A method for in-situ photocatalytic oxidation of ammonia nitrogen in water by loading alpha-MnO2 on optical fiber

Abstract

The application discloses a method for in-situ photocatalytic oxidation of ammonia nitrogen in water by loading alpha-MnO2 on optical fibers, and comprises the following steps: S1, preparation of the optical fibers loaded with alpha-MnO2; S2, removal of ammonia nitrogen in water; the alpha-MnO2 catalyst is loaded on the optical fibers, so that the ammonia nitrogen in water can be efficiently removed; the selectivity of the reaction product to nitrogen is about 90%, no nitrite is generated, the method is environment-friendly, the utilization efficiency of light energy is high, and the reaction product can be recycled and used, and the performance is stable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysis technology, in particular to a method for in-situ photocatalytic oxidation of ammonia nitrogen in water by α-MnO2-loaded optical fiber. BACKGROUND

[0002] The existing photocatalysts include TiO2, g-C3N4, Ag3PO4 and MnO2, and MnO2 has been proved to have certain thermal catalytic and photocatalytic activity, and α, β and γ three crystal forms of MnO2 can all have catalytic effect on the thermal decomposition of ozone, among which the catalytic effect of α-MnO2 is the best, and the catalytic effect of β-MnO2 and γ-MnO2 increases with the increase of temperature; however, it is found in the current research that the above-mentioned photocatalytic reaction has many shortcomings to be solved, for example, the removal rate of ammonia nitrogen by the catalyst and the selectivity of the product nitrogen gas cannot be achieved at the same time, the reaction product may contain nitrite, which is not friendly to the environment, the utilization efficiency of light energy is low, and the catalyst is free in the reaction system, which is difficult to recover or recycle after the reaction.

[0003] Due to the light transmission method from the inside to the outside of the optical fiber, the scattering and shielding of light by the photocatalyst and other impurities in water can be effectively avoided, and the research on the combination of light and catalyst before photocatalytic water pollutants is gradually increasing; however, the coating of a dense photocatalyst coating with a light shielding effect on the surface of the optical fiber will cause a large amount of light to be refracted out of the optical fiber, and only a small part of the refracted light is used to excite the photocatalyst, and most of the refracted light penetrates through the photocatalyst coating, so that it is not utilized. SUMMARY

[0004] To solve the above problems, the present application provides a method for in-situ photocatalytic oxidation of ammonia nitrogen in water by α-MnO2-loaded optical fiber.

[0005] The technical scheme of the present application is as follows: a method for in-situ photocatalytic oxidation of ammonia nitrogen in water by α-MnO2-loaded optical fiber, comprising the following steps:

[0006] S1, preparation of α-MnO2-loaded optical fiber:

[0007] S1-1, synthesis of α-MnO2

[0008] KMnO4 and (NH4)2C2O4·H2O are added to deionized water in a ratio of 20-30 mmol: 10 mmol: 60-70 mL, and after stirring until the solids are completely dissolved, a mixed solution is obtained, the mixed solution is placed in a reaction kettle lined with Teflon, and is kept at a constant temperature of 140-180℃ for 20-24h, and then washed with deionized water and dried at 80-105℃ for 10-12h; α-MnO2 is obtained;

[0009] S1-2, loading α-MnO2 on the optical fiber

[0010] Take the optical fiber of the polymer material, remove the PVDF layer on the surface of one end of the optical fiber, electrically polish the inner core surface of PMMA for 10s, and then perform surface treatment; the other end of the optical fiber is not treated; then α-MnO2 is added to the organic solvent in a proportion of 500mg:25ml, and the polished end of the optical fiber is also completely immersed in the organic solvent for loading, ultrasonic treatment is performed at 50-60℃, after the treatment is completed, drying is performed at 60℃ for 1h, and the optical fiber loaded with α-MnO2 is obtained;

[0011] S2, removing ammonia nitrogen in water

[0012] The weight increment of the optical fiber before and after loading in step S1-2 is taken as the loading amount of α-MnO2; under full-spectrum light illumination with an optical power density of 400-600mW / cm 2 , the end of the optical fiber loaded with α-MnO2 is placed in water to in-situ photocatalytically oxidize ammonia nitrogen in water.

