Method for degrading polycyclic aromatic hydrocarbons by micro-nano bubble synergistic ferrous sulfide activated oxygen

Abstract

The application provides a method for degrading polycyclic aromatic hydrocarbons by micro-nano bubbles and synergistic ferrous sulfide activated oxygen, comprising the following steps: simulating natural in-situ conditions in an anaerobic serum bottle, preparing ferrous sulfide under different iron-sulfur ratio environments; adding micro-nano bubbles and polycyclic aromatic hydrocarbon mother liquor into the anaerobic system containing ferrous sulfide; immediately introducing oxygen, and removing polycyclic aromatic hydrocarbons in the system by micro-nano bubbles and synergistic ferrous sulfide activated oxygen; the ferrous sulfide used in the application can efficiently activate oxygen to produce reactive oxygen species, effectively improve the degradation efficiency of polycyclic aromatic hydrocarbons, and has obvious degradation effect in a short time; the application process is simple and green; the micro-nano bubbles used in the application can significantly improve the degradation efficiency by mechanisms such as synergistic electron transfer, improving gas mass transfer efficiency and changing oxidation-reduction conditions; under aerobic conditions, the micro-nano bubbles can improve the degradation efficiency of polycyclic aromatic hydrocarbons by ferrous sulfide by more than 20%, and can efficiently remove pollutants.

Description

Technical Field

[0001] This invention belongs to the field of water pollution control application technology, specifically relating to a method for the degradation of polycyclic aromatic hydrocarbons by ferrous sulfide activated by micro-nano bubbles. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are aromatic hydrocarbons with two or more fused benzene rings, typically produced by the incomplete combustion or high-temperature cracking of organic matter. They are recognized as carcinogenic, teratogenic, and mutagenic. As persistent organic pollutants, PAHs tend to accumulate in aquifers and persist for extended periods, posing a continuous threat to human health and the ecological environment. Sixteen PAHs, including naphthalene, have been listed as priority pollutants by the U.S. Environmental Protection Agency. Current remediation strategies commonly employ physicochemical methods to increase the mobility and availability of PAHs, such as thermal desorption, chemical solubilization, and electrokinetic migration, or utilize chemobiological methods for oxidation-reduction or degradation, such as chemical oxidation, microbial remediation, and phytoremediation. However, thermal desorption and electrokinetic remediation technologies require electricity and are costly; chemical solubilization and chemical oxidation technologies cause significant environmental disturbance and pose a risk of secondary pollution; and microbial and phytoremediation technologies are less efficient and require excessively long remediation times. Therefore, there is an urgent need to develop low-disturbance, low-cost, green, and efficient remediation technologies.

[0003] Ferrous sulfide (FeS), a naturally occurring mineral found in geological formations, has been used to remove various environmental pollutants due to its unique crystal structure, large specific surface area, and strong reducing properties. Among the generated reactive oxygen species, the ·OH group has a redox potential as high as 2.8V, enabling it to non-selectively oxidize persistent organic pollutants and possessing the potential to degrade polycyclic aromatic hydrocarbons (PAHs). Micro- and nanobubbles, as an emerging technology, possess long-term stability, large specific surface area, high oxygen dissolution rate, and high mass transfer efficiency, without causing secondary pollution. Considering the widespread presence of FeS in groundwater environments, no additional chemical reagents are needed, resulting in lower costs and an environmentally friendly approach. Utilizing the synergistic effect of micro- and nanobubbles with FeS is expected to enhance the efficiency of generating reactive oxygen species from activated oxygen, thereby promoting the degradation of PAHs. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for enhancing the degradation of polycyclic aromatic hydrocarbons by ferrous sulfide activated by micro-nano bubbles.

[0005] To achieve the above objectives, the solution of the present invention is:

[0006] A method for the degradation of polycyclic aromatic hydrocarbons by micro / nano bubble-enhanced ferrous sulfide-activated oxygen, comprising the following steps:

[0007] (1) Ferrous sulfide was prepared in anaerobic serum bottles under simulated natural in-situ conditions with different iron-sulfur ratios.

