CN115920869A - La-BiOCl/LDHs composite material and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a La-BiOCl/LDHs composite material as well as a preparation method and an application thereof, wherein the La-BiOCl/LDHs composite material comprises the following steps: s1, dissolving inorganic salt containing a chlorine source and hydrotalcite in water to prepare a salt solution; dissolving a bismuth source in ethanol, adding the solution into the salt solution at the temperature of between 30 and 90 ℃, and stirring; and S2, stopping heating, adding a lanthanum source into the S1, adjusting the pH value to 10-12, stirring for reaction, cooling to room temperature, filtering, drying and grinding to obtain the La-BiOCl/LDHs composite material. The La-BiOCl/LDHs composite material synthesized by the method has the characteristics of large specific surface area, good photocatalytic performance, high utilization rate of visible light and the like, and the synthesis method is simple, good in photocatalytic effect and low in production cost of the composite material.

Description

La-BiOCl/LDHs composite material and preparation method and application thereof

Technical Field

The invention belongs to the technical field of inorganic non-metallic materials, and particularly relates to a La-BiOCl/LDHs composite material as well as a preparation method and application thereof.

Background

Water is an important resource on which human beings live, but as the social industry rapidly develops, the discharge amount of industrial wastewater gradually increases, and thus, environmental problems are receiving more and more attention. The emission of organic pollutants can not only harm the natural environment, but also have serious influence on the health problems of human beings. The antibiotic wastewater has complex components and belongs to refractory organic wastewater, and due to the discharge of industrial wastewater which does not reach the standard, the existence of antibiotics can be detected in the current ecological environment, thus threatening the health of human and animals.

At present, the treatment methods of antibiotic wastewater mainly comprise a physical treatment method, a chemical treatment method and a biological treatment method. The chemical treatment method has the advantages of stable treatment effect, strong adaptability, convenient reaction and environmental friendliness. In particular, the photocatalytic technology, which is a truly environmentally friendly technology, degrades organic pollutants into H through oxidation-reduction reaction using light as excitation energy ₂ O and CO ₂ Thereby achieving the purpose of purifying environmental sewage.

BiOCl is a material having good photocatalytic properties discovered in recent years, and is an anisotropic layered semiconductor. BiOCl is [ BiO ] layer formed by Bi atom and O atom, then Bi and Cl are connected with each other to form layered BiOCl. Its photocatalytic power is that the interlaminar reaction is used to make the electron hole be formed at different points, but its BiOCl forbidden band width is large, and the required light energy is high.

Disclosure of Invention

In order to solve the technical problems, the invention provides a La-BiOCl/LDHs composite material and a preparation method and application thereof.

The invention is realized by the following technical scheme.

The first purpose of the invention is to provide a preparation method of La-BiOCl/LDHs composite material, which comprises the following steps:

s1, dissolving inorganic salt containing a chlorine source and hydrotalcite in water to prepare a salt solution; dissolving a bismuth source in ethanol, adding the solution into the salt solution at the temperature of between 30 and 90 ℃, and stirring to prepare a mixture;

and S2, stopping heating, adding a lanthanum source into the mixture prepared in the S1, adjusting the pH value to 10-12, stirring for reaction, cooling to room temperature, filtering, drying and grinding to obtain the La-BiOCl/LDHs composite material.

Preferably, the hydrotalcite is prepared by a coprecipitation method, and has a chemical composition represented by the following general formula:

[M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ [A ^n- ] _x/n ·mH ₂ o, wherein M ²⁺ And M ³⁺ Respectively a divalent metal cation and a trivalent metal cation on the host laminate, A ^n- Is an anion.

Preferably, the divalent metal cation comprises Mg ²⁺ 、Ni ²⁺ 、Zn ²⁺ 、Mn ²⁺ 、Cu ²⁺ 、Co ²⁺ 、Pd ²⁺ 、Fe ²⁺ (ii) a The trivalent metal cation comprises Al ³⁺ 、Cr ³⁺ 、Co ³⁺ 、Fe ³⁺ (ii) a The anion comprises CO ₃ ^2- 、NO ₃ ^- 、Cl ^- 。

Preferably, the inorganic salt containing a chlorine source is sodium chloride, potassium chloride or calcium chloride; the bismuth source is bismuth nitrate pentahydrate, bismuth trioxide or bismuth chloride; the lanthanum source is lanthanum nitrate.

