CN109570222B - Method for restoring organic contaminated soil by magnetic sludge carbon enhanced electric-chemical oxidation - Google Patents
Method for restoring organic contaminated soil by magnetic sludge carbon enhanced electric-chemical oxidation Download PDFInfo
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- 239000002689 soil Substances 0.000 title claims abstract description 122
- 239000010802 sludge Substances 0.000 title claims abstract description 107
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 106
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 96
- 238000000034 method Methods 0.000 title claims abstract description 34
- 239000000126 substance Substances 0.000 title claims abstract description 14
- 230000003647 oxidation Effects 0.000 title claims abstract description 10
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 10
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 claims abstract description 50
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 claims abstract description 48
- 238000005067 remediation Methods 0.000 claims abstract description 35
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 claims abstract description 22
- 230000001590 oxidative effect Effects 0.000 claims abstract description 21
- 239000007800 oxidant agent Substances 0.000 claims abstract description 19
- 239000000843 powder Substances 0.000 claims abstract description 16
- 238000010000 carbonizing Methods 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- 238000009792 diffusion process Methods 0.000 claims abstract description 7
- 239000003814 drug Substances 0.000 claims description 28
- 238000003763 carbonization Methods 0.000 claims description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 12
- 238000006243 chemical reaction Methods 0.000 claims description 11
- 238000011049 filling Methods 0.000 claims description 11
- 229910002804 graphite Inorganic materials 0.000 claims description 10
- 239000010439 graphite Substances 0.000 claims description 10
- 229910052742 iron Inorganic materials 0.000 claims description 8
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- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 7
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- 239000001569 carbon dioxide Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000006056 electrooxidation reaction Methods 0.000 claims description 5
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 239000010935 stainless steel Substances 0.000 claims description 4
- 229910001220 stainless steel Inorganic materials 0.000 claims description 4
- 239000000956 alloy Substances 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 claims description 3
- 230000000630 rising effect Effects 0.000 claims description 3
- 238000009423 ventilation Methods 0.000 claims description 3
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- 238000005516 engineering process Methods 0.000 abstract description 10
- 230000004913 activation Effects 0.000 abstract description 9
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- JRKICGRDRMAZLK-UHFFFAOYSA-L peroxydisulfate Chemical compound [O-]S(=O)(=O)OOS([O-])(=O)=O JRKICGRDRMAZLK-UHFFFAOYSA-L 0.000 abstract description 3
- 230000015556 catabolic process Effects 0.000 abstract description 2
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- 238000002347 injection Methods 0.000 abstract 1
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- 230000000052 comparative effect Effects 0.000 description 19
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- YNPNZTXNASCQKK-UHFFFAOYSA-N phenanthrene Chemical compound C1=CC=C2C3=CC=CC=C3C=CC2=C1 YNPNZTXNASCQKK-UHFFFAOYSA-N 0.000 description 10
- BBEAQIROQSPTKN-UHFFFAOYSA-N pyrene Chemical compound C1=CC=C2C=CC3=CC=CC4=CC=C1C2=C43 BBEAQIROQSPTKN-UHFFFAOYSA-N 0.000 description 10
- 238000001994 activation Methods 0.000 description 9
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- GVEPBJHOBDJJJI-UHFFFAOYSA-N fluoranthrene Natural products C1=CC(C2=CC=CC=C22)=C3C2=CC=CC3=C1 GVEPBJHOBDJJJI-UHFFFAOYSA-N 0.000 description 5
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- 229910052681 coesite Inorganic materials 0.000 description 4
- 229910052906 cristobalite Inorganic materials 0.000 description 4
- 238000005485 electric heating Methods 0.000 description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 229910052682 stishovite Inorganic materials 0.000 description 4
- 229910052905 tridymite Inorganic materials 0.000 description 4
- 239000010405 anode material Substances 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
