CN107159280A - A kind of catalyst for converting aqueous solution nitrite and its preparation method and application - Google Patents

Abstract

The invention relates to a catalyst for converting nitrite in aqueous solution, its preparation method and application. The technical scheme adopted is: the up-conversion luminescent material Er ³⁺ :YAlO ₃ was prepared by the sol-gel method, and then Er ³⁺ :YAlO ₃ @BiPO ₄ and CdS were synthesized respectively by the hydrothermal method. Finally, a novel solar photocatalytic system Er ³⁺ : YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS was synthesized by boiling liquid method and high temperature calcination. Nitrite and other pollutants were treated with modified Z-type Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS photocatalyst under sunlight irradiation. The method of the invention is simple and novel, has low cost, does not generate by-products and does not cause environmental pollution.

Description

Catalyst for converting nitrite in aqueous solution and its preparation method and application

technical field

The invention belongs to the field of chemical catalysis, and in particular relates to the synthesis of a novel catalyst and a method for using the catalyst to convert nitrite in water.

Background technique

In nature, nitrite is usually a product produced by the oxidation of ammonia by nitrosifying bacteria, and it is also a relatively stable intermediate product in the process of nitrate degradation. With the rapid development of modern industry and agriculture, the concentration of nitrite in water bodies has increased significantly due to excessive discharge of industrial sewage, excessive use of nitrogen fertilizers, and incomplete abiotic denitrification processes. Nitrite is an inorganic environmental pollutant that is very toxic to human health. Once excessive intake, nitrite will combine with hemoglobin in the blood to form methemoglobin, which will cause human poisoning. In addition, excessive intake of nitrite will be converted into carcinogen nitrosamines in the body, leading to diseases such as high blood pressure, gastric cancer, intestinal cancer, leukemia and brain tumors. Therefore, the World Health Organization proposes that the maximum concentration of nitrite in drinking water is 3mg/L. Removal of nitrite from drinking water is necessary to meet health needs.

Photocatalytic technology has attracted extensive attention because it can directly use the absorbed light to remove pollutants in water bodies and is easy to separate and reuse. This feature mainly appears in metal oxides and composite metal oxide semiconductors, such as _TiO2 , which is widely used because of its relatively high catalytic activity and stable physical and chemical properties. However, for the removal of sodium nitrite in water, it is necessary to select a semiconductor with strong oxidizing and reducing abilities to convert nitrite into acid radicals and ammonia, which requires the selection of a relatively high conduction band and a relatively low price. band of broadband semiconductors. Through investigation, bismuth phosphate, as a new type of non-metal oxo-acid semiconductor, has three main crystal phase structures: monoclinic phase, monoclinic phase monazite and hexagonal phase. However, as a broadband semiconductor, bismuth phosphate has a poor ability to absorb sunlight, and can only use ultraviolet light to obtain photon energy, and ultraviolet light only accounts for 5% of the solar spectrum, which makes the utilization rate of solar energy extremely small. In order to obtain higher solar energy utilization, it is necessary to develop catalysts that can utilize visible light.

Contents of the invention

The purpose of the present invention is to design and synthesize a novel catalyst Er ^{3 +} :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS that can be used to convert nitrite in aqueous solution. The compound involved in the invention belongs to a novel catalyst, and the method is simple and pollution-free when applied to the conversion of nitrite, and the catalyst is stable and easy to separate.

The technical scheme adopted in the present invention is as follows: a catalyst for converting nitrite in aqueous solution, said catalyst being Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS.

