CN104801308A - A kind of NiFe2O4/TiO2/sepiolite composite photocatalyst and its preparation method - Google Patents

Abstract

A NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, the composition includes sepiolite, TiO ₂ and NiFe ₂ O ₄ , sepiolite is used as a carrier, TiO ₂ is wrapped on the surface of sepiolite in the form of a film, NiFe ₂ O ₄ is supported on the surface of TiO ₂ in the form of particles. The invention also provides a preparation method of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst. In the present invention, TiO ₂ is wrapped on the surface of sepiolite in the form of film, NiFe ₂ O ₄ is loaded on the surface of TiO ₂ in the form of particles, and NiFe ₂ O ₄ is loaded on the surface of TiO ₂ film in the form of particles, which will not cover all TiO ₂ film, but with TiO ₂ to form a coincidence effect, using sepiolite as a carrier, can further improve the adsorption capacity of the catalyst, so that the catalyst has good adsorption effect, high photocatalytic activity, and can be recycled and reused In addition, the photoresponse range is expanded. This catalyst not only improves the catalytic activity in the ultraviolet region, but also shifts the response wavelength from the ultraviolet region to the visible region, thereby improving the utilization rate of sunlight.

Description

A kind of NiFe2O4/TiO2/sepiolite composite photocatalyst and its preparation method

technical field

The invention relates to the technical field of photocatalytic oxidation, in particular to a NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst and a preparation method thereof.

Background technique

Photocatalytic oxidation technology is a new type of high-efficiency industrial wastewater treatment technology that has been applied in the field of wastewater for more than 20 years. The photocatalyst commonly used in photocatalytic oxidation technology is nano-TiO ₂ , which is used for wastewater treatment and is a new breakthrough in environmental protection technology. Under the irradiation of ultraviolet light, the nano- _TiO2 photocatalyst can generate electron-hole pairs with strong oxidation and reduction capabilities, which can effectively degrade chlorinated phenols, halogenated hydrocarbons, dioxins, various Organic acids, etc., and have high cleanliness, fast degradation speed, no secondary pollution, long service life, wide range of applicable pollutants, and achieve the purpose of one-time degradation of pollutants, so its research is very extensive.

At present, TiO ₂ has some shortcomings in the practical application process as a photocatalyst, such as: the photocatalyst quantum efficiency of TiO ₂ is low, the selective adsorption is poor, the curing conditions are harsh, easy to condense, easy to deactivate, and the spectral response range is in the ultraviolet In the light region, the visible part of the solar spectrum cannot be effectively utilized, which limits the industrial application of _TiO2 . In view of the shortcomings of TiO ₂ as a photocatalyst, there are currently two main researches on the modification of TiO ₂ photocatalysts at home and abroad: one is to develop TiO ₂ supported photocatalysts; the other is to modify TiO ₂ by doping, make it better used in practical applications.

In the field of TiO ₂ supported photocatalyst research, some researchers have developed a TiO ₂ / sepiolite supported photocatalyst, which is a catalyst coated with TiO ₂ on the surface of sepiolite, which is a hydrous magnesium aluminum silicate Clay minerals are cheap and widely sourced. They are porous media materials with a larger specific surface area, which can improve the adsorption effect on organic pollutants. There are a large number of micropores in the crystal structure of sepiolite, which are composed of countless parallel tubular pores, and its specific surface area is large. The adsorption properties of sepiolite are restricted by its crystal structure. The surface charge of sepiolite is caused by the hydrolysis and rupture of the Si-O bond and Al-O bond on the surface, which can be used as an acid or a base, and the hydroxyl group (-OH) on the R-OH produced by the bond-breaking hydrolysis, so It is amphoteric, and these surface reactions charge the surface of sepiolite. The modification is mainly to change the structural charge and surface charge of sepiolite in aqueous solution, thereby changing the chargeability and adsorption activity of sepiolite.

