Department of Civil & Environmental Engineering , Pennsylvania State University , 212 Sackett Building , University Park , Pennsylvania 16802 , United States.
Eawag , Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf , Switzerland.
Environ Sci Technol. 2018 May 15;52(10):5600-5609. doi: 10.1021/acs.est.8b00481. Epub 2018 Apr 11.
Numerous studies have reported that pollutant reduction rates by ferrous iron (Fe) are substantially enhanced in the presence of an iron (oxyhydr)oxide mineral. Developing a thermodynamic framework to explain this phenomenon has been historically difficult due to challenges in quantifying reduction potential ( E) values for oxide-bound Fe species. Recently, our group demonstrated that E values for hematite- and goethite-bound Fe can be accurately calculated using Gibbs free energy of formation values. Here, we tested if calculated E values for oxide-bound Fe could be used to develop a free energy relationship capable of describing variations in reduction rate constants of substituted nitrobenzenes, a class of model pollutants that contain reducible aromatic nitro groups, using data collected here and compiled from the literature. All the data could be described by a single linear relationship between the logarithms of the surface-area-normalized rate constant ( k) values and E and pH values [log( k) = - E/0.059 V - pH + 3.42]. This framework provides mechanistic insights into how the thermodynamic favorability of electron transfer from oxide-bound Fe relates to redox reaction kinetics.
许多研究报告指出，在存在铁（氧）氢氧化物矿物的情况下，亚铁（Fe）的污染物还原率会大幅提高。由于难以量化氧化物结合态 Fe 物种的还原电位 (E) 值，因此历史上一直难以开发出用于解释这一现象的热力学框架。最近，我们小组证明，使用生成自由能值可以准确计算赤铁矿和针铁矿结合态 Fe 的 E 值。在这里，我们测试了计算得出的氧化物结合态 Fe 的 E 值是否可用于开发自由能关系，从而能够描述取代硝基苯（一类含有可还原芳香硝基基团的模型污染物）的还原速率常数的变化，这些数据是通过在此处收集和从文献中汇编的数据得到的。所有数据都可以通过表面面积归一化速率常数 (k) 值与 E 和 pH 值的对数之间的单一线性关系来描述 [log(k) = - E/0.059 V - pH + 3.42]。该框架提供了关于从氧化物结合态 Fe 转移电子的热力学有利程度与氧化还原反应动力学之间关系的机理见解。