[0013] Description: Through the above method, the light transmission from the inside to the outside of the optical fiber can be utilized, the scattering and shielding of light by the photocatalyst and other impurities in water can be effectively avoided, and by loading α-MnO2 on the surface, ammonia nitrogen pollution in water can be efficiently catalyzed, so that the removal rate of ammonia nitrogen can be ensured and the selectivity of the product nitrogen can be ensured, the product does not pollute the water body, the light energy utilization efficiency is high, the product is easy to recycle or circulate, and the purpose of energy saving is achieved.

[0014] Further, the organic solvent is DMSO.

[0015] Description: Since DMSO has good solubility and penetration ability, it is a better solvent, and the loading of α-MnO2 can play a certain promoting role.

[0016] Further, the organic solvent is a mixed solvent obtained by mixing DMF and acetone in a mass ratio of 1:1.

[0017] Description: By using the above mixed solvent, the solubility range can be expanded, good wettability can be provided in coating and coating applications, and the solution can be more easily covered and penetrated to the surface. Compared with existing organic solvents, dimethyl sulfide and acetone both have lower toxicity and lower environmental impact, and are more environmentally friendly.

[0018] Further, in step S1-2, the ultrasonic treatment is: staying in the organic solvent under ultrasonic frequency of 35 kHz for 5 s under normal pressure, then taking out the optical fiber and placing it in a light-free environment, and drying and standing for 30 s under a pressure of 300 kPa; the above ultrasonic staying and drying and standing steps are alternately performed until the total ultrasonic staying time is 30 s.

[0019] It is explained that, through the setting of the above ultrasonic treatment steps, through the alternation of ultrasonic adsorption and pressurized adsorption, the α-MnO2 can be more easily and firmly loaded on the surface of the optical fiber, the loading effect of the two is enhanced, and the catalytic effect is more optimal, and the α-MnO2 is not easy to fall off.

[0020] Further, in the process of ultrasonic treatment, the ultrasonic frequency is gradually reduced at a rate of 2-2.5 kHz / time, and the pressure is gradually increased at a rate of 3-5 kPa / time, until completion.

[0021] It is explained that, through the relative change of the above ultrasonic frequency and pressure, the adsorption effect can be further enhanced, by reducing the ultrasonic frequency, some α-MnO2 adsorbed on the surface of the optical fiber can be avoided from being mixed into the solvent again under ultrasonic conditions, and by gradually increasing the pressure, the same effect can be achieved, and through the opposite change of the two, the loading effect is better.

[0022] Further, in step S1-2, the surface treatment is: placing at a temperature of 80°C for 30 min, and the ultrasonic treatment is: staying in the organic solvent under ultrasonic frequency of 35 kHz for 30 s.

[0023] It is explained that, through the heating and placing treatment of the surface of the optical fiber, the surface of the optical fiber can be activated, and it is more easy to combine with the photocatalyst in the solvent in the ultrasonic treatment.

[0024] Further, in step S1-2, the surface treatment is: coating the powdered porous organic polymer POPs on the polished surface of the optical fiber, and then drying it.

[0025] It is explained that, through the coating of the above porous organic polymer POPs, a large amount of light can be refracted out of the optical fiber by the α-MnO2 coating, only a small part of the refracted light is used to excite the photocatalyst, resulting in insufficient utilization of light; the porous organic polymer POPs is an important part of the porous material field, which has the advantages of designability, easy functionalization, high specific surface area, low density, excellent stability, etc., can make the light in the optical fiber propagate in the form of evanescent wave on the surface of the optical fiber, improve the photocatalytic efficiency, and the porous structure ensures the efficient transfer of pollutants in the α-MnO2 catalyst, thereby enhancing the catalytic effect of the catalyst.

[0026] Further, the porous organic polymer POPs has a particle size of 0.5-2 μm.

[0027] Description: The particle size is set to be better for the connection of the photocatalyst and the surface of the optical fiber and the loading function of the photocatalyst.

