Electrochemical Degradation of Acetaminophen in the Presence of Different Redox Mediator Systems

This study focuses on the electrochemical degradation of acetaminophen (AP) in the presence of individual redox mediators. The oxidation peaks of Fe(II), Ag(I), and sulfate were detected on a Windsor boron-dopped diamond (BDD) electrode in 1 M Na2SO4. The AP degradation performance using a single mediator was in the following order: Ce(IV) (from Ce(SO4)2) > Fe(III) (from Fe(NO3)3 or FeCl3) > Co(II) (from C0Cl2) ≈ Ag(I) (from AgNO3). p-BQ due to AP degradation was observed in 1 M Na2SO4 in the presence of Ce(IV) and Fe(III), while the former exhibited more and faster p-benzoquinone (p-BQ) generation than the latter. In the presence of individual mediators in 1 M Na2SO4 or NaNO3, the performance of electrochemical AP degradation, p-BQ removal, and TOC mineralization on a Diachem BDD anode occurred in the following order: Fe(III) > Ce(IV) > Fe(II) ≈ Co(II) > Ag(I), but the performance decreased when replacing Na2SO4 with NaNO3 as the electrolyte. The Cl2/Cl- redox mediator could also enhance AP degradation and TOC mineralization. The apparent pseudo first-order rate constants for AP electrochemical degradation in these solutions ranged from 2.92×10-4-4.34x10-2 1/s. An Fe(III) dosage of 100 ppm (Fe(III)/AP mole ratio = 2.7) at 0.25 A/cm2 is suggested for this electrochemical process although Fe(III) dosage in the range of 50-500 ppm could be considered. Fe(III) has good potential for use in the elctrochemical advanced oxidation process (EAOP) to significantly improve organic pollutant degradation performance.