A method for degrading organic pollutants in water by redox mediator enhanced system

Abstract

A method for degrading organic pollutants in water by using a redox mediator-enhanced system belongs to the field of water treatment technology. The purpose of the present invention is to overcome the shortcomings of the iron / persulfate system and the traditional Fenton / Fenton-like technology. Method: Hydrogen peroxide or persulfate, a redox mediator and an iron salt are sequentially added to the water to be treated containing organic pollutants at room temperature, and the organic pollutants in the water are reacted with the organic pollutants in the water to complete reaction under stirring conditions. The present invention introduces a redox mediator, which can effectively reduce Fe(III) in the Fenton / Fenton-like system to Fe(II), thereby accelerating the Fe(III) / Fe(II) cycle and improving the removal efficiency of organic pollutants; the present invention introduces a redox mediator, which can effectively reduce Fe(III) in the iron / persulfate system to Fe(II), accelerate the Fe(III) / Fe(II) cycle, and greatly improve the efficiency of the iron / persulfate system in degrading organic pollutants.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for degrading organic pollutants in water by a redox mediator enhanced system. Background Art

[0002] Water pollution, especially organic pollution, poses a huge challenge to the ecological environment and human water safety. Conventional water treatment processes have a certain effect on the removal of organic pollutants in water, but the removal effect is relatively poor, generally only a few percent can be removed. Chemical oxidation is an effective method to control organic pollution in water. Chemical oxidation using iron salts to activate hydrogen peroxide (Fenton / Fenton-like technology) or persulfate can produce hydroxyl radicals (HO • ) or sulfate radical (SO4 •- ) and intermediate active metals (Fe(IV)) and other highly active oxidizing species, thereby achieving deep degradation and removal of organic pollutants in water. Its significant purification effect, mild reaction conditions, low cost and environmental friendliness have made this method widely concerned by scholars.

[0003] Traditional Fenton / Fenton-like technologies and iron / persulfate systems have limited treatment capabilities for refractory organic pollutants, mainly due to the difficulty in regenerating Fe(II) and activating hydrogen peroxide or persulfate with Fe(III). The reduction of Fe(III) to Fe(II) can be accelerated by introducing energy (such as light, electricity) or adding chemical agents (such as chelating agents, reducing agents), thereby improving oxidation efficiency. However, the method of introducing energy is complicated to operate and increases the cost of treatment; chelating agents and reducing agents will compete with organic pollutants for active oxidizing species, which also reduces the reaction efficiency to a certain extent. In addition, another problem faced by these systems is the generation of free radicals (HO • / SO4 •- ) is highly active and can react with most anions, cations and organic matter in water almost non-selectively, resulting in waste of reagents.

[0004] Therefore, it is crucial to find an activation / catalyst that is effective, can effectively promote the Fe(III) / Fe(II) cycle, is less affected by pH, and is highly economical. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the iron / persulfate system and the traditional Fenton / Fenton-like technology, and to provide a method for degrading organic pollutants in water by using a redox mediator enhanced system to accelerate the Fe(III) / Fe(II) circulation, increase the utilization rate of the reagent, and improve the oxidation effect, thereby achieving efficient removal of organic pollutants in water.

[0006] A method for degrading organic pollutants in water by using a redox mediator enhanced system is specifically accomplished by the following steps:

[0007] Hydrogen peroxide or persulfate, a redox mediator and an iron salt are sequentially added to the water to be treated containing organic pollutants at room temperature, and the redox mediators are allowed to react with the organic pollutants in the water until they are completely reacted under stirring conditions. The redox mediator is an organic small molecule monomer containing a phenolic hydroxyl functional group, a nitrogen-containing cyclic compound containing a>N-OH structure or a>NO • The nitrogen-containing cyclic compound has a structure; the iron salt is a divalent iron salt or a trivalent iron salt.

