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Reduction Efficiency of Cr(VI) in Aqueous Solution by Different Sources of Zero-Valent Irons

수용액 중 영가 철(Zero-Valent Iron)의 특성에 따른 Cr(VI)의 환원 효율 비교

  • Yang, Jae-E. (Division of Biological Environment, Kangwon National University) ;
  • Kim, Jong-Sung (School of Natural Resources, University of Nebraska) ;
  • Ok, Yong-Sik (Division of Biological Environment, Kangwon National University) ;
  • Yoo, Kyung-Yoal (Division of Biological Environment, Kangwon National University)
  • Published : 2005.09.30

Abstract

Objective of this research was to assess the effectiveness of the different sources of the zero-valent irons (ZVIs) on the reduction of the toxic Cr(VI) to the nonhazardous Cr(III) in an aqueous solution. The physical and chemical properties of the six ZVIs were determined. Particle size and specific surface area of the ZVIs were in the ranges of $85.55{\sim}196.46{\mu}m\;and\;0.055{\sim}0.091m^2/g$, respectively. Most of the ZVIs contained Fe greater than 98% except for J (93%) and PU (88%). Reduction efficiencies of the ZVI for Cr(VI) reduction were varied with kinds of ZVIs. The J and PU ZVIs reduced 100% and 98% of Cr(VI) in the aqueous solution, respectively, within 3 hrs of reaction. However, PA, F, Sand J1 reduced 74, 65, 29 and 11% of Cr(VI), respectively, after 48 hrs. The pH of the reacting solution was rapidly increased from 3 to $4.34{\sim}9.04$ within 3 hrs. The oxidation-reduction potential (Eh) of the reacting solution was dropped from 600 to 319 mV within 3 hrs following addition of ZVIs to the Cr(VI) contaminated water. The capability of ZVIs for Cr(VI) reduction was the orders of PU > J > PA > F > S > J1, which coincided with the capacities to increase the pH and decrease the redox potentials. Results suggested that the reduction of Cr(VI) to Cr(III) was derived from the oxidation of the ZVI in the aqueous solution.

실험에 사용된 영가 철의 평균 입도는 $85.55{\sim}196.46{\mu}m$의 범위를 나타내었고 비표면적은 $0.055{\sim}0.091m^2/g$으로 나타났다. 영가 철 중 J(93%) 및 PU(88%)를 제외한 PA, F, S, J1는 철을 98% 이상 함유하는 것으로 평가되었다. 영가 철에 의한 Cr(VI)의 환원은 영가 철의 종류에 따라 달랐으며, J 및 PU의 경우 3시간 이내에 98% 이상의 Cr(VI)을 제거하였다. 그러나 PA, F, S, J1의 경우 반응 48시간 동안 각각 74, 65, 29, 11%의 Cr(VI) 만을 제거하였으며 이때 환원 효율은 J > PU > PA > F > S > J1 순으로 나타났다. 영가철에 의한Cr(VI)의 환원 과정에서 용액의 pH는 반응초기 3시간 동안 급격히 증가하였으며 이후 안정화되는 경향을 나타내었다. 영가 철의 종류에 따른 pH의 변화는 PU > J > PA > F > S > J1 순으로 나타났으며 Cr(VI)의 환원효율이 큰 영가 철에서 pH의 상승 폭도 크게 나타나는 것으로 평가되었다. 영가 철의 종류에 따른 산화환원전위 Eh의 변화는 pH와는 반대의 경향을 나타내었으며 Cr(VI)의 환원율이 클수록 Eh의 감소율은 증가하였다. 유기화합물의 경우 반응효율이 영가 철의 물리적 특성에 의해 주로 지배되는 것으로 알려져 있으나 Cr(VI)의 경우 화학적 특성이 반응효율을 지배하는 것으로 판단되었다. 본 실험에 사용된 6종류의 상용 영가 철 중에는 J와 PU가 Cr(VI)의 환원에 가장 효과적인 것으로 조사되었다.

Keywords

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