Controllable active oxygen species manipulation method

Abstract

The invention belongs to the technical field of environmental restoration and advanced oxidation, and particularly relates to a controllable active oxygen species manipulation method. According to the invention, the stabilized green rust is used as a structural activator, on the premise of maintaining a layered skeleton and oxygen deficiency, high-valence iron and active oxygen species are generated in situ and anchored, dissolution and quenching of the high-valence iron and the active oxygen species are inhibited, and slow release of peroxymonosulfate (PMS) oxidation capacity is realized. Besides, bicarbonate radicals can be added according to field conditions and requirements, a Fe-carbonate complex is formed by the bicarbonate radicals and surface Fe, the reaction energy barrier of high-grade oxide species is reduced, the apparent dynamic constant is increased by 1-2 orders of magnitude on the original basis, and controllable switching of high-grade oxidative degradation kinetics from slow to fast is achieved. The method is suitable for medium-and-long-term or emergency pollution repair of underground water and low-permeability media, and is also suitable for other advanced oxidation technology application scenes.

Description

Technical Field

[0001] This invention belongs to the field of environmental remediation and advanced oxidation technology, specifically relating to a method for controlling reactive oxygen species. Background Technology

[0002] Traditional PMS activation techniques include homogeneous Fe 2+ Activation technologies, such as nano-zero-valent iron activation technology and carbon-based catalyst activation technology, aim for instantaneous high activity, but generally suffer from the following drawbacks: First, the reaction rate is easily out of control, and the lifespan of the agent is generally short, making it difficult to meet the long-term stable repair requirements; Secondly, in traditional PMS activation technology, the iron leaching rate is high, generally reaching >20%, causing secondary pollution and clogging of the aquifer. Furthermore, the activator structure lacks stability and is prone to collapse during oxidation, resulting in non-renewable active sites. In addition, on-site conditions, including pH value, ionic strength, and natural organic matter, have a significant impact on kinetics, and there is a lack of effective means to "adjust the speed as needed".

[0003] Therefore, there is an urgent need to develop a PMS activation method that is structurally stable, has adjustable activity, and can release oxidation capacity over a long period of time. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a controllable method for manipulating reactive oxygen species. Using silicate or phosphate-stabilized rust-producing GR-Si or GR-P as structural activators, high-valence iron Fe(IV) and reactive oxygen species (including Fe(IV)=O, ·OH, etc.) are generated and anchored in situ while maintaining the layered framework and oxygen defects. 1 O2, SO4· - At oxygen vacancy sites in the GR interlayer or on the surface, metastable surface complexes are formed through Fe-O-Fe(IV) bridges or Fe-OO-Fe configurations, inhibiting the self-quenching and dissolution of oxide species. The half-life of the surface complexed higher oxide species is extended by 2-10 times compared to the solution-phase ROS, thereby achieving a slow release of PMS oxidation capacity. Simultaneously, by adding bicarbonate ions as needed, Fe-carbonate complexes are formed with Fe on the GR surface, reducing the reaction energy barrier of adsorbed high-valence iron Fe(IV) and reactive oxygen species, increasing the apparent kinetic constant by 1-2 orders of magnitude, and achieving a controllable switch from slow to fast advanced oxidation degradation kinetics. The schematic diagram of the stabilized layered framework of green rust and oxygen defect anchoring of Fe(IV) and ROS is shown in Figure 1. Figure 1 As shown.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a controllable PMS activation method, comprising the following steps: Stabilized green rust and PMS were simultaneously added to water containing pollutants to react. Even under conditions of power failure and no external energy input, Fe(IV) and ROS were continuously released, achieving an oxidation capacity of PMS > 72 hours.

[0006] Furthermore, it also includes the following steps: Adding bicarbonate can increase the degradation rate by 20-80 times.

[0007] Furthermore, the stabilized green rust is a green rust with a hexagonal layered structure stabilized by organic / inorganic anion intercalation or metal ion surface adsorption, specifically at least one of silicate-stabilized green rust GR-Si, phosphate-stabilized green rust GR-P, lauric acid organic anion modified green rust GR-C12, and trivalent chromium doped green rust GR-Cr(III).

