Process for enhancing photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst

Abstract

The present invention relates to a process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst, which comprises the following steps: the first step is the collection and detection of industrial wastewater containing perfluorooctanoic acid; the second step is the pH adjustment of the industrial wastewater; and the third step is the process for photocatalytically degrading perfluorooctanoic acid. By effectively inhibiting the aggregation of the nanocatalyst during the reaction, the present invention can achieve the effective degradation of perfluorooctanoic acid (the degradation rate is 73.2-99.9%) and the recycling and reuse of the nanocatalyst.

Description

Technical Field

[0001] The technical solution of the present invention can be applied to the field of wastewater treatment. Specifically, it is a process of constructing a photocatalytic reaction system by using foam-supported nano-catalysts to achieve efficient degradation of perfluorooctanoic acid through the flow of liquid in the internal channels of the foam. Background Art

[0002] Perfluorooctanoic acid is a fluorinated organic strong acid. Due to its high surface activity, high heat stability, high chemical stability and other advantages, it is widely used in industrial fields such as petroleum, chemical industry, textile, and medicine. Approximately 20% of perfluorooctanoic acid remains in the industrial wastewater during use, posing a serious threat to the ecological environment and human safety. The carbon-fluorine bond in perfluorooctanoic acid has strong polarity and is one of the covalent bonds with the largest bond energy in nature (about 450 kJ / mol). Therefore, perfluorooctanoic acid is not easily degraded in water and exhibits bioaccumulation. When industrial wastewater containing perfluorooctanoic acid is discharged into natural water bodies, it will reduce the dissolved oxygen content and interfere with the growth and metabolism of aquatic organisms. In addition, research shows that after perfluorooctanoic acid enters the human body, it will inhibit cytokine expression and interfere with antigen presentation ability, causing damage to macrophages, leading to multi-organ lesions and inducing cancer. Therefore, it is particularly important and urgent to develop a suitable method to effectively remove residual perfluorooctanoic acid in industrial wastewater.

[0003] Currently, the treatment methods for industrial wastewater containing perfluorooctanoic acid mainly include adsorption method, coagulation method, bioelectrochemical method and photocatalytic oxidation method. Representative patents are: the invention patent CN202010094174.4 "Method for removing perfluorooctanoic acid in water by using lignin-based carbon nanotubes" applied by Li Dengxin; the invention patent CN202110654819.X "Treatment method for wastewater containing low-concentration perfluorooctanoic acid" applied by Wang Haijun et al.; the invention patent CN202110765314.0 "Method for degrading perfluorooctanoic acid by coupling microbial electro-Fenton with sodium persulfate" applied by Wang Wen et al.; the invention patent CN201510418253.5 "Method for photocatalytic degradation of perfluorooctanoic acid in water by doping noble metals into gallium oxide" applied by Yu Zebin et al. During the treatment of industrial wastewater containing perfluorooctanoic acid by the adsorption method, saturation is likely to occur, and a large amount of organic solvents are required for the activation and regeneration of the adsorbent. Using flocculants to remove perfluorooctanoic acid from industrial wastewater not only increases the operating cost, but also the residual flocculants are extremely likely to cause secondary pollution. The treatment of industrial wastewater containing perfluorooctanoic acid by the bioelectrochemical method is limited by the composition and concentration of the wastewater, and there are problems such as long hydraulic retention time, high energy consumption, and low current efficiency. Usually, it needs to be combined with other water treatment methods. Photocatalytic oxidation is an advanced oxidation technology. Using semiconductors as catalysts, organic pollutants can be completely mineralized into CO 2 and H 2Simple inorganic substances such as O have the advantages of simple process, mild reaction conditions, and no secondary pollution. Therefore, the treatment of industrial wastewater containing perfluorooctanoic acid by photocatalytic oxidation method has good prospects for large-scale application.