[0028] Further, the preparation method of the porous organic polymer POPs is as follows:

[0029] 1,4-dibromo-2-butynyl and bromobenzene are added into methanol in a ratio of 1.5-1.7 mol:1 mol:10 ml, 5% of copper chloride and 3% of potassium carbonate by mass fraction of bromobenzene are added, stirring is carried out at 80-90 °C for 0.8-1 h, then the obtained product is washed with N,N-dimethylformamide and anhydrous tetrahydrofuran in sequence, drying is carried out at 80 °C for 5-6 h, the POPs is obtained, then grinding and screening are carried out, and the porous organic polymer POPs with a particle size of 0.5-2 μm is obtained.

[0030] Description: The porous organic polymer POPs prepared by the above method has high specific surface area and strong adsorption and catalytic capacity, 1,4-dibromo-2-butynyl and bromobenzene have nucleophilic substitution groups and high chemical stability, the porous organic polymer POPs prepared by polymerization has better performance, and is suitable for loading of the catalyst in the present research.

[0031] Further, the coating method is as follows: powder electrostatic spraying is used for spraying, the spraying is carried out under electrostatic high voltage of 40-50 kV, electrostatic current of 10-15 μA and atomization pressure of 0.30-0.45 MPa, until the coating thickness is 5-6 μm; after the spraying is completed, the coated surface is dried and placed at 90-95 °C for 2-3 h.

[0032] Description: By the above coating method, the porous organic polymer POPs can be firmly coated on the surface of the inner core of the optical fiber PMMA, and the two can enhance the surface adsorption capacity while well retaining the respective characteristics, and the influence on light transmission is small; at the same time, the setting of the parameters can ensure the powdering effect, and too high voltage and current can easily cause powder rebound and edge pitting, discharge breakdown of the powder coating; and too low powdering rate is low.

[0033] The present application has the following beneficial effects:

[0034] (1) The application can efficiently remove ammonia nitrogen in water by loading the alpha-MnO2 catalyst on the optical fiber; the selectivity of the reaction product to nitrogen is about 90%, no nitrite is produced, it is environmentally friendly, the light energy utilization efficiency is high, it can be recycled after reaction, the performance is stable, the light transmission from the inside to the outside of the optical fiber can be used to effectively avoid the scattering and shielding of light by the photocatalyst and other impurities in the water, and by loading alpha-MnO2 on the surface, the ammonia nitrogen pollution in the water body can be efficiently catalyzed, so that the removal rate of ammonia nitrogen can be ensured, the selectivity of the product to nitrogen can be ensured, the product does not pollute the water body, the light energy utilization efficiency is high, and the product is easy to recycle or recycle, so that the purpose of saving energy is achieved.

[0035] (2) The application can expand the solubility range by using mixed solvents, provide good wettability in coating and coating applications, make the solution easier to cover and penetrate the surface, and compared with existing organic solvents, dimethyl sulfide and acetone have lower toxicity and lower environmental impact, and are more environmentally friendly. The setting of the ultrasonic treatment step enables alpha-MnO2 to be more easily and firmly loaded on the surface of the optical fiber through ultrasonic adsorption and pressurized adsorption, thereby enhancing the loading effect of the two, and further improving the catalytic effect of alpha-MnO2.

[0036] (3) The application can avoid the large amount of light refracted out of the optical fiber caused by the alpha-MnO2 coating, only a small part of the refracted light is used to excite the photocatalyst, resulting in insufficient utilization of light; the porous organic polymer POPs is an important part of the porous material field, which has the advantages of designability, easy functionalization, high specific surface area, low density, excellent stability, etc., can make the light in the optical fiber propagate in the form of evanescent wave on the surface of the optical fiber, improve the photocatalytic efficiency, and the porous structure ensures efficient transmission of pollutants in the alpha-MnO2 catalyst, thereby enhancing the catalytic effect of the catalyst; the surface of the PMMA inner core has a uniform refractive index, which ensures stable transmission of the light signal along the path of the optical fiber and maximizes the diffusion and attenuation of the signal. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the alpha-MnO2 loaded optical fiber prepared in Example 1 of the application;

[0038] Figure 2 is a data graph of the ammonia nitrogen conversion rate of Example 1 of the application and Control Group 1 and Control Group 2;

[0039] Figure 3 is a data graph of the ammonia nitrogen conversion rate at different pH values in Example 1 of the application;

[0040] Figure 4is a data graph of ammonia nitrogen conversion rate of different initial ammonia nitrogen concentrations in Example 1 of the present application;

[0041] Figure 5 is a data graph of ammonia nitrogen conversion rate of different photocatalytic cycle times in Example 1 of the present application;

[0042] Figure 6 is a data graph of ammonia nitrogen conversion rate of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0043] The present application will be further described in conjunction with specific embodiments to better reflect the advantages of the present application.