The above-mentioned preparation method of a catalyst for conversion of nitrite in aqueous solution, the method is as follows:

1) Under magnetic stirring, disperse Er ³⁺ :YAlO ₃ @BiPO ₄ powder into Na ₂ S solution, then add PdCl ₂ solution dropwise, and react for 10-15 minutes. After centrifugation, the precipitate was washed with distilled water and dried at 60°C for 10 hours. Calcining the obtained powder in a muffle furnace at 180-220°C for 3-4 hours, cooling to obtain Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) composite;

2) Add graphene oxide (GO) and N ₂ H ₄ ·H ₂ O to alcohol, ultrasonically disperse for 50-60min to obtain rGO solution, then add HAuCl ₄ ·4H ₂ O and Er ³⁺ :YAlO ₃ @( PdS/BiPO ₄ ) composite, ultrasonically dispersed for 2-3h, the reactants were washed, dried, ground, and calcined in a muffle furnace at 180-220°C for 2-3h to obtain Er ³⁺ :YAlO ₃ @(PdS/ BiPO ₄ )/(Au/rGO) powder;

3) Add graphene oxide (GO) and N ₂ H ₄ ·H ₂ O to alcohol, ultrasonically disperse for 50-60 minutes, then add HAuCl ₄ ·4H ₂ O and CdS in sequence, ultrasonically disperse for 2-3 hours, and the reactants are washed , dried, ground, and calcined in a muffle furnace at 180-220°C for 2-3h to obtain (Au/rGO)/CdS powder;

4) Add Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO) powder and (Au/rGO)/CdS powder into alcohol, ultrasonically disperse for 50-60min, filter, wash the precipitate, and dry it , ground and calcined in a muffle furnace at 2000-2500°C for 2-3h to obtain Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS powder.

The preparation method of the above-mentioned catalyst for converting nitrite in aqueous solution, according to the mass ratio, Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO):(Au/rGO)/CdS=1: 1.

The preparation method of the above-mentioned catalyst for converting nitrite in aqueous solution, the preparation method of the Er ³⁺ :YAlO ₃ @BiPO ₄ is: mixing H ₃ PO ₄ with Bi(NO ₃ ) ₃ ·6H ₂ O , stirred magnetically at room temperature for 1-2h to obtain a suspension, then added Er ³⁺ :YAlO ₃ , continued to stir for 1-2h, transferred the mixture to a hydrothermal reactor, and reacted at 100°C for 70-75h , cooled to room temperature, discarded the supernatant, washed the precipitate with deionized water until neutral, and dried to obtain Er ³⁺ :YAlO ₃ @BiPO ₄ .

The above-mentioned preparation method of a catalyst for converting nitrite in aqueous solution, the preparation method of CdS is: dissolving CdCl ₂ ·2.5H ₂ O in distilled water, adding Na ₂ S aqueous solution, and continuously stirring for 30-40min , transferred to a polytetrafluoroethylene liner, placed in an oven, kept at 100°C for 4-5 hours, cooled naturally, filtered with suction, washed with distilled water and absolute ethanol, dried and ground to obtain CdS powder.

The preparation method of the catalyst for converting nitrite in the above-mentioned a kind of aqueous solution, the preparation method of described Er ³⁺ : YAlO ₃ is: Er ₂ O ₃ and Y ₂ O ₃ are dissolved in concentrated nitric acid, then add Al (NO ₃ ) ₃ aqueous solution and citric acid aqueous solution, heat and stir at 50-60°C, stop when the solution is viscous, and obtain a foaming viscous solution, heat the foaming viscous solution at 75-85°C After 35-40h, the foam sol was obtained. After heating the foam sol at 500°C for 50-60min, it was calcined at 1100°C for 2-3h, and cooled to obtain Er ³⁺ : YAlO ₃ .

The above-mentioned catalyst is used in the conversion of nitrite in aqueous solution. The method is as follows: in the solution containing nitrite, add the catalyst described in claim 1, at normal temperature, irradiate under sunlight

The above-mentioned application of converting nitrite in aqueous solution is as follows: in the solution containing nitrite, add catalyst to improve Z-type Er ³⁺ : YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/ CdS, irradiated under sunlight at room temperature.

The beneficial effects of the present invention are: on the basis of a variety of photocatalytic technologies, the present invention has studied for nitrite to improve Z-type Er ³⁺ : YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS Nanocomposites are the main technology for nitrite conversion. Through the method of the invention, the nitrite concentration can be reduced to below 3ppm without affecting other quality indicators. Compared with other photocatalytic technologies, the process of the invention is simple, carried out at normal temperature and pressure, with mild conditions, solar energy can be utilized, and the conversion rate of nitrite can reach more than 90%.

