Practical application of Pd-based bimetallic catalysts with enhanced selectivity supported by chelating resin for catalytic nitrate reduction in real water

Abstract

An innovative Pd-Me (Pd-Cu, Pd-In and Pd-Sn) bimetallic catalyst supported on porous chelating DOWEX M4195 resin (D) was established to reduce the nitrate almost entirely and achieved high selectivity to the expected harmless form of nitrogen. In this study, sodium borohydride (NaBH4) was applied in preparing bimetallic catalysts by liquid-phase reduction as the prestoring reductant. Pd-In/D and Pd-Sn/D groups performed well in N2 selectivity (all above 97%). In addition, Pd-In and Pd-Sn bimetallic catalysis yields higher selectivity towards N2 than the Pd-Cu pair in the presence of HCO3 −, Cl−, SO4 2− and humic acid. Likewise, in terms of N2 selectivity, Pd-In/D and Pd-Sn/D bimetallic catalysts were superior to that of Pd-Cu/D (72.16%) in the municipal wastewater treatment plant sewage. The current results provide insight into the superb reactivity, excellent stability, and most important—extremely high harmless N2 selectivity of Pd-In and Pd-Sn-based bimetallic catalysts in practical application and provide new ideas for enhancing the feasibility of the catalytic reduction of nitrate by minimizing environmentally harmful by-products.