[0008] (2) Add micro-nano bubbles and polycyclic aromatic hydrocarbon mother liquor to an anaerobic system containing ferrous sulfide;

[0009] (3) Immediately introduce oxygen, and micro-nano bubbles work together with ferrous sulfide to activate oxygen and remove polycyclic aromatic hydrocarbons from the system.

[0010] Preferably, in step (1), the preparation process of ferrous sulfide is as follows: sodium sulfide nonahydrate and ferrous chloride tetrahydrate are prepared separately in an anaerobic glove box. Sodium sulfide mother solution and ferrous chloride mother solution are added sequentially to the buffer solution of the anaerobic serum bottle. The iron-sulfur ratio is changed by changing the volume of FeCl2 mother solution added. The volumes of sodium sulfide mother solution and ferrous chloride mother solution do not exceed 2% of the total volume of the buffer solution in the anaerobic serum bottle.

[0011] The concentrations of sodium sulfide mother liquor and ferrous chloride mother liquor were 200 mM-2 M, respectively.

[0012] The buffer solution in the serum bottle is prepared from boric acid, sodium tetraborate and sodium chloride, and natural nutrients such as ammonium chloride, magnesium chloride and calcium chloride are added to simulate natural in-situ conditions.

[0013] Preferably, in step (1), the sulfur concentration of ferrous sulfide is 0.2-2 mM, more preferably 1.0 mM.

[0014] Preferably, in step (1), the iron-sulfur ratio of ferrous sulfide is 1:1-50:1, more preferably 35:1.

[0015] Preferably, in step (2), the preparation process of micro-nano bubbles is as follows: micro-nano bubbles are prepared using a micro-nano bubble generator, and the gas source is selected from one or a mixture of oxygen, nitrogen, and air (preferably oxygen). The total volume of pure water used in the preparation is 1500-2000 mL, the water pressure is 0.1-0.2 MPa, the preparation time is 5-10 min, and the bubble concentration in the resulting micro-nano bubble water is approximately 10. 6 -10 9 per mL.

[0016] Preferably, in step (2), the volume of the added micro-nano bubble water is 0.5-50% of the total volume of the solution in the anaerobic serum bottle, more preferably 35%.

[0017] Preferably, in step (2), the polycyclic aromatic hydrocarbons in the polycyclic aromatic hydrocarbon mother liquor are selected from one or more of naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene. The polycyclic aromatic hydrocarbons are solubilized with ethanol and sonicated for more than 3 minutes to completely dissolve them, thus preparing a 10 g / L pollutant mother liquor.

[0018] Preferably, in step (2), after adding the polycyclic aromatic hydrocarbon mother liquor, the concentration of the polycyclic aromatic hydrocarbon mother liquor in the system is 0.5-10 mg / L.

[0019] Preferably, in step (3), the oxygen flow rate is 30-120 mL / min and the ventilation time is 30-120 s.

[0020] Preferably, in step (3), the mixing reaction time in the system is 2-6 hours.

[0021] Due to the adoption of the above solution, the beneficial effects of the present invention are:

[0022] (1) The natural decay of polycyclic aromatic hydrocarbons often takes months to years. The ferrous sulfide used in this invention can efficiently activate oxygen to produce strong active oxygen substances within three hours. The strong oxidation potential of ·OH up to 2.8V enables it to effectively improve the degradation efficiency of polycyclic aromatic hydrocarbons. It has a significant degradation effect of more than 20% in a short time. The application process is simple and environmentally friendly.

