CN116532123A - Magnetic biochar-based bismuth tungstate composite photocatalyst and preparation method thereof - Google Patents
Magnetic biochar-based bismuth tungstate composite photocatalyst and preparation method thereof Download PDFInfo
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- CN116532123A CN116532123A CN202310519596.5A CN202310519596A CN116532123A CN 116532123 A CN116532123 A CN 116532123A CN 202310519596 A CN202310519596 A CN 202310519596A CN 116532123 A CN116532123 A CN 116532123A
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- biochar
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- 229910052797 bismuth Inorganic materials 0.000 title claims abstract description 115
- 239000011941 photocatalyst Substances 0.000 title claims abstract description 104
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 title claims abstract description 101
- PBYZMCDFOULPGH-UHFFFAOYSA-N tungstate Chemical compound [O-][W]([O-])(=O)=O PBYZMCDFOULPGH-UHFFFAOYSA-N 0.000 title claims abstract description 98
- 239000002131 composite material Substances 0.000 title claims abstract description 93
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000000843 powder Substances 0.000 claims abstract description 30
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 30
- 229910017052 cobalt Inorganic materials 0.000 claims abstract description 29
- 239000010941 cobalt Substances 0.000 claims abstract description 29
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims abstract description 29
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims abstract description 14
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 claims abstract description 7
- 229910001981 cobalt nitrate Inorganic materials 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- RXPAJWPEYBDXOG-UHFFFAOYSA-N hydron;methyl 4-methoxypyridine-2-carboxylate;chloride Chemical compound Cl.COC(=O)C1=CC(OC)=CC=N1 RXPAJWPEYBDXOG-UHFFFAOYSA-N 0.000 claims abstract description 7
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 7
- XMVONEAAOPAGAO-UHFFFAOYSA-N sodium tungstate Chemical compound [Na+].[Na+].[O-][W]([O-])(=O)=O XMVONEAAOPAGAO-UHFFFAOYSA-N 0.000 claims abstract description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 28
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- 239000000126 substance Substances 0.000 abstract description 6
- MYSWGUAQZAJSOK-UHFFFAOYSA-N ciprofloxacin Chemical compound C12=CC(N3CCNCC3)=C(F)C=C2C(=O)C(C(=O)O)=CN1C1CC1 MYSWGUAQZAJSOK-UHFFFAOYSA-N 0.000 description 42
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- OFVLGDICTFRJMM-WESIUVDSSA-N tetracycline Chemical compound C1=CC=C2[C@](O)(C)[C@H]3C[C@H]4[C@H](N(C)C)C(O)=C(C(N)=O)C(=O)[C@@]4(O)C(O)=C3C(=O)C2=C1O OFVLGDICTFRJMM-WESIUVDSSA-N 0.000 description 15
- -1 bismuth tungstate series Chemical class 0.000 description 14
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- NQTSTBMCCAVWOS-UHFFFAOYSA-N 1-dimethoxyphosphoryl-3-phenoxypropan-2-one Chemical compound COP(=O)(OC)CC(=O)COC1=CC=CC=C1 NQTSTBMCCAVWOS-UHFFFAOYSA-N 0.000 description 2
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Classifications
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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
- B01J23/84—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 arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/85—Chromium, molybdenum or tungsten
- B01J23/888—Tungsten
-
- 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
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
-
- 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
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
-
- 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
- B01J37/08—Heat treatment
- B01J37/10—Heat treatment in the presence of water, e.g. steam
-
- 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
- B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Thermal Sciences (AREA)
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Abstract
The embodiment of the specification discloses a magnetic biochar-based bismuth tungstate composite photocatalyst and a preparation method thereof. The scheme may include: in a tube furnace at N 2 Under the protection, heating the crop stem powder to prepare biochar; preparing cobalt ferrite powder by using cobalt nitrate and ferric nitrate; bismuth nitrate and sodium tungstate are used for preparing bismuth tungstate solution; and adding the biochar and the cobalt ferrite powder into the bismuth tungstate solution, and preparing the magnetic biochar-based bismuth tungstate composite photocatalyst by a hydrothermal method. Based on the scheme, by introducing low-cost biochar and magnetic substances into the photocatalyst, on one hand, the adsorptivity and photocatalytic efficiency of the photocatalyst can be improved, and the removal efficiency of the photocatalyst to pollutants can be improved, and on the other hand, the recovery of the photocatalyst can be improvedEfficiency is improved.
Description
Technical Field
The application relates to the technical field of photocatalysis, in particular to a composite photocatalyst and a preparation method thereof, and more particularly relates to a magnetic biochar-based bismuth tungstate composite photocatalyst and a preparation method and application thereof.
Background
Antibiotics, also called antibiotics, can be extracted from a microbial culture solution or synthesized artificially and chemically, and are chemical substances capable of interfering and inhibiting growth, development and proliferation of microorganisms and other biological cells. Antibiotics have been the most effective antibacterial agents through decades of development, and are widely used in the aquaculture, pharmaceutical and medical industries. In recent years, antibiotics have been found to enter the aqueous environment by a variety of routes, causing varying degrees of pollution to groundwater and surface water. Bacteria can develop resistance when antibiotics accumulate in the water environment for a long period of time, so that the dosage of the antibiotics needs to be increased, and the malignant circulation is caused. Moreover, the existence of antibiotics greatly influences the aquatic ecosystem, and a phenomenon that a large number of aquatic animals die easily occurs. Meanwhile, antibiotics in water environment can enter human body along with food chain, and have toxic and side effects on human health, such as damage to intestinal flora, damage to liver function, and decrease of human immunity. If antibiotics accumulated in the water environment are not treated in time, the risk to human health and ecological environment is greatly increased.
