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Despite the widespread presence of hydrogen peroxide (H2O2) in surface water and groundwater systems, little is known about the impact of environmental levels of H2O2 on the redox activity of minerals. Here we demonstrate that environmental concentrations of H2O2 can alter the reactivity of birnessite-type manganese oxide, an earth-abundant functional material, and decrease its oxidative activity in natural systems across a wide range of pH values (4–8). The H2O2-induced reductive dissolution generates Mn(II) that will re-bind to MnO2 surfaces, thereby affecting the surface charge of MnO2. Competition of Bisphenol A (BPA), used as a target compound here, and Mn(II) to interact with reactive surface sites may cause suppression of the oxidative ability of MnO2. This suppressive effect becomes more effective in the presence of oxyanions such as phosphate or silicate at concentrations comparable to those encountered in natural waters. Unlike nitrate, adsorption of phosphate or silicate onto birnessite increased in the presence of Mn(II) added or generated through H2O2-induced reduction of MnO2. This suggests that naturally occurring anions and H2O2 may have synergetic effects on the reactivity of birnessite-type manganese oxide at a range of environmentally relevant H2O2 amounts. As layered structure manganese oxides play a key role in the global carbon cycle as well as pollutant dynamics, the impact of environmental levels of hydrogen peroxide (H2O2/MnO2 molar ratio ≤ 0.3) should be considered in environmental fate and transport models. [ABSTRACT FROM AUTHOR]

In this paper, the degradation of three endocrine-disrupting chemicals (EDCs): bisphenol A (BPA), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) by manganite (γ-MnOOH) activated peroxymonosulfate (PMS) was investigated. Preliminary optimisation experiments showed that complete degradation of the three EDCs was achieved after 30 min of reaction using 0.1 g L -1 of γ-MnOOH and 2 mM of PMS. The degradation rate constants were determined to be 0.20, 0.22 and 0.15 min -1 for BPA, E2 and EE2, respectively. Combining radical scavenging approaches, Electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) analyses, we revealed for the first time that about 40% of EDCs degradation can be attributed to heterogeneous electron transfer reaction involving freshly generated Mn(IV), and 60% to sulfate radical degradation pathway. The influence of various inorganic ions on the γ-MnOOH/PMS system indicated that removal efficiency was slightly affected by chloride and carbonate ions, while nitrate and nitrite ions had negligible impacts. The application of γ-MnOOH/PMS system in real sewage treatment plant water (STPW) showed that degradation rate constants of EDCs decreased to 0.035-0.048 min -1 and complete degradation of the three EDCs after 45 min. This study provides new insights into the reactivity of combined γ-MnOOH and PMS, and opens new ways for the application of Mn-bearing species in wastewater treatment technologies., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Despite the widespread presence of hydrogen peroxide (H 2 O 2 ) in surface water and groundwater systems, little is known about the impact of environmental levels of H 2 O 2 on the redox activity of minerals. Here we demonstrate that environmental concentrations of H 2 O 2 can alter the reactivity of birnessite-type manganese oxide, an earth-abundant functional material, and decrease its oxidative activity in natural systems across a wide range of pH values (4-8). The H 2 O 2 -induced reductive dissolution generates Mn(II) that will re-bind to MnO 2 surfaces, thereby affecting the surface charge of MnO 2 . Competition of Bisphenol A (BPA), used as a target compound here, and Mn(II) to interact with reactive surface sites may cause suppression of the oxidative ability of MnO 2 . This suppressive effect becomes more effective in the presence of oxyanions such as phosphate or silicate at concentrations comparable to those encountered in natural waters. Unlike nitrate, adsorption of phosphate or silicate onto birnessite increased in the presence of Mn(II) added or generated through H 2 O 2 -induced reduction of MnO 2 . This suggests that naturally occurring anions and H 2 O 2 may have synergetic effects on the reactivity of birnessite-type manganese oxide at a range of environmentally relevant H 2 O 2 amounts. As layered structure manganese oxides play a key role in the global carbon cycle as well as pollutant dynamics, the impact of environmental levels of hydrogen peroxide (H 2 O 2 /MnO 2 molar ratio ≤ 0.3) should be considered in environmental fate and transport models.