Background
With the development of global economy, the energy consumption is rapidly increasedThe contradiction between the mouth and resources is more and more sharp, and the environmental protection problem becomes one of the important restriction factors for the development of economy and society. In recent years, photocatalysts have attracted wide attention in the field of water pollution treatment research, wherein bismuth-based photocatalysts including bismuth oxide, bismuthate and bismuth oxyhalide become hot spots for research in the field of photocatalytic materials due to the characteristics of unique layered structure, good light absorption, safety, no toxicity and the like, but bismuth oxyhalide has the defects of low visible light utilization rate, fast hole and electron recombination, too regular conduction band position and the like, so that the application of the bismuth oxyhalide in the fields of environment, energy and the like is limited. Bismuth-rich Bi as a novel bismuth-based catalyst24O31Br10The width of the conduction band is moderate, the increase of the content of Bi in the compound can effectively improve the position of the conduction band, is beneficial to generating more superoxide radicals, inhibits the recombination of photo-generated electrons and holes, and can improve the photocatalytic activity of the compound. Considering that in the process of photocatalytic degradation of organic wastewater, particularly large-scale treatment of wastewater, there is a problem that catalyst recovery is difficult. In order to prevent the secondary pollution caused by incomplete recovery of the photocatalyst and reduce the use cost, the photocatalyst is magnetized, and the separation, recovery and reuse are convenient.
Strontium ferrite SrFe12O19Not only has good magnetic performance, but also produces synergistic effect on photocatalysis; the bismuth is compounded on the magnetic strontium ferrite, so that the photocatalytic activity is improved, the recovery of the catalyst is facilitated, and the secondary pollution can be avoided. At present, few research reports on the composition of bismuth and magnetic substances are reported. Other magnetic photocatalysts, such as that disclosed in Chinese patent CN103480384A for preparing SrFe12O19/BiVO4The method has the following defects: (1) the prepared composite catalyst has low degradation efficiency of photocatalytic degradation of methylene blue, and the degradation rate is only 93% within 5 h; (2) the prepared composite catalyst has poor circulation stability, and when the composite catalyst is continuously used for 5 times, the degradation rate of methylene blue within 5 hours is only 60%. Researchers have conducted research on the photocatalytic activity of composite bismuth compounds, such as that disclosed in Chinese patent CN104722317A12O17Br2-Bi24O31Br10The method has the following defects: (1) firstly, bismuth oxybromide-bismuth oxalate is synthesized by a hydrothermal method, and then Bi is generated by calcination12O17Br2-Bi24O31Br10The composite photocatalyst is synthesized by a hydrothermal-roasting two-step method, the process is time-consuming, and the energy consumption is high; (2) no method for recovering and recovering the catalyst is given; (3) the degradation performance to dye wastewater is not high, and the synthesized composite catalyst is not completely degraded after 2 hours when the synthesized composite catalyst catalyzes and degrades 10mg/L rhodamine B solution.
Disclosure of Invention
The invention aims to provide SrFe aiming at the defects of low visible light catalytic activity and difficult catalyst recovery of a bismuth photocatalyst12O19Loading of non-stoichiometric bismuth-based compounds Bi as magnetic substrates24O31Br10Preparation of magnetic composite bismuth-rich Bi24O31Br10-SrFe12O19The method has the advantages of simple preparation method, less time consumption, low cost, convenient separation and recovery of the catalyst through the external magnetic field, and high catalytic activity and stability of the recovered catalyst. The prepared magnetic composite bismuth-rich visible light catalyst has good application prospect in the water pollution control technology for degrading organic pollutants containing heteroaromatic dyes and the like. The method not only realizes the full utilization of resources, but also avoids the secondary pollution possibly brought by the catalyst.
