CN111266126A - Preparation method and application of sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst - Google Patents

Abstract

A sulfur-doped graphite-like phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst takes a sulfur-doped graphite-like phase carbon nitride nanosheet as a carrier, and graphene and ferroferric oxide particles are modified on the sulfur-doped graphite-like phase carbon nitride nanosheet. The preparation method comprises the steps of preparing the sulfur-doped graphite-phase carbon nitride nanosheet by high-temperature pyrolysis of thiourea, preparing the sulfur-doped graphite-phase carbon nitride-loaded graphene composite material by an impregnation method, and preparing the sulfur-doped graphite-phase carbon nitride-loaded graphene and ferroferric oxide composite photocatalyst material by an alkaline-thermal coprecipitation method. The composite magnetic photocatalyst has the advantages of high photocatalytic activity, good stability, easy recovery of magnetic force, simple preparation process, low cost and good safety. The composite magnetic photocatalyst can be used for treating wastewater containing various antibiotic drugs, and has the advantages of good stability and practicability, high efficiency, simple and convenient operation, low cost and high recycling value.

Description

Preparation method and application of sulfur-doped graphitic carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst

technical field

The invention belongs to the technical and application fields of functional composite photocatalysts, and relates to a graphite-like carbon nitride nanosheet composite photocatalyst and a preparation method and application thereof, in particular to a sulfur-doped graphitic carbon nitride nanosheet supported graphene Preparation method and application of composite magnetic photocatalyst with ferric oxide.

Background technique

In recent years, the problems of environmental water pollution and energy shortage have become increasingly prominent, and traditional environmental remediation technologies have gradually been unable to meet people's requirements. Therefore, finding a new type of high-efficiency and energy-saving environmental remediation technology has become one of the current research hotspots. In recent years, the research on photocatalytic advanced oxidation technology based on semiconductor catalysts has attracted attention from researchers all over the world due to its good effect, low cost and easy operation. Nanotechnology based on nano-semiconductor catalyst materials has also been developed rapidly. . With the renewal and development of high-efficiency visible light catalysts, visible light has a good application prospect as a light source to remove refractory organic matter in water.

At present, graphitic carbon nitride (gC ₃ N ₄ ) has been introduced into photocatalysis as a visible light catalyst due to its unique semiconductor band structure, excellent chemical stability, no metal components, simple preparation process and low price. field, it can be prepared by simple steps from some cheap precursors such as urea, thiourea, melamine, etc. At the same time, gC ₃ N ₄ has high thermal stability, acid and alkali resistance, strong electrical conductivity and suitable conduction band and valence band, which endow it with good photocatalytic performance. About gC ₃ N ₄ in the field of photocatalysis There are broad application prospects. However, the traditional methods commonly used for the preparation of graphitic carbon nitride have problems such as large bulk particles, small specific surface area, low crystallinity, and incomplete polymerization, which limit the application prospects of carbon nitride materials. Its preparation method can be further improved. At the same time, the graphite-like carbon nitride still has problems such as high photo-generated electron-hole recombination rate and difficult recovery of catalysts in the field of water treatment. Therefore, the research on the catalytic effect of composite modification using graphite-like carbon nitride, a cheap and environmentally friendly substance, is more in line with the purpose of photocatalytic technology to degrade environmental water pollutants.

Due to its high saturation magnetization and superparamagnetic properties, ferric oxide nanomaterials have been widely used in information storage, sensor design, medical targeted drug delivery, sewage treatment and other fields. Ferric oxide is used as a magnetic carrier to combine many semiconductor photocatalysts, such as titanium dioxide/ferric oxide, zinc oxide/ferric oxide, etc. Through the study of the properties of the composite catalyst, it was found that the successfully composited composite catalyst material not only has magnetic properties, but also has stronger photocatalytic performance in the degradation of organic pollutants in water. The emergence of this phenomenon is due to the fact that the ferric oxide material has both high electrical conductivity and suitable energy band structure, which can improve the separation and transport of photogenerated electron-hole pairs and reduce the photo-generated electron-hole recombination rate. Graphene is widely used in capacitors and semiconductor composite materials due to its special two-dimensional honeycomb structure and excellent mechanical thermal, optical, and electronic conductivity. At the same time, its high specific area and relatively low production cost make it have a good prospect in compounding with semiconductor photocatalyst as an intermediate.

Therefore, the purpose of this work is to combine the three materials of graphitic phase carbon nitride and graphene and iron tetroxide into composite photocatalyst materials, in order to improve the photocatalytic performance and recyclable durability of semiconductor photocatalysts, which have important research significance.

SUMMARY OF THE INVENTION

The object of the present invention is to aim at the deficiencies of the prior art, and to provide a kind of sulfur-doped graphitic carbon nitride nanosheet-loaded graphene and ferric tetroxide composite magneto-optical light with high photocatalytic activity, good stability and easy recycling. Catalyst preparation method and application in antibiotic degradation. The visible light semiconductor catalyst material to be prepared in this technology is a crystalline substance with nano-scale particle size, which can be uniformly distributed and stable in an aqueous solution. The technology is simple in process, wide in raw materials and low in cost, meets actual production needs, and has great potential for industrial application in semiconductor catalyst materials, solar energy, and water treatment to degrade organic matter.

To achieve the above object, the present invention adopts the following technical solutions:

A sulfur-doped graphitic-like carbon nitride nanosheet supported graphene and ferric oxide composite magnetic photocatalyst, comprising sulfur-doped graphitic carbon nitride nanosheets, graphene and ferric oxide particles; the The single-layer graphene is attached to the surface of the sulfur-doped graphitic carbon nitride nanosheet to form a graphene-supported sulfur-doped graphitic carbon nitride nanosheet composite; the ferric oxide particles are attached to the The surface of the graphene-supported sulfur-doped graphitic-like carbon nitride nanosheet composites forms a composite of ferric oxide and graphene-supported sulfur-doped graphitic-like carbon nitride nanosheets.

