Improving the removal of losartan, irbesartan and their transformation products through in situ produced hydrogen peroxide in electrochemical oxidation processes

Abstract

The degradation of losartan (LST) and irbesartan (IBT) has been studied in an electrochemical cell composed of a boron-doped diamond (BDD) anode and a carbonaceous cathode made of reticulated vitreous carbon. The in situ production of hydrogen peroxide (H2O2) was observed at the cathode modified with two types of carbon black (CB) materials; XC72 and XCmax22. The most efficient H2O2 production was attained at the cathode made with XCmax22 in a mass ratio of 1/4 to PTFE (i.e., PTFE/CB). Overall, XCmax22 outperformed XC72 producing almost twice amount of H2O2 and reaching a current efficiency up to 93 %. Furthermore, the in situ produced H2O2 significantly enhanced the electro-oxidation rate of LST and IBT achieving an almost sixfold faster removal of both compounds with 10 mg L−1 of initial concentration of each compound completely removed in 10 min. In addition, the effect of water matrix was also analyzed at low initial concentration of the compounds (500 ng L−1). The degradation of the compounds followed pseudo first order kinetics achieving complete removal of 500 ng L−1 of both compounds in 30 min. Using ultra-high performance liquid chromatography in combination with high-resolution mass spectrometry (UHPLC-HRMS), transformation products of LST and IBT were identified, degradation pathways were proposed and their toxicity was assessed. These results offer an energy- and cost-effective solution for the treatment of recalcitrant organic micropollutants while also providing a pathway for the conversion and storage of excess electrical energy in the form of chemical energy (i.e., H2O2).