Non-activated peroxymonosulfate oxidation of p-aminobenzoic acid in the presence of effluent organic matter

Abstract

Non-activated peroxymonosulfate (PMS) oxidation of p-aminobenzoic acid (PABA) in the presence of effluent organic matter (EfOM) from wastewater treatment plant was investigated. The reaction kinetics of PMS with PABA exhibited a strong pH dependency, which was well described by species-specific reactions. The transformation of PABA by PMS was inhibited in the presence of EfOM at pH 3.0. Moreover, the variation of EfOM during PMS oxidation processes was tracked using excitation emission matrix (EEM) combined with parallel factor analysis (PARAFAC). The results revealed that humic-like substances and proteins in EfOM consumed a fraction of PMS and thus hindered PABA degradation, which was partly attributable to phenolic compounds widely existed in EfOM. The transformation products of PABA by PMS oxidation were identified by leveraging quadruple time-of-flight (Q-TOF) mass spectrometry (MS) coupled with ultra-high performance liquid chromatography (UHPLC), and a possible reaction pathway was also proposed. Understanding the role of EfOM in PABA oxidation by PMS is essential for providing useful insights into the application of PMS in advanced treatment of secondary effluent.