An artificial denitrification catalyst that works in a mild environment

March 29, 2018

Environmental purification technology gleaned from microorganism mechanisms

Environmental pollution has worsened from excessive use of nitrogen fertilizers to produce food for an increasing population. The nitrous oxides contained in nitrogenous fertilizers are highly water soluble and flow into groundwater and rivers, causing contamination of drinking water, eutrophication of lakes and red tides. As such, nitrous oxide emissions are strictly regulated. Microbial denitrification reactions are one way to remove nitrous oxides. In this reaction, nitrous oxides are converted to nitrogen molecules by reducing nitrate and nitrite ions, thereby detoxifying such nitrogen compounds. However, such microbial-based treatment methods requires large-scale equipment, and there are also problems treating nitrate ions in high concentrations.

An international collaborative research team of researchers from RIKEN CSRS, Shanghai Jiao Tong University and Korea Basic Research Institute have succeeded in developing an artificial catalyst that mimics microbial denitrification enzymes, demonstrating highly efficient conversion of nitrate ions to harmless di-nitrogen.

The team considered ways to create a completely artificial denitrification catalyst based on microbial denitrification reactions. They found that an oxygen-containing molybdenum sulfide converted nitrate ions to nitrogen molecules in a mild reaction condition. The key to this catalyst development was to deliberately shift the timing of electron and proton (hydrogen ion) movements at the selectivity determining step of the overall denitrification reaction. This shift improved the selectivity of nitrogen production to record levels (13.5%) with just a pH change.

Further improvement of the selectivity is expected to lead to new denitrification technologies with artificial catalysts, and possibly the development of new technologies to synthesize ammonia from waste liquids.

Original article
Journal of the American Chemical Society doi:10.1021/jacs.7b12774
D. He, Y. Li, H. Ooka, Y. K. Go, F. Jin, S. H. Kim, R. Nakamura,
"Selective electrocatalytic reduction of nitrite to dinitrogen based on decoupled proton-electron transfer".
Ryuhei Nakamura; Team Leader
Daoping He; International Program Associate
Biofunctional Catalyst Research Team