CN115672968A - A Method for Ultrasonic Enhanced Electric Remediation of Phenanthrene Contaminated Soil - Google Patents

Abstract

The invention relates to a method for ultrasonically intensified electric restoration of phenanthrene-contaminated soil, which has the following steps: (1), placing the phenanthrene-contaminated soil in the soil sample chamber of an electric restoration device, and fully soaking the soil for 24 hours by adding 0.01mol/L NaCl solution , to achieve water and soil balance, and then add oxidant and surfactant to the anode chamber of the electric restoration device; (2), insert two ultrasonic probes into both sides of the soil center to generate ultrasonic waves, start the DC power supply and the ultrasonic power supply for ultrasonic enhanced electric restoration Philippine polluted soil. The present invention utilizes the combination treatment method of ultrasonic enhanced electrodynamic restoration + advanced oxidation and surfactant to effectively improve the removal efficiency of electrodynamic restoration of phenanthrene pollution, enhance the transfer and oxidation capacity of oxidants, improve the desorption capacity of phenanthrene in soil, and realize Good remediation effect on organically polluted soil with low permeability.

Description

A Method for Ultrasonic Enhanced Electrokinetic Remediation of Philippine Contaminated Soil

technical field

The invention relates to the technical field of remediation of organic polluted soil, in particular to a method for ultrasonically enhanced electric remediation of phenanthrene polluted soil.

Background technique

Polycyclic aromatic hydrocarbons (PAHs), as a typical organic pollutant, ubiquitously exist in the air and are mainly produced by natural fires, incomplete combustion of coal and petroleum fuels. Once in the soil, they will remain in the soil for a long time due to their strong hydrophobicity and persistence.

Among the known soil remediation technologies, in-situ advanced oxidation has attracted widespread attention because of its rapidity and high efficiency. Although the oxidant has a strong ability to remove pollutants, due to the low permeability of the soil, there are certain limitations in the transfer of the oxidant. Therefore, some studies have pointed out that adding a DC electric field at both ends of the soil can transfer the oxidant to other parts of the soil through electroosmotic flow, electromigration, etc., and enhancing the contact with pollutants can improve the removal rate. Therefore, electrokinetic combined oxidizers are an effective method for remediation of low-permeability organic-contaminated soils. As for PAHs, due to their strong hydrophobicity, most of them exist in the adsorbed state in soil, which makes the effect of electroosmotic flow negligible. Therefore, some techniques are needed to improve the solubility of PAHs, such as adding surfactants to convert PAHs from the adsorbed state to the dissolved state through their micellar solubilization, and migrate out of the soil through electroosmotic flow. On the other hand, the application of ultrasound in soil remediation is becoming more and more extensive. Increasing ultrasonic energy in contaminated soil can increase pollutant desorption as well as soil porosity and permeability through cavitation. In addition, ultrasound can activate oxidants to generate stronger oxidative free radicals, and it can also generate strong oxidative free radicals to remove organic pollutants.

Contents of the invention

The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, the present invention provides a method for ultrasonically enhanced electrodynamic remediation of phenanthrene-contaminated soil, so as to improve the removal efficiency of electrodynamic remediation of phenanthrene pollution, enhance the transfer and oxidation capacity of oxidant , Improve the desorption capacity of phenanthrene in the soil.

The technical solution adopted by the present invention to solve the technical problems is: a method for ultrasonically enhanced electric repair of phenanthrene polluted soil, which has the following steps:

(1) Put the phenanthrene-contaminated soil in the soil sample chamber of the electrodynamic restoration device, fully infiltrate the soil by adding 0.01mol/L NaCl solution for 24 hours to achieve water and soil balance, and then add oxidant and surfactant to the anode chamber of the electrodynamic restoration device agent;

(2) Insert two ultrasonic probes into both sides of the soil center to generate ultrasonic waves, start the DC power supply and the ultrasonic power supply to carry out ultrasonic enhanced electric repair of the polluted soil.

Preferably, in step 1, the concentration of phenanthrene-contaminated soil is 300-500 mg/kg.

Specifically, the oxidizing agent in the described step 1 is any one of sodium persulfate or hydrogen peroxide or potassium permanganate; the surfactant is Tween 80 or Triton X-100 or rhamnolipid any of the

Further, the oxidizing agent is sodium persulfate with a concentration of 10mmol/L; the surfactant is Tween 80 with a concentration of 10g/L.

