CN114192561A - Remediation method for cadmium-containing contaminated soil and application thereof - Google Patents
Remediation method for cadmium-containing contaminated soil and application thereof Download PDFInfo
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Abstract
The invention belongs to the technical field of soil remediation treatment, and discloses a remediation method for cadmium-containing contaminated soil and application thereof. The repairing method comprises the following steps: mixing an activation pretreatment solution with cadmium-containing polluted soil to be treated, and then repairing the cadmium-containing polluted soil by an electrochemical method, wherein the activation pretreatment solution is a carboxylic acid chelating agent solution. The method adopts the activation pretreatment solution to pretreat the cadmium-containing polluted soil so as to promote the heavy metal pollutants to be converted into ion forms to form heavy metal ions, then promote the heavy metal ions to directionally move from the anode to the cathode, and carry out electric restoration treatment on the heavy metal-polluted soil by using an electrochemical method, thereby improving the restoration effect on the cadmium-polluted soil. So that the removal rate of cadmium in the final heavy metal polluted soil is high and exceeds 95 percent.
Description
Technical Field
The invention belongs to the technical field of soil remediation treatment, and particularly relates to a remediation method for cadmium-containing contaminated soil and application thereof.
Background
The problem of heavy metal pollution of soil is prominent in the world, particularly in regions with dense population and developed economy. Heavy metal pollutants are mainly accumulated and generated in the industrial production and urbanization development processes. The inorganic pollutants in the soil pollutants account for 82.8 percent, and particularly the eight heavy metal pollutants in the soil pollutants respectively account for the following proportions: cadmium (7.0%), mercury (1.6%), arsenic (2.7%), copper (2.1%), lead (1.5%), chromium (1.1%), zinc (0.9%) and nickel (4.8%), wherein lead and cadmium are two common heavy metal pollutants in soil pollution, are easily absorbed by plants, enter a food chain and are transmitted to be absorbed by a human body, and are extremely harmful to the health of the human body. Heavy metal pollutants in the soil environment have the characteristics of wide source, difficult degradation, long residue, high toxicity and the like, and are a great problem and a research hotspot in the current soil environment pollution treatment. The existing form of the heavy metal in the soil can be extracted step by a chemical continuous extraction method, and the existing form of the heavy metal in the soil can be divided into an exchangeable state, a reducible state, an oxidizable state and a residue state. The migration capacity and bioavailability of these four forms in soil are reduced in turn. The development of common restoration technology for heavy metal contaminated soil is closely related to the migration and transformation characteristics of heavy metals.
For heavy metal contaminated soil, the electrokinetic remediation technology has obvious advantages compared with other soil remediation methods such as a soil-mining method, a soil leaching, curing/stabilizing technology, phytoremediation, microbial remediation and the like. The electric restoration process of the heavy metal contaminated soil mainly acts through electrochemical reaction between electrodes, various complex chemical agents do not need to be additionally added, the soil is environment-friendly and pollution-free, the period required by electric restoration is short, the daily maintenance is simple, and the restoration efficiency is high. However, in the process of electric repair, the migration speeds of anions and cations generated by hydrolysis of two poles are greatly different, so that the phenomena of focusing effect, concentration polarization, activation polarization, resistance polarization and the like are caused, the directional migration of heavy metal ions is hindered, and the repair efficiency is required to be improved.
Therefore, the method needs to further enhance and promote the treatment efficiency of heavy metal pollutants in the soil by electrokinetic remediation, and has important significance for the remediation of the heavy metal polluted soil.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art described above. Therefore, the invention provides a remediation method of cadmium-containing contaminated soil and application thereof, and the remediation method has a high removal rate of cadmium in the soil, which is more than 95%.
The invention conception of the invention is as follows: the method adopts an activation pretreatment solution, namely a carboxylic acid chelating agent solution, to pretreat the heavy metal contaminated soil (namely the cadmium-containing contaminated soil) so as to promote the heavy metal contaminants to be converted into ion forms to form heavy metal ions, then promote the heavy metal ions to directionally move from an anode to a cathode, and carry out electric restoration treatment on the heavy metal contaminated soil by using an electrochemical method, so that the removal rate of cadmium in the heavy metal contaminated soil is high and exceeds 95 percent finally.
