CN109940032B - Remediation method of organic pollutant-heavy metal composite contaminated soil - Google Patents
Remediation method of organic pollutant-heavy metal composite contaminated soil Download PDFInfo
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Abstract
The invention relates to the technical field of soil remediation, in particular to a remediation method of organic pollutant-heavy metal combined polluted soil, which comprises the following steps: adding modified chitosan into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, pouring the soil thoroughly, then applying active coal gangue powder, and uniformly mixing the active coal gangue powder with the soil to realize effective remediation of the organic pollutant-heavy metal composite polluted soil. The invention can effectively degrade organic pollutants in the polluted soil and passivate heavy metals in the soil, thereby achieving the aim of restoring the soil and having short restoration period.
Description
Technical Field
The invention relates to the technical field of soil remediation, in particular to a remediation method of organic pollutant-heavy metal combined polluted soil.
Background
The soil is a loose surface layer which has fertility on the surface of the land and can grow plants, the thickness of the soil is about 2m generally, the soil not only provides mechanical support capability for the growth of the plants, but also provides fertility factors such as water, fertilizer, gas, heat and the like required by the growth and development of the plants, and is also the foundation of human activities. However, with the rapid development of social economy and industry, solid wastes are continuously piled and dumped to the surface of soil, harmful wastewater continuously permeates into the soil, harmful gas and floating dust in the atmosphere continuously fall into the soil along with rainwater, so that soil pollution is caused, and the soil pollution is more and more serious.
Existing soil pollution can be roughly divided into two categories, inorganic pollutants and organic pollutants. Inorganic pollutants include the pollution of substances such as acid, alkali, heavy metal and the like; the organic pollutants mainly comprise organic pesticides, phenols, polycyclic aromatic hydrocarbons and other substances. Among soil pollutants, heavy metal pollution and polycyclic aromatic hydrocarbon pollution are two typical pollutants, particularly heavy metal chromium and organic pollutant benzopyrene are the most common pollutants, so that how to degrade the organic pollutants and passivate the heavy metals becomes a main subject of polluted soil remediation.
In order to solve the problems, the inventor searches the prior art, and discloses a method for repairing heavy metals and organic pollutants in agricultural soil in Chinese patent publication No. CN108672485A, wherein biochar raw materials are washed by water to remove surface adhesive substances and then are naturally dried; crushing the air-dried biomass, and pyrolyzing in a pyrolysis furnace; wrapping the pyrolyzed biochar with a plastic mesh fabric with holes for forming to prepare biochar active filler, and burying the biochar active filler in soil to be repaired; dissolving percarbonate in water to prepare percarbonate leachate, and leaching the soil to be repaired periodically. According to the scheme, heavy metals in soil are adsorbed by the biochar, organic pollutants in the soil are degraded by the carbonate, and the purpose of removing the heavy metals and the organic pollutants in the soil is finally achieved. However, the adsorption capacity of the biochar active filler generated by pyrolysis is limited, and only heavy metal of soil can be adsorbed, organic pollutant adsorption treatment cannot be realized, carbonate is applied to the ground in a spraying mode, a large amount of recovery can occur in the process of permeating the soil through the carbonate, the capacity of the carbonate for repairing the soil is influenced, meanwhile, the carbonate treats the organic pollutants in the soil through an oxidation mode, and the activated treatment of iron-containing substances is needed to have good oxidation capacity, and the problem of limited organic pollutant treatment capacity exists.
In Chinese patent publication No. CN107641513A, a soil remediation agent is disclosed, which comprises the following components in parts by mass: 5-7 parts of bornyl acetate; 12-14 parts of diazolone; 7-9 parts of 1, 4-dimethylpiperazine; 10-15 parts of asiaticoside; 4-6 parts of 2-pyridinemethanol; 6-8 parts of ammonium citrate; 10-16 parts of fatty alcohol-polyoxyethylene ether; 10-15 parts of polyoxypropylene diol; 0.5-2 parts of 4-aminoisoquinoline; 1-2.5 of polycarboxylate; 4-12 parts of sodium polyacrylate; 6-10 parts of sodium chlorite; 15-22 parts of tridecyl polyoxyethylene ether; 80-100 parts of deionized water. The soil remediation agent in the scheme can restore organic pollution and remove heavy metal ions in soil, but the soil remediation agent contains excessive organic matters and has the problem of soil pollution.