In the above-mentioned sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst, preferably, the single-layer graphene is attached to the sulfur-doped graphitic phase nitride by dipping and dispersion method. On the surface of carbon nanometers, the mass ratio of the monolayer graphene to the sulfur-doped graphitic carbon nitride nanosheets is 1:(500-1000); The sulfur-doped graphite-like carbon nitride nano-layers and the surface have a mass ratio of the ferric oxide particles to the sulfur-doped graphite-like carbon nitride nanosheets of 1:(5-20).

As a general technical concept, the present invention provides a preparation method of the above-mentioned sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst, comprising the following steps:

S1. Using thiourea as a precursor, heating for a certain period of time in a special device and a high temperature environment, and obtaining sulfur-doped carbon nitride nanosheets after screening, grinding and sieving.

S2, mixing the graphene oxide solution with the sulfur-doped carbon nitride nanosheets obtained in step S1, and performing ultrasonic dispersion to obtain a graphene composite photocatalyst supported by sulfur-doped graphitic carbon nitride nanosheets.

S3, disperse and mix the ferrous chloride and the ferric chloride solution and the sulfur-doped carbon nitride nanosheet-supported graphene composite photocatalyst obtained in the step S2, and heat in a water bath, and then add ammonia water to realize alkali-heat co-precipitation to obtain Sulfur-doped graphitic carbon nitride nanosheets supported graphene and ferric oxide composite magnetic photocatalyst.

In the above preparation method, preferably, the preparation method of the sulfur-doped graphitic carbon nitride nanosheets includes the following steps:

(1) Precursor preparation: Weigh 20-30 grams of thiourea, thiourea does not need any pretreatment;

(2) Calcination: Two crucibles of 40 ml and 100 ml are prepared, and the thiourea mentioned in step (1) is placed in a small crucible of 40 ml. Then place the 40 ml crucible in the 100 ml crucible, as shown in Figure 1. Then, cover the 100-ml crucible with a lid, wrap the crucible and the lid with tin foil to fix it, and finally put it into a muffle furnace for heating and calcination.

(3) Programmatic heating step setting: from room temperature, the heating program is set at a heating rate of 2 to 3 degrees Celsius per minute, and the temperature is raised to 550 degrees Celsius for 3-4 hours for calcination, and the calcination process does not require any inert protective gas.

(4) After the calcination and heat preservation is completed, it is naturally cooled to room temperature. Open the crucible, and the beige substance attached to the lid of the 100 ml crucible and the inner wall of the pot is the target material, sulfur-doped graphite-like carbon nitride nanosheets, which are ground and sieved with 300 mesh.

In the above preparation method, preferably, the preparation method of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene composite photocatalyst comprises the following steps:

(1) Add the graphene dispersion to the mixed solution of ethanol and water, and stir for 0.5 to 1 hour

(2) adding sulfur-doped graphite-like carbon nitride nanosheets to the obtained dispersion, stirring the mixture solution for 0.5 to 1 hour, and then ultrasonically dispersing for 0.5 to 1 hour to obtain sulfur-doped carbon nitride nanosheet-supported graphene Composite photocatalyst suspension.

(3) After collecting by centrifugation, washing and drying, the sample sulfur-doped carbon nitride nanosheet-supported graphene composite photocatalyst was obtained.

In the above-mentioned preparation method of sulfur-doped graphitic carbon nitride nanosheet-supported graphene composite photocatalyst, preferably, in the step (1), the volume ratio of ethanol to water in the ethanol and water mixed solution is 1 :(1～2);

And/or, in the step (2), the mass ratio of the graphene dispersion to the sulfur-doped graphitic carbon nitride nanosheets is 1: (500-1000), and the sulfur-doped graphitic nitrogen is The mass volume ratio of the carbonized nanosheet to the ethanol and water solution is 1 g: (50-60) ml;

And/or, in the step (3), the drying temperature of the sulfur-doped carbon nitride nanosheet-supported graphene composite photocatalyst is 60-70 degrees Celsius, and the drying time is 7-8 hours.

In the above-mentioned preparation method, preferably, the preparation method of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst comprises the following steps:

(1) Dissolving ferric chloride and ferric dichloride tetrahydrate in distilled water, and adding them to the sulfur-doped graphite-like carbon nitride nanosheet-supported graphene composite photocatalyst suspension.

(2) The mixed solution is heated and stirred for 30 to 40 minutes, then ammonia water is quickly added to the mixed solution and stirred continuously for 30 to 40 minutes, and then the solution is allowed to cool naturally.

(3) The prepared precipitate was collected by centrifugation, washed alternately with ethanol and water for 2-3 times, and dried in an oven for 10 hours.

In the above-mentioned preparation method of sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst, preferably, in the step (1), the ferric chloride and tetrahydrate chlorine The mass ratio of ferrous chloride is (1.6～1.8): 1; The mass volume ratio of described ferric chloride and distilled water is 1 g: (80～650) milliliters; Described ferric chloride and sulfur doping The mass ratio of the graphite-like carbon nitride nanosheets is 1:(2～13); the mass ratio of the generated ferric oxide particles to the sulfur-doped graphite-like carbon nitride nanosheets is 1:(5～20 ).

And/or, in the step (2): the heating temperature is 80-85 degrees Celsius;

And/or, in the step (2): the ammonia water is generally 5-10 milliliters;

And/or, in the step (3): the temperature of the oven is set to 60-70 degrees Celsius.

As a general technical concept, the present invention also provides an application of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst prepared by the above preparation method in the treatment of antibiotic wastewater , comprising the following steps: mixing sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene, ferric tetroxide composite magnetic photocatalyst and antibiotic wastewater to carry out photocatalytic reaction to complete the treatment of antibiotic wastewater.