- 239000012159 carrier gas Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 230000001012 protector Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- MWPLVEDNUUSJAV-UHFFFAOYSA-N anthracene Chemical compound C1=CC=CC2=CC3=CC=CC=C3C=C21 MWPLVEDNUUSJAV-UHFFFAOYSA-N 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000575 pesticide Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003900 soil pollution Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006065 biodegradation reaction Methods 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
- B09C1/085—Reclamation of contaminated soil chemically electrochemically, e.g. by electrokinetics
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- Life Sciences & Earth Sciences (AREA)
- Soil Sciences (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Processing Of Solid Wastes (AREA)
- Treatment Of Sludge (AREA)
Abstract
The invention provides a method for restoring organic contaminated soil by sludge magnetic carbon-enhanced electrokinetic-chemical oxidation, which comprises the following steps: s1, carbonizing sludge to obtain sludge carbon, and then modifying the sludge carbon by using magnetite powder to prepare sludge magnetic carbon; s2, adding the sludge magnetic carbon into soil to be repaired, and uniformly stirring to obtain mixed soil; and S3, adding the oxidant into the mixed soil in an electrokinetic diffusion mode, namely adding the oxidant (sodium persulfate solution) into the restored soil in an electrokinetic injection mode. The invention utilizes the sludge magnetic carbon to efficiently catalyze sodium persulfate to generate free radicals with strong oxidizing property in the soil remediation. The method overcomes the problems of high energy consumption, secondary pollution and the like caused by the traditional persulfate activation, and simultaneously improves the degradation rate of organic pollutants. The method is suitable for ex-situ remediation and in-situ remediation, and is an organic contaminated soil remediation technology with application prospect.
Description
Technical Field
The invention relates to the technical field of polluted soil remediation, in particular to a method for remediating organic polluted soil by magnetic sludge carbon-enhanced electrokinetic-chemical oxidation.
Background
With the rapid development of urbanization and industrialization, soil pollution is becoming more serious, and the soil pollution becomes an important factor threatening human health and influencing ecological environment. Among them, organic contaminated soil is a typical pollution source which is difficult to control, and mainly results from the use of pesticides and the unreasonable discharge of chemical plants.
At present, the repair technology of the organic contaminated soil is formed and applied, and mainly comprises a physical thermal desorption repair technology, a chemical strong oxidation repair technology and a biodegradation repair technology. The physical thermal desorption remediation technology has high energy consumption and complex operation, and the problems of influencing the fertility and the structure of the soil and the like limit the application of the technology in remediation of the organic polluted soil. In bioremediation, microorganisms, plants and the like have poor resistance, are difficult to adapt to actual environment, and have long restoration period and are difficult to popularize. The chemical oxidation repair technology is relatively mature, the application effect is relatively stable, and the decomposition of organic pollutants is promoted by utilizing the strong oxidizing property of chemical reagents.
Oxidants such as persulfate, hydrogen peroxide and the like are widely applied to soil remediation, but the use and removal efficiency of a single oxidant is extremely low, and the activation is difficult, so that the waste of reagents and the secondary pollution of soil are caused. Therefore, the activation technology of the oxidant becomes the key for removing the organic pollutants, most of the processes adopt the thermal activation technology, but the energy consumption is huge, and the popularization is difficult.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to overcome the defects of difficult activation of sodium persulfate and low degradation rate of organic pollutants in the prior art and provides a method for restoring organic polluted soil by magnetic sludge carbon enhanced electrokinetic-chemical oxidation. The method utilizes the strong catalytic activity of the sludge magnetic carbon in the aspect of activating sodium persulfate, so that the efficiency of oxidizing organic pollutants by persulfate in soil is higher.
The invention provides sludge magnetic carbon which can efficiently activate an oxidant to generate free radicals with strong oxidizing property, is derived from waste, and can achieve the effect of changing waste into valuable if the sludge magnetic carbon can be applied to environmental management.
