CN109647869B - Method for rapidly reducing heavy metal content in heavily polluted soil - Google Patents
Method for rapidly reducing heavy metal content in heavily polluted soil Download PDFInfo
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- CN109647869B CN109647869B CN201811382511.9A CN201811382511A CN109647869B CN 109647869 B CN109647869 B CN 109647869B CN 201811382511 A CN201811382511 A CN 201811382511A CN 109647869 B CN109647869 B CN 109647869B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- 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
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Abstract
The invention discloses a method for rapidly reducing the heavy metal content of heavily polluted soil, which comprises the following steps: (1) adding lime with the soil mass percent of 0.2% into the heavy metal contaminated soil to carry out passivation reaction; (2) separating the passivated soil into colloidal particles in the soil by using an ultrasonic separation method, and adding a flocculating agent into the soil colloidal solution to flocculate and precipitate the soil colloidal particles in the solution; (3) adding an alkaline solution into the flocculated solution to remove heavy metal elements in the solution so as to enable the heavy metal elements to reach the standard of surface water; (4) and adding a curing agent with the mass of 30% of that of the sediment into the flocculation sediment to ensure that the leaching toxicity is lower than the identification standard of hazardous wastes. According to the invention, lime is added into the heavy metal contaminated soil for passivation, so that the content of colloid in the soil can be increased, the adsorption amount of the soil colloid to the heavy metal is increased, and the soil colloid is separated, thereby effectively reducing the content of the heavy metal in the soil.
Description
Technical Field
The invention relates to the technical field of soil improvement, in particular to a method for quickly reducing the heavy metal content of heavily polluted soil.
Background
According to the survey bulletin of the national soil pollution conditions in 2014, the standard exceeding rate of the point positions of typical plots and surrounding soil in China is more than 20%. The number of polluted sites left after the removal of urban industrial enterprises in China exceeds 50 thousands, wherein the heavy metal polluted sites account for a considerable proportion, measures are urgently needed to be taken to repair the soil of the heavy metal polluted sites, and the selected site repair technology has the characteristics of small secondary pollution risk, short repair period, high stability and the like. At present, the soil remediation technologies adopted by domestic heavy metal contaminated site soil remediation engineering mostly comprise technologies of blocking landfill, solidification/stabilization, chemical leaching, soil elution, chemical oxidation/reduction, phytoremediation and the like. Only few heavy metals can be enriched in the blocking landfill and solidification/stabilization; the phytoremediation only needs to reduce the pollution degree of heavy metals by a first mode through plants which absorb certain heavy metals exclusively; chemical methods such as chemical leaching, soil elution, chemical oxidation/reduction and the like are not suitable for being absorbed by plants or being integrated into underground water by changing the existence mode of heavy metals, but the existing chemical methods have limited capability of removing the heavy metals.
Therefore, it is necessary to provide a new method for rapidly reducing the heavy metal content in heavily polluted soil to solve the above problems.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for quickly reducing the content of heavy metals in heavily polluted soil, which can effectively reduce the content of heavy metals in the soil.
In order to solve the technical problems, the invention adopts a technical scheme that: the method for rapidly reducing the heavy metal content of the heavily polluted soil is provided, and comprises the following steps:
(1) adding lime with the soil mass percent of 0.2% into the heavy metal contaminated soil to carry out passivation reaction;
(2) separating the passivated soil into colloidal particles in the soil by using an ultrasonic separation method, and adding a flocculating agent into the soil colloidal solution to flocculate and precipitate the soil colloidal particles in the solution;
(3) adding an alkaline solution into the flocculated solution to remove heavy metal elements in the solution so as to enable the heavy metal elements to reach the standard of surface water;
(4) and adding a curing agent with the mass of 30% of that of the sediment into the flocculation sediment to ensure that the leaching toxicity is lower than the identification standard of hazardous wastes.
In a preferred embodiment of the invention, the ultrasonic separation method is to put the heavy metal contaminated soil into a settling tank, add water for wetting, stir and separate by ultrasonic oscillation, and settle in a room, wherein the settling time is determined according to a solution temperature and a settling table, as shown in table 1.
TABLE 1 soil colloid (. ltoreq.2 μm) extraction standing sedimentation time table
Further, the mass ratio of the heavy metal contaminated soil to water is 3: 100.
Further, the frequency of the ultrasonic wave is 40 KHz.
Further, the stirring rate was 30 rpm.
In a preferred embodiment of the invention, the flocculant is 0.5mol/L calcium chloride.
In a preferred embodiment of the present invention, in step (3), the alkaline solution is added as 0.5mol/L sodium hydroxide solution.
