  The ammonium cation interaction with Na-birnessite in aqueous alkaline medium
was studied. Solution and solid analysis give evidence that birnessite is not
only acting as a cationic exchanger toward NH4+. The surface analysis performed
by XPS showed that N1s spectra are characterized by the existence of two
different environments: one assignable to an interlayer NH4+ and the second to
a chemisorbed N-species. Structural and chemical transformations were observed
on birnessite with nitrogen mass balance deficit. The monitoring of NH4 +, Na+,
Mn2+, NO3- and NO2- and solid changes (average oxidation state of Mn, cation
exchange capacity, solid nitrogen content and symmetry evolution identified by
XRD and FTIR) indicate unambiguously that NH4+ reacts chemically with the
birnessite.
