A preparation method of a photosensitive flocculant and its application

Abstract

The present application discloses a preparation method and application of a photosensitive flocculant. Urea and sodium citrate are ground into powder in an agate mortar, and then the powder is placed in a polytetrafluoroethylene-lined autoclave and heated to obtain a yellowish-brown product. The obtained yellowish-brown product is dissolved in H2O and dialyzed to obtain a solution. The solution is centrifuged and filtered through a filter membrane to obtain a purified c-CNQDs solution, which is placed in a round-bottom flask. Weigh chitosan, dissolve it in HCl, adjust the pH after it is dissolved, and pour it into the purified c-CNQDs solution to obtain a mixed solution. Weigh N-hydroxysuccinimide NHS and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EDC, dissolve them in water, and pour them into the above mixed solution after NHS and EDC are dissolved. Adjust the temperature of the water bath where the round-bottom flask is located to 10-35 °C, stir mechanically, and irradiate under a xenon lamp to obtain the final product, the photosensitive flocculant.

Description

Technical Field

[0001] This application relates to the technical field of environmental pollution control, and particularly to a preparation method and application of a photosensitive flocculant. Background Art

[0002] Providing safe drinking water is one of the primary tasks of humanity. However, the deterioration of surface water pollution in drinking water supply remains a global challenge. In addition to common water pollutants (suspended solids [SS], natural organic matter [NOM]), emerging micropollutants, such as anthropogenic pharmaceuticals and pesticides, are frequently detected in surface water. The toxicological associations between these chemicals and adverse human health effects have been established. Since conventional methods cannot aggregate ultra-low concentration small particle low molecular weight organic pollutants into mesoscale coagulation nuclei for sedimentation separation, drinking water treatment plants (DWTPs) often have variable and insufficient removal of these refractory low molecular weight micropollutants.

[0003] Advanced water treatment technologies, such as oxidation, adsorption, and membrane filtration, can effectively remove emerging pollutants, but these technologies usually require traditional pretreatment methods to remove colloids and suspended particles. In practice, the combination of multiple water treatment technologies greatly increases treatment time, energy consumption, capital cost, and land use. The flocculation method is a cost-effective and simple water treatment technology with a long history and remains the mainstream process in DWTPs. There is an obstacle to the application of traditional flocculants in water treatment, that is, they cannot effectively remove low molecular weight trace dissolved pollutants. Among various effective methods to achieve this goal, flocculation using functionalized biopolymers has been proven to be promising.

[0004] Carbon nitride (CN) is a conjugated polymer semiconductor with ammonia-bridged triazine (C 3 N 3 ) or heptazine (C 6 N 7 ) rings as the basic structural units, which has attracted extensive attention due to its anisotropic graphene-like two-dimensional structure, low cost, relatively small bandgap, and the diversity of structure and function. Similar to graphene / carbon quantum dots, carbon nitride quantum dots (CNQDs) are tiny in size and rich in functional groups, and often have unique optical properties such as a wide response range in the visible light range and bright photoluminescence, so they are becoming increasingly popular. Inspired by the "emergence theory", that is, when some simple individuals (agents) move in an environment, emergent behaviors or emergent properties may appear, forming more complex behaviors at the overall level. CNQDs can self-assemble to form superlattices or superstructures under photoinduced conditions, which is similar to the "click reaction" process of macromolecules, in which -OH and -NH 2 functional groups activated along the boundary initiate the crosslinking of adjacent quantum dots through photoinduced effects.

[0005] In view of the problem that traditional flocculants cannot effectively remove trace dissolved pollutants with low molecular weight in water, the present invention designs a photosensitive flocculant which can spontaneously form a larger structure under light induction. This flocculant has strong interaction and sweeping effect with drugs and pesticides, and can remove trace dissolved pollutants with low molecular weight in water.