[0004] The secondary recombination of photo-generated carriers (electrons and holes) in traditional photocatalysts will significantly reduce the pollutant degradation efficiency, which is the key problem restricting the improvement of photocatalytic activity. Research shows that the smaller the particle size of semiconductor particles, the smaller the recombination probability of photo-generated carriers, and the better the charge separation effect, resulting in the improvement of catalytic activity. Therefore, the development of new nanocatalysts has become a research hotspot in the field of photochemistry. The invention patent CN201610101712.1 "Preparation method of a molybdenum oxide / titanium dioxide composite nanophotocatalyst" applied by Zhang Yong et al.; the invention patent CN201910274885.7 "Molybdenum diselenide modified titanium dioxide nanophotocatalyst and its preparation method and application" applied by Zhang Feixia and Tang Guogang; the invention patent CN201810330331.X "Preparation method of a tungsten bismuth oxide nanophotocatalyst" applied by Zhou Hongyang et al. However, the nanoparticles of nanocatalysts agglomerate seriously during the process of degrading pollutants, causing problems such as reduced activity, difficult recovery, and cost waste. Some studies have loaded nanocatalysts on the surface of solid carriers, but the reduction of the catalytic specific surface area will cause problems such as slow reaction rate, insufficient photon quantum efficiency, and mass transfer limitation. Therefore, the development of a new method for immobilizing nanocatalysts, which is convenient for catalyst recovery while maintaining a relatively fast reaction rate, is of great significance for accelerating the industrial application of photocatalytic oxidation technology.

[0005] In order to both enhance the surface contact between perfluorooctanoic acid and the nanocatalyst and improve the utilization rate of solar energy, this patent invented a process for enhancing the photocatalytic degradation of perfluorooctanoic acid by loading the nanocatalyst on foam. Through this process, the added nanocatalyst has the highest possible dispersion degree in the reaction system, which is beneficial to overcoming the problem of particle agglomeration during the process of degrading pollutants.

[0006] At present, the process for enhancing the photocatalytic degradation of perfluorooctanoic acid by loading the nanocatalyst on foam invented in this patent has a good operation effect, that is, it can well reduce the chemical oxygen demand value of industrial wastewater, and this method has not been reported in the literature. Summary of the Invention

[0007] The technical problem to be solved by this invention is: to propose a method for constructing a photocatalytic reaction system by loading a nanocatalyst on foam, which has a good treatment effect on industrial wastewater containing perfluorooctanoic acid, that is, it can greatly reduce the chemical oxygen demand value of industrial wastewater. This invention overcomes the defects of photocatalytic oxidation technology such as catalytic performance attenuation, difficult recovery, and inability to operate continuously caused by catalyst particle agglomeration.

[0008] The present invention provides a process for enhancing the photocatalytic degradation of perfluorooctanoic acid with a foam-supported nanocatalyst, comprising the following steps:

[0009] In the first step, industrial wastewater containing perfluorooctanoic acid is collected, its pH value is measured, and the concentration of perfluorooctanoic acid therein is detected.

[0010] In the second step, pH adjustment of the industrial wastewater: The pH value of the industrial wastewater containing perfluorooctanoic acid described in the first step is adjusted to 4.5 - 6.8 to obtain the initial wastewater, which is used as the feed liquid for the following photocatalytic degradation process of perfluorooctanoic acid.

[0011] In the third step, the photocatalytic degradation process of perfluorooctanoic acid: The nanocatalyst and surfactant are added to the feed liquid obtained in the second step, and after stirring, it is quickly injected into the sample cell; air is bubbled into the sample cell to generate bubbles. When the foam reaches the top of the foam column, the air supply is stopped. At the same time, the tungsten lamp is turned on to start the photocatalytic reaction, and the wastewater is maintained to circulate in the foam; when the foam height decreases to half of the foam column height, air is bubbled again, and when the foam reaches the top of the foam column, the air supply is stopped.

[0012] Preferably, in every 200 mL of the feed liquid, 1.0 - 10.0 g of the nanocatalyst and 0.02 - 0.30 g of the surfactant are added.

[0013] Preferably in any of the above, in the third step, air is bubbled into the sample cell at a certain gas volume flow rate to generate bubbles. The gas volume flow rate is preferably 50 - 500 mL / min, more preferably 50, 100, 150, 200, 250, 300, 350, 400, 450, 500 mL / min. Further preferably, air is bubbled into the sample cell at a gas volume flow rate of 276 - 350 mL / min. Even more preferably, it is 276, 290, 300, 310, 330, 350 mL / min.

[0014] Preferably in any of the above, in the second step, sodium hydroxide is used to adjust the pH value of the industrial wastewater containing perfluorooctanoic acid described in the first step.

[0015] Preferably in any of the above, in the second step, the pH adjustment range is 4.5, 5.0, 5.3, 6.0, 6.8.

