Adsorption Performance of SiO2/CPAM Composites for Aqueous Ca(II)

Silica/cationic polyacrylamide (SiO2/CPAM) composites with a dendritic structure were prepared via in situ polymerization based on silica containing vinyl groups and acrylamide monomers. The structure and surface properties of the composites were revealed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The adsorption behavior and properties of aqueous Ca(II) on the SiO2/CPAM composites were also investigated. The effect of the pH value, the initial Ca(II) concentration, adsorption time, and temperature on adsorption properties were examined. The results showed that the SiO2/CPAM composites displayed a high adsorption performance for aqueous Ca(II). The maximum adsorption capacity of the SiO2/CPAM composites for Ca(II) was 123.4 mg.g(-1) at room temperature and pH 9. The adsorption behavior was in agreement with the Langmuir isotherm model. The adsorption was an endothermic and spontaneous process. Adsorption kinetics fitted well with the pseudo-second-order model. The adsorption of Ca(II) on the SiO2/CPAM composites was mainly attributed to chemical interaction, and chelation was more significant than electrostatic interaction.