Method for screening high-yield active oxygen natural suspended particulate matters and degrading new pollutants by using high-yield active oxygen natural suspended particulate matters

Abstract

The invention discloses a method for screening high-yield active oxygen natural suspended particulate matters and degrading new pollutants by using the high-yield active oxygen natural suspended particulate matters, which comprises the following steps: firstly, collecting the suspended particulate matters from surface water, measuring the chemical oxygen demand (COD) and the aromaticity of surface organic matters of the suspended particulate matters, and screening the suspended particulate matters with high-yield active oxygen activity; the method comprises the following steps: adding high-activity suspended particulate matters into a to-be-treated water body containing new pollutants, enabling the suspended particulate matters to adsorb the new pollutants to the surfaces of the suspended particulate matters, and providing illumination after adsorption is completed to enable the suspended particulate matters to generate high-concentration active oxygen on the surfaces of the suspended particulate matters, so that rapid degradation of the new pollutants is realized. The method has the characteristics of greenness, economy, high efficiency and easiness in operation in the aspect of removing new pollutants.

Description

Technical Field

[0001] The invention belongs to the field of water treatment, and in particular relates to a method for screening high-yield active oxygen natural suspended particulate matter and degrading new pollutants. Background Art

[0002] With the increasing production and use of various chemicals, a large number of new pollutants have entered natural water bodies and have been detected in many water bodies around the world. Many of these new pollutants exhibit characteristics such as biotoxicity, environmental persistence, and bioaccumulation. These new pollutants entering water bodies can threaten ecological security and human health through various pathways, including ingestion, inhalation, and skin contact by humans and animals.

[0003] Sewage treatment plants are the last line of defense for urban and rural water systems. However, the mainstream activated sludge method in sewage treatment plants is not effective in removing new pollutants that are difficult to biodegrade. In order to remove new pollutants remaining in the effluent, deep treatment is often required, such as advanced oxidation technology. Advanced oxidation technology can efficiently degrade new pollutants by producing active oxygen species with strong oxidizing properties, such as photocatalytic oxidation, ozone oxidation, electrochemical oxidation, Fenton oxidation, etc. However, the current advanced oxidation technology has various problems in practical applications, such as high treatment costs, high energy consumption, high oxidant consumption, and secondary pollution. Therefore, in order to solve the problem of new pollutants remaining in the effluent of sewage treatment plants, it is urgent to develop an economical, green, simple and efficient treatment method. Summary of the Invention

[0004] The present invention addresses the problems existing in existing sewage treatment plants in treating new pollutants and provides a method for screening natural suspended particulate matter with high yield of active oxygen and its degradation of new pollutants. The purpose is to utilize the characteristics of suspended particulate matter, which are green and non-toxic, low cost, easy to adsorb new pollutants, and can produce high concentrations of active oxygen on the surface under light, to achieve efficient and low-cost degradation of new pollutants in sewage.

[0005] In order to achieve the purpose, the present invention adopts the following technical solutions:

[0006] A method for screening high-yield active oxygen natural suspended particulate matter and degrading new pollutants thereof comprises the following steps:

[0007] (1) Screening of highly active suspended particles: Collect suspended particles from surface water, measure the chemical oxygen demand (COD) and surface organic matter aromaticity of the suspended particles, and screen suspended particles with high COD and high surface organic matter aromaticity as highly active suspended particles;

[0008] (2) Adsorption of new pollutants by suspended particulate matter: The highly active suspended particulate matter obtained in step (1) is added to the water body to be treated containing new pollutants at a final concentration of 0.1 to 1 g / L, and stirred in the dark for 0.5 to 4 hours to allow the suspended particulate matter to adsorb the new pollutants onto its surface;

[0009] (3) Photodegradation of new pollutants: After the suspended particulate matter adsorbs new pollutants and reaches equilibrium, light is provided to stimulate the suspended particulate matter to produce active oxygen to degrade the new pollutants; the concentration changes of new pollutants are monitored until the sewage meets the treatment requirements.