[0016] Preferably in any of the above, in the third step, the stirring speed of the feed liquid, the nanocatalyst and the surfactant is 100 rpm for 10 min.

[0017] Preferably in any of the above, the concentration of perfluorooctanoic acid in the industrial wastewater is 1.0 - 20.0 mg / L.

[0018] Preferably, any one of the above is that the nano-photocatalyst is at least one of cadmium sulfide nanoparticles, nano-titanium dioxide, nano-zinc oxide, nano-bismuth oxide, and nano-copper sulfide.

[0019] Preferably, any one of the above is that the particle size of the nano-photocatalyst is 40 nm to 100 nm. Further preferably, it is 40, 50, 60, 70, 80, 90, 100 nm.

[0020] Preferably, any one of the above is that the concentration of the nano-photocatalyst is 5.0 to 50.0 g / L. Further preferably, it is 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0 g / L.

[0021] Preferably, any one of the above is that the metal content of the cadmium sulfide nanoparticles is 99.8%.

[0022] Preferably, any one of the above is that the concentration of the cadmium sulfide nano-catalyst is 5.0 to 50.0 g / L. Further preferably, it is 5.0, 10.0, 15.0, 20.0, 25.0, 30.0, 35.0, 40.0, 45.0, 50.0 g / L.

[0023] Preferably, any one of the above is that the concentration of the surfactant is 0.1 to 1.5 g / L. Further preferably, it is 0.1, 0.3, 0.6, 0.8, 1.0, 1.3, 1.5 g / L.

[0024] Preferably, any one of the above is that the surfactant is polysorbate 80.

[0025] Preferably, any one of the above is that the concentration of polysorbate 80 is 0.1 to 1.5 g / L. Further preferably, it is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 g / L.

[0026] Preferably, any one of the above is that for every 200 mL of the catalytic system of the feed liquid, the irradiation time of the 200 W tungsten lamp is 60 min.

[0027] Preferably, any one of the above is that in the third step, a peristaltic pump is used to maintain the circulation of the wastewater in the foam, and the peristaltic pump is set to 100 to 600 mL / h.

[0028] Preferably, any one of the above includes the following steps:

[0029] Includes the following steps:

[0030] First step, collection and detection of industrial wastewater containing perfluorooctanoic acid: Collect the wastewater generated during the application process of perfluorooctanoic acid, measure its pH value, and detect the concentration of perfluorooctanoic acid therein;

[0031] Second step, pH adjustment of industrial wastewater: Adjust the pH value of the industrial wastewater containing perfluorooctanoic acid described in the first step to 4.5 - 6.8 as the initial wastewater, which is used as the feed liquid for the following photocatalytic degradation process of perfluorooctanoic acid;

[0032] Third step, photocatalytic degradation process of perfluorooctanoic acid: Add 1.0 - 10.0 g of nano - catalyst and 0.02 - 0.30 g of surfactant to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed is 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a certain gas volume flow rate to generate bubbles. Stop introducing air when the foam reaches the top of the foam column, and at the same time, turn on a 200 - W tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, introduce air again, and stop introducing air when the foam reaches the top of the foam column. The irradiation time of the tungsten lamp is 60 min. Use a peristaltic pump (100 - 600 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction ends, collect the liquid in the sample cell and calculate the degradation rate of perfluorooctanoic acid.

[0033] In a preferred embodiment of the present invention, the technical solution adopted to solve this technical problem is:

[0034] A process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam - supported nano - catalyst, comprising the following steps:

[0035] First step, collection and detection of industrial wastewater containing perfluorooctanoic acid

[0036] Collect the wastewater generated during the application process of perfluorooctanoic acid, measure its pH value, and detect the concentration of perfluorooctanoic acid therein;

[0037] Second step, pH adjustment of industrial wastewater

[0038] Adjust the pH value of the industrial wastewater containing perfluorooctanoic acid described in the first step to 4.5 - 6.8 as the initial wastewater, which is used as the feed liquid for the following photocatalytic degradation process of perfluorooctanoic acid;

[0039] Third step, photocatalytic degradation process of perfluorooctanoic acid

[0040] The photocatalytic reactor is as Figure 1As shown, it consists of two parts: a sample cell 4 and a foam column 5. The sample cell 4 is made of a cylindrical plexiglass tube with a height of 200.0 mm and an inner diameter of 44.0 mm. The foam column 5 is made of a cylindrical plexiglass tube with a height of 800.0 mm and an inner diameter of 18.0 mm. The sample cell 4 has an air inlet hole 6, and a gas distributor 3 with a pore size of 125 μm made of sintered glass is installed at the bottom, and a peristaltic pump 2 is connected. The gas volume flow rate is controlled by a rotameter, and the flow range is 30 - 600 mL / min. A 200W tungsten lamp 1 is used as an external visible light source for the photocatalytic reaction. During the reaction process, the photocatalytic reactor and the light source are placed in a dark box (0.8 m × 0.8 m × 1.5 m).

