Stabilization of As Contaminated Soils using a Combination of Hydrated Lime, Portland Cement, FeCl3·6H2O and NaOH

The purpose of this study was to investigate the effectiveness of a stabilization treatment for As contaminated soil. A combination of hydrated lime, Portland cement, $FeCl_3{\cdot}6H_2O$, and NaOH were used as stabilizing agents. The effectiveness of stabilization treatment was evaluated by the Korean Standard Test (KST) method (1N HCl extraction). Sequential extractions were performed to investigate the As distribution after treatment. Following the application of the treatment, curing periods of up to 7 and 28days were investigated. The experimental results showed that a combination of hydrated lime/Portland cement was more effective than treatments of hydrated lime or Portland cement at immobilizing As in the contaminated soil. The treatment of 25wt% hydrated lime and 5wt% Portland cement was effective in reducing As leachability less than the Korean warning standard of 20 mg/kg. However, the treatments of hydrated lime and Portland cement failed to meet the Korean warning standard even when up to 30 wt% was used. The treatment utilizing hydrated lime and $FeCl_3{\cdot}6H_2O$ was not effective in properly reducing As leachability. The addition of $FeCl_3{\cdot}6H_2O$ was negative in terms of pH condition. Moreover, the treatment with hydrated lime/NaOH was effective in reducing As leachability but not as much as hydrated lime/Portland cement. The sequential extraction results indicated that the residual phase was greatly increased upon the treatment of hydrated lime/Portland cement. It was concluded that the hydrated lime/Portland cement treatment was the best among the other combinations studied at achieving trace As concentrations.

소석회, 포틀랜드 시멘트, FeCl3·6H2O, NaOH를 이용한 비소 오염토양의 안정화

본 연구에서 비소로 오염된 토양에 함유된 비소를 안정화시키기 위하여 4종류의 안정화제를 이용 처리하여 다음과 같은 결론을 얻었다. 안정화 처리에 사용된 오염토는 약알칼리성을 띄고 있으며, 입도분포 결과 사토계열이였고 57.5%의 비소가 무정형 및 비결정형 철/알루미늄 수산화물형태로 존재했다. 안정화 실험 결과 소석회/포틀랜드시멘트 혼합 안정화처리가 모든 안정화 처리와 비교 했을 때 현저한 우의를 보였으며 총 함량 30%로 토양오염 우려기준 20 mg/kg('나'지역)을 통과 하였다. 소석회/$FeCl_3{\cdot}6H_2O$ 혼합 이용시 효율적인 비소 저감효과룹 기대할 수 없었으며 소석회/NaOH는 효과적이었으나 소석회/포틀랜드시멘트 보다는 효율성이 제한적 이였다. 소석회/포틀랜드시멘트 혼합 안정화 처리 후 연속추출결과는 처리 전 오염토와 비교했을 때 특이적 흡착과 잔류대의 증가를 보였다. 특히 25wt%+10wt% 처리 시료에서 잔류태의 증가는 2배가 넘어 (16%에서 35.7%) 매우 안정적인 비소 존재 형태를 보여 비소 용출농도 저감에 현저하게 기여한 것으로 판단된다.