C3N5 / Mn0. 3Cd0. 7S photocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of heavy metal ion treatment, and particularly relates to a C3N5 / Mn0. 3Cd0. 7S photocatalyst and a preparation method and application thereof, and the preparation method comprises the following steps: (1) carrying out acid treatment on C3N5 to obtain acid modified C3N5; (2) mixing the acid modified C3N5 obtained in the step (1) with a precursor solution of Mn0. 3Cd0. 7S, and carrying out ultrasonic and stirring treatment to obtain a mixed suspension; and (3) carrying out hydrothermal treatment on the mixed suspension obtained in the step (2), cooling to room temperature, washing, filtering to obtain filter residues, and drying to obtain the C3N5 / Mn0. 3Cd0. 7S photocatalyst. The invention provides a safe, energy-saving and efficient method for removing Cr (VI) under visible light, the method is simple, the operation is convenient, the cost is low, the photocatalytic reduction efficiency is high, other chemical substances do not need to be added into a photocatalytic system, and secondary pollution is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal ion treatment, and specifically relates to a C3N5 / Mn 0.3 Cd 0.7 S photocatalyst and its preparation method and application. Background Art

[0002] With the rapid development of the global economy and the rise of the chemical industry, while meeting the needs of scientific and technological production, heavy metal pollutants represented by Cr(VI) inevitably enter water resources, which not only destroys the local water ecology, but also causes animal kidney dysfunction, reproductive system damage, teratogenicity and carcinogenicity. At present, the main methods for removing Cr(VI) from water bodies are adsorption, electrolysis and chemical reduction. Although adsorption can quickly remove Cr(VI), subsequent treatment is prone to secondary pollution; electrolysis converts Cr(VI) into Cr(III) under an external voltage, but this method requires maintaining high voltage and stable electrolyte, and the processing cost is high; chemical reduction requires the addition of a reducing agent to reduce Cr(VI), which greatly increases the cost. In recent years, exploring and researching new and environmentally friendly degradation technologies has become the main task of many scientific researchers. Among them, photocatalytic semiconductor technology has attracted the favor of many scholars due to its simplicity, environmental protection and sustainability. The key to semiconductor photocatalytic reduction of Cr(VI) is to find a photocatalyst with a suitable band gap, stability and high efficiency.

[0003] Chinese patent 201710452931.9 discloses a method for photocatalytic reduction of Cr(VI), wherein an ultraviolet light source is used to carry out Fe 3+ / TiO2 photocatalytic reduction of Cr(VI), under optimal conditions, maintained under UV light for 60 min, Fe 3+ / TiO2 reduction efficiency of Cr(VI) is 99.8%, and the reaction rate constant is 0.0584min -1 , the efficiency under visible light is as low as 4-5%, which seriously limits the practical application of TiO2. Chinese patent 201810506209.3 discloses a method for photocatalytic reduction of Cr(VI), which uses visible light to carry out N-Fe 3+ / TiO2 photocatalytic reduction of Cr(VI) under the best conditions, maintained for 50 min under visible light, catalyst dosage 3 g / L, N-Fe 3+ / TiO2 reduction efficiency of Cr(VI) is 99.2%, and the reaction rate constant is 0.0753min -1 . Summary of the invention

[0004] In view of this, the present invention provides a Mn 0.3 Cd 0.7S composite acid modified C3N5 photocatalyst is a safer, greener and more energy-saving photocatalytic material. Under visible light irradiation, it produces strongly reducing photogenerated electrons on its surface, which can effectively reduce Cr(VI) to Cr(III).

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A C3N5 / Mn 0.3 Cd 0.7 The preparation method of S photocatalyst comprises the following steps:

[0007] (1) treating C3N5 with acid to obtain acid-modified C3N5;

[0008] (2) The acid-modified C3N5 and Mn 0.3 Cd 0.7 The precursor solutions of S are mixed, and ultrasonic and stirring treatments are performed to obtain a mixed suspension;

[0009] (3) subjecting the mixed suspension of step (2) to hydrothermal treatment, cooling to room temperature, washing, filtering to obtain the residue, and drying to obtain the C3N5 / Mn 0.3 Cd 0.7 S photocatalyst.