[0044] Example 1:

[0045] A method for in-situ photocatalytic oxidation of ammonia nitrogen in water by loading α-MnO2 optical fiber, comprising the following steps:

[0046] S1, preparation of α-MnO2 loaded optical fiber:

[0047] S1-1, synthesis of α-MnO2

[0048] KMnO4 and (NH4)2C2O4·H2O were added to deionized water in a ratio of 25 mmol: 10 mmol: 65 mL, and after stirring until the solids were completely dissolved, a mixed solution was obtained. The mixed solution was placed in a Teflon-lined reaction kettle, and reacted at 160°C for 22h under constant temperature. After washing with deionized water, it was dried at 90°C for 11h; α-MnO2 was obtained.

[0049] S1-2, loading α-MnO2 on optical fiber

[0050] Take the optical fiber of the polymer material, remove the PVDF layer on one end of the optical fiber, electrically polish the PMMA inner core surface for 10s, and then perform surface treatment, which is: placing at 80°C for 30min; the other end of the optical fiber is not treated; then α-MnO2 is added to the organic solvent in a ratio of 500mg:25ml, and the polished end of the optical fiber is also completely immersed in the organic solvent for loading, and ultrasonic treatment is performed at 55°C, which is: 30s in the organic solvent under an ultrasonic frequency of 35kHz; then, drying is performed at 60°C for 1h to obtain α-MnO2 loaded optical fiber; the organic solvent is DMSO;

[0051] S2, removing ammonia nitrogen in water

[0052] The weight increment of the optical fiber before and after loading in step S1-2 is used as the α-MnO2 loading amount; under a light power density of 450mW / cm 2The α-MnO2 is loaded on one end of the optical fiber, and the other end is put into the water body under the full spectrum light, and the ammonia nitrogen in the water is in-situ photocatalytic oxidized with the α-MnO2 dosage of 0.1 g / L.

[0053] Example 2

[0054] The difference between this example and example 1 is that the raw material components for synthesizing α-MnO2 are different, and KMnO4 and (NH4)2C2O4·H2O are mixed in deionized water in a ratio of 20 mmol: 10 mmol: 70 mL.

[0055] Example 3

[0056] The difference between this example and example 1 is that the raw material components for synthesizing α-MnO2 are different, and KMnO4 and (NH4)2C2O4·H2O are mixed in deionized water in a ratio of 30 mmol: 10 mmol: 60 mL.

[0057] Example 4

[0058] The difference between this example and example 1 is that the time and temperature parameters for synthesizing α-MnO2 are different, and the reaction kettle with Teflon lining is placed at 140°C for 24 h, then washed with deionized water, and dried at 105°C for 10 h; α-MnO2 is obtained.

[0059] Example 5

[0060] The difference between this example and example 1 is that the time and temperature parameters for synthesizing α-MnO2 are different, and the reaction kettle with Teflon lining is placed at 180°C for 20 h, then washed with deionized water, and dried at 80°C for 12 h; α-MnO2 is obtained.

[0061] Example 6

[0062] The difference between this example and example 1 is that the temperature of ultrasonic treatment in the loading process is different, and the ultrasonic treatment is carried out at 50°C.

[0063] Example 7

[0064] The difference between this example and example 1 is that the temperature of ultrasonic treatment in the loading process is different, and the ultrasonic treatment is carried out at 60°C.

[0065] Example 8

[0066] The difference between this example and example 1 is that the organic solvent is a mixed solvent obtained by mixing DMF and acetone in a mass ratio of 1:1.

[0067] Example 9

[0068] The difference between this embodiment and embodiment 1 is that the organic solvent is kept under ultrasonic frequency of 35 kHz for 5 s under normal pressure, and then the optical fiber is taken out and placed in a light-free environment, and the pressure is dried and placed for 30 s under 300 kPa; the above-mentioned ultrasonic residence and drying and placing steps are alternately carried out until the total ultrasonic residence time is 30 s.

