Photocatalyst for degrading xanthate as well as application method and preparation method thereof

Abstract

The invention discloses a photocatalyst for degrading xanthate as well as an application method and a preparation method of the photocatalyst, and relates to the field of photocatalysis, in particular to a preparation method of a NiFe2O4 / ZnIn2S4 magnetic photocatalyst for degrading xanthate. The NFO / ZIS used as the photocatalyst can effectively inhibit electron-hole pair compounding, and in the xanthate degradation process, the degradation performance shown by the composite photocatalyst NFO / ZIS is better than that shown by two monomers. The photocatalyst is formed by compounding ZnIn2S4 and NiFe2O4 according to the mass ratio of 100: x, and the ZIS photocatalyst loaded with x% of NFO is formed. The compounded catalyst has magnetism and is convenient to recycle, and the application cost is reduced. The compounding method is simple and high in feasibility, and has great research value in the aspects of beneficiation wastewater treatment and environmental protection.

Description

Technical Field

[0001] The invention relates to the field of photocatalysis, and in particular to a method for preparing a NiFe2O4 / ZnIn2S4 magnetic photocatalyst for degrading xanthate. Background Art

[0002] Xanthate is often used as a flotation agent in industry. A certain amount of xanthate will remain in the flotation wastewater. The natural degradation rate of xanthate in the environment is slow. If it is discharged directly without treatment, it will cause serious damage to the ecosystem.

[0003] Traditional technologies for treating xanthate, such as chemical precipitation, will produce a large amount of solid waste, which requires further treatment. At the same time, its treatment effect is greatly affected by the pH value of the wastewater and the amount of precipitant used, and a large amount of chemical reagents are required, which increases the operating cost. The activated carbon adsorption method has a limited adsorption capacity and needs to be replaced regularly, which is costly, and the adsorption efficiency will also decrease with the increase in the use time of the activated carbon. The oxidation method requires a large amount of oxidant during the oxidation process, which not only greatly increases the cost, but also produces harmful by-products. The biodegradation method has a slow degradation rate, takes a long time, and the degradation conditions are also more harsh. The contradiction between the shortcomings of traditional technology and market demand has stimulated people to develop a new method with high efficiency, low cost, and less environmental pollution. Driven by many parties, relevant technicians have turned their attention to photocatalytic technology.

[0004] However, traditional photocatalysts have some shortcomings in the photocatalytic process, such as low light utilization efficiency, poor stability, and difficulty in recycling, which limit their industrial application prospects. In order to solve these problems, researchers are constantly developing new photocatalysts, such as narrow bandgap semiconductor materials and composite materials, to improve photocatalytic efficiency, stability and selectivity. Among them, ZIS is a narrow bandgap semiconductor that can respond to visible light and can effectively utilize solar energy; in addition, it has high chemical stability and is not easily corroded, making it an environmentally friendly material, but ZIS also has the problem of rapid recombination of electron-hole pairs. For this reason, researchers considered combining ZIS with other photocatalysts. Because NFO has a narrow bandgap and can respond to visible light, combining the two helps solve the problem of rapid recombination of electron-hole pairs, thereby improving photocatalytic efficiency. Summary of the invention

[0005] In view of the above problems, the present invention proposes a NiFe2O4 / ZnIn2S4 magnetic photocatalyst for degrading xanthate and its application method and preparation method. Using NFO / ZIS as a photocatalyst can effectively inhibit the recombination of electron-hole pairs. In the process of degrading xanthate, the degradation performance exhibited by the composite photocatalyst NFO / ZIS is also better than that of the two monomers.

[0006] The technical solution of the present invention is: the photocatalyst is a composite of ZnIn2S4 and NiFe2O4 in a mass ratio of 100:x, forming a ZIS (abbreviation of ZnIn2S4) photocatalyst loaded with x% NFO (abbreviation of NiFe2O4).

[0007] The application method is as follows: taking x as 10, that is, the ZIS photocatalyst loaded with 10% NFO is put into the wastewater as the photocatalyst, firstly ultrasonicated for 3 minutes to make the photocatalyst disperse evenly, then transferred to a photochemical reactor, magnetic stirring is turned on, and a dark reaction is carried out for 45 minutes. After the adsorption and desorption equilibrium between the photocatalyst and the xanthate is reached, the light source is turned on, and a photocatalytic reaction is carried out. The irradiated wastewater is purified by the photocatalytic reaction to degrade the xanthate in the wastewater.

