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A method of low-temperature thermal desorption combined with chemical leaching to remediate mercury-contaminated soil

A technology of chemical leaching and mercury pollution, applied in the restoration of polluted soil, etc., can solve the problems of low efficiency of leaching and restoration, high energy consumption of heat treatment, and small soil damage, so as to reduce soil structure damage and improve leaching. Efficiency, effective treatment effect

Active Publication Date: 2020-09-08
AEROSPACE KAITIAN ENVIRONMENTAL TECH CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] Aiming at the defects in the heat treatment and leaching repair methods of mercury-contaminated soil in the prior art, the purpose of the present invention is to provide a combination of thermal decomposition technology and medicament leaching technology to realize multiple valence in mercury-contaminated soil. It is a method for remediating mercury-contaminated soil with high efficiency, low mercury residue, less damage to soil, and low cost. After remediation, the removal rate of mercury in soil can reach more than 95%, which solves the problem of heat treatment of general mercury-contaminated soil. The problem of high consumption and low efficiency of rinsing and repairing

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] Take the soil from the mercury contaminated site left by the relocation of a chemical plant in Hunan. The average mercury content in the soil is 120mg / kg. The soil is dried and crushed for use. Prepare each eluent separately. The mixed solution containing organic acid, iodide salt and chloride salt contains citric acid concentration of 1moL / L, potassium iodide concentration of 0.1moL / L, calcium chloride concentration of 0.3moL / L, and sulfide salt The mass percentage concentration of sodium sulfide in the sodium hydroxide solution is 5%, and the amount of sodium hydroxide added is 1.5% of the amount of sodium sulfide. Weigh 500g of the pretreated soil and put it into a heat treatment device for heat treatment, set a treatment temperature of 350°C, and a treatment time of 30 minutes. The heat-treated soil is unearthed from the discharge port, the mercury in the tail gas is condensed and recovered, and then the residual mercury is removed by activated carbon adsorption. Aft...

Embodiment 2

[0052] Take the same soil as in Example 1, and undergo the same air-drying and crushing treatments, and configure the same leaching solutions as in Example 1. Weigh 500g of the pretreated soil and put it into a heat treatment device, and heat treatment under the conditions of a treatment temperature of 350°C and a treatment time of 20, 30, and 40 minutes. The heat-treated soil was cooled to room temperature and subjected to the same leaching treatment as in Example 1. After air-drying, the soil mercury content was determined to be 2.13mg / kg, 1.15mg / kg, 1.01mg / kg, and the removal rates of mercury in the soil were respectively It is 98.23%, 99.04%, 99.16%. When the treatment time was 30 and 40 minutes, the mercury content in the soil was lower than the third-level standard value (1.5mg / kg) of "Soil Environmental Quality Standard" (GB15618-1995).

Embodiment 3

[0054] Take the same soil as in Example 1, and undergo the same air-drying and crushing treatments, and configure the same leaching solutions as in Example 1. Weigh 500g of the pretreated soil and put it into the heat treatment device, and heat treatment under the conditions of setting treatment time of 30 minutes and treatment temperature of 250, 300, and 350°C. The heat-treated soil was cooled to room temperature and subjected to the same leaching treatment as in Example 1. After air-drying, the soil mercury content was determined to be 1.96mg / kg, 1.05mg / kg, 0.94mg / kg, and the removal rates of mercury in the soil were respectively It is 98.37%, 99.13%, 99.27%. The mercury content in the soil was lower than the third-level standard value (1.5mg / kg) of "Soil Environmental Quality Standard" (GB15618-1995) when the treatment temperature was 300 and 350 ℃ respectively.

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Abstract

The invention discloses a method for repairing polluted soil through low-temperature thermal desorption with chemical drip washing. The method comprises the following steps: firstly, performing low-temperature thermal desorption treatment on mercury polluted soil so as to remove metal mercury, organic combined mercury and a part of inorganic combined mercury with a low melting point in the soil; secondly, performing drip washing with a mixed liquid containing organic acids, iodate and chlorine salts so as to remove mercuric oxide with a high melting point; and finally performing drip washing on mercuric sulfide with a high melting point with a mixed liquid of sodium sulfide and sodium hydroxide. By adopting the method, efficient removal of mercury of multiple valence states in mercury polluted soil can be achieved, a small amount of mercury is retained, the removal rate of mercury is up to 95% or greater, secondary pollution to the environment is avoided, and the cost is low.

Description

Technical field [0001] The invention relates to a method for repairing mercury contaminated soil, in particular to a method for repairing mercury contaminated soil through low-temperature thermal desorption combined with leaching, and belongs to the technical field of heavy metal soil treatment. Background technique [0002] In recent years, with the rapid development of industry and agriculture, a large amount of mercury has been released during production and use, which has made the soil more and more polluted by mercury. The main sources of soil mercury pollution are atmospheric deposition, sewage irrigation, industrial pollution sources (coal burning, chlor-alkali industry, battery plants, smelting, papermaking and other industries), agricultural pollution sources (the use of pesticides and chemical fertilizers), and mercury-containing wastes (thermometers, waste Battery, etc.) Improper handling, etc. The mercury and its compounds in the soil can enter the human body through...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B09C1/02B09C1/06B09C1/08
CPCB09C1/02B09C1/06B09C1/08
Inventor 邵乐史学峰韩凤刘晓月
Owner AEROSPACE KAITIAN ENVIRONMENTAL TECH CO LTD
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