[0008] The main principles of the method of the present invention are as follows:

[0009] 1. Redox mediators play the role of both Fe(III) reducing agent and electron shuttle in Fenton / Fenton-like systems, achieving efficient removal of organic pollutants through a "double cycle" mechanism. Figure 1 First, Fe(III) oxidation > NO • Formation of Fe(II) and >N=O + ,>N=O + While oxidizing the pollutants, they are converted back to >NO • , that is, the first cycle (the cycle of redox mediators) occurs; in addition, hydrogen peroxide can also re-oxidize the generated Fe(II) to Fe(III), promoting the occurrence of the second cycle (iron cycle), which is accompanied by HO • The production of active species such as Fe(III) can degrade organic pollutants in water and can also oxidize NO • ,Therefore, in the Fenton / Fenton-like system, the two cycles are interdependent and mutually reinforcing;

[0010] 2. The redox mediator plays the role of both Fe(III) reducing agent and electron shuttle in the iron / persulfate system, achieving efficient removal of organic pollutants through the occurrence of a "double cycle" mechanism. Figure 2 First, Fe(III) oxidation > NO • and generate Fe(II) and >N=O + ,>N=O + While oxidizing organic pollutants, they are converted back to >NO • , that is, the first cycle (the cycle of redox mediators) occurs; in addition, persulfate reoxidizes the generated Fe(II) to Fe(III), promoting the occurrence of the second cycle (iron cycle), which is accompanied by SO4 •-The generation of active species such as Fe(III) can degrade organic pollutants and oxidize NO • Therefore, in the iron / persulfate oxidation system, the two cycles are interdependent and mutually reinforcing.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] 1. The present invention introduces a redox mediator, which can effectively reduce Fe(III) in the Fenton / Fenton-like system to Fe(II), thereby accelerating the Fe(III) / Fe(II) cycle and improving the removal efficiency of organic pollutants;

[0013] 2. The main oxidizing species in the present invention is a moderately active redox mediator free radical, which overcomes the limitation that highly active species such as hydroxyl radicals are easily interfered by background matrices such as anions and cations and organic matter in water, enhances the selectivity of oxidizing species for target pollutants, and improves the decontamination capacity of this technology and the effective utilization rate of the reagent;

[0014] 3. The present invention introduces a redox mediator, which can effectively reduce Fe(III) in the iron / persulfate system to Fe(II), accelerate the Fe(III) / Fe(II) cycle, and greatly improve the efficiency of the iron / persulfate system in degrading organic pollutants;

[0015] 4. The present invention converts the highly active sulfate radical (SO4 •- ) into moderately active redox mediator free radicals, overcoming the limitation of this technology being easily interfered by background matrices such as anions, cations and organic matter, enhancing the selectivity of oxidizing species for target pollutants, increasing the decontamination capacity of this technology and improving the effective utilization rate of reagents;

[0016] 5. The present invention has a significant strengthening effect on the iron / persulfate system under the condition that the initial pH of the solution is 3-9, and exhibits a strong ability to degrade organic pollutants;

[0017] 6. The present invention is simple to operate, easy to implement, has broad industrial application prospects, and is easy to upgrade and transform existing water plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process in which the redox mediator plays the role of both Fe(III) reductant and electron shuttle in the Fenton / Fenton-like system, achieving efficient removal of organic pollutants through a "double cycle" mechanism;

[0019] Figure 2Schematic diagram of the process in which the redox mediator plays the role of both Fe(III) reducing agent and electron shuttle agent in the iron / persulfate system, achieving efficient removal of organic pollutants through the occurrence of a "double cycle" mechanism;

[0020] Figure 3 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Example 1 and Comparative Examples 1 to 4;

[0021] Figure 4 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Example 2 and Comparative Examples 5-9;

[0022] Figure 5 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Examples 2 to 4 and Comparative Example 7;

[0023] Figure 6 This is a schematic diagram of the change in the concentration of bisphenol A over time in the redox mediator-enhanced iron / persulfate system under different initial pH conditions in Example 2 and Example 5. DETAILED DESCRIPTION

[0024] Specific implementation method 1: This implementation method is a method for degrading organic pollutants in water by a redox mediator enhancement system, which is specifically completed by the following steps:

[0025] Hydrogen peroxide or persulfate, a redox mediator and an iron salt are sequentially added to the water to be treated containing organic pollutants at room temperature, and the redox mediators are allowed to react with the organic pollutants in the water until they are completely reacted under stirring conditions. The redox mediator is an organic small molecule monomer containing a phenolic hydroxyl functional group, a nitrogen-containing cyclic compound containing a>N-OH structure or a>NO • The nitrogen-containing cyclic compound has a structure; the iron salt is a divalent iron salt or a trivalent iron salt.

