Particle Surface Hydrophobicity and the Dechlorination of Chloro-Compounds by Iron Sulfides |
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Authors: | Sang-Won Park Sung-Kuk Kim Jeong-Bae Kim Sung-Woo Choi Hilary I Inyang Shuzo Tokunaga |
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Institution: | (1) Department of Environmental Science and Engineering, Keimyung University, Daegu, 704-701, Korea;(2) Global Institute for Energy and Environmental Systems, University of North Carolina at Charlotte, 9201 University City Blvd, Charlotte, NC 28223, USA;(3) National Institute of Advanced Industrial Science and Technology, Central 5, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan |
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Abstract: | Halogenated aliphatic compounds (HACs) can be reduced by iron sulfides in aqueous systems. Generally, the thermodynamics and
kinetics of dehalogenation reactions are controlled by the mineralogical and particle surface characteristics of the iron
sulfide, the composition of the HAC and reaction conditions such as component concentrations, pH and Eh. In this theoretical
and experimental investigation of CCl4 and C2Cl6 reduction by FeS and FeS2, the roles of hydrophobic and hydrophilic sites on the iron sulfides were analyzed. Experimental data obtained through zeta
potential measurements, were used along with the Gouy-Chapman model and the simple two-layer surface complexation model to
relate iron sulfide surface hydroxyl densities to the degree of HAC dehalogenation. The surface hydroxyl site densities of
FeS and FeS2 were found to be 0.11 sites/nm2 and 0.21 sites/nm2, respectively. During the dehalogenation reaction process, CCl4 was found to decrease to its first intermediate product CHCl3 within the first 20 hours followed by a slower process of conversion to CH2Cl2. The results also show that FeS is less hydrated (more hydrophobic) than FeS2. For CCl4 and C2Cl6, FeS is a better dehalogenator than FeS2. These results imply that particle surface hydrophobicity is a critical factor in surface-mediated dehalogenation of chlorinated
compounds. |
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Keywords: | HACs hydrophilic/hydrophobic sites reductive dehalogenation |
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