In the field of modification of TiO ₂ by doping, some researchers use magnetic materials to dope TiO ₂ to form a composite catalyst. The commonly used doping method is to wrap TiO 2 on the surface of _{Fe 3} O ₄ or CoFe ₂ O ₄ , this composite catalyst can increase the range of light absorption and photocatalytic activity. In addition, due to the doping of magnetic materials, it is beneficial to the recovery and reuse of the catalyst.

Contents of the invention

The technical problem to be solved by the present invention is to provide a NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst which has the advantages of good adsorption effect, high photocatalytic activity, and the ability to recycle and reuse.

In order to solve the above technical problems, the present invention adopts the following technical scheme: a NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, the components include sepiolite, TiO ₂ and NiFe ₂ O ₄ , the sepiolite is the carrier, TiO ₂ is wrapped on the surface of sepiolite in the form of film, and NiFe ₂ O ₄ is loaded on the surface of TiO ₂ in the form of particles.

Further, the content of Ni is 1-2wt%, the content of Fe is 1.9-3.8wt%, the content of Ti is 12-18wt%, and the rest is sepiolite. When the content of each component of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst is within this range, its catalytic effect is better.

Further, the content of Ni is 1.5wt%, the content of Fe is 2.8wt%, the content of Ti is 15wt%, and the rest is sepiolite.

The present invention also provides a preparation method of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, comprising the following steps:

(1) Pretreatment of sepiolite

Pulverize sepiolite into powder, soak in dilute nitric acid with a concentration of 5-15% for 15-24 hours, filter, rinse with water until neutral, dry, and then calcinate at 400-500°C for 2-4 hours, Rinse with water and filter out the sepiolite floating in the upper part of the water body, and sieve the sepiolite powder with a particle size of 100-125 mesh as a carrier after drying;

(2) Preparation of TiO ₂ sol

At room temperature, in parts by volume, fully dissolve 15-20% butyl titanate in 40-50% absolute ethanol, then add 5-6% acetylacetone to obtain solution A, mix 0.75-1.0% distilled water and 20- 25% of absolute ethanol is fully mixed to obtain solution B, gradually add solution B to solution A under the condition of constant stirring, then adjust the pH value to 4-5 with concentrated nitric acid or concentrated hydrochloric acid, stir for 1-2h, add 1-1.5 polyethylene glycol, then stirred at 40-65°C for 1-1.5h to obtain a yellow and transparent TiO ₂ sol, and aged the TiO ₂ sol at room temperature for 12-15h;

(3) Coating TiO ₂ film on the surface of sepiolite

The number of layers of TiO ₂ film is 1-3 layers, and the formation method of each layer of TiO ₂ film is as follows: at room temperature, add sepiolite to TiO ₂ sol, stir until it is completely mixed with TiO ₂ sol, and then in 70-85 Dry under the condition of ℃, and finally calcined under the condition of 400-500℃ for 1-3h, cool down and set aside;

(4) Loading NiFe ₂ O ₄ particles on the surface of TiO ₂ film

At room temperature, in parts by weight, add 2.91-5.82 Ni(NO ₃ ) ₂ ·6H ₂ O and 8.08-16.16 Fe(NO ₃ ) ₃ ·9H ₂ O into 55.3-63.2 absolute ethanol, stir for 30 -60min, adjust the pH value to 9-10 with 5-20mol/L NaOH solution, then add sepiolite wrapped with TiO ₂ film, stir for 30-60min, then react at 160-180℃ for 18- After cooling for 24 hours, carry out solid-liquid separation, water washing, and finally dry at 70-85°C to obtain the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst.

For the sake of concise description, the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst described in the present invention is referred to as the catalyst for short, and the preparation method of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst referred to as this method.