[0010] Preferably, the acid-modified C3N5 and Mn 0.3 Cd 0.7 Molar ratio of S (0.1~1.0): 2 mol.

[0011] The beneficial effects of the above technical solution are as follows: the degradation efficiency of Cr(VI) by MCS and CN is relatively weak, but after the two are combined, the effect is greatly improved, resulting in a synergistic effect, and the acid-modified C3N5 and Mn 0.3 Cd 0.7 The molar ratio of S has a key influence on the degradation efficiency. A ratio exceeding or below the ratio defined in the present invention will reduce the Cr(VI) degradation efficiency.

[0012] Preferably, in step (1), an acid is added to C3N5, stirred for 20-28 hours, and washed with pure water until neutral to obtain acid-modified C3N5; the acid is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the mass volume ratio of C3N5 to acid is 1g: (1-4)mL.

[0013] Preferably, in step (2), Mn 0.3 Cd 0.7 The precursor solution of S is a mixture of manganese acetate tetrahydrate, cadmium nitrate tetrahydrate and thiourea in a molar ratio of 0.3:0.7:1.

[0014] Preferably, the hydrothermal treatment temperature in step (3) is 160-180° C. and the time is 6-24 h.

[0015] Preferably, the washing in step (3) is performed by alternating ethanol and deionized water for multiple times.

[0016] Preferably, the drying in step (3) is carried out at 60-80° C. for 12-24 hours.

[0017] The C3N5 / Mn 0.3 Cd 0.7 Application of S photocatalyst in the removal of heavy metal ions Cr(VI) from solution.

[0018] When removing heavy metal ions Cr(VI) from the solution, the reduction degradation of Cr(VI) is achieved by visible light irradiation.

[0019] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following excellent effects:

[0020] The C3N5 / Mn disclosed in the present invention 0.3 Cd 0.7 S photocatalyst was prepared by hydrothermal in situ growth method; C3N5 / Mn 0.3 Cd 0.7 The photocatalytic reduction reaction of Cr(VI) by S photocatalyst under visible light follows the first-order reaction kinetic equation, and the reaction rate constant is 0.1183min -1 .

[0021] Compared with the prior art, the present invention provides a safe, energy-saving and efficient method for removing Cr(VI) under visible light. The method is simple, easy to operate, low in cost, high in photocatalytic reduction efficiency, does not require the addition of other chemicals to the photocatalytic system, and has no secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0023] Figure 1 The scanning electron microscope images of the photocatalysts prepared in Example 2 of the present invention and Comparative Examples 1-2;

[0024] Figure 2 This is a photocatalytic reaction effect diagram of reducing Cr(VI) under visible light using the photocatalysts prepared in Examples 1-3 of the present invention and Comparative Examples 1-2. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The preparation method of acid-modified C3N5 in the specific embodiment of the present invention comprises the following steps:

[0027] Weigh 5.0 g of 3-amino-1,2,4-triazole and dissolve it in 100 ml of distilled water. After stirring and grinding at 80 °C, the obtained solid product is transferred to a muffle furnace and calcined at 540 °C for 3 hours in an air atmosphere, wherein the heating rate is 5 °C·min -1 After cooling to ambient temperature, the sample was obtained. Weigh 4.0 g of the sample and grind it into powder. Add 40 mL of a mixed acid of 37% hydrochloric acid and 98% sulfuric acid (volume ratio 1:1) and stir for 24 h. Wash with pure water until neutral to obtain acid-modified C3N5.

[0028] The performance tests of the following examples and comparative examples were conducted in a photochemical system, with a 300w xenon lamp (λ≧400nm) as the light source. The test includes: 20mg of the prepared catalyst is loaded into a quartz photocatalytic tube with a diameter of 2cm and a height of 20cm, 40mL of a 10mg / L potassium dichromate solution is added, and after stirring for 30min in a dark environment, the light source is turned on, the reaction temperature is controlled at 20°C, 5mL of the sample solution is accurately drawn every 10min, and after centrifugation, a chromium developer is added to the supernatant, and the absorbance is measured in a UV-visible spectrophotometer to calculate the reduction rate.

