School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, OK 73019, USA.
Water Res. 2010 Apr;44(7):2125-32. doi: 10.1016/j.watres.2009.12.026. Epub 2009 Dec 21.
Interest has grown in the use of reactive minerals for natural and engineered transformation of ground water contaminants. This study investigated how the structural properties of 10 model compounds representing natural organic matter (NOM) influenced their adsorption to chloride green rust (GR-Cl), and how this adsorption affected rate constants for transformation of carbon tetrachloride (CT) by GR-Cl. The affinity of benzoic acid, phthalic acid, trimesic acid, pyromellitic acid, and mellitic acid for the GR-Cl surface generally increased in the order of increasing number of carboxylic acid functional groups, increasing acidity of these functional groups, and increasing charge density. For NOM model compounds that had phenolic functional groups (p-hydroxybenzoic acid, alpha-resorcylic acid, and caffeic acid), the affinity for the GR-Cl surface was greatest for caffeic acid, which had two adjacent phenolic functional groups. Some NOM model compounds had experimentally determined Langmuir maximum adsorption capacities (q(max-Langmuir)) greater than those calculated based on external surface area measurements and the size of the NOM model compound, suggesting adsorption to internal as well as external sites at the GR-Cl surface for these compounds. Rate constants for CT transformation by GR-Cl generally decreased as the affinity of the NOM model compounds (estimated by Langmuir K values) increased, but there was no statistically significant correlation between Langmuir parameters (i.e., K and q(max-Langmuir)) and rate constants, perhaps due to significant adsorption of some NOM model compounds to sites that were not accessible to CT, such as interlayer sites. Unlike the other NOM model compounds, caffeic acid, which adsorbed to a significant extent to the GR-Cl surface, increased the rate constant for CT transformation. The influence of NOM on rate constants for CT transformation by green rusts should be considered in ground water remediation planning.
人们越来越感兴趣地将反应性矿物用于自然和人为转化地下水污染物。本研究调查了 10 种代表天然有机物 (NOM) 的模型化合物的结构特性如何影响它们对氯化绿锈 (GR-Cl) 的吸附，以及这种吸附如何影响 GR-Cl 转化四氯化碳 (CT) 的速率常数。苯甲酸、邻苯二甲酸、均苯三甲酸、均苯四甲酸和均苯四酸对 GR-Cl 表面的亲和力通常按羧酸官能团数量增加、这些官能团酸性增加和电荷密度增加的顺序增加。对于具有酚官能团的 NOM 模型化合物（对羟基苯甲酸、α-间苯二酚和咖啡酸），GR-Cl 表面的亲和力最大的是具有两个相邻酚官能团的咖啡酸。一些 NOM 模型化合物的实验确定的 Langmuir 最大吸附容量 (q(max-Langmuir)) 大于基于外部表面积测量和 NOM 模型化合物大小计算的值，这表明这些化合物在 GR-Cl 表面上除了外部位点之外，还吸附在内部分子。GR-Cl 转化 CT 的速率常数通常随着 NOM 模型化合物的亲和力（通过 Langmuir K 值估计）的增加而降低，但 Langmuir 参数（即 K 和 q(max-Langmuir)) 和速率常数之间没有统计学上的显著相关性，这可能是由于一些 NOM 模型化合物吸附到 CT 无法到达的位点，例如层间位点。与其他 NOM 模型化合物不同，咖啡酸在很大程度上吸附到 GR-Cl 表面，增加了 CT 转化的速率常数。在地下水修复规划中，应考虑 NOM 对绿锈转化 CT 速率常数的影响。
