State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
J Hazard Mater. 2010 Jul 15;179(1-3):596-603. doi: 10.1016/j.jhazmat.2010.03.045. Epub 2010 Mar 17.
Desorption of hydrophobic organic compounds from micropores is characteristically slow compared to surface adsorption and partitioning. The slow-desorbing mass of a hydrophobic probe molecule can be used to calculate the hydrophobic micropore volume (HMV) of microporous solids. A gas chromatographic apparatus is described that allows characterization of the sorbed mass with respect to the desorption rate. The method is demonstrated using a dealuminated zeolite and an aquifer sand as the model and reference sorbents, respectively, and trichloroethylene (TCE) as the probe molecule. A glass column packed with the microporous sorbent is coupled directly to a gas chromatograph that is equipped with flame ionization and electron capture detectors. Sorption and desorption of TCE on the sorbent was measured by sampling the influent and effluent of the column using a combination of switching and injection valves. For geosorbents, the HMV is quantified based on Gurvitsch's rule from the mass of TCE desorbed at a rate that is characteristic for micropores. Instrumental requirements, design considerations, hardware details, detector calibration, performance, and data analysis are discussed along with applications. The method is novel and complements traditional vacuum gravimetric and piezometric techniques, which quantify the total pore volume under vacuum conditions. The HMV is more relevant than the total micropore volume for predicting the fate and transport of organic contaminants in the subsurface. Sorption in hydrophobic micropores strongly impacts the mobility of organic contaminants, and their chemical and biological transformations. The apparatus can serve as a tool for characterizing microporous solids and investigating contaminant-solid interactions.
与表面吸附和分配相比，疏水分子从微孔中解吸的速度通常较慢。疏水性探针分子的缓慢解吸质量可用于计算微孔固体的疏水性微孔体积（HMV）。本文介绍了一种气体色谱仪器，该仪器允许根据解吸速率对吸附质量进行特征化。该方法使用脱铝沸石和含水层砂分别作为模型和参考吸附剂，以及三氯乙烯（TCE）作为探针分子进行了演示。用微孔吸附剂填充的玻璃柱直接与配备火焰离子化和电子俘获检测器的气相色谱仪相连。通过使用切换阀和注入阀的组合来采样柱的入口和出口，测量 TCE 在吸附剂上的吸附和解吸。对于地质吸附剂，根据 Gurvitsch 规则，基于在微孔特征速率下解吸的 TCE 的质量来量化 HMV。本文讨论了仪器要求、设计考虑因素、硬件细节、检测器校准、性能和数据分析，以及应用。该方法是新颖的，补充了传统的真空重量法和压阻技术，后者在真空条件下量化总孔体积。与总微孔体积相比，HMV 更能预测有机污染物在地下环境中的归宿和迁移。疏水性微孔中的吸附强烈影响有机污染物的迁移性及其化学和生物转化。该仪器可作为表征微孔固体和研究污染物-固体相互作用的工具。
