the ratio of template molecule and functional monomer is 1:4 by mole fraction, the value of X is shown in table 1;

[0088] S3, blow the first mixture with N2 for 20min to remove oxygen, then seal the reaction bottle containing the first mixture and place it in a water bath at 60℃, polymerize under ultraviolet light radiation for 20h (under continuous stirring), the power of ultraviolet light radiation is 10W, to get the second mixture, centrifuge the second mixture, use a mixed solution of acetic acid and ethanol as a washing agent (the ratio of acetic acid and ethanol is 1:9 by volume fraction) to wash, wash until no template molecule is detected, then use anhydrous ethanol and water to clean alternately for 3 times each to remove the washing agent, dry in an oven at 60℃ (the heating rate from room temperature to 60℃ is 5℃ / min) for 12h, to get the molecularly imprinted cerium oxide / biochar composite material.

[0089] Table 1

[0090] Example X Example 6 0.2：0.025 Example 7 0.2：0.05 Example 8 0.2：0.2 Example 9 0.2：0.4 Example 10 0.2：0.8 Example 11 0.2：2 Example 12 0.2：2.4

[0091] As Figure 1As shown, the XRD pattern of the molecularly imprinted ceria / biochar composite material prepared in Example 1 showed a broad diffraction peak (22°) and a characteristic peak (26°) corresponding to the imprinted biochar prepared in Example 3, indicating the presence of amorphous carbon and graphitic carbon in the biochar raw material during pyrolysis. In addition, diffraction peaks at 28.541°, 33.074°, 47.474°, 56.330°, 59.076°, 69.399°, 76.683°, 79.057° and 88.408° were observed, corresponding to ceria (PDF #81-0792) (1 1 1), (2 00), (2 2 0), (3 1 1), (2 2 2), (4 0 0), (3 3 1), (4 2 0) and (4 2 2) crystal planes, respectively, indicating that ceria was successfully loaded on the surface of the biochar and maintained good crystallinity.

[0092] Figure 2 Fourier infrared spectra of the molecularly imprinted ceria / biochar composite material prepared in Example 1, the conventional ceria / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, the conventional biochar prepared in Example 4 and the molecularly imprinted ceria / biochar composite material prepared in Example 5 are shown in FIG. 3. Figure 2 As shown, the peak values in the Fourier infrared spectra confirmed the successful imprinting of the surface functional groups of the molecularly imprinted ceria / biochar composite material prepared in Example 1 and p-chlorophenol. Compared to the conventional biochar prepared in Example 4, the C=C peak at 1650 cm -1 was significantly reduced in the molecularly imprinted ceria / biochar composite material prepared in Example 1, while a vibration peak caused by Ce-O bonds appeared at 461 cm -1 This phenomenon was attributed to the defects in the biochar being filled by ceria after hydrothermal treatment, indicating that the molecularly imprinted ceria / biochar composite material was successfully synthesized. In addition, compared to the conventional ceria / biochar composite material prepared in Example 2 and the conventional biochar prepared in Example 4, the molecularly imprinted ceria / biochar composite material prepared in Example 1 and the imprinted biochar prepared in Example 3 exhibited stronger absorption peaks in the range of 4000-500 cm -1 For example, the molecularly imprinted ceria / biochar composite material prepared in Example 1 exhibited obvious absorption peaks at 1502 cm -1 and 1490 cm -1 , which were attributed to the stretching vibrations of -OH and C-O caused by methacrylic acid and the bending and stretching vibrations of C-O and C-C caused by UV irradiation of the biochar, respectively. These absorption peaks confirmed that the imprinted polymer had been successfully imprinted on the surface of the ceria / biochar composite material. At the same time, in the peak spectrum of the molecularly imprinted ceria / biochar composite material prepared in Example 5, an absorption peak at 2984 cm-1 A specific peak was observed at 2984 cm -1 The peak was significantly weaker, and it can be inferred that the change in the peak value was mainly due to the imprinting of p-chlorophenol template molecules onto the polymer matrix (biochar composite) and removal by acid washing. In addition, the Fourier transform infrared peak values of the molecularly imprinted cerium oxide / biochar composite prepared in Example 1 and the conventional cerium oxide / biochar composite prepared in Example 2 were similar, indicating that the p-chlorophenol template molecules in the molecularly imprinted cerium oxide / biochar composite prepared in Example 1 had been completely removed.