In order to prevent the contamination surface from being diffused due to the residue of antibiotics in the water environment, so far, researchers have studied various methods for removing antibiotics in the water environment, mainly including a biological treatment method (activated sludge method), a physical method (adsorption method) and a chemical oxidation method (Fenton oxidation method, photocatalytic oxidation method). The methods have problems of different degrees, such as incomplete degradation of antibiotics by a physical method; biological methods have long antibiotic removal cycles and have great environmental requirements. The photocatalysis technology is one of effective methods for degrading antibiotics in water environment by virtue of the environmental protection and high efficiency. The photocatalytic oxidation method can efficiently degrade organic pollutants, reduce heavy metal ions and purify air, and is remarkable in a plurality of pollutant removal technologies.
Disclosure of Invention
The embodiment of the specification provides a magnetic biochar-based bismuth tungstate composite photocatalyst and a preparation method thereof, so as to solve the problems of low catalytic efficiency and difficult recovery of the existing photocatalyst.
In order to solve the above technical problems, the embodiments of the present specification are implemented as follows:
the magnetic biochar-based bismuth tungstate composite photocatalyst provided in the embodiments of the present specification may include: a biochar carrier; cobalt ferrite; is loaded on the biochar carrier; bismuth tungstate; is loaded on the biochar carrier.
Optionally, in the magnetic biochar-based bismuth tungstate composite photocatalyst, the mass of the biochar carrier may be 3% of the mass of the bismuth tungstate; the mass of the cobalt ferrite can be 3-10% of the mass of the bismuth tungstate; preferably, the mass of the cobalt ferrite may be 5% of the mass of the bismuth tungstate.
The preparation method of the magnetic biochar-based bismuth tungstate composite photocatalyst provided by the embodiment of the specification can comprise the following steps: in a tube furnace at N 2 Under the protection, heating the crop stem powder to prepare biochar; preparing cobalt ferrite powder by using cobalt nitrate and ferric nitrate; bismuth nitrate and sodium tungstate are used for preparing bismuth tungstate solution; and adding the biochar and the cobalt ferrite powder into the bismuth tungstate solution, and preparing the magnetic biochar-based bismuth tungstate composite photocatalyst by a hydrothermal method.
Optionally, the step of preparing biochar may specifically include: drying crop stems and grinding the crop stems into powder to obtain corn stem powder; placing crop stalk powder in a tube furnace, and adding N 2 Under the protection, the temperature is 5-10 ℃ for min -1 Heating to 790-810 ℃ to obtain a biochar crude product; for the saidAnd washing and drying the biochar crude product to obtain the biochar product.
Optionally, washing and drying the biochar crude product to obtain a biochar product, which specifically comprises the following steps: washing silicate in the biochar crude product by using sodium hydroxide solution; washing out metal impurities in the biochar crude product by using hydrochloric acid solution; repeatedly washing the biochar crude product to be neutral by using deionized water; and (5) drying in vacuum to obtain the biochar.
Optionally, the step of preparing the cobalt ferrite powder may specifically include: fe (NO) 3 ) 3 ·9H 2 O is dissolved in water to obtain ferric nitrate solution; co (NO) 3 ) 2 ·6H 2 O is dissolved in water to obtain cobalt nitrate solution; slowly pouring the cobalt nitrate solution into the ferric nitrate solution, adjusting the pH value to 11-13 (for example, the pH value can be adjusted to 12), and stirring to obtain a pre-reaction solution; placing the pre-reaction solution in a high-pressure reaction kettle, and reacting at a first temperature for a first time period (specifically, the first temperature is 160-200 ℃, the first time period is 11-13 hours, and optionally, the reaction is carried out at 180 ℃ for 12 hours) to obtain a post-reaction solution; and drying and grinding the solid in the solution after the reaction to obtain cobalt ferrite powder.
Optionally, the step of preparing the bismuth tungstate solution may specifically include: bi (NO) 3 ) 3 ·5H 2 O is dissolved in nitric acid solution to obtain bismuth nitrate solution; na is mixed with 2 WO 4 ·2H 2 O is dissolved in water, and sodium hydroxide solution is added to obtain sodium tungstate solution; while stirring, a sodium tungstate solution was slowly added dropwise to the bismuth nitrate solution to obtain a bismuth tungstate solution containing a white precipitate.
Alternatively, the mass of biochar added to the bismuth tungstate solution may be 3% of the mass of bismuth tungstate in the bismuth tungstate solution; the mass of the cobalt ferrite powder added into the bismuth tungstate solution can be 3-10% of the mass of the bismuth tungstate in the bismuth tungstate solution; preferably, the mass of the cobalt ferrite powder added to the bismuth tungstate solution may be 5% of the mass of bismuth tungstate in the bismuth tungstate solution.
