공기접촉 제어를 통한 산화방지 Core-Shell 나노영가철의 제조 = Synthesis of Oxidation Resistant Core-shell Nanoscale Zero-valent Iron by Controlled Air Contact

다국어 초록 (Multilingual Abstract)

Experimental studies were conducted to characterize the synthesized nanoscale zero-valent iron (NZVI) which is resistant to oxidation in the atmospheric environment. XRD, XPS, and TEM analyses revealed that the oxidation-resistant NZVI particles formed under various controlled air contact conditions (4, 8 and 12 mL/min) have shells with ~5nm thickness. The shells consist of magnetite (Fe3O4) and maghemite (g-Fe2O3), predominantly. No substantial differences were found in the shell components and thickness among NZVI particles formed under the various air flow rates. On the other hand, shell was not detected in the TEM image of rapidly oxidized NZVI particles. NZVI particles synthesized under the various air flow rates showed similar TCE degradation performances (kobs=0.111, 0.102, and 0.086 hr-1), which are equivalent to approximately 80% of those obtained by the fresh NZVI particles. TCE degradation efficiencies of the NZVI particles(fresh, controlled air contact and rapidly oxidized) were improved after equilibrating with water for one day, indicating that depassivation of the shells occurred. The performances of NZVI particles decreased to 90% and 50% of those of the fresh NZVI particles, when they were equilibrated with the atmosphere for a week and two months, respectively. The NZVI particles synthesized under the controlled air contact would have advantages over traditional NZVI particles in terms of practical application into the site, because of their inertness toward atmospheric oxygen.

국문 초록 (Abstract)

본 연구는 대기중에서 안정한 나노크기 영가철을 제조한 후 그 특성을 평가하기 위해 수행되었다. XRD, XPS 분석 을 통해 인위적으로 4, 8, 12 mL/min 유량의 공기 접촉을 통해 형성된 shell의 두께는 5 nm로 모두 유사한 것으로 확인되었고, shell의 성분은 magnetite(Fe3O4), maghemite(g-Fe2O3)가 주성분임을 확인할 수 있었다. 4, 8, 12 mL/ min의 접촉 공기 유량에 따른 shell의 명확한 성분 및 두께 변화는 확인할 수 없었다. 반면 대기 중에서 공기와 급 속으로 접촉시킨 나노크기 영가철의 경우는 TEM 분석 결과 shell 층이 확인되지 않았다. 4, 8, 12 mL/min의 유량 으로 공기 접촉된 나노크기 영가철의 TCE 분해능(kobs=0.111, 0.102, and 0.086 hr-1) 또한 큰 차이를 보이지 않았 으며, fresh한 나노크기 영가철에 비해서는 약 80%의 분해효율을 나타내었다. Fresh한 나노크기 영가철 및 4 mL/ min과 급속으로 공기 접촉시킨 나노크기 영가철을 물속에서 1일 동안 물과 접촉시킨 후 분해능을 평가한 실험에서 는 공기 접촉 후 바로 분해 실험한 것 보다 분해능이 모두 향상되었다. 이는 물과의 반응을 통해 shell 층이 벗겨져 순수한 Fe(0)와 TCE의 접촉이 빨라져서 일어난 결과로 판단되어진다. 또한 각각 1주일과 2달간 대기 중에서 방치한 후 분해 실험한 결과 공기 접촉 후 바로 분해 실험한 결과와 비교해서 분해능이 90%와 50%로 감소하였다. 따라서 본 연구결과 일정 유량으로 공기 접촉 시킨 나노크기 영가철은 대기 중 산소에 안정하기 때문에 실제 현장 적용에 유리할 것으로 판단된다.

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