Facile synthesis of 2D α-MnO₂ nanosheets for the removal of heavy metal ions

Removal of heavy metal ions (HMIs) has attracted great attentions due to the fact that they have serious effect on environment and human beings. Manganese oxide (MnO₂) was widely used as absorbent for the HMIs removal on account of its low-cost, eco-friendly and biocompatibility. The modification of morphological and structure is recognized as the effective route to improve the adsorption capacity. In this work, 2D α-MnO₂ nanosheets were synthesized by hydrothermal method with Al³⁺ additive. With the merits of high specific surface area, high dispersity in aqueous solution and abundant surface defects, 2D α-MnO₂ nanosheets exhibited excellent HMIs adsorption performance. The maximum adsorption capacity of 2D α-MnO₂ nanosheets reached 1.604 mmol g⁻¹ (Pb²⁺) and 0.813 mmol g⁻¹ (Cd²⁺), respectively and can maintain stable after five cycles. Besides, the established adsorption kinetics fitted well with pseudo-second-order adsorption kinetics model. Based on the above results, 2D α-MnO₂ is efficient for the removal of HMIs and possesses remarkable practical application potential.