Description of drawings

Figure 1a is the XRD pattern of Er ³⁺ : YAlO ₃ .

Figure 1b is the SEM image of Er ³⁺ : YAlO ₃ .

Figure 2a is the XRD pattern of Er ³⁺ :YAlO ₃ @BiPO ₄ .

Figure 2b is the SEM image of Er ³⁺ :YAlO ₃ @BiPO ₄ .

Fig. 3a is the XRD pattern of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ).

Fig. 3b is the SEM image of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ).

Fig. 4a is the XRD pattern of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO).

Figure 4b is the SEM image of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO).

Figure 5a is the XRD pattern of CdS.

Figure 5b is the SEM image of CdS.

Figure 6a is the XRD pattern of (Au/rGO)/CdS.

Figure 6b is the SEM image of (Au/rGO)/CdS.

Fig. 7a is the XRD pattern of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS powder.

Figure 7b is the SEM image of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS powder.

detailed description

(1) Preparation of catalyst for conversion of nitrite in aqueous solution

1. Preparation of Er ³⁺ :YAlO ₃ : Dissolve 0.0464g Er ₂ O ₃ and 2.7281g Y ₂ O ₃ in 250ml concentrated nitric acid under magnetic heating and stirring, and keep stirring until it is colorless and transparent to obtain a rare earth solution. Weigh 9.0633g Al(NO ₃ ) ₃ ·9H ₂ O and dissolve it in distilled water, stir evenly with a glass rod at room temperature, and then slowly add it into the rare earth solution. Weigh 30.4649g of citric acid as a chelating agent and a cosolvent and dissolve it in a beaker equipped with distilled water, stir well and then add it into the mixed solution. Subsequently, the above-mentioned mixed solution was continuously heated and stirred at 50-60°C, and stopped when the solution was viscous to obtain a foaming viscous solution, and then the above-mentioned foamed viscous solution was placed in a blast drying box , heated and dried at a constant temperature of 80°C for 36 hours to obtain a foam sol. The obtained foam sol was put into a muffle furnace and heated at 500°C for 50 minutes, then the temperature of the muffle furnace was raised to 1100°C and calcined for 2 hours, cooled and ground to obtain Er ³⁺ : YAlO ₃ powder.

2. Preparation of Er ³⁺ :YAlO ₃ @BiPO ₄ : Pour 100mL H ₃ PO ₄ (12M) into a beaker, mix with 10mmol Bi(NO ₃ ) ₃ 6H ₂ O, stir magnetically at room temperature for 1h to obtain a suspension liquid, and then, according to the mass ratio of Er ³⁺ :YAlO ₃ and BiPO ₄ in the ratio of 0.3:1.0, Er ³⁺ :YAlO ₃ was added to the above mixed liquid, and the stirring was continued. After stirring for 1.0 h until the solution was uniformly mixed, the mixed solution was transferred to a 50 ml hydrothermal reaction kettle, and reacted at 100° C. for 72 h. After the reaction is completed and the reaction kettle is naturally cooled, the supernatant is poured out, leaving the white powder obtained from the reaction, washed with deionized water until neutral, dried at 60°C for 12 hours, and ground to obtain Er ³⁺ : YAlO ₃ @BiPO ₄ powder, collected for later use.

3. Preparation of CdS: Weigh 6.0 mmol CdCl ₂ ·2.5H ₂ O and dissolve in 40 mL distilled water. Dissolve 6.0mmol Na ₂ S in an appropriate amount of distilled water and slowly add it dropwise to the above solution. An orange-yellow precipitate is formed. Stir continuously for 30 minutes. Then, transfer the precipitate and the solution to a 50mL polytetrafluoroethylene liner. The load does not exceed 80% of capacity. Put the polytetrafluoroethylene liner into a stainless steel reaction kettle, put the reaction kettle into an oven, raise the temperature of the oven to 100°C, and keep this temperature for 4 hours. After the reaction is completed, let it cool down naturally, then take out the reaction kettle, a bright yellow precipitate appears, transfer the yellow precipitate to a Buchner funnel, filter it with suction, wash it several times with distilled water and absolute ethanol, put the product in an oven, and heat up to 80°C , keep this temperature for 3 hours, grind to get CdS powder.

