Preparation method and application of Ce / black TiO2 / sepiolite composite photocatalyst

Abstract

The invention relates to a preparation method and application of a Ce / black TiO2 / sepiolite composite photocatalyst. According to the method, a one-step solvothermal method is adopted, Ti < 3 + > is introduced to the surface of white TiO2 in a self-doping mode to obtain black TiO2 with higher visible light response activity, meanwhile, Ce doping is performed on the black TiO2 in the reaction process, a carrier sepiolite mineral material is introduced, and therefore the novel Ce / black TiO2 / sepiolite composite photocatalyst different from the disclosed novel Ce / black TiO2 / sepiolite composite photocatalyst is prepared. The prepared composite photocatalyst is high in visible light utilization rate and good in degradation performance, and the effect of degrading residual xanthate in beneficiation wastewater is remarkable.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic photocatalytic materials, and particularly relates to a preparation method and application of a Ce / black TiO2 / sepiolite composite photocatalyst. Background Art

[0002] With the continuous acceleration of China's industrialization process, the demand for mineral resources is increasing. Mineral processing wastewater is an inevitable product in the process of mining production, and the harmless treatment of mineral processing wastewater has become a thorny problem restricting the green and high-quality development of the mining industry. The composition of mineral processing wastewater is complex, mainly including residual beneficiation agents, heavy metal ions and solid suspended matter, etc. Among them, xanthate is a collector widely used in the froth flotation of sulfide ores. If the flotation agents remaining in the mineral processing wastewater are discharged into natural water bodies without proper treatment, it will pose a great threat to human health and animal safety. The traditional methods for treating xanthate, such as adsorption, flocculation precipitation, natural exposure, chemical oxidation, biodegradation, etc., generally have problems such as low removal efficiency, risk of secondary pollution and high economic cost. Photocatalytic degradation is an environmentally friendly and low-cost wastewater treatment technology.

[0003] TiO2 has become one of the most systematically studied semiconductor materials in the field of environmental catalysis due to its excellent chemical stability, economy and good photocatalytic activity. However, problems such as serious aggregation of nanoscale TiO2 particles, difficult solid-liquid separation, and limited visible light response due to its wide bandgap (~3.2eV) have restricted the practical application of TiO2 photocatalysts. To improve the photocatalytic reaction activity of TiO2, domestic and foreign scholars have proposed various modification methods, including element doping, semiconductor compounding, and carrier loading. Chen et al. (Science, 2011, 331:746) introduced Ti 3+ and oxygen vacancies into the surface layer of nanoparticle TiO2 by hydrogenation to enhance its absorption of visible light. Compared with ordinary white TiO2, black TiO2 has a wider light absorption range (λ>700nm) and a narrower bandgap (~2.6eV), which is more conducive to the progress of photocatalytic reactions. However, to further improve the utilization efficiency of black TiO2 for visible light, it is often modified by element doping (rare earth, metal or non-metal elements), noble metal deposition, constructing semiconductor heterojunctions and introducing carriers, but these methods generally still have problems such as cumbersome preparation processes and high economic costs. Chinese Patent CN106925252A discloses a preparation method of a metal-doped nano-TiO2 / sepiolite composite material, which is used to degrade rhodamine B; this method uses the calcination crystallization method to dope metal elements cerium, bismuth and vanadium into nano-TiO2 and load it on the surface of sepiolite; however, there are problems such as high energy consumption in the preparation method and low visible light utilization rate of the photocatalyst. Summary of the Invention

[0004] In view of the problems of easy recombination of photo-generated carriers, low visible light utilization rate and poor adsorption performance of traditional TiO2 photocatalysts, the present invention provides a preparation method of a Ce / black TiO2 / sepiolite composite photocatalyst. This method adopts a one-step solvothermal method, and Ti is introduced onto the surface of white TiO2 by self-doping. 3+ Black TiO2 with higher visible light response activity is obtained. At the same time, Ce doping is carried out on black TiO2 during the reaction process, and the carrier sepiolite mineral material is introduced, thereby preparing a novel Ce / black TiO2 / sepiolite composite photocatalyst. The composite photocatalyst prepared by the present invention has high visible light utilization rate and good degradation performance, and has a remarkable effect when degrading the residual xanthate in the ore dressing wastewater.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A preparation method of a Ce / black TiO2 / sepiolite composite photocatalyst, which comprises the following steps:

[0007] (1) Mix sepiolite and deionized water and stir for 50 - 70 min to obtain a first suspension; then mix tetrabutyl titanate and isopropanol and stir for 5 - 15 min to obtain a first emulsion; after the stirring is completed, combine the first suspension and the first emulsion, and add manganese acetate tetrahydrate and cerium nitrate hexahydrate, and stir for 20 - 40 min to obtain a second emulsion.