[0069] Embodiment 10

[0070] The difference between this embodiment and embodiment 9 is that the ultrasonic treatment method is different, and in step S1-2, the ultrasonic treatment is: during the ultrasonic treatment, the ultrasonic frequency is reduced by 2.1 kHz / time, and the pressure is increased by 4 kPa / time, until completion.

[0071] Embodiment 11

[0072] The difference between this embodiment and embodiment 9 is that the ultrasonic treatment method is different, and in step S1-2, the ultrasonic treatment is: during the ultrasonic treatment, the ultrasonic frequency is reduced by 2.5 kHz / time, and the pressure is increased by 3 kPa / time, until completion.

[0073] Embodiment 12

[0074] The difference between this embodiment and embodiment 9 is that the ultrasonic treatment method is different, and in step S1-2, the ultrasonic treatment is: during the ultrasonic treatment, the ultrasonic frequency is reduced by 2 kHz / time, and the pressure is increased by 5 kPa / time, until completion.

[0075] Embodiment 13

[0076] The difference between this embodiment and embodiment 1 is that the power density of the light is different, and in step S2, the light power density is 400 mW / cm 2 Full spectrum light.

[0077] Embodiment 14

[0078] The difference between this embodiment and embodiment 1 is that the power density of the light is different, and in step S2, the light power density is 400 mW / cm 2 Full spectrum light.

[0079] Embodiment 15

[0080] The difference between this embodiment and embodiment 1 is that the dosage of α-MnO2 is different, and in step S2, the dosage of α-MnO2 is 0.5 g / L.

[0081] Embodiment 16

[0082] The difference between this embodiment and embodiment 1 is that the adding amount of α-MnO2 is different, and in step S2, the adding amount of α-MnO2 is 0.05 g / L.

[0083] Embodiment 17

[0084] The difference between this embodiment and embodiment 1 is that the surface treatment is different, and in step S1-2, the surface treatment is that the powdered porous organic polymer POPs is attached to the surface of the polished optical fiber, and then it is dried and placed at 92℃ for 2.5h.

[0085] The preparation method of the porous organic polymer POPs is that 1,4-dibromo-2-butynyl and bromobenzene are added to methanol in a ratio of 1.6mol:1mol:10ml, 5% of copper chloride and 3% of potassium carbonate by mass fraction of bromobenzene are added, stirring at 85℃ for 0.9h, and then the obtained product is washed with N,N-dimethylformamide and anhydrous tetrahydrofuran in sequence, dried at 80℃ for 5.5h to obtain POPs, and then ground and screened to obtain the porous organic polymer POPs with a particle size of 0.5-2μm.

[0086] The attachment method is that powder electrostatic spraying is used for spraying, and the spraying is carried out at a static high voltage of 45kV, a static current of 14μA, and an atomization pressure of 0.40MPa until the coating thickness is 5-6μm.

[0087] Embodiment 18

[0088] The difference between this embodiment and embodiment 17 is that the raw material components for preparing the porous organic polymer POPs are different, and 1,4-dibromo-2-butynyl and bromobenzene are added to methanol in a ratio of 1.5mol:1mol:10ml.

[0089] Embodiment 19

[0090] The difference between this embodiment and embodiment 17 is that the raw material components for preparing the porous organic polymer POPs are different, and 1,4-dibromo-2-butynyl and bromobenzene are added to methanol in a ratio of 1.7mol:1mol:10ml.

[0091] Embodiment 20

[0092] The difference between this embodiment and embodiment 17 is that the temperature and time parameters are different, 5% of copper chloride and 3% of potassium carbonate by mass fraction of bromobenzene are added, stirring at 90℃ for 0.8h, and then the obtained product is washed with N,N-dimethylformamide and anhydrous tetrahydrofuran in sequence, dried at 80℃ for 6h to obtain POPs.

[0093] Embodiment 21

[0094] The difference between this embodiment and embodiment 17 is that the temperature and time parameters are different, and 5% of copper chloride and 3% of potassium carbonate by mass of bromobenzene are added, stirring at 80°C for 1h, then the obtained product is washed with N, N-dimethylformamide, anhydrous tetrahydrofuran, and dried at 80°C for 5h to obtain POPs.