[0026] Specific embodiment 2: This embodiment differs from the specific embodiment 1 in that the organic small molecule monomer containing a phenolic hydroxyl functional group is selected from vanillin, vanillic acid, syringaldehyde, syringic acid, eugenol, p-coumaric acid, p-hydroxybenzaldehyde, p-hydroxybenzoic acid, ferulic acid, guaiacol, catechol, 3-methoxycatechol, trimethoxyphenol, acetovanillone and acetosyringone. The other steps are the same as those of the specific embodiment 1.

[0027] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that the nitrogen-containing cyclic compound containing a>N-OH structure is selected from 1-hydroxybenzotriazole, N-hydroxyphthalimide, violuric acid, 4-(1, 3-dioxolane-2-yl)-N-hydroxyphenylcarbonic acid diimide, N-hydroxythalidomide, 2-cyano-N'-hydroxyacetamidine, N-hydroxy-2-methylbenzamidine, N-hydroxy-4-methoxyindole-3-carboxamidine, N-hydroxy-2-benzyloxyaniline and N-hydroxyisoxazole-5-carboxamide. The other steps are the same as those of specific embodiment 1 or 2.

[0028] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: the • The nitrogen-containing cyclic compound of the structure is selected from 2,2,6,6-tetramethylpiperidinyl oxide, a derivative of 2,2,6,6-tetramethylpiperidinyl oxide, 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy, a derivative of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy, 3-carboxyl-2,2,5,5-tetramethylpyrrolidine-1-oxy free radical, a derivative of 3-(maleimidomethyl)-2,2,5,5-tetramethylpyrrolidine-1-oxy free radical and 9-azabicyclo[3.3.1]nonane-N-oxyl free radical. The other steps are the same as those in the first to third embodiments.

[0029] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the divalent iron salt is one or more of ferrous chloride, ferrous sulfate and ferrous nitrate; the trivalent iron salt is one or more of ferric chloride, ferrous sulfate and ferric nitrate. The other steps are the same as those of specific embodiments 1 to 4.

[0030] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the dosage of the iron salt is 0.01-0.5 mmol / L, and the molar ratio of iron to the redox mediator is (1-20): 1. The other steps are the same as those of specific embodiments 1 to 5.

[0031] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that: the persulfate is one or both of peroxymonosulfate and peroxydisulfate; the dosage of the persulfate is 0.1-1.0 mmol / L. The other steps are the same as those of specific embodiments 1 to 6.

[0032] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the dosage of hydrogen peroxide is 0.1-1.0 mmol / L. The other steps are the same as those of specific embodiments 1 to 7.

[0033] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the pH value of the water to be treated containing organic pollutants is 3 to 9, and the reaction time is 30 to 90 minutes. The other steps are the same as those of specific embodiments 1 to 8.

[0034] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that: the organic pollutants in the water to be treated containing organic pollutants include one or a mixture of phenols, amines, olefins and sulfonamides; the concentration of the organic pollutants in the water to be treated containing organic pollutants is 0.005mmol / L~0.05mmol / L. The other steps are the same as those in specific embodiments 1 to 9.

[0035] The following examples are used to verify the beneficial effects of the present invention:

[0036] Example 1: A method for degrading bisphenol A, an organic pollutant in water, by using a 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO)-enhanced iron sulfate / hydrogen peroxide Fenton system (H2O2 / Fe(III) / PTIO), which is carried out in the following steps:

[0037] At room temperature, a 10 mmol / L hydrogen peroxide solution, a 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution and a 2 mmol / L ferric sulfate solution are sequentially added to the untreated water containing bisphenol A with a pH value of 3.0, and the mixture is stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A begins. During the reaction, magnetic stirring is continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is evenly dispersed in the mixed solution. After 90 minutes of reaction, efficient removal of bisphenol A in water can be achieved.

[0038] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.05 mmol / L;

[0039] The concentration of hydrogen peroxide in the mixed solution is 0.5 mmol / L, the concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is 0.025 mmol / L, and the concentration of Fe(III) is 0.1 mmol / L.