4. Preparation of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) composite: Disperse 1.00g Er ³⁺ :YAlO ₃ @BiPO ₄ powder into 90ml PdCl ₂ solution (11mmol/L) under magnetic stirring condition , then, add 2ml Na ₂ S solution (0.50mol/L) dropwise, react for 10-15min, centrifuge, wash the precipitate with distilled water, dry at 60°C for 10 hours, and calcinate the product in a muffle furnace at 200°C for 3 hours, Cool to get Er3+:YAlO ₃ @(PdS/BiPO ₄ ) complex.

5. Preparation of Er ³⁺ : YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO): add 4.0mL GO (3.00mg/mL) and 0.461mL N ₂ H ₄ ·H ₂ O (85%) to 16mL ethanol , ultrasonically dispersed for 60min (frequency: 80kHz, output power: 50W), and rGO solution was obtained. Next, HAuCl ₄ ·4H ₂ O (97%) and 1.00 g of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) powder were added to the above rGO solution, and dispersed by ultrasonic for 2 hours. Finally, the obtained mixture was washed several times with alcohol, and then dried at 60°C for 12 hours. After grinding, it was calcined in a muffle furnace at 200°C for 2 hours to obtain Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/( Au/rGO) powder.

6. Preparation of (Au/rGO)/CdS: Add 4.0mL GO (3.00mg/mL) and 0.461mL N ₂ H ₄ ·H ₂ O (85%) to 16mL alcohol, ultrasonically disperse for 60 minutes (frequency: 80kHz, Output power: 50W), obtain rGO solution. Next, HAuCl ₄ ·4H ₂ O (97%) and 1.00 g of CdS powder were added into the above rGO solution, and dispersed sufficiently by ultrasonic for 2 hours. Finally, the resulting mixture was cleaned several times with alcohol, then dried at 60°C for 12 hours, ground, and calcined in a muffle furnace at 200°C for 2 hours to obtain (Au/rGO)/CdS.

7. Add 1.0g Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) and 1.0g (Au/rGO)/CdS into alcohol, and ultrasonically disperse for 50-60min. Filter, wash the obtained precipitate with deionized water and alcohol for 3 times respectively, then dry at 60°C for 12h, after grinding, put it in a muffle furnace at 2000°C for calcination for 2h, after the reaction, grind and collect to obtain Er ^{3 +} :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS powder.

(2) Characterization data

The XRD of the prepared Er ³⁺ : YAlO ₃ is shown in Figure 1a. It can be seen from Figure 1a that the diffraction peak position of the sample is basically consistent with the data of JCPDS standard card 33-0040, which shows that the samples after heat treatment are all single Body-centered cubic structure, no other impurity phases appear. This shows that the doping of Er ³⁺ ions has no obvious effect on the crystal structure.

The SEM of the prepared Er ³⁺ : YAlO ₃ is shown in Fig. 1b. It can be seen from Fig. 1b that the obtained crystals are irregular in shape and the average particle size is 80nm. The size distribution is relatively uniform and the dispersion is also good. Indicates that the sample preparation was successful.

The XRD of the prepared Er ³⁺ :YAlO ₃ @BiPO ₄ is shown in Figure 2a. It can be seen from Figure 2a that the characteristic peaks of BiPO ₄ are 2θ=18.13°(–101), 2θ=22.32°(–111), 2θ=26.03 °(110), 2θ=29.58°(200), 2θ=34.82°(–202), 2θ=46.98°(301), 2θ=49.24(212) and 2θ=53.25°(203) which are compatible with BiPO ₄ standard card (JCPDS card No.80-0209) data are basically consistent, which shows that the treated sample has a monoclinic crystal structure, and no other impurity phases appear.