Based on the above, the inventor prepares a remediation method of organic pollutant-heavy metal composite contaminated soil through a large number of tests and researches, so as to solve the problems in the prior art.
Disclosure of Invention
In view of the analysis of the prior art, the invention provides a method for restoring organic pollutant-heavy metal combined polluted soil, which can effectively degrade organic pollutants in the polluted soil and passivate heavy metals in the soil, thereby achieving the purpose of restoring the soil and having short restoration period.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for restoring organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, pouring the soil thoroughly, then applying active coal gangue powder, and uniformly mixing the active coal gangue powder with the soil to realize effective remediation of the organic pollutant-heavy metal composite polluted soil.
Preferably, the method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the contaminated soil containing the modified chitosan, watering every day, turning over once a day, and controlling the soil temperature to be 15-25 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) watering every day, ploughing once every day, and controlling the soil temperature to 10-15 ℃.
Preferably, the addition amount of the modified chitosan is 1.5-4.5% of the dry weight of the polluted soil.
Preferably, the adding amount of the active gangue powder is 1% -4% of the dry weight of the polluted soil.
Preferably, the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) placing the chitosan solution under the condition of vacuum degree of 0.07-0.09MPa for defoaming for 0.5-1h
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at 40-50 ℃ for 1-2 hours, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is in an inert gas atmosphere, the distance between the chitosan film and an electrode is 5-10mm, the treatment power is 50-70W, the discharge frequency is 10kHz, and the treatment time is 8-12 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating for 5-8h in an air oscillation bath at 35-40 ℃, with the oscillation speed of 90-110rpm, performing ultrasonic treatment on the reactor at the temperature of 5-10 ℃ for 30-40min, stopping ultrasonic treatment when the solution in the reactor is clear, adjusting the pH of the solution to 4.0-5.0 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1-2h to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
Preferably, the active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with a 100-mesh sieve, putting into an activation furnace, adding a K2CO3 solution with the concentration of 5mol/L, heating to 350-450 ℃, stirring for reaction for 5 hours, layering by a layering kettle to obtain activated material crystals, and filtering and washing to obtain the activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Preferably, the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Preferably, the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Compared with the prior art, the invention has the following beneficial effects:
before soil remediation, soil is firstly loosened, so that the modified chitosan, the active coal gangue powder and the soil are mixed more uniformly, the added chitosan can form a three-dimensional network structure after modification treatment, the chitosan has stronger adsorption capacity, organic pollutants and heavy metals in the soil can be adsorbed, and organic heavy metals are adsorbed in the three-dimensional network structure, so that the soil remediation effect is realized, meanwhile, the chemical activity of the modified chitosan is enhanced, the organic pollutants can be degraded, in addition, the modified chitosan is internally loosened and applied to the soil, the soil loosening state can be improved, the water and air permeability of the soil is enhanced, the soil remediation effect is improved, and the modified chitosan is environment-friendly and pollution-free;
the added active coal gangue powder is subjected to carbonization and activation treatment steps, so that the coal gangue powder has better ion exchange capacity and organophilic capacity, can effectively adsorb heavy metal ions in the soil, and can adsorb residual organic pollution in the soil again due to the organophilic capacity, thereby reducing the content of organic pollutants and heavy metals in the soil and further achieving the aim of restoring the soil;
according to the invention, the modified chitosan and the active gangue powder are mutually matched, the primary repairing effect is realized by the modified chitosan, and the special three-dimensional network structure of the modified chitosan can create a better adsorption environment for the active gangue powder, so that the adsorption capacity of the active gangue powder is improved, and a better soil repairing effect is achieved;
in addition, the modified chitosan and the active gangue powder have better activity by controlling the water content of the soil and the temperature of the soil, so that the effect of soil remediation is improved.
