중금속 오염토양 구연산 침출시 과산화수소의 영향

Abstract

The remediation of soil contaminated with heavy metal such as solidification/stabilization has been conducted to prevent migrating heavy metals. Korea soil cleanup standard was revised in 2009, and aqua regia is being used for leaching of heavy metal instead of 0.1N hydrochloric acid. The removal method of heavy metal from contaminated site such as soil washing is a better option than preventing heavy metal migration such as solidification/stabilization. Physical treatment has been found to be also effective and economical remediation method, but it is not available for fine particle size with under 75µm. The fine size of particle has large specific area so the removal efficiency by soil washing method could be expected to be better than coarse grain.

This study is aimed to investigate the removal of heavy metals from contaminated soil using soil washing. Three kinds of samples were collected from different contaminated soil area. These sites have been contaminated with heavy metals such as lead, copper and zinc. Firstly, sequential extraction method was conducted to determine chemical or mineralogical forms of heavy metals, and then citrate leaching efficiency was examined along with initial pH. In case of site A and B the summation of amounts bound to exchangeable, carbonate and Fe-Mn oxide metal faction over 90%, and high leaching efficiency was observed above 85% in both site A and B, whereas site C shows low leaching efficiency with 40%, because site C 70% of contaminated metals existed as sulphide and residual metal fraction. The result suggests that leaching efficiency could be increased by dissolution of sulphide and residual fraction. Therefore, further leaching tests were performed in citrate solution with hydrogen peroxide addition. While leaching efficiency of lead in site B has been increased 98% by adding 0.013mol hydrogen peroxide, in site C zinc leaching efficiency showed 70% even with 0.13mol hydrogen peroxide addition.