However, the dissolution rate constant (kD) is greater at the presence of BSA association (Table ). This result may be associated with mixing entropy effect. It has been suggested that soluble Mn (more likely Mn(II) species) can decrease the oxidative reactivity of glyphosate , and phenolic contaminants at the surface of Mn(IV) oxides. This occurs because (i) Mn(II) occupy active sites when sorbed, and (ii) Mn(II) can lower the redox potential of the system. As shown by quantitative XPS analysis (Table ), increases in the Mn(II) fraction at the K-birnessite surface indicate reduced Mn(II) was re-adsorbed, as suggested by previous work. This process may led to surface passivation. Furthermore, the adsorption of by-products such as Pi and AMPA may inhibit the reaction. These interactions suggest Mn(II) species, either in solution or at the surface, can modulate contaminant transformation, affecting the persistence and breakdown of agrochemicals like glyphosate in soil environments.