[0006] Chinese Patent CN104774290A discloses a pH- and temperature-dual sensitive chitosan flocculant, its preparation method and application, which is obtained by graft copolymerization of carboxymethyl chitosan with dimethyldiallylammonium chloride and N-isopropylacrylamide under acidic conditions. The flocculant of the present invention has both pH sensitivity and temperature sensitivity, which not only increases the molecular weight and enhances the bridging flocculation effect, but also can meet the requirements of flocculation and removal of water pollutants with different characteristics under different environmental conditions. Especially for pollutants with easily convertible surface charges and hydrophilic / hydrophobic properties, it has excellent flocculation ability. The raw material chitosan has a wide source, is non-toxic, biodegradable and has no risk of secondary pollution; it has good characteristics of flocculating heavy metal ions and small molecule organic pollutants, and has many functions such as antibacterial, deodorizing, decolorizing and effectively reducing the COD value. However, considering that the removal rate of trace pesticides in the prior art has not been studied, and there are problems such as multi-energy consumption caused by adjusting the two variables of pH and temperature, the prior art is slightly insufficient. Summary of the Invention

[0007] Technical problems to be solved:

[0008] The technical problem to be solved by this application is to provide a preparation method and application of a photosensitive flocculant in view of the problems of low removal rate of drugs and pesticides by traditional flocculants and limited application scope. First, urea and anhydrous sodium citrate are used to synthesize carbon nitride quantum dots (CNQDs), and then they are reacted with chitosan, which not only increases the number of functional groups and the molecular weight, enhances the flocculation performance, but also the flocculant can efficiently remove trace dissolved pollutants with low molecular weight in water after light induction.

[0009] Technical solution:

[0010] A preparation method of a photosensitive flocculant, and the specific process conditions are as follows:

[0011] The first step: Grind urea and sodium citrate into powder in an agate mortar, and then place the powder in a polytetrafluoroethylene-lined autoclave and heat to obtain a yellow-brown product;

[0012] The second step: Dissolve the obtained yellow-brown product in H 2 O and dialyze to obtain a solution; the mass ratio of the yellow-brown product to H 2 O is 1:3;

[0013] Step 3: Centrifuge the solution at a speed of 4000 - 10000 r / min and filter it through a filter membrane to obtain a purified c-CNQDs solution, which is placed in a round-bottom flask;

[0014] Step 4: Weigh chitosan and dissolve it in 1 - 5% HCl by mass. The mass ratio of chitosan to HCl is 1:1 - 10. After it is dissolved, adjust the pH and pour it into the purified c-CNQDs solution to obtain a mixed solution;

[0015] Step 5: Weigh N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), dissolve them in water, and pour the solution into the above mixed solution after dissolution;

[0016] Step 6: Adjust the temperature of the water bath where the round-bottom flask is located to 10 - 35 °C. After mechanical stirring, irradiate it under a xenon lamp to obtain the final product, a photosensitive flocculant. The light intensity is 30 mW / cm 2 。

[0017] Furthermore, in the first step, the molar ratio of sodium citrate to urea is 1:6 - 11.

[0018] As a preferred technical solution of this application: In the first step, the heating temperature in the polytetrafluoroethylene-lined autoclave is 100 - 150 °C, and the heating time is 1 - 3.5 h.

[0019] As a preferred technical solution of this application: In the second step, the dialysis parameters are MWCO: 0.5 - 3.5 kDa, and the dialysis time is 24 - 52 h.

[0020] As a preferred technical solution of this application: In the third step, the centrifugation time is 5 - 20 min, and the filter pore size of the filter membrane is 100 - 450 nm.

[0021] As a preferred technical solution of this application: In the fourth step, adjust the pH to 5 - 7.5.

[0022] As a preferred technical solution of this application: In the fifth step, the molar ratio of NHS, EDC, and water is 1:1.5 - 4:5 - 20, and the molar ratio of chitosan to NHS and EDC is 1:1 - 3:1 - 3.