The invention provides a method for repairing cadmium-containing polluted soil.
Specifically, the method for repairing the cadmium-containing polluted soil comprises the following steps:
mixing an activation pretreatment solution with cadmium-containing polluted soil to be treated, and then repairing the cadmium-containing polluted soil by an electrochemical method, wherein the activation pretreatment solution is a carboxylic acid chelating agent solution.
Preferably, the carboxylic acid chelating agent solution comprises at least one of glycolic acid solution, citric acid solution, acetic acid solution, lactic acid solution, or tartaric acid solution; glycolic acid solution is more preferred.
Preferably, the concentration of the carboxylic acid chelating agent solution is 0.8-1.5 mol/L; more preferably, the concentration of the carboxylic acid chelating agent solution is 0.9-1.2 mol/L; more preferably, the concentration of the carboxylic acid chelating agent solution is 1.0 mol/L.
Preferably, the method for repairing the cadmium-containing polluted soil comprises the following steps:
the method comprises the steps of taking cadmium-containing polluted soil to be treated, activating pretreatment solution, electrolyte and an electrolytic cell, wherein the electrolytic cell sequentially comprises an anode chamber, a soil chamber and a cathode chamber, placing the cadmium-containing polluted soil to be treated in the soil chamber of the electrolytic cell, adding the activating pretreatment solution into the soil chamber, standing, removing the activating pretreatment solution flowing into the anode chamber and the cathode chamber, adding the electrolyte into the anode chamber and the cathode chamber, inserting electrodes into the electrolyte in the anode chamber and the cathode chamber, electrifying, and powering off after a period of time, thus completing the repairing method.
Preferably, the anode chamber, the cathode chamber and the soil chamber are separated by a partition plate with holes and at least one layer of filter paper. The effect is to make the electrolyte smoothly flow between the anode chamber and the cathode chamber and the soil chamber and avoid the cadmium-containing polluted soil from losing to the anode chamber and the cathode chamber to block the electrode reaction.
Preferably, the amount of the activation pretreatment solution added into the soil chamber is such that the cadmium-contaminated soil is wetted and fully contacts with the cadmium-contaminated soil to ensure the pretreatment effect and further reach a saturated wetting state.
Preferably, the soil chamber is covered with a membrane after the activating pretreatment solution is added to the soil chamber.
Preferably, the standing time is 9-13 hours; further preferably, the standing time is 10 to 12 hours.
Preferably, the electrolyte comprises an anolyte and a catholyteThe anolyte is water, and is further preferably ultrapure water; the catholyte comprises an inorganic acid solution, further preferably the catholyte comprises HNO3The concentration of the solution, more preferably, the inorganic acid solution is 0.08 to 0.2mol/L (preferably 0.1 mol/L). An anolyte solution is added to the anode chamber and a catholyte solution is added to the cathode chamber.
Preferably, the electrode is a graphite electrode. I.e. the electrodes inserted into the electrolyte in the anode and cathode compartments are both graphite electrodes.
Preferably, the energization is direct current energization.
Preferably, the electrified voltage density is 1 +/-0.3V/cm; more preferably, the voltage intensity of the electricity is 1 +/-0.1V/cm (the total voltage of 20V input in the soil remediation area is represented, namely the section from the anode to the cathode is 20cm long, and the voltage of every 1cm in the section is 1 +/-0.1V/cm).
Preferably, the time of the energization is 90 to 96 hours.
The second aspect of the invention provides an application of a remediation method of cadmium-containing contaminated soil.
The method for repairing the cadmium-containing polluted soil is applied to the field of pollutant removal.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts an activated pretreatment solution, namely a carboxylic acid chelating agent solution, to pretreat heavy metal contaminated soil (namely cadmium-contaminated soil) so as to promote the heavy metal pollutants to be converted into heavy metal ions in an ion form, then promote the heavy metal ions to directionally move from an anode to a cathode, and carry out electric restoration treatment on the heavy metal contaminated soil by using an electrochemical method. So that the removal rate of cadmium in the final heavy metal polluted soil is high and exceeds 95 percent. Under the same condition, the cadmium removal rate of the repair method can reach 95.15%, and compared with the electric repair effect under the condition of ultra-pure water wetting treatment, the electric repair method has the advantage that the electric repair effect is obviously improved.