[0010] Furthermore, in step (1), the step of collecting the suspended particulate matter is as follows: first, the surface water is passed through a 200-mesh sieve, and the filtrate is collected. The filtrate is then passed through a 0.45 μm cellulose acetate membrane, and the membrane is replaced when the filtration speed is too slow, and the filtered membrane is collected. All the filtered membranes are added to an appropriate amount of deionized water, and the suspended particulate matter on the membrane is ultrasonically removed for 10 minutes to obtain a suspended particulate matter concentrate. The suspended particulate matter concentrate is divided into 50 mL centrifuge tubes, centrifuged at 6000 rpm for 5 minutes, the supernatant is discarded, the suspended particulate matter is resuspended with deionized water and evenly dispersed by vortexing, and centrifuged again at 6000 rpm for 5 minutes, and this is repeated three times to complete the cleaning. The washed suspended particulate matter is placed in a freeze dryer and vacuum freeze-dried at -50°C for 24 to 48 hours to obtain dried suspended particulate matter, which is stored at room temperature in the dark for later use.

[0011] Furthermore, in step (1), the COD of the suspended particulate matter is determined by resuspending the dried suspended particulate matter in deionized water, fully dispersing the suspended particulate matter by ultrasound, and determining the COD of the dispersed suspension. The specific method for determining COD is described in the "Water and Wastewater Monitoring and Analysis Methods, Fourth Edition" (China Environmental Press, Beijing). After the COD of the suspension is measured (in mg / L) according to this method, it is normalized according to the concentration of the suspended particulate matter and converted to g / g, that is, the COD per gram of suspended particulate matter.

[0012] Furthermore, in step (1), the step of determining the aromaticity of the organic matter on the surface of the suspended particles is as follows: adding the dried suspended particles to a 0.1M NaOH solution with a concentration of 0.1 to 1g / L of the suspended particles, shaking at room temperature and darkness for 24 hours, extracting the organic matter on the surface of the particles, and then neutralizing with 6M HCl to pH = 7, and then passing through a 0.45μm cellulose acetate membrane, collecting the filtrate, and obtaining an extracted organic matter solution. The UV-visible absorption spectrum of the extracted organic matter solution is measured, and the ratio of the absorbance at 254nm and 204nm (A 254 / A 204) is used as an indicator to judge the aromaticity of organic matter, and the ratio is positively correlated with the aromaticity.

[0013] Furthermore, the COD of the highly active suspended particles is greater than 0.5 g / g, and A 254 / A 204 >0.27.

[0014] Furthermore, the method of the present invention is applicable to treating a variety of new pollutants, including but not limited to one or more of cimetidine and medetomidine.

[0015] Furthermore, in actual water treatment, sunlight is directly used for the illumination treatment in step (3). In the experiment of the present invention, the light source used is a 500W xenon lamp equipped with a 290nm filter to filter light with a wavelength below 290nm to simulate sunlight.

[0016] Furthermore, in step (3), the monitoring of the change in the concentration of the new pollutant is performed by high performance liquid chromatography equipped with an ultraviolet detector, and the determination method is: 5mM KH2PO4 (pH=3) and acetonitrile are used as the mobile phase, and the detection wavelength is 219nm.

[0017] The beneficial effects of the present invention are embodied in:

[0018] 1. The present invention uses natural suspended particulate matter to degrade new pollutants. Suspended particulate matter is cheap, readily available, non-toxic, and will not cause secondary pollution;

[0019] 2. The method for screening highly active suspended particulate matter proposed in the present invention is simple to operate. The screened suspended particulate matter can generate a high concentration of active oxygen on the surface under light, which degrades new pollutants adsorbed on the surface. It does not require special devices and equipment, is simple to operate, and is easy to promote.

