Nitrate electro-sorption/reduction in capacitive deionization using a novel Pd/NiAl-layered metal oxide film electrode

摘要

Capacitive deionization (CDI) is a promising candidate for the removal of nitrate (NO3-) from water, but the concentrated waste water inevitably produced in the electrode regeneration process would cause secondary pollution. In the present study, a Pd/NiAl-LMO film electrode was successfully prepared and used as an innovative NO3- electro-sorption/reduction electrode. Metallic Pd nanoparticles were uniformly doped into NiAl-LMO nanosheets, which created a loose porous nanostructure for NO3- electro-sorption and enabled catalytic activity for NO3- electro-reduction. Doping Pd nanoparticles into NiAl-LMO improved electron transport in the film electrode. The Pd/NiAl-LMO film electrode possessed larger specific capacitance and lower ion diffusion resistance than the pristine NiAl-LMO electrode. NO3- was electro-adsorbed by the Pd/NiAl-LMO electrode with concomitant reconstruction of the original hydrotalcite structure by the intercalation of NO3-, then the adsorbed NO3- was electro-reduced to N-2 by atomic H* during the electrode regeneration process. Our study provides not only a novel CDI electrode but also a new concept for a CDI process to achieve a more environmentally friendly outcome.