CN112058894A

CN112058894A - Method for carrying out enhanced electrokinetic remediation on heavy metal contaminated soil by GLDA (Global System for Mobile communications)

Info

Publication number: CN112058894A
Application number: CN202010803742.3A
Authority: CN
Inventors: 杨晓娟; 仓龙; 吉乔伟; 解继业; 周明珠; 王霞; 周东美
Original assignee: PowerChina Huadong Engineering Corp Ltd; Institute of Soil Science of CAS
Current assignee: PowerChina Huadong Engineering Corp Ltd; Institute of Soil Science of CAS
Priority date: 2020-08-11
Filing date: 2020-08-11
Publication date: 2020-12-11

Abstract

The invention relates to a method for GLDA enhanced electrokinetic remediation of heavy metal contaminated soil. The invention aims to provide a method for GLDA enhanced electrokinetic remediation of heavy metal contaminated soil, so as to increase the mobility of heavy metals, improve the removal efficiency of the heavy metals and reduce environmental risks. The technical scheme of the invention is as follows: a method for strengthening electrokinetic remediation of heavy metal contaminated soil by GLDA is characterized by comprising the following steps: GLDA was used as complexing agent. The invention is suitable for the technical field of environmental protection.

Description

Method for carrying out enhanced electrokinetic remediation on heavy metal contaminated soil by GLDA (Global System for Mobile communications)

Technical Field

The invention relates to a method for GLDA enhanced electrokinetic remediation of heavy metal contaminated soil. Is applicable to the technical field of environmental protection.

Background

Contaminated soil remediation is a technology which needs to be developed urgently at present, because soil pollution can cause serious environmental problems, and human health and social development are affected. Heavy metals cannot be degraded and disappear in the environment, can enter a human body through a food chain, and have carcinogenic, teratogenic and mutagenic effects on human beings. According to the national soil pollution survey bulletin issued in 2014, the point position exceeding rate of heavy metals in the national soil reaches 19.4 percent and is far higher than that of organic matter polluted soil, so that the remediation of the heavy metal polluted soil is one of the great requirements of the remediation of the polluted soil.

At present, the remediation of the heavy metal contaminated soil mainly comprises a soil-requisition method, a solidification/stabilization method, a leaching method, a phytoremediation method and the like, and compared with the remediation technologies, the electric remediation has the characteristics of rapidness, low cost, in-situ and heavy metal total removal, is particularly suitable for the deep and severe low-permeability contaminated soil, and is a competitive heavy metal contaminated soil remediation technology. In order to improve the mobility of heavy metals in soil in electrokinetic remediation, a complexing agent is generally added to the soil to activate the heavy metals and improve the removal efficiency of the heavy metals. Traditional complexing agents, such as EDTA (ethylene diamine tetraacetic acid), DTPA (diethyltriamine pentaacetic acid) and the like, are difficult to degrade in the environment and have higher secondary pollution risk (CN201510815235.0), while biodegradable complexing agents, such as citric acid, EDDS (ethylenediamine disuccinic acid) and the like, have the defects of low heavy metal complexing capacity, high price and the like respectively and are difficult to apply in repair engineering.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the existing problems, the method for strengthening the electrokinetic remediation of the heavy metal contaminated soil by the GLDA is provided, so that the mobility of the heavy metal is increased, the removal efficiency of the heavy metal is improved, and the environmental risk is reduced.

The technical scheme adopted by the invention is as follows: a method for strengthening electrokinetic remediation of heavy metal contaminated soil by GLDA is characterized by comprising the following steps: GLDA was used as complexing agent.

Arranging a negative/positive electrode pair at two ends of the polluted soil;

adding a GLDA solution on the surface of the soil or in an electrode pool;

and (5) completing soil remediation after the treatment by the direct current electric field.

Controlling the pH value of the anode and the cathode to be neutral, and respectively arranging an anion membrane and a cation membrane on the anode and the cathode.

The direct current voltage gradient between the cathode and the anode is 5-150V/m.

The concentration of the GLDA is 5-50 mmol/L.

The GLDA is glutamic acid diacetic acid tetrasodium salt.

The invention has the beneficial effects that: according to the invention, GLDA is used as a complexing agent, so that the mobility of heavy metals is obviously increased, the removal efficiency of the heavy metals is improved, the influence on the soil property is reduced, and the electric remediation energy consumption is reduced.

Drawings

FIG. 1 is a graph showing the change of heavy metal content in soil after electrokinetic treatment with different biodegradable complexing agents.