[0008] Among them, 20 - 30 mL of deionized water is added to every 0.2 - 0.3 g of sepiolite, 20 - 30 mL of isopropanol, 0.06 - 0.18 g of manganese acetate tetrahydrate and 0.02 - 0.07 g of cerium nitrate hexahydrate are added to every 0.5 - 1.5 g of tetrabutyl titanate; the volume ratio of the first suspension to the first emulsion is 1:1 - 2;

[0009] (2) Transfer the second emulsion to a reaction kettle, seal it, and react at 180 - 220 °C for 6 - 10 h, and then naturally cool to room temperature;

[0010] (3) Vacuum filter the product obtained in the previous step, wash it with deionized water, then place the filter residue in a freeze dryer and dry it to constant weight, and grind it to obtain the Ce / black TiO2 / sepiolite composite photocatalyst;

[0011] The application of the Ce / black TiO2 / sepiolite composite photocatalyst prepared by the above method is used to degrade the residual xanthate in the ore dressing wastewater.

[0012] Add the Ce / black TiO2 / sepiolite composite photocatalyst to the xanthate solution, irradiate it under visible light for 60 - 180 min, and complete the degradation of the xanthate;

[0013] Among them, 20 - 40 mg of Ce / black TiO2 / sepiolite composite photocatalyst is added to every 50 mL of xanthate solution;

[0014] The initial concentration of the xanthate solution is 10 - 50 mg / L;

[0015] The visible light mentioned above is specifically the xenon lamp light source after filtering ultraviolet light, and the wavelength range is between 380 - 780 nm;

[0016] The illumination intensity of the xenon lamp is 300 - 500 mW / cm 2 , and the illumination distance is 100 - 500 mm.

[0017] For the preparation method of the above-mentioned Ce / black TiO2 / sepiolite composite photocatalyst, other raw materials, reagents, and equipment except sepiolite are obtained through well-known channels, and the operating process can be mastered by those skilled in the art.

[0018] The substantial features of the present invention are:

[0019] The Ce / black TiO2 / sepiolite composite photocatalyst is synthesized by a one-step solvothermal method. During the self-doping of Ti in TiO2 3+ to form black TiO2, Ce ions are doped into black TiO2, further reducing the band gap of black TiO2 and decreasing its grain size. At the same time, the introduction of the carrier sepiolite can not only effectively inhibit the aggregation of Ce / black TiO2, but also endow the ternary composite photocatalyst with more active adsorption sites and photocatalytic reaction sites, further improving the adsorption performance and visible light response ability of the composite photocatalyst, so that the prepared Ce / black TiO2 / sepiolite composite photocatalyst can achieve efficient and rapid degradation of xanthate under visible light conditions.

[0020] The beneficial effects of the present invention are: Compared with the prior art, the present invention has the following prominent substantial features and remarkable progress:

[0021] (1) Introducing sepiolite during the synthesis of black TiO2 can improve its dispersibility, making it have more photocatalytic reaction sites. At the same time, it can improve the adsorption performance of the composite catalyst for xanthate, making good use of the advantages of the porous and typical fibrous structure of sepiolite minerals.

[0022] (2) Using the solvothermal method to perform Ce doping while synthesizing black TiO2 further enhances the visible light response ability of black TiO2.

[0023] (3) The present invention uses a one-step solvothermal method to prepare the Ce / black TiO2 / sepiolite composite photocatalyst, and the preparation process is relatively simple and has a high tolerance for experimental parameters.

[0024] (4) The degradation rate of the composite photocatalyst of the present invention for 30 mg / L xanthate is 95.5%, which is significantly better than the degradation rate of the sample in the comparative example for xanthate under the same conditions.

[0025] (5) The pollutants that can be oxidized and degraded by using the composite photocatalyst disclosed in this application include, but are not limited to, xanthate in ore dressing wastewater, and it can be used to remove other organic pollutants in wastewater, providing a new material for the catalytic purification of residual organic pollutants in wastewater.

[0026] The present invention provides a preparation method and application of a Ce / black TiO2 / sepiolite composite photocatalyst. By using a one-step solvothermal method, while synthesizing Ce-doped black TiO2, Ce / black TiO2 is loaded onto sepiolite, and the visible light utilization rate of the prepared composite photocatalyst is significantly improved, and the adsorption performance is significantly improved. Description of the Drawings

[0027] Figure 1 XRD pattern of the Ce / black TiO2 / sepiolite composite photocatalyst prepared in Example 1.

