Journal of Korean Society of Environmental Engineers (대한환경공학회지)

Korean Society of Environmental Engineers (대한환경공학회)
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The Effects of Reaction Conditions and NOM on Persulfate Oxidation of RDX

Persulfate에 의한 RDX 산화시 반응조건과 NOM의 영향

  • Wu, Dabo (Environmental Business Division, H-Plus Eco Ltd.) ;
  • Bae, Bum-Han (Department of Civil & Environmental Engineering, Kyungwon University)
  • 무대박 (에이치플러스에코 환경사업부문) ;
  • 배범한 (경원대학교 토목환경공학과)
  • Received : 2011.06.23
  • Accepted : 2011.10.26
  • Published : 2011.10.31
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Abstract

In this experiment, persulfate, a strong oxidant for ISCO (In-Situ Chemical Oxidation) was used to degraded RDX in artificial ground water at ambient temperature. Results of RDX degradation by persulfate in a batch reactor showed that the oxidation reaction was pseudo first order with estimated Ea (activation energy) of $1.14{\times}10^2kJ/mol$ and the rate was increased with the increase of reaction temperature. The oxidation of RDX by persulfate increased slightly with the increase of initial solution pH from 4 to 8. The RDX oxidation rate increased 13 times at pH 10 compared with that at pH 4, however, alkaline hydrolysis was found to be the main reaction of RDX degradation rather than oxidation. The study also showed that the oxidation rate of RDX by persulfate was linearly dependent upon the molar ratios of persulfate to RDX from 5 : 1 up to 100 : 1, with a proportion constant of $4{\times}10^{-4}$ ($min^{-1}$/molar ratio) at $70^{\circ}C$. While NOM (Natural Organic Matter) exerted negative effects on the oxidation rate of RDX by persulfate, with a proportion constant of $1.21{\times}10^{-4}$ ($min^{-1}{\cdot}L/mg-NOM$) at $70^{\circ}C$ and persulfate/NOM molar ratio of 10/1. The decrease in RDX oxidation rate was linearly dependent upon the added NOM concentration. However, the estimated activation energy in the presence of 20 mg-NOM/L was within 3.3% error compared to that without NOM, which implies the addition of NOM does not alter intrinsic oxidation reaction.

본 연구는 토양이나 지하수 원위치 화학적 산화법(In-Situ Chemical Oxidation, ISCO)에서 사용할 수 있는 산화제 Persulfate를 상온에서 활용할 수 있도록 RDX를 처리대상물질로 연구하였다. Persulfate로 RDX를 처리한 결과, 반응은 유사1차반응으로 나타났으며 온도가 증가함에 따라 분해속도도 증가하였고, 이 때 활성화에너지(Activation energy)는 $1.14{\times}10^2kJ/mol$으로 산정되었다. Persulfate에 의한 RDX의 분해반응속도는 pH에 비례하여 증가하였으며, pH값이 4, 6, 8일 때 반응속도의 변화가 크지 않았다. 그러나 pH 10에서는 13배 이상 증가하였는데, persulfate에 의한 산화가 아니라 alkaline hydrolysis로 나타났다. Persulfate에 의한 RDX의 분해반응속도는 persulfate/RDX의 몰 비율에 따라 선형적으로 증가하였으며, $70^{\circ}C$에서 측정한 비례상수는 $4{\times}10^{-4}$ ($min^{-1}$/몰 비율)이었다. 용액 내 천연유기물(NOM) 농도가 증가함에 따라 persulfate에 의한 RDX 분해속도 선형 감소하였으며 $70^{\circ}C$, persulfate/RDX 몰비 10/1에서 측정한 비례상수는 $1.21{\times}10^{-4}$ ($min^{-1}{\cdot}L/mg-NOM$)이었다. 반응속도의 감소는 NOM 첨가량에 선형적으로 비례하였다. NOM 20 mg/L을 첨가한 반응의 Ea값은, 무첨가 반응에서 산정된 Ea값과 3.3% 오차에 불과하였는데, 이는 NOM의 첨가가 본래의 산화반응을 변화시키지는 않음을 의미한다.

Keywords

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