Electrochemical oxidation of losartan on a BDD electrode: Influence of cathodes and electrolytes on the degradation kinetics and pathways

In this work, the influence of supporting electrolytes (sodium sulfate and sodium chloride) on the electrochemical oxidation of the antihypertensive drug losartan (LOS) was studied under different operating conditions such as current density (4.1–12.5 mA cm⁻²), electrolyte concentration (0.05–0.5 M), initial pollutant concentration (250–1000 μg L⁻¹) and solution pH. The role of cathodes on the removal of LOS has been investigated using five different cathodes with carbonaceous cathodes showing better LOS removal. The effect of matrix composition has been studied using simulated water spiked with various constituents and real water matrices such as bottled water (BW) and wastewater (WW). The removal of LOS was pronounced while using a chloride electrolyte as compared to the sulfate electrolyte. The apparent rate constant increased on adding persulfate (PS) up to concentrations of 150 mg L⁻¹ and decreased in the presence of bicarbonates and organic matter. The transformation products (TPs) formed during the electrochemical oxidation depended on the supporting electrolyte and two common TPs were identified in both electrolytes with a total of 4 TPs identified in the chloride medium and 7 TPs in the sulfate medium. Degradation pathways for LOS in both electrolytes have also been proposed.