[0095] Example 22

[0096] The difference between this embodiment and embodiment 17 is that the coating method parameters are different, and the spraying is carried out at an electrostatic high voltage of 40kV, an electrostatic current of 10μA, and an atomization pressure of 0.30MPa, until the coating thickness is 5-6μm.

[0097] Example 23

[0098] The difference between this embodiment and embodiment 17 is that the coating method parameters are different, and the spraying is carried out at an electrostatic high voltage of 50kV, an electrostatic current of 15μA, and an atomization pressure of 0.45MPa, until the coating thickness is 5-6μm.

[0099] Experimental example

[0100] I. The α-MnO2-loaded optical fiber obtained in example 1 is subjected to a control test, a test for exploring the influence of pH on the removal rate of ammonia nitrogen, a test for exploring the influence of initial ammonia nitrogen concentration on the removal rate, a test for exploring the influence of cycle number on the removal rate, and a product selectivity test, and the performance of the α-MnO2-loaded optical fiber is comprehensively tested, and the results are shown in Figures 2 to 5 Figure 1 The optical fiber 1 is an original optical fiber, the optical fiber 2 is the optical fiber after the surface treatment in step S1-2, and the optical fiber 3 is the obtained α-MnO2-loaded optical fiber;

[0101] 1. As shown in Figure 2 , under full-spectrum light irradiation with an initial concentration of 5ppm NH4 + and a light power density of 450mW / cm 2 , the catalyst dosage is 0.1g / L α-MnO2, which can remove 88% of NH4 + in 2h;

[0102] Control example 1: the treatment in example 1 is carried out in a dark environment; control example 2: the optical fiber without α-MnO2 is used to carry out the catalytic oxidation treatment in example 1; it can be found that the ammonia nitrogen conversion rate of control example 1 and control example 2 is very low; it is proved that the method in example 1 is effective;

[0103] 2. As shown in Figure 3 , with the increase of pH, the performance of the α-MnO2-loaded optical fiber catalyst gradually improves; but when pH=9, the potassium periodate spectrophotometric method (GB11906-89) is used to detect Mn 2+ ​The dissolution of the catalyst is 5% of the catalyst dosage, so it can be concluded that higher pH will result in more catalyst loss, and the pH of 5.5 is selected as the normal test condition;

[0104] 3. As shown in Figure 4 , with the increase of initial ammonia nitrogen concentration, the ammonia nitrogen removal rate shows a downward trend, and the ammonia nitrogen concentration in the actual polluted water body generally does not exceed 40 ppm, so the initial concentration c0=5 ppm is selected as the normal test condition;

[0105] 4. As shown in Figure 5 , with the increase of the number of cycles, the removal rate starts to decrease after the third cycle, and the removal rate of the fifth cycle is reduced by 5% compared with the first cycle, so it can be concluded that the α-MnO2-loaded optical fiber is a stable catalyst;

[0106] 5. The NO3 - , NO2 - in the product is detected by ion chromatograph ICS-1100, and the remaining reactant NH4 + is detected by Nash reagent spectrophotometry (HJ 535-2009); the results show that the product after reaction does not contain NO2 - , indicating that the reaction catalyzed by the α-MnO2-loaded optical fiber is environmentally friendly; about 5% of NH4 + will remain after the reaction, and about 5% of NO3 - will be produced, and the remaining product is N2, that is, the selectivity of the reaction product catalyzed by α-MnO2 to N2 is about 90%, and the reaction catalyzed by the α-MnO2-loaded optical fiber catalyst meets the requirements of high efficiency and high selectivity to N2 at the same time;

[0107] 6. As shown in Figure 6 , under the same conditions, α-MnO2 powder is directly dispersed in the reaction system as a comparison; the performance of Example 1 is improved by about 5%, indicating that the α-MnO2-loaded optical fiber catalyst has better effect;

[0108] II. In-situ photocatalytic oxidation test of ammonia nitrogen in water by Examples 1-23, test time 2h, test results as follows:

[0109] 1. Explore the influence of parameters in the synthesis of α-MnO2 on photocatalytic oxidation;

[0110] Take Example 1, Example 2, and Example 3, Example 4, and Example 5 for comparison, as shown in Table 1;

[0111] Table 1 Influence of parameters in the synthesis of α-MnO2 on photocatalytic oxidation

[0112]

[0113]

[0114] From Table 1, it can be found that, compared with Comparative Example 1, Example 2 and Example 3, the component allocation ratio in Example 1 is optimal, and compared with Comparative Example 1, Example 5 and Example 4, the time and temperature parameters of Example 1 are optimal.