[0023] As a preferred technical solution of this application: In the sixth step, the mechanical stirring speed is 200 - 350 r / min, the stirring duration is 6 - 10 h, and then irradiate it under a xenon lamp for 0 - 7 h to obtain the final product, a photosensitive flocculant.

[0024] As a preferred technical solution of this application: The specific synthesis scheme of the preparation method is as follows:

[0025]

[0026] The present application also discloses the application of the photosensitive flocculant prepared by the above preparation method in the form of a flocculant mother liquor in water treatment. Seven 1-L beakers were taken, and simulated polluted wastewater was prepared in each beaker; the simulated polluted wastewater was 7.4 mg / L humic acid, 10 mg / L kaolin, 1 μg / L acetamiprid AAP, 1 μg / L roxithromycin ROX, 1 μg / L norfloxacin NOR, 1 μg / L sulfadiazine SDZ, 1 μg / L diclofenac DCF, 1 μg / L metaldehyde MET, 1 μg / L sulfamethoxazole SMX, 1 μg / L carbendazim CBZ, 1 μg / L tetracycline TC, 1 μg / L glyphosate GPS, 1 μg / L tylosin TYL; 0 - 60 mg / L of the flocculant mother liquor was added to each beaker, and the concentration of the photosensitive flocculant in the flocculant mother liquor was 5 g / L. Then, rapid stirring was carried out at 250 r / min for 5 min on a six-joint coagulation experiment stirrer, slow stirring was carried out at 50 r / min for 15 min, and static sedimentation was carried out for 1 h; the supernatant was taken, and the remaining humic acid UV 254 concentration in the water body was measured by ultraviolet absorption spectroscopy, the remaining turbidity Turbidity in the water body was measured by a turbidimeter, the remaining dissolved organic carbon DOC was measured by a total organic carbon analyzer, and the remaining concentrations of acetamiprid AAP, roxithromycin ROX, norfloxacin NOR, sulfadiazine SDZ, diclofenac DCF, metaldehyde MET, sulfamethoxazole SMX, carbendazim CBZ, tetracycline TC, glyphosate GPS, and tylosin TYL in the water body were measured by high performance liquid chromatography-mass spectrometry.

[0027] Beneficial effects:

[0028] Compared with the prior art, the preparation method and application of the photosensitive flocculant described in the present application adopt the above technical solutions and have the following technical effects:

[0029] 1. The photosensitive flocculant of the present invention is beneficial to the photoinduced self-assembly of the flocculant due to the grafting of carbon nitride quantum dots, thereby improving the flocculation efficiency;

[0030] 2. The graft copolymerization method of the photosensitive flocculant of the present invention is simple and easy to operate, and more active sites can be introduced, which is beneficial to the removal of pollutants;

[0031] 3. Chitosan in the photosensitive flocculant of the present invention has biodegradability and non-toxicity, and there is no secondary pollution to the treated water body;

[0032] 4. The carbon nitride quantum dots in the photosensitive flocculant of the present invention are rich in functional groups and have unique optical properties such as a wide response range in the visible light range and photoluminescence;

[0033] 5. The hydrophobic association between the photosensitive flocculant and pesticides and antibiotics effectively improves their removal rates;

[0034] 6. The preparation method of the photosensitive flocculant of the present invention is simple, the operation is easy, the cost of the main raw materials is low, and it is suitable for large-scale industrial production. It is an economical preparation method for obtaining high-quality water treatment agents;

[0035] 7. The photosensitive flocculant has a higher removal rate for trace antibiotics and pesticides in water compared to other commercial flocculants, and the removal rate of trace antibiotics and pesticides is nearly 50% higher than that of other commercial flocculants; Description of the Drawings

[0036] Figure 1 It is the photoluminescence spectrum diagram (excitation wavelength 320 nm) of the photosensitive flocculant in Examples 1-6 of this application;

[0037] Figure 2 It is the removal rate result diagram of the photosensitive flocculant in Example 1 for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm;

[0038] Figure 3 It is the removal rate result diagram of the photosensitive flocculant in Example 2 for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm;