Drawings
FIG. 1 is a graph showing the change of current in the remediation process of cadmium-contaminated soil according to example 1, comparative example 1 and comparative example 2;
FIG. 2 is a graph showing the results of pH values of different soil regions after remediation of cadmium-contaminated soils according to example 1, comparative example 1 and comparative example 2;
FIG. 3 is a graph showing the results of oxidation-reduction potentials of different soil areas after remediation of cadmium-contaminated soils of example 1, comparative example 1 and comparative example 2;
FIG. 4 is a graph of conductivity results for different soil areas after remediation of cadmium-contaminated soil of example 1, comparative example 1, and comparative example 2;
FIG. 5 is a graph of total cadmium concentration in different soil areas after remediation of cadmium contaminated soil of example 1, comparative example 1, and comparative example 2.
Detailed Description
In order to make the technical solutions of the present invention more apparent to those skilled in the art, the following examples are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.
The starting materials, reagents or apparatuses used in the following examples are conventionally commercially available or can be obtained by conventionally known methods, unless otherwise specified.
The preparation process of the cadmium-contaminated soil to be treated used in the following examples and comparative examples was: collecting soil near hydrographic village in Qujiang area of Shaoguan city, Guangdong province, removing foreign matters such as stones and plant residues after air drying (natural air drying) the collected soil sample, grinding the soil sample by using a wood stick until the soil sample passes through a nylon sieve with the diameter of 2mm, concentrating the soil sample by using a quartering method after uniformly mixing the soil sample, grinding the soil sample by using an agate mortar until the soil sample completely passes through a nylon sieve with the diameter of 100 meshes (the aperture is 0.15mm) for digestion (the soil sample is digested by adopting a hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid full decomposition method), and then determining the concentration of cadmium pollutants in the soil sample. Through determination, the concentration of cadmium in a soil sample (or called cadmium-containing polluted soil) is 8.3mg/kg, the water content of the soil is 3.7%, the pH value is 5.3, and the conductivity (EC) of the soil sample is 494 mu s/cm.
Example 1: method for restoring cadmium-containing polluted soil
A method for restoring cadmium-containing polluted soil comprises the following steps:
500g of cadmium-contaminated soil to be treated (cadmium concentration 8.3mg/kg), an activation pretreatment solution (glycolic acid solution, concentration 1.0mol/L), an electrolyte (ultrapure water, 0.1mol/L HNO) were taken3Solution), an electrolytic cell (an electrolytic cell made of organic glass, the length, width and height are 20cm multiplied by 10cm), the electrolytic cell sequentially comprises an anode chamber, a soil chamber and a cathode chamber from left to right (a partition board with holes and at least three layers of filter paper are arranged between the anode chamber and the cathode chamber and are separated from the soil chamber), the cadmium-containing polluted soil to be processed is flatly laid in the soil chamber of the electrolytic cell, then the activation pretreatment solution is added along the four walls of the soil chamber until the liquid level in the anode chamber and the cathode chamber is equal to the surface of the cadmium-containing polluted soil in the soil chamber, namely the cadmium-containing polluted soil reaches a saturated state, a layer of preservative film (which is used for reducing the volatilization of the glycolic acid solution) is covered, the solution is kept stand for 10 hours, then the activation pretreatment solution flowing into the anode chamber and the cathode chamber is removed, then the ultra-pure water is added into the anode chamber, and 0.1mol/L HNO is added into the cathode chamber3Inserting graphite electrodes into the anode chamber and the cathode chamber, electrifying at DC voltage of 20 + -0.1V, supplementing ultrapure water if ultrapure water in the anode chamber is reduced during electrifying, and adding HNO in the cathode chamber3If there is a decrease, HNO is added3And (5) electrifying the solution, and then powering off after 96 hours to finish the repairing method.
Comparative example 1
Comparative example 1 differs from example 1 only in that ultrapure water is used in place of the glycolic acid solution in example 1 in comparative example 1.
Comparative example 2
Comparative example 2 differs from example 1 only in that the glycolic acid solution in example 1 is replaced with a 1mol/L sodium tripolyphosphate solution in comparative example 2.
