Membrane-based Bimetallic Nanoparticles for Environmental Remediation: Synthesis and Reactive Properties Jian Xu and Dibakar Bhattacharyya Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506-0046; db@engr.uky.edu (for correspondence) Published online 3 November 2005 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ep.10106 Nanoscale bimetallic particles have important appli- cations in the environmentally important catalytic re- actions at room temperature because of the novel phys- ical and chemical properties. We report an innovative in situ synthesis method of functionalizing microfiltra- tion membranes with highly reactive bimetallic core/ shell Fe/Ni and Fe/Pd nanoparticles. The core/shell structure was confirmed by X-ray energy dispersive spectroscopy mapping images. Using TCE and PCB as model compounds, the reactivity of membrane-immo- bilized bimetallic nanoparticles was quantified in terms of both reaction mechanism shift and product distribution. Complete dechlorination was achieved with both compounds. © 2005 American Institute of Chem- ical Engineers Environ Prog, 24: 358 –366, 2005 Keywords: nanostructured metals, PVDF mem- branes, polyacrylic acid, Fe/Ni, Fe/Pd, TCE, PCB, chlo- rinated organics INTRODUCTION The creation of nanosized bimetallic particles having alloy or core/shell structure inside polymer domains has received intensive attention in the study of optical [1], electronic, magnetic [2], and biological [3] devices, and highly sensitive sensors [4]. Application of bimetal- lic nanoparticles (NPs) in catalytic reactions is particu- larly attractive [5–7] because of the unique physical and chemical properties of nanostructure over bulk struc- ture as well as the improvement of reactive properties. For example, significant changes of the topology found on the NP surface result in various facets, edges, cor- ners, and defects [8], which could create additional reactive sites. Small metal particles having a high bind- ing energy of their core electrons can influence the interaction between the surface sites with the reactants and products. The presence of secondary metal brings novel catalytic properties that are absent in the mono- metallic particles [9]. The deposition of a second metal can also enhance chemical reactivity by changing the electronic properties of the surface [10]. The creation and development of nanosized mate- rials have brought important and promising techniques into the field of pollution control. Recently, various studies have been reported on the groundwater reme- diation through degradation of toxic chlorinated or- ganic compounds (COCs) with nonimmobilized Fe 0 - based bimetallic NPs (Fe/Ni, Fe/Pd) [11–14]. In this case, COCs are reduced to nontoxic (or less) hydrocar- bons in the presence of the second catalytic metal (Pd or Ni) by substitution of chlorine with hydrogen. Com- pared to the single zerovalent Fe system (such as iron filings), which has been used for decades for degrada- tion of COCs, this catalytic hydrodechlorination tech- nology has been developed because of enhanced re- action rate and elimination of toxic by-product formation as a result of the second, catalytic metal. Correlations between reactive properties and the NP structure, the distribution of first and second metals, composition of the second metal, and particle size (nano vs. bulk size) have not been clarified. The bime- © 2005 American Institute of Chemical Engineers 358 December 2005 Environmental Progress (Vol.24, No.4)