[0028] Figure 2 SEM photos of the Ce / black TiO2 / sepiolite composite photocatalyst prepared in Example 1, where Figure 2 (a) Low-magnification SEM photo of the Ce / black TiO2 / sepiolite composite photocatalyst, Figure 2 (b) High-magnification SEM photo of the Ce / black TiO2 / sepiolite composite photocatalyst.

[0029] Figure 3 Fine spectra of Ce, Ti, O, and Si elements in the Ce / black TiO2 / sepiolite composite photocatalyst prepared in Example 1; where Figure 3 (a) Fine spectrum of Ce element, Figure 3 (b) Fine spectrum of Ti element; Figure 3 (c) Fine spectrum of O element, Figure 3 (d) Fine spectrum of Si element.

[0030] Figure 4 Degradation rate curves and degradation kinetic fitting lines of sepiolite, black TiO2, Ce / black TiO2 prepared in Comparative Examples 1-2, and Ce / black TiO2 / sepiolite prepared in Example 1 for xanthate; where Figure 4 (a) Degradation rate curve diagram of different samples for xanthate, Figure 4 (b) Degradation kinetic fitting line diagram of different samples for xanthate. Detailed Description of the Invention

[0031] The present invention will be described below with specific embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0032] Example 1

[0033] Take 0.25 g of sepiolite and place it in a beaker. Add 25 mL of deionized water and mix and stir for 60 min. Denote the obtained suspension as A1; take 0.85 g of tetrabutyl titanate and place it in a beaker. Add 25 mL of isopropanol and mix and stir for 10 min. Denote the obtained emulsion as B1; combine the suspension A1 and the emulsion B1, and simultaneously add 0.1226 g of manganese acetate tetrahydrate and 0.0434 g of cerium nitrate hexahydrate, and stir for 30 min to obtain an emulsion B2; transfer the emulsion B2 to a 100 mL closed reaction kettle for solvothermal reaction. The reaction temperature is 200 °C, and the reaction time is 8 h. After the heating is completed, slowly cool down to room temperature. Filter, wash, and freeze-dry the naturally cooled product to obtain a Ce / black TiO2 / sepiolite composite photocatalyst.

[0034] Modify black TiO2 by Ce doping to shorten the band gap. At the same time, use sepiolite to load Ce / black TiO2 to improve its dispersibility and further enhance the response ability of the composite catalyst to visible light.

[0035] Example 2

[0036] Other steps are the same as those in Example 1, except that "0.85 g of tetrabutyl titanate" is replaced with "0.64 g of tetrabutyl titanate", "0.1226 g of manganese acetate tetrahydrate" is replaced with "0.0920 g of manganese acetate tetrahydrate", and "0.0434 g of cerium nitrate hexahydrate" is replaced with "0.0326 g of cerium nitrate hexahydrate". The obtained composite photocatalyst still shows good degradation performance for xanthate.

[0037] Example 3

[0038] Other steps are the same as those in Example 1, except that "0.25 g of sepiolite" is replaced with "0.2 g of sepiolite", "0.1226 g of manganese acetate tetrahydrate" is replaced with "0.0613 g of manganese acetate tetrahydrate", and "0.0434 g of cerium nitrate hexahydrate" is replaced with "0.0651 g of cerium nitrate hexahydrate". The obtained composite photocatalyst still shows good degradation performance for xanthate.

[0039] Comparative Example 1

[0040] Take 0.85 g of tetrabutyl titanate and place it in a beaker. Add 25 mL of isopropanol and mix and stir for 10 min. Denote the obtained emulsion as A1; take 0.1226 g of manganese acetate tetrahydrate and dissolve it in 25 mL of deionized water and stir for 10 min. Denote the obtained solution as B1; combine the emulsion A1 and the solution B1, mix and stir for 30 min to obtain an emulsion A2. Transfer the emulsion A2 to a 100 mL sealed reactor for solvothermal reaction. The reaction temperature is 200 °C and the reaction time is 8 h. After the heating is completed, slowly cool down to room temperature. Filter, wash, and freeze-dry the naturally cooled product to obtain the catalyst black TiO2.

