Method for degrading bisphenol organic pollutants

Abstract

The invention discloses a method for degrading bisphenol organic pollutants. The method comprises a preparation method of ferromanganese spinel with a rare earth doped particle structure and an application of the ferromanganese spinel and peroxymonosulfate in degrading the bisphenol organic pollutants by cooperating with a hydrodynamic cavitation technology. Mainly relates to combination of a Fenton-like oxidation technology and a hydrodynamic cavitation technology for activating peroxymonosulfate by using ferromanganese spinel with a rare earth doped particle structure. Comprising the following steps: activating persulfate through transfer electrons between surface defects and rare earth elements of prepared ferromanganese spinel with a rare earth doped particle structure under a hydrodynamic cavitation condition, so as to generate a large number of superoxide free radicals to degrade bisphenol organic pollutants. A rich gas-liquid interface provided by nano bubbles generated by hydrodynamic cavitation is combined, and the contact opportunity of active oxygen species and pollutant molecules is increased, so that the reaction rate and the degradation efficiency are improved. According to the method, efficient degradation of bisphenol organic pollutants is realized, and a green and efficient solution is provided for water treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of advanced oxidation, and specifically provides a method for degrading bisphenol organic pollutants by using rare earth-doped ferromanganese spinel with a granular structure and peroxymonosulfate in coordination with hydrodynamic cavitation technology. Background Art

[0002] The widespread presence of endocrine disruptors such as bisphenol A (BPA) and other organic pollutants poses a serious threat to the ecological environment and human health, and the development of efficient water treatment technology is particularly important. As an effective water treatment method, advanced oxidation technology can degrade organic pollutants by producing strong oxidizing free radicals. Among them, permonosulfate (PMS) activation technology has attracted much attention because of its ability to produce a variety of reactive oxygen species (ROS). However, using PMS alone for oxidation treatment has problems such as low efficiency and high energy consumption.

[0003] As a composite metal oxide catalyst, manganese iron spinel (MnFe2O4) shows potential for application in PMS activation technology. Rare earth element doping, as an effective modification method, can improve the catalytic activity of manganese iron spinel by changing its crystal structure and electronic properties. The introduction of rare earth elements can increase the number of active sites of the catalyst, promote electron transfer, reduce the energy barrier of PMS activation, and thus improve the generation efficiency of ROS.

[0004] In addition, hydrodynamic cavitation (HC) technology can promote chemical reactions by creating a local high temperature and high pressure environment, and combined with PMS activation technology, it can further improve the degradation efficiency of organic pollutants. The microjets and shock waves generated during the hydrodynamic cavitation process can destroy the surface structure of the catalyst and form surface defects. These defects can promote the activation of PMS as active sites. At the same time, the nanobubbles generated by hydrodynamic cavitation can provide a rich gas-liquid interface, increase the contact opportunities between ROS and pollutant molecules, and thus improve the reaction rate and degradation efficiency. Summary of the invention

[0005] In order to improve the activation efficiency of peroxymonosulfate (PMS) and the degradation efficiency of bisphenol pollutants, the present invention adopts a sol-gel method to synthesize a rare earth-doped granular structure manganese iron spinel (Ce-MnFe2O4), and combines it with hydraulic cavitation technology to achieve efficient synergistic degradation.

[0006] The technical solution adopted by the present invention is:

[0007] A method for degrading bisphenol organic pollutants, wherein the degradation reaction is carried out in a hydrodynamic cavitation device, wherein rare earth-doped ferromanganese spinel with a granular structure is mixed with an aqueous solution containing bisphenol organic pollutants, and after reaching adsorption-desorption equilibrium, peroxymonosulfate is added, and the hydrodynamic cavitation device is started to carry out the degradation reaction. The synergistic effect of the hydrodynamic cavitation and the activation of peroxymonosulfate by the rare earth-doped ferromanganese spinel with a granular structure is used to achieve efficient degradation of bisphenol organic pollutants.

[0008] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the initial concentration of the aqueous solution containing bisphenol organic pollutants is 10-50 mg / L, preferably 20 mg / L.

[0009] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the addition amount of the rare earth-doped ferromanganese spinel with a particle structure is 0.05-0.3 g / L, preferably 0.15 g / L.

[0010] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the added amount of the peroxymonosulfate is 0.2-1.0 mM, preferably 0.6 mM.

[0011] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the pH value of the reaction system is 3-11, preferably 7.

[0012] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the adsorption-desorption equilibrium time is 30 minutes.

[0013] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the hydraulic cavitation device is composed of a centrifugal pump, a constant temperature water tank, a water valve, a pressure gauge and a venturi tube cavitator.