Preferably, the inorganic salt containing a chlorine source: hydrotalcite: the mass ratio of the bismuth source is 0.0234-0.2864: 0.5 to 3.0:0.2425 to 1.6977; a lanthanum source: the mass ratio of the hydrotalcite is 0.03-0.27: 0.5 to 3.0.

Preferably, in S1, the bismuth source ethanol solution is added dropwise to the salt solution by a peristaltic pump at a speed of 2 to 5 RPM.

Preferably, in S1, the stirring time is 1-4h.

Preferably, in S2, the stirring time is 1-4h.

The second purpose of the invention is to provide the La-BiOCl/LDHs composite material prepared by the preparation method.

The third purpose of the invention is to provide the application of the La-BiOCl/LDHs composite material in photocatalytic degradation of organic pollutants in wastewater.

Compared with the prior art, the invention has the following beneficial effects:

hydrotalcite-like compounds (LDHs) are alkaline inorganic compounds and are a series of supramolecular materials assembled by compound intercalation. The layered structure of the hydrotalcite enables the hydrotalcite to have a very large microporous structure, the types and the quantity of metal ions forming the hydrotalcite can be intervened through artificial synthesis, and meanwhile, the layered structure enables the hydrotalcite to have a special adsorption function, so that the hydrotalcite can be used as a catalyst or an adsorbent for treating polluted wastewater. In order to solve the defects of the BiOCl photocatalytic material, la-BiOCl is loaded on hydrotalcite and then doped, so that the forbidden bandwidth of the material can be reduced, and the photoresponse capability of the material can be improved. Doping of the BiOCl with metal ions affects the photocatalytic activity of BiOCl by two ways: active 'islands' are formed in the BiOCl crystal lattice, so that the generation, recombination and transfer processes of electrons and holes are influenced; the energy level of the metal element is positioned in a forbidden band of BiOCl, and the energy band structure of BiOCl can be changed. Specifically, after BiOCl is loaded on the surface and the interlayer of hydrotalcite, the specific surface area of the catalyst is improved, so that pollutant molecules adsorbed on the surface of the catalyst are increased, and the capacity of transferring electrons to pollutants is improved; the surface of the hydrotalcite layer is provided with a large number of hydroxyl groups which can react with the holes to generate more hydroxyl radicals (OH) required by organic matter degradation, so that the photodegradation efficiency of the catalyst on pollutants is improved; la and other forms of La are attached to the BiOCl surface as electron traps capable of reacting with oxygen O ₂ The combination ultimately generates hydroxyl radicals, resulting in enhanced electron and hole separation capabilities.

The chemical reagents used in the method are common reagents, the synthesis process is mild and simple, and the requirements of green development are met; the synthesis method has low cost and can greatly reduce the manufacturing cost; the La-BiOCl/LDHs composite material synthesized by the method has the advantages of increased specific surface area, improved photocatalytic performance, improved utilization rate of visible light and high removal efficiency of organic pollutants.

Drawings

FIG. 1 is SEM and TEM images of nano BiOCl and La-BiOCl/LDHs/LDHs composite materials synthesized in example 3 of the present invention;

FIG. 2 is an XRD pattern of the nano BiOCl and La-BiOCl/LDHs composite material synthesized in example 3 of the present invention;

FIG. 3 is the FT-IR chart of the nano BiOCl and La-BiOCl/LDHs composite material synthesized in example 3 of the present invention.

FIG. 4 is a diagram of UV-DRS of the nano BiOCl and La-BiOCl/LDHs composite material synthesized in example 3 of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood and implemented by those skilled in the art, the present invention is further described below with reference to the following specific embodiments and the accompanying drawings, but the embodiments are not meant to limit the present invention.