The purpose of the invention is realized by the following technical scheme:
the invention provides a method for restoring organic contaminated soil by sludge magnetic carbon-enhanced electrokinetic-chemical oxidation, which comprises the following steps:
s1, carbonizing sludge to obtain sludge carbon, and then modifying the sludge carbon by using magnetite powder to prepare sludge magnetic carbon;
s2, adding the sludge magnetic carbon into soil to be repaired, and uniformly stirring to obtain mixed soil;
and S3, adding the oxidant into the mixed soil in an electrokinetic diffusion mode. An oxidant (sodium persulfate solution) is added into the restored soil in an electric mode, and the sludge magnetic carbon is used for efficiently catalyzing sodium persulfate to generate free radicals with strong oxidizing property in the restored soil.
Preferably, in step S1, the carbonizing step includes: carbonizing the dried sludge under the conditions of heating and activated gas protection; the carbonization temperature is 500-600 ℃, the temperature rising rate is 20-30 ℃/h, and the carbonization time is 1-2 h; if the carbonization temperature is too low, carbonization is easy to occur and is not thorough; the temperature is too high, and pores are easy to melt.
Preferably, the activated gas is carbon dioxide, and the ventilation capacity of the carbon dioxide is 100-200 mL/min.
Preferably, in step S1, the modifying step includes: and (3) colliding the sludge carbon with magnetite powder in a stirring device, adding atomized concentrated sulfuric acid, and reacting to obtain the sludge magnetic carbon.
Preferably, the reaction conditions are: the reaction is carried out for 1 to 3 hours at the temperature of 70 to 80 ℃ and the rotating speed of 60 to 70 r/min. In the preparation process, concentrated sulfuric acid is used for independently releasing heat, the temperature is about 70 ℃, and if the temperature is too high, carbon demagnetization of sludge is easily caused.
Preferably, in step S1, the magnetite powder is natural magnetite powder, wherein the magnetite powder has a magnetic material content of 91%, an iron content of 68%, and Fe3O485% of Fe2O3The content is 3.2 percent and SiO2The content was 4.2%.
Preferably, the sludge magnetic carbon has a particle size of 0.01-0.02 mm and a specific surface area of 500-700 m2(ii) in terms of/g. Before use, the sludge magnetic carbon is screened to obtain the required particle size. The magnetic carbon of the sludge with the particle size can be fully contacted with the sodium persulfate, so that the activation degree of the sodium persulfate is improved.
Preferably, in step S2, the added mass of the sludge magnetic carbon is 1% to 12% of the mass of the soil to be restored.
More preferably, in step S2, the added mass of the sludge magnetic carbon is 8% to 10% of the mass of the soil to be repaired.
Preferably, in the step S2, the mixture is stirred uniformly and then is kept stand for 12-24 hours.
More preferably, in step S2, the mixture is left standing for 12 hours after being stirred uniformly.
Preferably, in step S3, the oxidizing agent is sodium persulfate solution.
Preferably, the mass concentration of the sodium persulfate solution is 5-20%.
More preferably, in step S3, the sodium persulfate solution has a mass concentration of 15% to 20%.
Preferably, in step S3, the electrokinetic diffusion is realized by an electrokinetic reactor; the electric reactor comprises a cathode, an anode, a soil remediation pool and a medicine inlet pool, wherein the anode is arranged in the center of the medicine inlet pool, and the cathode is arranged on the periphery of the medicine inlet pool; the soil remediation pool and the medicine inlet pool are coaxially arranged, the soil remediation pool is close to the anode, the medicine inlet pool is close to the cathode, and the soil remediation pool and the medicine inlet pool are separated by a plastic plate with a small hole; the soil restoration pool is used for filling soil to be restored, the medicine feeding pool is used for filling an oxidant, and the negatively charged part of the oxidant is diffused from the peripheral cathode to the central anode; the cathode and the anode are both connected with the control cabinet. The periphery of the reactor is provided with a cathode, and the center of the reactor is provided with an anode. The anode and the cathode are respectively connected with the anode and the cathode of the control cabinet. After the sodium persulfate is added into the medicine feeding pool, the medicine feeding pool and the soil remediation pool are separated by a plate with a hole. Due to S2O8 2-Negatively charged and thus diffuse from the peripheral cathode to the central anode.