Optionally, the step of preparing the magnetic biochar-based bismuth tungstate composite photocatalyst by a hydrothermal method specifically comprises the following steps: adding a proper amount of biochar and a proper amount of cobalt ferrite powder into the bismuth tungstate solution, and stirring vigorously to obtain a turbid liquid; placing the turbid liquid in an autoclave, and reacting at a second temperature for a second time period (specifically, the second temperature is 160 ℃ to 200 ℃, the second time period is 5 hours to 7 hours, and optionally, the turbid liquid is reacted at 180 ℃ for 6 hours) to obtain a compound photocatalyst product solution; and removing the supernatant from the composite photocatalyst product solution, and washing and drying the solution to obtain the magnetic biochar-based bismuth tungstate composite photocatalyst.
One embodiment of the present disclosure can achieve at least the following advantages: bismuth-based photocatalyst Bi is prepared by using biochar as carrier 2 WO 6 With cobalt ferrite (CoFe) 2 O 4 ) The magnetic biochar-based bismuth tungstate composite photocatalyst is prepared as a load material, so that the removal efficiency of the photocatalyst to pollutants can be improved, and the recovery efficiency of the powder catalyst can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present description or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present application, and that other drawings may be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a scanning electron microscope (Scanning Electronic Microscopy, SEM) image of a magnetic biochar-based bismuth tungstate composite photocatalyst prepared in an example of the present specification;
FIG. 2 is a Mapping energy spectrum of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the embodiment of the specification;
FIG. 3 is an energy scattering spectrum (Energy Dispersive Spectroscopy, EDS) spectrum of a magnetic biochar-based bismuth tungstate composite photocatalyst prepared in an example of the present specification;
FIG. 4 is an X-ray diffraction (XRD) pattern of a magnetic biochar-based bismuth tungstate composite photocatalyst prepared in an example of the present specification;
FIG. 5 is a transmission electron microscope image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification; wherein a is a common transmission electron microscope (transmission electron microscope, TEM) image, b is a selected area electron diffraction (SelectedArea Electron Diffraction, SAED) image, and c is a High Resolution Transmission Electron Microscope (HRTEM) image;
FIG. 6 is a Fourier infrared transform (Fourier Transform Infra-Red, FTIR) spectrum of a magnetic biochar-based bismuth tungstate composite photocatalyst prepared in an example of the present specification;
FIG. 7 is an Ultraviolet-visible spectrum (Ultraviolet-visible spectroscopy, uv-Vis) diagram of a magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate prepared in an example of the specification;
FIG. 8 shows band gap energy spectra of a magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate prepared in an embodiment of the present specification;
FIG. 9 is a nitrogen adsorption-desorption isotherm of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification and bismuth tungstate;
FIG. 10 is a hysteresis loop diagram of a magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification;
FIG. 11 shows the adsorption performance curves of magnetic biochar-based bismuth tungstate series composite photocatalysts prepared in the examples of the present specification on Ciprofloxacin (CIP);
FIG. 12 is a graph showing the adsorption performance of the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the example of the present specification to Tetracycline (TC);
FIG. 13 shows photocatalytic degradation curves of magnetic biochar-based bismuth tungstate series composite photocatalysts prepared in the examples of the present specification for CIP (CIP) in Ciprofloxacin and Tetracycline (TC) binary systems;
FIG. 14 is a graph showing photocatalytic degradation of magnetic biochar-based bismuth tungstate series composite photocatalysts prepared in the examples of the present specification against TC in Ciprofloxacin (CIP) and Tetracycline (TC) binary systems.
Detailed Description
The photocatalytic oxidation method converts light energy into chemical energy by photoexcitation to produce OH and O in the catalyst 2 -degrading organic contaminants. The adsorption-degradation efficiency of different photocatalysts for antibiotics is not the same. Bi (Bi) 2 WO 6 As one of the numerous photocatalysts, bi is caused by the special layered structure and energy band position thereof 2 WO 6 The catalyst has good visible light response capability, and the energy band structure is easier to adjust compared with other catalysts, so that the catalyst plays a better role in the reaction process of photocatalytic degradation of pollutants.
However, a single Bi 2 WO 6 The semiconductor catalyst still has the bottleneck problems of low visible light absorption, wide forbidden bandwidth, high electron hole repetition rate and the like, so that the pollutant treatment effect is not ideal, and the photocatalytic activity is poor. Therefore, bi needs to be improved 2 WO 6 Photocatalytic activity in the visible range. For example, bi can be modified by adopting technical strategies such as heterostructures construction, ion doping, surface modification, and defect engineering 2 WO 6 The photocatalytic material is modified and regulated to improve the absorption range of visible light, so that the photocatalytic activity of the bismuth-based semiconductor catalyst is further enhanced.
At the same time, a single Bi 2 WO 6 The adsorption effect on pollutants is also to be improved. Therefore, a porous material having high adsorptivity was selected as Bi 2 WO 6 The carrier of the catalyst can better realize solid-liquid separation while improving the adsorption effect of the photocatalyst. However, in the conventional studies, the recovery of the powdery catalyst often requires complicated steps such as centrifugation and filtration. In addition, the defect of secondary pollution caused by easy loss exists in practical application.
In view of this, in one or more embodiments of the present description, adsorption methods are used in combination with photocatalytic techniques in order to increase the efficiency of photocatalyst removal of contaminants. And magnetic substances are introduced, so that the recovery efficiency of the powder catalyst can be effectively improved under the action of an external magnetic field.
