Layer-by-layer assembly of layered double hydroxide/histidine/δ-MnO2 nanosheets: Synthesis, characterization, and applications

Abstract

In this work, layered double hydroxide (LDH) nanosheets, manganese dioxide (δ-MnO2) nanosheets, and amino acid as organic molecules were selected as the building blocks for the fabrication of organic-inorganic nanohybrids. Layer-by-layer LDH/histidine/MnO2 (LDH/His/MnO2) nanohybrids were synthesized by self-assembly between oppositely charged 2D nanosheets of LDH and δ-MnO2 nanosheets in presence of zwitterionic histidine biomolecules. Single-layer LDH and δ-MnO2 nanosheets were prepared by exfoliation of highly crystalline MgAl-LDH and bulk MnO2, respectively. To investigate the efficiency of the prepared structure, LDH/His/MnO2 was used for removal of heavy metal cations of Pb(II) and oxyanions of As(V) from aqueous solutions. The enormous capacities for Pb(II) (584.8 mg g−1) and As(V) (632.9 mg g−1) and very high distribution coefficients (Kd) of 7.2 × 104 mL g−1 for Pb(II) and 9.2 × 104 mL g−1 for As(V) clearly demonstrate the performance of the proposed strategy for the layer-by-layer synthesis of LDH/His/MnO2 materials. The present findings clearly show that the layer-by-layer assembly between inorganic 2D nanosheets and organic molecules is quite effective to improving the simultaneous removal of heavy metal ion Pb(II) and oxyanion of As(V).