CN108971215B

CN108971215B - Heavy metal contaminated soil remediation method based on ultrasonic suction filtration

Info

Publication number: CN108971215B
Application number: CN201810595297.9A
Authority: CN
Inventors: 刘莉莉; 陈鑫; 唐周; 周纯淳; 武广哲; 董永成; 赵翰斌
Original assignee: East China University of Science and Technology
Current assignee: East China University of Science and Technology
Priority date: 2018-06-11
Filing date: 2018-06-11
Publication date: 2020-07-24
Anticipated expiration: 2038-06-11
Also published as: CN108971215A

Abstract

A method for restoring heavy metal contaminated soil based on ultrasonic suction filtration comprises the steps of firstly spraying or soaking organic polybasic acid on soil to be processed to achieve dissociation of multi-valence state heavy metal ions, then carrying out ultrasonic treatment through a roller pin type ultrasonic vibration device to enable the surface layer of the soil to form a continuous water-filled phase, and finally quickly suction filtering and recovering a heavy metal-containing water solution in soil pores through a vacuum pad. According to the chemical characteristics of the polluted heavy metals in the soil, the method adopts the targeted organic polybasic acid for soaking, has the characteristics of short treatment period, high heavy metal removal efficiency, high environmental ecological safety and the like, and can be widely used for treating and repairing various heavy metal polluted soils.

Description

Heavy metal contaminated soil remediation method based on ultrasonic suction filtration

Technical Field

The invention relates to the field of soil remediation technology, in particular to a heavy metal contaminated soil remediation method based on ultrasonic suction filtration.

Background

The heavy metal contaminated soil treatment technology comprises physical, chemical and biological methods, and the methods have the defects of low pollutant removal efficiency, high cost, long period and the like, and even after treatment, the land can not be continuously cultivated. For example, in the electrokinetic remediation by a physical method, in order to improve the migration efficiency of heavy metal ions in a soil porous medium, the pH value of a soil solution needs to be greatly reduced, and a continuous stable electric field needs to be applied to the soil, so that the cost is high and the time consumption is long; the chemical fixing technology is characterized in that a soil conditioner is added to change the physical and chemical properties of soil, and the existence state of heavy metals in the soil is changed through the adsorption, precipitation or coprecipitation of the heavy metals, so that the bioavailability of the heavy metals is reduced, the fixing efficiency is poor, and the heavy metals can be continuously accumulated in crops in the cultivation process; the plant extraction technology is characterized in that some heavy metal super-enriched plants are planted, the root systems of the heavy metal super-enriched plants are used for enriching heavy metals in polluted soil to the overground parts of the plants, and the heavy metals in the polluted soil are removed by regular harvesting, so that the defects of underground enrichment efficiency, long treatment period and the like exist.

Disclosure of Invention

The invention provides a method for restoring heavy metal polluted soil based on ultrasonic suction filtration, which is a method for removing heavy metal ions by soaking in targeted organic polybasic acid according to the chemical characteristics of polluted heavy metals in soil and then carrying out ultrasonic treatment and vacuum suction filtration.

The invention is realized by the following technical scheme:

the method comprises the steps of firstly spraying or soaking the soil to be treated with organic polybasic acid to free the polyvalent heavy metal ions, then carrying out ultrasonic treatment through a roller pin type ultrasonic vibration device to form a continuous water-filled phase on the surface layer of the soil, and finally rapidly filtering and recovering the heavy metal-containing aqueous solution in soil pores through a vacuum pad.

The soaking is as follows: aiming at the chemical characteristics of the polluted heavy metal in the soil, the method adopts the composite organic acid with the effective component of aminocarboxylic acids, hydroxycarboxylic acids or hydroxylamino carboxylic acid chelating agents to soak, and realizes the dissociation of the multivalent heavy metal ions through the leaching and complexing action of the organic polybasic acid on the heavy metal ions.

The organic polybasic acid comprises: disodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, ammonium citrate, or a combination thereof.

The organic polybasic acid is preferably: aiming at the Pb and Zn polluted soil, a mixed solution of disodium ethylene diamine tetraacetate and ammonium citrate with a molar ratio of 1:3 is adopted, and aiming at the Cd and Cr polluted soil, a mixed solution of diethylenetriamine pentaacetic acid and ammonium citrate with a molar ratio of 1:5 is adopted.

And (3) soaking, preferably soaking in water for 12-48h, adding the compound organic polybasic acid, and continuing soaking for 6-24 h.

The ultrasonic treatment is preferably carried out by turning over, namely, but not limited to a sickle-type turning machine is adopted to turn over the surface layer of the sprayed or soaked soil.