In a preferred embodiment of the invention, the curing agent is cement and lime in a mass ratio of 3: 2.
The invention has the beneficial effects that:
(1) according to the invention, 0.2% of lime is added into the heavy metal contaminated soil for passivation, so that the adsorption capacity of the soil colloid to heavy metals is increased by increasing the content of the colloid in the soil, and the soil colloid has a large surface area and more active sites, thereby increasing the percentage of the heavy metals in the soil colloid particles to the heavy metals in the soil;
(2) the passivated soil is subjected to ultrasonic separation to separate out soil colloid, and heavy metals in the soil colloid solution and the flocculation precipitation are separated out, so that the content of the heavy metals in the soil is effectively reduced, and the residual water can be recycled, thereby saving and protecting the environment;
(3) the invention has simple operation and high efficiency, and is suitable for wide popularization and application.
Drawings
FIG. 1 is a flow chart of the method for rapidly reducing the heavy metal content in heavily polluted soil according to the invention;
figure 2 is a bar graph of the percent reduction in soil heavy metals in two sets of experiments.
Detailed Description
The invention is further illustrated with reference to the following specific examples, which are not intended to be limiting.
Heavy metal heavily polluted soil is collected around a Guixi smelting plant in Guixi City in Jiangxi province, the geographical positions are 117 degrees 12'30.40 degrees from east longitude and 28 degrees 20'2.38 degrees from north latitude, the region is subtropical monsoon climate, the annual average precipitation is 1881.8 mm, and the annual average temperature is 18.4 ℃. The soil properties are: the pH value of the soil is 5.43, and the organic matter content is 21.68 g.kg-1CEC of 8.99 cmol.kg-1The total cadmium content is 1.86 mg/kg-1The total copper content is 2172.85 mg/kg-1. Cadmium in the soil exceeds 5.20 times and copper exceeds 42.46 times.
With reference to fig. 1, the assay was performed in two groups: 1) CK, adding no lime into the polluted soil, culturing for a week, air-drying, and performing ultrasonic separation; 2) SH, adding 0.2 percent (percentage by mass of soil) of lime into the polluted soil, performing passivation reaction for one week, air-drying, and performing ultrasonic separation.
Respectively taking 60g of each treated soil, adding 2000ml of pure water, wetting the soil for 3 minutes, starting to separate the soil by using ultrasonic waves while stirring, wherein the stirring speed is 30 revolutions per minute, the frequency is 40KHz, placing the soil in a sedimentation barrel for sedimentation, measuring the temperature of the solution by using a thermometer at 25 ℃, determining the sedimentation time to be 6h, 53min and 24s, slowly pouring the solution at the upper part, and measuring the content of heavy metal cadmium and copper in the soil after air-drying and weighing the soil at the lower part.
0.5mol/L calcium chloride is dripped into the solution to flocculate and precipitate soil colloid particles in the solution, and the mass of the soil particles subjected to flocculation and precipitation only accounts for 5-15% of the mass of the original soil, so that the soil is small in volume and easy to handle. And adding 2 drops of 0.5mol/L sodium hydroxide into the solution to remove heavy metals in the solution, pouring out the supernatant after 10 minutes, and measuring the content of the heavy metals of copper and cadmium. Adding a curing agent into the flocculated sediment, wherein the curing agent is cement and lime in a mass ratio of 3:2, the addition amount is 30% of the mass of the sediment, measuring the leaching toxicity after one week of curing reaction, and preferably, extracting the solid waste by using a sulfuric acid-nitric acid method (HJ/T299-2007).
The test results of the two sets of tests are respectively as follows:
through the soil which is cultured for one week by adding 0.2 percent lime and then subjected to ultrasonic separation, as shown in figure 2, namely SH treatment in the figure, the contents of heavy metals Cu and Cd in the soil are respectively reduced by 48.21 percent and 57.18 percent. Compared with the other group (CK) of soil without lime, the content of heavy metals Cu and Cd in the soil is obviously reduced. The lime with the concentration of 0.2% is added into the heavy metal contaminated soil for passivation, the content of colloid in the soil can be increased, in addition, the surface area of the soil colloid is large and has more active sites, so that the adsorption capacity of the soil colloid to heavy metals is stronger, the percentage of the heavy metals in the soil colloid particles to the heavy metals in the soil is increased, and the percentage can be increased from 20-30% to 40-60%.
The leaching toxicity of the flocculated sediment after solidification is lower than the hazardous waste identification standard, namely leaching toxicity identification (GB5085.3-2007), as shown in Table 2.