[0023] (2) For oxygen-consuming processes, the mass transfer efficiency of oxygen is crucial. The micro-nano bubbles used in this invention have a large specific surface area. Compared with ordinary fine bubbles with a particle size of 1 mm, the specific surface area of ​​the micro-nano bubbles with a particle size of 100 nm in this invention can reach more than 10,000 times. According to Henry's Law, a large specific surface area can improve the gas-liquid mass transfer efficiency of micro-nano bubbles, continuously replenishing dissolved oxygen in the water, thereby improving the oxygen mass transfer efficiency. At the same time, the high zeta potential of -45 mV of micro-nano bubbles can increase the redox potential of Fe(II), making it easier for Fe(II) to lose electrons, enhancing the electron transfer of Fe(II), accelerating the process of activating oxygen to generate reactive oxygen species, and ultimately significantly improving the degradation efficiency by more than 20%. Moreover, micro-nano bubbles are prepared using pure water, which is simple to operate and environmentally friendly, without generating secondary pollution, and has practical application and promotion potential.

[0024] (3) The reaction conditions required by the present invention are easy to achieve. The reaction reagent (ferrous sulfide) is abundant in nature and widely exists in the reducing medium of groundwater containing organic matter. No additional chemical reagents are required, and no secondary pollution will be generated in the remediation application.

[0025] (4) Under aerobic conditions, the efficiency of micro-nano bubbles in degrading polycyclic aromatic hydrocarbons by ferrous sulfide can be increased by more than 20%, which can efficiently remove pollutants. Furthermore, it can be used for the in-situ remediation of polycyclic aromatic hydrocarbon pollution in groundwater, thereby removing stable target pollutants. Attached Figure Description

[0026] Figure 1 This is a comparison chart showing the efficiency of ferrous sulfide activation and degradation of naphthalene by micro-nano bubbles with different gas sources in Examples 1 to 3 of the present invention.

[0027] Figure 2 This is a comparison chart showing the efficiency of ferrous sulfide activation and degradation of naphthalene by different amounts of micro-nano bubbles in Examples 4 to 10 of the present invention.

[0028] Figure 3 This is a comparison chart showing the efficiency of naphthalene degradation by micro-nano bubbles synergistically activated with ferrous sulfide under different iron-sulfur ratios in Examples 11 to 16 of the present invention. Detailed Implementation

[0029] This invention provides a method for the degradation of polycyclic aromatic hydrocarbons by ferrous sulfide activated by micro-nano bubbles. The invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1

[0031] 10 mM ferrous sulfide was prepared in an anaerobic glove box, sealed in a clamp-on anaerobic flask, and stored in the dark for 5 days before use. 1 g of naphthalene was weighed and solubilized with ethanol to prepare a 100 mL stock solution with a concentration of 10 g / L. The solution was sonicated for at least 3 minutes to ensure uniform distribution. Micro-nanobubbles were prepared using a micro-nanobubble generator with nitrogen as the gas source. The total solution volume was 1800 mL, the water pressure was 0.15 MPa, and the preparation time was 10 minutes. The micro-nanobubble particle size distribution was 10-1000 nm, concentrated around 100 nm. 50 mL of micro-nanobubbles were added to the anaerobic flask using a 10 mL syringe, and oxygen was rapidly introduced at a flow rate of 60 mL / min for 90 seconds. The total solution volume was controlled to be 100 mL, and 25 μL of the stock solution was added using a microsyringe. At this point, the concentration of naphthalene in the system was 5 mg / L. The anaerobic flask was placed on a shaker at 200 rpm, and the system was kept sealed during the reaction at room temperature in the dark.

[0032] At time points of 30 min, 60 min, 90 min, 120 min, 150 min, and 180 min from the start of the reaction, 0.8 mL of sample was taken using a 1 mL syringe and added to a 2 mL vial containing 0.8 mL of ethanol. After filtration through a 0.22 μm nylon membrane, the residual naphthalene concentration was analyzed using high-performance liquid chromatography (HPLC). Three replicates were set up for each experiment, and the average value was used for analysis and discussion. The residual rate was used to reflect the degradation effect; the residual rate was the percentage of naphthalene concentration in the sample at each time point relative to the initial concentration.