In one or more embodiments of the present disclosure, a biochar material having a large specific surface area and a rich functional group structure is introduced into a composite photocatalyst. On one hand, the biochar material with a porous structure can be used as a good support for the immobilization of the photocatalytic material, and Bi 2 WO 6 The photocatalyst can be deposited in the pores of the photocatalyst to avoid agglomeration; on the other hand, the functional groups on the surface of the biochar can accelerate the adsorption of the composite photocatalyst on pollutants, so that the composite photocatalyst can rapidly react with photo-generated electrons and holes, and the photocatalysis efficiency of a reaction system is improved.
In one or more embodiments of the present description, ferrite having good electromagnetic properties, photo-responsivity, and easy recovery, etc. characteristics are introduced into the composite photocatalyst. Specifically, cobalt ferrite (CoFe) with (1.9 eV 2 O 4 ) The catalyst has magnetism and can improve the photocatalysis performance of the catalyst to a certain extent due to the narrow band gap.
In one or more embodiments of the present disclosure, a magnetic biochar-based bismuth tungstate composite photocatalytic material is successfully prepared for the first time by a hydrothermal method, and characterization analysis and antibiotic degradation effect evaluation are performed on the prepared magnetic biochar-based bismuth tungstate composite photocatalyst. In one or more embodiments of the present disclosure, the carrier Biochar (BC) is selected to be a large amount of storage as agricultural waste biomass in northeast China, and is relatively inexpensive, with the advantage of cost-effective waste utilization. The selected supporting material is bismuth photocatalyst Bi 2 WO 6 With cobalt ferrite (CoFe) 2 O 4 ) These materials provide a green and economical solution for achieving the combination of agricultural waste biomass and photocatalyst, and for improving the efficiency of the photocatalyst in practical applications.
For the purposes of making the objects, technical solutions and advantages of one or more embodiments of the present specification more clear, the technical solutions of one or more embodiments of the present specification will be clearly and completely described below in connection with specific embodiments of the present specification and corresponding drawings. It will be apparent that the described embodiments are only some, but not all, of the embodiments of the present specification. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without undue burden, are intended to be within the scope of one or more embodiments herein.
Example 1: preparation method of magnetic biochar-based bismuth tungstate composite photocatalyst
1.1 preparation of Biochar (Biochar, BC)
In the embodiment of the specification, corn stalks which are widely produced in the north of China are used as raw materials to prepare the biochar. Optionally, the raw materials for preparing the biochar can also comprise crop straws such as wheat, rice, potatoes, rape, cotton, sugarcane and the like.
Pretreatment: corn stalks were defoliated, root-removed, washed several times (e.g., 3 times) with deionized water and dried in an oven at 80 ℃ to constant weight. The corn stalks were then ground to a powder and sieved through a 60 mesh screen.
1g of corn stalk powder can be transferred to a crucible and then in a tube furnace, under N 2 Heating under protection, in particular at 5℃min -1 The temperature rise rate of (2) was increased to 800 ℃ (temperature rise process 2 h). After completion of the heating, the prepared samples were washed with 1M NaOH and 2M HCl each for 2 hours to remove silicate and metal impurities, respectively. The sample was then repeatedly washed with deionized water until neutral. Finally, the resultant was dried in a vacuum oven at 60℃for 8 hours to give a biochar product designated BC.
1.2 cobalt ferrite (CoFe) 2 O 4 ) Is prepared from
Weigh 5mmol Fe (NO) 3 ) 3 ·9H 2 O was dissolved in 30mL of water and designated A;2.5mmol Co (NO) 3 ) 2 ·6H 2 O was dissolved in 10mL of water and designated B. After dissolution B was slowly poured into a, ph=12 was adjusted with NaOH (2 mol/L) and stirred for a further 5h. Will be put onThe solution was transferred to a 100mL autoclave and heated at 180℃for 12h. Cooling, alternately and repeatedly washing with absolute ethanol and deionized water, suction filtering, drying the obtained sample in oven at 60deg.C for 4 hr, and grinding with agate mortar to obtain cobalt ferrite powder, denoted as CoFe 2 O 4 。
1.3 magnetic biochar-based bismuth tungstate composite photocatalyst (CoFe 2 O 4 /BC/Bi 2 WO 6 ) Is prepared from
2mmol Bi (NO) 3 ) 3 ·5H 2 O was dissolved in 40mL (0.3 mol/L) HNO 3 In (2), marked as C;1mmol Na 2 WO 4 ·2H 2 O was dissolved in 20mL of deionized water, followed by the addition of 20mL (0.2 mol/L) NaOH, designated as D. After both were completely dissolved, D was slowly added dropwise to C under the influence of magnetic stirring, and it was observed that the mixed solution immediately produced a white precipitate, which was stirred for 1h in this state.
Then taking a proper amount of BC and CoFe 2 O 4 Adding the mixture solution to make BC occupy Bi 2 WO 6 3% by mass, coFe 2 O 4 Bi is occupied by 2 WO 6 5% of the mass, and vigorously stirred for 5 hours. Finally, the turbid liquid was transferred to a 100mL autoclave and kept at 180 ℃ for 6h. After cooling to room temperature, the supernatant was discarded, washed three times and dried at 65 ℃ for 6 hours. The collected samples were 5CFO/3BC/BWO. In 5CFO/3BC/BWO, CFO means CoFe 2 O 4 BWO represents Bi 2 WO 6 5CFO means that the mass of CFO is 5% of the mass of BWO, and 3BC means that the mass of BC is 3% of the mass of BWO.
