Dechlorination of Pentachlorophenol by Palladium/Iron Nanoparticles Immobilized in a Membrane Synthesized by Sequential and Simultaneous Reduction of Trivalent Iron and Divalent Palladium Ions

Dechlorination of pentachlorophenol (PCP) by zero-valent iron (Fe-0) and palladium (Pd)/iron (Fe) bimetallic nanoparticles (NPs) immobilized in nylon 6,6/PEG membranes was investigated at room temperature. Pd/Fe bimetallic NPs were synthesized by two different approaches, sequential and simultaneous reduction of trivalent iron (Fe3+) and divalent palladium (Pd2+) ions. Pd/Fe NPs prepared by simultaneous reduction showed a much smaller particle size, only 30 nm in average, and significantly higher reactivity toward PCP dechlorination than the other two materials. Almost 85% PCP removal within 45 min was qualified in terms of both phenol emergence and chlorine ion release. In contrast, dechlorination efficiency by Pd/Fe NPs immobilized by sequential reduction was insignificant. Iron oxides between Fe-0 and Pd-0 during the sequential reduction process impeded their effective contact, and enhanced PCP sorption on membranes. Spectra of X-ray photoelectron spectroscopy confirmed the existence of both Fe-0 and iron oxide on the surface of these three NPs. This investigation has revealed that Pd/Fe NPs immobilized by simultaneous reduction may serve as a suitable medium for in situ remediation, even though it is difficult to avoid the formation of iron oxides.