In the above application, preferably, the addition of the sulfur-doped graphitic carbon nitride nanosheet-loaded graphene and the ferric oxide composite magnetic photocatalyst is the addition of the sulfur-doped photocatalyst per liter of the antibiotic wastewater. Graphite-like carbon nitride nanosheet supported graphene and ferric oxide composite magnetic photocatalyst 0.2 g to 1.5 g;

And/or, the antibiotics in the antibiotic wastewater are ranitidine and oxytetracycline; the initial concentration of the antibiotics in the antibiotic wastewater is 2-20 mg per liter;

And/or, the light source of the photocatalytic reaction is a xenon lamp;

And/or, the time of the photocatalytic reaction is 0.8 to 1 hour.

Compared with the prior art, the advantages of the present invention are:

1. The present invention provides a composite magnetic photocatalyst of sulfur-doped graphitic carbon nitride nanosheets loaded with graphene and iron tetroxide, using sulfur-doped graphitic carbon nitride nanosheets as a carrier, and sulfur-doped Graphene-like carbon nitride nanosheets are decorated with graphene and ferric oxide particles. First of all, the present invention adopts sulfur-doped graphite-like carbon nitride nanosheets, and the doping of sulfur can improve the absorption ability and electron conduction ability of graphitic-like carbon nitride in visible light, and can further improve the graphitic-like nitrogen The photocatalytic effect of carbonized materials; at the same time, the graphene composite catalyst supported by sulfur-doped graphitic carbon nitride nanosheets of the present invention, the loading of graphene further increases the specific surface area, which can promote the material to provide more active sites The contact between the catalyst material and the reactant is more sufficient, and the transfer of photogenerated electrons on the semiconductor surface is more favorable, and the recombination rate of photogenerated electrons and holes is reduced, thereby improving the photocatalytic efficiency. Secondly, in the present invention, the ferric oxide particles are supported on the sulfur-doped graphitic carbon nitride nanosheets, and the heterojunction is formed due to the close combination of the ferric oxide particles and the sulfur-doped graphitic carbon nitride nanosheets. It is beneficial to the separation of photogenerated electrons and holes, reducing the recombination of photogenerated electrons and holes, thereby improving the photocatalytic performance of the material. At the same time, due to the addition of ferric oxide, the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst has magnetic properties, which improves its effective separation and reuse performance, and strengthens its performance in Applications in the field of water treatment.

2. The present invention also provides a method for preparing a sulfur-doped graphitic carbon nitride nanosheet-loaded graphene and iron tetroxide composite magnetic photocatalyst. Using iron and ferric chloride as raw materials, sulfur-doped graphitic carbon nitride nanosheets were prepared by a muffle furnace programmed high temperature method, and graphene was attached to the sulfur-doped graphitic carbon nitride nanosheets by dipping. On the surface, a graphene composite photocatalyst supported by sulfur-doped carbon nitride nanosheets was prepared. The sulfur-doped carbon nitride nanosheet-supported graphene composite photocatalyst was supported on the surface of the sulfur-doped carbon nitride nanosheet-supported graphene composite photocatalyst by the alkali-heat co-precipitation method, and the sulfur-doped graphitic phase carbon nitride nanosheet-supported graphene and ferric oxide were prepared. Iron composite magnetic photocatalyst. The whole process steps of the invention are simple and easy to implement, all are carried out under normal pressure conditions, the equipment requirements are low, and high pressure operation reactors such as a reaction kettle are not required, thereby reducing the risk of experiments. At the same time, the raw materials used in the method are common cheap chemicals, do not use any dangerous chemicals, and have the characteristics of safety and low cost. Therefore, compared with other methods, the preparation method of the present invention has the advantages of simple operation, low cost, high safety factor, low energy consumption and the like.

3. The preparation of sulfur-doped graphite-like carbon nitride nanosheets described in the present invention uses thiourea as a precursor. Due to the special element composition of thiourea, the graphite-like carbon nitride prepared at high temperature will contain A small amount of sulfur doping, the doping of sulfur element can improve the absorption capacity and electron conductivity of graphitic carbon nitride in visible light, and can further improve the photocatalytic effect of graphitic carbon nitride material; at the same time, thiourea During the high temperature pyrolysis process, ammonia gas will be released, and the ammonia gas will pass through the surface of the material during the release process, causing the surface of the material to be uneven and increasing the specific surface area of carbon nitride. At the same time, the ammonia gas will bring out the target material in the process of rising, and these materials will be uniformly dispersed around the pot wall through the special stacking device of the crucible. carbon nanosheets.

4. The present invention also provides a method for treating antibiotic wastewater. The prepared sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst are added into wastewater containing antibiotics, and the photocatalytic reaction is carried out under the irradiation of visible light, under conventional conditions. It has a good effect on the degradation of antibiotics in a certain period of time. At the same time, the magnetic catalyst has the characteristics of simple use of the green ring, low cost, good recyclability, high stability, easy separation and the like.

Description of drawings

FIG. 1 is a schematic diagram of the placement position of the crucible during the preparation of the sulfur-doped graphitic carbon nitride material in the embodiment of the present invention.

FIG. 2 is a graph showing sulfur-doped graphitic carbon nitride nanosheets (gC ₃ N ₄ ) and sulfur-doped graphitic carbon nitride nanosheets loaded with different mass fractions of ferric oxide in an embodiment of the present invention XRD patterns of the composite magnetic photocatalyst (x%-Fe ₃ O ₄ /GE/CN) with ferric oxide and graphene (Graphene) and ferric oxide particles (Fe ₃ O ₄ ).

3 is a scanning electron microscope image of a sulfur-doped graphitic carbon nitride nanosheet and a sulfur-doped graphitic carbon nitride nanosheet supported graphene and iron tetroxide composite magnetic photocatalyst in the embodiment of the present invention; wherein a , b are sulfur-doped graphitic carbon nitride nanosheets, c, d are sulfur-doped graphitic carbon nitride nanosheets supported graphene and ferric oxide composite magnetic photocatalysts.

