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

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/cm 2 , 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/m 3 ) being much lower than the flow-by mode (125.76 Wh/m 3 ) under the same operating condition. Quenching experiments and electron spin resonance spectra demonstrated that singlet oxygen ( 1 O 2 ) was the main reactive oxygen species in the REM system, playing a vital role in SMX degradation. Results of this study indicated that 1 O 2 was mainly generated on the anode via Pd–O 2 interaction that directly activated oxygen, rather than the evolution of 1 O 2 precursors ( e.g ., O 2 − and H 2 O 2 ). 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.