The beneficial effects of the present invention are:

(1) In this catalyst, TiO ₂ is wrapped on the surface of sepiolite in the form of film, NiFe ₂ O ₄ is loaded on the surface of TiO ₂ in the form of particles, and NiFe ₂ O ₄ is loaded on the surface of TiO ₂ film in the form of particles, which will not Covering all the TiO ₂ film, but forming a coincidence effect with TiO ₂ , using sepiolite as a carrier can further improve the adsorption capacity of the catalyst, so that the catalyst has good adsorption effect, high photocatalytic activity, and can be recycled And the advantages of repeated use, and expand the photoresponse range, the catalytic activity of the catalyst not only in the ultraviolet region is improved, but also the response wavelength is shifted from the ultraviolet region to the visible region, so that the utilization rate of sunlight can be improved.

(2) This catalyst uses NiFe ₂ O ₄ . NiFe ₂ O ₄ not only has magnetic effect, but also is easy to recycle and reuse, and NiFe ₂ O ₄ as a catalyst can also catalyze and degrade pollutants under ultraviolet light. It is loaded on TiO ₂ The surface of the membrane, on the one hand, improves the degradation rate of the catalyst in the ultraviolet region, and on the other hand, broadens the photoresponse range to the visible region.

(3) This method uses a hydrothermal method to synthesize and load NiFe ₂ O ₄ on the surface of the TiO ₂ film. The hydrothermal method is characterized by the ability to prepare nanoparticles with high purity, good dispersibility, and good crystal shape, which makes NiFe ₂ O ₄ is very uniformly loaded on the surface of TiO ₂ film in the form of nanoparticles, and since Ni(OH) ₂ and Fe(OH) ₃ are generated by forced hydrolysis before the hydrothermal reaction, no hydrolysis inhibitor and surface Active agent, so as to ensure that NiFe ₂ O ₄ is not easy to exist in the form of film in the subsequent hydrothermal reaction, but is distributed on the surface of TiO ₂ film in particle state.

(4) this method calcines the sepiolite in the pretreatment process of the sepiolite, the impurities in the sepiolite surface and internal pores can be changed into gaseous substances and removed, thereby increasing the sepiolite specific surface area and porosity, Increasing the surface area and adsorption capacity of sepiolite is beneficial to the loading of _TiO2 and improves the photocatalytic performance.

(5) In the preparation process of _TiO2 sol in this method, tetrabutyl titanate and distilled water undergo hydrolysis reaction to generate _TiO2 sol. Since the hydrolysis of butyl titanate is very violent, acetylacetone is added as its inhibitor, acetylacetone Acetone and butyl titanate form ligands, so that a large amount of water cannot be removed, and these ligands prevent the hydrolysis reaction from proceeding, and the further polymerization of _TiO2 , thus forming a stable colloidal solution.

(6) This method wraps 1-3 layers of TiO ₂ films in the process of wrapping TiO ₂ films on the surface of sepiolite. As the number of TiO ₂ film layers increases, the catalytic effect will become better and better. When the TiO ₂ film layers When the number exceeds 3 layers, the catalytic effect becomes poor.

Description of drawings

Fig. 1 is a scanning electron micrograph of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention.

Fig. 2 is a solid ultraviolet-visible spectrum diagram of the existing TiO ₂ /sepiolite supported photocatalyst and the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention.

Fig. 3 is an infrared spectrogram of sepiolite and the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention.

Fig. 4 is a diagram showing the photocatalytic degradation of methylene blue solution by NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

Example 1

A NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, the composition includes sepiolite, TiO ₂ and NiFe ₂ O ₄ , sepiolite is used as a carrier, TiO ₂ is wrapped on the surface of sepiolite in the form of a film, NiFe ₂ O ₄ is supported on the surface of TiO ₂ in the form of particles, in which the content of Ni is 1.5wt%, that of Fe is 2.8wt%, that of Ti is 15wt%, and the rest is sepiolite.