The SEM of the prepared Er ³⁺ :YAlO ₃ @BiPO ₄ is shown in Figure 2b. It can be seen from Figure 2b that Er ³⁺ :YAlO ₃ and BiPO ₄ have formed a good coating structure. The prepared _BiPO crystals are about 300 nm long.

The XRD and SEM of the prepared Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) are shown in Figures 3a and 3b. It can be seen from Figure 3a that Er ^{3 +} :YAlO ₃ @(PdS/BiPO ₄ ) has the characteristic peaks of Er ³⁺ :YAlO ₃ and BiPO ₄ at the same time, and no other impurity phases appear, which shows that Er ^{3 +} :YAlO ₃ Combination with BiPO ₄ has no obvious effect on the crystal structure. It can be seen from Figure 3b that some particles of about 30nm are loaded on the surface of BiPO ₄ , and these particles are PdS. It shows that the composite catalyst was prepared successfully.

The XRD and SEM of the prepared Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO) are shown in Figures 4a and 4b. It can be seen from Figure 4a that Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO) has Er ³⁺ :YAlO ₃ and BiPO ₄ characteristic peaks at the same time, and no obvious representative peaks of PdS, Au and The characteristic peaks of rGO, which may be because their usage is small enough to be below the detection limit of the XRD patterns. It can be seen from Figure 4b that the surface of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ) is covered by rGO, and some small granular substances are distributed on it, which belong to Au particles. This indicates that Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO) has been well formed.

The XRD and SEM of the prepared CdS are shown in Figures 5a and 5b. It can be seen from Figure 5a that the characteristic peaks of CdS are 2θ=24.91°(100), 2θ=26.52°(002), 2θ=28.34°(101), 2θ=37.01°(102), 2θ=43.85°(110), 2θ = 48.17° (103) and 2θ = 52.3° (112) are basically consistent with the data of the CdS standard card (JCPDS No. 41-1049), which indicates that there are no other impurity phases in the treated sample. It can be seen from Figure 5b that there are many uniform spherical crystal particles with a diameter between 40-60nm, which belongs to the traditional crystallization form of nanoscale CdS particles.

The XRD and SEM of the prepared (Au/rGO)/CdS are shown in Figures 6a and 6b. It can be seen from Figure 6a that no obvious characteristic peaks representing Au and rGO can be found on the way, which may be because their usage is so small that it is below the detection limit of the XRD pattern. Their presence will be identified using other detection methods. It can be seen from Fig. 6b that both CdS and Au particles are dispersed on rGO. This indicates that (Au/rGO)/CdS has been successfully prepared.

The XRD and SEM of the prepared Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS are shown in Figures 7a and 7b. It can be seen from Fig. 7a that the characteristic peaks of the up-conversion luminescent material Er ³⁺ : YAlO ₃ and BiPO ₄ are characteristic peaks. It can be seen from Figure 7b that the overall morphology of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS is composed of different particles. It can be clearly seen from the figure that CdS and Au The particles are distributed on the surface of Er ³⁺ :YAlO ₃ @(PdS/BiPO ₄ ). Because rGO is a transparent material, it is difficult to be identified.

(3) Nitrite conversion method

Add 50mL of sodium nitrite (NaNO ₂ ) solution (10.0ppm) and 50mg of Er ^{3 +} :YAlO ₃ @(PdS/BiPO ₄ )/(Au/rGO)/CdS to the test tube of the photocatalytic reaction apparatus, simulate at room temperature Under sunlight, turn on the magnetic stirring, and react for 120 minutes. After the reaction is completed, the catalyst and the solution are separated.

The concentration of nitrite in the aqueous solution is determined by liquid chromatography, and the conversion rate is above 90%.

