The sepiolite/Poly(vinylimidazole) (sepiolite/PVI) composite was prepared by in situ polymerization of vinyl imidazole (VIM) and sepiolite, which was not modified. Fourier Transform Infrared (FTIR) analysis, X-ray diffraction (XRD) spectra, Scanning Electron Microscopy (SEM) images and Differential Scanning Calorimetry (DSC) exhibited that sepiolite/PVI composite was successfully produced. The theoretical maximum adsorption capacity was calculated to be 345.3 mg g(-1) (concentration range of 100-1000 mg L-1) in Hg(II) solution at pH 6.5 at 298 K. The adsorption kinetics and isotherms were also investigated for the adsorption process. The adsorption isotherms data were well fitted to the Langmuir model for the adsorption of Hg(II) onto sepiolite/PVI. The thermodynamic parameters (Delta G', Delta H degrees, and Delta S degrees) were calculated which the composite could be considered as a spontaneous, endothermic and mainly physical adsorption process. The equilibrium parameter (R-L) indicated that sepiolite/PVI composite was useful for Hg(II) removal from aqueous solutions. (C) 2016 Elsevier Ltd. All rights reserved.