[0115] 2. Explore the influence of parameters in the loading process of α-MnO2 on photocatalytic oxidation;

[0116] Comparative Example 1: α-MnO2 is directly added into the water body to perform the photocatalytic oxidation step of step S2;

[0117] Comparative Example 1, Examples 6-12 are taken for comparison, as shown in Table 2;

[0118] Table 2 Influence of parameters in the loading process of α-MnO2 on photocatalytic oxidation

[0119]

[0120]

[0121] From Table 2, it can be found that, compared with Comparative Example 1, Example 6 and Example 7, the temperature of ultrasonic treatment in Example 1 is more preferred;

[0122] Comparative Example 1, Example 8, it can be found that the mixed solvent of Example 8 is more preferred;

[0123] Comparative Example 1, Example 9, it can be found that the ultrasonic treatment method of Example 9 is more preferred, and the ultrasonic adsorption and pressurized adsorption of Example 9 are alternately performed, so that α-MnO2 can be more easily and firmly loaded on the surface of the optical fiber, thereby enhancing the catalytic effect;

[0124] Comparative Example 9, Example 10, it can be found that the change mode of ultrasonic frequency and pressure of Example 10 is more preferred;

[0125] Comparative Example 10, Example 11 and Example 12, it can be found that the change rate of ultrasonic frequency and pressure of Example 10 is more preferred.

[0126] 3. Explore the influence of parameters in the photocatalytic oxidation process;

[0127] Comparative Example 1, Examples 13-16 are taken for comparison, as shown in Table 3;

[0128] Table 3 Influence of parameters in the photocatalytic oxidation process

[0129] Parameter % conversion of ammonia nitrogen Example 1 88 Example 13 85 Example 14 86 Example 15 86 Example 16 87

[0130] From Table 3, it can be found that, compared with Comparative Example 1, Example 13 and Example 14, the light power density of Example 1 is more preferred, and compared with Comparative Example 1, Example 15 and Example 16, the α-MnO2 dosage of Example 1 is more preferred.

[0131] 4. Explore the influence of surface treatment method on photocatalytic oxidation results;

[0132] Comparative Example 2: zeolite molecular sieve with a particle size of 0.5-2 μm is used instead of porous organic polymer POPs, and the rest of the treatment is the same as Example 1;

[0133] Example 1, Examples 17-23 and Comparative Example 2 are compared, as shown in Table 4.

[0134] Table 4 Influence of surface treatment method on photocatalytic oxidation results

[0135] Parameter % conversion of ammonia nitrogen Example 1 88 Example 17 92 Example 18 90 Example 19 91 Example 20 91 Example 21 90 Example 22 90 Example 23 89 Comparative Example 2 Comparative Example 1 78

[0136] From Table 4, it can be found that, compared with Comparative Example 1 and Example 17, the surface treatment method of Example 17 can enhance the photocatalytic oxidation and improve the conversion rate of ammonia nitrogen;

[0137] Comparing Comparative Example 17 and Comparative Example 2, it can be found that the porous material of zeolite molecular sieve is better than that of porous organic polymer POPs; comparing Comparative Example 17, Example 18 and Example 19, it can be found that the preparation raw material components of porous organic polymer POPs of Example 17 are more preferred; comparing Comparative Example 17, Example 20 and Example 21, it can be found that the temperature and time parameters of Example 17 are more preferred; and comparing Comparative Example 17, Example 22 and Example 23, it can be found that the coating parameters of Example 17 are more preferred.