Detailed Description
The foregoing aspects of the present invention are described in further detail below by way of examples, but it should not be construed that the scope of the subject matter of the present invention is limited to the following examples, and that all the technologies that can be realized based on the above aspects of the present invention are within the scope of the present invention.
Example 1
The method for restoring the organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan accounting for 1.5% of the dry weight of the soil into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, thoroughly watering the soil, then applying active coal gangue powder accounting for 1% of the dry weight of the soil, uniformly mixing the active coal gangue powder with the soil, and realizing effective remediation of the organic pollutant-heavy metal composite polluted soil.
The method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the polluted soil containing the modified chitosan, watering every day, turning over once every day, and controlling the soil temperature to be 15 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) during the period, watering is carried out every day, ploughing is carried out once a day, and the soil temperature is controlled to be 10 ℃.
Wherein the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) placing the chitosan solution under the condition of 0.07MPa of vacuum degree for defoaming for 0.5h
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at 40 ℃ for 1 hour, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is in an inert gas atmosphere, the distance between the chitosan film and an electrode is 5mm, the treatment power is 50W, the discharge frequency is 10kHz, and the treatment time is 8 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating for 5 hours in an air oscillating bath at 35 ℃, with the oscillation speed of 90rpm, performing ultrasound for 30-40 minutes at the temperature of 5-10 ℃, stopping ultrasound when the solution in the reactor is clear, adjusting the pH of the solution to 4.0 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1 hour to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
The active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with 100 mesh sieve, putting into an activation furnace, adding K with the concentration of 5mol/L2CO3Heating the solutionStirring and reacting for 5 hours at 350 ℃, then layering through a layering kettle to obtain an activated material crystal, and filtering and washing to obtain an activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Example 2
The method for restoring the organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan accounting for 4.5% of the dry weight of the soil into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water to thoroughly irrigate the soil, then applying active coal gangue powder accounting for 4% of the dry weight of the soil, uniformly mixing the active coal gangue powder with the soil, and realizing effective remediation of the organic pollutant-heavy metal composite polluted soil.
The method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the polluted soil containing the modified chitosan, watering every day, turning over once every day, and controlling the soil temperature to be 25 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) during the period, watering is carried out every day, ploughing is carried out once a day, and the soil temperature is controlled to be 15 ℃.
Wherein the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) placing the chitosan solution under the condition of 0.09MPa of vacuum degree for defoaming for 1h
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at 50 ℃ for 2 hours, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is carried out in an inert gas atmosphere, the distance between the chitosan film and an electrode is 10mm, the treatment power is 70W, the discharge frequency is 10kHz, and the treatment time is 12 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating in an air oscillation bath at 40 ℃ for 8 hours at an oscillation speed of 110rpm, ultrasonically treating the reactor at 10 ℃ for 40 minutes, stopping ultrasonic treatment when the solution in the reactor is clear, adjusting the pH of the solution to 5.0 by using a sodium hydroxide solution, and adding ethanol for refluxing for 2 hours to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
The active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with a 100-mesh sieve, putting into an activation furnace, adding a K2CO3 solution with the concentration of 5mol/L, heating to 450 ℃, stirring for reaction for 5 hours, layering by a layering kettle to obtain an activated material crystal, and filtering and washing to obtain the activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Example 3
The method for restoring the organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan accounting for 3.0% of the dry weight of the soil into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water to thoroughly irrigate the soil, then applying active coal gangue powder accounting for 2.5% of the dry weight of the soil, uniformly mixing the active coal gangue powder with the soil, and realizing effective remediation of the organic pollutant-heavy metal composite polluted soil.
The method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the polluted soil containing the modified chitosan, watering every day, turning over once every day, and controlling the soil temperature to be 20 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) during the period, watering is carried out every day, ploughing is carried out once a day, and the soil temperature is controlled to be 13 ℃.
