Transformation of bisphenol AF and bisphenol S by permanganate in the absence/presence of iodide: Kinetics and products

Abstract

Recent studies have reported that permanganate (Mn(VII)) shows a good performance in treatment of phenolic compounds, and the presence of iodide (I−) may display a great impact on Mn(VII) oxidation with the formation of toxic iodinated aromatic products. In this work, transformation of bisphenol AF (BPAF) and bisphenol S (BPS) by Mn(VII) in the absence or presence of I− was studied. Mn(VII) showed considerable reactivity towards BPAF with apparent second-order rate constants (0.09–1.65 M−1s−1) higher than those of Mn(VII) with BPS (0.02–0.12 M−1s−1) reported in literature over the pH range of 5–9. The presence of I− apparently accelerated the transformation rates of BPAF and BPS by Mn(VII), and these results could be explained by the contribution of hypoiodous acid (HOI) in situ formed from Mn(VII) oxidation of I−. A kinetic model involving the competitive reactions (i.e., Mn(VII) with I− and bisphenols, HOI with Mn(VII) and bisphenols) well simulated BPAF/BPS transformation by Mn(VII) in the presence of I− under various conditions. Hydroxylated, bond-cleavage, and polymeric products were identified from BPAF/BPS oxidation by Mn(VII), and iodinated aromatic products (e.g., mono- and multi-iodinated BPAF/BPS) were additionally detected in the presence of I−. Reaction pathways involving Mn(VII) one-electron oxidation as well as HOI substitution of BPAF/BPS were proposed. Eco-toxicity analysis by ECOSAR showed that the toxicity of these products generally followed the order of polymeric and iodinated aromatic products > parent BPAF/BPS > hydroxylated products > bond-cleavage products.