Preferably, in the electromotive device, the cathode and the anode are made of one material selected from graphite, iron, stainless steel, and an alloy.
More preferably, in the electromotive device, both the cathode and the anode are made of graphite.
Preferably, in the electromotive device, a DC voltage gradient between a cathode and an anode is 50 to 200V/m.
More preferably, in the electromotive device, a DC voltage gradient between a cathode and an anode is 100 to 200V/m.
Preferably, the water content of the soil to be repaired is 20-30%. The low moisture content causes the sodium persulfate to diffuse difficultly, and the too high moisture content easily causes the short circuit of the whole electric device.
More preferably, the water content of the soil to be repaired is 20%.
Compared with the prior art, the invention has the following beneficial effects:
the method is based on that the magnetic sludge carbon catalyzes sodium persulfate to generate strong-oxidizing sulfate radicals and hydroxyl radicals, the generation rate of the radicals is high, and the organic pollutants are well removed, and particularly, compared with the traditional soil remediation method, the method has the advantages that:
1) the invention can reduce the loss of sodium persulfate and improve the removal efficiency of organic pollutants.
2) The magnetic carbon used in the invention is easy to prepare, has universality for repairing organic pollutants by cooperating with sodium persulfate, and has good removal effect on various organic pollutants.
3) The invention utilizes the process of activating the sodium persulfate by the sludge magnetic carbon to replace the traditional heating activation process, can obviously reduce the energy consumption and has higher economic value.
4) The sludge magnetic carbon material selected in the invention does not cause secondary pollution to soil, and can reduce the influence on soil property.
5) The invention is suitable for ex-situ repair and can also be used for in-situ repair.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of a soil remediation reactor apparatus;
in the figure, 1-medicine inlet pool; 2-a soil remediation pool; 3-a cathode; 4-anode.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
The invention provides a method for restoring organic contaminated soil by sludge magnetic carbon-enhanced electrokinetic-chemical oxidation, which comprises the following steps:
s1, carbonizing sludge to obtain sludge carbon, and then modifying the sludge carbon by using magnetite powder to prepare sludge magnetic carbon;
s2, adding the sludge magnetic carbon into soil to be repaired, and uniformly stirring to obtain mixed soil;
and S3, adding the oxidant into the mixed soil in an electrokinetic diffusion mode.
In step S1, the carbonizing step includes: carbonizing the dried sludge under the conditions of heating and activated gas protection; the carbonization temperature is 500-600 ℃, the temperature rising rate is 20-30 ℃/h, and the carbonization time is 1-2 h; the activated gas is carbon dioxide, and the ventilation capacity of the carbon dioxide is 100-200 mL/min.
In step S1, the modifying step includes: and (3) colliding the sludge carbon with magnetite powder in a stirring device, adding atomized concentrated sulfuric acid, and reacting to obtain the sludge magnetic carbon. The reaction conditions are as follows: the reaction is carried out for 1 to 3 hours at the temperature of 70 to 80 ℃ and the rotating speed of 60 to 70 r/min.
In step S1, the sludge magnetic carbon has a particle size of 0.01-0.02 mm and a specific surface area of 500-700 m2/g。
In the step S2, the adding mass of the sludge magnetic carbon is 1-12% of the mass of the soil to be repaired.
In step S3, the oxidizing agent is a sodium persulfate solution; the mass concentration of the sodium persulfate solution is 5-20%.
In step S3, the electrokinetic diffusion is realized by an electrokinetic reactor;
the electric reactor comprises a cathode 3, an anode 4, a soil remediation pool 2 and a medicine inlet pool 1, wherein the anode 4 is arranged in the center of the medicine inlet pool 1, and the cathode 3 is arranged on the periphery of the medicine inlet pool 1, as shown in fig. 1;
the soil remediation pool 2 and the medicine inlet pool 1 are coaxially arranged, the soil remediation pool 2 is close to the anode 4, the medicine inlet pool 1 is close to the cathode 3, and the soil remediation pool 2 and the medicine inlet pool 1 are separated by a plastic plate with a small hole;
the soil remediation pool 2 is used for filling soil to be remediated, the pesticide inlet pool 1 is used for filling an oxidant, and the negatively charged part of the oxidant diffuses from the peripheral cathode 3 to the central anode 4;
and the cathode 3 and the anode 4 are both connected with the control cabinet.
