From naturally low-grade palygorskite to hybrid silicate adsorbent for efficient capture of Cu(II) ions

A new eco-friendly hybrid Mg, Al-silicate adsorbent with superior adsorption properties for Cu(II) was prepared by a one-step hydrothermal process using earth-abundant low-grade palygorskite (PAL) as the starting materials and non-toxic sodium carbonate as the assistant. The structural characterizations by scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), BET adsorption-desorption isotherms and Zeta potential analyses confirm that part of rod-like PAL crystals were in-situ transformed as smectite sheets, and the hybrid silicate adsorbents with rod/sheet transition formulation were formed. Under the action of alkaline, some inert Si-O-Si(or M) bonds were broken as -Si-O- groups, which not only make the adsorbent having extremely negative surface charge (-46.4 mV), but also strengthen the chelating and holding capability of the adsorbent to Cu(II). The silicate adsorbent shows high adsorption capacity of 229.9 mg/g for Cu(II), which can capture 98.95% of Cu(II) from 200 mg/L of Cu(II) solution at the dosage of 2.6 g/L (only 64.5% for raw PAL). The intensified electrostatic attraction, ion-exchange, and chemical association of Si-O- surface groups with Cu(II) primarily contribute to the improved capture capability for Cu(II). (C) 2016 Elsevier B.V. All rights reserved.