Urynowicz Michael A, Balu Balamurali, Udayasankar Umamaheshwari
Department of Civil & Architectural Engineering, University of Wyoming, Laramie, Wyoming 82071, USA.
J Contam Hydrol. 2008 Feb 19;96(1-4):187-94. doi: 10.1016/j.jconhyd.2007.11.001. Epub 2007 Nov 17.
During in situ chemical oxidation with permanganate, natural organic matter and other reduced species in the subsurface compete with the target compounds for the available oxidant and can exert a significant natural oxidant demand. This competition between target and nontarget compounds can have a significant impact on the permeation, dispersal, and persistence of permanganate in the subsurface. The kinetics of natural oxidant demand by permanganate was investigated using a composite sample made up of aquifer material collected from three different sites. The study found that although the depletion of organic carbon increased with increased permanganate dosage and increased reaction period, the mass ratio of MnO(4)(-):OC (wt/wt) was relatively constant over time (11.4+/-0.9). The reaction order and rate with respect to permanganate were found to decrease with time suggesting a continuum of reactions with the slower reactions becoming more controlling with time. However, the data also suggests that this continuum of reactions can be simplified into short- and long-term kinetic expressions representing fast and slow reactions. An independent first-order kinetic model with separate fast and slow reaction rate constants was used to successfully describe the complete kinetic expression of natural oxidant demand. The kinetic parameters used in the model are easily determined and can be used to better understand the complex kinetics of natural oxidant demand.
在用高锰酸盐进行原位化学氧化过程中，地下水中的天然有机物和其他还原物质会与目标化合物竞争可用的氧化剂，并产生显著的天然氧化剂需求。目标化合物与非目标化合物之间的这种竞争会对高锰酸盐在地下水中的渗透、扩散和持久性产生重大影响。使用从三个不同地点采集的含水层材料组成的复合样品，研究了高锰酸盐对天然氧化剂需求的动力学。研究发现，尽管有机碳的消耗随着高锰酸盐剂量的增加和反应时间的延长而增加，但MnO₄⁻:OC的质量比（重量/重量）随时间相对恒定（11.4±0.9）。发现高锰酸盐的反应级数和反应速率随时间降低，这表明存在一系列反应，较慢的反应随着时间的推移变得更具控制性。然而，数据还表明，这种反应的连续性可以简化为代表快速和慢速反应的短期和长期动力学表达式。使用具有单独快速和慢速反应速率常数的独立一级动力学模型成功地描述了天然氧化剂需求的完整动力学表达式。该模型中使用的动力学参数易于确定，可用于更好地理解天然氧化剂需求的复杂动力学。
