CN116532121A - Preparation method of zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater - Google Patents

Abstract

The invention discloses a preparation method of a zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater, which adopts a sol-gel method to prepare a novel nano zinc oxide composite material, takes zinc oxide as a substrate and composites gamma-Fe ₂ O ₃ The semiconductor is doped with Al ions, and the prepared novel material has obvious improvement on the degradation efficiency of printing and dyeing wastewater such as methyl orange under the condition of visible light compared with nano zinc oxide. The transition metal doping can form more oxygen vacancies and promote the effective separation of photo-generated electron-hole pairs; the semiconductor composition can effectively increase the specific surface area of the semiconductor, increase the absorption spectrum of the semiconductor, and have different forbidden band widthsThe recombination can effectively realize the separation of electron hole pairs, and as the photocatalytic activity is improved from different angles by the two methods, the photocatalytic intensity of zinc oxide can be further improved by combining the two methods.

Description

A preparation method of zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater

technical field

The invention relates to the field of sewage treatment, in particular to the preparation of nanometer zinc oxide composite material, in particular to a preparation method of zinc oxide composite material used for photocatalytic treatment of printing and dyeing wastewater.

Background technique

With the progress of the times and the development of science and technology, a large amount of industrial wastewater will be discharged into the surrounding water bodies in the fields of textile, printing and dyeing, coating, medicine and other fields, causing serious pollution. The huge quantity and unpredictable composition undoubtedly increase the difficulty of the treatment of organic dyes. Traditional industrial wastewater treatment methods mainly include physical methods such as adsorption and membrane filtration, chemical methods such as electrochemical methods and advanced oxidation methods, and biochemical methods. However, these methods There are problems such as high energy consumption, high cost, and unsatisfactory treatment effect. The semiconductor composite material uses light energy to generate hole-electron pairs, and the electron holes on the surface active sites are respectively used as reducing agents and oxidizing agents to promote redox reactions, thereby completely decomposing organic pollutants in sewage into small molecular inorganic substances , is persistent and has no secondary pollution, and has received widespread attention. Therefore, in recent years, inorganic semiconductor-based photocatalysts have important application prospects in the field of degradation of organic pollutants and have attracted widespread attention.

Zinc oxide is one of the important semiconductor materials of II-VI group, which belongs to N-type semiconductor. Because of its excellent thermal stability and non-toxic characteristics, it is widely used in the fields of coatings, electronics, photocatalysis and sensors. In the field of photocatalysis, because the band gap energy of zinc oxide is 3.37eV, this limits the most efficient catalytic degradation of zinc oxide under ultraviolet light irradiation, and the efficiency under natural visible light is not high, but in actual work In the environment, continuous use of ultraviolet light is not as good as natural visible light in terms of cost and environmental protection. The catalytic degradation efficiency of zinc oxide under visible light is not high mainly because the band gap energy of zinc oxide determines that it can only use the ultraviolet part of sunlight, and the proportion of ultraviolet light in natural light is very small, only 4%, which also leads to the low efficiency of ZnO under visible light.

At present, the following two methods are commonly used for the problem of ZnO bandgap energy: 1. Using the compounding of transition metal ions, introducing transition metal cations into ZnO can change the coordination environment of Zn in the crystal lattice and change the electrons of ZnO. energy band structure. Generally, metal sites are considered to act as trap sites to accept photogenerated electrons or holes generated by semiconductors and inhibit the recombination of carriers, thereby enhancing the photocatalytic activity of semiconductors. Therefore, the current research is to modify ZnO by introducing different transition metal cations into the lattice. 2. Semiconductor recombination. Combining two or more semiconductors can not only increase the absorption in the visible light region, but also reduce the recombination of carriers, thereby improving the photocatalytic activity. Due to the conduction bands of different energy levels between the semiconductors, the photoexcited electrons can quickly transfer from one semiconductor to the adjacent semiconductor, thereby accelerating the separation of electron-hole pairs and improving the photocatalytic activity.

Contents of the invention

Transition metal doping can form more oxygen vacancies, which can promote the effective separation of photogenerated electron-hole pairs; semiconductor recombination can effectively increase the specific surface area of semiconductors, increase the absorption spectrum of semiconductors, and semiconductor recombination with different band gaps can be effectively realized The separation of electron-hole pairs, since the two methods improve the photocatalytic activity from different angles, the combination of the two methods can further improve the photocatalytic intensity of zinc oxide. In summary, the present invention provides a preparation method of a novel nano-zinc oxide material with higher photocatalytic activity and better effect in degrading printing and dyeing wastewater.

The present invention is achieved through the following technical solutions:

(1) First, weigh an appropriate amount of Zn(CH3COO) ₂ (0.2mol/L) and FeCl ₃ (0.1mol/L) and add them into a 100mL beaker.

(2) The mixed solution of the two was magnetically stirred for 10 min.

(3) Add 16mL KOH (2mol/L) dropwise to the mixed solution and stir for 30min.

(4) Accurately weigh an appropriate amount of aluminum nitrate nonahydrate, put it into a beaker, add ethanol as a solvent, and dissolve it completely, add it to a 100mL volumetric flask and dilute to volume with ethanol, and set aside.

