Meyer D E, Bhattacharyya D
University of Kentucky, Department of Chemical and Materials Engineering, Lexington, Kentucky 40506-0046, USA.
J Phys Chem B. 2007 Jun 28;111(25):7142-54. doi: 10.1021/jp070972u. Epub 2007 May 26.
The use of membrane immobilization to carry out the batch dechlorination of trichloroethylene (TCE) using bimetallic Fe/Ni (4:1, Fe to Ni) nanoparticles in cellulose acetate membranes is examined using modeling of transport phenomenon based on experimental results. Membranes are synthesized using both gelation and solvent evaporation techniques for phase inversion. The reduction of metal ions within cellulose acetate phase-inversion membranes was accomplished using sodium borohydride reduction to obtain up to 2 wt % total metals. Characterization of the mixed-matrix structure reveals a bimodal particle distribution ranging between 18 and 80 nm within the membrane cross section. The distribution is the result of changes in the morphology of the cellulose acetate support. The diffusivity and linear partitioning coefficient for the chlorinated organic were measured and are 2.0 x 10(-8) cm2.s-1 and 3.5 x 10(-2) L.g-1, respectively. An unsteady-state model for diffusion through a membrane with reaction was developed to predict experimental results with an error of only 7.2%. The error can be attributed to the lack of the model to account for loss of reactivity through pH effects, alloy effects (bimetallic ratio), and oxidation of nanoparticles. Simulations were run to vary the major transport variables, partitioning and diffusivity, and determine their impact on reaction kinetics. Of the two, diffusivity was less significant because it really only influences the time required for maximum TCE partitioning to the membrane to be achieved and has no effect on the limiting capacity of the membrane for TCE. Therefore, selection of an appropriate support material is crucial for development of highly reactive mixed-matrix membrane systems.
基于实验结果，利用传输现象模型研究了在醋酸纤维素膜中使用双金属铁/镍（4:1，铁与镍的比例）纳米颗粒通过膜固定化进行三氯乙烯（TCE）间歇式脱氯的情况。膜是使用凝胶化和溶剂蒸发技术进行相转化合成的。通过硼氢化钠还原实现醋酸纤维素相转化膜内金属离子的还原，以获得高达2 wt%的总金属含量。混合基质结构的表征显示，膜横截面内的双峰颗粒分布范围在18至80纳米之间。这种分布是醋酸纤维素载体形态变化的结果。测量了氯化有机物的扩散系数和线性分配系数，分别为2.0×10⁻⁸ cm²·s⁻¹和3.5×10⁻² L·g⁻¹。建立了一个通过有反应的膜扩散的非稳态模型来预测实验结果，误差仅为7.2%。该误差可归因于模型未能考虑通过pH效应、合金效应（双金属比例）和纳米颗粒氧化导致的反应活性损失。进行了模拟以改变主要传输变量、分配和扩散系数，并确定它们对反应动力学的影响。在这两者中，扩散系数的影响较小，因为它实际上只影响达到TCE在膜上最大分配所需的时间，而对膜对TCE的极限容量没有影响。因此，选择合适的载体材料对于开发高反应性混合基质膜系统至关重要。
