Abstract
Abstract
Activities and selectivities of iron/palladium (Fe/Pd) bimetallic nanoparticles supported on various resin materials (chelating resins DOW 3N, cation-exchange resin D001, and anion-exchange resin D201) were studied for the reduction of nitrate in water. Scanning electron microscopy–energy dispersive spectrometry and transmission electron microscopy results indicated that the Fe/Pd bimetallic nanoparticles were well dispersed without aggregation on the three resin supports, indicating that the resins were favorable supports for Fe/Pd bimetallic nanoparticles. The surface chemistry of the support plays an important role in the activity and selectivity of Fe/Pd bimetallic nanoparticles. D201-Fe/Pd and DOW 3N-Fe/Pd exhibited high removal efficiency of nitrate (100% and 97.8%, respectively), whereas D001-Fe/Pd exhibited low efficiency (21.0%) of nitrate removal. This is mainly because the fixed negatively charged functional groups on the surface of D001 prevented nitrate permeation owing to the Donnan exclusion effect. Moreover, almost all reduction products with D001-Fe/Pd and D201-Fe/Pd were ammonia, whereas 69.2% N2 selectivity was obtained with DOW 3N-Fe/Pd. The transfer of nitrite from the Fe surface to the Pd surface was regarded as a key step in determining the selectivity for N2. There was no strong electrostatic repulsion or electrostatic attraction between nitrite and DOW 3N-Fe/Pd. The intermediate reduction product nitrite can be transformed from Fe to Pd freely, and can be reduced by Hads on the surface of Pd to N2, resulting in high N2 selectivity. Therefore, the chelating resin, which has no strong electrostatic force between itself and nitrate, was suitable as the support for bimetallic nanoparticles to selectively reduce nitrate.
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