Impacts of ammonium ion on triclinic birnessites towards the transformation of As(III)

Understanding the role of manganese oxides in retaining harmful metals: Insights into oxidation and adsorption mechanisms at microstructure level

“…These birnessites possess numerous octahedral vacancies (up to 12 %) in the layers, primarily composed of Mn(IV) with a smaller amount of Mn(III), while the interlayer ions consist mainly of H + , Mn 3+ , and Mn 2+ [ 33 , 84 ]. Alkaline birnessites are typically created by fully oxidizing Mn(OH) 2 with KMnO 4 in a weakly alkaline medium, and triclinic birnessites are generally synthesized in alkaline conditions [ [92] , [93] , [94] ]. Alkaline birnessites have a higher Mn(III) content in their layers than acidic birnessites, and their interlayers consist of Mn 3+ and Mn 2+ , with fewer H + [ 84 ].…”