[0093] As Figure 3 XPS proved the successful preparation of the molecularly imprinted cerium oxide / biochar composite, as shown in the XPS spectrum of the molecularly imprinted cerium oxide / biochar composite prepared in Example 1, two new peaks appeared at 288.9 eV and 286.2 eV. These two peaks correspond to two unique chemical bonds in the imprinted polymer, representing O=C-OH of the functional monomer methacrylic acid and O-C-O specific functional groups caused by the change in the surface of the biochar under ultraviolet irradiation, which proves that the methacrylic acid successfully modified the surface of the cerium oxide / biochar.

[0094] From XPS and Fourier infrared spectroscopy, it can be seen that the surface of the cerium oxide / biochar composite creates an imprinting cavity that matches the size, shape, and charge of the p-chlorophenol.

[0095] The optical properties of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinting biochar prepared in Example 3, and the conventional biochar prepared in Example 4 were analyzed by ultraviolet-visible diffuse reflectance spectroscopy. As shown in FIG. 4(a), the absorbance of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 and the imprinting biochar prepared in Example 3 was stronger than that of the conventional cerium oxide / biochar composite material prepared in Example 2 and the conventional biochar prepared in Example 4, and the maximum absorption wavelength was red-shifted, which expanded the spectral response range. This is because the surface imprinting layer increased the specific surface area of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 and the imprinting biochar prepared in Example 3, and the introduction of organic groups on the imprinting surface enhanced the absorption of visible light and the light absorption intensity, and the addition of the imprinting polymer reduced the band gap width of cerium oxide, making the electrons more easily jump and more sensitive to visible light, as shown in FIG. 4(b). Compared with the imprinting biochar prepared in Example 3, the absorption intensity of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 was increased in the entire wavelength range, the ultraviolet-visible spectrum was red-shifted, and the utilization rate of visible light (380-450 nm) was significantly improved. This is because the addition of the photosensitive material cerium oxide on the surface of the biochar reduced the energy required for photon absorption and excitation. Therefore, the interaction and electronic coupling between cerium oxide and biochar were enhanced, resulting in the generation of more electron-hole pairs in the molecular imprinting cerium oxide / biochar composite material.

[0096] Examples 13-20

[0097] Catalyst performance test: 5 mg of catalyst and 10 mL of p-chlorophenol solution with an initial concentration of 10 mg / L were mixed, and the mixture was placed in a photocatalytic tube of a photochemical reaction instrument. A magnetic stirrer and a cooling water circulation were turned on, the reaction temperature was maintained at 25±0.2°C by circulating water outside the wall of the photochemical reaction instrument, and a dark reaction was performed for 90 min (to reach adsorption-desorption equilibrium) or a photocatalytic reaction was performed for 3 h. The removal efficiency of p-chlorophenol was tested after the reaction. The conditions for the photocatalytic reaction were as follows: a xenon lamp (xenon lamp power: 300 W, cutoff filter: 420 nm) was turned on.

[0098] According to the catalyst performance test, one of the molecular imprinting cerium oxide / biochar composite materials prepared in Examples 1 and 6-12 was used as a catalyst for the experiment.

[0099] The removal efficiency of p-chlorophenol obtained by the photocatalytic reaction was used as the photocatalytic degradation rate, and the removal efficiency of p-chlorophenol obtained after the dark reaction was used as the adsorption rate.

[0100] The adsorption rate and the photocatalytic degradation rate obtained by the dark reaction and the photocatalytic reaction are shown in Table 2.

