Electrochemical oxidation of sulfadiazine with titanium suboxide mesh anode

Abstract

Pharmaceutical wastewater needs to be treated properly before it can be discharged due to the presence of high-concentration antibiotic pollutants. Electrochemical oxidation is a promising process for decentralized treatment of pharmaceutical wastewater. In this study, electrochemical oxidation of a typical antibiotic, i. e. sulfadiazine (SDZ), was investigated by using titanium suboxide mesh (TiSOM) anode. The results showed that the 60 min electrolysis could achieve almost 100% removal of SDZ based on 0.05 mol L−1 Na2SO4, pH = 6.33, and current density of 10 mA cm−2. Under these conditions, the abatement of SDZ proceeded through indirect OH-mediated oxidation rather than direct electron transfer reaction, indicated by cyclic voltammetry (CV) and electron spin resonance (ESR) measurement. The TiSOM anode exhibited a high oxygen evolution potential (2.2 V vs standard hydrogen electrode, SHE) for OH formation and long-term stability in treatment of real pharmaceutical wastewater. The mesh structure of TiSOM anode enabled a large electrochemically active surface area (ECSA, 2517.3 cm2) derived from electrochemical impedance spectroscopy (EIS) measurement, and an improved mass transfer from bulk electrolyte to the anode under flow-through operation. This makes the TiSOM anode more advantageous than flat-plate anode. The degradation pathway of SDZ was underlined on a qualitative basis by using ion chromatography, ultra performance liquid chromatography-mass spectrometry/mass spectrometry (UPLC-MS/MS) and density functional theory (DFT) calculation. This study provides an effective manner for electrochemical treatment of pharmaceutical wastewater by using a mesh-structured TiSO anode material.