Claims

1. A method for in-situ photocatalytic oxidation of ammonia nitrogen in water by loading α-MnO2 on optical fiber, characterized in that, The method comprises the following steps: S1, preparation of optical fiber loaded with α-MnO2; S1-1, synthesis of α-MnO2 KMnO4 and (NH4)2C2O4·H2O are mixed in deionized water at a ratio of 20-30 mmol: 10 mmol: 60-70 mL, and after stirring until the solids are completely dissolved, a mixed solution is obtained. The mixed solution is placed in a Teflon-lined reaction kettle, and the temperature is kept constant at 140-180°C for 20-24 hours. After washing with deionized water, the product is dried at 80-105°C for 10-12 hours. The product is α-MnO2; S1-2, loading of α-MnO2 on optical fiber An optical fiber of a polymer material is taken, the PVDF layer on one end of the optical fiber is removed, the PMMA inner core surface is electrically polished for 10 seconds, and then surface treatment is performed. The other end of the optical fiber is not treated. Then α-MnO2 is added to an organic solvent at a ratio of 500 mg: 25 ml, and the polished end of the optical fiber is also completely immersed in the organic solvent for loading. Ultrasonic treatment is performed at 50-60°C. After the treatment is completed, drying is performed at 60°C for 1 hour, and the optical fiber loaded with α-MnO2 is obtained. The ultrasonic treatment is as follows: the optical fiber is kept in the organic solvent at an ultrasonic frequency of 35 kHz for 5 seconds under normal pressure, and then taken out and placed in a light-free environment. The pressure is dried and kept at 300 kPa for 30 seconds. The above ultrasonic keeping and drying keeping steps are alternately performed until the total ultrasonic keeping time is 30 seconds. The surface treatment is that a powdery porous organic polymer POPs is attached to the surface of the polished optical fiber, and then dried. S2, removal of ammonia nitrogen in water The weight increment of the optical fiber before and after step S1-2 is taken as the loading amount of α-MnO2; under the full-spectrum light with the optical power density of 400-600 mW / cm 2 2, the optical fiber loaded with α-MnO2 is put into the water body at one end, and the ammonia nitrogen in the water is in-situ photocatalytic oxidized.

2. The method for in-situ photocatalytic oxidation of ammonia in water by using α-MnO2 loaded optical fiber according to claim 1, characterized in that, The organic solvent is DMSO.

3. The method for in-situ photocatalytic oxidation of ammonia in water by using α-MnO2 loaded optical fiber according to claim 1, characterized in that, The organic solvent is a mixed solvent obtained by mixing DMF and acetone at a mass ratio of 1:

1.

4. The method for in-situ photocatalytic oxidation of ammonia in water by using α-MnO2 loaded optical fiber according to claim 1, characterized in that, During the ultrasonic treatment, the ultrasonic frequency is gradually reduced at a speed of 2-2.5 kHz / time, and the pressure is gradually increased at a speed of 3-5 kPa / time until completion.

5. The method for in-situ photocatalytic oxidation of ammonia nitrogen in water using an α-MnO2-loaded optical fiber according to claim 1, wherein: The particle size of the porous organic polymer POPs is 0.5-2 μm.

6. The method for in-situ photocatalytic oxidation of ammonia in water by using α-MnO2 loaded optical fiber according to claim 1, characterized in that, The preparation method of the porous organic polymer POPs is as follows: 1,4-dibromo-2-butynyl and bromobenzene are added to methanol at a ratio of 1.5-1.7 mol: 1 mol: 10 ml. Copper chloride accounting for 5% of the mass fraction of bromobenzene and 3% of potassium carbonate are added. The mixture is stirred at 80-90°C for 0.8-1 hour. The obtained product is then washed with N, N-dimethylformamide and anhydrous tetrahydrofuran in sequence, and dried at 80°C for 5-6 hours to obtain POPs. The POPs are then ground and screened to obtain a porous organic polymer POPs with a particle size of 0.5-2 μm.

7. The method for in-situ photocatalytic oxidation of ammonia in water by using α-MnO2 loaded optical fiber according to claim 1, characterized in that, The attachment method is as follows: powder electrostatic spraying is used for spraying at a static high voltage of 40-50 kV, a static current of 10-15 μA, and an atomization pressure of 0.30-0.45 MPa. The coating thickness is 5-6 μm. After spraying is completed, drying is performed at 90-95°C for 2-3 hours.

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