CN101138767A - A kind of remediation method of heavy metal polluted soil - Google Patents

Abstract

The present invention discloses a method of repairing soil polluted by heavy metal. Procedures of repair method are as following: (1) both sides of the soil are provided with electrode wells. Parallel negative electrode and positive electrode are installed in the electrode well, spaced at 0.1 to 1m. When the positive electrode adopts iron or aluminum, the negative electrode adopts manganese dioxide, carbon or copper; when the positive electrode adopts the carbon, the negative electrode adopts manganese dioxide; (2) the electrode well is filled with flushing fluid whose level is higher than that of the soil, thus, making materials of the negative and positive electrodes soaked in the flushing liquid; the flushing liquid is water or acid solution whose concentration is less than 2mol/l; (3) the negative and positive electrodes are connected and conduction time lasts for 30 to 500 days. The present invention makes negative and positive electrodes made up of different materials to have electrode reaction resulting from electrode potential of electrode surface, thus, forming primary batteries to produce potential difference to have pollutants in the soil between the negative and positive electrodes remove. Therefore, requirement for high consumption of additional power can be prevented. The method has advantages of low consumption, environment-friendly, good treatment effect and easy operation.

Description

A kind of remediation method of heavy metal polluted soil

technical field

The invention belongs to the technical field of soil remediation, and in particular relates to a method for remediating heavy metal polluted soil.

technical background

With the development of industrial and agricultural production, a large amount of heavy metal pollutants enter the environment and eventually accumulate in the soil, making soil pollution more and more serious. The direct economic loss caused by the production of agricultural products containing heavy metals in our country reaches 20 billion yuan every year, which is a very serious problem. Soil pollution has become one of the major obstacles restricting the international trade of agricultural products and the sustainable development of society in my country, and the contaminated soil is in urgent need of restoration.

The current contaminated soil remediation technologies mainly include soil replacement method, incineration method, solvent/surfactant leaching, steam extraction, chemical oxidation and biological treatment (including plant treatment), etc. Both the soil replacement method and the incineration method consume a lot of manpower and material resources. Biological treatment requires that the treated substances have good bioavailability and require highly selective strains. Other methods require the treated soil to have better permeability. Electrokinetic soil remediation technology is a method specially developed for low-permeability cohesive soils. It uses electromigration and electrodialysis to remove pollutants from the soil and realize the remediation of contaminated soil.

However, the traditional electrokinetic soil remediation technology consumes a lot of electric energy. According to the statistics of foreign authoritative organizations, the direct power consumption of repairing each square of soil is about 100 US dollars. In addition, this technology will cause damage to the soil while removing pollutants in the soil, such as acidifying the soil in the anode area and alkalizing the soil in the cathode area. These two factors, especially high energy consumption, directly limit the practical engineering application of electrodynamic technology. Therefore, it is very necessary to reduce the power loss of electrokinetic technology and at the same time reduce the damage to the treated soil area.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the existing electrodynamic soil remediation technology, and provide a remediation method for heavy metal-contaminated soil. The method does not consume electric energy, has very little damage to the soil, and has the advantages of low operating cost and environmental friendliness.

The repair method of heavy metal polluted soil provided by the invention, its steps are:

(1) Electrode wells are arranged on both sides of the soil to be treated, and negative and positive electrodes are installed in the electrode wells, the electrodes are placed in parallel, and the electrode spacing is 0.1-1m; when the anode material is iron or aluminum, the cathode adopts manganese dioxide, carbon or copper; When carbon is used as the anode material, manganese dioxide is used as the cathode;

(2) Fill the flushing liquid in the above-mentioned electrode well, make the liquid level of the electrode well higher than the height of the soil to be treated, and soak the cathode and anode materials in the flushing liquid; the flushing liquid is water or an acid solution with a concentration less than or equal to 2mol/L, the acid is sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, ethylenediaminetetraacetic acid or citric acid;

(3) Connect the cathode and anode, and the power-on time is between 30-500 days.

The method of the present invention uses materials of different properties (such as iron and carbon) as cathode and anode, so that electrode reactions with different electrode potentials occur on the electrode surface to form a primary battery, thereby generating a potential difference to drive the migration of pollutants in the soil between the cathode and anode, avoiding High energy consumption required for external power supply. The method can also increase the potential difference by connecting multiple primary batteries in series, thereby improving the treatment effect. Compared with the traditional electrokinetic technology, the galvanic battery soil remediation technology does not consume electric energy, has very little damage to the soil, and has the advantages of low operating cost and environmental friendliness. In a word, the method of the present invention has the advantages of safety, reliability and easy operation, and has the value of application and popularization.

Description of drawings

Fig. 1 is a schematic diagram of the principle of the present invention.

Figure 2 is a diagram of a soil remediation device with a single primary battery.

Fig. 3 is a diagram of a soil remediation device in which multiple primary batteries are connected in series.