[0039] Figure 4 It is the removal rate result diagram of the photosensitive flocculant in Example 3 for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm;

[0040] Figure 5 Removal rate results graph of the photosensitive flocculant for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm in Example 4;

[0041] Figure 6 Removal rate results graph of the photosensitive flocculant for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm in Example 5;

[0042] Figure 7 Removal rate results graph of the photosensitive flocculant for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), tylosin (TYL) at the optimal dosage of 30 ppm in Example 6. Detailed implementation method

[0043] The present invention will be further described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments:

[0044] Example 1:

[0045] A method for preparing a photosensitive flocculant, grinding urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:6) into powder in an agate mortar, then placing the powder in a polytetrafluoroethylene-lined autoclave and heating at 100 °C for 1 h. Dissolve the obtained yellow-brown product in H 2 O and dialyze (MWCO: 1 kDa) for 24 h; the mass ratio of the yellow-brown product to H 2 O is 1:3. Subsequently, centrifuge the solution at a speed of 4000 r / min for 5 min and filter through a 100 nm filter membrane to obtain a purified c-CNQDs solution.

[0046] Weigh a certain amount of chitosan and dissolve it in 5% HCl by mass. The mass ratio of chitosan to HCl is 1:1. After it is dissolved, adjust the pH to 5 and pour it into the c-CNQDs solution to obtain a mixed solution. Additionally, weigh N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), dissolve them in water, and the molar ratio of NHS, EDC, and water is 1:1.5:5. After NHS and EDC are dissolved, pour them into the above mixed solution, and the molar ratio of chitosan to NHS and EDC is 1:1:1. Adjust the temperature of the water bath where the round-bottom flask is located to 10 °C, stir mechanically for 6 h at a stirring speed of 200 r / min, and then irradiate under a xenon lamp for 0 h to obtain the final product.

[0047] Example 2

[0048] A method for preparing a photosensitive flocculant is to grind urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:7) into a powder in an agate mortar, then place the powder in a polytetrafluoroethylene-lined autoclave and heat it at 120 °C for 1.5 h. Dissolve the obtained yellow-brown product in H 2 O and dialyze (MWCO: 0.5 kDa) for 30 h; the mass ratio of the yellow-brown product to H 2 O is 1:3. Subsequently, centrifuge the solution at a speed of 5000 r / min for 10 min and filter it through a 220 nm filter membrane to obtain a purified c-CNQDs solution.

[0049] Weigh a certain amount of chitosan and dissolve it in 4% HCl by mass. The mass ratio of chitosan to HCl is 1:2. After it is dissolved, adjust the pH to 5.5 and pour it into the c-CNQDs solution to obtain a mixed solution. Additionally, weigh N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), dissolve them in water, and the molar ratio of NHS, EDC, and water is 1:2:10. After NHS and EDC are dissolved, pour them into the above mixed solution, and the molar ratio of chitosan to NHS and EDC is 1:1.5:1.5. Adjust the temperature of the water bath where the round-bottom flask is located to 15 °C, stir mechanically for 7 h at a stirring speed of 250 r / min, and then irradiate under a xenon lamp for 20 min to obtain the final product.

[0050] Example 3

[0051] A method for preparing a photosensitive flocculant is to grind urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:8) into a powder in an agate mortar, then place the powder in a polytetrafluoroethylene-lined autoclave and heat it at 120 °C for 2 h. Dissolve the obtained yellow-brown product in H 2Dialyze in O (MWCO: 2 kDa) for 35 h; the mass ratio of the yellowish-brown product to H 2 The mass ratio of O is 1:3. Subsequently, centrifuge the solution at 6000 r / min for 15 min and filter it through a 450 nm filter membrane to obtain a purified c-CNQDs solution.