[0040] Comparative Example 1: A method for oxidizing bisphenol A by adding a redox mediator alone (PTIO) is carried out according to the following steps:

[0041] A 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution was added to the treated water containing bisphenol A at a pH value of 3.0 at room temperature, and the mixture was stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began. During the reaction, magnetic stirring was continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) was evenly dispersed in the mixed solution. The reaction lasted for 90 minutes, and the removal rate of bisphenol A was detected.

[0042] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.05 mmol / L;

[0043] The concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) in the mixed solution is 0.025 mmol / L.

[0044] Comparative Example 2: A method for oxidation of bisphenol A by redox mediator and hydrogen peroxide (H2O2 / PTIO) was carried out in the following steps:

[0045] At room temperature, a 10 mmol / L hydrogen peroxide solution and a 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution were added to the treated water containing bisphenol A with a pH value of 3.0 in sequence, and the mixture was stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began. During the reaction, magnetic stirring was continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) was evenly dispersed in the mixed solution. The mixture was stirred continuously for 90 minutes, and the removal rate of bisphenol A was detected.

[0046] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.05 mmol / L;

[0047] The concentration of hydrogen peroxide in the mixed solution is 0.5 mmol / L, and the concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is 0.025 mmol / L.

[0048] Comparative Example 3: A method for oxidation of bisphenol A by redox mediator assisted by iron sulfate (Fe(III) / PTIO) was carried out in the following steps:

[0049] At room temperature, a 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution and a 2 mmol / L ferric sulfate solution are sequentially added to the treated water containing bisphenol A with a pH value of 3.0, and the mixture is stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A begins. During the reaction, magnetic stirring is continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is evenly dispersed in the mixed solution. After 90 minutes of reaction, efficient removal of bisphenol A in water can be achieved.

[0050] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.05 mmol / L;

[0051] The concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) in the mixed solution is 0.025 mmol / L, and the concentration of Fe(III) is 0.1 mmol / L.

[0052] Comparative Example 4: A method for oxidizing bisphenol A by activating hydrogen peroxide with ferric sulfate (H2O2 / Fe(III)) is carried out in the following steps:

[0053] At room temperature, a 10 mmol / L hydrogen peroxide solution and a 2 mmol / L ferric sulfate solution were sequentially added to the water to be treated containing bisphenol A with a pH value of 3.0, and the mixture was stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began, and the mixture was stirred continuously for 90 minutes to detect the removal rate of bisphenol A.

[0054] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.05 mmol / L;

[0055] The concentration of hydrogen peroxide in the mixed solution is 0.5 mmol / L, and the concentration of Fe(III) is 0.1 mmol / L.

[0056] Figure 3 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Example 1 and Comparative Examples 1 to 4;

[0057] Depend on Figure 3It can be seen that the degradation of bisphenol A by redox mediator alone and redox mediator in combination with hydrogen peroxide is not ideal, and the degradation rate of bisphenol A (BPA) within 90 minutes does not exceed 10%; redox mediator in combination with ferric sulfate can achieve 17.81% BPA removal, which is due to the fact that trivalent iron can oxidize the redox mediator to its oxidation state. Fe(III) has a poor activation effect on hydrogen peroxide, and only 14.05% of bisphenol A is removed within 90 minutes; when the redox mediator is added to the ferric sulfate / hydrogen peroxide system, the degradation rate of bisphenol A increases significantly, and the BPA removal rate can reach 90.06% at 90 minutes. It can be seen that the rapid removal of organic pollutants in water can only be achieved when the redox mediator, trivalent iron, and hydrogen peroxide described in the present invention are present at the same time.

[0058] Example 2: A method for degrading organic pollutants in water by 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxo (PTIO) enhanced iron / persulfate (PMS / Fe(III) / PTIO), which is carried out according to the following steps:

[0059] At room temperature, potassium permonosulfate (PMS) with a concentration of 10 mmol / L, 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution with a concentration of 1.0 mmol / L and ferric sulfate solution with a concentration of 2 mmol / L were added to the untreated water containing bisphenol A with a pH value of 5.0 in sequence, and stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began. During the reaction, continuous magnetic stirring was performed to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) was evenly dispersed in the mixed solution. After 90 minutes of reaction, efficient removal of bisphenol A in water could be achieved.