Comparative example 3
Comparative example 3 differs from example 1 only in that the glycolic acid solution in example 1 is replaced with a mixed solution (the mixed solution is composed of 0.095mol/L sodium tripolyphosphate solution and 1mol/L glycolic acid solution) in comparative example 3.
Product effectiveness testing
1. Current change during remediation of cadmium-contaminated soil
The current can reflect the number of electromigration ions generated in the cadmium-containing polluted soil in the repairing method. In the process of repairing cadmium-contaminated soil after three different pretreatment modes (different types of activating pretreatment solutions) of example 1 and comparative examples 1-2, a current recorder (model L99-DL-4) is used for automatically collecting and recording current data (1 time of data recording every 1 hour), and the result is shown in FIG. 1.
FIG. 1 is a graph showing the change of current in the remediation process of cadmium-contaminated soil according to example 1, comparative example 1 and comparative example 2; as can be seen from fig. 1, the current in the three sets of remediation tests (example 1, comparative example 1, and comparative example 2, respectively) rapidly increased after energization, and compared to comparative example 1 (the activation pretreatment solution was ultrapure water), the current in example 1 (the activation pretreatment solution was glycolic acid) and comparative example 2 (the activation pretreatment solution was sodium tripolyphosphate) both rapidly increased within 1 hour after energization, because the heavy metal form in the soil after saturation treatment with glycolic acid and sodium tripolyphosphate solution can be converted into a form that is more easily migrated, in which the migration ability of ionic heavy metal is strongest, and therefore heavy metal ions activated by pretreatment in the soil after energization and a large amount of H generated by hydrolysis at the anode side are present in the soil after energization+And the directional migration is generated to the cathode under the action of the electric field. The current decrease after a period of time indicates a decrease in the number of free ions, since the heavy metal cations that are mobile in the soil close to the anode side have mostly migrated towards the cathode, i.e. the content of ions that can migrate is reduced, and the cathode side is constantly hydrolysed to produce OH-Both with H generated at the anode+The water produced by the reaction is combined with heavy metal cations transferred from the soil near the anode to form precipitates in the soil near the cathode, and the number of ions in the soil area is continuously reduced. Therefore, the glycolic acid solution and the sodium tripolyphosphate solution as the activation pretreatment solution can effectively promote the directional migration of the heavy metal pollutants in the polluted soil in the remediation processAnd the migration rate is improved, and particularly, the migration rate can be obviously improved by using the glycolic acid solution as the activation pretreatment solution.
2. The pH value and the oxidation-reduction potential of each area change after the cadmium-containing polluted soil is repaired
The soil chamber in which the soil contaminated with cadmium was located after the completion of the remediation in the soil chamber of example 1 was sequentially divided into five soil regions from the anode-side end toward the cathode chamber, and the soil regions were designated as S1, S2, S3, S4, and S5 (each region was equal in width). And uniformly digging enough repaired soil samples in five soil areas by using plastic medicine spoons, placing the soil samples in a white porcelain plate, naturally drying the soil samples in the white porcelain plate, and grinding the soil samples by using a porcelain mortar until the soil samples pass through a nylon sieve (with the aperture of 0.15mm) of 100 meshes to obtain samples to be detected. Weighing a proper amount of the repaired soil sample, placing the soil sample into a 50mL beaker, adding water according to the water-soil mass ratio of 2.5:1, sealing the beaker by using a preservative film, then stirring the beaker for 2 minutes by using a magnetic stirrer, standing the beaker for 30 minutes, and completing the measurement within 1 hour by using a pH meter (the pH meter is Raymond PhSJ-4F). The pH value of the soil before remediation is 5.3.
The results of measuring the soil pH and oxidation-reduction potential (ORP) in the region from S1 to S5 after remediation are shown in FIGS. 2 and 3.
FIG. 2 is a graph showing the results of pH values of different soil regions after remediation of cadmium-contaminated soils according to example 1, comparative example 1 and comparative example 2;
FIG. 3 is a graph showing the results of oxidation-reduction potentials of different soil areas after remediation of cadmium-contaminated soils of example 1, comparative example 1, and comparative example 2.
