CN110560089B - Zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst and a preparation method thereof. In the zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst, the halloysite has a nanotube structure, and the zinc-cadmium-sulfur dispersed and grown on the surface of the bismuth-doped halloysite. The invention adopts a one-step solvothermal method to prepare modified bismuth-doped halloysite, which is combined with zinc-cadmium-sulfur ultrasonically to form a composite photocatalyst. The zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst of the invention has good dispersibility and many active sites, is used for photocatalytic degradation of 10 mg/L rhodamine B, and exhibits excellent catalytic performance, and the degradation rate reaches 60 minutes within 60 minutes. 85% or more.

Description

Zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst and preparation method thereof

technical field

The invention relates to a zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst and a preparation method thereof, belonging to the technical field of nanomaterial preparation.

Background technique

Photocatalytic technology utilizes the unique light and electrical conversion properties of materials to convert solar energy into chemical energy, obtain energy substances including hydrogen and hydrocarbons, and remove pollutants and bacteria. However, the existing photocatalysts have limited their applications due to their low light utilization rate, high photogenerated electron recombination rate, and few surface active sites. The photocatalytic performance can be improved by modifying the photocatalyst, and the modification methods include noble metal doping, semiconductor compounding, introducing defects or heteroatoms, adding photosensitizers, etc.

Halloysite is a natural clay-like silicate mineral with the advantages of large specific surface area, abundant reserves, good thermal stability and uniform structure. The chemical composition of halloysite is similar to that of kaolin, and the chemical formula is Al ₂ Si ₂ O ₅ (OH) ₄ ·nH ₂ O (n=0, 2), which consists of the spatial mismatch between aluminum oxide octahedra and silicon oxide tetrahedra Dislocations form tubular structures. The inner surface of the halloysite microtube is Al-OH, which is negatively charged, and the outer surface is O-Si-O group, which is positively charged. Therefore, halloysite can make most metal particles or ions (Pt, Fe ³⁺ , Ag ⁺ etc.), metal compounds (Fe ₃ O ₄ , CdS, CuO, etc.) and polymers (polyaniline, polythiophene, etc.) etc.) evenly loaded on the halloysite. Siva Kumar-Krishnan et al. Surface functionalized halloysite nanotubes by silver nanoparticle modification for enzyme immobilization and biosensing [Siva Kumar-Krishnan, et al. (2016)."Surface functionalized halloysite nanotubesdecorated with silvernanoparticles for enzyme immobilization and biosensing." J. Mater. Chem. B, 4, 2553-2560.]. Xing, WN et al. prepared CdS-halloysite composites by hydrothermal method for tetracycline degradation with high photocatalytic activity [Xing, WN, et al. (2012)."Preparation high photocatalytic activity of CdS/halloysite nanotubes (HNTs ) nanocomposites with hydrothermal method. "Applied Surface Science, 259, 698-704.]. Zhou, TZ, et al. Preparation of halloysite@polyaniline (HNT@PANI) core-shell nanocomposite nanotubes by in-situ polymerization with efficient Cr(VI) adsorption and reduction [Zhou, TZ, et al. (2017)."Effective Adsorption/Reduction of Cr(VI)Oxyanion by Halloysite@Polyaniline Hybrid Nanotubes."ACS Appl.Mater.Interfaces,9,6030-6043]. Yin, LX, et al. hydrothermally prepared Zn _0.2 Cd _0.8 S microspheres to degrade only 50% of 10 mg/L RhB within 60 min [Yin, LX, et al. (2019)."Constructing 3D hierarchical Zn _0.2 Cd _0.8 Smicrospheres for theimproved visible-light-driven photocatalytic performance." International Journal of Hydrogen Energy, doi: 10.1016]. The above modification methods all use natural silicate as a carrier, and do not use halloysite as a photocatalyst to participate in the photocatalytic reaction, and at the same time prepare a single zinc-cadmium-sulfur nanocrystal with agglomeration phenomenon.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst with excellent catalytic performance and a preparation method thereof.

The technical scheme that realizes the object of the present invention is:

The preparation method of zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst comprises the following steps:

Step 1, uniformly disperse the halloysite in the saturated aluminum trichloride solution, add the ethylene glycol solution of bismuth nitrate pentahydrate, stir and mix evenly, carry out a solvothermal reaction at 160-180 ° C, and naturally cool after the reaction is completed , centrifuged, washed, and dried to obtain bismuth-doped halloysite;

Step 2, ultrasonically dispersing bismuth-doped halloysite in water, adding cadmium acetate dihydrate and zinc acetate dihydrate, ultrasonically stirring, adding thioacetamide, ultrasonically stirring for reaction, centrifuging, washing, and drying to obtain zinc-cadmium-sulfur- Bismuth-doped halloysite composite photocatalyst.