[0033] Example 2

[0034] Compared with Example 1, the only difference is that the gas source for the micro-nano bubbles is air.

[0035] Example 3

[0036] Compared with Example 1, the only difference is that the gas source for the micro-nano bubbles is oxygen.

[0037] In Examples 1 to 3, the naphthalene residual rate-time relationship graph was obtained, as follows: Figure 1 As shown in the figure. The vertical axis represents the naphthalene residue rate, and the horizontal axis represents the reaction time. The degradation effect is reflected by the naphthalene residue rate; the lower the naphthalene residue rate, the better the degradation effect. The naphthalene residue rate is the ratio of the residual naphthalene concentration to the initial naphthalene concentration at each time point. Figure 1 It can be seen that the degradation effects of micro-nano bubbles using nitrogen, air, and oxygen as gas sources are almost identical, around 30%. Since oxygen is an important controlling factor in the reaction process, and oxygen micro-nano bubbles have a zeta potential as high as -45mV, oxygen micro-nano bubbles are the optimal choice.

[0038] Example 4

[0039] Compared to Example 1, the only difference was the amount of micro / nanobubbles used. Concentration gradients of 0 mL, 3 mL, 5 mL, 10 mL, 20 mL, 35 mL, and 50 mL were used, while keeping the total system volume, naphthalene concentration, and oxygen amount constant. In Example 4, the amount of oxygen micro / nanobubbles used was 0 mL.

[0040] Example 5

[0041] Compared to Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 3 mL.

[0042] Example 6

[0043] Compared to Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 5 mL.

[0044] Example 7

[0045] Compared to Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 10 mL.

[0046] Example 8

[0047] Compared to Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 20 mL.

[0048] Example 9

[0049] Compared with Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 35 mL.

[0050] Example 10

[0051] Compared to Example 4, the only difference is that the amount of oxygen micro-nano bubbles used is 50 mL.

[0052] In Examples 4 to 10, the naphthalene residue rate-time relationship graph was obtained, as shown below. Figure 2 As shown in the figure, the effect of different amounts of micro / nanobubbles on the degradation efficiency of naphthalene was compared. The figure shows that when the amount of micro / nanobubbles increased from 0 mL to 35 mL, the residual naphthalene percentage gradually decreased from 83% to 61%, and the degradation efficiency increased with increasing micro / nanobubble amount. However, when the amount was further increased, the residual naphthalene percentage increased from 61% to 74%, indicating that the increased amount of micro / nanobubbles hindered degradation. Therefore, the optimal amount of micro / nanobubbles is 35 mL. Figure 2 It can be seen that after 3 hours of reaction, the degradation rate of pollutants by the micro-nano bubble enhancement system is >35%; compared with the system without micro-nano bubbles, the efficiency is increased by more than 20%.

[0053] Example 11

[0054] Compared to Example 9, the only difference was the change in the iron-to-sulfur ratio of ferrous sulfide. The ratios were 1:1, 2:1, 5:1, 10:1, 30:1, and 50:1, with a sulfur concentration of 1 mM. 35 mL of oxygen microbubbles were added, while keeping the total system volume, naphthalene concentration, and oxygen amount constant. The iron-to-sulfur ratio in Example 11 was 1:1.

[0055] Example 12

[0056] The only difference from Example 11 is that the iron-sulfur ratio is 2:1.

[0057] Example 13

[0058] The only difference from Example 11 is that the iron-sulfur ratio is 5:1.

[0059] Example 14

[0060] The only difference from Example 11 is that the iron-sulfur ratio is 10:1.

[0061] Example 15

[0062] The only difference from Example 11 is that the iron-sulfur ratio is 30:1.

[0063] Example 16

[0064] The only difference from Example 11 is that the iron-sulfur ratio is 50:1.

