Nico P S, Zasoski R J
Department of Land, Air, and Water Resources, University of California, Davis 95616, USA.
Environ Sci Technol. 2001 Aug 15;35(16):3338-43. doi: 10.1021/es001848q.
Manganese oxides are involved in many environmentally important redox reactions. This work focuses primarily on the reaction of phenol and sulfide with delta-MnO2 (birnessite) and the inhibitory effect of pyrophosphate on these reactions. The reactions were modeled in terms of Mn(III) center surface availability. The model partitioned the observed rate constants between two different hypothetical reaction pathways. One of these pathways was deemed to be dependent on Mn(III) center concentration, while the other was Mn(III) center independent. The relative contribution of each pathway was then calculated based on the equilibrium concentration of free Mn(III) centers at a given pyrophosphate concentration. Using this approach it was possible to model the observed pyrophosphate effects and to predict inhibition with respect to reactant concentration. Finally, the effects of pyrophosphate and orthophosphate on the reaction of sulfide and hydroquinone with delta-MnO2 were observed and compared to previously published observations. The observed orthophosphate and pyrophosphate effects were consistent with the two reaction pathway model in terms of Mn(III) center complexation. These findings have important implications for modeling and understanding the fate and transport of redox reactive material.
氧化锰参与了许多对环境具有重要意义的氧化还原反应。这项工作主要聚焦于苯酚和硫化物与δ-MnO₂（水钠锰矿）的反应以及焦磷酸盐对这些反应的抑制作用。这些反应是根据Mn(III)中心的表面可利用性进行建模的。该模型将观测到的速率常数划分到两种不同的假设反应途径中。其中一条途径被认为依赖于Mn(III)中心浓度，而另一条则与Mn(III)中心无关。然后根据给定焦磷酸盐浓度下自由Mn(III)中心的平衡浓度计算每条途径的相对贡献。采用这种方法，可以对观测到的焦磷酸盐效应进行建模，并预测对反应物浓度的抑制作用。最后，观察了焦磷酸盐和正磷酸盐对硫化物和对苯二酚与δ-MnO₂反应的影响，并与之前发表的观察结果进行了比较。就Mn(III)中心络合而言，观测到的正磷酸盐和焦磷酸盐效应与双反应途径模型一致。这些发现对于建模和理解氧化还原活性物质的归宿和迁移具有重要意义。