The preparation method of the above-mentioned NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst comprises the following steps:

(1) Pretreatment of sepiolite

Grind sepiolite into powder, soak in dilute nitric acid with a concentration of 5% for 20 hours, filter, rinse with water until neutral, then dry, then place in a muffle furnace for calcination at 400°C for 4 hours, rinse with water And the sepiolite floating in the middle and upper parts of the water body is filtered out, and after drying, the sepiolite powder with a particle size of 100 meshes is sieved as a carrier;

(2) Preparation of TiO ₂ sol

At room temperature, in parts by volume, fully dissolve 18% butyl titanate in 40% absolute ethanol, then add 5.5% acetylacetone to obtain solution A, and fully mix 0.88% distilled water and 25% absolute ethanol to obtain a solution B. Gradually add solution B to solution A under constant stirring, then adjust the pH value to 4 with concentrated nitric acid, stir (80r/min) for 1.5h, add 1.2 polyethylene glycol, and then Under the condition of stirring (100r/min) 1h, obtain yellow transparent _TiO sol, by _TiO sol aging 12h at room temperature;

(3) Coating TiO ₂ film on the surface of sepiolite

The number of layers of TiO ₂ film is 2 layers, and the formation method of each layer of TiO ₂ film is: at room temperature, add sepiolite to TiO ₂ sol, stir (80r/min) for 1.2h to make sepiolite and TiO ₂ sol Mix completely, and then dry at 70°C. During the drying process, steam in a water bath to nearly dryness, then dry in a drying oven, and finally place it in a muffle furnace for calcination at 500°C for 1 hour, and cool it for later use;

(4) Loading NiFe ₂ O ₄ particles on the surface of TiO ₂ film

At room temperature, in parts by weight, add 4.37% Ni(NO ₃ ) ₂ ·6H ₂ O and 12.12% Fe(NO ₃ ) ₃ ·9H ₂ O to 59% absolute ethanol, magnetically stir (120r/min) for 45min , use 5mol/L NaOH solution to adjust the pH value to 9, then add sepiolite wrapped with TiO ₂ film, stir (100r/min) for 30min, then react at 180°C for 21h, after cooling, solid-liquid Separation, washing with water, and finally drying at 70° C. to obtain the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst.

Example 2

A NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, the composition includes sepiolite, TiO ₂ and NiFe ₂ O ₄ , sepiolite is used as a carrier, TiO ₂ is wrapped on the surface of sepiolite in the form of a film, NiFe ₂ O ₄ is supported on the surface of TiO ₂ in the form of particles, in which the content of Ni is 1wt%, that of Fe is 1.9wt%, that of Ti is 12wt%, and the rest is sepiolite.

The preparation method of the above-mentioned NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst comprises the following steps:

(1) Pretreatment of sepiolite

Crush the sepiolite into powder, soak it in dilute nitric acid with a concentration of 10% for 15 hours, filter it, rinse it with water until neutral, then dry it, then put it in a muffle furnace and calcinate it at 450°C for 3 hours, rinse it with water And the sepiolite floating in the upper part of the water body is filtered out, and after drying, the sepiolite powder with a particle size of 112 meshes is sieved as a carrier;

(2) Preparation of TiO ₂ sol

At room temperature, in parts by volume, fully dissolve 15% butyl titanate in 45% absolute ethanol, then add 5% acetylacetone to obtain solution A, and fully mix 0.75% distilled water and 20% absolute ethanol to obtain a solution B. Gradually add solution B to solution A under the condition of constant stirring, then adjust the pH value to 5 with concentrated nitric acid, stir (120r/min) for 1h, add 1.5 polyethylene glycol, and then Under the condition of stirring (80r/min) 1.2h, obtain yellow transparent _TiO sol, _TiO sol is aged at room temperature for 15h;

