Nitrate reduction by maghemite supported Cu-Pd bimetallic catalyst

Abstract

We have investigated the catalytic nitrate reduction by maghemite supported Cu-Pd bimetallic catalyst (maghemite/Cu/Pd). BET, XRD, XPS, TPR, SEM/EDX, TEM analysis were carried out to characterize maghemite/Cu/Pd. Remarkable nitrate removal (99.5%) by maghemite/Cu/Pd was observed in 90 min, while Cu-Pd catalyst supported with alumina (43%) and hematite (63%) showed less efficient nitrate removal. Nitrate removal was excellent (>95%) in all Cu loading variation (0.25-1 wt.%) on maghemite/Cu/Pd, while selectivity of nitrogen gas formed during the reaction was the highest (43%) at a specific Cu/Pd ratio (0.5/0.5 wt.%). We also observed excellent nitrate removals (>95 and >94%, respectively) by maghemite/Cu/Pd in the ranges of Pd loading (0.25-1 wt.%) and hydrogen flow rate (100-500 cc/min). The highest nitrogen selectivities (47 and 45%) were obtained by low Pd loading (0.25 wt.%) and hydrogen flow rate (200 cc/min). Maghemite/Cu/Pd showed slow decrease of nitrate removal (99.5-83%) and low metal leaching (1.5% of Cu leaching) during three reaction cycles. XPS analysis revealed that Cu(0) was oxidized to Cu2O and CuO during the catalytic nitrate reduction, while Pd(0) was not changed. (C) 2012 Elsevier B.V. All rights reserved.