The invention relates to a magnetic composite multi-bismuth visible-light-driven photocatalyst Bi24O31Br10-SrFe12O19The preparation method comprises the following steps:
(1) magnetic SrFe12O19Preparation of
SrCl dissolved and quantified by deionized water2·6H2O and FeCl3·6H2And O, dripping NaOH solution into the mixed solution, placing the mixed solution into a reaction kettle, preserving heat for 24 hours in water bath at the temperature of 200 ℃, cooling, filtering, washing a filter cake, placing the filter cake into an oven at the temperature of 80 ℃, and drying for 12 hours to obtain the magnetic SrFe12O19。
(2)Bi24O31Br10-SrFe12O19Preparation of
Weighing proper amount of Bi (NO) according to the molar ratio of 1:13)3·5H2Dissolving O and NaBr in deionized water respectively to obtain Bi (NO)3)3Solutions and NaBr solutions; adding a proper amount of polyvinylpyrrolidone (PVP) into a NaBr solution, dissolving under the action of ultrasound to obtain a mixed solution A, and dropwise adding the mixed solution A into Bi (NO)3)3Stirring the solution for 0.5h to obtain a mixed solution B; weighing the SrFe prepared in the step (1) according to the mass ratio of 100: 5-2012O19Adding the mixed solution B into a mixed solution B, adjusting the pH of the solution to 9-11 by using a sodium hydroxide solution, and performing ultrasonic treatment for 1 hour to obtain a suspension C; placing the suspension C in a reaction kettle, preserving heat for 10-12 h in 120-160 ℃ water bath, cooling, filtering, washing a filter cake, placing in an oven at 80 ℃, and drying for 12h to obtain the magnetic composite bismuth-Bi24O31Br10-SrFe12O19。
By adopting the technical scheme, the invention mainly has the following effects:
(1) the magnetic composite multi-bismuth visible-light-driven photocatalyst Bi prepared by the method24O31Br10-SrFe12O19X-ray diffraction spectrum has no impurity peak and only Bi24O31Br10And SrFe12O19Characteristic diffraction peaks of (a); the preparation method is simple, short in time consumption, few in used equipment and low in production cost.
(2) The magnetic composite multi-bismuth visible-light-driven photocatalyst Bi prepared by the method24O31Br10-SrFe12O19The catalytic activity is high, 0.05g of the prepared composite visible-light-driven photocatalyst is used for catalyzing light to degrade 100mL of rhodamine B solution (the concentration of which is twice that of rhodamine B in Chinese patent CN 104722317A) with the concentration of 20mg/L under the irradiation of a sunlight-simulated xenon lamp, and the degradation is completed within 40min (the degradation effect is obviously higher than that in Chinese patent CN103480384A and Chinese patent CN 104722317A); under the same conditions, Bi alone24O31Br10The visible light degradation rate of the catalytic rhodamine B is only 65%.
(3) Magnet prepared by the method of the inventionSexual composite multi-bismuth visible light catalyst Bi24O31Br10-SrFe12O19The recovery rate is up to 87% under the action of an external magnetic field, the catalyst after 5 times of recovery catalyzes the photodegradation of rhodamine B under the same condition, and the degradation rate of rhodamine B solution with the concentration of 20mg/L still reaches 90% in 0.5 h.
Detailed Description
The present invention will be further described with reference to the following specific embodiments.
Example 1
Magnetic composite multi-bismuth visible-light-driven photocatalyst Bi24O31Br10-SrFe12O19The preparation method comprises the following specific steps:
(1) magnetic SrFe12O19Preparation of
Dissolving quantitative SrCl in deionized water2·6H2O and FeCl3·6H2And O, slowly dripping NaOH solution into the mixed solution, placing the mixed solution into a reaction kettle, preserving heat for 24 hours in water bath at the temperature of 200 ℃, cooling, filtering, washing a filter cake, placing the filter cake into an oven at the temperature of 80 ℃, and drying for 12 hours to obtain the magnetic SrFe12O19。
(2)Bi24O31Br10-SrFe12O19Preparation of
Weighing 1.94g Bi (NO)3)3·5H2O and 0.204g NaBr were dissolved in 20ml of deionized water to obtain Bi (NO)3)3Solutions and NaBr solutions; adding 0.2g of polyvinylpyrrolidone PVP into NaBr solution, dissolving under the action of ultrasound to obtain mixed solution A, and dropwise adding Bi (NO) into the mixed solution A3)3Stirring the solution for 0.5h to obtain a mixed solution B; 0.1052g of SrFe prepared in step (1) are weighed12O19Adding the mixed solution B into the mixed solution B, adjusting the pH of the solution to 9 by using a sodium hydroxide solution, and performing ultrasonic treatment for 1 hour to obtain a suspension C; placing the suspension C in a reaction kettle, keeping the temperature in a water bath at 120 ℃ for 10h, cooling, filtering, washing a filter cake, placing the filter cake in an oven at 80 ℃, and drying for 12h to obtain the magnetic composite bismuth-Bi24O31Br10-SrFe12O19。
Example 2
Magnetic composite multi-bismuth visible-light-driven photocatalyst Bi24O31Br10-SrFe12O19The preparation method comprises the following specific steps:
(1) magnetic SrFe12O19Preparation of
Same as in step (1) of example 1.
