Method for repairing polluted soil through low-temperature thermal desorption with chemical drip washing
A technology of chemical leaching and mercury pollution, which is applied in the restoration of polluted soil, etc., can solve the problems of low efficiency of leaching and repair, high energy consumption of heat treatment, and small soil damage, so as to reduce soil structure damage and improve leaching. Efficiency, effective treatment effect
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Embodiment 1
[0044] The mercury-contaminated soil left over from the relocation of a chemical factory in Hunan was taken. The average mercury content in the soil was 120 mg / kg. The soil was air-dried and crushed for later use. Configure each eluent separately, in which the concentration of citric acid in the mixed solution containing organic acid, iodine salt and chloride salt is 1moL / L, the concentration of potassium iodide is 0.1moL / L, the concentration of calcium chloride is 0.3moL / L, and the concentration of sulfide salt is And the sodium sulfide mass percent concentration in the sodium hydroxide solution is 5%, and the add-on of sodium hydroxide is 1.5% of the sodium sulfide consumption. Weigh 500 g of the pretreated soil and put it into a heat treatment device for heat treatment, set the treatment temperature to 350° C., and the treatment time to 30 minutes. The heat-treated soil is unearthed from the discharge port, the mercury in the tail gas is condensed and recovered, and then th...
Embodiment 2
[0052] Take the same soil as in Example 1, and after the same air-drying and crushing treatment, configure the same eluents as in Example 1 respectively. Weigh 500 g of the pretreated soil and put it into a heat treatment device, and heat treatment is performed under the conditions that the treatment temperature is set at 350° C. and the treatment time is 20, 30, and 40 minutes, respectively. After the heat-treated soil was cooled to normal temperature, the same leaching treatment as in Example 1 was carried out. After air-drying, the soil mercury content was measured to be 2.13mg / kg, 1.15mg / kg, and 1.01mg / kg respectively. The removal rates of mercury in the soil were respectively 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 grade standard value (1.5mg / kg) of "Soil Environmental Quality Standard" (GB15618-1995).
Embodiment 3
[0054]Take the same soil as in Example 1, and after the same air-drying and crushing treatment, configure the same eluents as in Example 1 respectively. Weigh 500 g of the pretreated soil and put it into a heat treatment device, and heat treatment is performed under the conditions that the treatment time is set to 30 minutes and the treatment temperature is 250, 300, and 350° C. respectively. After the heat-treated soil was cooled to normal temperature, the same leaching treatment as in Example 1 was carried out. After the air-drying treatment, the mercury content in the soil was measured to be 1.96mg / kg, 1.05mg / kg, and 0.94mg / kg. The removal rates of mercury in the soil were respectively 98.37%, 99.13%, 99.22%. When the treatment temperature was 300 and 350℃, the mercury content in the soil was lower than the third grade standard value (1.5mg / kg) of "Soil Environmental Quality Standard" (GB15618-1995).
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