[0041] 1.0 - 10.0 g of the nano-catalyst and 0.02 - 0.30 g of polysorbate 80 (Tween80) are added to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (at a rotation speed of 100 rpm) for 10 min, it is quickly injected into the sample cell. Air is bubbled into the sample cell at a certain gas volume flow rate to generate bubbles. When the foam reaches the top of the foam column, the air injection is stopped, and at the same time, the tungsten lamp is turned on to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, air is injected again, and when the foam reaches the top of the foam column, the air injection is stopped. The tungsten lamp irradiation time is 60 min. The peristaltic pump (100 - 600 mL / h) is used to make the wastewater circulate in the foam. After the photocatalytic reaction, the liquid in the sample cell is collected, and the degradation rate of perfluorooctanoic acid is calculated.

[0042] The nano-catalyst is preferably at least one of cadmium sulfide nanoparticles, nano-titanium dioxide, nano-zinc oxide, nano-bismuth oxide, and nano-copper sulfide. Preferably, the cadmium sulfide nano-catalyst is greenockite, with a particle size of 40 nm and a metal content of 99.8%.

[0043] The concentration of perfluorooctanoic acid in the above-mentioned industrial wastewater is 1.0 - 20.0 mg / L.

[0044] The temperature of the above-mentioned photocatalytic reaction is room temperature, and more preferably 25°C.

[0045] The beneficial effects of the present invention are as follows: Foam is a stable gas dispersion existing in a liquid medium. The bubbles are separated by liquid films to form Prandtl boundary channels for liquid flow. At the same time, surfactant molecules adsorbed on the surface of the liquid film can cause an electric field effect in the channels. Therefore, foam can be used as a carrier for various fine solids. For example, foam separation technology is a special chemical engineering unit process using foam as an adsorption carrier and has been widely applied in the field of wastewater treatment. Using foam as a carrier for loading nano-catalysts has the advantages of simple operation, recyclability of the catalyst, and small dosage of surfactant. Compared with solutions, visible light has less energy loss on the bubble liquid film and in the Prandtl boundary channels, and has a longer transmission depth and higher irradiation efficiency in dry foam.

[0046] Through experiments, this patent found that foam has an entrainment effect on nanoparticles, and the Prandtl boundary channels between bubbles can inhibit the aggregation of nanoparticles into larger particles. Thus, a photocatalytic reaction system was invented by loading nano-catalysts with the aid of foam to strengthen the process of catalytic degradation of perfluorooctanoic acid. Compared with the process of directly applying photocatalysis to degrade perfluorooctanoic acid in wastewater, the photocatalytic reaction system constructed by loading nano-catalysts with foam is much more complex because there are gas-liquid-solid three phases in the system, and it involves the adsorption of perfluorooctanoic acid on the nano-catalyst and the adhesion of the nano-catalyst on the bubble surface. Based on the above situation, the present invention developed a new process for photocatalytic degradation of perfluorooctanoic acid under the control of conditions such as nano-catalyst concentration, surfactant concentration, gas volume flow rate, pH, and peristaltic pump flow rate, which can simultaneously achieve the recovery of the nano-catalyst and the degradation of perfluorooctanoic acid.

[0047] The present invention first applied foam to construct a photocatalytic reaction system. Under the conditions of nano-catalyst concentration of 5.0 - 50.0 g / L, Tween80 concentration of 0.1 - 1.5 g / L, wastewater pH of 4.5 - 6.8, gas volume flow rate of 50 - 500 mL / min, and peristaltic pump flow rate of 100 - 600 mL / h, the foam loading rate of the nano-catalyst is 50.2 - 90.3%, and the degradation rate of perfluorooctanoic acid is 73.2 - 99.9%. After the photocatalytic reaction, the system can perform foam separation operation to recover the nano-catalyst, and then use heat treatment to eliminate Tween80 on the surface of the catalyst, enabling the repeated use of the catalyst. Description of the Drawings

[0048] Figure 1 The preferred photocatalytic reactor of the present invention.