FIG. 4 is a graph showing sulfur-doped graphitic carbon nitride nanosheets (gC ₃ N ₄ ) and sulfur-doped graphitic carbon nitride nanosheets with different mass fractions of ferric oxide containing graphene supported in the embodiment of the present invention Infrared spectrum FT-IR image of the composite magnetic photocatalyst (x%-Fe ₃ O ₄ /GE/CN) with ferric oxide.

FIG. 5 is an element distribution mapping diagram of a sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst in an embodiment of the present invention.

FIG. 6 is an ultraviolet-visible absorption spectrum (UV-Vis) diagram of a sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst in an embodiment of the present invention.

FIG. 7 is a graph showing the magnetic hysteresis loop of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst in the embodiment of the present invention.

FIG. 8 is a graph showing sulfur-doped graphitic carbon nitride nanosheets (gC ₃ N ₄ ) and graphene composite photocatalysts (0.1% wt-GE/ CN), sulfur-doped graphitic carbon nitride nanosheets supported ferric oxide composite photocatalyst (20%wt-Fe ₃ O ₄ /CN), sulfur-doped graphite-like carbon containing different mass fractions of ferric oxide During the photocatalytic degradation of phase carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (x%-Fe ₃ O ₄ /GE/CN) in the visible light region (wavelength λ>400 nm), Raney Schematic diagram of the relationship between the concentration of tidine and the photocatalytic time.

9 is a graph showing the photocatalyst (20%-Fe ₃ O ₄ /GE/CN) in the visible light region (wavelength λ Schematic diagram of the relationship between the concentration of ranitidine and the photocatalytic time during the photocatalytic degradation of ranitidine wastewater with different initial concentrations at >400 nm).

Figure 10 shows the use of different sulfur-doped graphitic phase carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) concentrations in visible light in the embodiment of the present invention Schematic diagram of the relationship between the concentration of ranitidine and the photocatalytic time during the photocatalytic degradation process in the region (wavelength λ>400 nm).

Fig. 11 is a graph showing the photocatalyst (20%-Fe ₃ O ₄ /GE/CN) in the visible light region (wavelength λ Schematic diagram of the relationship between the concentration of ranitidine and the photocatalytic time during the photocatalytic degradation of ranitidine wastewater with different pH and alkalinity at >400 nm).

Fig. 12 shows the photocatalyst (20%-Fe ₃ O ₄ /GE/CN) in the visible light region (wavelength λ Schematic diagram of the relationship between the concentrations of ranitidine and oxytetracycline as a function of photocatalytic time during the photocatalytic degradation of wastewater containing ranitidine and oxytetracycline at >400 nanometers.

Fig. 13 is a graph showing the photocatalyst (20%-Fe ₃ O ₄ /GE/CN) in the visible light region (wavelength λ >400 nm), a schematic diagram of the relationship between the concentration of ranitidine and the photocatalytic time during the photocatalytic degradation of ranitidine wastewater by repeated recycling.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments.

The raw materials and instruments used in the following examples are commercially available, wherein the light source system is a rotary photochemical reactor PhchemIIII, equipped with a 300-watt xenon lamp, purchased from Beijing Newbit Co., Ltd.

Example 1

In order to specifically prepare a composite magnetic photocatalyst (20%- Fe ₃ O ₄ /GE/CN) as an example, including sulfur-doped graphitic carbon nitride nanosheets, graphene dispersions (purchased commercially), and ferric oxide particles. The catalyst is based on sulfur-doped graphitic-like carbon nitride nanosheets as a carrier, and graphene and ferric oxide particles are decorated on the sulfur-doped graphitic-like carbon nitride nanosheets.

In this embodiment, the graphene and the ferric oxide particles are uniformly attached to the surface of the sulfur-doped graphitic carbon nitride nanosheets.

In this example, the graphene dispersion is supported and modified on the sulfur-doped graphitic carbon nitride nanosheets by dipping to form a sulfur-doped graphitic carbon nitride-supported graphene photocatalyst composite material, wherein graphene and The mass ratio of sulfur-doped graphitic carbon nitride nanosheets is 1:500;

In this example, the sulfur-doped graphitic phase carbon nitride supported graphite is formed by loading and decorating the ferric oxide particles on the sulfur-doped graphite-like carbon nitride-supported graphene photocatalyst composite material by means of alkali-thermal co-precipitation. A composite material of alkene and ferric oxide photocatalyst, wherein the mass ratio of ferric oxide and sulfur-doped graphitic carbon nitride nanosheets is 1:5;

A preparation method of the sulfur-doped graphitic phase carbon nitride nanosheet-loaded graphene and ferric oxide composite magnetic photocatalyst composite material of the present embodiment, comprising the following steps:

(1) Precursor preparation: weigh 20 grams of thiourea, thiourea does not need any pretreatment;

(2) Calcination: Two crucibles of 40 ml and 100 ml are prepared, and the thiourea mentioned in step (1) is placed in a small crucible of 40 ml. Then place the 40 ml crucible in the 100 ml crucible, as shown in Figure 1. Then, cover the 100-ml crucible with a lid, wrap the crucible and the lid with tin foil to fix it, and finally put it into a muffle furnace for heating and calcination.

(3) Programmatic heating step setting: from room temperature, the heating program is set at a heating rate of 2 degrees Celsius per minute, and the temperature is raised to 550 degrees Celsius for 4 hours for calcination. The calcination process does not require any inert protective gas.

(4) After the calcination and heat preservation is completed, it is naturally cooled to room temperature. Open the crucible, the beige substance attached to the 100 ml crucible lid and the inner wall of the pot is the target material sulfur-doped graphite-like carbon nitride nanosheets, which are then ground and sieved with 300 mesh to obtain sulfur-doped graphite-like carbon nitride. carbon nanosheets.

