New insights into the quantiffcation of Fe(IV) using methyl phenyl sulfoxide (PMSO) as probe in the iron-based heterogeneous catalyst activated persulfate process.

Ferryl ions (Fe(IV)) are often thought to play an important role in iron-based advanced oxidation processes (AOPs), and their presence is typically inferred through the unique pathway of methyl phenyl sulfoxide (PMSO) conversion to methyl phenyl sulfone (PMSO). Here, we first employed probe method by degrading the mixed system containing PMSO, benzoic acid (BA), nitrobenzene (NB) to analyze the steady-state concentration of Fe (IV) in the iron-based heterogeneous persulfate reaction system. In addition, studies were conducted on the direct oxidation of PMSO by different oxidants under different pH conditions, and the results showed that peroxymonosulfate (PMS), sodium hypochlorite (NaClO) and sodium periodate (PI) can directly oxidize PMSO and convert it into PMSO. Furthermore, the influence of different types of iron salts and biomass on the prepared iron-biochar (Fe-BC) for the activation of persulfate on degradation of PMSO and the formation of PMSO was also investigated. This study may provide new insights into the use of PMSO as a probe for the analysis of Fe(IV) in heterogeneous reaction systems.