[0014] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the length of the Venturi tube cavitator is 100 mm, the tube diameter is 18.2 mm; the throat length is 2 mm, the diameter is 1.7 mm; the length of the contraction section is 20 mm, the contraction angle is 22°; the length of the diffusion section is 70 mm, and the expansion angle is 6°.

[0015] Furthermore, in the above-mentioned method for degrading bisphenol organic pollutants, the inlet pressure of the venturi tube cavitator is 1-4 bar, preferably 3 bar.

[0016] In any one of the above methods for degrading bisphenol organic pollutants, the method for preparing the rare earth-doped ferromanganese spinel with a granular structure comprises the following steps:

[0017] 1) dissolving cerium nitrate hexahydrate, manganese acetate tetrahydrate, ferric nitrate nonahydrate and citric acid as raw materials in deionized water, stirring at 80° C. to form a sol, and hydrolyzing and polycondensing the metal ions through a sol-gel reaction;

[0018] 2) drying the sol in an oven at 105° C. for 3-5 hours to remove the solvent and form a dry gel;

[0019] 3) The dry gel was heated to 520° C. at a heating rate of 2-5° C. / min and calcined at the temperature for 2 hours to obtain ferromanganese spinel with good crystallinity and particle structure.

[0020] Furthermore, in the method for preparing the above rare earth-doped ferromanganese spinel with a granular structure, in step 1), the molar ratio of cerium nitrate hexahydrate, manganese acetate tetrahydrate and ferric nitrate nonahydrate is manganese: iron: cerium = 1:2:0.03-0.07, preferably 1:2:0.05.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. Through the doping of rare earth element Ce, the Ce-MnFe2O4 catalyst of the present invention enhances the PMS activation ability, and can more effectively generate active oxygen species such as superoxide free radicals (·O2-) under the synergistic effect of hydrodynamic cavitation, thereby significantly improving the degradation efficiency of BPA. Compared with other advanced oxidation processes, the present invention significantly improves the degradation efficiency and the generation of active oxygen species, and can achieve a higher pollutant removal rate under the same conditions.

[0023] 2. As a new advanced oxidation process, hydrodynamic cavitation technology has lower energy consumption than other advanced oxidation processes. Combined with the Ce-MnFe2O4 catalyst of the present invention, the system can achieve efficient BPA degradation at lower energy input, thereby reducing operating costs. In addition, the stability and reusability of the Ce-MnFe2O4 catalyst further reduce long-term operating costs.

[0024] 3. The system of the present invention realizes a greener and more environmentally friendly water treatment process by reducing the consumption of chemical oxidants and lowering energy consumption. At the same time, due to the easy recovery and regeneration of Ce-MnFe2O4 catalyst, secondary pollution to the environment is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the X-ray diffraction (XRD) spectra of Ce-MnFe2O4 catalysts with different molar ratios.

[0026] Figure 2 This is the SEM image of Ce-MnFe2O4 ((a) 2μm, (b) 500nm).

[0027] Figure 3 It is a schematic diagram of a hydraulic cavitation degradation device (a) and a schematic diagram of the dimensions of a venturi tube cavitator (b), in which 1-centrifugal pump, 2-constant temperature water tank, 3-water valve, 4-pressure gauge, 5-venturi tube cavitator, 6-contraction section, 7-diffusion section, and 8-throat.

[0028] Figure 4 This is the optimal condition screening of the degradation method in the embodiment, where (a) is the Ce-MnFe2O4 catalyst dosage screening, (b) is the persulfate dosage screening, (c) is the environmental pH value screening, (d) is the Venturi tube cavitator inlet pressure screening, and (e) is the BPA concentration screening.

[0029] Figure 5 It is a removal curve diagram of the degradation reaction under different degradation conditions.

[0030] Figure 6 This is the removal curve of different bisphenol organic pollutants. DETAILED DESCRIPTION

[0031] The embodiments of the present invention are described in further detail below.