(5) Take 0.1 ml (ie 0.4 mg) of graphene dispersion (concentration is 4 mg per ml, commercially available) and add it to 100 ml of absolute ethanol/water (V ₁ /V ₂ =1:1) mixed solution, Stir at 600 rpm for 0.5 hours

(6) Add 0.2 g of the sulfur-doped graphitic carbon nitride nanosheets obtained in step (4) to the dispersion obtained in step (5), stir the mixture solution at 600 rpm for 0.5 hours, and then ultrasonically disperse 0.5 hours, a sulfur-doped graphitic-like carbon nitride-supported graphene composite photocatalyst suspension was prepared.

(7) 0.07 g of ferric chloride and 0.042 g of ferrous chloride tetrahydrate were dissolved in 10 ml of deionized water, and added to the suspension in step (6). The mixed solution was stirred at 600 rpm for 30 minutes at 80 degrees Celsius, then 10 ml of ammonia water was quickly added to the mixed solution and continued stirring at 600 rpm for 30 minutes, and finally the solution was allowed to cool naturally. (Supplementary step (7): preparation of sulfur-doped graphitic carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalysts containing different mass fractions of ferric oxide (5-30%), only by adding Different quality of ferric chloride and ferrous chloride tetrahydrate are completed, the specific quality required, see the table below.)

Table 1 The amount of materials prepared by Fe ₃ O ₄ /GE/CN with different mass fractions

(8) The prepared precipitate was collected by centrifugation, washed 3 times alternately with deionized water and absolute ethanol, and air-dried at 60 degrees Celsius for 10 hours. After drying, it was ground and sieved through a 300-mesh sieve, and finally the obtained The sulfur-doped graphite-like carbon nitride nanosheet supports graphene and ferric oxide composite magnetic photocatalyst.

Material Characterization 1: X-ray Diffraction Spectroscopy (XRD)

The sulfur-doped graphitic-like carbon nitride nanosheets prepared in Example 1 supported graphene and ferric oxide composite magnetic photocatalyst (Fe ₃ O ₄ /GE/CN), sulfur-doped graphitic carbon nitride The nanosheets (gC ₃ N ₄ ), graphene (Graphene) and iron tetroxide particles (Fe ₃ O ₄ ) were analyzed by X-ray energy dispersive spectrometer (XRD) respectively, and the results are shown in FIG. 2 . It can be seen from Figure 2 that the sulfur-doped graphitic carbon nitride nanosheets (gC ₃ N ₄ ) prepared in Example 1 show typical carbon nitride diffraction peaks, and the graphene is amorphous and amorphous. There are no fixed standard characteristic peaks, the Fe3O4 particles (Fe ₃ O ₄ ) show typical Fe3O4 diffraction peaks, containing sulfur-doped graphitic carbon nitride nanosheets with different Fe3O4 mass fractions The supported graphene and ferric oxide composite magnetic photocatalyst (Fe ₃ O ₄ /GE/CN) exhibited diffraction peaks similar to those of graphitic carbon nitride nanosheets, and also included characteristic peaks of ferric oxide. It shows that the loading of graphene and different mass fractions of ferric oxide does not change the crystal structure of graphitic carbon nitride nanosheets, which is of great significance for maintaining the excellent photocatalytic performance of the composites.

Material Characterization 2: Material Surface Morphology Observation (SEM)

The sulfur-doped graphitic phase carbon nitride nanosheets and the sulfur-doped graphitic phase carbon nitride nanosheets supported graphene and iron tetroxide composite magnetic photocatalysts in Example 1 were respectively subjected to scanning electron microscope SEM analysis, and the results were as follows As shown in Figure 3, (a)(b) are sulfur-doped graphitic carbon nitride nanosheets, (c)(d) are sulfur-doped graphitic carbon nitride nanosheets supported by graphene and trioxide Iron composite magnetic photocatalyst. It can be seen from Figure 3 that (a) (b) pure sulfur-doped graphite-like carbon nitride nanosheets exhibit a typical sheet-like structure and smooth surface; in contrast, (c) (d) sulfur-doped graphite-like carbon nanosheets Phase carbon nitride nanosheets supported graphene and ferric oxide composite magnetic photocatalyst with more ferric oxide particles distributed on the surface, and well dispersed on the surface of sulfur-doped graphitic carbon nitride nanosheets And around, while making the material magnetic, the surface of the material is rough and uneven, thereby increasing the specific surface area of the material. The large specific surface area can provide more active sites and adsorb more pollutants, thereby promoting the photocatalytic reaction. conduct.

Material Characterization 3: Fourier Transform Infrared Transform Spectroscopic Characterization (FT-IR)

The sulfur-doped graphitic phase carbon nitride nanosheets and the sulfur-doped graphitic phase carbon nitride nanosheets supported graphene and iron tetroxide composite magnetic photocatalysts in Example 1 were respectively subjected to infrared absorption spectrum FT-IR analysis . The results are shown in Figure 4. The positions of the characteristic peaks of several materials are not significantly different, indicating that the materials have the same molecular structure. The characteristic peak at 812 cm ^{-1 is due to the stretching vibration of the triazine ring unit; several characteristic peaks at 1250-1600 cm -1 are} mainly due to the C ₆ N ₇ ring in the graphitic phase carbon nitride nanosheet structural unit Stretching vibration of ; this result indicates that the loading of graphene and different mass fractions of ferric oxide does not change the crystal structure of graphitic carbon nitride nanosheets, which is of great significance for maintaining the excellent photocatalytic performance of the composites.