Preferably, in step 1, the molar ratio of the bismuth nitrate pentahydrate and the halloysite is 1:5.

Preferably, in step 1, the halloysite is first ultrasonically dispersed in a saturated aluminum trichloride solution, and then stirred until the mixture is uniform.

Preferably, in step 1, the stirring and mixing time is more than 0.5h, and the solvothermal reaction is more than 24h.

Preferably, in step 1, the centrifugal speed is 9000r/min, and the drying temperature is 60-80°C.

Preferably, in step 2, the molar ratio of cadmium acetate dihydrate, zinc acetate dihydrate and thioacetamide is 1:4:5.

Preferably, in step 2, the ratio of the bismuth-doped halloysite to thioacetamide is 100 mg:1 mmol.

Preferably, in step 2, the ultrasonic stirring reaction time is more than 2h, the centrifugal speed is 9000r/min, and the drying temperature is 60-80°C.

The zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst prepared by the above preparation method of the present invention is microscopically in the form of a nanotube structure, and zinc-cadmium-sulfur is dispersed and grown on the surface of the bismuth-doped halloysite.

Compared with the prior art, the present invention has the following advantages:

(1) The modified bismuth-doped halloysite was prepared by one-step solvothermal method, and composited with zinc-cadmium-sulfur ultrasonically to form a composite photocatalyst; (2) The raw material halloysite was rich in resources, cheap and easy to obtain, and the pretreatment method was simple; ( 3) The zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst of the present invention is used for photocatalytic degradation of 10 mg/L rhodamine B, showing excellent catalytic performance, and the degradation rate reaches more than 85% within 60 minutes.

Description of drawings

Fig. 1 is the synthetic route diagram of the preparation method of the present invention.

2 is an optical image of the unmodified halloysite nanotubes (A) prepared in Example 1 and the bismuth-doped halloysite (B).

FIG. 3 is a doping atomic model diagram of the bismuth-doped halloysite prepared in Example 1. FIG.

Figure 4 shows undoped halloysite nanotubes (A), bismuth doped halloysite nanotubes (B), ZnCdS-halloysite nanocomposites (C), ZnCdS-bismuth doped Angstroms High-resolution transmission electron microscopy images of the rocky nanocomposites (D and E), zinc-cadmium-sulfur nanoparticles (F).

5 is a transmission electron microscope image of the zinc-cadmium-sulfur-bismuth-doped halloysite prepared in Comparative Example 1 (A) and Comparative Example 2 (B).

FIG. 6 is the XRD diffraction patterns of the materials prepared in Example 1, Example 2 and Comparative Example 1. FIG.

7 is a graph showing the catalytic performance of the zinc-cadmium-sulfur-bismuth-doped halloysite prepared in Example 2 and Comparative Example 1.

Detailed ways

The present invention will be described in further detail below in conjunction with the embodiments and the accompanying drawings.

Fig. 1 is the synthesis mechanism diagram of the preparation method of the present invention, after halloysite pretreatment, it is dispersed in saturated aluminum chloride solution; bismuth nitrate pentahydrate is dispersed in ethylene glycol. The above solutions are mixed, transferred to a polytetrafluoroethylene reactor, taken out after solvothermal reaction, centrifugally washed and dried to obtain a bismuth-doped halloysite material. Then, Bi-doped halloysite was dispersed in deionized water, and cadmium acetate dihydrate, zinc acetate dihydrate and thioacetamide were added in sequence, after ultrasonic stirring, centrifugal washing and drying to obtain zinc-cadmium-sulfur-bismuth-doped halloysite composite Material.

Example 1

In the first step, 1.5 mmol halloysite (258 g/mol) was mixed with saturated aluminum chloride solution, ultrasonically dispersed for 10 min, and then placed on a magnetic stirrer and stirred for 0.5 h;

In the second step, take 0.3mmol of bismuth nitrate pentahydrate (1:5 molar ratio with halloysite) and disperse it in 5mL of ethylene glycol solution and ultrasonically for 10min;

In the third step, the solution obtained in the second step was added dropwise to the suspension obtained in the first step and transferred to a 100 mL polytetrafluoroethylene reaction kettle, and then taken out after being solvothermally heated in an oven at 180 °C for 24 hours;

In the fourth step, the sample in the third step is centrifugally washed, and dried in an oven at 60° C. for 12 hours to obtain a modified bismuth-doped halloysite nanomaterial.