H produced by electrolysis+The ion moving speed of (2) is OH-1.8 times of the total amount of the alkaline component, the migration speed of an acid peak formed in the soil near the anode to the cathode is significantly higher than that of an alkali peak formed near the cathode to the anode, so that the pH value generally gradually rises from the anode to the cathode in the soil remediation region, but is generally neutral or weakly alkaline at last. This is due to the hydrolysis reaction at the cathode to form OH-They migrate in the direction of the anode and hydrolyze the H produced at the anode+Will migrate towards the cathode and H+The ion moving speed of (2) is OH-1.8 times of the total amount of the organic compound, and therefore, can cause the generation of hydrogen at the cathodeOH in the soil near the migration cathode-H to be gradually moved from the anode direction+By neutralized, it is meant that the acid peak generated near the anode gradually migrates toward the vicinity of the cathode. As can be seen from fig. 2, the pH value in the soil region after remediation in comparative examples 1-2 gradually increased from the anode toward the cathode. The pH values of the soil areas S1-S5 repaired in the embodiment 1 are all kept at about 3, and the pH values are slightly increased near the cathode, so that cadmium pollutants in the soil can be better dissolved, the cadmium pollutants in the soil can be kept to migrate to the cathode in an ionic state, the cadmium pollutants are precipitated in the cathode chamber, and almost all cadmium ions are separated from the soil and enriched in the cathode chamber. In comparative example 2, since the sodium tripolyphosphate solution itself is alkaline, in addition to being acidic in the regions of the S1 and S2 soils near the anode side, the middle region S3 of the remediating soil is neutral, and then the regions of S4 and S5 near the cathode side are both strongly alkaline, resulting in that a large amount of activated and migrated heavy metal ions are precipitated and accumulated, and cannot migrate out of the soil, thereby reducing the overall remediation efficiency, but the overall remediation effect is better than that of ultrapure water (comparative example 1).
As can be seen from fig. 3, the oxidation-reduction potential of the soil region in comparative examples 1-2 gradually decreased significantly from S1 to S5, whereas the oxidation-reduction potential of example 1 was maintained at around 250mV, so that heavy metal ions could be stably precipitated.
In the embodiment 1, the glycolic acid solution is used as the activation pretreatment solution, so that each soil area can keep an acidic environment beneficial to the migration of heavy metal pollutants, and the removal efficiency of the heavy metal pollutants is obviously improved.
3. Conductivity measurement result after cadmium-contaminated soil remediation
And uniformly digging enough repaired soil samples in the five soil areas (S1, S2, S3, S4 and S5) by using a plastic medicine spoon, placing the soil samples into a white porcelain plate, naturally drying the soil samples in the air, and grinding the soil samples by using a porcelain mortar until the soil samples pass through a 100-mesh nylon sieve (with the aperture of 0.15mm) to obtain samples to be detected. Weighing a proper amount of sample to be measured, placing the sample to be measured in a 50mL plastic centrifuge tube, adding water according to the water-soil mass ratio of 5:1, oscillating for 30 minutes at the oscillation frequency of 180 r/min, standing for 30 minutes, centrifuging for 30 minutes at the speed of 3000 r/min, taking out, and placing the electrode of a conductivity meter (the model of the conductivity meter is thunder magnet DDS-11A) in the supernatant part of the centrifuge tube to complete the measurement. The conductivity test results are shown in fig. 4.
FIG. 4 is a graph of conductivity results for different soil areas after remediation of cadmium-contaminated soil of example 1, comparative example 1, and comparative example 2.