[0032] Example 1

[0033] This embodiment provides a method for degrading bisphenol organic pollutants by combining peroxymonosulfate Fenton oxidation technology with hydrodynamic cavitation technology, which comprises the following steps:

[0034] 1) Preparation of rare earth-doped granular structured manganese iron spinel (Ce-MnFe2O4): 0.217 g of cerium nitrate hexahydrate, 2.45 g of manganese acetate tetrahydrate and 8.08 g of ferric nitrate nonahydrate (molar ratio, manganese: iron: cerium = 1:2:0.05) were placed in a beaker and dissolved in an appropriate amount of deionized water. The resulting mixture was stirred until a uniform solution was formed, and then the temperature was raised to 80°C. Separately, 12.6 g of citric acid was placed in a beaker and dissolved in an appropriate amount of deionized water to prepare a uniform solution, and the solution was added to the aforementioned uniform solution. Thereafter, the suspension was stirred at a constant temperature of 80°C until a sol was formed. The obtained sol was then dried at 105°C until the water was completely evaporated to obtain a dry gel. The obtained dry gel was ground, and the ground sample was calcined at 520°C (heated to 520°C at a heating rate of 2-5°C / min) for 2 h to obtain a Ce-MnFe2O4 product (Ce 5%).

[0035] In addition, cerium nitrate hexahydrate was added to the mixed solution in four different molar ratios of 1:0.03 (0.130 g), 1:0.05 (0.217 g), 1:0.07 (0.304 g) and 1:0.1 (0.434 g) to obtain Ce-MnFe2O4 products (3%, 5%, 7%, 10%), respectively.

[0036] Figure 1 X-ray diffraction (XRD) spectra of Ce-MnFe2O4 catalysts with different molar ratios and standard cards of MnFe2O4 (JCPDS No.01-0319) and CeO2 (JCPDS No.43-1002). The threshold of Ce doping concentration was determined based on the results of XRD analysis. For the prepared Ce-MnFe2O4 nanocatalyst, the Ce / MnFe2O4 molar ratio should be controlled at <0.07, and the preferred ratio is 0.05 to successfully synthesize cerium-doped manganese iron spinel. Figure 2 This is the SEM image of Ce-MnFe2O4 ((a) 2μm, (b) 500nm). It can be clearly seen from the figure that its structure is a three-dimensional nanoparticle stacking structure, which can provide more active sites to promote the activation of PMS. At the same time, this structure has the ability to resist hydraulic cavitation impact and is suitable for application in a combined system.

[0037] 2) Screening of Ce-MnFe2O4 catalyst and persulfate dosage, environmental pH value and venturi tube cavitation inlet pressure. The degradation device uses a closed-loop system hydraulic cavitation device. Figure 3 It is a schematic diagram of the degradation device and a schematic diagram of the dimensions of the Venturi tube type cavitator. Figure 4It is the optimal condition screening result of the degradation method in the embodiment. According to the screening result, in a hydrodynamic cavitation device (composed of a centrifugal pump, a constant temperature water tank, a water valve, a pressure gauge and a venturi tube type cavitator), a Ce-MnFe2O4 catalyst is mixed with a BPA aqueous solution with an initial concentration of 20 mg / L at a concentration of 0.15 g / L, and stirred for 30 min to reach adsorption / desorption equilibrium. Subsequently, PMS (0.6 mM) is added to the mixture, and the hydrodynamic cavitation device is started to adjust the inlet pressure of the venturi tube type cavitator (the length of the venturi tube type cavitator is 100 mm, and the diameter is 18.2 mm; the throat length is 2 mm, and the diameter is 1.7 mm; the length of the contraction section is 20 mm, and the contraction angle is 22°; the length of the diffusion section is 70 mm, and the expansion angle is 6°) to 3 bar to start the degradation reaction. Before the test, the removal performance of PMS / Ce-MnFe2O4 / HC obtained in this example on BPA was measured by the following method: the peak area of ​​the BPA solution was measured by high performance liquid chromatography and converted into concentration using the BPA standard curve, the initial peak area of ​​the bisphenol pollutant solution was measured by high performance liquid chromatography and converted into concentration using the bisphenol pollutant standard curve, which was recorded as initial concentration C0 (20 mg / L). Subsequently, the degradation reaction was started, and after a certain time interval, the peak area of ​​the BPA solution was measured again and converted into concentration, which was recorded as C, and the degradation rate = (C0-C) / C0×100%. Figure 4 It is a removal curve of the degradation reaction under different degradation conditions. When the BPA concentration is 20mg / L, the PMS dosage is 0.6mM, the Ce-MnFe2O4 dosage is 0.15g / L, the temperature is 25±5℃, and the pH value is 7, the synergistic removal efficiency of BPA by the PMS / Ce-MnFe2O4 / HC system can reach 99%. Figure 5 It is a removal curve diagram of the degradation reaction under different degradation conditions. The results show that the PMS / Ce-MnFe2O4 / HC system has a good degradation effect on BPA compared with the single Fenton-like system and the hydrodynamic cavitation system.