[0060] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0061] In the mixed solution, the concentration of potassium permonosulfate (PMS) is 0.02 mmol / L, the concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxo (PTIO) is 0.01 mmol / L, and the concentration of Fe(III) is 0.05 mmol / L.

[0062] Comparative Example 5: A method for oxidizing bisphenol A by adding persulfate alone (PMS) is carried out according to the following steps:

[0063] At room temperature, potassium permonosulfate (PMS) with a concentration of 10 mmol / L was added to the water to be treated containing bisphenol A with a pH value of 5.0, and the mixture was stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began, and the mixture was stirred continuously for 90 minutes to detect the removal rate of bisphenol A.

[0064] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0065] The concentration of potassium permonosulfate (PMS) in the mixed solution is 0.02 mmol / L.

[0066] Comparative Example 6: A method for oxidizing bisphenol A by adding a redox mediator alone (PTIO) is carried out according to the following steps:

[0067] A 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution was added to the treated water containing bisphenol A at a pH value of 5.0 at room temperature, and the mixture was stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began. During the reaction, magnetic stirring was continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) was evenly dispersed in the mixed solution. The mixture was stirred continuously for 90 minutes, and the removal rate of bisphenol A was detected.

[0068] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0069] The concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) in the mixed solution is 0.01 mmol / L.

[0070] Comparative Example 7: Fe(III) activated persulfate oxidation method for bisphenol A (PMS / Fe(III)), according to the following steps:

[0071] At room temperature, potassium permonosulfate (PMS) with a concentration of 10 mmol / L and ferric sulfate solution with a concentration of 2 mmol / L were added to the water to be treated containing bisphenol A with a pH value of 5.0 in sequence, and stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began, and the stirring was continued for 90 minutes to detect the removal rate of bisphenol A.

[0072] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0073] The concentration of potassium permonosulfate (PMS) in the mixed solution is 0.02 mmol / L, and the concentration of Fe(III) is 0.05 mmol / L.

[0074] Comparative Example 8: A method for oxidation of bisphenol A by redox mediator and persulfate (PMS / PTIO) is carried out according to the following steps:

[0075] At room temperature, potassium permonosulfate (PMS) with a concentration of 10 mmol / L and 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution with a concentration of 1.0 mmol / L were added to the water to be treated containing bisphenol A with a pH value of 5.0 in sequence, and stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A began. During the reaction, magnetic stirring was continued to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) was evenly dispersed in the mixed solution. Stirring was continued for 90 minutes, and the removal rate of bisphenol A was detected.

[0076] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0077] The concentration of potassium permonosulfate (PMS) in the mixed solution is 0.02 mmol / L, and the concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is 0.01 mmol / L.

[0078] Comparative Example 9: A method for oxidation of bisphenol A by redox mediator synergistically with Fe(III) (Fe(III) / PTIO) was carried out in the following steps:

[0079] At room temperature, a 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) solution and a 2 mmol / L ferric sulfate solution are sequentially added to the treated water containing bisphenol A with a pH value of 5.0, and the mixture is stirred evenly to obtain a mixed solution. The degradation reaction of bisphenol A begins. During the reaction, continuous magnetic stirring is performed to ensure that 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) is evenly dispersed in the mixed solution. After 90 minutes of reaction, efficient removal of bisphenol A in water can be achieved.

[0080] The concentration of bisphenol A in the water to be treated containing bisphenol A is 0.005 mmol / L;

[0081] The concentration of 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxide (PTIO) in the mixed solution is 0.01 mmol / L, and the concentration of Fe(III) is 0.05 mmol / L.

[0082] Figure 4 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Example 2 and Comparative Examples 5 to 9;

[0083] Depend on Figure 4It can be seen that the degradation of bisphenol A by persulfate alone and redox mediator alone is not ideal, and it is almost difficult to remove within 90 minutes; Fe (III) has a poor activation effect on persulfate, and only 12.6% of bisphenol A is removed within 90 minutes; when the redox mediator is added to the iron / persulfate system, the degradation rate of bisphenol A increases significantly, and the BPA removal rate can reach 89.14% at 90 minutes. At the same time, the figure also reflects that it is difficult for the redox mediator to directly activate persulfate, and the redox mediator can achieve 37.5% BPA removal in coordination with iron, which is due to the oxidation of the redox mediator to its oxidation state by iron. It can be seen that the effect of rapid removal of organic pollutants in water can only be achieved when the redox mediator, iron salt, and persulfate described in the present invention are present at the same time.