The conductivity of the soil before remediation is 494 mu s/cm, and the conductivity of the soil after remediation is obviously increased. In comparative example 1, more H was produced by electrolysis in the soil except for the vicinity of the electrode+And OH-The conductivity is lower in the other regions than the higher conductivity because the presence of water produced by the neutralization reaction in the central soil region reduces the number of ions present in the soil and the conductivity decreases. While the conductivities of example 1 and comparative example 2 were significantly improved and maintained at high conductivity levels, and in combination with the pH and redox potential results measured in fig. 2 and 3, it can be seen that example 1 provides a stable acidic environment for dissolution and migration of soil heavy metal contaminants, H+Large amount of Cd2+Since a large amount of the ions are eluted, the amount of the ions in the soil area after restoration is large, and the conductivity is always maintained at a high and stable level. In comparative example 2, the conductivity in soil region S5 suddenly rose to 1.872mS/cm, similar to the pH change results in FIG. 2, primarily due to cathodic electrolysis producing OH-Migration and diffusion to soil, and sodium tripolyphosphate mainly exists in the form of phosphate or hydrogen phosphate in weak alkali or strong alkali environment and undergoes multi-stage hydrolysis reaction to generate a large amount of OH-And release of Na+Increased alkalinity, release of substantial amounts of OH-And Na+So that the conductivity in the soil region rises sharply.
4. Determination of total concentration of cadmium and analysis of concentration change of cadmium-containing polluted soil after remediation
And uniformly digging enough repaired soil samples in the five soil areas (S1, S2, S3, S4 and S5) by using a plastic medicine spoon, placing the soil samples into a white porcelain plate, naturally airing the white porcelain plate, grinding the white porcelain plate by using a porcelain mortar until the white porcelain plate passes through a nylon sieve of 100 meshes (the aperture of 0.15mm) to obtain a sample to be detected, digesting the soil by adopting a hydrochloric acid-nitric acid-hydrofluoric acid-perchloric acid full decomposition method, measuring the residual total cadmium concentration in the repaired soil sample by using an atomic absorption spectrophotometry, and analyzing the concentration change of the soil sample before and after repairing. The method comprises the following specific steps:
accurately weighing 0.4g (accurate to 0.0002g) of soil sample, adding the soil sample into a microwave digestion tank, adding a little water to wet the soil sample, and then sequentially adding 6mL of nitric acid solution, 3mL of hydrochloric acid and 2mL of hydrofluoric acid solution (the acid is purchased acid stock solution) into an acid-proof fume hood according to the national standard (HJ 832 and 2017) to fully and uniformly mix the soil sample and the digestion solution (the nitric acid solution, the hydrochloric acid and the hydrofluoric acid solution form the digestion solution). If there is a violent chemical reaction, the cover is covered and screwed down after the reaction is finished. And (4) loading the microwave digestion tank into a digestion tank support, then placing the microwave digestion tank into a furnace chamber of a microwave digestion device, and confirming that the temperature sensor and the pressure sensor work normally. Microwave digestion was carried out according to the temperature program in table 1, and cooling was carried out after the program was finished. And (3) after the temperature in the microwave digestion tank is reduced to 20 ℃ at room temperature, taking out the microwave digestion tank from an acid-proof fume hood, slowly releasing pressure and releasing gas, and opening the microwave digestion tank cover.
Table 1: microwave digestion and temperature rise process
| Time of temperature rise | Digestion temperature | Retention time |
| 7 minutes | Room temperature → 120 deg.C | 3 |
| 5 minutes | 120→160℃ | 3 |
| 5 minutes | 160→190℃ | 25 minutes |
Transferring the mixture in the microwave digestion tank to a polytetrafluoroethylene crucible, washing the microwave digestion tank and the cover by water, and pouring the mixture into the crucible. And (3) placing the crucible on temperature control heating equipment to remove acid under the micro-boiling state. And when the liquid is viscous, taking the liquid down for cooling slightly, taking a small amount of dilute nitric acid by using a dropper to wash the inner wall of the crucible, dissolving residues attached to the inner wall of the crucible by using the residual heat, transferring the residues into a 25mL volumetric flask, sucking a small amount of dilute nitric acid by using the dropper to repeat the steps, transferring the washing liquid into the volumetric flask together, then fixing the volume to a scale mark by using the dilute nitric acid, mixing uniformly, standing for 60 minutes, and taking the supernatant to be measured.