(3) Coating TiO ₂ film on the surface of sepiolite

The number of layers of TiO ₂ film is 1 layer, and the formation method of each layer of TiO ₂ film is: at room temperature, add sepiolite to TiO ₂ sol, stir (100r/min) for 1.5h to make sepiolite and TiO ₂ sol Mix completely, and then dry at 80°C. During the drying process, first steam in a water bath until it is nearly dry, then dry in a drying oven, and finally place it in a muffle furnace for calcination at 450°C for 2 hours, and cool it for later use;

(4) Loading NiFe ₂ O ₄ particles on the surface of TiO ₂ film

At room temperature, by weight, 2.91 Ni(NO ₃ ) ₂ ·6H ₂ O and 8.08 Fe(NO ₃ ) ₃ ·9H ₂ O were added to 55.3% absolute ethanol, magnetically stirred (80r/min) for 30min , use 15mol/L NaOH solution to adjust the pH value to 10, then add sepiolite wrapped with TiO ₂ film, stir (120r/min) for 60min, then react at 160°C for 24h, cool and perform solid-liquid Separation, washing with water, and finally drying at 85° C. to obtain the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst.

Example 3

A NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, the composition includes sepiolite, TiO ₂ and NiFe ₂ O ₄ , sepiolite is used as a carrier, TiO ₂ is wrapped on the surface of sepiolite in the form of a film, NiFe ₂ O ₄ is supported on the surface of TiO ₂ in the form of particles, in which the content of Ni is 2wt%, that of Fe is 3.8wt%, that of Ti is 18wt%, and the rest is sepiolite.

The preparation method of the above-mentioned NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst comprises the following steps:

(1) Pretreatment of sepiolite

Grind sepiolite into powder, soak in dilute nitric acid with a concentration of 15% for 24 hours, filter, rinse with water until neutral, then dry, then place in a muffle furnace for calcination at 500°C for 2 hours, rinse with water And the sepiolite floating in the middle and upper part of the water body is filtered out, and after drying, the sepiolite powder with a particle size of 125 objects is sieved as a carrier;

(2) Preparation of TiO ₂ sol

At room temperature, in parts by volume, fully dissolve 20% butyl titanate in 50% absolute ethanol, then add 6% acetylacetone to obtain solution A, and fully mix 1.0% distilled water and 23% absolute ethanol to obtain a solution B. Gradually add solution B to solution A under the condition of constant stirring, then adjust the pH value to 4.5 with concentrated hydrochloric acid, stir (100r/min) for 2h, add 1 polyethylene glycol, and then Stirring (120r/min) for 1.5h under the condition to obtain a yellow transparent _TiO sol, the _TiO sol was aged at room temperature for 13h;

(3) Coating TiO ₂ film on the surface of sepiolite

The number of layers of the TiO ₂ film is 3 layers, and the formation method of each layer of TiO ₂ film is: at room temperature, add sepiolite to the TiO ₂ sol, stir (120r/min) for 1 hour to make the sepiolite and TiO ₂ sol completely Mix and then dry at 85°C. During the drying process, first steam in a water bath until nearly dry, then dry in a drying oven, and finally place it in a muffle furnace for calcination at 400°C for 3 hours, and cool it for later use;

(4) Loading NiFe ₂ O ₄ particles on the surface of TiO ₂ film

At room temperature, in parts by weight, add 5.82 g of Ni(NO ₃ ) ₂ ·6H ₂ O and 16.16 g of Fe(NO ₃ ) ₃ ·9H ₂ O into 63.2 g of absolute ethanol, and magnetically stir (100r/min) for 60 min , use 20mol/L NaOH solution to adjust the pH value to 9, then add sepiolite wrapped with TiO ₂ film, stir (80r/min) for 45min, then react at 170°C for 18h, cool and perform solid-liquid Separation, washing with water, and finally drying at 80° C. to obtain the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst.

Example 4

The NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst (hereinafter referred to as NiFe ₂ O ₄ /TiO ₂ /sepiolite) obtained in Example 1 of the present invention is subjected to electron microscope scanning, solid ultraviolet-visible spectrum test and infrared Spectrum test, the test results are shown in Figure 1, Figure 2 and Figure 3.