[0020] 3. The suspended particulate matter screened by the present invention can utilize sunlight when treating pollutants without the need for additional energy input. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Qualitative and quantitative characterization of the generation of reactive oxygen species (ROS) by suspended particulate matter (SPM) in Example 1: (a) imaging results of the reactive oxygen species fluorescent probe; (b) degradation kinetics of the singlet oxygen probe (furfuryl alcohol).

[0022] Figure 2 It is the degradation kinetics curve of cimetidine in Example 2.

[0023] Figure 3Comparison of singlet oxygen generation and cimetidine degradation by different SPMs in Example 3: (a) COD and aromaticity of different SPMs; (b) kinetic curves of singlet oxygen probe (furfuryl alcohol) degradation by different SPMs; (c) steady-state concentrations of singlet oxygen generated by different SPMs; (d) kinetic curves of cimetidine degradation by different SPMs.

[0024] Figure 4 This is the degradation kinetics curve of medetomidine in Example 4. DETAILED DESCRIPTION

[0025] To more clearly describe the technical solution of the present invention, preferred embodiments are described in detail with reference to the accompanying drawings. Obviously, the technical solution of the present invention is not limited to the specific embodiments listed below. All other embodiments obtained by persons of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following embodiments, the light source used is a 500W xenon lamp equipped with a 290nm filter to filter light with a wavelength below 290nm to simulate sunlight.

[0027] Example 1

[0028] 1. Collection of suspended particulate matter (SPM)

[0029] First, pass 50 L of surface water containing SPM through a 200-mesh sieve and collect the filtrate. Then, pass the filtrate through a 0.45 μm cellulose acetate membrane. Replace the membrane if the filtration rate becomes too slow. Collect the filtered membrane. Place all filtered membranes in a 500 mL plastic beaker, add 200 mL of deionized water, and sonicate for 10 minutes to remove the SPM from the membrane. Discard the membrane to obtain the SPM concentrate. The SPM concentrate is divided into 50 mL centrifuge tubes and centrifuged at 6000 rpm for 5 minutes. Discard the supernatant, resuspend the SPM in deionized water, vortex to evenly disperse it, and centrifuge again at 6000 rpm for 5 minutes. Repeat this process three times to complete the cleaning process. The cleaned SPM is freeze-dried in a freeze dryer at -50°C under vacuum for 24 hours to obtain the dried SPM, which is then stored at room temperature in the dark.

[0030] In step 1, surface water was collected from China Railway Construction International City Wetland Park in Hefei City, Anhui Province in April 2024, and the obtained suspended particulate matter was SPM-4.

[0031] 2. Qualitative proof of SPM generating reactive oxygen species (ROS)

[0032] Weigh 4 mg of the SPM obtained in step 1 and place it in a 2 mL plastic centrifuge tube. Add 0.4 mL of deionized water and sonicate for 10 minutes to achieve full dispersion to obtain an SPM suspension. Prepare a ROS capture gel membrane, place the ROS capture gel membrane horizontally, add an appropriate amount of deionized water to wet its surface, carefully add 50 μL of the above SPM suspension to the center of the ROS capture gel membrane, let it stand for 3 minutes, and allow the SPM to precipitate on its surface. Use an ultraviolet LED lamp with a power of 10 W and a wavelength range of 360-365 nm to irradiate vertically for 1 minute, and use a stereo fluorescence microscope to take bright field photos and fluorescence photos of the ROS capture gel membrane. When taking fluorescence photos, the excitation wavelength is 488 nm and the emission wavelength is 525 nm. ROS will oxidize the probe 2',7'-dichlorodihydrofluorescein (H2DCF) to generate a product with green fluorescence, 2',7'-dichlorofluorescein (DCF). Green fluorescence can be observed after the suspended particles are illuminated (see Figure 1 (a)), indicating that ROS were generated on its surface.