Preferably, the voltage gradient of the electrokinetic restoration in step 2 is 1.5V/cm, the working power of the ultrasonic probe is 100W, the vibration frequency generated by the ultrasonic probe is 30-50KHz, and the working time is 10min/time.

Preferably, the electrode material in the electrokinetic repair device is an inert graphite electrode, and the electrokinetic repair time is 10d.

The beneficial effect of the present invention is: the present invention utilizes the combined treatment mode of ultrasonic enhanced electric repair + advanced oxidation and surfactant to enhance the removal efficiency of phenanthrene-contaminated soil.

(1) The addition of surfactants desorbs more phenanthrene from the soil and migrates out of the soil column through mechanisms such as electroosmotic flow and electromigration. In addition, the transmission and diffusion of Na ₂ S ₂ O ₈ into the soil increases its The range and time of contact with phenanthrene in the soil greatly improved the removal efficiency of phenanthrene.

(2) An ultrasonic probe is installed in the soil. On the one hand, the ultrasonic energy generated by it can destroy the mechanical vibration of the liquid film and air bubbles formed in the soil pores during the electroosmotic process, thereby increasing the space for the pore solution to flow and enhancing the electroosmotic flow. ; On the other hand, the cavitation effect produced by ultrasonic waves can significantly improve the desorption capacity of phenanthrene in soil, and can enhance the removal of phenanthrene pollution by electric remediation together with the micellar solubilization of surfactants.

(3) The ultrasonic waves generated by the ultrasonic probe can also activate Na ₂ S ₂ O ₈ to produce sulfate radicals (SO ₄ ^- ) with stronger oxidizing properties, which can also generate strong oxidizing free radicals to oxidize Remove phenanthrene from soil.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a schematic structural view of an electric restoration device adopted in the present invention.

In the figure: 1. DC power supply, 2. Anode chamber, 3. Cathode chamber, 4. Inert graphite electrode, 5. Inert graphite electrode, 6. Soil remediation chamber, 7. Ultrasonic power supply, 8. Ultrasonic probe, 9. Ultrasonic probe .

Detailed ways

The present invention is described in further detail now in conjunction with accompanying drawing. These drawings are all simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, so they only show the configurations related to the present invention.

As shown in FIG. 1 , a schematic structural diagram of an electric restoration device used in a method for ultrasonically enhanced electrodynamic restoration of phenanthrene-contaminated soil.

The electric restoration device includes an experimental box made of acrylic plexiglass. The left side of the experimental box is the anode chamber 2, the right side is the cathode chamber 3, and the soil restoration chamber 6 is between the anode chamber 2 and the cathode chamber 3. , the test box is equipped with a DC power supply 1 and an ultrasonic power supply 7, an inert graphite electrode 4 is placed in the anode chamber 2, an inert graphite electrode 5 is placed in the cathode chamber 3, and the soil restoration chamber 6 is divided into S1～S5 from left to right Five sections for data checking after experiments. The inert graphite electrode 4 and the inert graphite electrode 5 are respectively connected to two ends of the DC power supply 1, and the DC power supply 1 applies a voltage gradient of 1.5 V/cm to the two ends of the inert graphite electrode 4 and the inert graphite electrode 5 during operation. An ultrasonic probe 8 and an ultrasonic probe 9 are respectively installed on both sides of the soil center. The ultrasonic probe 8 and the ultrasonic probe 9 are respectively electrically connected to the ultrasonic power supply 7 to generate ultrasonic waves. The maximum ultrasonic power is 100W and the maximum vibration frequency is 50KHz.

Example 1:

Configuration of phenanthrene-contaminated soil: Weigh 0.500g of phenanthrene with a purity of 97% and dissolve it in acetone, then weigh 1kg of the original soil and mix it with the prepared phenanthrene solution evenly, then put it in a fume hood for 3 days, and stir it three times a day during this period In order to ensure that the excess acetone is volatilized, the prepared phenanthrene mixed mud is aged for 60 days.

Electrokinetic experiment: first place the configured phenanthrene-contaminated soil in the soil remediation chamber 6, and add 0.01mol/L NaCl solution to the anode chamber 2 and cathode chamber 3 to fully soak the soil for 1 day to obtain saturated phenanthrene-contaminated wet soil; Add 10mmol/L Na ₂ S ₂ O ₈ solution in the anode chamber 2 to carry out electric repair, and the electric repair time is 10 days; at the same time, turn on the ultrasonic power supply 7, the ultrasonic working power of ultrasonic probe 8 and ultrasonic probe 9 is 100W, and the oscillation frequency is 50KHz, working time is 10min/time. On the first day, the ultrasound was performed for one hour every six hours, and the ultrasound was performed for 3 hours; after that, the ultrasound was performed for one hour every day, and the ultrasound was performed for a total of 10 days. After the electrical restoration, the DC power supply 1 and the ultrasonic power supply 7 were turned off, and the soil was taken out for freeze-drying-ultrasonic extraction to measure the phenanthrene content. The average removal rate of phenanthrene was measured to be 55.38%.