[0049] Markings in the drawings: 1 tungsten lamp, 2 peristaltic pump, 3 gas distributor, 4 sample cell, 5 foam column, 6 air supply hole. Detailed Embodiments

[0050] The present invention will be described more clearly and completely through the following embodiments. However, the described embodiments are only a part of the embodiments of the present invention, not all of them. The embodiments are provided to help understand the present invention and should not be used to limit the protection scope of the present invention.

[0051] Example 1

[0052] First step, collection and detection of industrial wastewater containing perfluorooctanoic acid

[0053] Collect industrial wastewater containing perfluorooctanoic acid, and use a high-performance liquid chromatograph to detect (the same in the following embodiments) that the concentration of perfluorooctanoic acid in the wastewater is 1.0 mg / L and the pH is 3.0.

[0054] Second step, pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0055] Adjust the pH of the industrial wastewater containing perfluorooctanoic acid described in the first step to 4.5 - 4.8 with an aqueous sodium hydroxide solution (1 mol / L), and use it as the feed liquid for constructing a photocatalytic reaction system with a foam-supported cadmium sulfide nanocatalyst.

[0056] Third step, photocatalytic degradation process of perfluorooctanoic acid

[0057] Add 1.0 - 2.4 g of cadmium sulfide nanocatalyst (particle size 40 nm) and 0.02 - 0.07 g of Tween 80 to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a gas volume flow rate of 50 - 125 mL / min to generate bubbles. Stop passing air when the foam reaches the top of the foam column, and at the same time turn on the tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, inject air again, and stop passing air when the foam reaches the top of the foam column. The irradiation time of the tungsten lamp is 60 min. Use a peristaltic pump (100 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction ends, collect the liquid in the sample cell.

[0058] Use a foam-supported cadmium sulfide nanocatalyst to construct a photocatalytic reaction system. The foam loading rate of the cadmium sulfide nanocatalyst is 50.2 - 56.8%, and the degradation rate of perfluorooctanoic acid is 95.7 - 99.9%.

[0059] Note: Since the isoelectric point of cadmium sulfide nanocatalyst is 6.8, the adsorption efficiency of perfluorooctanoic acid on the surface of cadmium sulfide nanocatalyst is related to the pH of the solution. Due to different application processes of perfluorooctanoic acid, there are significant differences in the concentration of perfluorooctanoic acid in industrial wastewater. According to the paper "Study on the Photocatalytic Performance of Perfluorinated Compound-Modified Molecularly Imprinted TiO2 Nanotubes for Perfluorooctanoic Acid" published by researchers Tian Aijun et al. on pages 1 to 5 of Volume 51, Issue 1, 2022 of "Shandong Chemical Industry", the concentration range of perfluorooctanoic acid in the examples of this patent was determined to be 1.0 - 20.0 mg / L by high performance liquid chromatography, with acetonitrile and 0.15% formic acid water (6:4) as the mobile phase, a flow rate of 0.5 mL / min, a detection wavelength of 210 nm, and a column temperature of 20°C.

[0060] Example 2

[0061] First step, collection and detection of industrial wastewater containing perfluorooctanoic acid

[0062] Collect industrial wastewater containing perfluorooctanoic acid, and use high performance liquid chromatography to detect that the concentration of perfluorooctanoic acid in this wastewater is 4.6 mg / L and the pH is 3.0;

[0063] Second step, pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0064] Use sodium hydroxide aqueous solution (1 mol / L) to adjust the pH of the industrial wastewater containing perfluorooctanoic acid described in the first step to 4.9 - 5.2, and use it as the feed liquid for constructing a photocatalytic reaction system with foam-loaded cadmium sulfide nanocatalyst;

[0065] Third step, process for photocatalytic degradation of perfluorooctanoic acid

[0066] Add 2.5 - 3.9 g of cadmium sulfide nanocatalyst (particle size 100 nm) and 0.08 - 0.13 g of Tween 80 to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a gas volume flow rate of 126 - 200 mL / min to generate bubbles. When the foam reaches the top of the foam column, stop introducing air, and at the same time turn on the tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, introduce air again, and stop introducing air when the foam reaches the top of the foam column. The tungsten lamp irradiation time is 60 min. Use a peristaltic pump (200 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction is completed, collect the liquid in the sample cell.