The left side of Fig. 1 is the scanning electron micrograph after wrapping TiO ₂ film on the surface of sepiolite in Example 1 of the present invention, and the right side is the scanning electron micrograph of NiFe ₂ O ₄ /TiO ₂ / sepiolite, as can be seen from Fig. 1 It can be seen that sepiolite becomes flakes after modification, and has a large surface area. TiO ₂ forms a film on the surface of sepiolite, and the surface of the TiO ₂ film is loaded with granular NiFe ₂ O ₄ , so the present invention is conducive to increasing the specific surface area. , adsorption performance and photocatalytic activity.

Among Fig. 2, a is the solid ultraviolet-visible spectrum figure of existing TiO ₂ /sepiolite supported photocatalyst (hereinafter referred to as TiO ₂ / sepiolite), b is NiFe ₂ O ₄ /TiO ₂ / sepiolite Solid ultraviolet-visible spectrum, as can be seen from Figure 2, TiO ₂ has a wider band gap (3.2eV), and the band gap of TiO ₂ / sepiolite is reduced to 3.18eV, while NiFe ₂ O ₄ /TiO ₂ / The bandgap of sepiolite is further reduced to 2.85eV, indicating that the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in the present invention has better catalytic activity for visible light, thereby improving the utilization efficiency of visible light . It can also be seen from Fig. 2 that the photoresponse range of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in the present invention has been extended to the visible light region.

In Figure 3, a is the infrared spectrum of sepiolite, b is the infrared spectrum of NiFe ₂ O ₄ /TiO ₂ /sepiolite, at 600-800cm ^-1 , NiFe ₂ O ₄ /TiO ₂ /sepiolite Compared with the infrared spectrum of sepiolite, the absorption peak at 668cm ^-1 becomes weaker, and the _external absorption peak of Si-O at 755cm ^-1 disappears, this is because the NiFe ₂ O ₄ /TiO ₂ /sepiolite Ti-O's sake. The intensity of the stretching vibration peak _within Si-O at ¹⁰²⁹ cm remains basically unchanged. The absorption peak of free OH at 3570cm ^-1 disappears, and the absorption peak of Si-O-Mg at 535cm ^-1 weakens, indicating that the magnesium in sepiolite may be replaced, which may increase the Si-O _{bridge inverted} -Si , resulting in more pores and larger adsorption capacity.

Example 5

Photocatalytic degradation of methylene blue solution effect test of NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention

Reaction initial conditions: the initial concentration of methylene blue is 50mg/L, the amount of catalyst is 0.4g, pH=5, it is subjected to a degradation experiment under the ultraviolet photocatalytic reactor, the degradation time is 60min, and samples are taken every 10min for visible light spectrophotometer measurement Its absorbance measures the methylene blue degradation efficiency. The test results are shown in Figure 4. It can be seen that the degradation efficiency of the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention can reach 85.56% in 60 minutes, while the existing TiO ₂ The degradation efficiency of sepiolite supported photocatalyst and CoFe ₂ O ₄ -TiO ₂ doped photocatalyst can only reach about 70% under the same conditions.

Example 6

Photocatalysts of the existing TiO ₂ /sepiolite supported photocatalyst, the existing CoFe ₂ O ₄ -TiO ₂ doped photocatalyst and the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention Comparison of Catalytic Degradation of Methylene Blue Solution

Experimental conditions: Catalyst dosage 1.0g, methylene blue initial concentration 4mg/L, pH=5, and the degradation experiment was carried out under the visible light catalytic reactor, the degradation time was 120min, the absorbance was measured by sampling every 20min, and the degradation efficiency of methylene blue was calculated. The test results are shown in Table 1. It can be seen from Table 1 that the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst obtained in Example 1 of the present invention has significantly better absorbance and degradation rate than the existing TiO ₂ /Sepiolite composite photocatalyst. Sepiolite supported photocatalyst and existing CoFe ₂ O ₄ -TiO ₂ doped photocatalyst, which shows that the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst of the present invention also has better photocatalysis under visible light However, the existing existing TiO ₂ /sepiolite-supported photocatalysts and existing CoFe ₂ O ₄ -TiO ₂ doped photocatalysts have extremely poor photocatalytic degradation effects under visible light, with almost no response.