[0101] Table 2

[0102]

[0103] As shown in Fig. 5(a), by comparing the results of the adsorption rate and the photocatalytic degradation rate of p-chlorophenol in water by Comparative Examples 13-20, it can be seen that when the mass ratio of cerium oxide / biochar composite material and imprint polymer exceeds 1:8, the adsorption rate decreases significantly, which is due to the excessive self-polymerization of imprint polymer, resulting in an excessively thick imprint layer covering the binding sites in the imprint cavity, thereby significantly inhibiting the effective adsorption of p-chlorophenol. In terms of photocatalytic degradation rate, the photocatalytic degradation rate is the highest when the mass ratio of cerium oxide / biochar composite material and imprint polymer is 1:8, indicating that an appropriate amount of imprint polymer enhances the chemical complexation near the photocatalytic sites on the surface of the cerium oxide / biochar composite material, and improves the contact probability between p-chlorophenol and the catalyst (molecularly imprinted cerium oxide / biochar composite material). However, further coating of this non-photosensitive polymer (imprint polymer) will block the photocatalytic sites on the surface of the cerium oxide / biochar composite material, hinder the penetration of light and reduce the surface photoexcitation. Similarly, when the content of imprint polymer is too low, the number of imprint cavities on the surface of the molecularly imprinted cerium oxide / biochar composite material will also decrease, hindering the selective adsorption of p-chlorophenol. Therefore, the ideal mass ratio of cerium oxide / biochar composite material and imprint polymer is 1:8, and the mass ratio of cerium oxide / biochar composite material and imprint polymer of 1:8 can not only maintain the excellent performance structure of cerium oxide and biochar, but also specifically recognize and adsorb p-chlorophenol in water, ultimately making the molecularly imprinted cerium oxide / biochar composite material have excellent photocatalytic activity.

[0104] Examples 21-22

[0105] Effect of catalyst dosage on removal of p-chlorophenol: catalyst and 10 mL of p-chlorophenol solution with an initial concentration of 10 mg / L were mixed, and then placed in a photocatalytic tube of a photochemical reaction instrument. A magnetic stirrer and a cooling water circulation were turned on. The reaction temperature was maintained at 25 ± 0.2 °C by circulating water outside the wall of the photochemical reaction instrument. After 90 min of dark reaction, adsorption-desorption equilibrium was reached. A light source was turned on for photocatalytic reaction for 3 h. After the reaction, the removal efficiency of p-chlorophenol was tested. The photocatalytic reaction conditions were as follows: a xenon lamp (300 W, with a 420 nm cutoff filter) was turned on. The catalyst dosage was 0.001, 0.002, 0.003, 0.005, 0.006, 0.008 or 0.01 g. The catalyst was the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 or the imprinted biochar prepared in Example 3.

[0106] The results of the removal of p-chlorophenol when the catalyst dosage was 0.005 g are shown in Table 3.

[0107] Table 3

[0108] Example Catalyst Removal rate Example 21 Example 1 90％ Example 22 Example 3 63％

[0109] As shown in FIG. 5(b) (in which the abscissa represents the concentration of the catalyst after the catalyst and the p-chlorophenol solution were mixed), when the dosage of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 and the imprinted biochar prepared in Example 3 was from 0.001 g to 0.005 g, the removal efficiency of p-chlorophenol showed an increasing trend. The removal efficiency of p-chlorophenol by the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 increased from 19% to 90%, and the removal efficiency of p-chlorophenol by the imprinted biochar prepared in Example 3 increased from 14% to 63%. This indicates that under certain conditions, the removal rate of p-chlorophenol is proportional to the catalyst dosage, which shows that an appropriate catalyst dosage can provide more reaction sites for the removal of pollutants. However, too much catalyst dosage will cause the pores to be blocked by organic matter, covering the surface catalytic sites, which will significantly reduce the removal rate of p-chlorophenol.