And in the ultrasonic treatment, the rolling needle type ultrasonic vibration device is driven by the cultivator to carry out ultrasonic vibration treatment on the surface layer of the soil for 2 hours.

The depth of the surface soil is 10-30 cm.

The rapid suction filtration of the vacuum pad refers to: covering a vacuum pad on the continuous water filling phase, realizing continuous vacuum suction filtration on the polluted area by using a vacuum water suction machine, extracting the water solution containing the heavy metals in the soil pores, and realizing the separation of the heavy metals in the polluted soil.

The recovery refers to: and respectively adding corresponding chemical precipitating agents such as lime, a vulcanizing agent, iron salt and the like into the extracted soil solution after being collected by a tank car according to the composition of the heavy metals and the added compound organic polybasic acid to realize the precipitation separation of the heavy metals.

Technical effects

Compared with the prior art, the method is based on the systematic research of the occurrence form of the heavy metal in the soil, the effective separation of the heavy metal and soil particles is realized by using polybasic organic acid and ultrasonic treatment, the continuous suction filtration of the soil solution and the chemical precipitation treatment of the suction filtrate are realized by combining the vacuum continuous suction filtration technology, the rapid and efficient remediation of the heavy metal contaminated soil can be realized, the influence of the residual medicament is small, and the damage to the soil is low.

Drawings

FIG. 1 is a side view of the roller pin ultrasonic vibrator of the present invention;

FIG. 2 is an axial view of the ultrasonically vibrated roller pin of the present invention;

in the figure: the device comprises an energy converter 1, an amplitude transformer 2, a rolling shaft 3, a roller pin 4, a filter cloth 5, a flexible pressing pad 6 and an aluminum alloy buckle edge 7.

Figure 3 is a schematic view of the absorbent vacuum pad of the present invention.

Detailed Description

Example 1

In the embodiment, a terrace polluted by the weathered slag leachate near a certain lead-zinc ore in Hunan province is used for carrying out experiments, the soil is viscous red soil, the pH value is 7.62, the organic matter content is low and is only 4.8g/kg, and the conductivity is obviously high and is about 1140 mu S/m; the mean values of the total Pb and Zn concentrations were 1624mg/kg and 2287mg/kg, respectively, and the main concentrations are shown in the following table.

The specific steps of the embodiment include:

① ploughing by a surface layer ploughing machine after cleaning the plants on the surface, injecting water and soaking for 48h, and then dissolving disodium ethylene diamine tetraacetate and ammonium citrate with the molar ratio of 1:3 uniformly and spraying the solution on the surface layer of the polluted land;

② soaking for 6h, and driving a roller pin type ultrasonic vibration device to perform ultrasonic vibration treatment on the surface soil for 2h by using a cultivator;

as shown in fig. 1 and 2, the roller-pin ultrasonic vibration device includes: the horn 2 and a plurality of groups rotate the roller 3, the transducer 1 and the needle roller 4 arranged thereon, wherein: the energy converter 1 is arranged inside the roller 3 and connected with a high-frequency power supply, the roller pin 4 is fixedly arranged outside the roller 3, the energy converter 1 embedded in the roller 3 generates mechanical vibration with the same frequency as current through high-frequency alternating current, and amplitude is transmitted to the roller pin 4 fixed on the roller 3 by the aid of the amplitude transformer 2, so that the roller pin 4 generates ultrasonic vibration.

The length of the roller pins is 15cm, and the transverse distance is 15 cm.

③ in turn using 4 × 6m²Covering soil with a vacuum pad, connecting with a tank wagon, starting a vacuum water suction machine for suction filtration (single suction filtration for 0.5h), standing the soil solution collected in the tank wagon, and then standing according to the mass ratio of 0.8kg/m³Adding lime complexing agent to destabilize the chelating agent, precipitating and recovering heavy metals.

As shown in fig. 3, the vacuum pad includes: the device comprises a filter cloth 5 contacted with a continuous water filling phase, a flexible pressing pad 6 arranged on the filter cloth 5 and aluminum alloy fastening edges 7 arranged on the periphery of the filter cloth 5 and the flexible pressing pad 6, wherein a channel used for connecting a vacuum pump is arranged on the flexible pressing pad 6, the filter cloth 5 covers the continuous water filling phase, and the aluminum alloy fastening edges 7 temporarily isolate covering area pulpous soil, so that a relatively sealed soil layer is provided for the continuous suction filtration of the vacuum pump.

After the treatment by the method, the total concentration mean values of Pb and Zn in the terraced fields are 219mg/kg and 193mg/kg respectively, which reach the GB15618-1995 secondary standard, and the bioavailability is greatly reduced.

