Degradation of bisphenol A by ferrate(VI) oxidation: Kinetics, products and toxicity assessment

A series of batch experiments were carried out to investigate the factors influencing BPA degradation by ferrate(VI) and the reaction rate kinetics, including molar ratio of ferrate(VI) to BPA (0.1-8.0), initial solution pH (3.0-11.0) and temperature (283-323 K). Reaction pathways were proposed according to the determination of intermediate products and the toxicity variation during the BPA degradation process was evaluated by marine luminescent bacteria (Vibriofischeri). BPA degradation by ferrate(VI) was effective and rapid, with a major BPA removal happening within 3 min. With an initial BPA concentration of 4.4 μmol/L, a ferrate(VI) to BPA molar ratio of 8.0, an initial solution pH of 7.0 and a temperature 298 K, ca. 97.5% BPA removal was achieved. Twelve reaction products were identified by gas chromatography/mass spectrometry-mass spectrometry (GC/MS-MS) and two possible pathways for BPA degradation by ferrate(VI) were proposed, featuring a series of steps including dehydroxylation, cleavage of C-C bond, OH group addition, and oxidation. Unlike the rapid degradation of BPA by ferrate(VI), the elimination of toxicity exhibited a hysteresis effect and there was a rise tendency within the first 5 min, which might be caused by formation of more toxic intermediates, such as benzoquinone, hydroquinone, styrene.