[0041] Comparative Example 2

[0042] Take 0.85 g of tetrabutyl titanate and place it in a beaker. Add 25 mL of isopropanol and mix and stir for 10 min. Denote the obtained emulsion as A1; take 0.1226 g of manganese acetate tetrahydrate and 0.0434 g of cerium nitrate hexahydrate and dissolve them in 25 mL of deionized water and stir for 10 min. Denote the obtained solution as B1; combine the emulsion A1 and the solution B1, mix and stir for 30 min to obtain an emulsion A2. Transfer the emulsion A2 to a 100 mL sealed reactor for solvothermal reaction. The reaction temperature is 200 °C and the reaction time is 8 h. After the heating is completed, slowly cool down to room temperature. Filter, wash, and freeze-dry the naturally cooled product to obtain the catalyst Ce / black TiO2.

[0043] From the appendix Figure 1 The characteristic diffraction peaks of sepiolite and black TiO2 can be seen. The reason for not observing the Ce-related diffraction peaks is that the Ce doping amount is relatively small, lower than the detection limit of XRD analysis. Combining with the XPS analysis results of the composite catalyst (as shown in the appendix Figure 3 (a)), Ce exists on the surface of the composite catalyst 3+ and Ce 4+ , indicating that the Ce element has been successfully incorporated. The combination of the two characterization analyses confirms the successful preparation of the Ce / black TiO2 / sepiolite composite photocatalyst.

[0044] From the appendix Figure 2 As can be seen from the low-magnification SEM image of the Ce / black TiO2 / sepiolite composite photocatalyst in appendix Figure 2 (a), the Ce / black TiO2 nanoparticles are uniformly distributed on the sepiolite fibers; as can be seen from the high-magnification SEM image of the Ce / black TiO2 / sepiolite composite photocatalyst in appendix Figure 2 (b), the size of the Ce / black TiO2 nanoparticles is about 10 nm. The fibrous structure of sepiolite can significantly improve the dispersion of the Ce / black TiO2 nanoparticles, which is beneficial to the improvement of the photocatalytic effect of Ce / black TiO2.

[0045] From the appendix Figure 3The chemical valence states and bonding situations of Ce, Ti, O, and Si elements in the Ce / black TiO2 / sepiolite composite photocatalyst can be seen, indicating that the components in the composite photocatalyst are tightly bound by chemical bonds. Among them, Figure 3 (a) The peaks located at 916.4, 912.7, 899.3, and 881.7 eV correspond to Ce 4+ , and the two peaks located at 903.9 and 885.5 eV correspond to Ce 3 + , indicating the successful incorporation of Ce element in black TiO2. Figure 3 (b) The peaks located at 458.0, 463.7, 456.8, and 459.9 eV correspond to Ti 4+ 2p 3 / 2 , Ti 4+ 2p 1 / 2 , Ti 3+ 2p 3 / 2 and Ti 3+ 2p 1 / 2 orbits, indicating the successful introduction of Ti 3+ in black TiO2. Figure 3 (c) The peaks located at 529.3 and 531.9 eV correspond to Ti-O and Si-O bonds respectively. Figure 3 (d) The peaks located at 100.6 and 102.8 eV correspond to Si-OH and Si-O-Si bonds respectively.

[0046] From attachment Figure 4 (a), it can be seen that the degradation rates of xanthate by the Ce / black TiO2 / sepiolite composite photocatalyst are all better than those of the materials prepared in Comparative Examples 1-2; Figure 4 (b) shows that the degradation processes of xanthate by all samples follow pseudo-first-order kinetics, and the Ce / black TiO2 / sepiolite composite photocatalyst exhibits the optimal degradation rate. The degradation rate of the black TiO2 prepared in Comparative Example 1 for xanthate with an initial concentration of 30 mg / L is 44.7%, and the degradation rate is 0.0025 min -1 , which may be due to the high surface energy of black TiO2 nanoparticles causing them to agglomerate with each other, reducing the photoreactive active sites and thus affecting its photocatalytic degradation rate; the degradation rate of the Ce / black TiO2 nanoparticles prepared in Comparative Example 2 for xanthate with an initial concentration of 30 mg / L is 80.9%, and the degradation rate is 0.0070 min -1 , which is significantly lower than the degradation rate of 95.5% and the degradation rate of 0.0197 min of the Ce / black TiO2 / sepiolite composite catalyst for xanthate under the same conditions -1Although the Ce doping improved the agglomeration of black TiO2 nanoparticles to a certain extent, the dispersibility of black TiO2 was still worse than that on sepiolite. In addition, although sepiolite had a certain adsorption capacity for xanthate, the effect of using sepiolite alone to remove xanthate was average, with a degradation rate of only 8.6%, and the degradation rate decreased to 0.0003 min -1 。