[0008] The preparation method comprises the following steps:

[0009] Step 1: Preparation of NFO:

[0010] Fe(NO3)3·9H2O and Ni(NO3)2·6H2O with a molar ratio of 2:1 were dispersed in ultrapure water and stirred for 10 minutes; then the pH of the solution was adjusted to 13 with NaOH solution; after stirring for 1 hour, the above solution was transferred to a polytetrafluoroethylene high-pressure reactor and reacted at 180°C for 12 hours; after the reactor was naturally cooled to room temperature, it was centrifuged and washed with ultrapure water and anhydrous ethanol for 3 times each; finally, it was dried in an oven at 60°C for 12 hours to obtain NFO powder;

[0011] Step 2: Preparation of ZIS:

[0012] Disperse ZnCl2, InCl3·4H2O and thioacetamide in a molar ratio of 1:2:8 in ultrapure water, and ultrasonicate for 30 minutes to form a uniform solution; stir the solution continuously for 30 minutes and then transfer it to a polytetrafluoroethylene high-pressure reactor, and react at 160°C for 12 hours; after the reactor is naturally cooled to room temperature, wash it with ultrapure water and anhydrous ethanol three times by centrifugation; finally, dry it in an oven at 80°C for 12 hours to obtain a yellow ZIS catalyst;

[0013] Step 3: Compounding of NFO / ZIS materials:

[0014] ZIS was dispersed in methanol and ultrasonically treated for 15 min. Subsequently, NFO was added to the above solution and ultrasonically treated for 15 min, with the mass ratio of ZIS to NFO being 100:x. After that, the mixed solution was stirred in an oil bath at 35°C for 24 h, the solid was collected by centrifugation and dried in a vacuum oven at 60°C for 12 h to obtain the xNFO / ZIS catalyst.

[0015] The present invention uses Fe(NO3)3·9H2O and Ni(NO3)2·6H2O as raw materials to prepare NiFe2O4 (NFO), uses ZnCl2, InCl3·4H2O and thioacetamide (TAA) as raw materials to synthesize ZnIn2S4 (ZIS) by a hydrothermal method, and synthesizes the NFO / ZIS composite catalyst by a stirring method. The present invention loads NFO on ZIS to form a heterojunction, so that it has strong carrier mobility, excellent light absorption ability and porous microstructure; compared with pure phase NFO and ZIS, the performance of the composite material NFO / ZIS in photocatalytic treatment of xanthate is greatly improved. The composite catalyst is magnetic, easy to recover, and reduces the application cost. The composite method of this case is simple and feasible, and has great research value in the treatment of mineral processing wastewater and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The scanning electron microscope images of NFO, ZIS, and 10NFO / ZIS samples in the embodiment;

[0017] Figure 2 is the X-ray diffraction pattern of NFO, ZIS, 5NFO / ZIS, 10NFO / ZIS, 30NFO / ZIS, 50NFO / ZIS, samples in the embodiment;

[0018] Figure 3 The photocatalytic degradation effect diagram of xanthate solution of NFO, ZIS, 5NFO / ZIS, 10NFO / ZIS, 30NFO / ZIS, and 50NFO / ZIS samples in the implementation manner;

[0019] Figure 4 Graph showing the results of four cycles of xanthate degradation by 10NFO / ZIS in an embodiment. DETAILED DESCRIPTION

[0020] In order to clearly illustrate the technical features of this patent, this patent is elaborated in detail below through a specific implementation method and in combination with its accompanying drawings.