[0110] Example 23

[0111] Effect of pH on removal of p-chlorophenol: the method was basically the same as that of the aforementioned “Effect of catalyst dosage on removal of p-chlorophenol”, except that the catalyst dosage was 0.005 g, the catalyst was the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1, and the pH of the p-chlorophenol solution was one of 5, 6, 7, 8, 9, 10 and 11. The pH of the p-chlorophenol solution was adjusted with 0.1 mol / L hydrochloric acid or 0.1 mol / L sodium hydroxide aqueous solution, and a pH meter was used for determination.

[0112] As shown in Fig. 5(c), the pH value of the p-chlorophenol solution was increased from 5 to 11, and the removal efficiency of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 for p-chlorophenol increased first and then decreased. When the pH value of the p-chlorophenol solution was 9, the removal efficiency of p-chlorophenol was the highest, reaching 90%. This is because the pH value of the p-chlorophenol solution is similar to the isoelectric point of cerium dioxide (charge zero point = 8.1), and this similarity enables the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 to be more uniformly dispersed in the solution, thereby improving the degradation efficiency of p-chlorophenol through photodegradation. In addition, the weak alkaline environment stimulates the molecularly imprinted cerium oxide / biochar composite material to generate negatively charged oxygen-containing functional groups (such as carboxyl groups), thereby increasing the degradation effect of hydroxyl radicals on p-chlorophenol. The imprinting process has a significant impact on the surface structure of the cerium oxide / biochar composite material and the solid-liquid interface, thereby affecting the removal behavior of p-chlorophenol.

[0113] Examples 24-27

[0114] Method for determining the optimal adsorption time and photocatalytic time of the catalyst: 5 mg of the catalyst and 10 mL of a p-chlorophenol solution with an initial concentration of 10 mg / L of p-chlorophenol (pH = 9) were mixed, and then placed in the photocatalytic tube of a photochemical reaction instrument. The magnetic stirrer and cooling water circulation were turned on, and the reaction temperature was maintained at 25 ± 0.2°C by circulating water outside the wall of the photochemical reaction instrument. First, the reaction was carried out in complete darkness for 120 min, and the adsorption efficiency of p-chlorophenol was tested at 30 min, 60 min, 90 min, and 120 min in the dark, respectively. The adsorption equilibrium was almost reached at 90 min in the dark. Then, the photocatalytic reaction was carried out for 4 h, and the removal efficiency of p-chlorophenol was tested at 150 min, 180 min, 210 min, and 240 min during the photocatalytic reaction, respectively. The conditions of the photocatalytic reaction were as follows: the xenon lamp (xenon lamp power was 300 W, and the cutoff filter was 420 nm) was turned on. The catalyst was one of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, and the conventional biochar prepared in Example 4.

[0115] The adsorption efficiency at 90 min in the dark and the photocatalytic degradation rate at 180 min in the photocatalytic reaction of Examples 24-27 are shown in Table 4.

[0116] Table 4

[0117]

[0118] The results of the dark reaction are shown in Fig. 5(d) on the left side of "dark reaction". The adsorption-desorption equilibrium was reached at the 90th min (point -30 min in Fig. 5(d)) under dark conditions. The adsorption rate of p-chlorophenol by the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 was 47%, the adsorption rate of p-chlorophenol by the conventional cerium oxide / biochar composite material prepared in Example 2 was 35%, the adsorption rate of p-chlorophenol by the imprinted biochar prepared in Example 3 was 31%, and the adsorption rate of p-chlorophenol by the conventional biochar prepared in Example 4 was 22%. Compared with Example 2, the adsorption rate of Example 1 was increased, and compared with Example 4, the adsorption rate of Example 3 was increased, because there were many strong binding recognition sites of p-chlorophenol in the imprinted layer of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 and the imprinted biochar prepared in Example 3.