In other embodiments, the BC to Bi content added to the mixed solution may be adjusted 2 WO 6 Mass ratio and CoFe added to the mixed solution 2 O 4 Bi is occupied by 2 WO 6 The mass ratio is that, thus, a series of magnetic biochar-based bismuth tungstate composite photocatalysts with different load ratios, such as 5CFO/4BC/BWO, 3CFO/3BC/BWO, 7CFO/3BC/BWO, 10CFO/3BC/BWO, etc., can be obtained.
1.4 bismuth tungstate (Bi) 2 WO 6 ) Is prepared from
For comparative evaluation of the performance of the composite photocatalyst prepared in the examples of the present specification, pure Bi was prepared 2 WO 6 (BWO) as a reference.
2mmol Bi (NO) 3 ) 3 ·5H 2 O was dissolved in 40mL (0.3 mol/L) HNO 3 In (2), denoted as E;1mmol Na 2 WO 4 ·2H 2 O was dissolved in 20mL of deionized water, followed by the addition of 20mL (0.2 mol/L) NaOH, designated as F. After both were completely dissolved, F was slowly dropped into E under the action of magnetic stirring, and it was observed that the mixed solution immediately produced a white precipitate, which was stirred for 1h in this state.
The turbid liquid was transferred to a 100mL autoclave and kept at 180℃for 6h. After cooling to room temperature, the supernatant was discarded, washed three times and dried at 65 ℃ for 6 hours. The collected sample is Bi 2 WO 6 May be denoted BWO.
Example 2: product characterization of magnetic biochar-based bismuth tungstate composite photocatalyst
In one or more embodiments of the present disclosure, the 5CFO/3BC/BWO sample is subjected to characterization analysis of structure, crystal form, morphology, purity, element distribution and valence state by using methods such as X-ray diffraction (XRD), scanning Electron Microscope (SEM), transmission electron microscope (TEM, HRTEM), energy spectrum (EDX), X-ray/ultraviolet electron spectroscopy (XPS/UPS), etc., to obtain crystal face exposure information, and the structural form of the 5CFO/3BC/BWO is analyzed; observing the organic functional group composition on the surface of the catalyst by utilizing Fourier infrared spectroscopy (FT-IR), and analyzing the optical performance change of the catalyst according to the change of the absorption band edge and the absorption peak intensity of the catalyst sample in the ultraviolet and visible light regions and the like; the pore size structure of 5CFO/3BC/BWO was analyzed using a specific surface area analyzer (BET).
Fig. 1 shows a scanning electron microscope (Scanning Electronic Microscopy, SEM) image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification.
In FIG. 1, a is Bi prepared in the examples of the present specification 2 WO 6 Exhibiting a uniform flower-like nano layered structure at 10 μm；Bi 2 WO 6 Is of a layered structure such that Bi 2 WO 6 Has larger specific surface area.
In fig. 1, b is Biochar (BC) prepared in the examples of the present specification; the microstructure of Biochar (BC) is a rod-like structure with multiple pores.
In FIG. 1, c is CoFe prepared in the examples of the present specification 2 O 4 Is a spherical particle. Wherein due to CoFe 2 O 4 The magnetic properties of (2) are such that a slight agglomeration is accompanied in the figure.
In FIG. 1, d is the microscopic morphology of 5CFO/3BC/BWO prepared in the examples herein; wherein BC is used as a carrier, and CoFe is prepared by a hydrothermal method 2 O 4 And Bi (Bi) 2 WO 6 And (3) loading the catalyst on the BC to roughen the surface of the BC after compounding to prepare the 5CFO/3BC/BWO composite photocatalyst.
Fig. 2 shows Mapping energy spectrum of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the specification.
In fig. 2, a to f sequentially represent distribution diagrams of Bi, C, O, W, fe, co six elements in the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification.
In fig. 2, a to f show a uniform distribution of six elements, which ensures sufficient contact with the contaminants in order to degrade the contaminants sufficiently.
Fig. 3 shows an energy scattering spectrum (Energy Dispersive Spectroscopy, EDS) spectrum of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification.
Fig. 4 shows an X-ray diffraction (XRD) pattern of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification.
In FIG. 4, coFe 2 O 4 More pronounced characteristic peaks appear at 2θ=30.15 °, 35.4 °, 43.1 °, 53.6 °, 57.0 °, 62.6 ° and 74.2 °, with CoFe 2 O 4 The lattice planes (220), (311), (400), (422), (511), (440) and (533) of (JCPDS No. 221086) are substantially uniform.
Bi 2 WO 6 Characteristic peaks appear at 2θ=28.3 °, 32.9 °, 47.1 °, 56.0 °, 58.5 °, 68.8 °, 75.9 °, and 78.5 °, which are both similar to orthorhombic Bi 2 WO 6 The lattice planes (131), (200), (002), (202), (133), (262), (193) and (204) of (JCPDS No. 39-0256) have good correspondence.
5CFO/3BC/BWO composite catalyst and Bi 2 WO 6 And CoFe 2 O 4 The positions of the characteristic peaks are in one-to-one correspondence, due to CoFe 2 O 4 The addition amount of (C) is only 5%, so that CoFe in the 5CFO/3BC/BWO composite catalyst 2 O 4 The characteristic peaks of (2) are not apparent.
Fig. 5 shows a transmission electron microscope image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification.
In fig. 5, a is a TEM image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification. Wherein the thinner edge is the prepared nano flower-shaped Bi 2 WO 6 While a small amount of shading may be the magnetic material CoFe in 5CFO/3BC/BWO 2 O 4 Agglomeration phenomenon of (2).