TABLE 2 flocculation precipitation after solidification heavy metal leaching toxicity (mg/kg)
Note:athe method is used for leaching toxicity identification for hazardous waste identification standard (GB 5085.3-2007).
The content of heavy metals in the flocculated residual water can meet the quality standard of surface water environment quality, namely the second-class water quality standard, and can be recycled, as shown in Table 3.
TABLE 3 heavy metal content (mg/kg) in the flocculated residual water
Note:bthe method is a two-class standard of surface water environmental quality standard (GB 3838-2002).
The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all equivalent flow transformations and combinations made by the present specification, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (7)
1. A method for rapidly reducing the heavy metal content of heavily polluted soil comprises the following steps:
(1) adding lime with the soil mass percent of 0.2% into the heavy metal contaminated soil to carry out passivation reaction;
(2) separating the passivated soil into colloidal particles in the soil by using an ultrasonic separation method, and adding a flocculating agent into the soil colloidal solution to flocculate and precipitate the soil colloidal particles in the solution; the ultrasonic separation method comprises the steps of putting heavy metal contaminated soil into a settling tank, adding water for wetting, stirring and carrying out ultrasonic oscillation separation, settling indoors, and determining settling time according to a solution temperature and a settling table;
(3) adding an alkaline solution into the flocculated solution to remove heavy metal elements in the solution so as to enable the heavy metal elements to reach the standard of surface water;
(4) and adding a curing agent with the mass of 30% of that of the sediment into the flocculation sediment to ensure that the leaching toxicity is lower than the identification standard of hazardous wastes.
2. The method for rapidly reducing the heavy metal content in the heavily polluted soil according to claim 1, wherein the mass ratio of the heavy metal polluted soil to the water is 3: 100.
3. The method for rapidly reducing the heavy metal content in the heavily polluted soil according to claim 1, wherein the frequency of the ultrasonic wave is 40 KHz.
4. The method for rapidly reducing the heavy metal content of heavily polluted soil according to claim 1, wherein the stirring rate is 30 rpm.
5. The method for rapidly reducing the heavy metal content of heavily polluted soil according to claim 1, wherein the flocculating agent is 0.5mol/L calcium chloride.
6. The method for rapidly reducing the heavy metal content in the heavily polluted soil according to claim 1, wherein in the step (3), the alkaline solution is added to be 0.5mol/L sodium hydroxide solution.
7. The method for rapidly reducing the heavy metal content in the heavily polluted soil according to claim 1, wherein the curing agent is cement and lime in a mass ratio of 3: 2.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101811133A (en) * | 2010-04-27 | 2010-08-25 | 河海大学 | Ultrasonic remediating method for heavy metal polluted soil/slurry |
| CN106563692A (en) * | 2015-10-08 | 2017-04-19 | 韩国地质资源研究院 | Method of restoring heavy-metal-contaminated soil |
| CN107639108A (en) * | 2017-07-21 | 2018-01-30 | 郑旭东 | A kind of Ex-situ washing remediation of heavy-metal contaminated soil |
| CN108273846A (en) * | 2018-01-11 | 2018-07-13 | 湖南美源环保科技有限公司 | A kind of efficient heavy soil-repairing agent and its restorative procedure |
| CN108329922A (en) * | 2018-02-01 | 2018-07-27 | 吴申龙 | A kind of composite material and preparation method for administering heavy metal soil |
| CN108410473A (en) * | 2018-03-19 | 2018-08-17 | 吴洪生 | A kind of farmland soil heavy metals passivation agent and process for producing same and application |
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- 2018-11-20 CN CN201811382511.9A patent/CN109647869B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101811133A (en) * | 2010-04-27 | 2010-08-25 | 河海大学 | Ultrasonic remediating method for heavy metal polluted soil/slurry |
| CN106563692A (en) * | 2015-10-08 | 2017-04-19 | 韩国地质资源研究院 | Method of restoring heavy-metal-contaminated soil |
| CN107639108A (en) * | 2017-07-21 | 2018-01-30 | 郑旭东 | A kind of Ex-situ washing remediation of heavy-metal contaminated soil |
| CN108273846A (en) * | 2018-01-11 | 2018-07-13 | 湖南美源环保科技有限公司 | A kind of efficient heavy soil-repairing agent and its restorative procedure |
| CN108329922A (en) * | 2018-02-01 | 2018-07-27 | 吴申龙 | A kind of composite material and preparation method for administering heavy metal soil |
| CN108410473A (en) * | 2018-03-19 | 2018-08-17 | 吴洪生 | A kind of farmland soil heavy metals passivation agent and process for producing same and application |
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