Pathway and mechanism study on improvement of N2 selectivity of catalytic denitrification

Abstract

Recently, nitrate pollution has attracted more public attention. In order to truly remove nitrate and reduce total nitrate content (TN) in water body, more harmless N2 should be converted from nitrate. Studies on catalytic removal of nitrate in wastewater have been carried out. However, the catalytic performance still needs to be significantly improved, especially the N2 selectivity. According to these, strategies that enable to efficiently improve N2 selectivity of catalytic denitrification were explored in this paper. Results implied that the catalyst with composite carrier that possesses porous structure, large surface area, excellent electronic properties, and stable physical–chemical property tends to have better catalytic performance. It is suggested that acid washing by 2 mol/L HCl for certain carriers be applied to enhancement of N2 selectivity. Additionally, higher N2 conversion was also achieved by addition of sodium bis-2-ethylhexyl sulphosuccinate (AOT) onto Pd with the formation of PdAOT-Cu catalyst, which may be ascribed to the AOT that partially shields Pd active sites and inhibits hydrogen spillover from Pd to Cu. Response Surface Methodology (RSM) was utilized for experimental design and prediction of the optimal parameters. More N2 was obtained under the predicted optimal conditions: 5.0 pH, 135 min time, 3.1 Pd: Cu, and 3.1 g/L Fe(0).