Material Characterization 4: Semi-quantitative Analysis of Material Element Content (EDX and Mapping)

EDX elemental analysis and Mapping elemental distribution analysis were performed on the sulfur-doped graphitic phase carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst in Example 1, respectively, and the results are shown in the table. According to the EDX line scan results of the element energy spectrum, five elements of carbon, nitrogen, oxygen, sulfur and iron were detected in the modified composite material, and the contents are shown in Table 2 below:

Table 2 EDX element analysis table

element weight(%) atom(%) carbon 42.57 49.14 nitrogen 45.15 44.68 oxygen 5.06 4.38 sulfur 0.04 0.02 iron 7.18 1.78 total 100.00 100.00

Compared with the pure graphite-like carbon nitride nanosheets, the detection of the indicated elements indicates that the material is successfully compounded with iron tetroxide and graphene as a carrier. According to the element distribution Mapping diagram in Figure 5, after compounding, the three composite elements of oxygen, sulfur and iron are evenly distributed in the interlayer or surface of the carbon nitride nanosheets, which is very important for maintaining the excellent photocatalytic performance of the composite material. Significance.

Material Characterization 5: Material UV-Vis Absorption Spectroscopy (UV-Vis)

The catalytic activity of photocatalysts is closely related to the light absorption capacity. Therefore, the light absorption properties of the samples investigated by UV-Vis absorption spectroscopy are shown in Figure 6. The absorption edge of the sulfur-doped graphitic carbon nitride nanosheet samples is 450 nm, indicating the photocatalytic activity under visible light irradiation. While adding _Fe3O4 to the _samples further increased the visible light absorption and enhanced the absorption intensity. _The higher light absorption of the composites can be attributed to the intercalation effect of _Fe3O4 nanoparticles, which causes the inner space between the layers to absorb reflected light multiple times and thus increase the absorbance. Higher light absorption performance can absorb more photons and promote the photocatalytic reaction.

Material Characterization 6: Magnetic Verification of Composite Catalysts (VSM Hysteresis Curve)

The hysteresis loop curve VSM analysis of the sulfur-doped graphitic phase carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst in Example 1 is shown in FIG. 7 . The hysteresis loops of the 5%-Fe ₃ O ₄ /GE/CN and 20%-Fe ₃ O ₄ /GE/CN samples both show that they are superparamagnetic and have no obvious remanence. At the same time, the degree of magnetization of the composite material is proportional to the proportion of Fe ₃ O ₄ . The smaller the proportion of Fe ₃ O 4 is, the smaller the magnetization intensity is. At the same time, according to Fig. 7(a), the composite photocatalyst is uniformly distributed in the aqueous solution in the experiment. Under the action of an external magnet, the material can be separated from the water within 2 minutes, as shown in Fig. 7(b). Good magnetism enhances the performance of material recovery and recycling, reduces costs on the basis of high efficiency, and strengthens the application of this material in water treatment and other fields.

Example 2

An application of a sulfur-doped graphitic-like carbon nitride nanosheet-loaded graphene and ferric tetroxide composite magnetic photocatalyst in the treatment of ranitidine antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and then placed in a photocatalytic reaction device for 30 minutes at a rate of 500 rpm in a dark and dark environment.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 8 .

(3) A group of 5 mg per liter ranitidine wastewater without any catalyst was set as a blank control. In addition, 50 mg of sulfur-doped graphitic carbon nitride nanosheets (gC ₃ N ₄ ), sulfur Doped graphitic-like carbon nitride nanosheet-supported graphene composite photocatalyst (0.1%-GE/CN), ferric oxide particle-supported graphene composite (0.1%-GE/Fe ₃ O ₄ ), sulfur doping Graphite-like carbon nitride nanosheets supported ferric oxide composite photocatalyst (20%-Fe ₃ O ₄ /CN), and other sulfur-doped graphitic-like carbon nitride nanosheets supported by different mass fractions of ferric oxide The graphene and ferric oxide composite magnetic photocatalyst (X%-Fe ₃ O ₄ /GE/CN) was supported, and the above steps of photocatalytic degradation of ranitidine wastewater were repeated, and the results were shown in FIG. 8 .

(4) It can be seen from FIG. 8 that the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst invented in Example 1 can remove ranitidine within 60 minutes. The photocatalytic degradation efficiency was significantly improved compared with the blank group (2.83%) and the sulfur-doped graphite-like carbon nitride nanosheet (gC ₃ N ₄ ) group (31.78%). It can be seen that, compared with the control group, the sulfur-doped graphitic carbon nitride nanosheet-loaded graphene and iron tetroxide composite magnetic photocatalyst of the present invention has better performance than the pure sulfur-doped graphitic carbon nitride nanosheets. High photocatalytic activity, that is, the composite photocatalyst of the present invention has faster catalytic efficiency and better removal effect for the antibiotic ranitidine.

Example 3

An application of a sulfur-doped graphitic-like carbon nitride nanosheet-loaded graphene and ferric tetroxide composite magnetic photocatalyst in the treatment of ranitidine antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and then placed in a photocatalytic reaction device for 30 minutes at a rate of 500 rpm in a dark and dark environment.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 9 .

(3) In addition, the ranitidine wastewater with initial concentrations of 2, 10, and 15 mg per liter was prepared respectively, and the above-mentioned photocatalytic degradation step of the ranitidine wastewater was repeated. The results are shown in FIG. 9 .

(4) As can be seen from FIG. 9 , for the ranitidine wastewater with an initial concentration of 2 mg per liter, the sulfur-doped graphitic phase carbon nitride nanosheet-loaded graphene and ferric tetroxide invented in Example 1 were composited The magnetic photocatalyst can completely remove ranitidine within 60 minutes. With the increase of the initial concentration of ranitidine, the reaction time required for degradation increases, and the final removal rate decreases. This is mainly due to a certain amount of catalyst, a certain number of reaction active sites provided, and the higher the pollutant concentration, the longer the time required for complete removal.

