Pd and Pt nanoparticles supported on the mesoporous silica molecular sieve SBA-15 with enhanced activity and stability in catalytic bromate reduction

Abstract

Bromate is a highly carcinogenic disinfection by-product in drinking water. Catalytic reduction is an emerging technology that can effectively remove bromate from water without forming additional brines and sludges. In this study, Pd and Pt nanoparticles supported on SBA-15 were prepared for catalytic bromate reduction. The activity investigation results showed that the Pt/SBA-15 catalysts exhibited higher activities than the Pd/SBA-15 catalysts and the commercial 5% Pd/C catalyst, and the highest catalytic activity of 24.72 mg·min−1·gcat−1 was obtained using 4% Pt/SBA-15 as the catalyst. This activity is approximately 2.33- and 6.50-fold higher than the activities of the 4% Pd/SBA-15 and 5% Pd/C catalysts, respectively. Analysis of the intrinsic mechanism revealed that the activation energy of bromate reduction over the 4% Pt/SBA-15 catalyst was 47.31 kJ·mol−1, and the reaction followed the Langmuir-Hinshelwood mechanism, suggesting that the reduction of adsorbed bromate on the Pt surface rather than the diffusion process controlled the overall reaction rate. Catalytic bromate reduction was strongly dependent on the reaction pH, and the catalytic activity increased with decreasing pH. Bromate reduction was suppressed in the presence of coexisting anions, including PO43−, SO42−, and Cl−, and the inhibition effects followed the order of PO43− > SO42− > Cl−. Surprisingly, bromate removal was obviously enhanced when a low concentration (<1.5 mM) of nitrate coexisted in the reaction solution. In addition, the losses in catalytic activity and Pt after five repeated tests were only 7.8% and 2.6%, respectively, revealing the high stability of the 4% Pt/SBA-15 catalyst in the catalytic reduction of bromate.