RESUMEN
A highly active and selective electrode is essential in electrochemical denitrification. Although the emerging Cu-based electrode has attracted intensive attentions in electrochemical NO3- reduction, the issues such as restricted activity and selectivity are still unresolved. In our work, a binder-free composite electrode (Cu3P/CF) was first prepared by direct growth of copper phosphide on copper foam and then applied to electrochemical NO3- reduction. The resulting Cu3P/CF electrode showed enhanced electrochemical performance for NO3- reduction (84.3%) with high N2 selectivity (98.01%) under the initial conditions of 1500 mg L-1 Cl- and 50 mg N L-1 NO3-. The cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) demonstrated that electrochemical NO3- reduction was achieved through electron transfer between NO3- and Cu0 originated from CF. The in-situ grown Cu3P served as the bifunctional catalyst, the electron mediator or bridge to facilitate the electron-transfer for NO3- reduction and the stable catalyst to produce atomic H* toward NO2- conversion. Meanwhile, the Cu3P/CF remained its electrocatalytic activity even after eight cyclic experiments. Finally, a 2-stage treatment strategy, pre-oxidation by Ir-Ru/Ti anode and post-reduction by Cu3P/CF cathode, was designed for electrochemical chemical oxygen demand (COD) and total nitrogen (TN) removal from real wastewater.
Asunto(s)
Cobre , Nitratos , Electrodos , Nitrógeno , Óxidos de NitrógenoRESUMEN
In this work, a novel method for complete Cr(â ¥) removal was achieved in a single-chamber cell with titanium (Ti) as anode via simultaneous indirect electro-reduction of Cr(â ¥) and in-situ precipitation of Cr(â ¢). The Cr(â ¥) and total Cr removal, and electric energy consumption were optimized as a function of electrochemical reactor, current density, initial Cr(â ¥) and chloride (Cl-) concentration, and initial solution pH. The maximum Cr(â ¥) and total Cr removal efficiency reached 80.5 and 79.4% respectively within 12 h at current density of 10 mA cm-2 as initial Cr(â ¥) concentration was 0.078 mM. Decreasing the initial solution pH was beneficial to Cr(â ¥) reduction, but Cr(â ¢) precipitation was inhibited, resulting in the poor total Cr removal. The suitable Cl- concentration guaranteed sufficient reducing agents (Ti3+ and Ti2+) for Cr(â ¥) removal. The reaction mechanism demonstrated that Ti anode could be corroded to produce Ti3+ and Ti2+, which provided the electrons for reduction of Cr(â ¥) to Cr(â ¢). Simultaneously, the solid products (Ti2O(6x-y-z+52)Cl2yCr2x(OH)2z(s)) were in-situ formed and precipitated from the solution due to the continuous generation of hydroxyl ion (OH-) from cathode. This study might provide a new electrochemical method with non-precious metal as the electrode for complete Cr(â ¥) removal from aqueous media.