Example 4

An application of a sulfur-doped graphitic-like carbon nitride nanosheet-loaded graphene and ferric tetroxide composite magnetic photocatalyst in the treatment of ranitidine antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and then placed in a photocatalytic reaction device for 30 minutes at a rate of 500 rpm in a dark and dark environment.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 10 .

(3) In addition, weigh 10, 25, and 75 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O) prepared in Example 1, respectively. ₄ /GE/CN), added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and repeated the above steps of photocatalytic degradation of ranitidine wastewater. The results are shown in Figure 10.

(4) It can be seen from Fig. 10 that the reaction time required for degradation and the final removal rate vary with the concentration of the added composite photocatalyst. Within the scope of this embodiment, with the increase of the catalyst concentration, the rate and efficiency of the degradation reaction also increase. This is mainly because the concentration of pollutants is constant. With the increase of the catalyst, the number of reaction active sites provided. It also increases, and the higher the catalyst concentration added, the higher the degradation rate and efficiency.

Example 5

An application of a sulfur-doped graphitic-like carbon nitride nanosheet-loaded graphene and ferric tetroxide composite magnetic photocatalyst in the treatment of ranitidine antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter at pH 3 (pH was adjusted with 0.1 mol per liter of hydrochloric acid and sodium hydroxide), and then placed in a photocatalytic reaction device in the dark. Stir at 500 rpm for 30 minutes under light.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 11 .

(3) In addition, adjust the pH of 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter to be 5, 7, 9, and 11, repeat the above-mentioned photocatalytic degradation step of ranitidine wastewater, and the results are shown in Figure 11. Show.

(4) It can be seen from Figure 11 that with the different pH of ranitidine wastewater, the rate of degradation and the final removal rate are also different. Within the scope of this example, when the pH of the ranitidine wastewater is 3 and 11 in an acidic or alkaline environment, the catalyst prepared in Example 1 has a low degradation efficiency to ranitidine. When the ranitidine wastewater was in a pH neutral environment such as 5, 7, and 9, the catalyst prepared in Example 1 had better degradation efficiency to ranitidine, and this environment was more in line with the actual utilization scenario.

Example 6

An application of a sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst in the treatment of ranitidine and oxytetracycline antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and then placed in a photocatalytic reaction device for 30 minutes at a rate of 500 rpm in a dark and dark environment.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 12 .

(3) Weigh 50 mg of the sulfur-doped graphite-like carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of oxytetracycline wastewater with an initial concentration of 5 mg per liter (in addition, 0.1 mol per liter of hydrochloric acid and sodium hydroxide was used to adjust the pH of the oxytetracycline solution to 7), and then placed in a photocatalytic reaction device. Stir at 500 rpm for 30 minutes in the dark and protected from light.

(4) Use the above-mentioned 300W xenon lamp as the light source, and use the cut-off filter below 400 nm to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nm) for 60 minutes, and the soil mold in the wastewater is completed. element processing. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the concentration of oxytetracycline in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of oxytetracycline at different light times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial oxytetracycline concentration at time 0), the results are shown in Figure 11 .

(4) It can be seen from FIG. 12 that the sulfur-doped graphitic phase carbon nitride nanosheet-supported graphene and iron tetroxide composite magnetic photocatalyst invented in Example 1 can remove ranitidine within 60 minutes. The rate can reach 80.23%, and the oxytetracycline solution of 5 mg per liter can be completely removed within 60 minutes. It can be seen that the sulfur-doped graphitic phase carbon nitride nanosheet supported graphene and ferric oxide composite magnetic properties of the present invention The photocatalyst has a good removal effect on many different kinds of antibiotics.

Example 7

The recycling stability of a sulfur-doped graphitic-like carbon nitride nanosheet-supported graphene and ferric tetroxide composite magnetic photocatalyst in the treatment of ranitidine antibiotic wastewater, comprising the following steps:

(1) Weigh 50 mg of the sulfur-doped graphitic carbon nitride nanosheet-supported graphene and ferric oxide composite magnetic photocatalyst (20%-Fe ₃ O ₄ /GE/CN) prepared in Example 1, It was added to 50 ml of ranitidine wastewater with an initial concentration of 5 mg per liter, and then placed in a photocatalytic reaction device for 30 minutes at a rate of 500 rpm in a dark and dark environment.

(2) The above-mentioned 300-watt xenon lamp is used as the light source, and the cut-off filter below 400 nanometers is used to ensure that the photocatalytic reaction of ranitidine and the composite photocatalyst is carried out in the visible light region (wavelength λ>400 nanometers) for 60 minutes, and the reaction of lightning in the wastewater is completed. Treatment of nitidine. The sampling time for judging the progress of the photocatalytic reaction is set as 0, 2, 5, 10, 15, 20, 30, 40, 50, 60 minutes in the progress of the reaction, and a liquid chromatograph is used to measure the ranitidine in the solution at this time. The peak area absorbance value, combined with the standard curve, obtained the corresponding concentration C of ranitidine at different illumination times. Taking time t as the ordinate and C/C ₀ as the ordinate (where C ₀ is the initial ranitidine concentration at time 0), the results are shown in FIG. 12 .

(3) After each 60 minutes of degradation, use a magnet to absorb and separate the catalyst material obtained in Example 1 from the wastewater, and use 40 ml of ultrapure water and absolute ethanol to alternately wash three times, and finally separate the material in an oven at 60 degrees Celsius. Bake for 8 hours. After drying, it will be used for the next degradation.

(4) It can be seen from Figure 13 that after four cycles of recycling, the composite photocatalyst material prepared in Example 1 has no significant reduction in the degradation efficiency of ranitidine, indicating that the composite photocatalyst prepared by the present invention has good Photocatalytic stability and recycling performance.