The results of the atomic absorption spectrophotometry measurement of the supernatant are shown in fig. 5, and fig. 5 is a graph showing the total cadmium concentration in different soil areas after the cadmium-contaminated soil is repaired in example 1, comparative example 1 and comparative example 2. The total concentration of cadmium in the soil before remediation is 8.3mg/kg, and the concentration of cadmium in the soil after remediation in example 1 is remarkably reduced. The average removal rates of the comparative examples 1 and 2 for the total cadmium in the cadmium-contaminated soil (the average removal rates are the average values of the removal rates of the total cadmium in the soil areas S1, S2, S3, S4 and S5) are respectively 30.68% and 48.75%. And the average removal rate of the total cadmium in the cadmium-containing polluted soil in the example 1 is 95.15%. It can be seen that the remediation effect of example 1 using glycolic acid solution as the activation pretreatment solution is the best, the cadmium contaminant in the cadmium-contaminated soil can be almost completely removed, the cadmium removal efficiency of example 1 is improved by 210.14% (210.14% ═ 95.15% -30.68%)/30.68%. 100%) compared with the remediation effect of comparative example 1, and the cadmium removal efficiency of example 1 is improved by 95.18% (95.18%: 95.15% -48.75%)/48.75%. 100%) compared with the remediation effect of comparative example 2.
The soil sample repaired in comparative example 3 was tested according to the above method, and the result was that the average removal rate of total cadmium in the cadmium-contaminated soil of comparative example 3 was 53.30%.
It should be noted that, within the scope of the present invention, when the technical solution is adjusted, for example, citric acid solution, acetic acid solution, lactic acid solution or tartaric acid solution is used instead of glycolic acid solution, the average removal rate of the total cadmium in the soil is also over 85%, and the removal efficiency of the total cadmium in the soil is the highest by using glycolic acid solution.
Claims (10)
1. The method for repairing the cadmium-containing polluted soil is characterized by comprising the following steps of:
mixing an activation pretreatment solution with cadmium-containing polluted soil to be treated, and then repairing the cadmium-containing polluted soil by an electrochemical method, wherein the activation pretreatment solution is a carboxylic acid chelating agent solution.
2. The repair method of claim 1, wherein the carboxylic acid based chelating agent solution comprises at least one of a glycolic acid solution, a citric acid solution, an acetic acid solution, a lactic acid solution, or a tartaric acid solution.
3. The repair method according to claim 1, wherein the concentration of the carboxylic acid type chelating agent solution is 0.8 to 1.5 mol/L.
4. Repair method according to any one of claims 1-3, characterized in that it comprises the following steps:
the method comprises the steps of taking cadmium-containing polluted soil to be treated, an activation pretreatment solution, an electrolyte and an electrolytic cell, wherein the electrolytic cell sequentially comprises an anode chamber, a soil chamber and a cathode chamber, placing the cadmium-containing polluted soil to be treated in the soil chamber of the electrolytic cell, adding the activation pretreatment solution into the soil chamber, standing, removing the activation pretreatment solution flowing into the anode chamber and the cathode chamber, adding the electrolyte into the anode chamber and the cathode chamber, inserting electrodes into the electrolyte in the anode chamber and the cathode chamber, electrifying, and powering off after a period of time, thus completing the restoration method.
5. Process for the rehabilitation according to claim 4, characterized in that between the anodic and cathodic compartments and the soil compartment are placed perforated separators and at least one layer of filter paper.
6. The remediation method of claim 4 wherein the soil chamber is covered with a membrane after addition of said activating pretreatment solution thereto.
7. The repair method according to claim 4, wherein the time for the standing is 9 to 13 hours.
8. The repair method of claim 4, wherein the electrolyte comprises an anolyte and a catholyte, the anolyte being water; the catholyte comprises an inorganic acid solution.
9. The repair method according to claim 4, wherein the electrified voltage density is 1 ± 0.3V/cm; the electrifying time is 90-96 hours.
10. Use of the remediation method of any one of claims 1 to 9 in the field of contaminant removal.
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| CN115351060A (en) * | 2022-08-22 | 2022-11-18 | 广东环境保护工程职业学院 | Compound eluting agent, preparation method thereof and application thereof in removing cadmium and lead in soil |
| CN115491206A (en) * | 2022-08-16 | 2022-12-20 | 中化地质矿山总局浙江地质勘查院 | Agent and method for repairing heavy metal contaminated soil |
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| CN115351060A (en) * | 2022-08-22 | 2022-11-18 | 广东环境保护工程职业学院 | Compound eluting agent, preparation method thereof and application thereof in removing cadmium and lead in soil |
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