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.
- Active chlorine
- Platinized titanium electrode