[0008] Furthermore, the method for preparing silicate-stabilized green rust GR-Si includes the following steps: Step X1: Dissolve sodium chloride and glycine in deionized water, purge with nitrogen gas, and stir; Step X2: Under nitrogen gas conditions, first add FeCl2 solution and adjust the pH value, then add FeCl3 solution and adjust the pH value, repeat four times, and then let it stand in the anaerobic chamber. Step X3: Remove the supernatant and centrifuge the precipitate to wash it. Place the washed precipitate in oxygen-free deionized water to obtain a green rust suspension. Step X4: Mix sodium metasilicate nonahydrate solution with green rust suspension to prepare GR-Si solution.

[0009] Furthermore, the method for preparing the phosphate-stabilized green rust GR-P includes the following steps: Step Y1: Dissolve sodium chloride and glycine in deionized water, purge with nitrogen gas, and stir; Step Y2: Under nitrogen gas conditions, first add FeCl2 solution and adjust the pH value, then add FeCl3 solution and adjust the pH value, repeat four times, and then let it stand in the anaerobic chamber. Step Y3: Remove the supernatant and centrifuge the precipitate to wash it. Place the washed precipitate in oxygen-free deionized water to obtain a green rust suspension. Step Y4: Mix sodium phosphate dodecahydrate solution with green rust suspension to prepare GR-P solution.

[0010] Furthermore, in steps X4 and Y4, the molar ratio of Fe(II) to silicon or phosphorus is controlled to be 10:1.

[0011] Furthermore, the amount of stabilized green rust and PMS is controlled at a PMS / GR-Fe(II) molar ratio of 0.5-2:1.

[0012] Furthermore, the reaction is carried out at a pH of 5-8, a temperature of 5-30°C, and a time of 1.5-15 h. The apparent rate constant of degradation, k0, is 1-16 μmol / L. -1 h- 1 Fe dissolution < 5%, and skeleton morphology retention > 95%.

[0013] Furthermore, the pollutant is at least one of chlorinated hydrocarbons, antibiotics, and pesticides.

[0014] Furthermore, the dosage of the bicarbonate ion is 50-500 mg / L. -1 The apparent rate constant k0 of degradation after the addition of bicarbonate increased by 20-80 times compared to the original value, reaching a maximum of 1.6 × 10⁻⁶. 2 μmol L -1 h -1 .

[0015] Furthermore, the stabilized green rust can be reduced and soaked with sodium dithionite, and can be recycled more than 5 times with a structure retention rate of more than 90%.

[0016] Furthermore, the stabilized green rust is combined with biochar, zeolite, or zero-valent iron to form a multi-level porous structure, which further increases the number of oxygen vacancies and the controllable release of ROS.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) Stable structure: The stabilized green rust skeleton of the present invention does not collapse during the oxidation process, and the oxygen defect can be regenerated, effectively solving the problem of "one-time activator".

[0018] (2) Controllable activity: This invention utilizes HCO3 - The dosage can be switched at a rate of 20-80 times, which can meet the dual needs of long-term slow release or emergency treatment.

[0019] (3) Environmentally friendly: During the entire degradation process of this invention, Fe leaching in the rapid mode is <3%, and Fe leaching in the slow-release mode is <10%, with no secondary pollution.

[0020] (4) Economical and long-term: The stabilized green rust cycle in this invention is ≥3 times, and the oxidant consumption per unit pollutant is reduced by 30-50%, which is applicable to various scenarios such as low-permeability aquifers, PRB and in-situ injection. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the layered skeleton of stabilized green rust and the anchoring of Fe(IV) and ROS by oxygen defects according to the present invention.

[0022] Figure 2 Degradation kinetics curves of TCE for PMS activated by different GRs.

[0023] Figure 3 To add HCO3 - TCE degradation kinetic curves before and after degradation.

[0024] Figure 4 Comparison of SEM and TEM images of different GRs after rapid oxidation by PMS.

[0025] Figure 5 Degradation kinetics curves for multiple additions of TCE.