[0119] The photocatalytic reaction is shown in Fig. 5(d) on the right side of "photocatalysis". After 180 min of light irradiation under the light source, the removal rate of p-chlorophenol by the imprinted biochar prepared in Example 3 was increased to 63%, and the removal rate of p-chlorophenol by the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 was increased to 90%. The reason is that the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1 not only has an imprinted cavity for selectively adsorbing p-chlorophenol, but also has Ce elements on the surface, which increases the absorption of light and reduces the band gap (Fig. 4(a)-(b)) as a photosensitive material, thereby generating more electron-hole pairs.

[0120] Examples 28-31

[0121] Method for studying the photocatalytic degradation kinetics of p-chlorophenol in the process of removing p-chlorophenol by the catalyst: 5 mg of the catalyst and 10 mL of a p-chlorophenol solution with an initial concentration of 10 mg / L of p-chlorophenol (pH = 9) were mixed, and then placed into a photocatalytic tube of a photochemical reaction instrument. A magnetic stirrer and a cooling water circulation were turned on. The reaction temperature was maintained at 25 ± 0.2°C by circulating water outside the wall of the photochemical reaction instrument. First, the reaction was carried out for 90 min in complete darkness, and then photocatalytic reaction was carried out for 4 h. At the 0th min of the photocatalytic reaction, the removal efficiency of p-chlorophenol was tested every 30 min. The photocatalytic reaction conditions were as follows: a xenon lamp (xenon lamp power was 300 W, and the cutoff filter was 420 nm) was turned on. The catalyst was one of the molecularly imprinted cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, and the conventional biochar prepared in Example 4. According to the removal efficiency of p-chlorophenol obtained at different time points, Kt = Ln(C0 / C t ) at each time point was calculated, and the Ln(C0 / C t ) was linearly fitted by origin2021 to obtain R2 and slope K (first order degradation rate constant K). The more the slope K value tends to 1, the faster the kinetic rate, the faster the photo-reaction rate.

[0122] As shown in Figure 5 (e), the first order degradation rate constant K value of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 is 0.0930 min -1 , the first order degradation rate constant K value of the conventional cerium oxide / biochar composite material prepared in Example 2 is 0.0734 min -1 , the first order degradation rate constant K value of the imprinting biochar prepared in Example 3 is 0.0872 min -1 , the first order degradation rate constant K value of the conventional biochar prepared in Example 4 is 0.0567 min -1 , and the first order degradation rate constant K value of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 is obviously higher than that of Examples 2-4, because the surface imprinting cavity of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 matches the spatial structure of p-chlorophenol, thereby improving the adsorption rate, increasing the mass transfer rate, and increasing the rate of photocatalytic degradation.

[0123] The fitting degree R of the kinetic model to the data of Examples 28-31 2 (the closer to 1 indicates the better the fitting degree of the kinetic model to the data), as shown in Table 5.

[0124] Table 5

[0125] Example Catalyst [R 2 ]] Example 28 Example 1 0.99285 Example 29 Example 2 0.99183 Example 30 Example 3 0.99788 Example 31 Example 4 0.97305

