Nitrate reduction with bimetallic catalysts. A stability-addressed overview

Nitrate (NO3-) pollution of water bodies is a serious environmental problem worldwide. One of the major concerns about NO3- contamination is the lack of cost-effective solutions for its removal from potential drinking water resources. Current technologies, such as ion exchange, reverse osmosis and electrodialysis, produce a reject with high NO3- concentration. Catalytic reduction is an emerging technology, capable of transforming NO3- into harmless N-2. A critical issue is to achieve almost complete selectivity to this last species so that the final concentrations of NO2- and NH4+ can fit the stringent allowed limits. Numerous studies have been carried out evaluating the activity and N-2 selectivity of bimetallic catalysts. Catalyst deactivation by surface fouling, irreversible oxidation of the metal promoter, metal leaching and aggregation of metallic particles remain a major challenge for full-scale implementation of catalytic nitrate reduction. Therefore, it is necessary to develop highly stable catalyst and/or effective solutions for catalyst regeneration. The existing literature on this respect is reviewed hereby.