Smuleac V, Varma R, Sikdar S, Bhattacharyya D
Dept. of Chemical and Materials Engineering, University of Kentucky Lexington, KY 40506 USA.
J Memb Sci. 2011 Sep 1;379(1-2):131-137. doi: 10.1016/j.memsci.2011.05.054.
Membranes containing reactive nanoparticles (Fe and Fe/Pd) immobilized in a polymer film (polyacrylic acid, PAA-coated polyvinylidene fluoride, PVDF membrane) are prepared by a new method. In the present work a biodegradable, non-toxic -"green" reducing agent, green tea extract was used for nanoparticle (NP) synthesis, instead of the well-known sodium borohydride. Green tea extract contains a number of polyphenols that can act as both chelating/reducing and capping agents for the nanoparticles. Therefore, the particles are protected from oxidation and aggregation, which increases their stability and longevity. The membrane supported NPs were successfully used for the degradation of a common and highly important pollutant, trichloroethylene (TCE). The rate of TCE degradation was found to increase linearly with the amount of Fe immobilized on the membrane, the surface normalized rate constant (k(SA)) being 0.005 L/m(2)h. The addition of a second catalytic metal, Pd, to form bimetallic Fe/Pd increased the k(SA) value to 0.008 L/m(2)h. For comparison purposes, Fe and Fe/Pd nanoparticles were synthesized in membranes using sodium borohydride as a reducing agent. Although the initial k(SA) values for this case (for Fe) are one order of magnitude higher than the tea extract synthesized NPs, the rapid oxidation reduced their reactivity to less than 20 % within 4 cycles. For the green tea extract NPs, the initial reactivity in the membrane domain was preserved even after 3 months of repeated use. The reactivity of TCE was verified with "real" water system.
通过一种新方法制备了包含固定在聚合物膜（聚丙烯酸，涂覆有聚丙烯酸的聚偏二氟乙烯，PVDF膜）中的反应性纳米颗粒（Fe和Fe/Pd）的膜。在本工作中，使用一种可生物降解、无毒的“绿色”还原剂——绿茶提取物来合成纳米颗粒，而不是众所周知的硼氢化钠。绿茶提取物含有多种多酚，它们既可以作为纳米颗粒的螯合/还原剂，又可以作为封端剂。因此，颗粒受到保护，防止氧化和聚集，这增加了它们的稳定性和寿命。负载在膜上的纳米颗粒成功用于降解一种常见且非常重要的污染物——三氯乙烯（TCE）。发现TCE的降解速率随固定在膜上的Fe量线性增加，表面归一化速率常数（k(SA)）为0.005 L/m²h。添加第二种催化金属Pd形成双金属Fe/Pd后，k(SA)值增加到0.008 L/m²h。为了进行比较，使用硼氢化钠作为还原剂在膜中合成了Fe和Fe/Pd纳米颗粒。尽管这种情况下（对于Fe）的初始k(SA)值比用茶提取物合成的纳米颗粒高一个数量级，但快速氧化使其在4个循环内的反应性降低到不到20%。对于绿茶提取物纳米颗粒，即使在重复使用3个月后，膜域中的初始反应性仍得以保留。用“实际”水系统验证了TCE的反应性。
