A high-efficiency photocatalytic purification composite material and its preparation process

Abstract

The present invention relates to a high-efficiency photocatalytic purification composite material and a preparation process thereof, belonging to the field of photodegradation technology, comprising a Zn-Cr layered double hydroxide and a gC3N4-TiO2 composite nanoparticle deposited on the Zn-Cr layered double hydroxide, wherein TiO2 is deposited on gC3N4, and the gC3N4 loaded with TiO2 is deposited on the Zn-Cr layered double hydroxide, and a conduction band that decreases successively is formed between gC3N4, TiO2 and the Zn-Cr layered double hydroxide. In the technical scheme of the present invention, the energy band potentials of the three parts of TiO2, gC3N4 and Zn-Cr layered double hydroxide show multi-step characteristics, wherein the slight gradient difference of the energy band helps to disperse the charge in multiple energy bands and provide a small interface resistance, thereby having a high charge transfer efficiency and showing excellent organic pollutant removal under sunlight irradiation.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysis, and in particular, relates to a high-efficiency photocatalytic purification composite material and a preparation process thereof. Background Art

[0002] With the strengthening of environmental protection awareness, chemical wastewater contains many harmful substances including cyanide, heavy metals, mercury, protein, etc. The traditional process of treating chemical wastewater is not only difficult, inefficient, time-consuming and labor-intensive, and the treatment cost is too high, but its treatment effect is not particularly ideal. After the sewage is purified once, there are still pollutants remaining, which may cause secondary pollution. In recent years, photocatalytic materials have received widespread attention in the treatment of chemical wastewater. Catalytic materials refer to a type of semiconductor catalyst materials required for photochemical reactions that occur under the action of light through this material. There are many photocatalytic materials in the world, including gC3N4 (graphite phase carbon nitride), titanium dioxide, zinc oxide, tin oxide, zirconium dioxide, cadmium sulfide and other oxide sulfide semiconductors.

[0003] Reasonable control of the photogenerated charge transfer inside the photocatalyst is the key to improving the photocatalytic performance. In the prior art, photogenerated charge transfer is achieved by depositing various semiconductor materials such as metal oxides on layered double hydroxides. However, the conduction band gap between the layered double hydroxides and the metal oxides is large, resulting in a large interface resistance, which is not conducive to the transfer of charges, resulting in low photocatalytic efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a high-efficiency photocatalytic purification composite material and a preparation process thereof, which solves the problem in the prior art that the conduction band gap between the layered double hydroxide and the metal oxide is large, resulting in a large interface resistance, which is not conducive to the transfer of charges and thus leads to low photocatalytic efficiency.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A high-efficiency photocatalytic purification composite material comprises a Zn-Cr layered double hydroxide and gC3N4-TiO2 composite nanoparticles deposited on the Zn-Cr layered double hydroxide, wherein TiO2 is deposited on gC3N4, and gC3N4 loaded with TiO2 is deposited on the Zn-Cr layered double hydroxide, and a conduction band that decreases in sequence is formed between TiO2, gC3N4 and the Zn-Cr layered double hydroxide;

[0007] The gC3N4-TiO2 composite nanoparticles are prepared by the following steps:

[0008] The gC3N4 powder and the TiO2 powder were mixed and dissolved in methanol under ultrasound, and the temperature was raised to 80°C to remove the methanol to obtain a composite powder. The obtained composite powder was calcined at 300°C to obtain gC3N4-TiO2 composite nanoparticles.

[0009] Furthermore, the usage ratio of gC3N4 powder, TiO2 powder and methanol is 0.8-1g:0.3-0.5g:80-100mL.

[0010] Furthermore, the composite powder is calcined at 300° C. for 30-40 minutes.

[0011] A preparation process of a high-efficiency photocatalytic purification composite material comprises the following steps:

[0012] S1, dispersing 0.5 mM Cr(NO3)3·9H2O and 1 mM Zn(NO3)2·6H2O into deionized water to form a mixture, denoted as dispersion A;

[0013] S2, adding gC3N4-TiO2 composite nanoparticles into a Na2CO3 solution with a concentration of 1 mM to obtain dispersion B;

[0014] S3. Dispersion A and dispersion B are mixed, stirred and mixed evenly, and then a 1M NaOH solution is added dropwise, the pH value is maintained at 9, and the mixture is stirred and reacted at 60°C for 30 minutes, and calcined at 350°C to obtain a high-efficiency photocatalytic purification composite material.

[0015] Furthermore, in step S1, the usage ratio of Cr(NO3)3·9H2O, Zn(NO3)2·6H2O and deionized water is 5-6g:4-5g:100-150mL.

[0016] Furthermore, in step S2, the dosage ratio of gC3N4-TiO2 composite nanoparticles and Na2CO3 solution is 0.8-1g:40-50mL.