Wherein the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) the chitosan solution is defoamed for 0.7h under the condition that the vacuum degree is 0.08MPa
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at 45 ℃ for 1.5 hours, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is carried out in an inert gas atmosphere, the distance between the chitosan film and an electrode is 7mm, the treatment power is 60W, the discharge frequency is 10kHz, and the treatment time is 10 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating in an air oscillation bath at 38 ℃ for 6.5h at the oscillation speed of 100rpm, ultrasonically treating the reactor at 7.5 ℃ for 35min, stopping ultrasonic treatment when the solution in the reactor is clear, adjusting the pH of the solution to 4.5 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1.5h to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
The active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with a 100-mesh sieve, putting into an activation furnace, adding a K2CO3 solution with the concentration of 5mol/L, heating to 400 ℃, stirring for reaction for 5 hours, layering by a layering kettle to obtain an activated material crystal, and filtering and washing to obtain the activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Example 4
The method for restoring the organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan accounting for 2.0 percent of the dry weight of the soil into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, thoroughly watering the soil, then applying active coal gangue powder accounting for 2 percent of the dry weight of the soil, uniformly mixing the active coal gangue powder with the soil, and realizing the effective restoration of the organic pollutant-heavy metal composite polluted soil.
The method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the polluted soil containing the modified chitosan, watering every day, turning over once a day, and controlling the soil temperature to be 18 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) during the period, watering is carried out every day, ploughing is carried out once a day, and the soil temperature is controlled to be 12 ℃.
Wherein the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) placing the chitosan solution under the condition of 0.07MPa of vacuum degree for defoaming for 0.6h
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at the temperature of 43 ℃ for 1.3h, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is in an inert gas atmosphere, the distance between the chitosan film and an electrode is 6mm, the treatment power is 55W, the discharge frequency is 10kHz, and the treatment time is 9 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating in an air oscillation bath at 36 ℃ for 6 hours at an oscillation speed of 95rpm, ultrasonically treating the reactor at the temperature of 6 ℃ for 33 minutes, stopping ultrasonic treatment when the solution in the reactor is clear, adjusting the pH of the solution to 4.3 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1.3 hours to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
The active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with a 100-mesh sieve, putting into an activation furnace, adding a K2CO3 solution with the concentration of 5mol/L, heating to 380 ℃, stirring for reaction for 5 hours, layering by a layering kettle to obtain an activated material crystal, and filtering and washing to obtain the activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Example 5
The method for restoring the organic pollutant-heavy metal combined polluted soil comprises the following steps: adding modified chitosan accounting for 4.0% of the dry weight of the soil into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, thoroughly watering the soil, then applying active coal gangue powder accounting for 3% of the dry weight of the soil, uniformly mixing the active coal gangue powder with the soil, and realizing effective remediation of the organic pollutant-heavy metal composite polluted soil.
The method specifically comprises the following steps:
(1) loosening the organic pollutant-heavy metal composite polluted soil, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil;
(2) adding water, thoroughly watering the polluted soil containing the modified chitosan, watering every day, turning over once every day, and controlling the soil temperature to be 22 ℃;
(3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged;
(4) during the period, watering is carried out every day, ploughing is carried out once a day, and the soil temperature is controlled to be 14 ℃.
Wherein the modified chitosan is obtained by the following method:
(1) dissolving chitosan in glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution;
(2) the chitosan solution is defoamed for 0.9h under the condition that the vacuum degree is 0.09MPa
(3) Coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate at 40-50 ℃ for 1-2 hours, and obtaining a chitosan membrane after the membrane is naturally uncovered;
(4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is in an inert gas atmosphere, the distance between the chitosan film and an electrode is 9mm, the treatment power is 65W, the discharge frequency is 10kHz, and the treatment time is 11 min;
(5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating in an air oscillation bath at 38 ℃ for 7 hours at an oscillation speed of 105rpm, performing ultrasound on the reactor at the temperature of 9 ℃ for 38 minutes, stopping ultrasound when the solution in the reactor is clear, adjusting the pH of the solution to 4.8 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1.8 hours to obtain a reaction solution;
(6) and (5) filtering the reaction solution in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain the modified chitosan.