[0033] The steps for preparing the ROS-capturing gel membrane are as follows: First, 3.9 mg of 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA, a fluorescent ROS probe) was weighed and placed in a 2 mL plastic centrifuge tube. 400 μL of N,N-dimethylformamide (DMF) was added to fully dissolve the solution. Then, 400 μL of 20 mM NaOH solution was added and incubated in the dark at 37°C for 30 min to hydrolyze the solution into 2',7'-dichlorodihydrofluorescein (H2DCF). Next, 1.2 g of agarose was added to a 100 mL Erlenmeyer flask containing 60 mL of 10 mM phosphate-buffered saline (PBS, pH 7). The solution was heated in a microwave for 3 min to fully dissolve the agarose. After cooling to approximately 60°C, 600 μL of the H2DCF solution was added and shaken thoroughly. The agarose gel mixture was then filled into a 2 × 2 cm plastic binding plate. The gel membrane was cured at 4°C in the dark for 2 h to obtain a ROS capture gel membrane.

[0034] 3. Quantitative demonstration of ROS production by SPM

[0035] The SPM obtained in step 1 above was added to 4 mL of a solution containing 50 μM singlet oxygen probe (furfuryl alcohol), mixed evenly and adjusted to pH 8. The final concentration of SPM was 0.4 g / L. The container used was a 10 mL quartz test tube. The solution was placed in a photoreactor and stirred in the dark for 2 h to reach adsorption equilibrium, and then light was provided. The reaction temperature was controlled at 25 ± 1 ° C by circulating water, and the stirring speed was controlled at 800 rpm by magnetic stirring. The concentration change of furfuryl alcohol in water was detected by high performance liquid chromatography (see Figure 1(b)) The detection method is: water and acetonitrile as mobile phases, and the detection wavelength is 219 nm. According to the pseudo-first-order degradation rate of furfuryl alcohol, the steady-state concentration of singlet oxygen generated by SPM can be obtained to be 1.66×10 -13 M. For the specific quantitative method of the steady-state concentration of reactive oxygen species, please refer to the literature "The Role of Dissolved Organic Matter Composition in Determining Photochemical Reactivity at the Molecular Level".

[0036] Example 2

[0037] 1. Same as step 1 of Example 1.

[0038] 2. Photodegradation of new pollutants:

[0039] The SPM obtained in step 1 was added to 4 mL of water to be treated containing 2 mg / L cimetidine, with a final SPM concentration of 0.4 g / L. The reaction mixture was placed in a 10 mL quartz tube and stirred in the dark for 2 hours to reach adsorption equilibrium. The SPM was then illuminated to excite the SPM to produce reactive oxygen species for cimetidine degradation. The reaction temperature was controlled at 25 ± 1° C. using circulating water, and the stirring speed was controlled at 800 rpm using magnetic stirring. The residual cimetidine concentration was detected by high performance liquid chromatography using 5 mM KH2PO4 (pH = 3) and acetonitrile as the mobile phase at a detection wavelength of 219 nm.

[0040] After 6 h of illumination, 73.0% of cimetidine was degraded in the water with SPM added, while no degradation was observed in the water without SPM added (see Figure 2 ), indicating that SPM produces reactive oxygen species under light that can cause the degradation of cimetidine.

[0041] Example 3

[0042] 1. The same as step 1 of Example 1, except that different SPMs were collected from different surface water bodies. The sampling locations and sampling times of different SPMs are shown in Table 1.

