Efficient removal of levofloxacin by iron (II) phthalocyanine/g-C3N4 activated peroxymonosulfate under high salinity conditions: Role of high-valent iron-oxo species

Abstract

Efficient and selective removal of organic contaminants using traditional radical-dominated Advanced Oxidation Processes (AOPs) in complex environmental matrices is challenging, especially under high salinity conditions. This study proposes an alternative approach using iron (II) phthalocyanine-supported g-C3N4 composite (FePc/CN) as a peroxymonosulfate (PMS) activator to efficiently remove organic contaminants. The FePc/CN-PMS process was selective towards the elimination of various organic contaminants, and those compounds with lower ionization potential value can be effectively degraded after reaction for 10 min. Results from radical quenching experiments, electron spin resonance (ESR), and PMSO chemical probe indicated that the dominant active species in the FePc/CN-PMS process are high-valent iron-oxo species (FeIVO2+), rather than the long-recognized SO4•− and •OH radical. A total of 22 intermediate products resulting from the degradation of levofloxacin (LVF) were identified by LC-MS. Additionally, two degradation pathways of LVF were proposed, with the piperazine ring of LVF being the primary site of degradation. The 5%FePc/CN-PMS system demonstrates resistance to ubiquitous inorganic anions and dissolved organic matter (DOM) in an aquatic environment, enabling efficient removal of (LVF) even under high salinity conditions. Furthermore, the 5%FePc/CN catalyst exhibits good chemical stability and reusability, making it a viable option for practical water remediation.