Electro-assisted naproxen adsorption followed by its electrodegradation and simultaneous electroreactivation of the activated carbon electrode

Abstract

In this work, the adsorption of a pharmaceutical pollutant, Naproxen (NPX), on activated carbon electrodes was improved through electroadsorption treatment under anodic polarization. After that, the contaminant was electrochemically degraded favoring the reactivation of the adsorbent material. The electroadsorption tests were performed with selected anodic potentials up to 1.1 V vs. NHE. The NPX removal increased from 14.2 mg/g (32.3%), during adsorption without electric potential, to 18.3 mg/g (42.7%) and 20.3 mg/g (47.1%) at 0.7 and 1.1 V vs. NHE, respectively, at an initial NPX concentration of 10 mg/L, in 0.05 M KNO3 solutions at pH 7. The presence of NPX on the electrode was confirmed by differential pulse voltammetry. The electrochemical oxidation of NPX followed an ECE mechanism confirmed by the analysis of voltamperometric parameters. The degradation mechanism was studied at different electrolysis times whose products were extracted by solvent and analyzed by HPLC-MS. Additionally, the reuse of the electrode was studied by the analysis of its textural properties, surface chemical analysis and in a new electroadsorption process. It was observed that the reactivated electrode increased its adsorption capacity up to 38 mg NPX/g (83 %) at 0.7 V and 41 mg NPX/g (84 %) at 1.1 V.