FIG. 2 is a graph showing the change of heavy metal content in soil after electrokinetic treatment with GLDA of different concentrations.

FIG. 3 is a graph showing the change in soil pH and EC after enhanced electrokinetic treatment with GLDA in different pH control modes.

FIG. 4 is a graph showing the variation of heavy metal content in soil after enhanced electrokinetic treatment of GLDA by different pH control modes.

Detailed Description

The embodiment is a method for restoring heavy metal contaminated soil by GLDA enhanced electrokinetic, wherein a cathode/anode pair (electrode material is graphite, iron, titanium, stainless steel or alloy) is arranged at two ends of the contaminated soil, GLDA solution serving as a complexing agent is added on the soil surface or an electrode pool, the pH value of the whole system is controlled according to needs, and the soil restoration can be completed after the treatment by a direct current electric field.

The pH control method in this example includes controlling the pH to be neutral at the anode and the cathode, and arranging an anion membrane and a cation membrane at the anode and the cathode simultaneously. GLDA is glutamic acid diacetic acid tetrasodium salt; the concentration of GLDA is 7.1-71 mmol/kg; the DC voltage gradient between the cathode and the anode is 5-150V/m.

In the embodiment, a test device with the patent number of 201120524796.2 is adopted to carry out the reinforced electric remediation research of the heavy metal contaminated soil:

1. electric remediation of heavy metal contaminated soil by different biodegradable chelating reagents

The experimental design is shown in table 1, three chelating agents (LA (lactic acid), CA (citric acid) and GLDA) are adopted, the adding amount is 5mmol, the chelating agents are prepared into 50ml of solution (the concentration is 0.1mol/L), the adding mode is surface adding, each soil column is filled with 700g of soil (the adding concentration of GLDA is 7.1mmol/kg), the applied voltage gradient is 1V/cm, and the treatment time is 8 d.

Table 1. test design for strengthening electrokinetic remediation of heavy metal contaminated soil by different biodegradable complexing agents

FIG. 1 is the change in Cu and Ni content of soil after electrokinetic remediation. The removal rates of the different treatments T1-T4 on the soil Cu are respectively 4.2%, 9.5%, 10.5% and 11.1%. The Cu content of the soil at two ends is obviously reduced in the T3 and T4 treatment, while the Cu content of the S2 section is obviously increased, and an obvious aggregation phenomenon is shown, which is often caused when the heavy metal polluted soil is repaired by the chelation-enhanced electrokinetic remediation, and is mainly caused by the fact that a part of heavy metal chelate compounds are decomposed after moving to an anode pool, so that the heavy metals are moved into the soil again. The removal rules of different treatments on the soil Ni are consistent, the Ni content of the soil is gradually increased from the anode to the cathode, and the removal rates are respectively 2.6% (T1), 5.7% (T2), 6.1% (T3) and 6.9% (T4).

Comparing different treatments comprehensively, the removal rate of GLDA to heavy metals is higher than that of other treatments, and secondly, LA is consistent with the extraction capability results of different chelating agents to different heavy metals in the extraction test. From the viewpoint of the removal rate of the total amount of the heavy metals in the soil, the removal rate of the heavy metals is not high in general, which may be related to the lower dosage of the chelating agent and the form of the heavy metals in the soil. In general, the proportion of the active heavy metal forms in the actual contaminated soil is small, and the heavy metal forms (iron-manganese combined state, organic combined state, residue state and the like) which are combined with a large amount of soil are not easy to activate and move.

2. Enhanced electrokinetic remediation of heavy metal contaminated soil by GLDA (Global System for Mobile communications) with different concentrations

The experimental design is shown in table 2. GLDA is selected as a chelating agent, the adding amount is 5, 20 and 50mmol, the GLDA is prepared into 50ml of solution, the adding mode is surface adding, each soil column is 700g (the adding concentration of GLDA is 7.1, 28.4 and 71mmol/kg respectively), the applied voltage gradient is 1V/cm, and the treatment time is 8 d.

Table 2. test design for enhanced electrokinetic remediation of heavy metal contaminated soil by GLDA with different concentrations

FIG. 2 is the change in Cu, Ni, Cr and hexavalent chromium content of the soil after electrokinetic remediation. The removal rates of different treatments T5-T7 on soil Cu are respectively 11.1%, 15.8% and 15.2%, and the removal rate of medium-high concentration GLDA (T6 and T7) on Cu is higher than that of low concentration GLDA (T5). Cu on the section of the soil S2 has obvious aggregation phenomenon, and the aggregation phenomenon is not obvious when the concentration of GLDA is higher, probably because the quantity of GLDA is far higher than that of heavy metal in the soil, the heavy metal generated by decomposing the heavy metal chelate by the anode is chelated again and is not easy to migrate into the soil body. The removal rate of the different treatments to the soil Ni is respectively 6.9% (T5), 22.1% (T6) and 18.2% (T7), wherein the removal rate of the medium-concentration GLDA to the Ni is the highest. By comprehensively comparing different treatments, the GLDA with the medium concentration of 28.4mmol/kg is suitable for the electrokinetic remediation treatment.