The active coal gangue powder is obtained by the following method:
(1) putting the coal gangue into an ultrafine pulverizer to be pulverized to below 150 meshes, adding a binder with the mass of 0.5 time of that of the coal gangue, fully mixing, adding deionized water with the mass of 2.5 times of that of the coal gangue, mixing, kneading, and briquetting by a briquetting machine to obtain a briquetting material;
(2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material;
(3) crushing the carbonized material, sieving with a 100-mesh sieve, putting into an activation furnace, adding a K2CO3 solution with the concentration of 5mol/L, heating to 420 ℃, stirring for reaction for 5 hours, layering by a layering kettle to obtain an activated material crystal, and filtering and washing to obtain the activated material;
(4) and (2) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
Wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
Wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
Comparative example 1
The method of Chinese patent publication No. CN108672485A is adopted to repair the soil.
Comparative example 2
The procedure and method were the same as in example 1 except that the modified chitosan was changed to the conventional chitosan.
Comparative example 3
The steps and methods were the same as in example 1 except that the active gangue powder was changed to ordinary gangue powder.
Test examples
Test soil was used for the preparation.
Adding an aqueous solution of a water-soluble compound of Cd metal and an aqueous solution of benzo (a) pyrene into common vegetable garden soil, wherein the content of heavy metal elements Hg, As, Pb and Cd in the soil is about 5 times of a standard limit value corresponding to the environmental requirement for agricultural product quality safety pollution-free vegetable production place (GB/T18407.1-2001). After fully and uniformly mixing the aqueous solution of the heavy metal compound and the aqueous solution of the benzo (a) pyrene with the garden soil, standing for one week, and detecting the content of Cd and the content of the benzo (a) pyrene, wherein the specific detection results are shown in Table 1.
TABLE 1 concentration of Cd and benzo (a) pyrene in soil available State before treatment
| Contaminants | Concentration (mg/kg) |
| Active state Cd | 18 |
| Benzo (a) pyrene | 3.2 |
Contaminated garden soil was restored by the restoration methods of examples 1 to 5 and comparative examples 1 to 3, and the content of Cd in an active state and the content of benzo (a) pyrene in the restored soil were measured, and the specific results are shown in Table 2.
TABLE 2
As can be seen from the data in table 2, the remediation effect of Cd and benzo (a) pyrene after the contaminated soil is remediated by the method of the present invention is good, the residual rate of Cd in the soil is low, and the degradation effect of benzo (a) pyrene is obvious, which indicates that the remediation of the composite contaminated soil by the combination of the modified chitosan and the active gangue powder achieves a good remediation effect, and the remediation effect of the contaminated soil of example 3 is the last. Compared with the prior art, the method improves the remediation effect of the heavy metal and polycyclic aromatic hydrocarbon composite polluted soil, is more beneficial to the actual remediation of the polluted soil, and can improve the remediation effect of the soil by adding the modified chitosan and the active coal gangue powder according to the comparative examples 2 and 3.