The experimental methods and the detection methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

Hydrotalcite is prepared by a coprecipitation method, and the chemical composition of the hydrotalcite has the following general formula: [ M ] A ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ [A ^n- ] _x/n ·mH ₂ O, wherein M ²⁺ And M ³⁺ Respectively a divalent metal cation and a trivalent metal cation, A, located on the host layer plate ^n- Being an anion, the divalent metal cation comprising Mg ²⁺ 、Ni ²⁺ 、Zn ²⁺ 、Mn ²⁺ 、Cu ²⁺ 、Co ²⁺ 、Pd ²⁺ 、Fe ²⁺ (ii) a The trivalent metal cation comprises Al ³⁺ 、Cr ³⁺ 、Co ³⁺ 、Fe ³⁺ (ii) a The anion comprises CO ₃ ^2- 、NO ₃ ^- 、Cl ^- 。

For example: weighing 41.03g of magnesium nitrate and 15.01g of aluminum nitrate, dissolving the magnesium nitrate and the aluminum nitrate in 200mL of distilled water to prepare a salt solution, weighing 13.50g of sodium hydroxide and 10.60g of sodium carbonate, dissolving the sodium hydroxide and the sodium carbonate in 200mL of distilled water to prepare an alkali solution, placing the alkali solution in a magnetic stirring water bath kettle, keeping the temperature of the alkali solution at 60 ℃, stirring, dropwise adding the salt solution into the alkali solution at the speed of 2RPM by a peristaltic pump, continuously stirring for 4 hours after dropwise adding, taking out a beaker from the water bath kettle, cooling to room temperature, centrifuging by a centrifuge at the speed of 6000 RPM, taking out a white precipitate, drying, and grinding through a 100-mesh sieve to obtain the hydrotalcite with 100 meshes.

Comparative example 1

And (3) synthesis of nano BiOCl: weighing 0.1461g of sodium chloride in 30mL of water to prepare a salt solution, placing the salt solution in a water bath kettle at 30 ℃, weighing 1.2127g of bismuth nitrate pentahydrate in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the bismuth nitrate pentahydrate into the salt solution at the speed of 5RPM through a peristaltic pump, continuing stirring for 3 hours after dropwise addition, cooling to room temperature, performing suction filtration, drying and grinding a white precipitate to obtain the nano BiOCl.

Example 1

Synthesizing La-BiOCl/LDHs: weighing 0.1461g of sodium chloride and 0.5g of 100-mesh zinc-aluminum hydrotalcite in 30mL of water to prepare a salt solution, placing the salt solution in a water bath kettle at 30 ℃, weighing 1.2127g of pentahydrated bismuth nitrate in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the pentahydrated bismuth nitrate into the salt solution at the speed of 5RPM by a peristaltic pump, continuing stirring for 3h after the dropwise addition is finished, stopping heating after the stirring is finished, adding 0.09g of lanthanum nitrate, adjusting the pH value to 10, stirring for 4h, cooling to room temperature, then carrying out suction filtration, drying and grinding the white precipitate to obtain the La-BiOCl/LDHs composite material.

Comparative example 2

And (3) synthesis of the nano BiOCl: weighing 0.1753g of sodium chloride in 30mL of water to prepare a salt solution, placing the salt solution in a water bath kettle at 90 ℃, weighing 1.2127g of bismuth chloride in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the bismuth chloride into the salt solution at the speed of 2RPM through a peristaltic pump, continuing stirring for 2 hours after dropwise addition, cooling to room temperature, performing suction filtration, and drying and grinding a white precipitate to obtain the nano BiOCl.

Example 2

Synthesizing La-BiOCl/LDHs: weighing 0.1753g of sodium chloride and 3.0g of 100-mesh magnesium-aluminum hydrotalcite in 30mL of water to prepare a salt solution, placing the salt solution in a water bath at 90 ℃, weighing 1.2127g of bismuth chloride in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the bismuth chloride into the salt solution at the speed of 2RPM through a peristaltic pump, continuing stirring for 2h after the dropwise addition is finished, stopping heating after the stirring is finished, adding 0.03g of lanthanum nitrate, adjusting the pH value to 10, stirring for 1h, performing suction filtration after cooling to room temperature, drying and grinding the white precipitate to obtain the La-BiOCl/LDHs composite material.

Comparative example 3

And (3) synthesis of nano BiOCl: weighing 0.1636g of sodium chloride in 30mL of water to prepare a salt solution, placing the salt solution in a water bath kettle at 50 ℃, weighing 1.6977g of bismuth nitrate pentahydrate in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the salt solution at the speed of 3RPM through a peristaltic pump, continuing stirring for 1h after dropwise addition is finished, cooling to room temperature, performing suction filtration, and drying and grinding a white precipitate to obtain the nano BiOCl.