[0021] The preparation method of NFO / ZIS photocatalyst in this case includes the following steps:

[0022] Step 1: Preparation of NFO:

[0023] Disperse 0.02mmol Fe(NO3)3·9H2O and 0.01mmol Ni(NO3)2·6H2O in 50mL ultrapure water and stir for 10min; then adjust the pH of the solution to 13 with 4.5mol / L NaOH solution; after stirring for 1h, transfer the above solution to a 100mL polytetrafluoroethylene autoclave and react at 180℃ for 12h. After the autoclave is cooled to room temperature naturally, wash it with ultrapure water and anhydrous ethanol by centrifugation 3 times each; finally, dry it in an oven at 60℃ for 12h to obtain NFO powder;

[0024] Step 2: Preparation of ZIS:

[0025] 1.6mmol ZnCl2, 3.2mmol InCl3·4H2O and 12.8mmol thioacetamide (TAA) were dispersed in 50mL ultrapure water, and ultrasonicated for 30min to form a uniform solution. The above solution was continuously stirred for 30min and then transferred to a 100mL polytetrafluoroethylene autoclave and reacted at 160℃ for 12h. After the autoclave was cooled to room temperature naturally, it was washed three times by centrifugation with ultrapure water and anhydrous ethanol respectively; finally, the sample was placed in an oven and dried at 80℃ for 12h to obtain a yellow ZIS catalyst;

[0026] Step 3: Compounding of NFO / ZIS materials:

[0027] 0.1 g ZIS was weighed and dispersed in 50 mL methanol and ultrasonically treated for 15 min. Subsequently, 0.01 g NFO was added to the above solution and ultrasonicated for another 15 min; thereafter, the above mixed solution was stirred in an oil bath at 35 °C for 24 h. The solid was collected by centrifugation and dried in a vacuum oven at 60 °C for 12 h to obtain a 10NFO / ZIS catalyst.

[0028] After step 3 was modified to compound 0.005 g, 0.03 g and 0.05 g NFO with 0.1 g ZIS, the obtained products were named 5NFO / ZIS, 30NFO / ZIS and 50NFO / ZIS, respectively.

[0029] Figure 1 Field emission scanning electron microscopy (FE-SEM) images of NFO, ZIS and 10NFO / ZIS catalysts are shown. Figure 1 (ab) show that the NFO catalyst is composed of irregular nanoparticles with a particle size of about 100 nm agglomerated together. Figure 1 (cd) show that the ZIS catalyst is composed of nanosheets agglomerated into micron-flower-like spheres with a diameter of 1-4 mm. The morphology of the 10NFO / ZIS catalyst is similar to that of the ZIS catalyst. However, compared with pure ZIS, Figure 1(e) There are some irregular NFO nanoparticles on the surface of the 10NFO / ZIS catalyst micron flower-like spheres.

[0030] like Figure 2 As shown, all diffraction peaks in the XRD spectrum of NFO are consistent with the characteristic diffraction peaks of spinel cubic structure NFO (JCPDS No10-0325). The diffraction peaks of NFO catalyst at 2θ of 18.8°, 30.5°, 35.7°, 43.5°, 57.6° and 63.6° correspond to NFO (111), (220), (311), (400), (511) and (440) crystal planes, respectively. And no other impurity peaks appear in the XRD pattern of NFO, which indicates that NFO is successfully prepared. The diffraction peaks of the ZIS catalyst are consistent with the characteristic diffraction peaks of hexagonal ZIS (JCPDS No. 65-2023). The diffraction peaks at 2θ of 21.6°, 27.8° and 47.2° correspond to the (006), (102) and (110) crystal planes, respectively, and no other impurity peaks appear in the XRD pattern of ZIS, indicating that ZIS was successfully prepared. Compared with pure ZIS, the xNFO / ZIS catalyst has corresponding diffraction peaks of NFO at 2θ of 30.5°, 35.7°, 43.5°, 57.6° and 63.6°, and as x increases (i.e., the content of NFO increases), the diffraction peaks of NFO become increasingly obvious.

[0031] Embodiments of the application method:

[0032] The wastewater was simulated by using a xanthate solution with a concentration of 80 mg / L. A xenon lamp equipped with a 380 nm filter was used as the visible light source.

[0033] The specific steps are as follows:

[0034] Disperse 25 mg of photocatalyst into a quartz test tube containing 50 mL of xanthate solution, ultrasonicate for 3 minutes to make it dispersed evenly, and put the test tube into a photochemical reactor. Perform a dark reaction for 45 minutes under magnetic stirring to achieve adsorption and desorption equilibrium between the catalyst and the xanthate, then turn on the xenon lamp to perform a photocatalytic reaction. Take a sample of 2-3 mL from the quartz tube every 15 minutes, centrifuge at 4500 r / min for 3 minutes, take the supernatant, measure its absorbance at 301 nm, and calculate the degradation rate. The degradation efficiency of materials with different composite ratios is shown in Figure 2. Figure 3 As shown, the ZIS photocatalyst loaded with 10% NFO has the best photocatalytic performance.

