Coupled Transformation of Carbon Tetrachloride and Copper Ion by Nanocrystalline Ferric Oxides and Ferrous Ions

奈米鐵氧化物與亞鐵離子共分解四氯化碳與銅離子之研究

董瑞安(Ruey-An Doong) ； 梅若恩(R. A. Maithreepala) ； 張淑閔(Sue-Min Chang)

《界面科學會誌》 27卷1期 (2005/03) Pp. 65-75

https://doi.org/10.30020/JCCIS.200503.0007

摘要

奈米級鐵氧化物與亞鐵離子形成的鐵面結合鐵系統具有廣大比表面積及強還原力，適合作為吸附重金屬及及分解氯化有機物之用途。本研究主要針對奈米級赤鐵礦與氫氧化鐵所形成之表面結合鐵系統進行銅離子與四氯化碳之共分解研究。X-光粉末繞射及掃描式電子顯微鏡分析結果發現，所合成之奈米鐵氧化物顆粒大小約為30-100nm，比表面積為39.8 - 222 m^2/g，亞鐵離子在赤鐵礦表面的吸附符合Langmuir等溫吸附模式，而在氫氧化鐵表面的吸附則可用Freundlich方程式描述。奈米鐵氧化物對銅離子的吸附能力高於亞鐵離子，其吸附行為符合Langmuir 等溫吸附方程式。奈米級表面結合鐵系統對四氯化碳也有不錯的還原脫氯能力，其擬一階反應動力常數（kobs）在赤鐵礦及氫氧化鐵系統中分別為0.0836 及0.0609 h^(-1)，氯仿產生量則為7.3 -13 M間。銅離子的存在則大幅增加表面結合鐵分解氯化有機物的能力，當添加0.5 mM Cu(II)時，其kobs值可增加3-30倍，顯示奈米表面結合鐵系統在厭氧環境中能同時去除銅離子與氯化有機物。

關鍵字

四氯化碳 ； 奈米鐵氧化物 ； 表面結合鐵系統 ； 脫氯反應 ； 銅離子

並列摘要

The transformation of carbon tetrachloride (CT) and copper ions by Fe(II) ions associated with nanocrystalline iron oxides minerals including hematite (α-Fe2O3) and ferrihydrite (Fe(OH)3) was investigated. Experiments were performed using 10 mM iron oxides and 3 mM Fe(II) to form surface-bound iron suspensions at pH 7.2 under anoxic condition. X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM) showed that the particle sizes of synthesized iron oxides were in the range of 30 - 100 nm. In addition, the specific surface areas of nanocrystalline hematite and ferrihydrite were 39.4 and 222 m^2/g, respectively. The sorption of Fe(II) ions onto hematite followed Langmuir sorption equation, while sorption of Fe(II) ions onto ferrihydrite obeyed Freundlich isotherm kinetics, presumably due to the high specific surface area of ferrihydrite. In addition, the sorption of Cu(II) ion onto iron oxides also followed Langmuir isotherm. The dechlorination of CT by surface-bound iron species followed pseudo first-order kinetics. The rate constants (kobs) for CT dechlorination were 0.0836 and 0.0609 h^(-1) in hematite and ferrihydrite suspensions, respectively. The produced chloroform ranged 7.3-13 μM, depicting that reductive dechlorination is the major pathway for CT dechlorination in surface-bound iron system. Addition of 0.5 mM Cu(II) greatly enhance the dechlorination efficiency and rate of CT. The kobs for CT dechlorination were 3 and 30 times greater than those in the absence of Cu(II) in the ferrihydrite and hematite systems, respectively. These results show that the Cu(II) plays a positive role in enhancing the dechlorination efficiency and rate of CT by Fe(II) associated with nanocrystalline iron oxides.

並列關鍵字

Carbon tetrachloride (CT) ； Nanocrystalline iron oxides ； Surface-bound iron species ； Dechlorination ； Copper ion