A method for degradation of flame retardant intermediates by UVB / periodate enhanced by trace nitrogen oxides

Abstract

The present application relates to a kind of trace nitrogen oxide reinforced UVB / high iodate degradation flame retardant intermediate method, comprising the following steps: respectively, an appropriate amount of high iodate and ACNHTEMPO are sequentially added into DOPO containing wastewater, the pH of mixed solution is adjusted with phosphate buffer solution, after being fully stirred, UV irradiation is carried out for a period of time, the degradation of organic phosphorus flame retardant intermediate DOPO can be realized.The present application method utilizes potassium periodate under the irradiation of ultraviolet light, activates ACNHTEMPO to speed up electron transfer rate, substantially improves the degradation efficiency of pollutant, and the pH is widely applicable.Solve the defect that most advanced oxidation technology needs to be carried out in acidic conditions;In addition, the present method is simple to operate, uses trace activator, does not produce secondary pollution, can provide new perspective for organic wastewater treatment field.

Description

Technical Field

[0001] The present invention relates to the field of photocatalytic degradation, in particular to the degradation of new pollutants in water treatment. Background Art

[0002] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is an important precursor for the synthesis of flame retardants in textile dyes, luminescent materials, flame retardants, and electronic devices. Electronic devices are now ubiquitous in our daily lives. However, DOPO polymers produce DOPO upon thermal decomposition. Due to DOPO's low vapor pressure and Henry's law constant, it readily migrates into water. my country, a major producer of organophosphorus flame retardants, has over 200 factories nationwide. DOPO, a major flame retardant, produces over 80,000 tons annually. Furthermore, DOPO and its derivatives have been shown to affect neuronal differentiation and neural progenitor cell migration, as well as persistent effects on Daphnia pulex, disrupting the human endocrine system and leading to various abnormalities. Therefore, an effective method for reducing DOPO in surface waters is urgently needed.

[0003] However, traditional water pollution treatment processes based on physical methods and biodegradation principles are mainly used to remove inorganic matter and COD in water, and have extremely low efficiency in removing organic matter, resulting in a large amount of pollutants entering the water environment. However, these difficult-to-degrade pollutants are mostly persistent and bioaccumulative, affecting ecological safety and human health. In recent years, advanced oxidation technology based on periodate (PI) has attracted widespread attention. As a solid oxidant, PI has the advantages of stable chemical properties, easy storage and transportation, and is used preferentially in water treatment processes. PI can be activated to generate HO•, 1 Activation by transition metals or UV light can effectively remove pollutants from water by using reactive oxygen species (ROS) such as O₂ and reactive iodine species (RIS) such as IO₄• and IO₃•. Activation by transition metals or UV light can result in high energy consumption and suboptimal activation performance. Therefore, developing an activator to activate PI that can reduce energy consumption and improve degradation efficiency is crucial.

[0004] 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) was initially used as a spin trapping agent in EPR detection technology to characterize the generation of free radicals. Studies have shown that TEMPO can act as a redox mediator in AOPs to improve the efficiency of electron transfer and can also be oxidized to its oxyammonium cation (TEMPO +), directly degrading pollutants. Furthermore, a series of TEMPO derivatives, TEMPOs, can be easily used in practical water treatment reactors. Therefore, the present invention provides a method for activating PI using UVB (wavelength 305 nm) combined with ACNHTEMPO, which is expected to remove DOPO from polluted water. Summary of the Invention

[0005] The present invention aims to address the deficiencies of the prior art by providing a method for degradation of flame retardant intermediates using trace amounts of nitrogen oxides (ACNHTEMPO) enhanced by UVB / periodate. The method is simple to operate, uses a trace amount of activator, does not generate secondary pollution, and achieves efficient removal of DOPO.

[0006] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A method for degradation of flame retardant intermediates by UVB / periodate enhanced by trace nitrogen oxides comprises the following steps:

[0008] (1) Using phosphate buffer solution, adjust the pH of the water containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to 7;

[0009] (2) Periodate and 4-acetylamino-2,2,6,6-tetramethyl-1-oxapiperidinium tetrafluoroborate (ACNHTEMPO) are added to the water containing DOPO to obtain a mixed solution, which is then placed under UVB light for oxidative decomposition reaction.

[0010] Preferably, the periodate is potassium periodate.

[0011] Preferably, the concentration of the phosphate in the water is 20 mM.

[0012] Preferably, the concentration of periodate in water is 500 μM.

[0013] Preferably, the concentration of ACNHTEMPO in water is 0.1 μM.

[0014] Preferably, the concentration of DOPO in the water containing DOPO is 20 mM.

[0015] Preferably, the stopper is 100 mM Na2S2O3.

[0016] Preferably, the wavelength of the ultraviolet lamp is 305 nm.

