Highly efficient and fast co-removal of heavy metal ions and oxyanions with zeolite@layered double hydroxides core-shell heterostructure

Heavy metal ions and toxic oxyanions contamination in water samples is a serious risk to the public health and other life forms on earth. In recent years, collective efforts have been channeled into removing the heavy metal ions and oxyanions from aqueous samples. Here, we synthesized Core–shell ZSM-5 zeolite@ layered double hydroxides (ZSM-5@LDH) via a simple in situ coprecipitation method. The structures of the sorbent was investigated using X-ray diffraction, scanning electron microscopy, Fourier transform infrared, Brunauer-Emmett-Teller, Barret-Joyner-Halenderm and transmission electron microscope. ZSM-5@LDH was used for the simultaneous removal of heavy metal ions (Pb(II), Zn(II), Cd(II) and Cu(II)) and oxyanions (As(V), Cr(VI), Se(VI)) from aqueous solutions. Three-dimensional ZSM-5@LDH showed promising selectivity for removing Pb(II) and As(V). The equilibrium data fitted the Langmuir sorption isotherm well, and the maximum capacity of Pb(II) and As(V) onto ZSM-5@LDH were 546.25 and 411.41 mg g−1, respectively, which shows an outstanding adsorption capacity comparable to other adsorbents. The pseudo-second-order model describes the adsorption behavior towards the ions of Pb(II) and As(V) well, indicating a chemisorption process. The very high distribution coefficient (Kd) values for Pb (II) and As (V) (4.07× 104 and 8.0 × 106 mL g-1, respectively), using a V/m ratio of 2000 mL g-1, place the ZSM-5@LDH at the top of materials known for such removal. As a result, this study indicates that the ZSM-5@LDH may be an ideal material for the selective removal of Pb (II) and As (V).