Electro-catalytic oxidation of artificial human urine by using BDD and IrO2 electrodes

• Comparative studies on BDD and IrO2 electrodes for urine oxidation were conducted.
• The electrode properties have a high relation with the oxidation processes.
• Urine can be completely oxidized by OH radicals on the non-active BDD electrode.
• Highly toxic substances were generated in solution on the active IrO2 electrode.

Galvanostatic anodic oxidation of artificial human urine (AHU) was carried out by using boron doped diamond (BDD) and IrO2 electrodes respectively. It was found that organic compounds in urine could be almost completely mineralized in a few hours and ammonia may be oxidized into N2 by the electro-catalytic process. However, the oxidation processes were highly dependent on the electrode materials. On the non-active BDD electrode complete oxidation occurred, and the final oxidation products of inorganic ions, including ClO4− and NO3−, were formed. Whereas on the active IrO2 electrode, the final products generated and left in solution were highly toxic substances, including N2H4 and NO2−, because the oxidizing activity on the IrO2 electrode surface is relatively low. The pH values during the degradation process were monitored and the corresponding degradation mechanisms and pathways on both electrodes are proposed based upon the measured inorganic intermediates.

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