[0043] Table 1. Sampling locations and times for different suspended particulate matter (SPM)

[0044] suspended particulate matter Longitude of sampling site (E) Latitude of sampling site (N) Sampling time SPM-1 117.236 31.878 2024.04 SPM-2 117.238 31.876 2024.04 SPM-3 117.250 31.841 2024.04 SPM-4 117.240 31.901 2024.04

[0045] 2. Screening of SPMs with different ROS-producing activities

[0046] Determine the COD and surface organic matter aromaticity of different SPMs obtained in step 1, and screen SPMs with different ROS production activities (see Figure 3(a)), where the ROS production activity of SPM is positively correlated with its COD and the aromaticity of surface organic matter. The order of ROS production activity of SPM is: SPM-1 < SPM-2 < SPM-3 < SPM-4. Among them:

[0047] The steps for measuring the COD of SPM are as follows: Weigh 4 mg of the SPM obtained in step 1 and place it in a 50 mL plastic centrifuge tube. Add 10 mL of deionized water and ultrasonicate for 10 min to achieve sufficient dispersion. Then measure the COD of the dispersed suspension. The specific method for COD measurement refers to the "Fourth Edition of Monitoring and Analysis Methods for Water and Wastewater" (China Environmental Science Press, Beijing). After measuring the COD (unit: mg / L) of the SPM suspension by this method, normalize it according to the concentration of SPM and convert it to g / g, that is, the COD per g of SPM.

[0048] The steps for measuring the aromaticity of surface organic matter of SPM are as follows: Weigh 4 mg of the SPM obtained in step 1 and place it in a 50 mL plastic centrifuge tube. Add 10 mL of 0.1 M NaOH solution and shake it at room temperature in the dark for 24 h to extract the organic matter on the surface of the particulate matter. Then neutralize it to pH = 7 with 6 M HCl, and then pass it through a 0.45 μm cellulose acetate membrane. Collect the filtrate to obtain the extracted organic matter solution. Measure the ultraviolet-visible absorption spectrum of the extracted organic matter solution, and use the ratio of absorbance at 254 nm and 204 nm (A 254 / A 204 ) as an index to judge the aromaticity of organic matter. This ratio is positively correlated with aromaticity.

[0049] 3. Steady-state concentration of singlet oxygen generated by different SPMs

[0050] Add the different SPMs obtained in step 1 above to 4 mL of a solution containing 50 μM singlet oxygen probe (furfuryl alcohol) respectively. The final concentration of SPM is 0.4 g / L. The container used is a 10 mL quartz test tube. Place it in a photoreactor and stir it in the dark for 2 h to reach adsorption equilibrium, and then provide light. Control the reaction temperature at 25 ± 1 °C through circulating water, control the stirring speed at 800 rpm through magnetic stirring, and detect the change in the concentration of furfuryl alcohol in water by high performance liquid chromatography (see Figure 3 (b)). According to the pseudo-first-order degradation rate of furfuryl alcohol, the order of the steady-state concentration of singlet oxygen generated by different SPMs can be obtained: SPM-1 < SPM-2 < SPM-3 < SPM-4 (see Figure 3(c)), which is consistent with the results screened in step 2, proving the reliability of the screening method in step 2. The specific quantitative method for the steady-state concentration of reactive oxygen species refers to the literature "The Role of Dissolved Organic Matter Composition in Determining Photochemical Reactivity at the Molecular Level".

[0051] 4. Efficiency of Different SPMs in Degrading New Pollutants

[0052] The different SPMs obtained in step 1 were respectively added to 4 mL of the water to be treated containing 2 mg / L cimetidine. The final concentration of SPM was 0.4 g / L. The container used was a 10 mL quartz test tube, which was placed in a photoreactor and stirred in the dark for 2 h to reach the adsorption equilibrium. Then, light was provided to stimulate the SPM to generate reactive oxygen species for the degradation of cimetidine. The reaction temperature was controlled at 25 ± 1 °C by circulating water, the stirring speed was controlled at 800 rpm by magnetic stirring, and the residual cimetidine concentration was detected by a high-performance liquid chromatograph. The detection method was: 5 mM KH2PO4 (pH = 3) and acetonitrile as the mobile phase, and the detection wavelength was 219 nm.

[0053] After 6 h of illumination, the efficiency order of SPM in degrading cimetidine was: SPM-1 < SPM-2 < SPM-3 < SPM-4 (see Figure 3 (d)), which is consistent with the results screened in step 2, further proving the reliability of the screening method in step 2. By screening, SPMs with high reactive oxygen production can be obtained to achieve more efficient degradation of new pollutants.