In fig. 5, b is a SAED image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification. The diffraction light spot is annular, which indicates that the prepared composite catalyst belongs to a polycrystalline structure.
In fig. 5, c is an HRTEM image of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification. Wherein, bi is respectively corresponding to the positions of d=0.31 nm, d=0.16 nm, d=0.20 nm and d=0.25 nm of the interplanar spacing 2 WO 6 (131) and (133) planes and CoFe 2 O 4 A (400) crystal plane and a (311) crystal plane.
Fig. 6 shows fourier infrared transform (Fourier Transform Infra-Red, FTIR) spectra of the magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate and cobalt ferrite prepared in the examples of the present specification.
In FIG. 6, bi is sequentially present from top to bottom 2 WO 6 5CFO/3BC/BWO and CoFe 2 O 4 Is a FTIR spectrum of (C).
In FIG. 6, coFe 2 O 4 At 410cm -1 And 560cm -1 The characteristic peaks are shown in the positions, respectively belonging to CoFe 2 O 4 The stretching vibration peaks of Co-O and Fe-O in the magnetic biochar-based bismuth tungstate composite photocatalyst prove that CoFe in the prepared magnetic biochar-based bismuth tungstate composite photocatalyst 2 O 4 Is present.
In FIG. 6, bi 2 WO 6 Is at 570cm -1 、740cm -1 And 1385cm -1 Respectively show that it belongs to Bi 2 WO 6 The characteristic peaks corresponding to Co-O, fe-O, W-O, bi-O and W-O-W were also found in the 5CFO/3BC/BWO spectra for the W-O, bi-O and W-O-W, thereby confirming the success of the preparation of the 5CFO/3BC/BWO composite catalyst.
FIG. 7 shows Ultraviolet-visible spectrum (Uv-Vis) spectra of the magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate prepared in the examples of the present specification.
In FIG. 7, the absorption band edge of BWO is 4572 nm and the absorption band edge of 5CFO/3BC/BWO is 479nm, showing that CoFe is introduced into the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the example of the present specification 2 O 4 The absorption threshold of the composite photocatalyst material is obviously red shifted, and the light response range of the catalyst is effectively widened.
Fig. 8 shows band gap energy spectra of the magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate prepared in the examples of the present specification.
In fig. 8, the energy gap widths of BWO and 5CFO/3BC/BWO are estimated according to the Tauc Plot equation, where eg=2.83 eV for BWO and eg=2.64 eV for 5CFO/3BC/BWO, which proves that the energy gap width of the magnetic biochar-based bismuth tungstate composite photocatalyst material prepared in the embodiment of the present specification is effectively shortened.
Fig. 9 shows nitrogen adsorption-desorption isotherms of the magnetic biochar-based bismuth tungstate composite photocatalyst and bismuth tungstate prepared in the examples of the present specification.
In FIG. 9, the adsorption equilibrium isotherms of BWO and 5CFO/3BC/BWO are in accordance with type IV, belonging to the H3 hysteresis loop. The pore diameters of the two materials are middle pore or large pore type materials, and the adsorption materials have stronger interaction with organic pollutants.
Table 1 shows BET specific surface area-related parameters of the magnetic biochar-based bismuth tungstate composite photocatalyst prepared in the examples of the present specification. The BET specific surface area-related parameters in FIG. 1 were obtained according to the BET specific surface area test method.
TABLE 1 specific surface area related parameters of BWO and 5CFO/3BC/BWO
| Sample of | Specific surface area (m) 2 /g) | Pore volume (cm) 2 /g) | Aperture (nm) |
| BWO | 15.95 | 0.05 | 12.6 |
| 5CFO/3BC/BWO | 45.64 | 0.15 | 13.1 |
As shown in Table 1, the specific surface area of BWO was 15.95m 2 In contrast, the specific surface area of 5CFO/3BC/BWO is increased by 2 times than that of BWO, and can reach 45.64m 2 And/g. This is because the addition of the porous material BC makes the 5CFO/3BC/BWO have a larger specific surface area.
Further calculating the pore volume and the pore diameter of the material to obtain the pore volumes of BWO and 5CFO/3BC/BWO of 0.05cm respectively 2 Per g and 0.15cm 2 Per gram, pore diameters of 12.6cm respectively 2 /g and 13.1cm 2 And/g. In comparison, the pore volume and the pore diameter are also greatly increased. The increase of the specific surface area and the pore volume can provide more active sites and adsorb more pollutants so that the catalytic efficiency after compounding is more excellent.
Fig. 10 shows hysteresis loop patterns of the magnetic biochar-based bismuth tungstate composite photocatalyst and the cobalt ferrite prepared in the embodiment of the present specification.
In FIG. 10, coFe 2 O 4 The magnetization curves of both 5CFO/3BC/BWO exhibit a symmetrical S-shape, wherein CoFe 2 O 4 The saturation Magnetization (MS) was 3.87emu/g, and the 5CFO/3BC/BWO saturation Magnetization (MS) was 0.22emu/g.
In the small diagram of fig. 10, the right diagram shows that the 5CFO/3BC/BWO composite photocatalyst is dispersed in the solution, and the left diagram shows the magnetic attraction condition after the external magnetic field is added for 3min, and it can be seen that the 5CFO/3BC/BWO has good magnetic separation capability.