[0084] Example 3: The difference between this example and Example 2 is that the 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxy (PTIO) solution with a concentration of 1.0 mmol / L is replaced by a 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical (3-carboxy-PROXYL) solution with a concentration of 1.0 mmol / L. The other steps and parameters are the same as those in Example 3.

[0085] Example 4: This example is different from Example 2 in that the 1.0 mmol / L 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxyl (PTIO) solution is replaced with a 1.0 mmol / L 9-azabicyclo[3.3.1]nonane-N-oxyl radical (ABNO) solution. The other steps and parameters are the same as those in Example 3.

[0086] Figure 5 Schematic diagram of the change of bisphenol A concentration over time under different working conditions in Examples 2 to 4 and Comparative Example 7;

[0087] from Figure 5 It can be seen that: in the PMS / Fe(III) / 3-carboxyl-PROXYL system of Example 3, the change of bisphenol A concentration over time within 90 minutes is shown in the figure. Figure 5 It can be seen from the figure that the degradation reaction in Example 3 is efficient and rapid, and the BPA removal rate can reach 95.55% when the reaction is carried out for 30 minutes. The schematic diagram of the change of bisphenol A concentration over time in the PMS / Fe(III) / ABNO system of Example 4 within 90 minutes is shown in the figure. Figure 5 It can be seen that the degradation reaction of Example 4 is efficient and rapid, and the BPA removal rate can reach 82.88% when the reaction is carried out for 90 minutes.

[0088] Example 5: This example is different from Example 2 in that the pH values ​​of the water to be treated containing bisphenol A are 3, 4, 6, 7, 8, and 9. The other steps and parameters are the same as those in Example 2.

[0089] Figure 6 This is a schematic diagram of the change in the concentration of bisphenol A over time in the redox mediator-enhanced iron / persulfate system under different initial pH conditions in Example 2 and Example 5.

[0090] Depend on Figure 6 It can be seen that when the initial pH of the water to be treated containing bisphenol A is 3-7, the degradation effect of the system on BPA is very significant, and the removal rate of BPA exceeds 85% at 90 minutes. When the initial pH is 8 and 9, the removal rates of BPA by the system are 52.61% and 27.77%, respectively. In summary, the enhanced system of the present invention has a wide range of pH application conditions.

Claims

1. A method for degrading organic pollutants in water by a redox mediator-enhanced system, characterized in that The method is specifically completed according to the following steps: At room temperature, hydrogen peroxide or persulfate, a redox mediator and an iron salt are sequentially added to the water to be treated containing organic pollutants, and the redox mediator and an iron salt are reacted with the organic pollutants in the water to complete reaction under stirring conditions, wherein the redox mediator is 3-carboxyl-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical; and the iron salt is a divalent iron salt or a trivalent iron salt; The dosage of the iron salt is 0.01-0.5 mmol / L, wherein the molar ratio of iron to the redox mediator is (1-20):1; The dosage of the persulfate is 0.1-1.0 mmol / L; The dosage of the hydrogen peroxide is 0.1-1.0 mmol / L; The concentration of organic pollutants in the water to be treated containing organic pollutants is 0.005mmol / L~0.05mmol / L.

2. The method for degrading organic pollutants in water by a redox mediator enhancement system according to claim 1, characterized in that The divalent iron salt is one or more of ferrous chloride, ferrous sulfate and ferrous nitrate; the trivalent iron salt is one or more of ferric chloride, ferrous sulfate and ferric nitrate.

3. The method for degrading organic pollutants in water by a redox mediator enhancement system according to claim 1, characterized in that The persulfate is one or both of peroxymonosulfate and peroxydisulfate.

4. The method for degrading organic pollutants in water by a redox mediator enhancement system according to claim 1, characterized in that The pH value of the water to be treated containing organic pollutants is 3-9; and the reaction time is 30-90 minutes.

5. The method for degrading organic pollutants in water by using a redox mediator enhanced system according to claim 1, characterized in that The organic pollutants in the water to be treated containing organic pollutants include one or a mixture of phenols, amines, olefins and sulfonamides.

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