Use of copper plate electrode and Pd catalyst to the nitrate reduction in an electrochemical dual-chamber cell

Abstract

Nitrate is a chemical species usually present in water, lakes and rivers and in high concentration can be dangerous to the human health. In this work, palladium-coated alumina pellets associated to a copper plate electrode were tested, in an electrochemical dual-chamber cell (DCC), for the treatment of solutions containing high nitrate concentration. The tests evaluated how Pd catalyst, current density and pH have an effect on the reduction reaction and on the formation of nitrite, ammonium and gaseous compounds. It was possible to observe that the Pd catalyst has an influence on the products formed, with an increase on the gaseous compounds production. The current density plays also an important role on the treatment, considering that, by applying 1.1 mA cm−2, 59 % of nitrate reduction was observed, while with 1.5 mA cm−2 the reduction was 64 %. The highest selectivity to gaseous compounds and lower selectivity to nitrite were obtained using alumina pellets coated with 2.5 % wt. of Pd, a current density of 1.5 mA cm−2 and with pH adjustment (6.0–6.5). In these conditions, a nitrate reduction of 49 % was obtained, with a selectivity of 64 % to gaseous compounds, 1% to nitrite and 35 % to ammonium. The main novelty of this work is the reduction cell design, by the use of a dual chamber cell and with the catalyst in pellets form. This cell would be suitable for scaling-up the process.