Removal process of nickel(II) by using dodecyl sulfate intercalated calcium aluminum layered double hydroxide

Calcium aluminum layered double hydroxides (LDH) modified with sodium dodecyl sulfate (SDS) (Ca/Al-DS LDH) was prepared to investigate the unique removal mechanism of metal cations by organic calcium contained LDHs. The as-prepared sample was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma atomic emission spectrometer (ICP-AES) and elemental analysis (EA). Ni(II) was selected as the target metal cation and its removal kinetics could be well described by the pseudo-second-order kinetic model (R-2 = 0.990). The maximum removal capacity of Ni(II) reached 2.45 mol/g at the LDH dosage of 0.5 g L-1. The XRD and element analysis results indicate that a new Ni/Al-DS LDH phase and CaCO3 were formed as well as a portion of Ca/Al-DS LDH remained in the final products after the removal process. Therefore, the removal of Ni(II) was contributed to the surface complexation, isomorphic substitution and sorption on the CaCO3. The pillared interlayer organic anions might help to keep the layered structure of LDH. This study revealed the multi-interaction mechanism of metal ions with Ca/Al LDH and proposed a novel strategy to generate organic intercalated LDHs by isomorphic substitution. (C) 2016 Elsevier B.V. All rights reserved.