Study on reaction mechanism and Langmuir-Hinshelwood kinetic model of catalytic denitrification by Fe0 and bimetallic catalyst

The focus of this research was on the catalytic reduction of nitrate to nitrogen gas for the water conservation. Zero-valent iron (Fe0) with bimetallic catalyst that carrier supported palladium (Pd) and copper (Cu) was innovatively applied in this study. First, XPS (X-ray photoelectron spectroscopy) analyses and experiments were conducted to study the mechanism of the catalytic reduction of nitrate. In the catalytic reaction, which is regarded as a stepwise process, Fe0 was the electron provider; Pd and Cu supported on carrier played indispensable but distinct roles. The kinetics suggested that the process was better reflected by first-order kinetics of the Langmuir-Hinshelwood model. Additionally, first-order kinetics of the catalytic reaction under the effect of catalysts with different carriers (SiO2, silica gel, kaolin, diatomite, γ-Al2O3, graphene) were further studied. Pd-Cu/graphene catalyst showed higher catalytic performance compared with other catalysts.