2 is an optical image of the unmodified halloysite nanotubes (A) prepared in Example 1 and the bismuth-doped halloysite (B). It can be seen from the figure that the modified bismuth-doped halloysite changed from yellowish to gray-black, indicating that the doping was successful. 3 is a model diagram of the doping atoms of the bismuth-doped halloysite prepared in Example 1, in the saturated aluminum chloride solution environment, it is favorable for the aluminum atoms in the aluminum-oxygen octahedron to be replaced by the bismuth atoms.

Example 2

In the first step, 100 mg of bismuth-doped halloysite was dispersed in 50 mL of deionized water, and ultrasonically dispersed for more than 30 minutes;

In the second step, quantitatively add 0.8mmol of cadmium acetate dihydrate and 0.2mmol of zinc acetate dihydrate (mol ratio 8:2) to the solution obtained in the first step, and ultrasonically stir for more than 1h;

In the third step, 1 mmol of thioacetamide was added to the solution obtained in the second step, and ultrasonic mechanical stirring was performed for 2 h;

In the fourth step, the samples in the third step were centrifuged and washed, and dried in an oven at 60° C. for 12 hours to obtain a zinc-cadmium-sulfur-bismuth-doped halloysite composite material (named ZCS/Bi-HNT-1).

Example 3

In the first step, 20 mg of zinc-cadmium-sulfur-bismuth-doped halloysite was dispersed in 50 mL of 10 mg/L Rhodamine B solution, and stirred in a dark room for 1 h;

In the second step, the suspension obtained in the first step is placed under a 300W xenon lamp (λ>420nm) for illumination, and 3 mL of liquid is placed at an interval of 10 minutes;

In the third step, the liquid sample obtained in the second step was centrifuged at 9000 r/min for 1 min to remove the catalyst;

In the fourth step, the centrifuged liquid obtained in the third step is detected in an ultraviolet-visible spectrophotometer to evaluate the photocatalytic performance.

Comparative Example 1

In the first step, 100 mg of modified halloysite was dispersed in 50 mL of deionized water, and ultrasonically dispersed for more than 30 minutes;

In the second step, 0.8 mmol of cadmium acetate dihydrate and 0.2 mmol of zinc acetate dihydrate (mol ratio 8:2) were quantitatively added to the solution obtained in the first step, and ultrasonically stirred for 1 h;

In the third step, the solution obtained in the second step was added with 1mmol of thioacetamide, and the ultrasonic mechanical stirring was performed for 2h;

In the fourth step, the sample in the third step is centrifuged and washed, and dried in an oven at 60° C. for 12 hours to obtain a zinc-cadmium-sulfur-halloysite composite material.

Comparative Example 2

In the first step, 100 mg of bismuth-doped halloysite was dispersed in 50 mL of deionized water, and ultrasonically dispersed for more than 30 minutes;

In the second step, quantitatively add 0.4mmol of cadmium acetate dihydrate and 0.1mmol of zinc acetate dihydrate (mol ratio 8:2) to the solution obtained in the first step, and ultrasonically stir for more than 1h;

In the third step, 0.5 mmol of thioacetamide was added to the solution obtained in the second step, and ultrasonic mechanical stirring was performed for 2 h;

In the fourth step, the samples in the third step were centrifuged and washed, and dried in an oven at 60° C. for 12 hours to obtain a zinc-cadmium-sulfur-bismuth-doped halloysite composite material (ZCS/Bi-HNT-0.5).

Comparative Example 3

In the first step, 100 mg of bismuth-doped halloysite was dispersed in 50 mL of deionized water, and ultrasonically dispersed for more than 30 minutes;

In the second step, quantitatively add 1.6 mmol of cadmium acetate dihydrate and 0.4 mmol of zinc acetate dihydrate (mol ratio 8:2) to the solution obtained in the first step, and ultrasonically stir for more than 1 h;

The third step, the solution obtained in the second step was added with 2mmol of thioacetamide, and the ultrasonic mechanical stirring was performed for 2h;

In the fourth step, the samples in the third step were centrifuged and washed, and dried in an oven at 60° C. for 12 hours to obtain a zinc-cadmium-sulfur-bismuth-doped halloysite composite material (ZCS/Bi-HNT-2).