[0026] Figure 6 Comparison of activation kinetics for TCE degradation by GR-Si, GR-P, and GR-activated PMS. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0029] Example 1: Preparation of Stabilized Green Rust GR-Si (1) Accurately weigh 5.8 g sodium chloride (NaCl) and 2.1 g glycine (GLY), and dissolve them in 400 mL of deionized water. Purge the solution with nitrogen gas (N2) for at least 1 h, and continuously stir the solution with a magnetic stirrer during the purging process; (2) After ventilating for 1 h, add 25 mL of pre-prepared 0.5 M FeCl2 solution and 20 mL of 0.1 M FeCl3 solution in sequence, as follows: First add 25 mL of FeCl2 solution. 2+ The solution was prepared, and the pH was adjusted to 8 using 1M sodium hydroxide (NaOH) solution. Then, 5 mL of Fe was added. 3+ The solution is then adjusted to the pH value again; this process needs to be repeated four times, adding Fe each time. 3+After adding the iron solution, the pH value must be adjusted to 8. Throughout the entire process of adding the iron solution, nitrogen gas (N2) should be continuously introduced while stirring. After the iron solution has been added, the reaction system should be immediately transferred to an anaerobic chamber for settling. (3) After standing for a period of time, remove the supernatant and use oxygen-free deionized water to perform two centrifugation washing operations on the precipitate. Place the washed precipitate in oxygen-free deionized water, add 100 mL of water and shake gently to obtain a green rust (GR) suspension with a Fe(II) concentration of 56 mM. (4) Sodium metasilicate nonahydrate (Na2SiO3•9H2O) was used as the silicon source introduction reagent. In the anaerobic chamber, according to the principle that the molar ratio of Fe(II) to silicon is 10:1, a certain volume of sodium metasilicate aqueous solution was measured and mixed with the basic GR to obtain GR-Si solution.

[0030] Example 2: Preparation of Stabilized Green Rust GR-P (1) Accurately weigh 5.8 g sodium chloride (NaCl) and 2.1 g glycine (GLY), and dissolve them in 400 mL of deionized water. Purge the solution with nitrogen gas (N2) for at least 1 h, and continuously stir the solution with a magnetic stirrer during the purging process; (2) After ventilating for 1 h, add 25 mL of pre-prepared 0.5 M FeCl2 solution and 20 mL of 0.1 M FeCl3 solution in sequence, as follows: First add 25 mL of FeCl2 solution. 2+ The solution was prepared, and the pH was adjusted to 8 using 1M sodium hydroxide (NaOH) solution. Then, 5 mL of Fe was added. 3+ The solution is then adjusted to the pH value again; this process needs to be repeated four times, adding Fe each time. 3+ After adding the iron solution, the pH value must be adjusted to 8. Throughout the entire process of adding the iron solution, nitrogen gas (N2) should be continuously introduced while stirring. After the iron solution has been added, the reaction system should be immediately transferred to an anaerobic chamber for settling. (3) After standing for a period of time, remove the supernatant and use oxygen-free deionized water to perform two centrifugation washing operations on the precipitate. Place the washed precipitate in oxygen-free deionized water, add 100 mL of water and shake gently to obtain a green rust (GR) suspension with a Fe(II) concentration of 56 mM. (4) Using sodium dodecahydrate (Na3PO4·12H2O) as the phosphorus source, according to the principle that the molar ratio of Fe(II) to phosphorus is 10:1, a certain volume of sodium dodecahydrate solution is measured and mixed with the basic GR to obtain GR-P solution.

[0031] Comparative Example 1: Preparation of Basic Green Rust GR (1) Accurately weigh 5.8 g sodium chloride (NaCl) and 2.1 g glycine (GLY), and dissolve them in 400 mL of deionized water. Purge the solution with nitrogen gas (N2) for at least 1 h, and continuously stir the solution with a magnetic stirrer during the purging process; (2) After ventilating for 1 h, add 25 mL of pre-prepared 0.5 M FeCl2 solution and 20 mL of 0.1 M FeCl3 solution in sequence, as follows: First add 25 mL of FeCl2 solution. 2+ The solution was prepared, and the pH was adjusted to 8 using 1M sodium hydroxide (NaOH) solution. Then, 5 mL of Fe was added. 3+ The solution is then adjusted to the pH value again; this process needs to be repeated four times, adding Fe each time. 3+ After adding the iron solution, the pH value must be adjusted to 8. Throughout the entire process of adding the iron solution, nitrogen gas (N2) should be continuously introduced while stirring. After the iron solution has been added, the reaction system should be immediately transferred to an anaerobic chamber for settling. (3) After standing for a period of time, remove the supernatant and use oxygen-free deionized water to perform two centrifugation washing operations on the precipitate. Place the washed precipitate in oxygen-free deionized water, add 100 mL of water and shake gently to obtain a green rust (GR) suspension with a Fe(II) concentration of 56 mM.