Example 3: application of magnetic biochar-based bismuth tungstate composite photocatalyst
The 5CFO/3BC/BWO has stronger oxidizing capability to organic pollutants, and in practical application, the 5CFO/3BC/BWO can be directly added into a water body containing the organic pollutants under the irradiation of visible light, and a rotor is added into the solution for magnetic stirring, so that the 5CFO/3BC/BWO is uniformly dispersed in the solution to keep full contact with the pollutants, and the aim of efficiently removing the organic matters is fulfilled.
In the adsorption-degradation experiment effect comparison experiment, 10mg/L Ciprofloxacin (CIP) +5mg/L Tetracycline (TC) is used as a target pollutant. At ph=7.0, the CFO/BC/BWO series composite catalyst was subjected to adsorption and degradation experiments on cip+tc at an addition amount of 50 mg.
Fig. 11 shows adsorption performance curves of magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the example of the present specification to Ciprofloxacin (CIP). Fig. 12 shows adsorption performance curves of the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the example of the present specification on Tetracycline (TC).
As shown in fig. 11 and 12, the adsorptivity of CFO/BC/BWO series composite catalysts (including 3CFO/3BC/BWO, 5CFO/3BC/BWO, 7CFO/3BC/BWO, 10CFO/3BC/BWO, etc.) to CIP and TC can be significantly higher than that of pure BWO, indicating that the introduction of biochar provides more adsorption sites for the photocatalyst, and improves adsorption efficiency.
As shown in fig. 11 and 12, in the CFO/BC/BWO series composite catalyst, the adsorption performance of 5CFO/3BC/BWO is higher than that of other photocatalysts (3 CFO/3BC/BWO, 7CFO/3BC/BWO, 10CFO/3 BC/BWO).
Fig. 13 and 14 show photocatalytic degradation curves of the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the embodiment of the present specification on a binary system of Ciprofloxacin (CIP) and Tetracycline (TC). Wherein, fig. 13 shows the photocatalytic degradation curves of the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the embodiment of the present specification on CIP in a CIP and TC binary system; fig. 14 shows photocatalytic degradation curves of the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared in the example of the present specification for TC in CIP and TC binary systems.
In a binary system of CIP and TC, the concentration of CIP is 10mg/L, and the concentration of TC is 5mg/L.
As shown in FIGS. 13 and 14, the oxidative degradation performance of CFO/BC/BWO series composite catalysts (including 3CFO/3BC/BWO, 5CFO/3BC/BWO, 7CFO/3BC/BWO, 10CFO/3BC/BWO, etc.) on CIP and TC can be significantly higher than pure BWO. The photocatalytic degradation result shows that the CFO/BC/BWO series composite catalyst forming the heterostructure and single Bi 2 WO 6 Compared with the prior art, the photocatalytic performance is effectively improved.
As shown in FIGS. 13 and 14, in the CFO/BC/BWO series composite catalyst, the 5CFO/3BC/BWO has higher oxidizing power than other photocatalysts (3 CFO/3BC/BWO, 7CFO/3BC/BWO, 10CFO/3 BC/BWO), 92.4% of CIP and 95.3% of TC can be oxidatively degraded within 90 minutes of the photoreaction.
According to the experimental study of adsorption-degradation, the magnetic biochar-based bismuth tungstate composite photocatalyst (5 CFO/3 BC/BWO) prepared in the embodiment of the specification can be proved to be compared with the existing single Bi 2 WO 6 The photocatalysis technology can effectively improve the adsorption performance and the catalysis performance of the photocatalyst, and solves the problem of high electron-hole recombination rate of the semiconductor photocatalyst.
In addition, the magnetic recovery of 5CFO/3BC/BWO was also demonstrated by the magnetic separation data in FIG. 10, solving the problem of difficult recovery of the powder catalyst.
The magnetic biochar-based bismuth tungstate series composite photocatalyst prepared according to one or more embodiments of the specification has at least the following technical effects:
first, have higher adsorptivity. In one or more embodiments of the present disclosure, the magnetic biochar-based bismuth tungstate series composite photocatalyst prepared by introducing 3% of Biochar (BC) prepared from agricultural waste biomass greatly improves the adsorption performance for organic pollution in water environment. As can be seen from SEM images, BC is an adsorbent having a porous structure with a large specific surface area.
Second, it has better magnetic recovery. The recycling of the existing powdery photocatalyst is difficult. In one or more embodiments of the present description, the magnetic material is formed by introducing 5% of a magnetic material cobalt ferrite (CoFe 2 O 4 ) The prepared magnetic biochar-based bismuth tungstate series composite photocatalyst can recover the powdery catalyst through the magnetism of the magnetic biochar-based bismuth tungstate series composite photocatalyst.
Thirdly, the photocatalysis efficiency is effectively improved. In one or more embodiments of the present specification, the magnetic substance cobalt ferrite (CoFe) in the prepared magnetic biochar-based bismuth tungstate series composite photocatalyst 2 O 4 ) With Bi 2 WO 6 The heterogeneous structure is formed by compounding, the forbidden bandwidth of the catalyst is effectively reduced, and the aim of improving the photocatalytic performance is fulfilled.
