A C3N5 / Mn 0.3 Cd 0.7 S photocatalyst, and a preparation method and application thereof

Abstract

The application belongs to the technical field of heavy metal ion treatment, and particularly relates to a C3N5 / Mn 0.3 Cd 0.7 S photocatalyst, a preparation method and application thereof, comprising the following steps: (1) acid treatment of C3N5 to obtain acid modified C3N5; (2) mixing the acid modified C3N5 in step (1) with a precursor solution of Mn 0.3 Cd 0.7 S, ultrasonic and stirring treatment to obtain a mixed suspension; (3) hydrothermal treatment of the mixed suspension in step (2), cooling to room temperature, washing, filtering to obtain filter residue, and drying to obtain the C3N5 / Mn 0.3 Cd 0.7 S photocatalyst. The application provides a method for safely, energy-efficiently and highly effectively removing Cr(VI) under visible light, which is simple in method, convenient in operation, low in cost, high in photocatalytic reduction efficiency, free of secondary pollution and without the need of adding other chemical substances to the photocatalytic system.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heavy metal ion treatment, and particularly relates to a C3N5 / Mn 0.3 Cd 0.7 S photocatalyst, a preparation method and application thereof. BACKGROUND

[0002] With the super-speed development of global economy and the rise of chemical industry, heavy metal pollutants represented by Cr(VI) inevitably enter water resources while meeting the production of science and technology, which not only destroys the local water body ecology, but also causes animal kidney function disorder, reproductive system damage, teratogenicity and carcinogenicity, etc. At present, the methods for removing Cr(VI) in water body mainly include adsorption, electrolysis and chemical reduction. Although adsorption can quickly remove Cr(VI), subsequent treatment is easy to cause secondary pollution; electrolysis converts Cr(VI) into Cr(III) under external voltage, but this method needs to maintain high voltage and stable electrolyte, and the processing cost is high; chemical reduction needs to add reducing agent to reduce Cr(VI), and the cost is greatly increased. In recent years, exploring and researching new and environmentally friendly degradation technology has become the main task of many scientific researchers, among which the photocatalytic semiconductor technology is favored by many scholars due to its simplicity, environmental protection and sustainability. The key to the photocatalytic reduction of Cr(VI) by semiconductor is to find a photocatalyst with appropriate band gap, stability and high efficiency.

[0003] Chinese patent 201710452931.9 discloses a method for photocatalytic reduction of Cr(VI), in which Fe 3+ / TiO2 reduces Cr(VI) photocatalytic reaction under ultraviolet light source, under the best conditions, the ultraviolet light is kept for 60 min, the Fe 3+ / TiO2 reduction efficiency of Cr(VI) is 99.8%, and the reaction rate constant is 0.0584min -1 Under visible light, the efficiency is as low as 4-5%, which seriously limits the application of TiO2 in practice. Chinese patent 201810506209.3 discloses a method for photocatalytic reduction of Cr(VI), in which N-Fe 3+ / TiO2 reduces Cr(VI) photocatalytic reaction under visible light source, under the best conditions, the visible light is kept for 50 min, the catalyst dosage is 3g / L, N-Fe 3+ / TiO2 reduction efficiency of Cr(VI) is 99.2%, and the reaction rate constant is 0.0753min -1 . SUMMARY

[0004] Therefore, the application provides a Mn 0.3 Cd 0.7The C3N5 / Mn

[0005] To achieve the above object, the present application adopts the following technical scheme:

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

[0007] (1) acid treatment of C3N5 to obtain acid-modified C3N5;

[0008] (2) mixing the acid-modified C3N5 in step (1) with a precursor solution of Mn 0.3 Cd 0.7 S, ultrasonic and stirring treatment to obtain a mixed suspension;

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

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

[0011] The above technical scheme has the following beneficial effects: the single material of MCS and CN has weak degradation efficiency on Cr(VI), and the combination of the two greatly improves the effect and produces a synergistic effect, and the molar ratio of the acid-modified C3N5 to Mn 0.3 Cd 0.7 S has a key influence on the degradation efficiency, and the degradation efficiency of Cr(VI) is reduced when the ratio exceeds or is lower than the ratio defined in the present application.