[0035] The stability of the composite catalyst was studied through cyclic experiments.

[0036] The steps for catalyst recovery and regeneration are as follows:

[0037] After the test, the waste liquid containing the catalyst was centrifuged at 4500r / min for 3 minutes, the supernatant was poured out to separate the catalyst from the liquid, the collected catalyst was placed in ultrapure water for ultrasonic treatment for 15 minutes, and then centrifuged at 4500r / min for 3 minutes to collect, so that it was a complete cleaning, and the above steps were repeated until five water washings were completed; then the above steps were repeated with anhydrous ethanol instead of ultrapure water. After washing, the material was dried in a vacuum environment at 60℃ for 12 hours as the experimental material for the next cycle.

[0038] The results are as follows Figure 4 As shown in the figure, a complete experiment includes 45 minutes of dark reaction and 135 minutes of photocatalytic reaction. After four cycles, the degradation efficiency of 10NFO / ZIS on xanthate only decreased by 1.32%. This shows that the synthesized 10NFO / ZIS composite material has good stability and reusability.

[0039] There are many specific implementation ways of the present invention. The above is only the preferred implementation mode of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention. These improvements should also be regarded as the protection scope of the present invention.

Claims

1. A photocatalyst for degrading xanthate, It is characterized in that The photocatalyst is ZnIn with a mass ratio of 100:x 2 S 4 and NiFe 2 O 4 The composite is formed to form a ZIS photocatalyst loaded with x% NFO.

2. A method for using the photocatalyst for degrading xanthate according to claim 1, It is characterized in that Taking x as 10, that is, the ZIS photocatalyst loaded with 10% NFO is put into the wastewater as the photocatalyst, first ultrasonicated for 3 minutes to make the photocatalyst evenly dispersed, then transferred to the photochemical reactor, turned on the magnetic stirring, and carried out the dark reaction for 45 minutes. After the adsorption and desorption equilibrium between the photocatalyst and the xanthate is reached, the light source is turned on and the photocatalytic reaction is carried out. The irradiated wastewater is purified by the photocatalytic reaction to degrade the xanthate in the wastewater.

3. A method for preparing the photocatalyst for degrading xanthate according to claim 1, It is characterized in that The following steps are involved: Step 1: Preparation of NFO: The molar ratio of Fe(NO 3 ) 3 9H 2 O and Ni (NO 3 ) 2 6H 2 O was dispersed in ultrapure water and stirred for 10 minutes; then the pH of the solution was adjusted to 13 with NaOH solution; after stirring for 1 hour, the above solution was transferred to a polytetrafluoroethylene high-pressure reactor and reacted at 180°C for 12 hours; after the reactor was naturally cooled to room temperature, it was centrifuged and washed with ultrapure water and anhydrous ethanol for 3 times each; finally, it was dried in an oven at 60°C for 12 hours to obtain NFO powder; Step 2: Preparation of ZIS: The molar ratio of ZnCl was 1:2:

8. 2 、InCl 3 ·4H 2 O and thioacetamide were dispersed in ultrapure water, and ultrasonicated for 30 minutes to form a uniform solution; the above solution was continuously stirred for 30 minutes and then transferred to a polytetrafluoroethylene high-pressure reactor, and reacted at 160°C for 12 hours; after the reactor was naturally cooled to room temperature, it was centrifuged and washed three times with ultrapure water and anhydrous ethanol respectively; finally, it was placed in an oven and dried at 80°C for 12 hours to obtain a yellow ZIS catalyst; Step 3: Compounding of NFO / ZIS materials: ZIS was dispersed in methanol and ultrasonically treated for 15 min. Subsequently, NFO was added to the above solution and ultrasonically treated for 15 min, with the mass ratio of ZIS to NFO being 100:x. After that, the mixed solution was stirred in an oil bath at 35°C for 24 h, the solid was collected by centrifugation and dried in a vacuum oven at 60°C for 12 h to obtain the xNFO / ZIS catalyst.

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