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Study on Extraction Remediation Technologies of Arsenic Contaminated Soils

Author: TangMin
Tutor: ZhangHuanZuo
School: Chinese Geology University (Beijing)
Course: Environmental Science and Engineering
Keywords: Soil Arsenic Extraction Citric acid Sodium hydroxide
CLC: X53
Type: Master's thesis
Year: 2011
Downloads: 183
Quote: 1
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Abstract


Arsenic is widely distributed in nature 's elements and their compounds are widely used in the production of alloys , dyes , pesticides , preservatives . Associated with arsenic industrial development , arsenic chemicals caused serious environmental pollution accident also occurred . General arsenic contamination events , the soil is the most direct victims , it is necessary to find a quick and effective way to control the repair of arsenic contaminated soil . Artificially mixed arsenic-contaminated soil samples ( powder clay ) and soil samples (sand ) as the object of study, through screening extractant , to optimize the extraction conditions , the extraction soil leaching after the toxicity detection as well as before and after extraction of arsenic in soil morphological analysis and other tests , and strive to provide the basis for governance of the soil arsenic contamination . The experiment draw the following conclusions : ( 1 ) liquid soil than the concentration of the extractant , the extraction time and the extraction rate was positively correlated . With the increase of the ratio of liquid soil , increasing the concentration of extractant and extraction time , contamination rate of arsenic in soil extracts . (2) extracts arsenic contamination powder clay , the best solution of citric soil ratio 20mL / g, the extractant concentration of 0.25mol / L , the extraction time was 21h, the highest extraction rate 85.51 % ; of NaOH solution soil than 30 mL / g , the extractant concentration of 0.75mol / L, extraction time was 24 h , up to the highest extraction rate of 78.85% . (3) citrate best solution in the extraction of arsenic-contaminated sand , soil ratio of 25ml / g, and the concentration of the extractant was 0.1mol / L, the extraction time was 21h , up to the highest extraction rate of 97.36% ; of NaOH The liquid soil than 40mL / extractant concentration to 0.02 mol / L , the extraction time of 24 h , up to a maximum extraction rate of 81.36% . (4) co-exist in the soil PO43- , Zn2 , Fe2 ions , due to its competitive role , so reduce the effect of arsenic extraction . (5 ) , citric acid or NaOH extracted arsenic contaminated soil leaching toxicity detection experiment , the results show that the extracted soil can reach hazardous waste leaching toxic identification standard is no longer hazardous waste . (6 ) the effect of citric acid and NaOH extraction of arsenic-contaminated sand was significantly better than the effect of the powder clay extraction . (7), citric acid and NaOH are able to significantly remove the tested soil samples bioavailable arsenic , and most of the potential use of arsenic , to reduce the bioavailability of arsenic in the soil .

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CLC: > Environmental science, safety science > Environmental pollution and its prevention > Soil Contamination and Control
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