Study On The Elution Technology Of Heavy Metal Pb And Cr(VI) Contaminated Soil

With the continuous advancement of city construction in China,the environmental problems of large soil pollution caused by the relocation of enterprise legacy site has attracted much attention.Because of its wide range and serious harm,not only caused great impact on the surrounding residents personal and property safety,but also left serious environment security risks for future land using,and it has become an important factors of affecting and restricting the regional sustainable development.So the remediation of contaminated sites to accelerate its transformation and utilization is particularly urgent.Heavy metals Pb and Cr are the most common,toxic and difficult heavy metal among contaminated sites due to their wide use in industry.In this paper,we reviewed present situation of heavy metal contaminated soil and the main remediation technology.Washing and Reduction-solidification were used to remediate Pb and Cr⁶⁺ contaminated soil.First,choosing several typical washing reagents to wash the different Pb and Cr⁶⁺ pollution soil by two cleaning methods of mixing and swirl desorption.The results showed that:?1?Mixing cleaning,the best cleaning reagent for Pb contaminated soil is EDTA,and then citric acid and hydrochloric acid,there was no significant difference between several kinds of cleaning effect of cleaning reagent on Cr⁶⁺ contaminated soil.?2?The best cleaning conditions of EDTA,citric acid and HCl respectively in Pb contaminated soils were the concentration of 0.1,0.5,0.2,mol/L,30,30,10 min and solid-liquid ratio was 1:10,the highest removal rate of low,medium and high pollution soil were 99%,72%and 73%respectively.Because there were no significant difference between the cleaning reagents for Cr⁶⁺ contaminated soil,we selected water for five stage cleaning and the total removal rate was 59%.?3?Cyclone desorption,the removal rate of Pb have been strengthened,the removal rate increased by 16%,after two stage cyclone desorbed,the final Pb content met the standards.While the removal rate of Cr⁶⁺ did not significantly increase and the desorption equipment in the cyclone overflow mouth enrichment f:ne particles of Cr⁶⁺ contaminated soil.Washing experiments showed that cleaning can achieve restoration goals for the Pb contaminated soil,while Cr⁶⁺couldn't.Secondly,using the reducing reagent of sodium metabisulfite and curing reagent of cement to conduct experiments of the different pollution load of Cr⁶⁺ contaminated soil,results showed that:?1?Adding 4 times of the theoretical amount of reducing reagent and 10%cement,and then maintained for 10 days,the final soil Cr⁶⁺ content and leaching concentration met the standards.?2?On the basis of laboratory test results,the actual site reduction-solidification had remediated the contaminated soil.The results showed that the remediation of Cr⁶⁺ contaminated soil could achieve good effect by the combination of reduction and solidification technology.Meanwhile,the successful restoration of the actual site could provide reference for similar Cr⁶⁺contaminated soil remediation projects.