In the electric device, the cathode 3 and the anode 4 are respectively made of one material selected from graphite, iron, stainless steel and alloy; in the electric device, the DC voltage gradient between the cathode 3 and the anode 4 is 50-200V/m.
The water content of the soil to be repaired is 20-30%.
Example 1
The embodiment provides a method for restoring organic contaminated soil by magnetic sludge carbon-enhanced electro-chemical oxidation.
1. Preparing the sludge magnetic carbon.
Preparing sludge carbon: the sludge carbon is carbonized through dried sludge under the condition that nitrogen is used as an activating gas carrier gas and a carbonization protector, the carbonization temperature is 500 ℃, the temperature rise rate is 20 ℃/h, and the carbonization time is 1.5 h.
Modification of sludge carbon: the modification of the sludge carbon is to use natural magnetite powder as a modified material, wherein the content of magnetic substances is 91 percent, the content of iron is 68 percent, and Fe3O485% of Fe2O3The content is 3.2 percent and SiO2The content was 4.2%. Mixing sludge carbon with magnetite powderColliding in a rotary stirring device, adding concentrated sulfuric acid in an atomized state, and reacting for 2 hours at the temperature of 80 ℃ and the rotating speed of 70r/min to obtain the sludge magnetic carbon. The prepared sludge magnetic carbon has a particle size of 0.02mm and a specific surface area of 500m2/g。
2. The influence of the adding amount of the sludge magnetic carbon on the removal efficiency of the sodium persulfate PAHs catalyzed by the sludge magnetic carbon is examined by taking the artificially polluted soil as a research object.
Phenanthrene and pyrene are artificially added into the pollution-free soil according to the proportion of 100mg/kg for pollution. Adding sludge magnetic carbon into the soil according to the mass ratio of 1%, 3%, 5%, 8% and 10% of the sludge magnetic carbon to the soil, uniformly mixing, and standing for 12 hours. And (3) moving the polluted soil into a soil remediation pool with the round bottom radius of 0.5m and the depth of 0.7m, and filling the soil to 0.5 m. Adding water to control the water content of the soil to be 20%. The mass concentration of the sodium persulfate is fixed to be 10%, and a sodium persulfate solution is added into a medicine inlet pool. The anode material is graphite, and the cathode material is graphite. The control cabinet provides a DC voltage gradient of 200V/m, and a DC electric field is applied between the electrodes for repair. After 10d of reaction, soil with different sections (the distances from the cathode are 0m,0.3m,0.5m are marked as S1, S2 and S3) is taken for PAHs concentration detection. The results of the effect of the addition amount of the magnetic carbon in different sludge on the efficiency of catalyzing sodium persulfate to remove PAHs are shown in Table 1.
TABLE 1 influence of the amount of magnetic carbon added to the sludge on the efficiency of the sludge in catalyzing the removal of PAHs from sodium persulfate (unit: mg/kg)
As can be seen from Table 1, when the mass ratio of the sludge magnetic carbon to the soil is 8% -10%, the removal rate of PAHs can achieve good effect.
Example 2
The embodiment provides a method for restoring organic contaminated soil by magnetic sludge carbon-enhanced electro-chemical oxidation.
1. Preparing the sludge magnetic carbon.
Preparing sludge carbon: the sludge carbon is carbonized through dried sludge under the condition that nitrogen is used as an activating gas carrier gas and a carbonization protector, the carbonization temperature is 600 ℃, the temperature rise rate is 20 ℃/h, and the carbonization time is 1 h.
