Reductive Removal of Four Halogenated Organic Compounds by Different Sizes of Zero-valent-iron

ZHAO Xufei1, WEI Caijie2,†, ZHANG Jin2, WU Weizhong1,†, WANG Xiaomao2, YANG Hongwei2, XIE Yuefeng2

1. College of Environmental Sciences and Engineering, Peking University, Beijing 100871; 2. School of Environment, Tsinghua University, Beijing 100084; † Corresponding authors, E-mail: cjwei@mail.tsinghua.edu.cn (WEI Caijie), wzwu@pku.edu.cn (WU Weizhong)

Abstract Based on the chlorinated organic compounds pollution existed in underground water of China, Zerovalent-iron (ZVI) technology is employed for the removal of four representative halogenated organic compounds (HOCS) (tetrachloroethylene, PCE; tricholoroethylene, TCE; tetrachlormethane, TCM; and chloroform, CT). The results indicated that the reduction rates of four target compounds, of which the initial concentration is 400 μg/l, negatively correlated with the size of Zero-valent-iron particles. The reduction kinetics of the targeted HOCS were all well fitted with the Pseudo-firstorder kinetics, and the ranking of obtained first order rate constants (K) among different particle sizes was K20nm>k100nm>k10μm>k100μm. Comparing K among four target HOCS, the reduction rates of chlorinated methane (CT, TCM) are higher than chlorinated ethylene (PCE, TCE), and highly chlorinated HOCS (PCE, CT) were degraded more easily than lower one (TCE, TCM). ph of aqueous solution all increased along the chlorinated compounds reduction which was raised by the reaction between ZVI and water. The oxygen in water consumed the ZVI particle either and competed with the surface adsorbed chlorinated compounds. In summary, Zero-valent-iron proved to be an efficient technology for typical HOCS removal, which can be considered as a promising process added in the beginning part of drinking water treatment plant. Key words zero-valent-iron (ZVI); particle size; halogenated organic compounds; kinetics