A novel adsorbent, named tri-amino-functionalized mesoporous delta manganese dioxide (NNN-MnO2), was synthesized by bonding trimethoxysilyl propyl diethylenetriamine onto the surface of delta manganese dioxide (δ-MnO2) and used as a Cu(II) adsorbent in aqueous solution. The graft of silane coupling agent onto δ-MnO2 was verified by Fourier transform infrared spectroscopy. The crystalline structure of the adsorbents was indicated by an X-ray powder diffractometer. The specific surface area, pore volume, and Barrett–Joyner–Halenda pore diameter of the NNN-MnO2 were 93.50 m2 g−1, 0.31 cm3 g−1, and 13.12 nm, respectively. The Elovich equation described well the Cu(II) adsorbing process and the negative values of ΔG and the positive values of ΔH and ΔS indicated a spontaneous and endothermic process. The Langmuir equation fitted well the adsorption isotherm at 298 K and the maximum adsorption capacity of NNN-MnO2 for Cu(II) at pH 4 was 87.72 mg g−1, which was higher than that of the un-functionalized δ-MnO2 (66.67 mg g−1). The graft of tri-amino-functional groups enhanced the uptake of Cu(II), and NNN-MnO2 was a promising candidate for Cu(II) removal from aqueous solution.
Synthesis and evaluation of manganese dioxide with layered structure as an adsorbent for selective removal of strontium ions from aqueous solution
