Mineralization of paracetamol in aqueous medium by anodic oxidation with a boron-doped diamond electrode

Abstract

The degradation of 100 ml of solutions with paracetamol ( N-(4-hydroxyphenyl)acetamide) up to 1 g l −1 in the pH range 2.0–12.0 has been studied by anodic oxidation in a cell with a boron-doped diamond (BDD) anode and a graphite cathode, both of 3-cm 2 area, by applying a current of 100, 300 and 450 mA between 25 and 45 °C. Complete mineralization is always achieved due to the great concentration of hydroxyl radical ( OH) generated at the BDD surface, with release of NH 4 + and NO 3 - ions. The mineralization rate is pH-independent, increases with increasing applied current and temperature, but decreases when drug concentration raises from 315 mg l −1. Reversed-phase chromatography revealed a similar complex paracetamol decay in acid and alkaline media. Ion-exclusion chromatography allowed the detection of oxalic and oxamic acids as ultimate carboxylic acids. When the same solutions have been comparatively treated with a Pt anode, a quite poor mineralization is found because of the production of much lower OH concentration. Under these conditions, the degradation rate is enhanced in alkaline medium and polymerization of intermediates is favored in concentrated solutions. Paracetamol can be completely destroyed with Pt and its kinetics follows a pseudo-first-order reaction with a constant rate independent of pH.