In conclusion, the invention provides a method for restoring organic pollutant-heavy metal combined polluted soil, which can effectively degrade organic pollutants in the polluted soil and passivate heavy metals in the soil, thereby achieving the aim of restoring the soil and having short restoration period.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. The method for restoring the organic pollutant-heavy metal combined polluted soil is characterized by comprising the following steps of: adding modified chitosan into the organic pollutant-heavy metal composite polluted soil, ploughing the polluted soil to uniformly mix the modified chitosan with the soil, adding water, pouring the soil thoroughly, then applying active coal gangue powder, and uniformly mixing the active coal gangue powder with the soil to realize effective remediation of the organic pollutant-heavy metal composite polluted soil;
the modified chitosan is obtained by the following method: dissolving chitosan in a glacial acetic acid aqueous solution, carrying out ultrasonic stirring, and then stirring at a high speed until the chitosan is completely dissolved to obtain a chitosan solution; (2) placing the chitosan solution in a vacuum degree of 0.07-0.09MPa for defoaming for 0.5-1h (3) coating the defoamed chitosan solution on a smooth glass plate, placing the glass plate in a vacuum box, evaporating the glass plate for 1-2h at 40-50 ℃, and obtaining a chitosan membrane after the membrane is naturally uncovered; (4) treating the chitosan film prepared in the step (3) by adopting a plasma technology, wherein the treatment is in an inert gas atmosphere, the distance between the chitosan film and an electrode is 5-10mm, the treatment power is 50-70W, the discharge frequency is 10kHz, and the treatment time is 8-12 min; (5) adding the chitosan membrane subjected to the plasma treatment in the step (4) into a reactor, adding chloroform, vacuumizing the reactor, introducing nitrogen, oscillating in an air oscillation bath at 35-40 ℃ for 5-8h at the oscillation speed of 90-110rpm, performing ultrasound on the reactor at the temperature of 5-10 ℃ for 30-40min, stopping ultrasound when the solution in the reactor is clear, adjusting the pH of the solution to 4.0-5.0 by using a sodium hydroxide solution, and adding ethanol for refluxing for 1-2h to obtain a reaction solution; (6) filtering the reaction liquid obtained in the step (5), washing a filter cake by using ethanol, water and acetone, collecting the filtrate, removing the solvent, and drying to obtain modified chitosan;
the active coal gangue powder is obtained by the following method: (1) pulverizing coal gangue in a superfine pulverizer to below 150 meshes, adding binder 0.5 times of the mass of the coal gangue, mixing, and adding deionized water 2.5 times of the mass of the coal gangueMixing and kneading the water and the water, and then briquetting and forming by a briquetting machine to obtain a briquetting material; (2) putting the briquette material into a carbonization furnace, heating and carbonizing under the protection of inert gas, firstly curing at 300 ℃ for 1.5h, directly heating to 550 ℃ for carbonization for 2h, and finally heating to 800 ℃ for carbonization for 1h to obtain a carbonized material; (3) crushing the carbonized material, sieving with 100 mesh sieve, putting into an activation furnace, adding K with the concentration of 5mol/L2CO3Heating the solution to 350-450 ℃, stirring and reacting for 5h, layering the solution by a layering kettle to obtain activated material crystals, and filtering and washing the activated material crystals to obtain the activated material; and (4) putting the activated material into a KOH solution with the concentration of 3mol/L, activating for 2 hours at the temperature of 60 ℃, then heating to 80 ℃ for activating for 5 hours, finally heating to 90 ℃ for activating for 10 hours, then washing, drying, crushing, and sieving with a 200-mesh sieve to obtain the modified coal gangue powder.
2. The method for remediating organic pollutant-heavy metal combined contaminated soil according to claim 1, which specifically comprises the following steps: (1) loosening the soil polluted by the organic pollutant and heavy metal, applying modified chitosan, and ploughing the soil to uniformly mix the modified chitosan and the soil; (2) adding water, thoroughly watering the contaminated soil containing the modified chitosan, watering every day, turning over once a day, and controlling the temperature of the soil to be 15-25 ℃; (3) then applying active coal gangue powder into the soil, ploughing the soil to uniformly mix the active coal gangue powder with the soil, and adding water until the soil is submerged; watering every day during the period (4), ploughing once every day, and controlling the soil temperature to be 10-15 ℃.
3. The method for remediating organic pollutant-heavy metal combined contaminated soil according to claim 1 or 2, wherein the modified chitosan is added in an amount of 1.5% -4.5% by dry weight of the contaminated soil.
4. The method for remediating organic pollutant-heavy metal combined contaminated soil according to claim 1 or 2, wherein the addition amount of the active gangue powder is 1% -4% of the dry weight of the contaminated soil.
5. The method for remediating an organic pollutant-heavy metal combined contaminated soil according to claim 1 or 2, wherein the organic pollutant is polycyclic aromatic hydrocarbon; the heavy metal is one or at least two of Cu, Pb and Cd.
6. The method for remediating an organic pollutant-heavy metal combined contaminated soil according to claim 5, wherein the polycyclic aromatic hydrocarbon is benzo (a) pyrene.
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