[0067] Construct a photocatalytic reaction system using foam-loaded cadmium sulfide nanocatalyst. The foam loading rate of cadmium sulfide nanocatalyst is 56.9 - 63.5%, and the degradation rate of perfluorooctanoic acid is 91.2 - 95.6%.

[0068] Example 3

[0069] Step 1: Collection and detection of industrial wastewater containing perfluorooctanoic acid

[0070] Collect the industrial wastewater containing perfluorooctanoic acid, and use a high-performance liquid chromatograph to detect that the concentration of perfluorooctanoic acid in the wastewater is 8.2 mg / L and the pH is 3.0;

[0071] Step 2: pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0072] Use an aqueous sodium hydroxide solution (1 mol / L) to adjust the pH of the industrial wastewater containing perfluorooctanoic acid described in Step 1 to 5.3 - 5.6, and use it as the feed liquid for constructing a photocatalytic reaction system with a foam-supported cadmium sulfide nanocatalyst;

[0073] Step 3: Process for photocatalytic degradation of perfluorooctanoic acid

[0074] Add 4.0 - 5.4 g of cadmium sulfide nanocatalyst (particle size 60 nm) and 0.20 - 0.25 g of Tween 80 to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a gas volume flow rate of 201 - 275 mL / min to generate bubbles. Stop passing air when the foam reaches the top of the foam column, and at the same time turn on the tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, bubble air again, and stop passing air when the foam reaches the top of the foam column. The tungsten lamp irradiation time is 60 min. Use a peristaltic pump (300 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction is completed, collect the liquid in the sample cell.

[0075] Construct a photocatalytic reaction system using a foam-supported cadmium sulfide nanocatalyst. The foam loading rate of the cadmium sulfide nanocatalyst is 63.6 - 70.2%, and the degradation rate of perfluorooctanoic acid is 86.7 - 91.1%.

[0076] Example 4

[0077] Step 1: Collection and detection of industrial wastewater containing perfluorooctanoic acid

[0078] Collect the industrial wastewater containing perfluorooctanoic acid, and use a high-performance liquid chromatograph to detect that the concentration of perfluorooctanoic acid in the wastewater is 12.6 mg / L and the pH is 3.0;

[0079] Step 2: pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0080] Use an aqueous sodium hydroxide solution (1 mol / L) to adjust the pH of the industrial wastewater containing perfluorooctanoic acid described in Step 1 to 5.7 - 6.0, and use it as the feed liquid for constructing a photocatalytic reaction system with a foam-supported cadmium sulfide nanocatalyst;

[0081] Step 3, Photocatalytic Degradation Process of Perfluorooctanoic Acid

[0082] Add 5.5 - 6.9 g of cadmium sulfide nanocatalyst (particle size selected from 40 - 100 nm) and 0.14 - 0.19 g of Tween 80 into 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed is 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a gas volume flow rate of 276 - 350 mL / min to generate bubbles. Stop introducing air when the foam reaches the top of the foam column, and at the same time, turn on the tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, introduce air again, and stop introducing air when the foam reaches the top of the foam column. The irradiation time of the tungsten lamp is 60 min. Use a peristaltic pump (400 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction ends, collect the liquid in the sample cell.

[0083] Construct a photocatalytic reaction system by loading cadmium sulfide nanocatalyst on foam. The foam loading rate of the cadmium sulfide nanocatalyst is 70.3 - 76.9%, and the degradation rate of perfluorooctanoic acid is 82.2 - 86.6%.