[0054] Example 4

[0055] 1. The same as step 1 of Example 1.

[0056] 2. Photodegradation of New Pollutants

[0057] The SPM obtained in step 1 was added to 4 mL of the water to be treated containing 2 mg / L medetomidine. The final concentration of SPM was 0.4 g / L. The container used was a 10 mL quartz test tube, which was placed in a photoreactor and stirred in the dark for 2 h to reach the adsorption equilibrium. Then, light was provided to stimulate the SPM to generate reactive oxygen species for the degradation of medetomidine. The reaction temperature was controlled at 25 ± 1 °C by circulating water, the stirring speed was controlled at 800 rpm by magnetic stirring, and the residual medetomidine concentration was detected by a high-performance liquid chromatograph. The detection method was: 5 mM KH2PO4 (pH = 3) and acetonitrile as the mobile phase, and the detection wavelength was 219 nm.

[0058] After 6 h of illumination, the degradation of medetomidine in water with SPM was 94.7% (see Figure 4 ),contrast Figure 2 , indicating that SPM has a good degradation effect on different types of new pollutants.

[0059] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for screening high-yield active oxygen natural suspended particulate matter and degrading new pollutants, characterized in that: The steps include: (1) Screening of highly active suspended particles: Collect suspended particles from surface water, measure the chemical oxygen demand (COD) and surface organic matter aromaticity of the suspended particles, and screen suspended particles with high COD and high surface organic matter aromaticity as highly active suspended particles; (2) Suspended particles adsorb new pollutants: The highly active suspended particles obtained in step (1) are added to the water to be treated containing new pollutants, and stirred in the dark to allow the suspended particles to adsorb the new pollutants onto their surfaces; (3) Photodegradation of new pollutants: After the suspended particulate matter adsorbs new pollutants and reaches equilibrium, light is provided to stimulate the suspended particulate matter to produce active oxygen to degrade the new pollutants; the concentration changes of new pollutants are monitored until the sewage meets the treatment requirements.

2. The method according to claim 1, wherein: In step (1), the step of collecting the suspended particulate matter is as follows: first passing the surface water through a 200-mesh sieve to collect the filtrate; passing the filtrate through a 0.45 μm cellulose acetate membrane to collect the suspended particulate matter on the cellulose acetate membrane, washing it with deionized water, and then placing it at -50°C for vacuum freeze drying for 24 to 48 hours to obtain the dried suspended particulate matter, which is then stored at room temperature in the dark for future use.

3. The method according to claim 1, wherein: In step (1), the COD of the suspended particulate matter is determined by resuspending the dried suspended particulate matter in deionized water, fully dispersing the suspended particulate matter by ultrasound, and determining the COD of the dispersed suspension.

4. The method according to claim 1, wherein: In step (1), the step of determining the aromaticity of the organic matter on the surface of the suspended particles is as follows: extracting the organic matter on the surface of the suspended particles, measuring the UV-visible absorption spectrum of the extracted organic matter solution, and converting the absorbance ratio A at 254 nm to that at 204 nm. 254 / A 204 As an indicator of the aromaticity of organic matter, this ratio is positively correlated with the aromaticity.

5. The method according to claim 1, wherein: In step (1), the COD of the highly active suspended particulate matter is greater than 0.5 g / g, and A 254 / A 204 >0.

27.

6. The method according to claim 1, wherein: In step (2), the highly active suspended particulate matter is added to the water body to be treated containing new pollutants at a final concentration of 0.1 to 1 g / L.

7. The method according to claim 1, wherein: In step (2), the stirring time is 0.5 to 4 hours.

8. The method according to claim 1, wherein: In step (3), the light source of the illumination is a xenon lamp simulating sunlight or real sunlight.

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