Pd–O2 interaction and singlet oxygen formation in a novel reactive electrochemical membrane for ultrafast sulfamethoxazole oxidation

Abstract

In this study, a novel reactive electrochemical membrane (REM) made of Pd-loaded porous Ti was prepared to achieve ultrafast and efficient oxidation of trace antibiotics sulfamethoxazole (SMX) under anodic polarization. At a current density of 0.5 mA/cm2, the percentage removal of SMX by the REM was 96.3% in flow-through mode, with the energy cost (i.e., the electrical energy per order of removal, 1.34 Wh/m3) being much lower than the flow-by mode (125.76 Wh/m3) under the same operating condition. Quenching experiments and electron spin resonance spectra demonstrated that singlet oxygen (1O2) was the main reactive oxygen species in the REM system, playing a vital role in SMX degradation. Results of this study indicated that 1O2 was mainly generated on the anode via Pd–O2 interaction that directly activated oxygen, rather than the evolution of 1O2 precursors (e.g., O2− and H2O2). The constantly high electrochemical removal of SMX (88.5–91.9%) from actual surface water demonstrated that the matrix effect on the process performance was minimal in realistic applications, highlighting this novel REM to be a viable way to remove trace organic contaminants from surface water.