Logue Brian A, Westall John C
U.S. Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, Maryland 21010-5400, USA.
Environ Sci Technol. 2003 Jun 1;37(11):2356-62. doi: 10.1021/es026472q.
The rates of reduction of carbon tetrachloride (CT) and nitrobenzene (NB) by iron-oxide coated gold electrodes were studied to gain insight into the processes that control reduction of groundwater contaminants by zerovalent metal permeable reactive barriers. Fe(III)-oxide films were deposited on gold electrodes with a small fraction of the Fe(III) electrochemically reduced to Fe(II) to investigate the role of Fe(II) in the reduction of the CT and NB. Mass transport to the surface of the oxide film was controlled through use of a well-defined flow-through system similar to a wall-jet electrode. The factors affecting the overall reduction rate were investigated by varying the Fe(II) content in the iron-oxide, controlling mass transport of the electroactive species to the oxide surface, and varying the thickness of the oxide film. The rates of reduction of CT and NB were found to be independent of Fe(II) content in the iron-oxide and were only slightly dependent on the rate of transport to the surface of the oxide under a few sets of reaction conditions. Conversely, the rates of reduction were greatly dependent on the thickness of the oxide film, with the reduction rate decreasing as the oxide thickness increased. Evidence suggests that the location of the reduction reaction for CT and NB is at the gold surface and supports a barrier model for the system studied, in which the oxide film physically impedes direct contact of the electroactive species and the gold electrode, increases the diffusion path length, and creates adsorption sites.
研究了氧化铁包覆金电极对四氯化碳（CT）和硝基苯（NB）的还原速率，以深入了解零价金属渗透反应屏障控制地下水污染物还原的过程。将Fe(III) - 氧化物薄膜沉积在金电极上，使一小部分Fe(III) 电化学还原为Fe(II)，以研究Fe(II) 在CT和NB还原中的作用。通过使用类似于壁面射流电极的明确定义的流通系统来控制向氧化膜表面的传质。通过改变氧化铁中的Fe(II) 含量、控制电活性物质向氧化膜表面的传质以及改变氧化膜的厚度，研究了影响整体还原速率的因素。发现在几组反应条件下，CT和NB的还原速率与氧化铁中的Fe(II) 含量无关，仅略微依赖于向氧化膜表面的传质速率。相反，还原速率在很大程度上取决于氧化膜的厚度，随着氧化膜厚度的增加，还原速率降低。有证据表明，CT和NB还原反应的位置在金表面，并支持所研究系统的屏障模型，其中氧化膜物理上阻碍了电活性物质与金电极的直接接触，增加了扩散路径长度，并产生了吸附位点。
