Nitrate contamination of aquatic systems represents a pressing global environmental challenge. This investigation centered on the catalytic reduction of aqueous nitrate through synergistic application of zero-valent iron (Fe 0 ) and Pd-Cu bimetallic catalysts. Key objectives included operational parameter optimization via response surface methodology (RSM), mechanistic elucidation of reaction pathways, strategic enhancement of N 2 selectivity, and comprehensive kinetic analysis. Under RSM-derived optimal conditions (20 mg L -1 NaNO 3 , 3 g L -1 Fe 0 , pH 5.2, 127-min duration, Pd:Cu mass ratio 3.4, 3.2 g L -1 catalyst), Pd-Cu/graphene achieved a remarkable 71.6% N 2 selectivity. Three enhancement strategies were identified: (1) transition to composite supports, exemplified by Pd-Cu/γ-Al 2 O 3 -diatomite (68% N 2 selectivity) outperforming single-component counterparts (Pd-Cu/γ-Al 2 O 3 : 66%; Pd-Cu/diatomite: 57%); (2) acid-washing pretreatment of carrier with 1 mol L -1 HCl, elevating Pd-Cu/diatomite N 2 selectivity from 56% to 62% while marginally reducing Pd-Cu/γ-Al 2 O 3 from 67% to 64%; and (3) active-site modification with sodium bis(2-ethylhexyl) sulfosuccinate (AOT), boosting N 2 selectivity by 4-8% in Pd AOT -Cu systems. Based on the catalytic denitrification kinetic studies of 16 different supported catalysts, kinetic analysis confirmed first-order behavior governing the nitrate reduction process, which proceeds through a multistep surface-mediated mechanism.
Yun et al. (Tue,) studied this question.