[0052] Weigh a certain amount of chitosan and dissolve it in 3% HCl by mass. The mass ratio of chitosan to HCl is 1:4. After it is dissolved, adjust the pH to 6 and pour it into the c-CNQDs solution. In addition, weigh N-hydroxysuccinimide NHS and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EDC and dissolve them in water. The molar ratio of NHS, EDC, and water is 1:2.5:13; after NHS and EDC are dissolved, pour them into the above mixed solution. The molar ratio of chitosan to NHS and EDC is 1:2:2. Adjust the temperature of the water bath where the round-bottom flask is located to 20 °C and stir mechanically for 8 h at a stirring speed of 300 r / min. Then irradiate it under a xenon lamp for 1 h to obtain the final product.

[0053] Example 4

[0054] A method for preparing a photosensitive flocculant, grind urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:9) into powder in an agate mortar, then place the powder in a polytetrafluoroethylene-lined autoclave and heat it at 130 °C for 2.5 h. Dissolve the obtained yellowish-brown product in H 2 Dialyze in O (MWCO: 3.5 kDa) for 40 h; the mass ratio of the yellowish-brown product to H 2 The mass ratio of O is 1:3. Subsequently, centrifuge the solution at 7000 r / min for 20 min and filter it through a 100 nm filter membrane to obtain a purified c-CNQDs solution.

[0055] Weigh a certain amount of chitosan and dissolve it in 2% HCl by mass. The mass ratio of chitosan to HCl is 1:6. After it is dissolved, adjust the pH to 6.5 and pour it into the c-CNQDs solution to obtain a mixed solution. In addition, weigh N-hydroxysuccinimide NHS and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EDC and dissolve them in water. The molar ratio of NHS, EDC, and water is 1:3:15; after NHS and EDC are dissolved, pour them into the above mixed solution. The molar ratio of chitosan to NHS and EDC is 1:2.5:2.5. Adjust the temperature of the water bath where the round-bottom flask is located to 25 °C and stir mechanically for 9 h at a stirring speed of 350 r / min. Then irradiate it under a xenon lamp for 3 h to obtain the final product.

[0056] Example 5

[0057] A method for preparing a photosensitive flocculant, urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:10) are ground into powder in an agate mortar, and then the powder is placed in a polytetrafluoroethylene-lined autoclave and heated at 140 °C for 3 h. The obtained yellow-brown product is dissolved in H 2 O and dialyzed (MWCO: 2 kDa) for 48 h; the mass ratio of the yellow-brown product to H 2 O is 1:3. Subsequently, the solution is centrifuged at 9000 r / min for 10 min and filtered through a 100 nm filter membrane to obtain a purified c-CNQDs solution.

[0058] Weigh a certain amount of chitosan and dissolve it in 4% HCl by mass. The mass ratio of chitosan to HCl is 1:8. After it is dissolved, adjust the pH to 7 and pour it into the c-CNQDs solution to obtain a mixed solution. In addition, weigh N-hydroxysuccinimide NHS and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EDC and dissolve them in water. The molar ratio of NHS, EDC and water is 1:3.5:17; after NHS and EDC are dissolved, pour them into the above mixed solution. The molar ratio of chitosan to NHS and EDC is 1:3:3. Adjust the temperature of the water bath where the round-bottom flask is located to 30 °C, stir mechanically for 10 h, and the stirring speed is 300 r / min. Then irradiate it under a xenon lamp for 5 h to obtain the final product.

[0059] Example 6

[0060] A method for preparing a photosensitive flocculant, urea and sodium citrate (the molar ratio of sodium citrate to urea is 1:11) are ground into powder in an agate mortar, and then the powder is placed in a polytetrafluoroethylene-lined autoclave and heated at 150 °C for 3.5 h. The obtained yellow-brown product is dissolved in H 2 O and dialyzed (MWCO: 3.5 kDa) for 52 h; the mass ratio of the yellow-brown product to H 2 O is 1:3. Subsequently, the solution is centrifuged at 10000 r / min for 5 min and filtered through a 220 nm filter membrane to obtain a purified c-CNQDs solution.