[0017] Furthermore, in step S3, the usage ratio of dispersion A, dispersion B and NaOH solution is 100-150 mL: 50-60 mL: 5-10 mL.

[0018] Furthermore, the calcination time at 350° C. is 1-1.2 h.

[0019] Beneficial effects of the present invention:

[0020] In the technical scheme of the present invention, Zn-Cr layered double hydroxide is used as an adsorption material, which can adsorb organic pollutants in wastewater. The gC3N4-TiO2 composite nanoparticles are prepared by in-situ depositing TiO2 nanoparticles on gC3N4, and then the gC3N4-TiO2 composite nanoparticles are deposited on the surface of Zn-Cr layered double hydroxide, wherein the electron transfer path from gC3N4 (-1.5eV) and TiO2 (-0.99eV) to Zn-Cr layered double hydroxide (-0.8eV) and the hole transfer path from Zn-Cr layered double hydroxide (2.6eV) and TiO2 (2.35eV) to gC3N4 (1.9eV) are established, and the energy band potentials of the three parts show multi-step characteristics, wherein the slight gradient difference of the energy bands helps to disperse the charge in multiple energy bands and provide a smaller interface resistance, thereby having a higher charge transfer efficiency and showing excellent hydrogen evolution and organic pollutant removal under sunlight. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0022] Example 1

[0023] The gC3N4-TiO2 composite nanoparticles are prepared by the following steps:

[0024] 0.8 g of gC3N4 powder and 0.3 g of TiO2 powder were mixed and dissolved in 80 mL of methanol under ultrasound, and the temperature was raised to 80°C to remove methanol to obtain a composite powder. The obtained composite powder was calcined at 300°C for 30 min to obtain gC3N4-TiO2 composite nanoparticles.

[0025] Example 2

[0026] The gC3N4-TiO2 composite nanoparticles are prepared by the following steps:

[0027] 0.9 g of gC3N4 powder and 0.4 g of TiO2 powder were mixed and dissolved in 90 mL of methanol under ultrasound, and the temperature was raised to 80°C to remove methanol to obtain a composite powder. The obtained composite powder was calcined at 300°C for 35 min to obtain gC3N4-TiO2 composite nanoparticles.

[0028] Example 3

[0029] The gC3N4-TiO2 composite nanoparticles are prepared by the following steps:

[0030] 1 g of gC3N4 powder and 0.5 g of TiO2 powder were mixed and dissolved in 100 mL of methanol under ultrasound, and the temperature was raised to 80°C to remove the methanol to obtain a composite powder. The obtained composite powder was calcined at 300°C for 40 min to obtain gC3N4-TiO2 composite nanoparticles.

[0031] Comparative Example 1

[0032] This comparative example is prepared by simply mixing 1 g of gC3N4 powder and 0.5 g of TiO2 powder.

[0033] Example 4

[0034] A preparation process of a high-efficiency photocatalytic purification composite material comprises the following steps:

[0035] S1. Disperse 5 g of 0.5 mM Cr(NO3)3·9H2O and 4 g of 1 mM Zn(NO3)2·6H2O into 100 mL of deionized water to form a mixture, which is referred to as dispersion A.

[0036] S2, adding 0.8 g of the gC3N4-TiO2 composite nanoparticles prepared in Example 1 into 40 mL of a 1 mM Na2CO3 solution to obtain a dispersion B;

[0037] S3. Mix 100 mL of dispersion A and 50 mL of dispersion B, stir and mix evenly, then drop 5 mL of 1 M NaOH solution, keep pH = 9, stir and react at 60°C for 30 minutes, and calcine at 350°C for 1 hour to obtain a high-efficiency photocatalytic purification composite material.

[0038] Example 5

[0039] A preparation process of a high-efficiency photocatalytic purification composite material comprises the following steps:

[0040] S1. Disperse 5.5 g of 0.5 mM Cr(NO3)3·9H2O and 4.5 g of 1 mM Zn(NO3)2·6H2O into 125 mL of deionized water to form a mixture, which is referred to as dispersion A.

[0041] S2, adding 0.9 g of the gC3N4-TiO2 composite nanoparticles prepared in Example 2 to 45 mL of a 1 mM Na2CO3 solution to obtain a dispersion B;

[0042] S3. Mix 125 mL of dispersion A and 55 mL of dispersion B, stir and mix evenly, then drop 7 mL of 1 M NaOH solution, keep pH = 9, stir and react at 60 ° C for 30 minutes, and calcine at 350 ° C for 1.1 hours to obtain a high-efficiency photocatalytic purification composite material.

[0043] Example 6

[0044] A preparation process of a high-efficiency photocatalytic purification composite material comprises the following steps:

[0045] S1. Disperse 6 g of 0.5 mM Cr(NO3)3·9H2O and 5 g of 1 mM Zn(NO3)2·6H2O into 150 mL of deionized water to form a mixture, which is referred to as dispersion A.