[0065] In Examples 11 to 16, the naphthalene residue rate-time relationship graph was obtained, as follows: Figure 3As shown in the figure, the effect of different iron-sulfur ratios on the degradation efficiency of naphthalene was compared. The figure shows that as the iron-sulfur ratio increased from 1:1 to 30:1, the residual naphthalene percentage gradually decreased from 76% to 64%, and the degradation efficiency increased with the increase of free naphthalene content. However, when the iron-sulfur ratio was further increased to 50:1, the residual naphthalene percentage increased from 64% to 71%, which somewhat hindered degradation. The optimal iron-sulfur ratio for degradation was 35:1, which improved the degradation efficiency by 12% compared to 1:1.

[0066] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for the degradation of polycyclic aromatic hydrocarbons by ferrous sulfide activated by micro-nano bubbles, characterized in that, It includes the following steps: (1) Ferrous sulfide was prepared in an anaerobic serum bottle under simulated natural in-situ conditions; (2) Add micro-nano bubbles and polycyclic aromatic hydrocarbon mother liquor to an anaerobic system containing ferrous sulfide; (3) Introduce oxygen, and micro-nano bubbles work together with ferrous sulfide to activate oxygen and remove polycyclic aromatic hydrocarbons from the system; In step (1), the preparation process of ferrous sulfide is as follows: Sodium sulfide nonahydrate and ferrous chloride tetrahydrate are used to prepare mother liquor in an anaerobic glove box. Sodium sulfide mother liquor and ferrous chloride mother liquor are added to the buffer solution of the anaerobic serum bottle in sequence. The volumes of sodium sulfide mother liquor and ferrous chloride mother liquor do not exceed 2% of the total volume of the buffer solution in the anaerobic serum bottle. The buffer solution in the serum bottle is prepared from boric acid, sodium tetraborate and sodium chloride, and ammonium chloride, magnesium chloride and calcium chloride are added to simulate natural in-situ conditions. In step (2), the preparation process of the micro-nano bubbles is as follows: micro-nano bubbles are prepared using a micro-nano bubble generator, with the gas source selected from one or a mixture of oxygen, nitrogen, and air. The total volume of pure water used in the preparation is 1500-2000 mL, the water pressure is 0.1-0.2 MPa, the preparation time is 5-10 min, and the bubble concentration in the resulting micro-nano bubble water is 10. 6 -10 9 per mL.

2. The method according to claim 1, characterized in that, The concentrations of the sodium sulfide mother liquor and the ferrous chloride mother liquor are 200 mM-2 M, respectively.

3. The method according to claim 1, characterized in that, In step (1), the sulfur concentration of the ferrous sulfide is 0.2-2 mM.

4. The method according to claim 1, characterized in that, In step (1), the iron-sulfur ratio of the ferrous sulfide is 1:1-50:

1.

5. The method according to claim 1, characterized in that, In step (2), the volume of the added micro-nano bubble water is 0.5-50% of the total volume of the solution in the anaerobic serum bottle.

6. The method according to claim 1, characterized in that, In step (2), the polycyclic aromatic hydrocarbons in the polycyclic aromatic hydrocarbon mother liquor are selected from one or more of naphthalene, acenaphthene, fluorene, phenanthrene, and anthracene. The polycyclic aromatic hydrocarbons are solubilized with ethanol and ultrasonically mixed to prepare the pollutant mother liquor.

7. The method according to claim 1, characterized in that, In step (2), after adding the polycyclic aromatic hydrocarbon mother liquor, the concentration of the polycyclic aromatic hydrocarbon mother liquor in the system is 0.5-10 mg / L.

8. The method according to claim 1, characterized in that, In step (3), the oxygen flow rate is 30-120 mL / min and the ventilation time is 30-120 s.

9. The method according to claim 1, characterized in that, In step (3), the mixing reaction time in the system is 2-6 hours.

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