Application of Different Waveforms of Pulsed Current in the Classical Electro-Cocatalytic Process for Effective Removal of Sulfamethoxazole: Oxidation Mechanisms

Abstract

In this study, sulfamethoxazole (SMX) was applied as the model pollutant to assess the performance of pulsed current (PC) waveforms in the decontamination efficiency of the PC/peroxymonosulfate (PMS)/Fe(III) process and to investigate underlying oxidation mechanisms. Among the various waveforms tested, the sinusoidal wave (SIN), combined with the Dimensionally Stable Anode (DSA) electrode, demonstrated superior degradation performance, with the order being SIN > ramp > square > direct current (DC). The operational conditions for the SIN/PMS/Fe(III) system were optimized to an initial pH of 3, a voltage of 6 V, 0.6 mmol/L of Fe3+, 1.0 mmol/L of PMS, and a frequency of 1 kHz. The results of quenching and probe experiments confirmed the generation of abundant reactive radicals such as •OH, SO4•−, O2•−, Fe(IV), and 1O2 in the SIN/PMS/Fe(III) process, which collectively enhanced the degradation of SMX. Additionally, results of high-resolution mass spectrometry analysis were employed to identify the SMX oxidation byproducts, and the toxicity of SMX byproducts was evaluated. Overall, the SIN/PMS/Fe(III) process exhibits effective degradation capacity with high energy efficiency, establishing itself as an effective strategy for the practical treatment of medical wastewater.