[0126] Examples 32-35

[0127] The selective experiment method of the catalyst: 5 mg of the catalyst and 10 mL of the pollutant solution (pH = 9) were put into a photocatalytic tube of a photochemical reaction instrument, a magnetic stirrer and a cooling water circulation were turned on, the reaction temperature was maintained at 25 ± 0.2 ℃ by circulating water outside the wall of the photochemical reaction instrument, and then dark reaction was carried out for 90 min, followed by photocatalytic reaction for 180 min, wherein the photocatalytic reaction conditions were as follows: a xenon lamp (300 W of xenon lamp power and 420 nm of cut-off filter) was turned on, the pollutant solution was a water solution of a mixture of p-chlorophenol and a pollutant, the concentrations of p-chlorophenol and the pollutant in the pollutant solution were 10 mg / L respectively, the pollutant was dichlorophenol or enrofloxacin, and the catalyst was one of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3 and the conventional biochar prepared in Example 4. After the photocatalytic reaction, the removal efficiencies of p-chlorophenol and the pollutant were tested, and when the pollutant was dichlorophenol, the removal efficiencies of p-chlorophenol and the pollutant were as shown in FIG. 6(a), and when the pollutant was enrofloxacin, the removal efficiencies of p-chlorophenol and the pollutant were as shown in FIG. 6(c). As can be seen from the figures, the removal rates of enrofloxacin of Example 1 and Example 2 are not much different, the removal rates of 2-chlorophenol of Example 1 and Example 2 are not much different, the removal rate of enrofloxacin is maintained at 31-32%, and the removal rate of 2-chlorophenol is maintained at 36-37%, which indicates that the imprinting cavity has a smaller effect on the removal of enrofloxacin and 2-chlorophenol, but the removal rate of p-chlorophenol of Example 1 is as high as 90%, which is 2.90 times that of enrofloxacin and 2.43 times that of 2-chlorophenol, which indicates that the imprinting cavity in the molecular imprinting cerium oxide / biochar composite material obtained in Example 1 has only recognition sites for p-chlorophenol and has a strong selectivity for p-chlorophenol. In addition, these imprinting cavities are rich in organic chemical groups such as O=C-OH in methacrylic acid, and physical cross-linking will form chemical bonds between long polymer chains or form strong physical binding points, thereby enhancing the chemical adsorption effect. Figure 3

[0128] The catalysts corresponding to Examples 32-35 are shown in Table 6.

[0129] Table 6

[0130]

[0131] Examples 36-39

[0132] ​The anti-interference experiment method of the catalyst: 5 mg of the catalyst, 0.1 mg of the organic matter, and 10 mL of a p-chlorophenol solution with an initial concentration of 10 mg / L were mixed uniformly and placed in a photocatalytic tube of a photochemical reaction instrument. A magnetic stirrer and a cooling water circulation were turned on. The reaction temperature was maintained at 25±0.2°C by circulating water outside the wall of the photochemical reaction instrument. A dark reaction was performed for 90 min. After reaching the adsorption / desorption equilibrium, a photocatalytic reaction was immediately performed for 3 h under light. The removal efficiency of p-chlorophenol was tested after the reaction. The photocatalytic reaction conditions were as follows: a xenon lamp (xenon lamp power: 300 W, and a cutoff filter: 420 nm) was turned on. The organic matter was one of humic acid, fulvic acid, trypsin, and glucose (“humic acid”, “fulvic acid”, “trypsin”, and “glucose” in FIG. 6(b)). The catalyst was one of the molecular imprinting cerium oxide / biochar composite material prepared in Example 1, the conventional cerium oxide / biochar composite material prepared in Example 2, the imprinted biochar prepared in Example 3, and the conventional biochar prepared in Example 4.

[0133] The blank experiment group: The method was basically the same as the anti-interference experiment method of the catalyst, except that no organic matter was contained (“control” in FIG. 6(b)).

[0134] FIG. 6(b) shows that, under the adsorption equilibrium state, the removal efficiency of p-chlorophenol in Example 37 (Example 2 in FIG. 6(b)) decreased obviously in the presence of organic matters such as fulvic acid, from 56% (“control” in FIG. 6(b)) to 18% (“fulvic acid” in FIG. 6(b)). This decrease was attributed to the fact that the adsorption sites on the surface of the conventional cerium oxide / biochar composite material prepared in Example 2 were occupied by competitive compounds such as fulvic acid, humic acid, trypsin, and glucose, resulting in a decrease in the adsorption of p-chlorophenol. However, Example 36 (Example 1 in FIG. 6(b)) was less affected by the background environment. The removal efficiency of “glucose” in Example 36 (Example 1 in FIG. 6(b)) was almost unaffected, and “humic acid” (removal efficiency: 88%) and “trypsin” (removal efficiency: 83%) also had only a slight inhibitory effect. Because the molecular imprinting cerium oxide / biochar composite material prepared in Example 1 has imprinting polymers on the surface, specific adsorption sites are provided. These adsorption sites selectively adsorb p-chlorophenol, reducing the interference of other background components and improving the efficiency of the photocatalytic reaction of p-chlorophenol.