[0038] 3) In order to verify the degradation effect of PMS / Ce-MnFe2O4 / HC system on bisphenol pollutants, a series of experiments were designed in this embodiment. The specific steps are as follows: Ce-MnFe2O4 catalyst is added to an aqueous solution containing 20 mg / L bisphenol organic pollutants, stirred for 30 min to reach adsorption / desorption equilibrium, and the Ce-MnFe2O4 dosage is maintained at 0.15 g / L, and the temperature is 25±5°C. The selected bisphenol substances are bisphenol A (BPA), bisphenol B (BPB), bisphenol F (BPF), bisphenol AF (BPAF) and bisphenol S (BPS). After reaching adsorption / desorption equilibrium, PMS (0.6 mM) is then added to the mixture, and the water cavitation device is started to adjust the inlet pressure to 3 bar to start the degradation reaction. The initial peak area of ​​the bisphenol pollutant solution is measured using a high performance liquid chromatograph, and converted into a concentration through a bisphenol pollutant standard curve, recorded as the initial concentration C0. Subsequently, the degradation reaction was started, and after a certain time interval, the peak area of ​​the BPA solution was measured again and converted into concentration, recorded as C, and the degradation rate = (C0-C0) / C0×100% to evaluate the degradation effect. Figure 6 It is a removal curve of different bisphenol organic pollutants. The results show that the degradation efficiency of bisphenol pollutants by the PMS / Ce-MnFe2O4 / HC system is maintained above 98%, which fully demonstrates the excellent degradation performance of the PMS / Ce-MnFe2O4 / HC system on bisphenol pollutants.

[0039] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A method for degrading bisphenol organic pollutants, characterized in that: The degradation reaction is carried out in a hydrodynamic cavitation device. Manganese iron spinel with a granular structure doped with rare earth is mixed with an aqueous solution containing bisphenol organic pollutants. After reaching adsorption and desorption equilibrium, peroxymonosulfate is added and the hydrodynamic cavitation device is started to carry out the degradation reaction.

2. The method for degrading bisphenol organic pollutants according to claim 1, characterized in that: The initial concentration of the aqueous solution containing bisphenol organic pollutants is 10-50 mg / L, the added amount of rare earth-doped granular structured manganese iron spinel is 0.05-0.3 g / L, and the added amount of permonosulfate is 0.2-1.0 mM.

3. The method for degrading bisphenol organic pollutants according to claim 2, characterized in that: The initial concentration of the aqueous solution containing bisphenol organic pollutants is 20 mg / L, the added amount of rare earth-doped ferromanganese spinel with a particle structure is 0.15 g / L, and the added amount of peroxymonosulfate is 0.6 mM.

4. The method for degrading bisphenol organic pollutants according to claim 1, characterized in that: The pH value of the reaction system is 3-11.

5. The method for degrading bisphenol organic pollutants according to claim 4, characterized in that: The pH value of the reaction system was 7.

6. The method for degrading bisphenol organic pollutants according to claim 1, characterized in that: The adsorption-desorption equilibrium time is 30 min.

7. The method for degrading bisphenol organic pollutants according to claim 1, characterized in that: The hydraulic cavitation device consists of a centrifugal pump, a constant temperature water tank, a water valve, a pressure gauge and a venturi tube cavitator; the venturi tube cavitator has a length of 100 mm and a tube diameter of 18.2 mm; a throat length of 2 mm and a diameter of 1.7 mm; a contraction section length of 20 mm and a contraction angle of 22°; a diffusion section length of 70 mm and an expansion angle of 6°.

8. The method for degrading bisphenol organic pollutants according to claim 7, characterized in that: The inlet pressure of the venturi tube cavitator is 1-4 bar.

9. The method for degrading bisphenol organic pollutants according to claim 8, characterized in that: The inlet pressure of the Venturi tube cavitator is 3 bar.

10. A method for degrading bisphenol organic pollutants according to any one of claims 1 to 9, characterized in that: The method for preparing the rare earth-doped ferromanganese spinel with a granular structure comprises the following steps: 1) dissolving cerium nitrate hexahydrate, manganese acetate tetrahydrate, ferric nitrate nonahydrate and citric acid as raw materials in deionized water, stirring at 80° C. to form a sol, wherein the molar ratio of cerium nitrate hexahydrate, manganese acetate tetrahydrate and ferric nitrate nonahydrate is manganese: iron: cerium = 1:2:0.03-0.07; 2) drying the sol in an oven at 105° C. for 3-5 hours to form a xerogel; 3) The dry gel was heated to 520° C. at a heating rate of 2-5° C. / min and calcined at the temperature for 2 hours to obtain ferromanganese spinel with good crystallinity and particle structure.

Images