Journal of Korean Society of Environmental Engineers (대한환경공학회지)

Korean Society of Environmental Engineers (대한환경공학회)
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The Effect of Fumed Silica on Nitrate Reduction by Zero-valent Iron

흄드 실리카가 영가철에 의한 질산성질소 환원에 미치는 영향

  • Received : 2010.01.14
  • Accepted : 2010.06.04
  • Published : 2010.06.30
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Abstract

The effect of silica(fumed) on nitrate reduction by zero-valent iron(ZVI) was studied using batch experiment. The reduction of nitrate was tested in three different aqueous media including de-ionized water, artificial groundwater and real groundwater contaminated by nitrate. Kinetics of nitrate reduction in groundwater were faster than those in de-ionized water, and first-order rate constant($k_{obs}$) of ZVI/silica(fumed) process was about 2.5 time greater than that of ZVI process in groundwater. Amendment of Silica(fumed) also decreased ammonium presumably through adsorption on silica surface. The pHs in all processes increased due to oxidation of ZVI, but the increase was lower in groundwater due to buffering capacity of groundwater. The result also showed amount of reduced nitrate increased as initial nitrate concentration increased in groundwater. Separate adsorption isotherm experiments indicated that fumed silica itself had some degree of adsorption capacity for ammonium. The overall results indicated that silica(fumed) might be a promising material for enhancing nitrate reduction by ZVI.

다양한 반응조에서 흄드 실리카(silica(fumed))가 질산성질소 처리를 위한 영가철 공정에 미치는 영향을 알아보기 위한 회분실험(batch experiment)을 수행하였다. 반응조는 질산성질소만 주입한 경우, 질산성질소와 지하수 환경에 존재하는 이온들을 주입한 경우, 실제 질산성질소로 오염된 지하수로 구성하였다. 지하수 환경을 가진 반응조에서 질산성질소 환원 속도가 빠르게 진행되었으며, 영가철/흄드 실리카 공정이 영가철 단독 공정에 비해 약 2.5 배의 반응 상수값($k_{obs}$)을 나타냈다. 전반적으로 주요 부산물인 암모늄은 영가철 단독 공정에서 약 70% 환원율로 발생하였으며, 영가철/흄드 실리카 공정의 경우에는 암모늄 발생율이 저감되었다. 수중 pH 는 영가철이 산화되면서 pH 가 상승하였으며, 지하수 환경에서는 상대적으로 낮게 유지되었다. 모든 반응조에서 영가철/흄드 실리카 공정의 pH 가 낮게 유지되었으며, 지하수 환경에서 질산성질소가 고농도로 존재할 경우에는 저농도에 비해 pH 상승폭이 큰 것으로 나타났다. 또한 등온흡착실험을 수행한 결과, 흄드 실리카가 암모늄에 대한 흡착능을 보였다. 전반적인 결과들을 통해 흄드 실리카가 질산성질소를 처리하는 영가철 공정에 유용한 매질임을 확인하였다.

Keywords

References

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