Claims (8)

1. a kind of catalyst for converting aqueous solution nitrite, it is characterised in that described catalyst is Er³⁺:YAlO₃@ (PdS/BiPO₄)/(Au/rGO)/CdS。

2. a kind of preparation method of the catalyst of conversion aqueous solution nitrite described in claim 1, it is characterised in that side Method is as follows：

1) under magnetic agitation, by Er³⁺:YAlO₃@BiPO₄Powder is distributed to Na₂In S solution, PdCl is then added dropwise₂Solution, React 10-15min；By centrifugation, precipitation is cleaned with distilled water, 60 degrees Celsius dry 10 hours；By obtained powder in Muffle Calcined 3-4 hours at 180-220 DEG C in stove, cooling obtains Er³⁺:YAlO₃@(PdS/BiPO₄) compound；

2) graphene oxide and N are added in alcohol₂H₄·H₂O, ultrasonic disperse 50-60min, then sequentially adds HAuCl₄· 4H₂O and Er³⁺:YAlO₃@(PdS/BiPO₄) compound, ultrasonic disperse 2-3h, reactant is scrubbed, after drying, grinding, in Muffle 2-3h is calcined at 180-220 DEG C in stove, Er is obtained³⁺:YAlO₃@(PdS/BiPO₄)/(Au/rGO) powder；

3) graphene oxide and N are added in alcohol₂H₄·H₂O, ultrasonic disperse 50-60min, then sequentially adds HAuCl₄· 4H₂O and CdS, ultrasonic disperse 2-3h, reactant is scrubbed, after drying, and grinding calcines 2- in Muffle furnace at 180-220 DEG C 3h, obtains (Au/rGO)/CdS powder；

4) by Er³⁺:YAlO₃@(PdS/BiPO₄)/(Au/rGO) powder is with (Au/rGO)/CdS powder addition alcohol, and ultrasound is divided 50-60min is dissipated, filtering precipitates scrubbed, after drying, and grinding is placed in 2000-2500 DEG C of Muffle furnace and calcines 2-3h, obtains Er³⁺: YAlO₃@(PdS/BiPO₄)/(Au/rGO)/CdS powder.

3. a kind of preparation method of catalyst for converting aqueous solution nitrite according to claim 2, its feature exists In, in mass ratio, Er³⁺:YAlO₃@(PdS/BiPO₄)/(Au/rGO):(Au/rGO)/CdS=1:1.

4. a kind of preparation method of catalyst for converting aqueous solution nitrite according to claim 2, its feature exists In described Er³⁺:YAlO₃@BiPO₄Preparation method be：By H₃PO₄With Bi (NO₃)₃·6H₂O is mixed, and magnetic force is stirred at room temperature 1-2h is mixed, suspension is obtained, then, Er is added³⁺:YAlO₃, 1-2h is persistently stirred, mixed liquor is transferred in hydrothermal reaction kettle, 70-75h is reacted under the conditions of 100 DEG C, room temperature is cooled to, supernatant is abandoned, sediment is washed with deionized to neutrality, dries, obtain Er³⁺:YAlO₃@BiPO₄。

5. a kind of preparation method of catalyst for converting aqueous solution nitrite according to claim 2, its feature exists In described CdS preparation method is：By CdCl₂·2.5H₂O is dissolved in distilled water, adds Na₂The S aqueous solution, lasting stirring After 30-40min, it is transferred in polytetrafluoroethylene bushing, is put into baking oven, at 100 DEG C, is incubated 4-5h, natural cooling is taken out Filter, is washed with distilled water and absolute ethyl alcohol, and product is dried, and grinding obtains CdS powder.

6. a kind of preparation method of catalyst for converting aqueous solution nitrite according to claim 2, its feature exists In described Er³⁺:YAlO₃Preparation method be：By Er₂O₃And Y₂O₃It is dissolved in concentrated nitric acid, then sequentially adds Al (NO₃)₃ The aqueous solution and aqueous citric acid solution, in 50-60 DEG C of heating stirring, stop when solution is in thick, and must foam glutinous colloidal solution, By the glutinous colloidal solution of foaming in heating 35-40h at 75-85 DEG C, foam sol is obtained, foam sol is heated into 50- at 500 DEG C After 60min, 2-3h is calcined at 1100 DEG C, cooling obtains Er³⁺:YAlO₃。

7. application of the catalyst in conversion aqueous solution nitrite described in claim 1.

8. application according to claim 8, it is characterised in that method is as follows：In the solution containing nitrite, add Catalyst described in claim 1, irradiates under normal temperature, solar irradiation.