Example 3

Synthesizing La-BiOCl/LDHs: weighing 0.1636g of sodium chloride and 1.0g of 100-mesh zinc-chromium hydrotalcite in 30mL of water to prepare a salt solution, placing the salt solution in a 50 ℃ water bath, weighing 1.6977g of pentahydrated bismuth nitrate in 50mL of absolute ethyl alcohol for ultrasonic treatment, adding the mixture into the salt solution at the speed of 3RPM through a peristaltic pump, continuing stirring for 1h after the dropwise addition is finished, stopping heating after the stirring is finished, adding 0.15g of lanthanum nitrate, adjusting the pH value to 10, stirring for 4h, cooling to room temperature, then performing suction filtration, drying and grinding the white precipitate to obtain the La-BiOCl/LDHs composite material.

In FIG. 1, (a), (c) are SEM and TEM images of BiOCl synthesized in example 3 of the present invention, respectively, (b), (d) are SEM and TEM images of the nano La-BiOCl/LDHs composite material of example 3, respectively, and as can be seen from the SEM image in FIG. 1, the dispersibility of the nano La-BiOCl/LDHs composite material is well improved, the particle size is reduced, and meanwhile, la-BiOCl/LDHs still presents a layered structure as the BiOCl, which shows that the material after doping and compounding still has the structure of BiOCl, and the ratio table shows thatThe area is increased, belonging to nano-grade materials. From FIG. 1 (c TEM image, it can be seen that nano BiOCl has large particle morphology and high overlap and serious agglomeration, while La-BiOCl/LDHs has flower-like hydrotalcite combined with it, so that BiOCl is well dispersed and the total specific surface area is increased, thereby exposing more photocatalytic active sites, from FIG. 1 (d TEM image, it can be seen that there is a point-like substance generated on the surface of the material, and La (OH) generated on the surface by doped La is possible ₃ And precipitating to show that the La element is successfully doped into the material crystal lattice.

FIG. 2 is an XRD pattern of the nano BiOCl and nano La-BiOCl/LDHs composite material synthesized in example 3 of the present invention; as can be seen from fig. 2: the crystal planes (001), (101), (110), (102), (200), (221), (212) are consistent with the BiOCl card JCPDS No.06-0249 of the tetragonal phase. The spectrum of La-BiOCl/LDHs has reduced sharpness of the corresponding diffraction peak compared with the prepared pure BiOCl, but still has the basic structure of BiOCl and has relatively complete structure. The composite material prepared by the experiment is good in development and high in crystallinity, and is compounded with hydrotalcite while being doped with La, the crystalline phase of the substance is not changed, and the material still takes BiOCl as a main body.

FIG. 3 is FT-IR diagram of the synthesized nano BiOCl and nano La-BiOCl/LDHs composite material of example 3 of the present invention; as can be seen from fig. 3: wherein 530.81cm ^-1 And 1325.34cm ^-1 The area is a characteristic absorption peak of BiOCl, and the material La-BiOCl/LDHs also has an absorption peak in the area, which indicates that the La-BiOCl/LDHs really contains BiOCl;3443.79cm ^-1 Formed by the stretching vibration of water molecules between hydroxyl and hydrotalcite layers, 1624.72cm ^-1 The absorption peak and the deformation vibration of hydrotalcite interlayer water; la-BiOCl/LDHs at 1353.78cm ^-1 The shift of the characteristic absorption peak of the Bi-O bond may be caused by CO between hydrotalcite layers after the compound with hydrotalcite ₃ ^2- Caused by antisymmetric stretching vibration of; 855.28cm ^-1 The absorption peak is a tensile absorption peak of the La-O skeleton, which indicates that the La element is successfully doped and is relatively stable.

FIG. 4 is a diagram of UV-DRS of the nano BiOCl and nano La-BiOCl/LDHs composite material synthesized in example 3 of the present invention; as can be seen from fig. 4: biOCl mainly absorbs in an ultraviolet region, and La-BiOCl/LDHs has partial absorption in a visible region besides the ultraviolet region. The light absorption threshold values of BiOCl and La-BiOCl/LDHs can be obtained according to a tangent method, and are 374.6nm and 472.9nm respectively.