[0012] Preferably, in step (1), acid is added to C3N5 and stirred for 20-28 hours, and then 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 the C3N5 to the acid is 1g:(1-4)mL.

[0013] Preferably, in step (2), the precursor solution of Mn 0.3 Cd 0.7 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 of step (3) is 160-180℃, and the time is 6-24h.

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

[0016] Preferably, the drying in step (3) is performed at 60-80℃ for 12-24h.

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

[0018] In the removal of heavy metal ion Cr(VI) in a solution, the reduction degradation of Cr(VI) is realized through visible light irradiation.

[0019] Compared with the prior art, the application has the following excellent effects:

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

[0021] Compared with the prior art, the application provides a method for safely, energy-efficiently and highly effectively removing Cr(VI) under visible light, which is simple in method, convenient in operation, low in cost, high in photocatalytic reduction efficiency, free of secondary pollution and free of addition of other chemical substances to the photocatalytic system. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of the provided drawings.

[0023] Figure 1 The scanning electron microscope image of the photocatalyst prepared in Example 2 and Comparative Example 1-2 of the application;

[0024] Figure 2 The photocatalytic reaction effect diagram of the photocatalyst prepared in Example 1-3 and Comparative Example 1-2 of the application in reduction of Cr(VI) under visible light. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

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

[0027] 5.0 g of 3-amino-1,2,4-triazole was dissolved in 100 ml of distilled water, and the solution was stirred to dryness at 80 °C. After grinding, the resulting solid product was transferred to a muffle furnace and calcined at 540 °C for 3 hours in air atmosphere, with a heating rate of 5 °C / min. -1 After cooling to ambient temperature, the sample was obtained. 4.0 g of the sample was weighed, ground into powder, and 40 mL of a mixed acid solution of 37% hydrochloric acid and 98% sulfuric acid (volume ratio 1:1) was added. The mixture was stirred for 24 h. The sample was washed with purified water until neutral to obtain acid-modified C3N5.

[0028] The performance tests in the following examples and comparative examples were conducted in a photochemical system using a 300W xenon lamp (λ≧400nm) as the light source. The tests included: 20mg of the prepared catalyst was placed in a quartz photocatalytic tube with a diameter of 2cm and a height of 20cm; 40mL of 10mg / L potassium dichromate solution was added; the mixture was stirred in the dark for 30min; the light source was then turned on; the reaction temperature was controlled at 20℃; 5mL of sample solution was accurately pipetted every 10min; after centrifugation, a chromium colorimetric agent was added to the supernatant; and the absorbance was measured using a UV-Vis spectrophotometer to calculate the reduction rate.

[0029] Example 1

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

[0031] 10.6 mg (0.1 mmol) of acid-modified C3N5 was weighed and sonicated in 65 mL of distilled water for 30 min. 0.6 mmol of manganese acetate tetrahydrate, 1.4 mmol of cadmium nitrate tetrahydrate, and 2 mmol of thiourea were added, and the mixture was stirred continuously for 30 min. The mixture was transferred to a 100 mL PTFE-lined autoclave and heated to 180 °C for 12 h. After the sample cooled to room temperature, it was washed three times alternately with ethanol and deionized water, dried at 80 °C for 12 h, and then collected. The C3N5 / Mn prepared in Example 1 was then used... 0.3 Cd 0.7The S photocatalyst is labeled MCS / CN1.

