Heterogeneous degradation of bisphenol A by peroxymonosulfate activated with vanadium-titanium magnetite: Performance, transformation pathways and mechanism

The vanadium-titanium magnetite (VTM) has a high comprehensive utilization value because it is an important source of iron (Fe) and other elements such as titanium (Ti) and vanadium (V). In this study, VTM was first used as a PMS activator to evaluate the degradation of bisphenol A (BPA) in the aqueous solution. First, the characteristics of VTM were analyzed via X-ray powder diffraction (XRD), energy dispersive spectrometer (EDS), Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Then, effects of several key parameters (i.e., VTM dosage (0-15 g/L), PMS dosage (0-5 mM), initial pH (3.0-11.0) and co-existing ions) on the BPA degradation were investigated systematically. Regardless of the initial pH, 50 mg/L of BPA could be degraded effectively ( >= 90%) with the fixed VTM (12 g/L) and PMS (4 mM) dosage. Besides, quenching experiments confirmed that the main free radical contributed to the BPA degradation varied with the initial pH. Also, to verify the high efficiency of VTM, two control experiments (i.e., PMS alone and VTM alone systems), reusability and practical application tests were carried out. Furthermore, ten degradation intermediates of BPA were identified via ultrahigh performance liquid chromatograph-mass spectrometry/mass spectrometry (UPLC-MS/MS). Based on the detected intermediates, the degradation pathways and degradation mechanism of BPA were proposed comprehensively. In addition, toxicity tests were performed on samples during processing. Finally, a reasonable reaction mechanism of VTM/PMS system for BPA degradation was put forward thoroughly. In brief, this study provided some new insights for the use of natural ore in the wastewater treatment and all the results suggested VTM is a cheap and efficient catalyst for PMS activation.