[0032] Example 3: Slow-release oxidation and rapid switching of stabilized green rust GR-Si and PMS 1 mM GR-Si prepared in Example 1 and 2 mM PMS (PMS / Fe(II) = 2:1) were added sequentially to 10 mL of simulated groundwater (pH 7.0) containing 20 μM TCE. The reaction was carried out at 25 °C and 150 rpm for 8 h, and the TCE removal rate was 100%, k0 = 2.45 μmol L⁻¹. -1 h -1 Total Fe dissolution was 1.47%, and GR retained its hexagonal lamellar morphology after the reaction, such as... Figure 4 As shown in (b) and (e).

[0033] Each time the TCE concentration drops to 0, 50 μL of TCE stock solution is rapidly injected again to restore the initial TCE concentration. The resulting degradation kinetic curves are shown below. Figure 5 As shown, repeatable TCE degradation efficiency can be observed in all three cycles of TCE addition. This indicates that the advanced oxide species are not rapidly quenched in the system, but rather maintain a relatively long reactivity.

[0034] After adding GR-Si and PMS, TCE was added after static aging for 2, 4, and 8 hours. After all three aging times, the TCE removal rate reached 100% within 25 hours, with similar degradation rates of approximately k0 = 1.8 μmol / L. -1 h -1 This indicates that higher oxide species do not undergo rapid quenching in the system, but rather maintain a relatively long reactivity.

[0035] The degradation kinetics curves of TCE by GR-Si activated PMS were obtained by changing the ratio of GR-Si to PMS to PMS as follows: (PMS / Fe(II) = 2:1, 1:1, 2:3, 1:3). Figure 2 As shown on the left side of the diagram, it can be seen that TCE degradation is significantly inhibited under high Fe concentrations. This is because excess Fe(II) reacts with active species, competing with TCE and reducing the number of active species available for TCE oxidation, thereby lowering the reaction rate.

[0036] Further add 500 mg L to the oxidation system -1 NaHCO3, all other conditions being the same, TCE degradation kinetics curve is as follows: Figure 3 As shown by the blue curve, when the reaction time was shortened to 12 min, k0 decreased from 2.45 μmol / L. -1 h -1 Increased to 116.97 μmol L -1 h -1 The Fe dissolution rate was 2.07%. This indicates that the activity of higher oxide species in the reaction system can be adjusted from slow release to rapid reaction, allowing for on-demand switching of kinetics.

[0037] Example 4: Slow-release oxidation and rapid switching between GR-P and PMS for stabilizing green rust 1 mM of GR-P prepared in Example 2 and 2 mM PMS (PMS / Fe(II) = 2:1) were added sequentially to 10 mL of simulated groundwater (pH 7.0) containing 20 μM TCE. The reaction was carried out at 25 °C and 150 rpm for 8 h, and the TCE removal rate was 100%, k0 = 2.11 μmol L⁻¹. -1 h -1 Total Fe dissolution was 4.30%, and GR retained its hexagonal lamellar morphology after the reaction, such as... Figure 4 As shown in (c) and (f).

[0038] The degradation kinetics curves of TCE by GR-P-activated PMS were obtained by changing the ratio of GR-P to PMS to PMS as PMS / Fe(II) = 1:1, 2:3, and 1:3, as shown in the figure. Figure 2As shown on the right side of the figure, it can be seen that TCE degradation is significantly inhibited under high Fe concentrations. This is because excess Fe(II) reacts with active species, competes with TCE, reduces the number of active species available for TCE oxidation, and thus lowers the reaction rate.

[0039] Further add 500 mg L to the oxidation system -1 NaHCO3, all other conditions being the same, TCE degradation kinetics curve is as follows: Figure 3 As shown by the green curve, when the reaction time is shortened to 10 min, k0 decreases from 2.11 μmol / L. -1 h -1 Increased to 163.72 μmol L -1 h -1 Fe dissolution decreased to 1.51%. This indicates that the activity of higher oxide species in the reaction system can be adjusted from slow release to rapid reaction, allowing for on-demand switching of kinetics.

[0040] Comparative Example 2: Slow-release oxidation and rapid switching of basic green rust treatments using GR and PMS 1 mM of the basic green rust GR prepared in Comparative Example 1 and 2 mM PMS (PMS / Fe(II) = 2:1) were added sequentially to 10 mL of simulated groundwater (pH 7.0) containing 20 μM TCE. The reaction was carried out at 25 °C and 150 rpm for 8 h, and the TCE removal rate was 100%, k0 = 3.27 μmol L⁻¹. -1 h -1 The total Fe dissolution was 5.18%. The SEM and TEM images of GR after the reaction are shown below. Figure 4 As shown in (a) and (d), it can be seen that GR still maintains a relatively intact lamellar structure, but there are large particles on the surface, which may be due to the dissolution of its iron.