[0046] S2, adding 1 g of the gC3N4-TiO2 composite nanoparticles prepared in Example 3 to 50 mL of a 1 mM Na2CO3 solution to obtain a dispersion B;

[0047] S3. Mix 150 mL of dispersion A and 60 mL of dispersion B, stir and mix evenly, then drop 5-10 mL of 1 M NaOH solution, keep pH = 9, stir and react at 60 ° C for 30 minutes, and calcine at 350 ° C for 1.2 hours to obtain a high-efficiency photocatalytic purification composite material.

[0048] Comparative Example 2

[0049] The difference between this comparative example and Example 6 is that the gC3N4-TiO2 composite nanoparticles prepared in Example 3 are replaced by the material prepared in Comparative Example 1, and the other steps and raw materials are the same as Example 6.

[0050] The performance of a high-efficiency photocatalytic purification composite material prepared in Examples 4-6 and Comparative Example 2 was tested. 50 mg of a high-efficiency photocatalytic purification composite material prepared in Examples 4-6 and Comparative Example 2 was added to 150 mL of a 10 mg / L methyl orange solution, and the desorption equilibrium was reached under visible light irradiation. The test results are shown in Table 1 below.

[0051] Table 1

[0052] project Initial methyl orange concentration Methyl orange concentration at the end Example 4 10mg / L 1.42mg / L Example 5 10mg / L 1.36mg / L Example 6 10mg / L 1.39mg / L Comparative Example 2 10mg / L 6.44mg / L

[0053] It can be seen from Table 1 above that the high-efficiency photocatalytic purification composite material prepared in the embodiment of the present invention has higher efficiency in the photodegradation of organic matter methyl orange than that in the comparative example, wherein the electron transfer path attributed to gC3N4 (-1.5 eV) and TiO2 (-0.99 eV) to Zn-Cr layered double hydroxide (-0.8 eV) and the hole transfer path from Zn-Cr layered double hydroxide (2.6 eV) and TiO2 (2.35 eV) to gC3N4 (1.9 eV) are established.

[0054] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0055] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A high-efficiency photocatalytic purification composite material, characterized by: The invention comprises a Zn-Cr layered double hydroxide and a gC3N4-TiO2 composite nanoparticle deposited on the Zn-Cr layered double hydroxide, wherein TiO2 is deposited on the gC3N4, the gC3N4 loaded with TiO2 is deposited on the Zn-Cr layered double hydroxide, and a conduction band that decreases in sequence is formed between the gC3N4, the TiO2 and the Zn-Cr layered double hydroxide; The gC3N4-TiO2 composite nanoparticles are prepared by the following steps: Under ultrasound, gC3N4 powder and TiO2 powder are mixed and dissolved in methanol, and the temperature is raised to 80°C to remove methanol to obtain composite powder. The obtained composite powder is calcined at 300°C to obtain gC3N4-TiO2 composite nanoparticles; the gC3N4 is graphite phase carbon nitride.

2. The high-efficiency photocatalytic purification composite material according to claim 1, characterized in that: The usage ratio of gC3N4 powder, TiO2 powder and methanol is 0.8-1g:0.3-0.5g:80-100mL.

3. The high-efficiency photocatalytic purification composite material according to claim 1, characterized in that: The composite powder is calcined at 300°C for 30-40 minutes.

4. A process for preparing a high-efficiency photocatalytic purification composite material according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, dispersing 0.5 mM Cr(NO3)3·9H2O and 1 mM Zn(NO3)2·6H2O into deionized water to form a mixture, denoted as dispersion A; S2, adding gC3N4-TiO2 composite nanoparticles into a Na2CO3 solution with a concentration of 1 mM to obtain dispersion B; S3. Dispersion A and dispersion B are mixed, stirred and mixed evenly, and then a 1M NaOH solution is added dropwise, the pH value is maintained at 9, and the mixture is stirred and reacted at 60° C. for 30 minutes, and calcined at 350° C. to obtain a high-efficiency photocatalytic purification composite material.

5. The preparation process of a high-efficiency photocatalytic purification composite material according to claim 4, characterized in that: In step S1, the usage ratio of Cr(NO3)3·9H2O, Zn(NO3)2·6H2O and deionized water is 5-6g:4-5g:100-150mL.

6. The preparation process of a high-efficiency photocatalytic purification composite material according to claim 4, characterized in that: In step S2, the dosage ratio of gC3N4-TiO2 composite nanoparticles and Na2CO3 solution is 0.8-1g:40-50mL.

7. The process for preparing a high-efficiency photocatalytic purification composite material according to claim 4, characterized in that: In step S3, the usage ratio of dispersion A, dispersion B and NaOH solution is 100-150 mL: 50-60 mL: 5-10 mL.

8. The process for preparing a high-efficiency photocatalytic purification composite material according to claim 4, characterized in that: The calcination time at 350°C is 1-1.2h.