Rational construction and understanding the effect of metal cation substitution of three novel ternary Zn-Co-Ni-LDHs from 2D to 3D and its enhanced adsorption properties for MO.

The layered double hydroxides (LDHs) have attracted attention in the water treatment field. In this paper, three novel ternary Zn-Co-Ni-LDH adsorbents were prepared successfully through rational construction from 2D to 3D using triethanolamine (TEA) as an alkali source and a structural controlling reagent by hydrothermal technique. Samples were characterized by the SEM, XRD, XPS, FTIR, BET, solid-state UV/vis spectra, and TG. Three Zn-Co-Ni-LDHs exhibited higher crystallinity and surface area which were beneficial to the adsorption for methyl orange (MO). The maximum adsorption capacity of three Zn-Co-Ni-LDH adsorbents can even reach as high as 1871.65 mg·g-1, 1799.56 mg·g-1, and 1646.44 mg·g-1 for MO, respectively, which surpass those of most previously reported LDH-based adsorbents. The pseudo-second-order kinetic equation fitted the kinetic data of adsorption, while the equilibrium adsorption isotherm data followed the Langmuir model. The adsorption mechanism, electrochemical, and the antibacterial properties of three Zn-Co-Ni-LDHs were also discussed. This results not only demonstrates that three Zn-Co-Ni-LDHs are practical interest as an efficient adsorbent for the removal of MO from dye waste water, but also provides a strategy for the rational design through three ternary Zn-Co-Ni-LDHs from 2D to 3D.