Figure 4 shows undoped halloysite nanotubes (A), bismuth doped halloysite nanotubes (B), ZnCdS-halloysite nanocomposites (C), ZnCdS-bismuth doped Angstroms High-resolution transmission electron microscopy images of the rocky nanocomposites (D and E), zinc-cadmium-sulfur nanoparticles (F).

5 is a transmission electron microscope image of the zinc-cadmium-sulfur-bismuth-doped halloysite prepared in Comparative Example 1 (A) and Comparative Example 2 (B). A is the composite ratio of zinc-cadmium-sulfur and bismuth-doped halloysite 0.5mmol:100mg (ZCS/Bi-HNT-0.5), B is the composite ratio of zinc-cadmium-sulfur and bismuth-doped halloysite 2mmol:100mg (ZCS/Bi- HNT-2). It can be seen from the figure that when the input ratio of ZnCdS is less than the optimal ratio, some bismuth-doped halloysite nanotubes do not grow on ZnCdS nanoparticles; when the input ratio of ZnCdS is greater than the optimal ratio, there is zinc Agglomeration of cadmium-sulfur nanoparticles.

FIG. 6 is the XRD diffraction patterns of the materials prepared in Example 1, Example 2 and Comparative Example 1. FIG. Comparing the X-ray diffraction patterns of halloysite and bismuth-doped halloysite, when 2θ=12.2°, the diffraction peak of bismuth-doped halloysite slightly shifts to a small angle, which is because the radius of Bi ³⁺ is larger than that of Al ³⁺ , which also verifies the successful doping of bismuth.

7 is a graph showing the catalytic performance of the zinc-cadmium-sulfur-bismuth-doped halloysite prepared in Example 2 and Comparative Example 1. It can be seen from the figure that the photocatalytic effects of ZnCdS-halloysite and ZnCdS-Bismuth doped halloysite composite photocatalysts are better than those of undoped halloysite within 60 min. The degradation rate of -bismuth doped halloysite is higher than that of ZnCdS-halloysite, indicating the excellent photocatalytic activity of ZnCdS-bismuth doped halloysite. In summary, ZnCdS has good dispersibility on the modified halloysite, and the bismuth-doped halloysite is closely combined with ZnCdS, which increases the effective specific surface area and active sites of the catalytic reaction, and improves the efficiency of the catalytic reaction. Therefore, the zinc-cadmium-sulfur-bismuth-doped halloysite composite material prepared by the present invention has excellent photocatalytic performance as a photocatalyst.

Claims (8)

1. The preparation method of the zinc-cadmium-sulfur-bismuth doped halloysite composite photocatalyst is characterized by comprising the following steps of:

Step 1, uniformly dispersing halloysite in a saturated aluminum trichloride solution, adding a glycol solution of bismuth nitrate pentahydrate, stirring and mixing uniformly, carrying out solvothermal reaction at 160-180 ℃, naturally cooling after the reaction is finished, centrifuging, washing, and drying to obtain bismuth-doped halloysite;

and 2, ultrasonically dispersing bismuth-doped halloysite in water, adding cadmium acetate dihydrate and zinc acetate dihydrate, ultrasonically stirring, adding thioacetamide, ultrasonically stirring for reaction, centrifuging, washing and drying to obtain the zinc-cadmium-sulfur-bismuth-doped halloysite composite photocatalyst, wherein the molar ratio of the cadmium acetate dihydrate, the zinc acetate dihydrate and the thioacetamide is 1:4:5, and the ratio of the bismuth-doped halloysite to the thioacetamide is 100mg:1 mmol.

2. The method according to claim 1, wherein in step 1, the molar ratio of bismuth nitrate pentahydrate to halloysite is 1: 5.

3. the method according to claim 1, wherein in step 1, the halloysite is ultrasonically dispersed in a saturated aluminum trichloride solution and then stirred until the mixture is uniformly mixed.

4. The process according to claim 1, wherein in the step 1, the stirring and mixing time is 0.5 hours or more, and the solvothermal reaction time is 24 hours or more.

5. The method according to claim 1, wherein in step 1, the centrifugation rate is 9000r/min, and the drying temperature is 60-80 ℃.

6. The preparation method according to claim 1, wherein in the step 2, the ultrasonic stirring reaction time is more than 2h, the centrifugal rate is 9000r/min, and the drying temperature is 60-80 ℃.

7. The zinc-cadmium-sulfur-bismuth doped halloysite composite photocatalyst prepared by the preparation method according to any one of claims 1 to 6.

8. The application of the zinc-cadmium-sulfur-bismuth doped halloysite composite photocatalyst in photocatalytic degradation of organic dyes according to claim 7.

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