[0084] Example 5

[0085] Step 1, Collection and Detection of Industrial Wastewater Containing Perfluorooctanoic Acid

[0086] Collect industrial wastewater containing perfluorooctanoic acid, and use a high - performance liquid chromatograph to detect that the concentration of perfluorooctanoic acid in this wastewater is 16.3 mg / L and the pH is 3.0;

[0087] Step 2, pH Adjustment of Industrial Wastewater Containing Perfluorooctanoic Acid

[0088] Adjust the pH of the industrial wastewater containing perfluorooctanoic acid described in the first step to 6.1 - 6.4 with an aqueous sodium hydroxide solution (1 mol / L), and use it as the feed liquid for constructing a photocatalytic reaction system by loading cadmium sulfide nanocatalyst on foam below;

[0089] Step 3, Photocatalytic Degradation Process of Perfluorooctanoic Acid

[0090] 7.0 - 8.4 g of cadmium sulfide nanocatalyst and 0.20 - 0.25 g of Tween80 were added to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (at a rotation speed of 100 rpm) for 10 min, it was quickly injected into the sample cell. Air was bubbled into the sample cell at a gas volume flow rate of 351 - 425 mL / min to generate bubbles. When the foam reached the top of the foam column, the air supply was stopped, and at the same time, the tungsten lamp was turned on to start the photocatalytic reaction. When the foam height decreased to half of the foam column height, air was bubbled in again, and when the foam reached the top of the foam column, the air supply was stopped. The tungsten lamp irradiation time was 60 min. A peristaltic pump (500 mL / h) was used to make the wastewater circulate in the foam. After the photocatalytic reaction ended, the liquid in the sample cell was collected.

[0091] A photocatalytic reaction system was constructed by loading cadmium sulfide nanocatalyst on foam. The foam loading rate of the cadmium sulfide nanocatalyst was 77.0 - 83.6%, and the degradation rate of perfluorooctanoic acid was 77.7 - 82.1%.

[0092] Example 6

[0093] The first step: Collection and detection of industrial wastewater containing perfluorooctanoic acid

[0094] Industrial wastewater containing perfluorooctanoic acid was collected, and the concentration of perfluorooctanoic acid in this wastewater was detected by a high - performance liquid chromatograph to be 20.0 mg / L, and the pH was 3.0.

[0095] The second step: pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0096] When the pH of the industrial wastewater containing perfluorooctanoic acid described in the first step was adjusted to 6.5 - 6.8 with an aqueous sodium hydroxide solution (1 mol / L), it was used as the feed liquid for constructing the photocatalytic reaction system by loading cadmium sulfide nanocatalyst on foam below.

[0097] The third step: Process for photocatalytic degradation of perfluorooctanoic acid

[0098] 8.5 - 10.0 g of cadmium sulfide nanocatalyst and 0.26 - 0.30 g of Tween80 were added to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (at a rotation speed of 100 rpm) for 10 min, it was quickly injected into the sample cell. Air was bubbled into the sample cell at a gas volume flow rate of 426 - 500 mL / min to generate bubbles. When the foam reached the top of the foam column, the air supply was stopped, and at the same time, the tungsten lamp was turned on to start the photocatalytic reaction. When the foam height decreased to half of the foam column height, air was bubbled in again, and when the foam reached the top of the foam column, the air supply was stopped. The tungsten lamp irradiation time was 60 min. A peristaltic pump (600 mL / h) was used to make the wastewater circulate in the foam. After the photocatalytic reaction ended, the liquid in the sample cell was collected.

[0099] Construct a photocatalytic reaction system by loading cadmium sulfide nanocatalyst on water-based foam. The foam loading rate of the cadmium sulfide nanocatalyst is 83.7 - 90.3%, and the degradation rate of perfluorooctanoic acid is 73.2 - 77.6%.

[0100] Example 7

[0101] First step: Collection and detection of industrial wastewater containing perfluorooctanoic acid

[0102] Collect industrial wastewater containing perfluorooctanoic acid, and use a high-performance liquid chromatograph to detect that the concentration of perfluorooctanoic acid in this wastewater is 20.0 mg / L and the pH is 3.0.

[0103] Second step: pH adjustment of industrial wastewater containing perfluorooctanoic acid

[0104] When the pH of the industrial wastewater containing perfluorooctanoic acid described in the first step is adjusted to 4.5 - 6.8 with an aqueous sodium hydroxide solution (1 mol / L), it is used as the feed liquid for constructing a photocatalytic reaction system by loading a nanocatalyst on foam; the nanocatalyst is nanometer titanium dioxide.