(2)Bi24O31Br10-SrFe12O19Preparation of
Weighing 1.94g Bi (NO)3)3·5H2O and 0.204g NaBr were dissolved in 20ml of deionized water to obtain Bi (NO)3)3Solutions and NaBr solutions; adding 0.2g of polyvinylpyrrolidone PVP into NaBr solution, dissolving under the action of ultrasound to obtain mixed solution A, and dropwise adding Bi (NO) into the mixed solution A3)3Stirring the solution for 0.5h to obtain a mixed solution B; weighing 0.0526g of SrFe prepared in step (1)12O19Adding the mixed solution B into the mixed solution B, adjusting the pH of the solution to 10 by using a sodium hydroxide solution, and performing ultrasonic treatment for 1 hour to obtain a suspension C; placing the suspension C in a reaction kettle, preserving heat for 11h in 140 ℃ water bath, cooling, filtering, washing a filter cake, placing in an oven at 80 ℃, and drying for 12h to obtain the magnetic composite bismuth-Bi24O31Br10-SrFe12O19。
Example 3
Magnetic composite multi-bismuth visible-light-driven photocatalyst Bi24O31Br10-SrFe12O19The preparation method comprises the following specific steps:
(1) magnetic SrFe12O19Preparation of
Same as in step (1) of example 1.
(2)MoS2/SrFe12O19Preparation of
Weighing 1.94g Bi (NO)3)3·5H2O and 0.204g NaBr were dissolved in 20ml of deionized water to obtain Bi (NO)3)3Solutions and NaBr solutions; adding 0.2g of polyvinylpyrrolidone PVP into NaBr solution, dissolving under the action of ultrasound to obtain mixed solution A, and dropwise adding Bi (NO) into the mixed solution A3)3Stirring the solution for 0.5h to obtain a mixed solution B; weighing 0.0263g of SrFe prepared in step (1)12O19Adding the mixed solution B into the mixed solution B, adjusting the pH of the solution to 11 by using a sodium hydroxide solution, and performing ultrasonic treatment for 1 hour to obtain a suspension C; placing the suspension C in a reaction kettle, keeping the temperature in a water bath at 160 ℃ for 12h, cooling, filtering, washing a filter cake, placing the filter cake in an oven at 80 ℃, and drying for 12h to obtain the magnetic composite bismuth-Bi24O31Br10-SrFe12O19。
Results of the experiment
Bi prepared in example 224O31Br10-SrFe12O19The catalytic degradation activity is optimal. For convenience of comparison, Bi was prepared24O31Br10And (3) sampling. Bi24O31Br10The preparation method is that in the step (2) of the embodiment 2, SrFe is not added12O19。
Bi prepared in example 224O31Br10-SrFe12O19And Bi24O31Br10And SrFe12O19Is shown in FIG. 1, and is represented by the following formula (XRD)24O31Br10Diffraction of the sampleThe peak corresponds exactly to the standard bismuth-rich card PDF #75-0888, indicating that the sample is homogeneous Bi24O31Br10;SrFe12O19Diffraction peaks completely correspond to standard card PDF #33-1340 of hexagonal strontium ferrite, and the sample is pure SrFe12O19. Composite magnetic bismuth-rich Bi24O31Br10-SrFe12O19The diffraction peaks of the X-ray diffraction spectrum of the Bi-based optical fiber are matched with the characteristic crystal face spectral lines (008), (107), (114) and (21-3), (10-10) and (11-7) of the standard cards PDF #33-1340 and PDF #75-0888, no impurity peak is generated, and the Bi-based optical fiber is proved to have the Bi-based optical fiber24O31Br10And SrFe12O19And (4) successfully compounding.