Comparative example 1:

The difference between Comparative Example 1 and Example 1 is that the ultrasonic probe 8 and the ultrasonic probe 9 are not activated, and other conditions remain unchanged.

Example 2:

Configuration of phenanthrene-contaminated soil: Weigh 0.500g of phenanthrene with a purity of 97% and dissolve it in acetone, then weigh 1kg of the original soil and mix it with the prepared phenanthrene solution, then put it in a fume hood for 3 days, and stir it three times a day during this period In order to ensure that the excess acetone is volatilized, the prepared phenanthrene mixed mud is aged for 60 days.

Electrokinetic experiment: first place the configured phenanthrene-contaminated soil in the soil remediation chamber 6, and add 0.01mol/L NaCl solution to the anode chamber 2 and cathode chamber 3 respectively to fully infiltrate the soil for 1 day to obtain saturated phenanthrene-contaminated wet soil; Add 10g/L Tween80 solution into the anode chamber 2 for electric repair, and the electric repair time is 10 days; at the same time, turn on the ultrasonic power supply 7, the ultrasonic working power of ultrasonic probe 8 and ultrasonic probe 9 is 100W, the oscillation frequency is 50KHz, and the working time is 10min /Second-rate. On the first day, the ultrasound was performed for one hour every six hours, and the ultrasound was performed for 3 hours; after that, the ultrasound was performed for one hour every day, and the ultrasound was performed for a total of 10 days. After the electric restoration, the DC power supply 1 and the ultrasonic power supply 7 were turned off, and the soil was taken out for freeze-drying-ultrasonic extraction to measure the phenanthrene content, and the average removal rate of phenanthrene was measured to be 59.27%.

Comparative example 2:

The difference between Comparative Example 2 and Example 2 is that the ultrasonic probe 8 and the ultrasonic probe 9 are not activated, and other conditions remain unchanged.

Example 3:

Configuration of phenanthrene-contaminated soil: Weigh 0.500g of phenanthrene with a purity of 97% and dissolve it in acetone, then weigh 1kg of the original soil and mix it with the prepared phenanthrene solution, then put it in a fume hood for 3 days, and stir it three times a day during this period In order to ensure that the excess acetone is volatilized, the prepared phenanthrene mixed mud is aged for 60 days.

Electrokinetic experiment: first place the configured phenanthrene-contaminated soil in the soil remediation chamber 6, and add 0.01mol/L NaCl solution to the anode chamber 2 and cathode chamber 3 to fully soak the soil for 1 day to obtain saturated phenanthrene-contaminated wet soil; First add 10g/L Tween80 solution into the anode chamber 2 for electric repair, then add 10mmol/L Na ₂ S ₂ O ₈ solution to the anode chamber 2 to continue electrolysis, and the electric repair time is 10d; at the same time, turn on the ultrasonic power supply 7, and the ultrasonic The ultrasonic working power of the probe 8 and the ultrasonic probe 9 is 100W, the oscillation frequency is 50KHz, and the working time is 10min/time. On the first day, the ultrasound was performed for one hour every six hours, and the ultrasound was performed for 3 hours; after that, the ultrasound was performed for one hour every day, and the ultrasound was performed for a total of 10 days. After the electrical restoration, the DC power supply 1 and the ultrasonic power supply 7 were turned off, and the soil was taken out for freeze-drying-ultrasonic extraction to measure the phenanthrene content. The average removal rate of phenanthrene was measured to be 80.18%.

The details of the above example schemes are shown in Table 1.