[0135] The catalysts corresponding to Examples 36-39 are shown in Table 7.

[0136] Table 7

[0137] Example Catalyst Example 36 Example 1 Example 37 Example 2 Example 38 Example 3 Example 39 Example 4

[0138] The above has made the exemplary description to the present application, should indicate that, in not departing from the core of the present application, any simple change, modification or other field technicians can not spend the equivalent replacement of creative labor falls into the protection scope of the present application.

Claims

1. A method for preparing a molecularly imprinted cerium oxide / biochar composite material, characterized in that, Includes the following steps: S1, mix the cerium oxide / biochar composite material and solvent, and sonicate to obtain a first solution. The mass fraction of the cerium oxide / biochar composite material and the volume fraction of the solvent are 1:(100~130). The mass fraction is in g and the volume fraction is in mL. The cerium oxide / biochar composite material is biochar and cerium oxide supported on the biochar. S2, At room temperature, the first solution and the imprinted polymer are mixed and stirred to obtain a first mixture. By mass parts, the ratio of the cerium oxide / biochar composite material to the imprinted polymer is 1:(0.1~12). The imprinted polymer is a mixture of template molecules and functional monomers. The template molecule is p-chlorophenol, and the functional monomer is methacrylic acid. By molar parts, the ratio of the template molecule to the functional monomer is 1:(2~8). S3, the first mixture is purged with N2 to remove oxygen, and polymerized under sealed conditions and ultraviolet radiation for 12-24 hours to obtain the second mixture. The second mixture is centrifuged, washed with detergent until template molecules are undetectable, washed to remove detergent, and dried to obtain molecularly imprinted cerium oxide / biochar composite material.

2. The preparation method according to claim 1, characterized in that, The method for preparing the cerium oxide / biochar composite material is as follows: Step 1: Mix biochar, water, and anhydrous ethanol, and sonicate until homogeneous to obtain solution A. Mix cerium salt and water, and stir until homogeneous to obtain solution B. The ratio of the mass fraction of biochar, the volume fraction of water, and the volume fraction of anhydrous ethanol in solution A is (1.5~2):20:20, and the ratio of the mass fraction of cerium salt to the volume fraction of water in solution B is 1:(4~6). The units of mass fraction are g, and the units of volume fraction are mL. Step 2: Mix the A solution and the B solution, stir until uniform, hydrothermally heat at 140~180℃ for 10~12 h, cool to room temperature, wash, dry, and calcine at 500~600℃ for 1~3 h under N2 atmosphere to obtain cerium oxide / biochar composite material, wherein, by mass fraction, the ratio of biochar in the A solution to cerium salt in the B solution is 1:(2~4).

3. The preparation method according to claim 1, characterized in that, In S3, the polymerization temperature is 50~80°C, and the polymerization is carried out under continuous stirring conditions.

4. The preparation method according to claim 1, characterized in that, In S3, the power of the ultraviolet radiation is 8~15W.

5. The preparation method according to claim 1, characterized in that, In S1, the solvent is acetonitrile.

6. The preparation method according to claim 1, characterized in that, In S1, the ultrasound time is 20-30 min; in S2, the stirring time is 15-30 min.

7. The preparation method according to claim 2, characterized in that, In step 1, the cerium salt is cerium nitrate hexahydrate.

8. The preparation method according to claim 2, characterized in that, In step 1, the method for obtaining biochar is as follows: the biochar raw material is dried at 60~80℃ for 24~36 h, then pyrolyzed at 500~600℃ under N2 atmosphere with limited oxygen for 1~3 h, and cooled to room temperature to obtain biochar.

9. The preparation method according to claim 8, characterized in that, The biochar raw materials are one or more of straw, sawdust, animal manure and sludge.

10. The application of the molecularly imprinted cerium oxide / biochar composite material obtained by any one of claims 1 to 9 as a catalyst in improving the removal efficiency of p-chlorophenol.

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