The adsorption mechanism of Zn2+ by triclinic birnessite and the mechanism.

In this paper, the reaction mechanism for the adsorption of Zn2+ by synthetic triclinic Na-birnessite was studied by reacting synthetic triclinic Na-birnessite with Zn2+ in solution, thereby providing a theoretical basis for the purification of heavy metal ions in acid soil and water by triclinic birnessite. The adsorption effect of Zn2+ on Na-birnessite enhances with an increase in either reaction time or Na-birnessite dosage, as well as decrease of pH. Na-birnessite can effectively adsorb Zn2+ in acidic solutions without any secondary pollution, and the stronger the acidity, the better the treatment effect. In acidic conditions, H+ in solution exchanges with Na+ in the interlayer of triclinic Na-birnessite, then a small part of Zn2+ in solution exchanges with the Mn2+ produced during the triclinic-to-hexagonal phase transformation, and most of the Zn2+ forms a complex with OH- on the octahedral layer, which loses protons due to the consumption of H+ ions. Finally, Zn2+ adsorbs above and below octahedral vacancies in hexagonal birnessite in either an octahedral or tetrahedral coordination.