Environment-friendly chemical leaching method for Cd-polluted soil

Abstract

The invention belongs to the field of soil remediation, and provides an environment-friendly Cd-polluted soil chemical leaching method which comprises the following steps: determining the optimal concentration and the optimal pH of GLDA for removing Cd in soil through oscillation extraction, leaching the Cd-polluted soil through a GLDA solution column with the concentration and the pH determined through oscillation extraction, in order to reduce the risk that after leaching, residual GLDA in the soil activates heavy metal again, washing the soil leached by the GLDA by using water, analyzing the residual condition of the GLDA by determining soluble organic carbon, and determining the content of Cd by using an atomic absorption spectrophotometer. According to the method, a biodegradable chelating agent is used, water is used for washing after column leaching, high Cd removal efficiency is kept, meanwhile, residual chelating agent in the soil is reduced, the influence on the ecological environment of the soil is reduced, and a reference is provided for GLDA in-situ chemical leaching remediation of the Cd-polluted soil.

Description

technical field [0001] The invention relates to an environment-friendly restoration technology for rinsing Cd-contaminated soil with a biodegradable chelating agent GLDA column, which can maintain a high removal rate and reduce the residue of the chelating agent in soil, and belongs to the field of soil restoration. Background technique [0002] The "National Soil Pollution Survey Bulletin" released in 2014 shows that the total soil exceeding the standard rate in the country is 16.1%. Pollution exceeded the highest rate reached 7.0%. Heavy metals are concealed, persistent, and non-degradable in the soil, and cannot be repaired through soil self-purification, but only transformed between various forms. Heavy metal pollution affects soil physical and chemical properties and ecological structure functions, destroys microbial community structure, and may endanger human health through food chain enrichment. The "Soil Pollution Prevention and Control Action Plan" released in 201...

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Problems solved by technology

Inorganic acids / salts and other inorganic solutions have the advantages of good effect, fast speed, and low cost, but inorganic acids / salts damage the soil structure, increase the risk of soil salinization, and corrode leaching equipment, etc., which limit their practical engineering

EDTA can extract potentially toxic metals from all non-silicate bonded phases in soil, and is considered to be one of the most effective chelating agents for removing heavy metals from soil, but EDTA is not easy to degrade, the literature "Soil Biology and Biochemistry, 2009, 41 (10): 2214-2221." Reported that EDTA only decomposed 14% within 20 days, which can cause secondary pollution by leaching to groundwater, and even with low doses of EDTA, the growth of plants and soil rhizosphere microorganisms suppressed

Citric acid is a natural organic acid. Compared with EDTA, it has better biodegradability, but the chelating ability of citric acid is weak at low concentration, and the removal effect of Pb, Cd and Cu in polluted soil is not good.

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