Bi prepared in example 224O31Br10-SrFe12O19The FT-IR spectrum of (2) at 3431cm-1,2921.8cm-1Obvious wave peaks appear and are respectively O-H and-CH2Stretching vibration, 530cm-1Is at Bi-O bond stretching vibration peak, 444cm-1, 544.4cm-1,592.5cm-1The absorption peak is the stretching vibration characteristic peak of Fe-O and Sr-O bonds of the M-type strontium ferrite; the C ═ O peak position of the characteristic peak of PVP is 1666cm-1Moving to 1654cm in low wavenumber direction-1At least one of (1) and (b); the peak positions of the other characteristic peaks C-N and C ═ C are not shifted. From the above-mentioned results, it was found that the interaction between Bi-O in the composite magnetic catalyst and C ═ O bond in PVP occurred, and thus Bi was synthesized24O31Br10-SrFe12O19In the process of (1), PVP and Bi24O31Br10-SrFe12O19Forming a chemical bond therebetween. 1654cm-1Is C ═ O stretching vibration peak, 1291cm-1Is C-N absorption peak, 1384cm-1The left and right absorption peaks are the C-N structure stretching vibration peaks of the amide structure and are the characteristic peaks of PVP. The reference shows that the synthesized composite contains Bi24O31Br10And SrFe12O19The characteristic absorption peak of the sample proves that the sample is magnetic composite bismuth-rich Bi24O31Br10-SrFe12O19。
Bi prepared in example 224O31Br10-SrFe12O19SEM of (5) is shown in FIG. 3, which shows monoclinic Bi24O31Br10Flake stacked flower shape and SrFe12O19Further proves the morphology of the hexagonal crystal of SrFe12O19And Bi24O31Br10The effective composition of (1).
Bi prepared in example 224O31Br10-SrFe12O19The magnetic composite multi-bismuth visible-light-driven photocatalyst is used for catalyzing and degrading 100mL of rhodamine B solution with the concentration of 20mg/L, and can be completely degraded within 40min under the irradiation of simulated sunlight, while single Bi24O31Br10In parallel tests, the degradation rate of RhB is 65%, and single SrFe12O19The corresponding degradation rate was 10%. The result shows that the magnetic composite bismuth-rich visible light catalyst synthesized by the invention has excellent visible light photocatalytic activity, and the magnetic matrix SrFe12O19The photocatalysis of the bismuth is synergistically promoted by further preventing the recombination of photogenerated electrons and holes. This is because the addition of PVP promotes Bi24O31Br10The growth of the crystal face with the active dominance weakens the growth of the inert crystal face, and effectively regulates and controls the growth direction of the crystal face, thereby inducing the generation of anisotropic structure and appearance, and also realizing the magnetic composite multi-bismuth Bi24O31Br10-SrFe12O19Can be controlled and synthesized.
Bi prepared in example 224O31Br10-SrFe12O19VSM of the magnetic composite bismuth-rich catalyst is shown in FIG. 4, Bi24O31Br10-SrFe12O19The saturation magnetization (Ms) and the residual magnetization (Mr) are 3.078emu/G and 1.026emu/G respectively, the coercivity (Hc) is 753.5G, and the higher coercivity shows good demagnetization resistance, which indicates that the composite magnetic bismuth-rich catalyst is a hard magnetic material, has good magnetic performance and is beneficial to separation and recovery under the action of an external magnetic field. By usingThe catalyst is recovered by an external magnetic field, and the average recovery rate is 87%; the catalyst recovered in the 5 th time catalyzes the photodegradation of rhodamine B under the same condition, and the degradation rate of the rhodamine B solution with the concentration of 20mg/L still reaches 90 percent within 0.5 h.
The above examples describe the preparation process, the main features and the advantages of the present invention. The present invention is not limited to the above-described embodiments, and the present invention can be continuously modified without departing from the scope of the principle and method of the present invention, which falls within the protection scope of the present invention.