Removal of trace naproxen from aqueous solution using a laboratory-scale reactive flow-through membrane electrode.

Abstract

The kinetics and mechanisms of naproxen (NPX) degradation with the concentration of 20-200 μg/L were investigated by using reactive flow-through membrane anode. The electrochemical degradation of NPX followed pseudo-first-order reaction kinetics. The kinetic rate constant (k) of 0.649 min-1 and energy consumption (EEO) of 0.744 Wh/L were found under optimal conditions with the initial NPX concentration of 50 μg/L. Higher current density benefited •OH production and NPX degradation. Faster rotational speed of pump and lower pH were in favor of electrochemical degradation of NPX, in which k and EEO were 3.9 and 0.27 times when rotational speed was increased from 100 to 600 rpm, and 4.9 and 0.21 times when pH was decreased from 11.0 to 3.0, respectively. The degradation efficiency and energy consumption were both maintained at a narrow range when the initial concentration of NPX was changed from 20 to 200 μg/L, and even under the addition of humic acid (1.0-10.0 mg/L). The major degradation pathways of NPX were demethylation and decarboxylation, followed with the further ring cleavage reactions. The flow-through membrane electrode is proved to be effective for the elimination of trace NPX from aqueous solution.