Table 1

It should be understood that the examples and implementations described herein are for illustration only, and those skilled in the art can make various modifications or changes based on them, all of which belong to the protection scope of the present invention without departing from the spirit of the present invention.

Claims (4)

1. A NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst, characterized in that: the components include sepiolite, TiO ₂ and NiFe ₂ O ₄ , the sepiolite is the carrier, and the TiO ₂ is wrapped in the form of a film On the surface of sepiolite, NiFe ₂ O ₄ is supported on the surface of TiO ₂ in the form of particles. 2. NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst as claimed in claim 1, characterized in that: the content of Ni is 1-2wt%, the content of Fe is 1.9-3.8wt%, the content of Ti The content is 12-18wt%, and the remainder is sepiolite. 3. NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst as claimed in claim 2, characterized in that: the content of Ni is 1.5wt%, the content of Fe is 2.8wt%, and the content of Ti is 15wt% , the remainder is divided into sepiolite. 4. the preparation method of NiFe ₂ O ₄ /TiO ₂ / sepiolite composite photocatalyst as described in any one in claim 1 to 3, comprises the following steps: (1) Pretreatment of sepiolite Pulverize sepiolite into powder, soak in dilute nitric acid with a concentration of 5-15% for 15-24 hours, filter, rinse with water until neutral, dry, and then calcinate at 400-500°C for 2-4 hours, Rinse with water and filter out the sepiolite floating in the upper part of the water body, and sieve the sepiolite powder with a particle size of 100-125 mesh as a carrier after drying; (2) Preparation of TiO ₂ sol At room temperature, in parts by volume, fully dissolve 15-20% butyl titanate in 40-50% absolute ethanol, then add 5-6% acetylacetone to obtain solution A, mix 0.75-1.0% distilled water and 20- 25% of absolute ethanol is fully mixed to obtain solution B, gradually add solution B to solution A under the condition of constant stirring, then adjust the pH value to 4-5 with concentrated nitric acid or concentrated hydrochloric acid, stir for 1-2h, add 1-1.5 polyethylene glycol, then stirred at 40-65°C for 1-1.5h to obtain a yellow and transparent TiO ₂ sol, and aged the TiO ₂ sol at room temperature for 12-15h; (3) Coating TiO ₂ film on the surface of sepiolite The number of layers of TiO ₂ film is 1-3 layers, and the formation method of each layer of TiO ₂ film is as follows: at room temperature, add sepiolite to TiO ₂ sol, stir until it is completely mixed with TiO ₂ sol, and then in 70-85 Dry under the condition of ℃, and finally calcined under the condition of 400-500℃ for 1-3h, cool down and set aside; (4) Loading NiFe ₂ O ₄ particles on the surface of TiO ₂ film At room temperature, in parts by weight, add 2.91-5.82 Ni(NO ₃ ) ₂ ·6H ₂ O and 8.08-16.16 Fe(NO ₃ ) ₃ ·9H ₂ O into 55.3-63.2 absolute ethanol, stir for 30 -60min, adjust the pH value to 9-10 with 5-20mol/L NaOH solution, then add sepiolite wrapped with TiO ₂ film, stir for 30-60min, then react at 160-180℃ for 18- After cooling for 24 hours, carry out solid-liquid separation, water washing, and finally dry at 70-85°C to obtain the NiFe ₂ O ₄ /TiO ₂ /sepiolite composite photocatalyst.