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

[0033] Example 2

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

[0035] Weigh 63.6 mg (0.6 mmol) of acid-modified C3N5 and sonicate 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 maintain the mixture with continuous stirring for 30 min. Transfer the mixture to a 100 mL PTFE-lined autoclave and heat it to 180 °C for 12 h. After the sample cools to room temperature, wash it three times alternately with ethanol and deionized water, dry it at 80 °C for 12 h, and collect it. The C3N5 / Mn prepared in Example 1... 0.3 Cd 0.7 The S photocatalyst is labeled MCS / CN2.

[0036] Under the conditions of irradiation by a 300W xenon lamp and a 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 using the S photocatalyst (MCS / CN2) was 0.11830 min. -1 like Figure 2 As shown.

[0037] Example 3

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

[0039] 106 mg (1.0 mmol) of acid-modified C3N5 was weighed and sonicated in 65 mL of distilled water for 30 min. 0.6 mmol of manganese acetate tetrahydrate, 1.4 mmol of cadmium nitrate tetrahydrate, and 2 mmol of thiourea were added, and the mixture was stirred continuously for 30 min. The mixture was transferred to a 100 mL PTFE-lined autoclave and heated to 180 °C for 12 h. After the sample cooled to room temperature, it was washed three times alternately with ethanol and deionized water, dried at 80 °C for 12 h, and then collected. The C3N5 / Mn prepared in Example 1 was then used... 0.3 Cd 0.7 The S photocatalyst is labeled MCS / CN3.

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

[0041] Comparative Example 1

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

[0043] Comparative Example 2

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

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

[0046] Figure 1 Scanning electron microscope (SEM) images of the photocatalysts prepared in Example 2 and Comparative Examples 1-2.Figure 1 It can be seen that the catalyst prepared in Comparative Example 1 is irregularly granular, the catalyst prepared in Comparative Example 2 has a needle-like flower structure, and the catalyst prepared in Example 2 is flower-like clusters. The scanning electron microscope images show that the catalyst in Example 2 successfully catalyzed acid-modified C3N5 and Mn. 0.3 Cd 0.7 S was compounded.

[0047] Figure 2 The images show the photocatalytic effect of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2 on the reduction of 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 exhibits the best photocatalytic effect in reducing Cr(VI) under visible light.

[0048] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The solutions disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant parts can be found in the method section.

[0049] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded 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 by, Includes the following steps: (1) C3N5 is acid-treated to obtain acid-modified C3N5; (2) The acid-modified C3N5 and Mn described in step (1) are combined. 0.3 Cd 0.7 The precursor solutions of S are mixed and subjected to ultrasonic and stirring treatment to obtain a mixed suspension. (3) The mixed suspension obtained in step (2) is subjected to hydrothermal treatment, cooled to room temperature, washed, filtered, and the residue is dried to obtain the C3N5 / Mn. 0.3 Cd 0.7 S photocatalyst; The acid-modified C3N5 and Mn 0.3 Cd 0.7 The molar ratio of S is 0.6:

2.

2. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized by, Step (1) Add acid to C3N5, stir for 20-28h, wash with pure water until neutral, and 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.

3. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized by, 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.

4. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized by, Step (3) The hydrothermal treatment temperature is 160-180℃ and the time is 6-24h.

5. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The method for preparing S photocatalyst is characterized by, The washing process described in step (3) involves alternating washing with ethanol and deionized water multiple times.

6. A C3N5 / Mn according to claim 1 0.3 Cd 0.7 The preparation method of S photocatalyst is characterized by, The drying process described in step (3) involves drying at 60–80°C for 12–24 hours.

7. The C3N5 / Mn prepared by the preparation method according to any one of claims 1-6 0.3 Cd 0.7 S photocatalyst.

8. A C3N5 / Mn according to claim 7 0.3 Cd 0.7 Application of S photocatalyst in the removal of heavy metal ions Cr(VI) from solution.

9. The application according to claim 8, characterized in that, When removing heavy metal ions Cr(VI) from the solution, the reduction and degradation of Cr(VI) are achieved by irradiation with visible light.

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