Highly efficient and selectivity removal of heavy metal ions using single-layer Na_xK_yMnO₂ nanosheet: A combination of experimental and theoretical study

Manganese oxides (MnO₂) are widely applied in heavy metal ions removal due to their low-cost, environmental-friendly and biocompatibility. However, the adsorption capacity of MnO₂ need to be further improved to satisfy the demand of practical application. Herein, a highly dispersed single layer Na_xK_yMnO₂ nanosheet was synthesized by a facile wet-chemical method with sodium dodecyl sulfonate as surfactant. The high surface specific area, excellent dispersibility and abundant oxygen vacancies endowed Na_xK_yMnO₂ nanosheets with potential in heavy metal ions adsorption. The adsorption experiments results showed that Na_xK_yMnO₂ nanosheets possessed high efficiency and selectivity towards lead ion (Pb²⁺) with a high adsorption capacity of 2091.8 μmol g⁻¹. The Na_xK_yMnO₂ also showed an excellent reusability with the removal rate of 95.4% for Pb²⁺ even after five cycles. Moreover, both the theoretical calculation and experimental data illustrated that the single layer Na_xK_yMnO₂ nanosheets possess high selectivity to Pb²⁺ adsorption.