[0061] Weigh a certain amount of chitosan and dissolve it in 5% HCl by mass. The mass ratio of chitosan to HCl is 1:10. After it is dissolved, adjust the pH to 7.5 and pour it into the c-CNQDs solution to obtain a mixed solution. In addition, weigh N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) and dissolve them in water. The molar ratio of NHS, EDC, and water is 1:4:20. After NHS and EDC are dissolved, pour them into the above mixed solution. The molar ratio of chitosan to NHS and EDC is 1:1.5:2.5. Adjust the temperature of the water bath where the round-bottom flask is located to 35 °C, stir mechanically for 8 h at a stirring speed of 250 r / min, and then irradiate under a xenon lamp for 7 h to obtain the final product.

[0062] Example 7

[0063] Application of the photosensitive flocculant in water treatment. The photosensitive flocculants prepared in Examples 1-6 above were respectively made into flocculant mother liquors for water treatment test experiments.

[0064] The test steps for each group of experiments are as follows: Take 7 1-L beakers and prepare simulated polluted wastewater in each beaker; the simulated polluted wastewater is respectively 7.4 mg / L humic acid, 10 mg / L kaolin, 1 μg / L acetamiprid (AAP), 1 μg / L roxithromycin (ROX), 1 μg / L norfloxacin (NOR), 1 μg / L sulfadiazine (SDZ), 1 μg / L diclofenac (DCF), 1 μg / L metaldehyde (MET), 1 μg / L sulfamethoxazole (SMX), 1 μg / L carbendazim (CBZ), 1 μg / L tetracycline (TC), 1 μg / L glyphosate (GPS), 1 μg / L tylosin (TYL); Add 0-60 mg / L of the flocculant mother liquor to each beaker. The concentration of the photosensitive flocculant in the flocculant mother liquor is 5 g / L. Then, perform rapid stirring at 250 r / min for 5 min and slow stirring at 50 r / min for 15 min on a six-stirring coagulation experiment stirrer, and let it stand for sedimentation for 1 h; Take the supernatant, measure the concentration of the remaining humic acid (UV 254 ) in the water body by ultraviolet absorption spectroscopy, measure the remaining turbidity Turbidity in the water body with a turbidimeter, measure the remaining dissolved organic carbon DOC with a total organic carbon analyzer, and measure the concentrations of the remaining acetamiprid AAP, roxithromycin ROX, norfloxacin NOR, sulfadiazine SDZ, diclofenac DCF, metaldehyde MET, sulfamethoxazole SMX, carbendazim CBZ, tetracycline TC, glyphosate GPS, and tylosin TYL in the water body by high performance liquid chromatography-mass spectrometry.

[0065] The photosensitive flocculants of Examples 1-6 for turbidity Turbidity, humic acid (UV 254), the removal results of dissolved organic carbon (DOC), acetamiprid (AAP), roxithromycin (ROX), norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), glyphosate (GPS), and tylosin (TYL) are as follows Figure 2-7 . In Figure 2-7 , the photosensitive flocculant can achieve a maximum removal rate of over 90% for turbidity, humic acid (UV 254 ), dissolved organic carbon (DOC), acetamiprid (AAP), and roxithromycin (ROX). The maximum removal rates for norfloxacin (NOR), sulfadiazine (SDZ), diclofenac (DCF), metaldehyde (MET), sulfamethoxazole (SMX), carbendazim (CBZ), tetracycline (TC), and glyphosate (GPS) can be between 80% and 90%, and the maximum removal rate for tylosin (TYL) can be between 75% and 80%.