Figure 4 shows the treatment effect of primary battery technology on copper-contaminated soil.

Figure 5 shows the treatment effect of galvanic battery technology on cadmium-contaminated soil.

Detailed ways

The method of the invention uses the electric field generated by the primary battery to drive the heavy metal pollutants to migrate out of the soil, thereby achieving the repair of the polluted soil. As shown in Figure 1, materials with different properties are used as cathode and anode on both sides of the polluted soil, and the cathode and anode are connected by wires to form a primary battery, which drives the electromigration of inorganic ions in the polluted soil, positive ions migrate to the cathode, and negative ions migrate to the anode .

The method of the present invention will be further described below in conjunction with the accompanying drawings.

①. Electrode setting: set electrode wells on both sides of the soil to be treated, install electrodes in the electrode wells, place the electrodes in parallel and symmetrically, and the electrode spacing is 0.1-1m, use wires to connect the cathode and anode to form a complete primary battery, as shown in Figure 2 Or set up multiple electrode wells, install cathodes and anodes alternately, and use wires to connect the cathode of one primary battery with the anode of the adjacent primary battery to realize the series connection of multiple primary batteries, as shown in Figure 3; the anode is selected to be reductive Better materials, such as iron, aluminum, and carbon, and materials with better oxidizing properties, such as carbon and manganese dioxide, are used for the cathode to ensure that different electrode reactions occur at the cathode and anode.

②. Flushing solution setting: Fill the electrode well with 0-2mol/L acid solution (sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, ethylenediaminetetraacetic acid, citric acid), and connect with the flushing solution storage tank through the pump to ensure that the electrode well The liquid level is higher than the height of the treated soil, and the soil has a certain humidity, so that the cathode and anode materials are soaked in the flushing solution.

③Connection treatment: Use wires to connect the cathode and anode, so that the treated soil is under the action of the weak electric field generated by the cathode and anode, and the pollutants in it will undergo electrokinetic migration effect, positive ions migrate to the anode (the cathode of the primary battery), and negative ions migrate to the anode. The cathode (the anode of the primary battery) migrates, and the electrodialysis migration occurs in the gap water to make the pollutants migrate accordingly. To intensify the treatment process, the soil can be sprayed with flushing fluid during operation. Depending on the type and concentration of pollutants, the power-on time generally lasts between 30-500 days.

Example 1: Copper is a typical heavy metal pollutant, which is very harmful to the environment. Take 150g of simulated copper-contaminated soil, the copper content is 170mg/kg, and the moisture content is 50%, and put it into the galvanic reaction device (Φ5cm×8cm). The anode uses iron filings, the cathode uses activated carbon, the cathode and anode chambers (100mL) are filled with dilute acid solutions of different concentrations (0mol/L, 0.1mol/L and 0.5mol/L sulfuric acid), and the cathode and anode are connected by wires. After 30 days of treatment, the analysis found that the copper concentration gradually increased from iron to carbon, as shown in Figure 4. x/L is the distance between the test point and the iron electrode divided by the total length of the reactor.

Example 2: Cadmium is a typical heavy metal pollutant, which is extremely harmful to the environment. Take a certain amount of simulated cadmium-contaminated soil, the cadmium content is 160mg/kg, and the water content is 50%. Put it into the primary battery reaction device (Φ5cm×20cm), and connect the three primary battery devices in series as shown in Figure 2b. Iron filings are used for the anode, activated carbon is used for the cathode, and the cathode and anode chamber (100mL) is filled with 0.2mol/L hydrochloric acid solution, and the cathode and anode are connected by wires. After 30 days of treatment, the analysis found that the concentration of cadmium in the single reaction column gradually increased from iron to carbon, and the series connection of multiple galvanic reaction columns can expand the treatment area, as shown in Figure 5. x/L is the distance between the test point and the iron electrode divided by the total length of the reactor, C1, C2 and C3 represent the first, second and third primary cells in series, and C represents the situation of a single primary cell.

Claims (1)

1. the restorative procedure of a heavy-metal contaminated soil the steps include:

(1) on pending soil both sides electrode wells is set, the yin, yang electrode is installed in the electrode wells, the parallel placement of electrode, electrode spacing is 0.1-1m; When anode material adopted iron or aluminium, negative electrode adopted manganese dioxide, carbon or copper; When anode material adopted carbon, negative electrode adopted manganese dioxide;

(2) in above-mentioned electrode wells, fill flushing liquor, make the liquid level of electrode wells be higher than processing soil height, and the cathode and anode material is immersed in the flushing liquor; Flushing liquor is water or the concentration acid solution smaller or equal to 2mol/L, and acid is sulfuric acid, hydrochloric acid, nitric acid, oxalic acid, ethylenediamine tetra-acetic acid or citric acid;

(3) use lead to connect cathode and anode, conduction time is between 30-500 days.

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