[0047] The photocatalytic degradation experiment of xanthate was carried out with the help of a PL-03 double-rotation motion aeration type photoreactor, and a UV1901PC type ultraviolet-visible spectrophotometer was used to measure the absorbance of xanthate at a wavelength of 301 nm. The Lambert-Beer law was used to calculate the degradation rate (D) of xanthate by the Ce / black TiO2 / sepiolite composite photocatalyst, and its calculation formula is as follows:

[0048]

[0049] In the formula, C0 and C represent the initial concentration of xanthate and the concentration after being adsorbed or degraded, respectively; A0 and A represent the initial absorbance of xanthate at the characteristic absorption wavelength of 301 nm and the corresponding absorbance after degradation, respectively. The degradation rate of xanthate can be expressed by the following pseudo-first-order kinetic model:

[0050] In(C0 / C)kt

[0051] In the formula, k is the reaction kinetic constant and t is the light irradiation time.

[0052] The specific test steps are as follows: First, a dark adsorption test in the dark was carried out. 30 mg of photocatalyst was added to 50 mL of xanthate solution with an initial concentration of 30 mg / L to start the dark adsorption test. The dosage of the photocatalyst was 30 mg, the initial concentration was 30 mg / L, and the dark adsorption time was set to 30 min. After the dark adsorption reaction reached equilibrium basically, the light source was turned on to start the photocatalytic degradation test. The light intensity of the xenon lamp was 400 mW / cm 2 2, and the light irradiation distance was 300 mm. The light irradiation time interval was set to 30 min, and the sampling time for a single group of samples was set to 3 min. After sampling, the samples were filtered with a 0.22 μm aqueous filter membrane, and the absorbance value of the filtrate at a wavelength of 301 nm was measured.

[0053] From the above examples and comparative examples, it can be seen that in the present invention, the TiO2 was self-doped with Ti 3+During the preparation of black TiO2, Ce doping is carried out simultaneously to refine the size of black TiO2 nanoparticles and shorten the band gap width, thereby improving its photocatalytic activity. At the same time, Ce / black TiO2 is loaded onto sepiolite to improve its dispersion and further enhance the visible light response ability of the composite catalyst. The preparation process of the present invention is simple, and the synthesized Ce / black TiO2 / sepiolite composite photocatalyst gives full play to the advantages of each component, enabling efficient degradation of xanthate under visible light conditions.

[0054] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

[0055] Matters not covered by the present invention are well-known technologies.

Claims

1. A preparation method of a Ce / black TiO2 / sepiolite composite photocatalyst, characterized in that, The method comprises the following steps: (1) Mix and stir sepiolite and deionized water for 50 - 70 min to obtain a first suspension; then mix and stir tetrabutyl titanate and isopropanol for 5 - 15 min to obtain a first emulsion; after the stirring is completed, combine the first suspension and the first emulsion, and add manganese acetate tetrahydrate and cerium nitrate hexahydrate, and stir for 20 - 40 min to obtain a second emulsion; Among them, 20 - 30 mL of deionized water is added to every 0.2 - 0.3 g of sepiolite, 20 - 30 mL of isopropanol, 0.06 - 0.18 g of manganese acetate tetrahydrate and 0.02 - 0.07 g of cerium nitrate hexahydrate are added to every 0.5 - 1.5 g of tetrabutyl titanate; the volume ratio of the first suspension to the first emulsion is 1:1 - 2; (2) Transfer the second emulsion to a reaction kettle, seal it, and react at 180 - 220 °C for 6 - 10 h, and then naturally cool to room temperature; (3) Vacuum filter the product obtained in the previous step, and after the filter residue is washed with deionized water, freeze-dried and ground, a Ce / black TiO2 / sepiolite composite photocatalyst is obtained.

2. Application of the Ce / black TiO2 / sepiolite composite photocatalyst prepared by the method according to claim 1, characterized in that, It is used for degrading the residual xanthate in the ore dressing wastewater.

3. The application according to claim 2, characterized in that, Add the Ce / black TiO2 / sepiolite composite photocatalyst to the xanthate solution, and then irradiate it under visible light for 60 - 180 min to complete the degradation of the xanthate; Among them, 20 - 40 mg of the Ce / black TiO2 / sepiolite composite photocatalyst is added to every 50 mL of the xanthate solution; The concentration of the xanthate solution is 10 - 50 mg / L.

4. The application according to claim 3, characterized in that, The visible light is specifically a xenon light source after filtering ultraviolet light, with a wavelength range between 380 and 780 nm; the light intensity is 300 to 500 mW / cm 2 , and the illumination distance is 100 to 500 mm.

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