Nano-hybrid bimetallic Au-Pd catalysts for ambient condition-catalytic wet air oxidation (AC-CWAO) of organic dyes

Abstract

In this work, a hybrid of Na2Mo4O13 and MoO3 (NM) was synthesized by a hydrothermal method, and Au-Pd nanoparticles were further deposited on NM by a facile one-pot deposition reduction method to obtain highly active and stable nano-hybrid bimetallic catalysts. The nano-hybrid bimetallic catalysts were systematically characterized and investigated for ambient condition-catalytic wet air oxidation (AC-CWAO) of organic dyes (Brilliant Green (BG), Safranine O (SO) and Methylene Blue (MB)) using air as the sole oxidant in aqueous solution. Au-Pd(1:1)/NM-400 with an Au/Pd mass ratio of 1:1 calcined at 400 °C possessed the highest catalytic activity compared to the catalysts with other Au/Pd mass ratios and the monometallic catalysts due to the synergistic effect of Au and Pd. It could be workable efficiently for high dye concentrations at reaction temperatures even close to 0 °C. Dye degradation kinetics investigation shows that dye degradation follows pseudo-first-order kinetics. High dye removal efficiency still could be achieved after five times reuse which indicated that it exhibited a good reusability and catalytic stability. The mechanism investigation for catalytic activity revealed that superoxide radical (O2−) is the main active oxidative specie during CWAO of dyes.