Calculating formula E according to forbidden bandwidth _g ＝1240/λ _g It can be calculated that the forbidden band width of BiOCl is about 3.31eV, and the forbidden band width of La-BiOCl/LDHs is 2.62eV. The La-BiOCl/LDHs not only improves the light absorption capacity, but also obviously reduces the forbidden band width, thereby improving the light response capacity to ultraviolet light and visible light and improving the performance of the material for degrading pollutants by photocatalysis.

The SEM, TEM, XRD, FT-IR and UV-DRS results of the materials in example 1 and example 2 are similar to those in example 3, and are not repeated.

10mg of the synthesized BiOCl and La-BiOCl/LDHs were weighed respectively, and placed in 100mL of tetracycline hydrochloride solution containing 20mg/L, stirred in the dark at 25 ℃ for 0.5h, stirred under ultraviolet irradiation for 2h, filtered through a 0.45 μm microfiltration membrane to obtain a clarified solution, and the absorbance of the tetracycline hydrochloride solution was measured at 358nm using an ultraviolet spectrophotometer, and the results are shown in Table 1.

TABLE 1 results of detection and analysis of samples of examples

As can be seen from Table 1, the La-BiOCl/LDHs composite material has better organic wastewater removal effect than nano BiOCl photocatalysis effect, and the specific surface area of the modified material is increased, so that the contact with pollutants is improved, and the photocatalysis process is facilitated.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, it is intended that such changes and modifications be included within the scope of the present invention as set forth in the appended claims and their equivalents.

Claims (10)

1. A preparation method of a La-BiOCl/LDHs composite material is characterized by comprising the following steps:

s1, dissolving inorganic salt containing a chlorine source and hydrotalcite in water to prepare a salt solution; dissolving a bismuth source in ethanol, adding the solution into the salt solution at the temperature of between 30 and 90 ℃, and stirring to prepare a mixture;

and S2, stopping heating, adding a lanthanum source into the mixture prepared in the S1, adjusting the pH to 10-12, stirring for reaction, cooling to room temperature, filtering, drying and grinding to obtain the La-BiOCl/LDHs composite material.

2. The method according to claim 1, wherein the hydrotalcite is prepared by a coprecipitation method and has a chemical composition represented by the following general formula: [ M ] A ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ [A ^n- ] _x/n ·mH ₂ O, wherein M ²⁺ And M ³⁺ Are respectively divalent metal cations and trivalent metal cations, A ^n- Is an anion.

3. The method of claim 2, wherein the divalent metal cation is Mg ²⁺ 、Ni ²⁺ 、Zn ^{2 +} 、Mn ²⁺ 、Cu ²⁺ 、Co ²⁺ 、Pd ²⁺ 、Fe ²⁺ (ii) a The trivalent metal cation is Al ³⁺ 、Cr ³⁺ 、Co ³⁺ 、Fe ³⁺ (ii) a The anion being CO ₃ ^2- 、NO ₃ ^- 、Cl ^- 。

4. The method according to claim 1, wherein the inorganic salt containing a chlorine source is sodium chloride, potassium chloride or calcium chloride; the bismuth source is bismuth nitrate pentahydrate, bismuth trioxide or bismuth chloride; the lanthanum source is lanthanum nitrate.

5. The method according to claim 1, characterized in that the ratio of inorganic salt containing chlorine source: hydrotalcite: the mass ratio of the bismuth source is 0.0234-0.2864: 0.5 to 3.0:0.2425 to 1.6977; a lanthanum source: the mass ratio of the hydrotalcite is 0.03-0.27: 0.5 to 3.0.

6. The method according to claim 1, wherein the bismuth source in the ethanol solution is added dropwise to the salt solution in S1 by a peristaltic pump at a speed of 2 to 5 RPM.

7. The method according to claim 1, wherein the stirring time in S1 is 1 to 4 hours.

8. The method according to claim 1, wherein the stirring time in S2 is 1 to 4 hours.

9. The La-BiOCl/LDHs composite material prepared by the preparation method of any one of claims 1 to 8.

10. The use of the La-BiOCl/LDHs composite of claim 9 for photocatalytic degradation of organic pollutants in wastewater.

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