N-nitrosodimethylamine (NDMA) and related N-nitrosamines are a family of extremely potent carcinogens which raise serious public health concerns since they are widely found as disinfection by-products. Catalytic reductive process has been investigated as a rapid and economical treatment option for NDMA-contaminated water because the N-N=O moiety can be effectively reduced by hydrogen at the presence of metallic catalysts. Nickel shows the highest reactivity among the tested metallic catalysts, but are readily deactivated when exposed to dissolved oxygen, severely limiting their application for water treatment. The development of stable and active noble metals is thus highly required. Here, we report the synthesis of palladium nanoparticles with a simple but effective method without addition of any stabilizer. The clean and highly dispersed palladium shows significantly improved reactivity and its turnover frequency (0.69 ± 0.03 h -1) outperforms previously reported pure metallic catalysts, including nickel. Kinetic studies show that reduction of NDMA is pH and NDMA concentration dependent and the highest activity is observed at pH=5 and C(NDMA)=100 μM. The reaction is moderately temperature sensitive with an activation energy of 47 ± 3 kJ/mol. We further show that the reactivity of the catalyst reduces with the addition of polyvinylpyrrolidone, a commonly used polymer stabilizer during synthesis of nanoparticles, suggesting the accessible surface of the catalyst can be blocked by stabilizers. Based on Fourier transform infrared spectroscopy, we propose that the clean palladium surface is responsible for its high reactivity, which is protected by trace amount of acetate formed during the synthesis process.

Highly active palladium nanoparticles for catalytic reduction of N-nitrosodimethylamine

253rd National Meeting (2017)

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