Table 1

According to the removal effect of the phenanthrene pollution in Example 1 and Comparative Example 1, the ultrasonic-enhanced electrodynamic remediation of phenanthrene pollution in the test of electrodynamic persulfate remediation of phenanthrene-contaminated soil in Example 1, the removal rate of phenanthrene can reach 55.38%, which is The removal rate (29.33%) of phenanthrene in Comparative Example 1 without ultrasonic treatment is much higher. This is because the cavitation effect produced by ultrasonic waves can significantly improve the desorption capacity of phenanthrene in the soil, and promote more adsorption states in the soil. The phenanthrene is transformed into dissolved phenanthrene, which enables the Na ₂ S ₂ O ₈ transported by the electroosmotic flow to contact with more phenanthrene for in-situ degradation and improve the removal rate of phenanthrene. In addition, ultrasound can also activate Na ₂ S ₂ O ₈ to produce sulfate radicals (SO ₄ ^- ·) with stronger oxidative properties, which can also generate strong oxidizing free radicals to oxidize and remove phenanthrene in soil.

According to the electrodynamic surfactant repairing phenanthrene pollution test after ultrasonic strengthening in Example 2, the removal rate of phenanthrene reached 59.27%, which is slightly higher than the removal rate (37.5%) of phenanthrene in comparative example 2 without ultrasonic , this is because the cavitation effect generated by ultrasonic waves can significantly improve the desorption capacity of phenanthrene in soil, and together with the micellar solubilization effect generated by Tween80 solution, it can enhance the removal of phenanthrene pollution by electrokinetic remediation. In addition, the surfactant will produce foaming phenomenon under electrodynamic restoration, thereby blocking the soil pores. However, the addition of ultrasonic energy can destroy the liquid film and mechanical vibration of the air bubbles formed in the soil pores during the electroosmotic process, thereby increasing the flow of the pore solution. Space, enhanced electroosmotic flow, thereby increasing the removal rate of phenanthrene.

Example 3 combines the schemes of Examples 1 and 2, adding Tween80 solution and Na ₂ S ₂ O ₈ solution in the anode chamber 2, and electrodynamically repairing the phenanthrene-contaminated soil through ultrasonic enhancement, and the removal rate of phenanthrene reaches 80.18%. . This is due to the synergistic effect of ultrasound, Tween80 and Na ₂ S ₂ O ₈ , the surfactant is responsible for transferring more adsorbed phenanthrene into the cavity of the micelles it produces, and Na ₂ S ₂ O ₈ is responsible for transferring It is removed by oxidation. Ultrasound is responsible for strengthening the desorption capacity of phenanthrene in soil together with surfactants; destroying the vacuole phenomenon produced by surfactants in soil and enhancing the availability of pores; secondly, it can activate Na ₂ S ₂ O ₈ to produce more oxidative capacity. The strong sulfate radical (SO ₄ ⁻ ·) reacts with the dissolved phenanthrene in the cavity of the micelles. From the maximum extent to improve the removal rate of phenanthrene.

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

Claims (6)

1. a method for supersonic-enhanced electrodynamic remediation of phenanthrene-contaminated soil, characterized in that: it has the following steps: (1) Put the phenanthrene-contaminated soil in the soil sample chamber of the electrodynamic restoration device, fully infiltrate the soil by adding 0.01mol/L NaCl solution for 24 hours to achieve water and soil balance, and then add oxidant and surfactant to the anode chamber of the electrodynamic restoration device agent; (2) Insert two ultrasonic probes into both sides of the soil center to generate ultrasonic waves, start the DC power supply and the ultrasonic power supply to carry out ultrasonic enhanced electric repair of the polluted soil. 2. The method for ultrasonically enhanced electrodynamic remediation of phenanthrene-contaminated soil as claimed in claim 1, characterized in that: in said step 1, the concentration of phenanthrene-contaminated soil is 300-500 mg/kg. 3. the method for supersonic enhanced electric repair phenanthrene polluted soil as claimed in claim 1, is characterized in that: the oxidant in described step 1 is any one in sodium persulfate or hydrogen peroxide or potassium permanganate; The surfactant is any one of Tween 80, Triton X-100 or rhamnolipid. 4. the method for supersonic strengthening electric repair phenanthrene polluted soil as claimed in claim 3 is characterized in that: described oxidizing agent is sodium persulfate, and concentration is 10mmol/L; Surfactant is Tween 80, and concentration is 10g/L L. 5. The method for ultrasonically enhanced electric restoration of phenanthrene-contaminated soil as claimed in claim 1, characterized in that: the voltage gradient of electric restoration in the described step 2 is 1.5V/cm, the operating power of the ultrasonic probe is 100W, and the ultrasonic probe The generated vibration frequency is 30-50KHz, and the working time is 10min/time. 6. The method for ultrasonically enhanced electric restoration of phenanthrene-contaminated soil as claimed in claim 1, characterized in that: the electrode material in the electric restoration device is an inert graphite electrode, and the electric restoration time is 10 days.

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