[0029] Example 1

[0030] A Mn 0.3 Cd 0.7 The preparation method of S composite acid modified C3N5 as a photocatalyst comprises the following steps:

[0031] Weigh 10.6 mg (0.1 mmol) of acid-modified C3N5 and ultrasonicate it in 65 mL of distilled water for 30 min, add 0.6 mmol of manganese acetate tetrahydrate, 1.4 mmol of cadmium nitrate tetrahydrate and 2 mmol of thiourea, and keep stirring for 30 min. Transfer the mixture into a 100 ml polytetrafluoroethylene-lined kettle and heat it to 180 ° C for 12 h. After the sample is cooled to room temperature, wash it alternately with ethanol and deionized water three times, dry it at 80 ° C for 12 h, and collect it. 0.3 Cd 0.7S photocatalyst is labeled as MCS / CN1.

[0032] Under the irradiation of 300W xenon lamp and the reaction temperature of 20°C, the C3N5 / Mn 0.3 Cd 0.7 The photocatalytic reaction rate of Cr(VI) reduction on S(MCS / CN1) is 0.02084min -1 like Figure 2 shown.

[0033] Example 2

[0034] A Mn 0.3 Cd 0.7 The preparation method of S composite acid modified C3N5 as a photocatalyst comprises the following steps:

[0035] Weigh 63.6 mg (0.6 mmol) of acid-modified C3N5 and ultrasonicate it in 65 mL of distilled water for 30 min. Add 0.6 mmol of manganese acetate tetrahydrate, 1.4 mmol of cadmium nitrate tetrahydrate and 2 mmol of thiourea, and keep stirring for 30 min. Transfer the mixture into a 100 ml polytetrafluoroethylene-lined kettle and heat it to 180 ° C for 12 h. After the sample is cooled to room temperature, wash it alternately with ethanol and deionized water three times, dry it at 80 ° C for 12 h, and collect it. 0.3 Cd 0.7 S photocatalyst is labeled as MCS / CN2.

[0036] Under the irradiation of 300W xenon lamp and the reaction temperature of 20°C, the C3N5 / Mn prepared in Example 2 0.3 Cd 0.7 The photocatalytic reaction rate of Cr(VI) reduction by S photocatalyst (MCS / CN2) is 0.11830min -1 like Figure 2 shown.

[0037] Example 3

[0038] A Mn 0.3 Cd 0.7 The preparation method of S composite acid modified C3N5 as a photocatalyst comprises the following steps:

[0039] Weigh 106 mg (1.0 mmol) of acid-modified C3N5 and ultrasonicate it in 65 mL of distilled water for 30 min, add 0.6 mmol of manganese acetate tetrahydrate, 1.4 mmol of cadmium nitrate tetrahydrate and 2 mmol of thiourea, and keep stirring for 30 min. Transfer the mixture into a 100 ml polytetrafluoroethylene-lined kettle and heat it to 180 ° C for 12 h. After the sample is cooled to room temperature, wash it alternately with ethanol and deionized water three times, dry it at 80 ° C for 12 h, and collect it. 0.3 Cd 0.7 S photocatalyst is labeled as MCS / CN3.

[0040] Under the irradiation of 300W xenon lamp and the reaction temperature of 20°C, the C3N5 / Mn 0.3 Cd 0.7 The photocatalytic reaction rate of Cr(VI) reduction by S photocatalyst (MCS / CN3) is 0.07965min -1 like Figure 2 shown.

[0041] Comparative Example 1

[0042] Under the irradiation of 300W xenon lamp and the reaction temperature of 20℃, the photocatalytic reaction rate of Cr(VI) reduction by acid-modified C3N5 photocatalyst was 0.00328min -1 like Figure 2 shown.