[0017] Preferably, the ultraviolet light irradiation time is 5-15 min.

[0018] Preferably, the stirring speed is 100-300 r / min.

[0019] The present application has the advantages of:

[0020] 1、The method has the advantages of stable effect and fast removal speed: using UVB as an auxiliary, combining ACNHTEMPO with potassium periodate greatly improves the removal rate of DOPO.

[0021] 2、The method has the advantages of simple operation and no safety hazards: compared with traditional UVC, UVB is more energy-saving, providing a new perspective for photoactivated advanced oxidation technology.

[0022] 3、The method has the advantages of wide applicability: it can be carried out at room temperature, and solves the defects of oxidizing pollutants under acidic conditions in the current advanced oxidation technology, and has a wide pH application range. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Figure 1 is a degradation curve of DOPO in water in different reaction systems in Example 1;

[0024] Figure 2 Figure 2 is a degradation curve of DOPO in water in different concentrations of ACNHTEMPO in Example 2;

[0025] Figure 3 Figure 3 is the degradation rate of DOPO in water under the conditions of pH 3, 4, 5, 6, 7, 8 and 9 in Example 3;

[0026] Figure 4 Figure 4 is the degradation rate of DOPO in water in different water matrices in Example 4;

[0027] Figure 5 Figure 5 is the degradation rate of DOPO in different types of water by UVB / PI / ACNHTEMPO. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. The described examples are part of the examples of the present application, but not all the examples. The specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0029] The present application provides a method for strengthening UVB / high iodate to degrade flame retardant intermediates containing trace amounts of nitrogen oxides, comprising the following steps:

[0030] (1) Adjust the pH of the DOPO-containing water body to 7 using a phosphate buffer solution;

[0031] (2) continue to add periodate and ACNHTEMPO in the water body containing DOPO to obtain a mixed solution, and place the mixed solution under UVB ultraviolet light to perform an oxidative decomposition reaction.

[0032] Preferably, the periodate is potassium periodate.

[0033] Preferably, the concentration of the phosphate in the water body is 20 mM.

[0034] Preferably, the concentration of the periodate in the water body is 500 μM.

[0035] Preferably, the concentration of the ACNHTEMPO in the water body is 0.1 μM.

[0036] Preferably, the concentration of DOPO in the water body containing DOPO is 20 mM.

[0037] Preferably, the quenching agent is 100 mM Na2S2O3.

[0038] Preferably, the wavelength of the UV ultraviolet lamp is 305 nm.

[0039] Preferably, the illumination time of the ultraviolet light is 5-15 min.

[0040] Preferably, the stirring speed is 100-300 r / min.

[0041] Example 1

[0042] The present embodiment utilizes trace nitrogen oxides to strengthen the process of UVB / periodate degradation of flame retardant intermediates, which is realized by the following steps:

[0043] A DOPO solution is added to a quartz reaction kettle to ensure that the initial concentration C0 thereof is 20 μM, thereby obtaining a water body containing DOPO to be treated; under the premise that the total volume of the system is 100 mL, phosphate buffer solution (a mixed solution of Na2HPO4 and NaH2PO4), ACNHTEMPO, and potassium periodate (PI) are sequentially added to the water body containing DOPO to make the concentrations thereof be 20 mM, 0.1 μM, and 0.5 mM respectively, then the reaction kettle is covered with a quartz plate to prevent water evaporation while allowing ultraviolet penetration, and the mixed system is fully mixed under the action of a magnetic stirrer, thereby obtaining a mixed system. The mixed system is placed under an ultraviolet lamp, and the illumination is started to be recorded as 0 s, and a circulating condensate water system is used to keep the mixed system at a constant temperature of 25℃. During the reaction, samples are taken at fixed reaction time points of 0, 1, 3, 5, 8, 10, and 15 minutes, and finally the solution is immediately transferred to an amber vial containing 0.1 mL of a quenching agent (100 mM, Na2S2O3). The residual concentration of DOPO is analyzed by high performance liquid chromatography (HPLC).

[0044] As a comparative example of Example 1, the procedure of Example 1 was repeated, except that ACNHTEMPO and PI were not added, and only UV light was used to degrade the DOPO wastewater. The degradation effect is shown in Figure 1 .

[0045] As a comparative example of Example 1, the procedure of Example 1 was repeated, except that PI was not added. The degradation effect is shown in Figure 1 .

[0046] As a comparative example of Example 1, the procedure of Example 1 was repeated, except that the mixed system was placed in the dark for reaction. The degradation effect is shown in Figure 1 .

[0047] As a comparative example of Example 1, the procedure of Example 1 was repeated, except that ACNHTEMPO was not added. The degradation effect is shown in Figure 1 .

[0048] As a comparative example of Example 1, the procedure of Example 1 was repeated, except that ACNHTEMPO was replaced by TEMPO. The degradation effect is shown in Figure 1 .