Modification of sludge carbon: the modification of the sludge carbon is to use natural magnetite powder as a modified material, wherein the content of magnetic substances is 91 percent, the content of iron is 68 percent, and Fe3O485% of Fe2O3The content is 3.2 percent and SiO2The content was 4.2%. And (3) colliding the sludge carbon with magnetite powder in a rotary stirring device, adding concentrated sulfuric acid in an atomized state, and reacting for 2 hours at the temperature of 75 ℃ and the rotating speed of 70r/min to obtain the sludge magnetic carbon. The prepared sludge magnetic carbon has the particle size of 0.02mm and the specific surface area of 550m2/g。
2. The influence of the mass concentration of sodium persulfate on the removal efficiency of PAHs is examined by taking the actual PAHs contaminated site soil as a research object.
Adding sludge magnetic carbon with the mass ratio of 10% to the soil into the restored soil, uniformly mixing, and standing for 12 hours. And (4) moving the remediation soil into a soil remediation pool with the round bottom radius of 0.5m and the depth of 0.7m, and filling the soil to 0.5 m. Adding water to control the water content of the soil to be 20%. The mass concentration of the sodium persulfate is respectively set to 5%, 10%, 15% and 20%, and a sodium persulfate solution is added into the medicine feeding pool. The anode material is graphite, and the cathode material is graphite. The control cabinet provides a DC voltage gradient of 200V/m, and a DC electric field is applied between the electrodes for repair. After 10d of reaction, soil with different sections (the distances from the cathode are 0m,0.3m,0.5m are marked as S1, S2 and S3) is taken for PAHs concentration detection. The results of the different sodium persulfate mass concentrations on the removal efficiency of PAHs are shown in Table 2.
TABLE 2 influence of the sodium persulfate Mass concentration on the removal efficiency of PAHs (unit: mg/kg)
As can be seen from Table 2, the concentrations of organic pollutants in the soil are 356mg/kg phenanthrene, 251mg/kg pyrene and 67mg/kg anthracene. When the mass concentration of the sodium persulfate is 10-20%, the removal rate of the PAHs can achieve good effect. When the mass concentration of the sodium persulfate reaches more than 15%, the removal effect of the PAHs is basically saturated, and the mass concentration of the sodium persulfate is preferably 15-20%. The mass concentration of the sodium persulfate can be properly adjusted according to different concentrations and types of organic pollutants.
Example 3
The embodiment provides a method for restoring organic contaminated soil by magnetic sludge carbon-enhanced electro-chemical oxidation.
1. Preparing the sludge magnetic carbon.
Preparing sludge carbon: the sludge carbon is carbonized through dried sludge under the condition that nitrogen is used as an activating gas carrier gas and a carbonization protector, the carbonization temperature is 550 ℃, the temperature rise rate is 20 ℃/h, and the carbonization time is 2 h.
Modification of sludge carbon: the modification of the sludge carbon is to use natural magnetite powder as a modified material, wherein the content of magnetic substances is 91 percent, the content of iron is 68 percent, and Fe3O485% of Fe2O3The content is 3.2 percent and SiO2The content was 4.2%. And (3) colliding the sludge carbon with magnetite powder in a rotary stirring device, adding concentrated sulfuric acid in an atomized state, and reacting for 2 hours at the temperature of 70 ℃ and the rotating speed of 70r/min to obtain the sludge magnetic carbon. The prepared sludge magnetic carbon has a particle size of 0.02mm and a specific surface area of 600m2/g。
2. Phenanthrene and pyrene are artificially added into the pollution-free soil according to the proportion of 100mg/kg for pollution. Adding sludge magnetic carbon into the soil according to the mass ratio of the sludge magnetic carbon to the soil being 8%, uniformly mixing, and standing for 24 hours. And (3) moving the polluted soil into a soil remediation pool with the round bottom radius of 0.5m and the depth of 0.7m, and filling the soil to 0.5 m. Adding water to control the water content of the soil to be 25%. The mass concentration of the sodium persulfate is 15 percent, and a sodium persulfate solution is added into the medicine feeding pool. The cathode material is iron, and the cathode material is stainless steel. The control cabinet provides a DC voltage gradient of 150V/m, and a DC electric field is applied between the electrodes for repair. After 10d of reaction, soil with different sections (the distances from the cathode are 0m,0.3m,0.5m are marked as S1, S2 and S3) is taken for PAHs concentration detection. The results of the effect of adding magnetic carbon to the sludge on the efficiency of catalyzing sodium persulfate to remove PAHs are shown in Table 3.
