The removal mechanisms of ionized polychlorinated phenolic chemical such as pentachlorophenol (PCP) with the zerovalent Pd/Fe bimetallic nanoparticles (NPs) in common water with oxygen include adsorption, dechlorination, and mineralization. The optimal Pd content of the bimetallic Pd/Fe NPs was around 0.05% by weight. Increase in both dosage of Pd/Fe NPs and temperature enhanced degradation rate and efficiency. The activation energy of 29 kJ/mol indicates that the degradation is a surface-mediated mechanism. Common dissolved anions inhibit PCP degradation in increasing order of Cl- < HCO3- < SO42- < HPO42- < NO3-. With the exception of NO3- and SO42-, this order generally consists with their affinity to form complexes with iron oxide, suggesting that the inhibitory effects may be attributed to passivation of reactive sites from Fe-anion complexes formed on the iron surface. NO3- could compete with PCP for reactive sites on the surface of iron. Sulfide produced from the reduction of SO42- by Pd/Fe could poison the Pd catalysts. Furthermore, multiple dechlorination is proposed. Dechlorination at the ortho and meta positions of chloride is easier than that at the para position, which results from the adsorption of ionized PCP on particles. The more effective removal of PCP and its byproduct with Pd/Fe NPs was demonstrated in oxic conditions than in anoxic conditions.

Oxidation and reduction of pentachlorophenol by zerovalent Pd/Fe nanoparticles in water

248th National Meeting (2014)

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