Abstract:

Based on the chlorinated organic compounds pollution existed in underground water of China, Zero-Valent-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 K_20nm>K_100nm>K_10μm>K_100μm. 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

摘要：

针对目前我国地下水中卤代烃污染问题, 采用零价铁技术, 应用不同粒径的零价铁, 对4种具代表性的卤代烃(四氯乙烯、三氯乙烯、四氯化碳和三氯甲烷)的降解动力学进行对比研究。结果表明, 在投加过量铁粉、卤代烃浓度为400 μg/L的条件下, 4种卤代烃的降解速率均与零价铁颗粒的粒径大小负相关。4种卤代烃的降解均符合伪一级动力学反应, 按照颗粒零价铁粒径大小, 伪一级反应速率常数从大到小依次为K_20nm>K_100nm>K_10μm>K_100μm。对比同种零价铁、不同卤代烃之间的降解速率, 得出的结论为K_烷烃>K_烯烃, K_四氯>K_三氯, 即氯代程度高的烷烃被零价铁降解的速率最高。基于体系中的pH, DO以及氯离子浓度变化趋势, 卤代烃降解过程中pH升高, DO的消耗与卤代烃降解同步并存在竞争关系。研究表明, 零价铁技术能有效地去除水中卤代烃, 可作为饮用水处理中前端处理工艺, 通过脱氯来降低卤代烃的毒性及分子量, 利于后续的工艺处理。

关键词: 零价铁, 粒径, 卤代烃, 动力学