Fourth, can degrade and remove multiple pollutant at the same time. In the previous researches, most of photocatalysis methods only degrade single pollutants, in actual water, the types of antibiotics are complex and various, and in a multi-solute system, strong competition for adsorption sites may exist among antibiotics, and the competitive adsorption behavior and the cooperative removal mechanism of the multi-solute system still need to be further explored. In view of this, how to degrade multi-solute systems and increase the recovery of catalytic materials is a bottleneck problem that needs to be solved in the field of photocatalytic technology at present. In one or more embodiments of the present disclosure, a multi-functional material system is constructed using straw biochar as a carrier. The preparation of the magnetic biochar-based multifunctional material is used for synchronously removing various trace antibiotics. The research result can promote the value of agricultural waste resources, enrich the content of a theoretical system for cooperatively removing the composite pollutants of the slightly polluted water body by the biochar-based multifunctional material, realize the efficient recovery of the functional material, provide technical support for the application of the multifunctional material in the restoration of the slightly polluted water body, and have guiding significance in the field of water environment safety guarantee. Meanwhile, the method is helpful to provide basic data in the aspect of developing novel nano photocatalytic materials for efficiently and deeply removing organic matters in water.
The foregoing describes specific embodiments of the present disclosure. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and changes may be made to the present application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. which are within the spirit and principles of the present application are intended to be included within the scope of the claims of the present application.
Claims (9)
1. A magnetic biochar-based bismuth tungstate composite photocatalyst, which is characterized by comprising:
a biochar carrier;
cobalt ferrite; is loaded on the biochar carrier;
bismuth tungstate; is loaded on the biochar carrier.
2. The magnetic biochar-based bismuth tungstate composite photocatalyst as claimed in claim 1, wherein a mass of the biochar carrier is 3% of a mass of the bismuth tungstate; the mass of the cobalt ferrite is 3-10% of the mass of the bismuth tungstate.
3. The preparation method of the magnetic biochar-based bismuth tungstate composite photocatalyst is characterized by comprising the following steps of:
in a tube furnace at N 2 Under the protection, heating the crop stem powder to prepare biochar;
preparing cobalt ferrite powder by using cobalt nitrate and ferric nitrate;
bismuth nitrate and sodium tungstate are used for preparing bismuth tungstate solution;
and adding the biochar and the cobalt ferrite powder into the bismuth tungstate solution, and preparing the magnetic biochar-based bismuth tungstate composite photocatalyst by a hydrothermal method.
4. The method of claim 3, wherein the step of preparing biochar comprises:
drying crop stems and grinding the crop stems into powder to obtain corn stem powder;
placing crop stalk powder in a tube furnace, and adding N 2 Under the protection, the temperature is 5-10 ℃ for min -1 Heating to 790-810 ℃ to obtain a biochar crude product;
and washing and drying the biochar crude product to obtain a biochar product.
5. The method according to claim 4, wherein the step of washing and drying the crude biochar product to obtain a biochar product comprises the following steps:
washing silicate in the biochar crude product by using sodium hydroxide solution;
washing out metal impurities in the biochar crude product by using hydrochloric acid solution;
repeatedly washing the biochar crude product to be neutral by using deionized water;
and (5) drying in vacuum to obtain the biochar.
6. The method of preparing as claimed in claim 3, wherein the step of preparing the cobalt ferrite powder comprises:
fe (NO) 3 ) 3 ·9H 2 O is dissolved in water to obtain ferric nitrate solution;
co (NO) 3 ) 2 ·6H 2 O is dissolved in water to obtain cobalt nitrate solution;
slowly pouring the cobalt nitrate solution into the ferric nitrate solution, regulating the pH value to 11-13, and stirring to obtain a solution before reaction;
placing the pre-reaction solution into a high-pressure reaction kettle, and reacting for a first period of time at a first temperature to obtain a post-reaction solution; the first temperature is 160 ℃ to 200 ℃; the first duration is 11 hours to 13 hours;
and drying and grinding the solid in the solution after the reaction to obtain cobalt ferrite powder.
7. A method according to claim 3, wherein the step of preparing the bismuth tungstate solution comprises:
bi (NO) 3 ) 3 ·5H 2 O is dissolved in nitric acid solution to obtain bismuth nitrate solution;
na is mixed with 2 WO 4 ·2H 2 O is dissolved in water, and sodium hydroxide solution is added to obtain sodium tungstate solution;
while stirring, a sodium tungstate solution was slowly added dropwise to the bismuth nitrate solution to obtain a bismuth tungstate solution containing a white precipitate.
8. A method of preparing as claimed in claim 3 wherein the mass of biochar added to the bismuth tungstate solution is 3% of the mass of bismuth tungstate in the bismuth tungstate solution;
the mass of the cobalt ferrite powder added into the bismuth tungstate solution is 3-10% of the mass of the bismuth tungstate in the bismuth tungstate solution.
9. The preparation method of claim 3, wherein the step of preparing the magnetic biochar-based bismuth tungstate composite photocatalyst by a hydrothermal method specifically comprises the following steps:
adding a proper amount of biochar and a proper amount of cobalt ferrite powder into the bismuth tungstate solution, and stirring vigorously to obtain a turbid liquid;
placing the turbid liquid in an autoclave, and reacting for a second time period at a second temperature to obtain a composite photocatalyst product solution; the second temperature is 160 ℃ to 200 ℃; the second period of time is 5 hours to 7 hours;
and removing the supernatant from the composite photocatalyst product solution, and washing and drying the solution to obtain the magnetic biochar-based bismuth tungstate composite photocatalyst.
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