The above related descriptions and descriptions of the embodiments are for the convenience of those skilled in the art to understand and apply the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these contents, and the general principles described herein can be applied to other embodiments without inventive step. Therefore, the present invention is not limited to the above-mentioned related descriptions and descriptions of the embodiments. Those skilled in the art can make improvements and modifications without departing from the scope of the present invention based on the disclosure of the present invention, which should fall within the protection scope of the present invention.

Claims (12)

1. A sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst is characterized in that: the preparation method takes sulfur-doped graphite-like phase carbon nitride nanosheets as carriers, and the sulfur-doped graphite-like phase carbon nitride nanosheets are modified with graphene and ferroferric oxide particles.

2. The sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst according to claim 1, characterized in that: the graphene is attached to the surface of the sulfur-doped graphite-phase carbon nitride nanosheet through an impregnation method, and the ferroferric oxide is attached to the interlayer or surface of the sulfur-doped graphite-phase carbon nitride nanosheet through an alkaline-thermal coprecipitation method.

3. The sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst according to claim 1, characterized in that: the mass ratio of the graphene to the sulfur-doped carbon nitride nanosheet is 1 (500-1000).

4. The sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst according to claim 1, characterized in that: the mass ratio of the ferroferric oxide particles to the sulfur-doped carbon nitride nanosheets is 1 (5-20).

5. A preparation method of the sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst as defined in any one of claims 1 to 4, comprising the following steps:

and S1, heating thiourea serving as a precursor for a certain time in a special device and a high-temperature environment, and screening, grinding and sieving to obtain the sulfur-doped carbon nitride nanosheet.

And S2, mixing the graphene oxide solution with the sulfur-doped carbon nitride nanosheets obtained in the step S1, and performing ultrasonic dispersion to obtain the sulfur-doped carbon nitride nanosheet loaded graphene composite photocatalyst.

And S3, dispersing and mixing ferrous chloride and ferric chloride solution with the sulfur-doped carbon nitride nanosheet-loaded graphene composite photocatalyst obtained in the step S2, heating in a water bath, and adding ammonia water to realize alkali-heat coprecipitation to obtain the sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst.

6. The method for preparing the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst according to claim 5, wherein in the step S1, the preparation of the sulfur-doped graphite-phase carbon nitride nanosheet comprises the following steps:

(1) preparing a precursor: weighing thiourea precursor in a ceramic crucible, wherein the thiourea does not need to be subjected to any pretreatment; putting the mixture into a muffle furnace for heating and calcining.

(2) A temperature rising step is set: and (3) from a room temperature state, carrying out temperature rise program setting at a temperature rise rate of 2-3 ℃ per minute, raising the temperature to 540-550 ℃, and carrying out heat preservation for 3-4 hours for calcination, wherein no inert shielding gas is needed in the calcination process.

(3) And after the calcination and heat preservation are finished, naturally cooling to room temperature. The obtained target material trace sulfur-doped graphite-like phase carbon nitride powder.

7. The preparation method of the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst according to claim 5, wherein in the step S2, the graphene oxide and sulfur-doped carbon nitride nanosheets are prepared by the following steps:

(1) adding the graphene dispersoid into a mixed solution of ethanol and water, and stirring for 0.5 to 1 hour to prepare a graphene suspension;

(2) adding sulfur-doped graphite-phase carbon nitride nanosheets into the dispersion suspension obtained in the step (1), stirring the mixture solution for 0.5 to 1 hour, and then ultrasonically dispersing for 0.5 to 1 hour to obtain a sulfur-doped carbon nitride nanosheet loaded graphene composite photocatalyst suspension;

(3) and centrifugally collecting, washing and drying to obtain the sample sulfur-doped carbon nitride nanosheet loaded graphene composite photocatalyst.

8. The preparation method of the sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene composite photocatalyst, according to claim 7, wherein the mass ratio of the graphene to the sulfur-doped carbon nitride nanosheet is 1 (500-1000); the volume ratio of the ethanol to the water in the ethanol and water mixed solution is 1 (1-2).

9. The method for preparing the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst according to claim 5, wherein in the step of S3, the preparation method of the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst comprises the following steps:

(1) dissolving ferric chloride and ferric dichloride tetrahydrate in distilled water, and adding the solution into the suspension in the step (2) in the claim 5;

(2) heating and stirring the mixed solution for 30 to 40 minutes, then quickly adding ammonia water into the mixed solution, continuously stirring for 30 to 40 minutes, and then naturally cooling the solution;

(3) and (3) collecting the prepared precipitate through centrifugation, washing the precipitate for 2-3 times by using ethanol and water alternately, and drying the precipitate in an oven for 7-10 hours.

10. The preparation method of the sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene and ferroferric oxide composite magnetic photocatalyst according to claim 9, wherein the mass ratio of the ferroferric oxide to the sulfur-doped carbon nitride nanosheets is 1: (5-20);

and/or, in the step (2): the ammonia water is generally 5-10 ml;

and/or, in the step (2): the heating temperature is 80-85 ℃;

and/or, in the step (3): the temperature in the drying oven is set to be 60-70 ℃.

11. The application of the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst as defined in any one of claims 1 to 5 in antibiotic wastewater treatment, is characterized in that: mixing the sulfur-doped graphite-phase carbon nitride nanosheet-loaded graphene, a ferroferric oxide composite magnetic photocatalyst and antibiotic wastewater to perform photocatalytic reaction, and finishing the treatment of the antibiotic wastewater.

12. The application of claim 11, wherein the addition amount of the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst is 0.2-1.5 g of the sulfur-doped graphite-phase carbon nitride nanosheet-supported graphene and ferroferric oxide composite magnetic photocatalyst added to each liter of antibiotic wastewater;

and/or the antibiotics in the antibiotic wastewater are ranitidine and oxytetracycline; the concentration of ranitidine or oxytetracycline in the antibiotic wastewater is 5-15 mg/L;

and/or the light source of the visible light is a xenon lamp light source;

and/or the photocatalytic reaction time is 0.8-1 hour.

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