[0105] Third step: Photocatalytic degradation process of perfluorooctanoic acid

[0106] Add nanometer titanium dioxide (reaction concentration is 5.0 - 50.0 g / L, particle size is selected from 40 - 100 nm) and 0.1 - 1.5 g / L of Tween 80 to 200 mL of industrial wastewater containing perfluorooctanoic acid. After magnetic stirring (rotation speed is 100 rpm) for 10 min, quickly inject it into the sample cell. Bubble air into the sample cell at a rate of 50 - 500 mL / min to generate bubbles. When the foam reaches the top of the foam column, stop introducing air, and at the same time turn on the tungsten lamp to start the photocatalytic reaction. When the foam height decreases to half of the foam column height, introduce air again. When the foam reaches the top of the foam column, stop introducing air. The irradiation time of the tungsten lamp is 60 min. Use a peristaltic pump (600 mL / h) to make the wastewater circulate in the foam. After the photocatalytic reaction is completed, collect the liquid in the sample cell.

[0107] Construct a photocatalytic reaction system by loading titanium dioxide nanocatalyst on water-based foam, and its technical effect is equivalent to that of constructing a photocatalytic reaction system by loading cadmium sulfide nanocatalyst on water-based foam.

[0108] Example 8

[0109] Example 8 is similar to Example 7, except that the nanocatalyst is nanometer zinc oxide with a concentration of 5.0 - 50.0 g / L and a particle size selected from 40 - 100 nm. Construct a photocatalytic reaction system by loading nanometer zinc oxide on water-based foam, and its technical effect is equivalent to that of constructing a photocatalytic reaction system by loading cadmium sulfide nanocatalyst on water-based foam.

[0110] Example 9

[0111] Example 9 is similar to Example 7, except that the nano-catalyst is bismuth oxide nano-particles with a concentration of 5.0 - 50.0 g / L and a particle size selected from 40 - 100 nm. A photocatalytic reaction system is constructed by loading bismuth oxide nano-particles on the water-based foam, and its technical effect is equivalent to that of the photocatalytic reaction system constructed by loading cadmium sulfide nano-catalyst on the water-based foam.

[0112] Example 10

[0113] Example 10 is similar to Example 7, except that the nano-catalyst is copper sulfide nano-particles with a concentration of 5.0 - 50.0 g / L and a particle size selected from 40 - 100 nm. A photocatalytic reaction system is constructed by loading copper sulfide nano-particles on the water-based foam, and its technical effect is equivalent to that of the photocatalytic reaction system constructed by loading cadmium sulfide nano-catalyst on the water-based foam.

Claims

1. A process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst, characterized in that it comprises the following steps: First step, collect the industrial wastewater containing perfluorooctanoic acid, measure its pH value and detect the concentration of perfluorooctanoic acid therein; Second step, pH adjustment of the industrial wastewater: adjust the pH value of the industrial wastewater containing perfluorooctanoic acid described in the first step to 4.5 - 6.8 as the initial wastewater, which is used as the feed liquid for the following photocatalytic degradation process of perfluorooctanoic acid; Third step, photocatalytic degradation process of perfluorooctanoic acid: add the nanocatalyst and the surfactant to the feed liquid obtained in the second step, stir and then quickly inject it into the sample cell; introduce air into the sample cell to generate bubbles, stop introducing air when the foam reaches the top of the foam column, and at the same time turn on the tungsten lamp to start the photocatalytic reaction, and maintain the circulation of the wastewater in the foam; when the foam height decreases to half of the foam column height, introduce air again, and stop introducing air when the foam reaches the top of the foam column, wherein the surfactant is polysorbate 80, and the nanocatalyst is at least one of cadmium sulfide nanoparticles, nano-titanium dioxide, nano-zinc oxide, nano-bismuth oxide, and nano-copper sulfide.

2. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that in the third step, air is introduced into the sample cell at a gas volume flow rate of 50 - 500 mL / min to generate bubbles.

3. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that in the third step, the stirring speed of the feed liquid with the nanocatalyst and the surfactant is 100 rpm for 10 min.

4. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that the concentration of perfluorooctanoic acid in the industrial wastewater is 1.0 - 20.0 mg / L.

5. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that the particle size of the nanocatalyst nanoparticles is 40 nm - 100 nm.

6. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that the concentration of the nanocatalyst is 5.0 - 50.0 g / L.

7. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that the concentration of the surfactant is 0.1 - 1.5 g / L.

8. The process for enhancing the photocatalytic degradation of perfluorooctanoic acid by a foam-supported nanocatalyst according to claim 1, characterized in that in the third step, a peristaltic pump is used to maintain the circulation of the wastewater in the foam, and the peristaltic pump is set to 100 - 600 mL / h.

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