Structural Transformation of MnO₂ during the Oxidation of Bisphenol A

Abstract

Bisphenol A (BPA) is an endocrine-disrupting compound widely used in the plastic industry and found in natural waters at concentrations considered harmful for aquatic life. BPA is susceptible to oxidation by Mn(III/IV) oxides, which are commonly found in near-surface environments. Here, we quantify BPA oxidation rates and the formation of its predominant product, 4-hydroxycumyl alcohol (HCA), in tandem with transformation of a synthetic, Mn(III)-rich δ-MnO. To investigate the effect of Mn oxide structural changes on BPA oxidation rate, 12 sequential additions of 80 μM BPA are performed at pH 7. During the additions, BPA oxidation rate decreases by 3 orders of magnitude, and HCA yield decreases from 40% to 3%. This is attributed to the accumulation of interlayer Mn(II/III) produced during the reaction, as observed using X-ray absorption spectroscopy, as well as additional spectroscopic and wet chemical techniques. HCA is oxidized at a rate that is 12.6 times slower than BPA and accumulates in solution. These results demonstrate that BPA degradation by environmentally relevant Mn(III/IV) oxides is inhibited by the buildup of solid-phase Mn(II/III), specifically in interlayer sites. Nevertheless, Mn oxides may limit BPA migration in near-surface environments and have potential for use in drinking and wastewater treatment.

Arsenite Depletion by Manganese Oxides: A Case Study on the Limitations of Observed First Order Rate Constants

“…Both data sets indicate that the rate constant has multiple orders of magnitude variability (10 −2 -10 −4 s −1 ) on relatively small timescales, demonstrating the importance of reporting the time range used. This order of magnitude variability in rate constant was also observed with sequential additions of bisphenol A to Mn oxide [57]. Reductive dissolution of Mn oxides by As III is characterized by structural changes, rather than simply reducing Mn IV to aqueous Mn II [56].…”

“…Comparison of oxidation rates between studies requires solid phase characterization, including, but not limited to, mineral phase fractions, chemical composition, AMON, crystallite size, and point of zero charge (PZC) [51,[53][54][55]. This is important both at the start of the experiment, and throughout the experiment, because the mineral structure changes throughout the reaction [56,57]. Characterization of environmental Mn oxides presents unique challenges, since they frequently occur as poorly crystalline, fine-grained particles or coatings on other minerals, and are often substituted with Fe [5].…”

Hydrophilic trace organic contaminants in urban stormwater: occurrence, toxicological relevance, and the need to enhance green stormwater infrastructure

“…12 Manganese oxides (MnO 2 ) are natural oxidants in soils and sediments and can enhance the removal and transformation of organic contaminants through direct oxidation, adsorption, and surface catalysis. [170][171][172] MnO 2 can oxidize a variety of hyphil-TrOCs including antibacterial agents, 173,174 sulfonamide antibiotics, 171 glyphosate, 175 steroid hormones (estrone and 17α-ethinylestradiol), 176 BPA, 177 and β-blockers (betaxolol, atenolol, and metoprolol). 178 Compared to iron oxides, manganese oxides have a higher redox potential resulting in greater oxidation possibilities for organic contaminants.…”

Predicting Kinetics of As(V) Adsorption and Desorption on Mixed Minerals of Ferrihydrite and δ‐MnO2

“…The background electrolyte was 2 mM NaNO 3 containing 3 mM MES buffer ([2‐(N‐morpholino) ethanesulfonic acid]) for pH 6.0, or containing 3 mM MOPS buffer [3‐(N‐morpholino) propanesulfonic acid] for pH 6.5 and 7.0. Both MES and MOPS did not adsorb on mineral surfaces (Balgooyen et al, 2017; Ying et al, 2012), having little interference on As(V) adsorption on both ferrihydrite and δ‐MnO 2 . Different concentrations of As(V) stock solutions were prepared by diluting a different amount of As(V) standard solution in the background electrolytes.…”