[0043] Comparative Example 2

[0044] Mn 0.3 Cd 0.7 Preparation of S photocatalyst: 0.6mmol manganese acetate tetrahydrate, 1.4mmol cadmium nitrate tetrahydrate and 2mmol thiourea were mixed and kept under continuous stirring for 30min. The mixture was transferred into a 100ml polytetrafluoroethylene-lined kettle and heated to 180℃ for 12h. After the sample was cooled to room temperature, it was washed alternately with ethanol and deionized water three times, dried at 80℃ for 12h and collected. The Mn0.3Cd0.7S photocatalyst prepared in Comparative Example 2 was labeled as MCS.

[0045] Under the irradiation of 300W xenon lamp and the reaction temperature of 20℃, Mn 0.3 Cd 0.7 The photocatalytic reaction rate of S photocatalyst reducing Cr(VI) is 0.01465min -1 like Figure 2 shown.

[0046] Figure 1 The scanning electron microscope images of the photocatalysts prepared in Example 2 and Comparative Examples 1-2 are shown. Figure 1 It can be seen that the catalyst prepared in Comparative Example 1 is in the form of irregular particles, the catalyst prepared in Comparative Example 2 is in the form of a needle-shaped flower structure, and the catalyst prepared in Example 2 is in the form of flower-shaped clusters. It can be seen from the scanning electron microscope that the catalyst in Example 2 successfully combines acid-modified C3N5 with Mn 0.3 Cd 0.7 S was compounded.

[0047] Figure 2 The photocatalytic effect diagram of the catalyst prepared in Example 1-3 and Comparative Example 1-2 in reducing Cr(VI) under visible light. Figure 2 It can be seen that the C3N5 / Mn prepared in Example 2 0.3 Cd 0.7 S photocatalyst has the best photocatalytic effect on the reduction of Cr(VI) under visible light.

[0048] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0049] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A C3N5 / Mn 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: The following steps are involved: (1) treating C3N5 with acid to obtain acid-modified C3N5; (2) The acid-modified C3N5 and Mn 0.3 Cd 0.7 The precursor solutions of S are mixed, and ultrasonic and stirring treatments are performed to obtain a mixed suspension; (3) subjecting the mixed suspension of step (2) to hydrothermal treatment, cooling to room temperature, washing, filtering to obtain the residue, and drying to obtain the C3N5 / Mn 0.3 Cd 0.7 S photocatalyst.

2. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: The acid-modified C3N5 and Mn 0.3 Cd 0.7 The molar ratio of S is (0.1~1.0):2mol.

3. A C3N5 / Mn according to claim 1 or 2 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: Step (1) adding acid to C3N5, stirring for 20-28h, washing with pure water until neutral, to obtain acid-modified C3N5; the acid is selected from any one or more of hydrochloric acid, sulfuric acid, and nitric acid, and the mass volume ratio of C3N5 to acid is 1g: (1-4)mL.

4. A C3N5 / Mn according to claim 1 or 2 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: Step (2) Mn 0.3 Cd 0.7 The precursor solution of S is a mixture of manganese acetate tetrahydrate, cadmium nitrate tetrahydrate and thiourea in a molar ratio of 0.3:0.7:

1.

5. A C3N5 / Mn according to claim 1 or 2 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: The hydrothermal treatment temperature in step (3) is 160-180° C. and the time is 6-24 hours.

6. A C3N5 / Mn according to claim 1 or 2 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized in that: The washing in step (3) is performed by alternating ethanol and deionized water for multiple times.

7. A C3N5 / Mn according to claim 1 or 2 0.3 Cd 0.7 The preparation method of the S photocatalyst is characterized in that, The drying in step (3) is carried out at 60-80° C. for 12-24 hours.

8. C3N5 / Mn prepared by the preparation method according to any one of claims 1 to 7 0.3 Cd 0.7 S photocatalyst.

9. A C3N5 / Mn according to claim 8 0.3 Cd 0.7 Application of S photocatalyst in the removal of heavy metal ions Cr(VI) from solution.

10. The use according to claim 9, characterized in that: When removing heavy metal ions Cr(VI) from the solution, the reduction degradation of Cr(VI) is achieved by visible light irradiation.

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