Preparation of amino-silane and thiosemicarbazide modified graphene oxide composite for high uptake adsorption of Hg(II) and Pb(II)

Seeking new modification adsorbents of graphene oxide with high uptake for some heavy metal ions is still the current hot-pot in adsorption technique. An amino-silanized and thiosemicarbazide modified graphene oxide adsorbent (TSCGO) was synthesized by silanized and crosslinking reaction of graphene oxide. The structure, morphology and thermostability of TSCGO were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and BET methods. The characteristic results verified that TSCGO was successfully acquired. The adsorption experiments of TSCGO for Hg2+, Pb2+, Cd2+, Zn2+ and Cu2+ showed that TSCGO owned higher uptake for Hg2+ and Pb2+ than the other ions. Main factors affecting adsorption of TSCGO for Hg2+ and Pb2+ were analyzed. The adsorption kinetics was studied using pseudo-first-order, pseudo-second-order, Elovich, Boyd, Weber and Morris models. The adsorption followed the pseudo-second-order kinetic and Weber and Morris intraparticle diffusion models. The adsorption isotherms were fitted using Langmuir, Freundlich, Temkin, Redlich-Peterson and Hill models. The best isothermal models should be Hill model for Hg2+ and Redlich-Peterson model for Pb2+. The maximum uptakes of Hg2+ and Pb2+ obtained from the Hill model were 933.2 and 890.4 mg g−1, respectively, which were much higher than those of some reported adsorbents from the Langmuir model. The adsorption of TSCGO for Hg2+ and Pb2+ was an endothermic and spontaneous chemical process. TSCGO could be effectively regenerated with EDTA. Hence, TSCGO would be a promising adsorbent for removal of Hg2+ and Pb2+ from wastewaters.