(5) Use a pipette to pipette 1 mL of the prepared aluminum salt solution into the mixed solution after step (3), and stir on a magnetic stirrer for 30 min.

(6) Transfer the liquid in the above beaker to a crucible and put it into a muffle furnace, set the calcination temperature to 500° C., and set the time to 3 hours.

(7) After the reaction is finished, when the product is cooled to room temperature, the product is taken out. The product was centrifuged and washed (the product was washed with deionized water and ethanol, respectively).

(8) Finally, put the product into a vacuum drying oven and dry at 50°C for 24 hours to obtain a khaki product.

The improvement effects of the present invention are as follows: γ-Fe2O3 provides more reactive sites for ZnO, increases the specific surface area and light absorption of ZnO, effectively reduces the energy band width, and improves its photocatalytic reactivity. At the same time, the doping of aluminum ions makes the particle distribution of zinc oxide more uniform and the particle size is relatively consistent, which all play a role in strengthening the photocatalytic degradation ability.

Description of drawings

Figure 1 is a schematic diagram of zinc oxide photocatalytic degradation of printing and dyeing wastewater

Detailed ways

Unless otherwise stated, implied from the context, or customary in the art, the testing and characterization methods employed are current as of the filing date of this application. Where applicable, the contents of any patent, patent application, or publication referred to in this application are hereby incorporated by reference, and equivalent patent families are also incorporated by reference, especially those disclosed by these documents with respect to the state of the art. Definition of synthesis techniques, product and process design, etc. If the definition of a specific term disclosed in the prior art is inconsistent with any definition provided in the present application, the definition of the term provided in the present application shall prevail.

Example 1

A new type of nano-zinc oxide material is realized through the following approaches:

(1) First, weigh 40ml of Zn(CH3COO) ₂ (0.2mol/L) and 4ml of FeCl ₃ (0.1mol/L) into a 100mL beaker.

(2) The mixed solution of the two was magnetically stirred for 10 min.

(3) Add 16mL KOH (2mol/L) dropwise to the mixed solution and stir for 30min.

(4) Accurately weigh 25g of aluminum nitrate nonahydrate, put it into a beaker, add ethanol as a solvent, and dissolve it, add it to a 100mL volumetric flask and dilute to volume with ethanol, and set aside.

(5) Use a pipette to pipette 1 mL of the prepared aluminum salt solution into the mixed solution after step (3), and stir on a magnetic stirrer for 30 min.

(6) Transfer the liquid in the above beaker to a crucible and put it into a muffle furnace, set the calcination temperature to 500° C., and set the time to 3 hours.

(7) After the reaction is finished, when the product is cooled to room temperature, the product is taken out. The product was centrifuged and washed (the product was washed with deionized water and ethanol, respectively).

(8) Finally, put the product into a vacuum drying oven and dry at 50°C for 24 hours to obtain a khaki product.

The atomic ratio of Fe and Zn in the novel nano-zinc oxide material obtained in this example is 1:20, and the molar ratio of Al atoms is 5%. According to X-ray diffraction, ultraviolet spectrophotometer, scanning electron microscope, and photocatalytic experimental analysis of printing and dyeing wastewater represented by methyl orange solution under visible light, the γ-Fe ₂ O ₃ loaded with Al ions at the same time The long-wavelength light absorption ability of zinc oxide has been significantly increased, which shows that the absorption ability of the new material for incident light is enhanced compared with pure zinc oxide, which can stimulate more photogenerated carriers, thereby improving photocatalytic degradation. ability. At the same time, after repeated experiments, the degradation efficiency of the methyl orange solution is above 95%, which shows that the new nano-zinc oxide material has high photocatalytic stability and can be reused many times.

Example 2

The atomic ratio of Fe and Zn in the novel nano-zinc oxide material obtained in this embodiment is 1:50, and the molar ratio of Al atoms is 5%. Other technical characteristics are identical with embodiment 1. According to X-ray diffraction, ultraviolet spectrophotometer, scanning electron microscope and photocatalytic experimental analysis of printing and dyeing wastewater represented by methyl orange solution under visible light, the photocatalytic effect of the new nano-zinc oxide material is also better than that of pure zinc oxide. However, with the decrease of the loaded γ-Fe ₂ O ₃ , the specific surface area decreases, the number of active sites decreases, and the photocatalytic efficiency decreases.

Example 3

The atomic ratio of Fe and Zn in the novel nano-zinc oxide material obtained in this example is 1:100, and the molar ratio of Al atoms is 5%. Other technical characteristics are identical with embodiment 1. According to X-ray diffraction, ultraviolet spectrophotometer, scanning electron microscope and photocatalytic experimental analysis of printing and dyeing wastewater represented by methyl orange solution under visible light, the photocatalytic effect of the new nano-zinc oxide material is also better than that of pure zinc oxide. However, with the reduction of the loaded γ-Fe ₂ O ₃ , the specific surface area is reduced, and the band gap of the new material is also reduced. The energy barrier for photo-generated electrons to transition from the valence band to the conduction band The degree of reduction has also decreased, which is not conducive to the conduction of photogenerated electrons, so the photocatalytic activity has decreased compared with Example 1.

