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Modification of Pd-Fe nanoparticles for catalytic dechlorination of 2,4-dichlorophenol.

The Science of the total environment (2013-02-22)
Xiangyu Wang, Minping Zhu, Huiling Liu, Jun Ma, Fang Li
ABSTRACT

To reveal how different dispersants influence the dispersity and physicochemical properties of palladium/iron nanoparticles (Pd/Fe NPs), we modified Pd/Fe NPs with poly(methylmethacrylate) (PMMA), polyacrylic acid (PAA) and cetyltrimethylammonium bromide (CTAB) respectively and obtained three hybrid NPs denoted M-Pd/Fe NPs, A-Pd/Fe NPs and C-Pd/Fe NPs. The physical properties of the three hybrid Pd/Fe NPs were studied, together with their behaviors in the room-temperature dechlorination in aqueous solution of 2,4-dichlorophenol (2,4-DCP). Dispersant effects of the three dispersants were observed, as well as changes in the properties of resulted Pd/Fe NPs. The pristine Pd/Fe NPs experienced more severe oxidation than A-Pd/Fe NPs, while there was no evidence for the presence of oxidation phase of M-Pd/Fe NPs and C-Pd/Fe NPs. Degradation results showed that compared with pristine Pd/Fe NPs, the catalytic dechlorination efficiency of 2,4-DCP with modified Pd/Fe NPs increased by 23%-58% within a given reaction period of 20 min. The role of dispersants themselves in dechlorination properties of Pd/Fe NPs is more significant than that of volume ratio of PAA to water, weight ratio of PMMA to anisole and volume ratio of water to ethanol in determining the properties of A-Pd/Fe, M-Pd/Fe and C-Pd/Fe NPs, respectively. Studies on the kinetics of 2,4-DCP reacted with Pd/Fe NPs in our cases implied that their behaviors didn't match the first- or pseudo-first-order kinetics: because the presence of oxidation phases on the surface of pristine Pd/Fe NPs and the dispersants on the surface of NPs could influence the diffusion of 2,4-DCP onto reactive sites, thus affecting the whole degradation process. So, an innovatively revised kinetics was proposed in the study for considering the effects of oxidation phases and the dispersants.

MATERIALS
Product Number
Brand
Product Description

Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 4,000
Sigma-Aldrich
Poly(methyl methacrylate)
Sigma-Aldrich
Poly(methyl methacrylate), average Mw ~350,000 by GPC
Sigma-Aldrich
Hexadecyltrimethylammonium chloride, ≥98.0% (NT)
Sigma-Aldrich
Hexadecyltrimethylammonium hydroxide solution, ~25% in methanol (T)
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 8,000
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 2,480,000
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 2,000
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 10,000
Sigma-Aldrich
Cetyltrimethylammonium chloride solution, 25 wt. % in H2O
Sigma-Aldrich
Chlorine, ≥99.5%
Sigma-Aldrich
Poly(methyl methacrylate)
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 100,000
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 20,000
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, 50,000
Sigma-Aldrich
Poly(methyl methacrylate), average Mw ~15,000 by GPC, powder
Sigma-Aldrich
2,4-Dichlorophenol, 99%
Sigma-Aldrich
Hexadecyltrimethylammonium hydroxide solution, 10 wt. % in H2O
Sigma-Aldrich
Cetyltrimethylammonium hydrogensulfate, 99%
Supelco
Poly(methyl methacrylate), analytical standard, for GPC, average Mw 97,000 (Typical), average Mn 46,000 (Typical)
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, BioUltra, for molecular biology, ≥99.0% (AT)
Supelco
Hexadecyltrimethylammonium bromide, suitable for ion pair chromatography, LiChropur
Supelco
Hexadecyltrimethylammonium bisulfate, suitable for ion pair chromatography, LiChropur, ≥99.0% (T)
Sigma-Aldrich
Poly(methyl methacrylate), isotactic, >80% isotactic
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, ≥98%
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, BioXtra, ≥99%
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, for molecular biology, ≥99%
Supelco
Hexadecyltrimethylammonium bromide, analytical standard
Sigma-Aldrich
Hexadecyltrimethylammonium bromide, ≥96.0% (AT)