[0049] It can be seen from Figure 1 that the degradation of DOPO can be ignored when using UV light alone to treat the water sample containing DOPO, which excludes the possibility of direct photodegradation of DOPO under UVB. In the UVB / ACNHTEMPO and PI / ACNHTEMPO systems, DOPO is not degraded, indicating that the oxidation ability of PI itself is not sufficient to degrade DOPO. In the UVB / PI system, the removal rate of DOPO is about 60.30% within 15 minutes. It is worth noting that the combination of UV light, PI and ACNHTEMPO greatly improves the degradation of DOPO in aqueous solution, with a degradation rate of 87.70% within 15 minutes. This indicates that PI and ACNHTEMPO have a great degree of synergy under UV light. This can be considered that ACNHTEMPO acts as an electron shuttle under the excitation of UV light, accelerating electron transfer and thus accelerating the generation of active oxygen species and the degradation of DOPO. After the acetylamino group is substituted, ACNHTEMPO shows a higher redox potential (858 mV), which is consistent with the electron-withdrawing effect of the heteroatom substituent. Therefore, compared with TEMPO, ACNHTEMPO is more likely to obtain electrons and convert to ACNHTEMPO + , thereby improving the degradation rate of DOPO.

[0050] Example 2

[0051] In this example, the effect of ACNHTEMPO concentration on the degradation rate of DOPO was investigated.

[0052] Taking Example 1 as a reference, only the concentration of ACNHTEMPO in the mixed solution was changed to 0, 0.05, 0.10, and 0.20 μM. After 15 minutes, the degradation rates of DOPO reached 60.30%, 77.7%, 87.70%, and 80.57%, respectively. Figure 2 shown.

[0053] Example 3

[0054] In this example, the effect of different pH values ​​on the degradation rate of DOPO was investigated.

[0055] Taking Example 1 as a reference, only the pH value of the phosphate buffer solution added to the mixed solution was changed to simulate the degradation of DOPO under the conditions of pH 4, 5, 6, 7, 8, and 9 in the DOPO-containing water. Figure 3 As shown in the figure, the addition of ACNHTEMPO increases the degradation rate of DOPO by UVB / PI at all pH conditions. The addition of ACNHTEMPO increases the degradation rate by 39.30%, 91.05%, 77.57%, 100.00%, 63.54%, and 64.82%, respectively. Furthermore, the DOPO degradation rate peaks at pH 7.

[0056] Example 4

[0057] Various actual water bodies contain a large amount of Cl - 、HCO3 - And natural organic matter. In this example, different Cl - 、HCO3 - And FA (fulvic acid is an important component of natural organic matter) changes the concentration of each ion in the solution, and combines the data to determine the effect of each main component on the degradation of DOPO by UVB / PI / ACNHTEMPO. Figure 4 As shown, FA (<10 mgC·L -1 ), Cl - and HCO3 - The increase in the concentration of water matrix will inhibit the degradation of DOPO in the UVB / PI process to varying degrees, but ACNHTEMPO can promote the degradation of DOPO by the UVB / PI process in water bodies containing these water matrices.

[0058] Example 5

[0059] Example 1 was repeated except that river water (Jiaoxi, NW) was used instead of ultrapure water.

[0060] Example 6

[0061] Example 1 was repeated, except that reservoir water (Liuyang Reservoir, EW) was used instead of ultrapure water.

[0062] like Figure 5 As shown, the UVB / PI / ACNHTEMPO constructed by the present invention can be effectively applied to the pollution treatment of various actual water bodies, further indicating that UVB / PI / ACNHTEMPO has good application prospects.

[0063] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for degradation of flame retardant intermediates by UVB / periodate enhanced by trace nitrogen oxides, characterized in that: The following steps are involved: (1) Using phosphate buffer solution, adjust the pH of the water containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to 7; (2) Periodate and 4-acetylamino-2,2,6,6-tetramethyl-1-oxapiperidinium tetrafluoroborate (ACNHTEMPO) are added to water containing DOPO to obtain a mixed solution, which is then placed under UVB light for oxidative decomposition reaction.

2. The method of claim 1, wherein the method comprises: The periodate is potassium periodate.

3. The method of claim 1, wherein the method comprises: The concentration of the phosphate in the water body is 20 mM.

4. The method of claim 1, wherein the method comprises: The concentration of periodate in water is 500 μM.

5. The method of claim 1, wherein the method comprises: The concentration of ACNHTEMPO in water is 0.1 μM.

6. The method of claim 1, wherein the method comprises: The concentration of DOPO in water is 20 mM.

7. The method of claim 1, wherein the method comprises: The wavelength of the ultraviolet rays is 305 nm.

8. The method of claim 1, wherein the method comprises: The UV exposure time is 5-15 min.

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