TABLE 3 removal efficiency of PAHs (unit: mg/kg)
In conclusion, the method utilizes the magnetic carbon of the sludge to activate the sodium persulfate so as to generate strong oxidizing free radicals in the soil remediation, and has very high capability of removing organic pollutants. The method can effectively overcome the problems of low removal rate, excessive energy consumption, easy secondary pollution and the like in the traditional repair method.
Comparative example 1
This comparative example provides a method of remediating organically-contaminated soil.
Phenanthrene and pyrene are artificially added into the pollution-free soil according to the proportion of 100mg/kg for pollution. And (3) moving the polluted soil into a soil remediation pool with the round bottom radius of 0.5m and the depth of 0.7m, and filling the soil to 0.5 m. Adding water to control the water content of the soil to be 20%. The mass concentration of the sodium persulfate is fixed to be 10%, and a sodium persulfate solution is added into a medicine inlet pool. The anode material is graphite, and the cathode material is graphite. The control cabinet provides a DC voltage gradient of 200V/m, and a DC electric field is applied between the electrodes for repair. After 10d of reaction, soil with different sections (the distances from the cathode are 0m,0.3m,0.5m are marked as S1, S2 and S3) is taken for PAHs concentration detection. The removal efficiency results for PAHs with sodium persulfate alone are shown in table 4.
TABLE 4 removal efficiency of sodium persulfate alone for PAHs
Comparative example 2
This comparative example provides a method of remediating organically-contaminated soil.
Phenanthrene and pyrene are artificially added into the pollution-free soil according to the proportion of 100mg/kg for pollution. And (3) moving the polluted soil into a soil remediation pool with the round bottom radius of 0.5m and the depth of 0.7m, and filling the soil to 0.5 m. Adding water to control the water content of the soil to be 20%. The mass concentration of the sodium persulfate is fixed to be 10%, and a sodium persulfate solution is added into a medicine inlet pool. The temperature in the soil is maintained to be 50-70 ℃ by inserting an electric heating rod into the soil. The control cabinet provides a DC voltage gradient of 200V/m, and a DC electric field is applied between the electrodes for repair. After 10d of reaction, soil with different sections (the distances from the cathode are 0m,0.3m,0.5m are marked as S1, S2 and S3) is taken for PAHs concentration detection. The results of the removal efficiency of PAHs by electrically heating activated sodium persulfate are shown in table 5.
TABLE 5 removal efficiency of PAHs by electric heating activated sodium persulfate
Although the repairing effect of comparative example 2 is superior to that of example 1 in which the mass ratio of magnetic carbon to soil in sludge is 1%. However, in comparative example 2, sodium persulfate was activated by electric heating which is commonly used at the present stage, and although a good removal effect can be achieved, the required energy consumption is extremely large. The magnetic carbon activation of the sludge can save the activation cost and simultaneously achieve the same effect as the electric heating activation.
In conclusion, the invention can greatly improve the removal efficiency of the organic pollutants, even if the removal efficiency of the organic pollutants can be improved by electrical heating activation, the energy consumption is huge, and the invention has good application prospect in consideration of the economic benefit of the process.
Comparative example 3
This comparative example provides a method of remediating organically-contaminated soil, the steps of which are substantially the same as in example 3, except that: in the comparative example, after the sodium persulfate solution is added into the feeding tank, the control cabinet does not provide a direct-current voltage gradient, and a direct-current electric field is not applied between the two electrodes, so that the repair is directly carried out.