[0041] Activation kinetics of PMS degradation of TCE by GR-Si, GR-P, and GR, for example Figure 6 As shown, the inhibition levels of different systems vary. At a molar ratio of 1:3, after 6 h of reaction, the removal rates of PMS / GR, PMS / GR-Si, and PMS / GR-P were 65.70%, 72.34%, and 72.73%, respectively. To completely remove the same concentration of TCE, the PMS / GR system required approximately 22 h, while GR-Si and GR-P only required 13–14 h. This indicates that the PMS and GR composite system had the most significant inhibition effect, while GR-Si and GR-P showed certain advantages. According to existing research, Si and P can complex with Fe, reducing the structural Fe(II) used for activation, resulting in fewer active sites in GR-Si and GR-P than in GR, thus leading to a weaker inhibition effect than GR under the same conditions.

[0042] Further add 500 mg L to the oxidation system -1 NaHCO3, all other conditions being the same, TCE degradation kinetics curve is as follows: Figure 3 As shown by the red curve in the figure, when the reaction time is shortened to 20 min, k0 decreases from 3.27 μmol L⁻¹. -1 Increased to 62.33 μmol L -1 h -1 Fe dissolution decreased to 2.27%. This indicates that the activity of higher oxide species in the reaction system can be adjusted from slow release to rapid reaction, allowing for on-demand switching of kinetics.

[0043] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A controllable PMS activation method, characterized in that, Includes the following steps: Stabilized green rust and PMS were added simultaneously to water containing pollutants to react, achieving an oxidation capacity of PMS > 72 hours.

2. The controllable PMS activation method according to claim 1, characterized in that, It also includes the following steps: Adding bicarbonate can increase the degradation rate by 20-80 times.

3. The controllable PMS activation method according to claim 1, characterized in that, The stabilized green rust is a green rust with a hexagonal layered structure stabilized by organic / inorganic anion intercalation or metal ion surface adsorption, specifically at least one of silicate-stabilized green rust GR-Si, phosphate-stabilized green rust GR-P, lauric acid organic anion modified green rust GR-C12, and trivalent chromium doped green rust GR-Cr(III).

4. The controllable PMS activation method according to claim 3, characterized in that, The method for preparing silicate-stabilized green rust GR-Si includes the following steps: Step X1: Dissolve sodium chloride and glycine in deionized water, purge with nitrogen gas, and stir; Step X2: Under nitrogen gas conditions, first add FeCl2 solution and adjust the pH value, then add FeCl3 solution and adjust the pH value, repeat four times, and then let it stand in the anaerobic chamber. Step X3: Remove the supernatant and centrifuge the precipitate to wash it. Place the washed precipitate in oxygen-free deionized water to obtain a green rust suspension. Step X4: Mix sodium metasilicate nonahydrate solution with green rust suspension to prepare GR-Si solution.

5. The controllable PMS activation method according to claim 3, characterized in that, The method for preparing phosphate-stabilized green rust GR-P includes the following steps: Step Y1: Dissolve sodium chloride and glycine in deionized water, purge with nitrogen gas, and stir; Step Y2: Under nitrogen gas conditions, first add FeCl2 solution and adjust the pH value, then add FeCl3 solution and adjust the pH value, repeat four times, and then let it stand in the anaerobic chamber. Step Y3: Remove the supernatant and centrifuge the precipitate to wash it. Place the washed precipitate in oxygen-free deionized water to obtain a green rust suspension. Step Y4: Mix sodium phosphate dodecahydrate solution with green rust suspension to prepare GR-P solution.

6. A controllable PMS activation method according to claim 4 or 5, characterized in that, In steps X4 and Y4, the molar ratio of Fe(II) to silicon or phosphorus is controlled to be 10:

1.

7. The controllable PMS activation method according to claim 1, characterized in that, The amount of stabilized green rust and PMS is controlled at a PMS / GR-Fe(II) molar ratio of 0.5-2:

1.

8. The controllable PMS activation method according to claim 1, characterized in that, The reaction is carried out at a pH of 5-8, a temperature of 5-30℃, and a time of 1.5-15 h.

9. The controllable PMS activation method according to claim 1, characterized in that, The pollutant is at least one of chlorinated hydrocarbons, antibiotics, and pesticides.

10. A controllable PMS activation method according to claim 2, characterized in that, The dosage of bicarbonate is 50-500 mg / L. -1 .

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