Thiol-Yne Click Synthesis of Polyamide-Amine Dendritic Magnetic Halloysite Nanotubes for the Efficient Removal of Pb(II)

Heavy metals such as Pb(II) pollutions in wastewater have been a serious environmental problem. In this study, we loaded polyamide-amine (PAMAM) on the surface of magnetic halloysite nanotubes (MHNTs) via one-step thiol-yne click chemistry to obtain dendritic magnetic halloysite nanotubes (MHNTs-PAMAM) with high-density amine groups for the highly efficient adsorption of Pb(II). The synthesized MHNTs-PAMAM were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and thermogravimetric analysis (TGA), which confirmed the formed nanostructures and chemical features of MHNTs-PAMAM. And batch adsorption experiments were carried out to investigate the effect of pH and other variables on the adsorption amount. Here, TGA shows that PAMAM grafting on halloysite nanotubes (HNTs) achieves a sufficiently high graft ratio of 6.1 wt %, which ensures sufficient active adsorption sites on the surface of the composite. With the increase of the grafted PAMAM generation, the functional group density and adsorption capacity of the material also gradually increased, and the maximum adsorption capacity of the material for Pb(II) was up to 194.4 mg g(-1). The adsorption kinetics agrees well with the pseudo-second-order equations, and the equilibrium data can be described by the Langmuir isotherm (R-2 = 0.940).