PEM Electrolysis-Assisted Catalysis Combined with Photocatalytic Oxidation towards Complete Abatement of Nitrogen-Containing Contaminants in Water.

Electrolysis-assisted nitrate (NO3 - ) reduction is a promising approach for its conversion to harmless N2 from waste, ground, and drinking water due to the possible process simplicity by in-situ generation of H2 /H/H+ by water electrolysis and to the flexibility given by tunable redox potential of electrodes. This work explores the use of a polymer electrolyte membrane (PEM) electrochemical cell for electrolysis-assisted nitrate reduction using SnO2 -supported metals as the active cathode catalysts. Effects of operation modes and catalyst materials on nitrate conversion and product selectivity were studied. The major challenge of product selectivity, namely complete suppression of nitrite (NO2 - ) and ammonium (NH4 + ) ion formation, was tackled by combining with simultaneous photocatalytic oxidation to drive the overall reaction towards N2 formation.

Determination of choline and derivatives with a solid-contact ion-selective electrode based on octaamide cavitand and carbon nanotubes.

A new solid-contact ion-selective electrode has been developed for determining choline and derivatives in aqueous solutions. The backbone of this new potentiometric sensor is the conjunction of the cavitand receptor, as the molecular recognition element, and a network of non-carboxylated single-walled carbon nanotubes, acting as a solid transducer material. The octaamide cavitand, a synthetic receptor that is highly selective for biologically important trimethyl alkylammonium cations such as choline, acetylcholine or carnitine, makes the selective determination of these compounds possible for the first time. The guest-host interaction takes place in the acrylate ion-selective membrane of the solid-contact electrode. The sensor was characterized by electrochemical impedance spectroscopy and environmental scanning electron microscopy. The new electrode displays a nearly Nernstian slope (57.3+/-1.0 mV/decade) and very stable behaviour (DeltaE/Deltat=224 muVh(-1)) throughout the dynamic range (10(-5) to 10(-1)M). The limit of detection of 10(-6.4)M and the high selectivities obtained will enable choline and derivatives to be determined in biological samples. Finally, the stability of the electrical potential of the new solid-contact electrode was examined by performing current-reversal chronopotentiometry and the influence of the interfacial water film was evaluated by the potentiometric water layer test.