3. Method for strengthening GLDA complexing electrokinetic remediation of soil polluted by heavy metals by different pH control modes

The experimental design is shown in table 3. Controlling the pH value of a cathode to be 4, not adding a chelating agent as a control (T8), using GLDA as a chelating agent, dividing into cathode and anode pH control 6 treatment (T9) and cathode and anode solution mixing treatment (T10) with an ionic membrane arranged on two electrodes, wherein the adding amount is 5mmol, the adding mode is surface adding, each earth pillar is 700g (the adding concentration of GLDA is 7.1mmol/kg), the applied voltage gradient is 1V/cm, and the treatment time is 8 d.

Table 3. test design of GLDA enhanced electrokinetic remediation of heavy metal contaminated soil by different pH control modes

FIG. 3 is the change in soil pH and EC after electrokinetic treatment. The T8 treatment controlled the cathode pH to 4, making the entire column acidic and increasing gradually from anode to cathode with a minimum pH of 2.11, appearing at S1 cross section. The pH of the T9 and T10 treated soils was substantially neutral, indicating that the pH control of T9 and T10 was better and also beneficial in mitigating the adverse effects of electrokinetic remediation on soil pH. Soil EC data showed the highest EC value for T8 treated soil, which was associated with the addition of large amounts of acid to control cathode pH. The soil EC treated by T9 was close to the original soil EC value, indicating that the treatment had a lesser effect on soil EC. The EC of the soil treated by T10 is higher than the original EC value of the soil, but is obviously lower than that of the soil treated by T9, and is a treatment which has less influence on the EC of the soil.

FIG. 4 is the change in Cu, Ni, Cr and hexavalent chromium content of the soil after electrokinetic remediation. Although the T8 treatment significantly reduced the Cu content of the soil at the S1-S3 sections, a large amount of Cu was accumulated at the S4 and S5 sections, and the total removal rate was only 0.4%, indicating that Cu was not removed from the soil, which may be related to the shorter treatment time of 8 d. The total Cu removal rates of T9 and T10 were 12.9% and 20.1%, respectively, and the distribution of total Cu at each section was relatively close. The removal rule of the different treatments on the total Ni of the soil is similar to that of Cu, and the removal rates are-0.9% (T8), 24.8% (T9) and 27.7% (T10) respectively. Although the total Ni of the soil with the sections S1-S4 was significantly reduced in the T8 treatment, a large amount of Ni accumulated in the section S5 and was not removed from the soil, which is related to the shorter treatment time in this study. From the power consumption of table 4, both the power consumption and the energy consumption per removal rate of the ion membrane treatment are superior to those of other treatments. By comprehensively comparing different treatments, the ion membrane enhanced GLDA electro-kinetic remediation treatment is a more suitable electro-kinetic remediation treatment measure.

Claims

1. A method for strengthening electrokinetic remediation of heavy metal contaminated soil by GLDA is characterized by comprising the following steps: GLDA was used as complexing agent.

2. The GLDA enhanced electrokinetic remediation method of heavy metal contaminated soil of claim 1, wherein:

arranging a negative/positive electrode pair at two ends of the polluted soil;

adding a GLDA solution on the surface of the soil or in an electrode pool;

3. The GLDA enhanced electrokinetic remediation method of heavy metal contaminated soil of claim 2, wherein: controlling the pH value of the anode and the cathode to be neutral, and respectively arranging an anion membrane and a cation membrane on the anode and the cathode.

4. The GLDA enhanced electrokinetic remediation method of heavy metal contaminated soil of claim 2, wherein: the direct current voltage gradient between the cathode and the anode is 5-150V/m.

5. The GLDA enhanced electrokinetic remediation method of heavy metal contaminated soil according to claim 1 or 2, wherein: the concentration of the GLDA is 7.1-71 mmol/kg.

6. The GLDA enhanced electrokinetic remediation method of heavy metal contaminated soil according to claim 1 or 2, wherein: the GLDA is glutamic acid diacetic acid tetrasodium salt.