Comparative example 4
This comparative example provides a method of remediating organically-contaminated soil, the steps of which are substantially the same as in example 3, except that: in this comparative example, the carbonization temperature was 650 ℃ in the preparation of the sludge carbon.
Comparative example 5
This comparative example provides a method of remediating organically-contaminated soil, the steps of which are substantially the same as in example 3, except that: in the comparative example, when sludge carbon is modified, ferroferric oxide is used as a modified material to replace natural magnetite powder.
Comparative example 6
This comparative example provides a method of remediating organically-contaminated soil, the steps of which are substantially the same as in example 3, except that: in this comparative example, hydrogen peroxide was used instead of the sodium persulfate solution.
TABLE 6 removal efficiency of comparative examples 3-6 on PAHs
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (6)
1. A method for restoring organic contaminated soil by sludge magnetic carbon-enhanced electrokinetic-chemical oxidation is characterized by comprising the following steps:
s1, carbonizing sludge to obtain sludge carbon, and then modifying the sludge carbon by using magnetite powder to prepare sludge magnetic carbon;
s2, adding the sludge magnetic carbon into soil to be repaired, and uniformly stirring to obtain mixed soil;
s3, adding an oxidant into the mixed soil in an electrokinetic diffusion mode;
in step S1, the carbonizing step includes: carbonizing the dried sludge under the conditions of heating and activated gas protection; the carbonization temperature is 500-600 ℃, the temperature rising rate is 20-30 ℃/h, and the carbonization time is 1-2 h; the activated gas is carbon dioxide, and the ventilation capacity of the carbon dioxide is 100-200 mL/min;
in step S1, the modifying step includes: the sludge carbon and magnetite powder are collided in a stirring device, atomized concentrated sulfuric acid is added, and the sludge magnetic carbon is prepared after reaction;
the reaction conditions are as follows: reacting for 1-3 h at the temperature of 70-80 ℃ and the rotating speed of 60-70 r/min;
in step S3, the oxidizing agent is a sodium persulfate solution; the mass concentration of the sodium persulfate solution is 5-20%.
2. The method for restoring organically-polluted soil through sludge magnetic carbon-enhanced electro-chemical-oxidative remediation as claimed in claim 1, wherein the sludge magnetic carbon has a particle size of 0.01mm to 0.02mm and a specific surface area of 500m to 700m2/g。
3. The method for remediating organically-polluted soil through sludge magnetic carbon enhanced electro-chemical oxidation as claimed in claim 1, wherein in step S2, the added mass of the sludge magnetic carbon is 1-12% of the mass of the soil to be remediated.
4. The method for remediating organically-polluted soil through sludge magnetic carbon-enhanced electro-chemical-oxidative remediation, as claimed in claim 1, wherein in step S3, the electro-kinetic diffusion is achieved through an electro-kinetic reactor;
the electric reactor comprises a cathode, an anode, a soil remediation pool and a medicine inlet pool, wherein the anode is arranged in the center of the medicine inlet pool, and the cathode is arranged on the periphery of the medicine inlet pool;
the soil remediation pool and the medicine inlet pool are coaxially arranged, the soil remediation pool is close to the anode, the medicine inlet pool is close to the cathode, and the soil remediation pool and the medicine inlet pool are separated by a plastic plate with a small hole;
the soil restoration pool is used for filling soil to be restored, the medicine feeding pool is used for filling an oxidant, and the negatively charged part of the oxidant is diffused from the peripheral cathode to the central anode;
the cathode and the anode are both connected with the control cabinet.
5. The method for remediating organically-polluted soil through sludge magnetic carbon-enhanced electro-chemical-oxidation as claimed in claim 4, wherein in the electro-kinetic reactor, the cathode and the anode are respectively made of one material selected from graphite, iron, stainless steel and alloy; in the electric reactor, the direct current voltage gradient between the cathode and the anode is 50-200V/m.
6. The method for remediating organically-polluted soil through magnetic carbon-enhanced electro-chemical-oxidative remediation of sludge as claimed in claim 1, wherein the water content in the soil to be remediated is 20% to 30%.
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