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The functionalization of multi-walled carbon nanotubes (MWCNTs) was achieved by reacting ethylenediamine, cyanuric chloride and sodium 2-mercaptoethanol in sequence as efficient ways to introduce amine and thiol functional groups onto the nanotube sidewalls. The synthesized amino and thiolated MWCNTs were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). A series of batch adsorption experiments were conducted to study the effect of pH, dose of adsorbent, metal concentration and temperature on Hg(II) uptake by the functionalized MWCNTs. The adsorption isotherm data were better fitted by Langmuir model, while kinetic data can be characterized by the pseudo-second-order rate kinetics. Based on the thermodynamic data of ΔH^∘, ΔS^∘ and ΔG^∘ obtained, it can be …