Example 4

The atomic ratio of Fe and Zn in the novel nano-zinc oxide material obtained in this example is 1:20, and the molar ratio of Al atoms is 1%. Other technical characteristics are identical with embodiment 1. According to X-ray diffraction, ultraviolet spectrophotometer, scanning electron microscope, and photocatalytic experimental analysis of printing and dyeing wastewater represented by methyl orange solution under visible light, when the doping ratio of Al is 1%, the new nano-zinc oxide material The average particle size of ZnO is not much different from that of pure nano-zinc oxide, which is not conducive to the occurrence of photocatalytic reaction, and the improvement of photocatalytic activity is also relatively low.

Example 5

The atomic ratio of Fe and Zn in the novel nano-zinc oxide material obtained in this example is 1:20, and the molar ratio of Al atoms is 15%. Other technical characteristics are identical with embodiment 1. According to X-ray diffraction, ultraviolet spectrophotometer, scanning electron microscope and photocatalytic experimental analysis of printing and dyeing wastewater represented by methyl orange solution under visible light, when the doping ratio of Al is 15%, the effect of photocatalytic degradation It is lower than that of Example 1, because the Al doping amount is too large to cause Al to become electron and ion vacancies, resulting in a decline in photocatalytic efficiency.

It can be seen from Examples 1 to 5 that the present invention provides more reactive sites for zinc oxide in γ-Fe ₂ O ₃ by adjusting the ratio of doped Al ions to the required γ-Fe ₂ O ₃ , increasing the specific surface area and light absorption of zinc oxide, effectively reducing the energy band width, and at the same time, the doping of Al will also increase the visible light absorption of the solution containing aluminum-doped zinc oxide powder to a certain extent, providing for The utilization efficiency of visible light improves its photocatalytic activity. During the experiment, it was found that when the atomic ratio of Fe to Zn is 1:20 and the molar ratio of Al atoms is 5%, the effect of improving photocatalytic activity is the most significant.

The above description of the embodiments is for those of ordinary skill in the art to understand and apply the present application. It will be apparent to those skilled in the art that various modifications to these embodiments can be easily made, and the general principles described here can be applied to other embodiments without creative efforts. Therefore, the present application is not limited to the embodiments here, and improvements and modifications made by those skilled in the art based on the content disclosed in the present application without departing from the scope and spirit of the present application are within the scope of the present application.

Claims (9)

1. A zinc oxide composite material for treating dyeing waste water by photocatalysis features that oxygen is used as catalystZinc oxide and gamma-Fe ₂ O ₃ Compounding and simultaneously doping Al ions and gamma-Fe ₂ O ₃ The proportion of the Al ions is required to be configured, and the proportion is as follows: the atomic ratio of Fe to Zn is 1: 20. 1:50 or 1:100, and the molar ratio of Al atoms is 1%,5% or 15%.

2. A method for preparing the zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater according to claim 1, which is characterized by comprising the following steps:

(1) Firstly, weighing a proper amount of Zn (CH 3 COO) ₂ Solution and FeCl ₃ Adding the solution into a beaker;

(2) Magnetically stirring the mixed solution of the two;

(3) Dropwise adding KOH solution into the mixed solution and stirring;

(4) Accurately weighing a proper amount of aluminum nitrate nonahydrate, putting the aluminum nitrate nonahydrate into a beaker, adding ethanol as a solvent, completing dissolution, adding the aluminum nitrate nonahydrate into a volumetric flask, and using the ethanol to fix the volume for standby;

(5) Transferring a proper amount of the aluminum salt solution prepared in the step (4) by using a pipette, putting the aluminum salt solution into the mixed solution after the step (3) is completed, and stirring by using a magnetic stirrer;

(6) Transferring the liquid in the beaker into a crucible, and placing the crucible into a muffle furnace for calcination;

(7) After the reaction is finished, taking out the product when the reaction is cooled to room temperature; centrifugal washing is carried out on the product, and deionized water and ethanol are respectively used for washing the product;

(8) Finally, the product is put into a vacuum drying oven to be dried, and then the earthy yellow product is obtained.

3. The method for producing a zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein Zn (CH 3 COO) in step (1) is contained in the raw material ₂ The solution is 0.2mol/L, feCl ₃ The solution was 0.1mol/L.

4. The method for producing a zinc oxide composite for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the magnetic stirring time in the step (2) is 10min.

5. The method for producing a zinc oxide composite for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the KOH solution in step (3) is 16ml, the concentration is 2mol/L, and the stirring time is 30min.

6. The method for producing a zinc oxide composite for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the gauge of the volumetric flask in the step (4) is 100ml.

7. The method for producing a zinc oxide composite for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the stirring time in the step (5) is 30min.

8. The method for preparing the zinc oxide composite material for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the muffle furnace calcining temperature in the step (6) is 500 ℃ and the time is 3h.

9. The method for producing a zinc oxide composite for photocatalytic treatment of printing and dyeing wastewater according to claim 2, wherein the vacuum drying oven temperature in step (8) is set to 50 ℃ for 24 hours.