The presence of MnO2 as a single oxide in aquatic environments is likely the exception rather than the rule. This work examines how interactions in ternary mixtures of MnO2, FeIII oxides and NOM affect the oxidative reactivity of MnO2. Adsorption studies showed that there was insignificant adsorption of the NOM including Aldrich humic acid (AHA), alginate and pyromellitic acid (PA) by MnO2, while there was high (AHA and alginate) to low (PA) adsorption by FeIII oxides. ATR-FTIR spectra showed that PA is mainly adsorbed by FeIII oxides through the formation of outer-sphere complexes. FeIII oxides by themselves predominantly inhibited the MnO2 reactivity through heteroaggregation between the positively charged FeIII oxides and the negatively charged MnO2. The reactivity of MnO2 in ternary mixtures with FeIII oxides and NOM was either inhibited or promoted as compared to that in binary mixtures with NOM. The proposed interaction mechanisms for the ternary mixtures mainly include 1) inhibited heteroaggregation with MnO2 but enhanced homoaggregation within the FeIII oxides due to the formation of oppositely charged patches within the FeIII oxides at 1 mg/L&lt;[NOM]&lt;5 mg/L, and 2) inhibited heteroaggregation between FeIII oxides and MnO2 due to the largely negatively charged surfaces for all oxides at [NOM]&gt;10 mg/L.

Oxidative reactivity of MnO2 in mixtures with FeIII oxides and/or natural organic matter (NOM)

249th National Meeting (2015)

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