Combined direct and indirect electroxidation of urea containing water

Abstract

The direct oxidation of urea at high electrode potentials over platinized titanium electrodes in sulphate media generates a high amount of nitrates, representing an environmental problem. Coupling direct and indirect oxidation (using chloride salt), the total amount of generated nitrates can be lowered due to competition between anodic generation of chlorine and nitrates. A qualitative description of the influence of applied current density (ranging from 0.5 to 30 A m -2 ) and the nitrogen-to-chlorine ratio N/Cl (ranging from 0.5 to 3 by weight) on the distribution of urea electroxidation by-products was obtained. In a highly acidic environment, a decrease in nitrate concentration was observed when operating at relatively high current densities, which suggests the occurrence of a complex heterogeneous reaction involving nitrates and yielding mainly molecular nitrogen.

Strategies for designing more efficient electrocatalysts towards the urea oxidation reaction

“…72 Since NaCl is one of the main components in real urine, urea oxidation in neutral NaCl medium was also investigated before. 73,74 For neutral UOR performed in NaCl electrolyte, Cl − is first oxidized to Cl 2 , and then the obtained Cl 2 is disproportionated to produce HClO and Cl − . Lastly, urea is oxidized by HClO to generate CO 2 and N 2 , while HClO is reduced back to Cl − .…”

Nanostructured β−NiS Catalyst for Enhanced and Stable Electro−oxidation of Urea

“…Therefore, developing efficient electrocatalysts to promote the reaction rate is the major focus in this field. The catalytic performance of Ag [7], Ru−TiO 2 [8], Ti/Pt [9], Pt−Ir [10], IrO 2 [11], and Ta 2 O 5 −IrO 2 [12] have been investigated. However, the scarcity and high cost of these catalysts limits their practical application on a large scale.…”

Mixed-Metal Semiconductor Anodes for Electrochemical Water Splitting and Reactive Chlorine Species Generation: Implications for Electrochemical Wastewater Treatment

“…Upon hydrolysis, urea forms NH 3 and CO 2 , eventually leading to the formation of chloramines, NHCl 2 , NH 2 Cl, and NCl 3 . Urea decomposition and subsequent chlorination using mixed metal oxide anodes [35][36][37] has been reported. Urea degradation using the alternative Ti-IrTa-TiO 2 and Ti-IrTa-NaTaO 3 :La anodes has been investigated as part of this study.…”