[0066] The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A preparation method of a photosensitive flocculant, characterized in that, the specific process conditions are as follows: The first step: Grind urea and sodium citrate into powder in an agate mortar, and then place the powder in a polytetrafluoroethylene-lined autoclave and heat to obtain a yellowish-brown product; Step 2: Dissolve the obtained yellowish-brown product in H 2 O and dialyze to obtain a solution; the mass ratio of the yellowish-brown product to H 2 O is 1:3; The third step: Centrifuge the solution at a speed of 4000 - 10000 r / min and filter through a filter membrane to obtain a purified c-CNQDs solution, which is placed in a round-bottom flask; The fourth step: Weigh chitosan and dissolve it in 1 - 5% mass fraction HCl. The mass ratio of chitosan to HCl is 1:1 - 10. After it is dissolved, adjust the pH and pour it into the purified c-CNQDs solution to obtain a mixed solution; The fifth step: Weigh N-hydroxysuccinimide NHS and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride EDC and dissolve them in water. After NHS and EDC are dissolved, pour them into the above mixed solution; Step 6: Adjust the temperature of the water bath where the round-bottom flask is located to 10 - 35 °C. After mechanical stirring, irradiate under a xenon lamp to obtain the final product, a photosensitive flocculant, with an irradiation intensity of 30 mW / cm 2 .

2. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the first step, the molar ratio of sodium citrate to urea is 1:6 - 11.

3. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the first step, the heating temperature in the polytetrafluoroethylene-lined autoclave is 100 - 150 °C, and the heating time is 1 - 3.5 h.

4. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the second step, the dialysis parameters are MWCO: 0.5 - 3.5 kDa, and the dialysis time is 24 - 52 h.

5. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the third step, the centrifugation time is 5 - 20 min, and the filter pore size of the filter membrane is 100 - 450 nm.

6. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the fourth step, adjust the pH to 5 - 7.

5.

7. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the fifth step, the molar ratio of NHS, EDC and water is 1:1.5 - 4:5 - 20, and the molar ratio of chitosan to NHS and EDC is 1:1 - 3:1 - 3.

8. A preparation method of a photosensitive flocculant according to claim 1, characterized in that: In the sixth step, the mechanical stirring speed is 200 - 350 r / min, the stirring duration is 6 - 10 h, and then irradiate under a xenon lamp to obtain the final product photosensitive flocculant.

9. A preparation method of a photosensitive flocculant according to claim 1, characterized in that, the specific synthesis scheme of the preparation method is as follows: 。 10. Application of a photosensitive flocculant prepared by the preparation method according to any one of claims 1 - 9 as a flocculant mother liquor in water treatment, characterized in that: Take 7 1-L beakers and prepare simulated polluted wastewater in each beaker; the simulated polluted wastewater contains 7.4 mg / L humic acid, 10 mg / L kaolin, 1 μg / L acetamiprid AAP, 1 μg / L roxithromycin ROX, 1 μg / L norfloxacin NOR, 1 μg / L sulfadiazine SDZ, 1 μg / L diclofenac DCF, 1 μg / L metaldehyde MET, 1 μg / L sulfamethoxazole SMX, 1 μg / L carbendazim CBZ, 1 μg / L tetracycline TC, 1 μg / L glyphosate GPS, and 1 μg / L tylosin TYL respectively; add 0 - 60 mg / L of the flocculant mother liquor to each beaker, where the concentration of the photosensitive flocculant in the flocculant mother liquor is 5 g / L, then perform rapid stirring at 250 r / min for 5 min, slow stirring at 50 r / min for 15 min on a six-joint coagulation experiment stirrer, and let it stand for sedimentation for 1 h; Take the supernatant and measure the UV of the remaining humic acid in the water body using ultraviolet absorption spectroscopy 254 concentration, measure the remaining turbidity Turbidity in the water body using a turbidimeter, measure the remaining dissolved organic carbon DOC using a total organic carbon analyzer, and measure the concentrations of the remaining acetamiprid AAP, roxithromycin ROX, norfloxacin NOR, sulfadiazine SDZ, diclofenac DCF, metaldehyde MET, sulfamethoxazole SMX, carbendazim CBZ, tetracycline TC, glyphosate GPS, and tylosin TYL in the water body using high performance liquid chromatography-mass spectrometry.

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