Transformation of bisphenol AF and bisphenol S by manganese dioxide and effect of iodide.

In this work, transformation of bisphenol A (BPA) alternatives bisphenol AF (BPAF) and bisphenol S (BPS) by manganese dioxide (MnO) and the effect of iodide (I) during these processes were investigated in comparison with BPA for the first time. These three bisphenols showed appreciable reactivity towards MnO with the half-lives of their loss following the order of BPA < BPAF < BPS under similar conditions, and a higher transformation efficiency was generally obtained at a lower pH. The presence of I apparently accelerated the transformation of BPAF and BPS by MnO at pH ≤ 7 but negligibly affected BPA transformation over the pH range of 5-9. This discrepancy could be well explained by the relative contribution of hypoiodous acid (HOI) in situ formed from I oxidation by MnO. Polymers, hydroxylated derivatives, and bond-cleavage products were detected from BPAF and BPS treated by MnO, where a series of reactions of BPAF/BPS radicals formed from one-electron oxidation of BPAF/BPS were likely involved, similar to the case of BPA reported in literature. A group of iodinated aromatic products were additionally identified from BPAF/BPS treated by MnO in the presence of I (e.g., iodinated BPAF/BPS and iodinated BPAF/BPS dimers), and they could be further transformed. This study suggests that naturally occurring manganese oxides play a significant role in the attenuation of bisphenols released into the environment and the presence of I can display a great effect on their transformation.