Synthesis and characterization of green agents coated Pd/Fe bimetallic nanoparticles

• Green agents modified Pd/Fe NPs have been synthesized.
• Dispersity of modified Pd/Fe NPs in aqueous phase was successfully increased.
• Dechlorination reactivity of modified Pd/Fe NPs was enhanced.
• Reactive mechanism and kinetics were investigated.

The low stability and mobility of nanoparticles in liquid phase is one of the biggest challenges for the application of zero-valent iron (ZVI) technology. In this research, three green agents, polyethylene glycol (PEG), starch, and guar gum were coated on Pd/Fe bimetallic nanoparticles (NPs) to enhance the stability and reactivity of Pd/Fe NPs. The modified NPs (PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs) were characterized in terms of specific surface area, particle size, shape, morphology, and structural feature, etc. The results show that the diameters of modified Pd/Fe NPs are in the range of 60–100 nm. Compared with the pristine unmodified Pd/Fe NPs, the aggregations of modified Pd/Fe NPs were successfully reduced. XRD patterns indicate that modified Pd/Fe NPs remained the body centered cubic crystal structure, and the modification process contributed to improve the antioxidant ability. 2,4-Dichlorophenol (2,4-DCP) dechlorination experiments show that physico-chemical properties of the three modifiers have different effects on the reactivity of modified Pd/Fe NPs. The initial pH value of the reaction system had complex effects on the dechlorination of 2,4-DCP by using modified Pd/Fe NPs. Activation energies of pristine, PEG-Pd/Fe, Starch-Pd/Fe, and Guar gum-Pd/Fe NPs were calculated to be 39.47 kJ/mol, 38.66 kJ/mol, 36.59 kJ/mol, and 33.88 kJ/mol, respectively, implying that the modification process can enhance the dechlorination rate of Pd/Fe NPs, and that catalytic hydrodechlorination process of 2,4-DCP with modified Pd/Fe NPs is a surface-controlled chemical reaction.