The Extraction Characteristics of Metal-contaminated Soil by Soil Washing

토양세척기법을 이용한 중금속 오염토양 처리에서 중금속 추출특성

  • Hwang, Seon-Suk (Department of Environment Engineering, College of Engineering, Konkuk University) ;
  • Lee, Noh-Sup (Department of Environment Engineering, College of Engineering, Konkuk University) ;
  • NamKoong, Wan (Department of Environment Technology Center, Konkuk University)
  • 황선숙 (건국대학교 공과대학 환경공학과) ;
  • 이노섭 (건국대학교 공과대학 환경공학과) ;
  • 남궁완 (건국대학교 차세대환경기술센터)
  • Published : 2005.10.31

Abstract

The extraction characteristics of heavy metals(HM) from a contaminated soil at existing lead smelters were investigated with ethylene diamine tetraacetic acid(EDTA), citrate and HCl as washing solutions. EDTA was more effective for Pb than for other heavy metals. As the mol ratio of EDTA/HM increased, the removal efficiency of heavy metals became higher. When the mol ratio of EDTA/HM approached to 6.5, it removed Pb most effectively. Citrate was effective especially in extracting Zn. The removal efficiency of HCl was comparatively high in almost all heavy metals, and at 0.3N concentration it was the highest. After soil washing process by the use of EDTA, the great part of exchangeable fractions and most of heavy metals of weakly adsorbed like carbonate fraction were extracted. For washing with citrate and HCl, four heavy metals showed the similar exchange of chemical partitioning and the exchangeable fractions of Pb which has weakly adsorbed to soil were more increased than before the process. As removal efficiency of citrate washing process depends upon the distribution of non-detrital fractions, so it can be contended that only the amount of non-detrital fractions could be removed from all the heavy metal content. EDTA and HCl could remove most of non-residual fractions in all heavy metals except Zn. As a result of EDTA washing, toxicity characteristic leaching procedure(TCLP) concentration of the processed soil met the USEPA Pb limit of 5.0 mg/L.

과거 납제련소 부지의 중금속으로 오염된 토양을 EDTA, citrate, HCl의 세가지 용매를 이용하여 토양세척법으로 처리한 경우 중금속의 추출특성에 대하여 중금속의 추출율과 화학적 결합형태별 변화를 중심으로 살펴보았다. EDTA를 이용한 토양세척실험에서 중금속의 추출은 Pb에 특히 효과적이었다. EDTA/HM의 물비가 증가할수록 Pb의 제거율도 증가하였고 EDTA/HM의 몰비 6.5에서 효율적인 제거가 가능하였다. Citrate를 이용한 토양세척실험에서 중금속의 추출은 다른 중금속들 보다 Zn의 추출에 효과적이었다. HCl은 모든 중금속에 대하여 전반적으로 높은 추출율을 나타내었으며 0.3N 농도에서 가장 효율적인 추출이 가능하였다. EDTA로 토양세척법 처리 전후 중금속의 결합형태별 변화는 교환성과 탄산염 형태와 같이 결합력이 약한 형태로 존재하는 중금속이 대부분 추출되었다. Citrate와 HCl 처리 후 중금속의 결합형태별 변화는 네가지 중금속 모두 유사한 경향을 보였으며 Pb은 처리 전보다 처리 후에 교환가능성 형태가 증가하는 현상이 관찰되었다. Citrate 처리시 중금속 추출효율은 비결정성 형태의 함량과 거의 일치하는 결과를 나타내었다. EDTA와 HCl을 이용한 경우는 중금속 추출효율과 중금속의 결합형태의 비교결과 Zn을 제외한 나머지 중금속의 경우 비잔류성 형태의 대부분을 제거할 수 있었다. 처리 후 토양의 TCLP 결과는 EDTA로 처리한 경우에 Pb의 USEPA 기준인 5 mg/L를 만족시켰다.

Keywords

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