Transformation of bisphenol A by manganese oxide-coated sand
2013
Lin, Kunde | Peng, Yiwen | Huang, Xinwen | Ding, Jiafeng
Oxidative transformation of organic contaminants by manganese oxides was commonly investigated with pure MnO₂ suspension, which deviates from the fact that natural manganese oxides are seldom present as a pure form in the natural environment. In this study, we prepared manganese oxide-coated sand (MOCS) and evaluated its oxidative capacity using bisphenol A (BPA) as the model compound. BPA was transformed by MOCS and the reaction followed an exponential decay model. The reaction was pH dependent and followed the order of pH 4.5 > pH 5.5 > pH 6.5 > pH 7.5 > pH 8.6 > pH 9.6, indicating that acidic conditions facilitated BPA transformation while basic conditions disfavored the reaction. Coexisting metal ions exhibited inhibitory effects and followed the order of Fe³⁺ > Zn²⁺ > Cu²⁺ > Ca²⁺ > Mg²⁺ > Na⁺. Transformation of BPA by MOCS was much slower than that by pure MnO₂ suspension. However, similar transformation products were identified in both studies, suggesting the same reaction pathways. This work suggests that the reactivity of MnO₂ in the environment might be overestimated if extrapolating the result from the pure MnO₂ suspension because natural MnO₂ is mainly present as coating on the surface of soils and sediments.
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