Example 2

In the embodiment, a farmland polluted by industrial wastewater in Guangdong is tested, the soil is viscous brown soil, the pH value is weak and acidic and is 6.45, the organic matter content is normal and is 12.7g/kg, and the conductivity is high and is about 820 mu S/m; the total concentration mean values of the heavy metals Cd and Cr are 470 mug/kg and 191.5mg/kg respectively, and the main storage states are shown in the following table.

The specific steps of the embodiment include:

① harvesting the cultivated crops, soaking in water for 24h, ploughing 20cm soil on the surface layer by a surface layer ploughing machine, and crushing, and then dissolving diethylenetriamine pentaacetic acid and ammonium citrate at a molar ratio of 1:5 uniformly and spraying onto the surface layer of the polluted soil;

② driving roller pin type ultrasonic vibrator (roller pin length 20cm, transverse spacing 20cm) with a cultivator to perform ultrasonic vibration treatment on surface soil for 3 h;

③ use 4 × 6m²Covering soil with a vacuum pad, connecting with a tank wagon, starting a vacuum water suction machine for suction filtration (single suction filtration for 1h), standing the soil solution collected in the tank wagon, and then standing the soil solution according to the mass ratio of 1.2kg/m³Lime is added to destabilize the precipitate of the chelating agent to recover the heavy metals.

The total concentration mean values of Cd and Cr in the soil treated by the method are 241 mug/kg and 67mg/kg respectively, which basically reach the GB15618-1995 secondary standard, and the bioavailability is greatly reduced.

The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. The method for restoring the heavy metal contaminated soil based on ultrasonic suction filtration is characterized by comprising the steps of firstly spraying or soaking organic polybasic acid on the soil to be treated to free polyvalent heavy metal ions, then carrying out ultrasonic treatment through a roller pin type ultrasonic vibration device to enable the surface layer of the soil to form a continuous water-filled phase, and finally quickly suction-filtering and recovering a heavy metal-containing aqueous solution in soil pores through a vacuum pad;

the soaking is as follows: aiming at the chemical characteristics of the polluted heavy metal in the soil, soaking the polluted heavy metal in a composite organic acid of which the effective component is an amino carboxylic acid, a hydroxycarboxylic acid or a hydroxylamino carboxylic acid chelating agent, and realizing the dissociation of the multivalent heavy metal ions through the leaching and complexing action of organic polybasic acid on the heavy metal ions;

the roller pin type ultrasonic vibration device comprises: the horn and a plurality of groups rotate roller bearing, transducer and the kingpin of setting up on it, wherein: the energy converter is arranged in the roller and connected with a high-frequency power supply, the roller pins are fixedly arranged outside the roller, the energy converter embedded in the roller generates mechanical vibration with the same frequency as current through high-frequency alternating current, and amplitude is transmitted to the roller pins fixed on the roller through the amplitude transformer, so that the roller pins generate ultrasonic vibration;

the rapid suction filtration of the vacuum pad refers to: covering a vacuum pad on the continuous water filling phase, realizing continuous vacuum suction filtration on a polluted area by using a vacuum water suction machine, extracting the water solution containing heavy metals in soil pores, and realizing the separation of the heavy metals in the polluted soil;

the vacuum pad comprises: the filter cloth is in contact with the continuous water filling phase, the flexible pressing pad is arranged on the filter cloth, the aluminum alloy fastening edges are arranged on the periphery of the filter cloth and the flexible pressing pad, a channel used for connecting a vacuum pump is arranged on the flexible pressing pad, the filter cloth covers the continuous water filling phase, and the covering area pulpous soil is temporarily isolated through the aluminum alloy fastening edges, so that a relatively sealed soil layer is provided for the continuous suction filtration of the vacuum pump.

2. The method of claim 1, wherein the organic polyacid comprises: disodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, ammonium citrate, or a combination thereof.

3. The method as set forth in claim 1, wherein said organic polyacid is: aiming at the Pb and Zn polluted soil, a mixed solution of disodium ethylene diamine tetraacetate and ammonium citrate with a molar ratio of 1:3 is adopted, and aiming at the Cd and Cr polluted soil, a mixed solution of diethylenetriamine pentaacetic acid and ammonium citrate with a molar ratio of 1:5 is adopted.

4. The method as claimed in claim 1, wherein the soaking is carried out by adding the compound organic polybasic acid after the pre-soaking in water for 12-48h for further soaking for 6-24 h.

5. The method as claimed in claim 1, wherein the ultrasonic treatment is previously carried out by turning the surface of the soaked soil by a sickle-type turning machine.

6. The method as claimed in claim 1, wherein the ultrasonic treatment is carried out by driving a roller-type ultrasonic vibrator for 2h by a tiller.