Preparation and Characterization of Mesoporous Magnesium Silicate Gels and Application for Cobalt(II) Removal

Two new mesoporous magnesium silicate gel adsorbents, MgO x 2SiO2 and MgO x 6SiO2, have been successfully prepared by hydrothermal method. The synthetic factors including reaction pH, temperature, time and calcination temperature were studied. The aiming products were characterized by N2 adsorption/desorption isotherms, FT-IR spectroscopy and Scanning Electron Microscopy (SEM). The adsorption behaviors for cobalt ions were also systematically investigated. The results show that the reaction pH was the decisive factor for Si/Mg mole ratios. The special surface areas are 534.29 m2 x g(-1) for MgO x 2SiO2 and 181.61 m2 x g(-1) for MgO x 6SiO2, respectively. The maximum adsorption capacities of MgO x 2SiO2 and MgO x 6SiO2 for cobalt ions are 135.5 and 52.5 mg x g(-1). Furthermore, the experimental data are well described by pseudo-second order adsorption and Langmuir isotherm models. The experiment would afford one excellent adsorbent for solving the wastewater pollution and also providing metal cobalt for modern industry including new energy car.