Adsorption of copper by aminopropyl functionalized mesoporous delta manganese dioxide from aqueous solution

A novel adsorbent, named aminopropyl functionalized mesoporous delta manganese dioxide (NH2-MnO2), was synthesized by bounding 3-aminopropyltrimethoxysilane (APTMS) onto delta manganese dioxide (δ-MnO2)surface and used as Cu(II) adsorbent in aqueous solution. The Fourier transform infrared spectroscopy (FT-IR) results verified the grafting of APTMS onto δ-MnO2. The amount of APTMS grafted onto δ-MnO2 was found to be 1.640 mmol g−1 by thermo gravimetric analysis (TGA). X-ray powder diffraction (XRD) indicated the poorly-crystalline structure of the adsorbents. The specific surface area, pore volume and Barrett–Joyner–Halenda (BJH) pore diameter of the NH2-MnO2 were 79.31 m2 g−1, 0.19 cm3 g−1 and 9.52 nm, respectively. The adsorption isotherm at 298 K could be well described by Langmuir isotherm equation. The maximum adsorption capacity of NH2-MnO2 for Cu(II) at pH 4.0 was 1.543 mmol g−1, which was higher than that of the un-functionalized δ-MnO2 (1.220 mmol g−1). The Elovich equation fitted well for the Cu(II) adsorbing process by NH2-MnO2. The process of aminopropyl functionalization enhanced the adsorbing capability of NH2-MnO2 for Cu(II).