Facile and simple synthesis of triethylenetetramine-modified mesoporous silica adsorbent for removal of Cd(II)

Monodispersed porous silica microspheres (SM) were synthesized and further functionalized with amine moieties using triethylenetetramine (TETA) in order to obtain a novel adsorbent for Cd(II) elimination from aqueous media. The morphology, texture and structure of samples were characterized with the aid of Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM), energy dispersive spectroscopy (EDS), and N₂ adsorption-desorption. The adsorption efficiency was investigated based on the effect of operational parameters including pH of the solution, the dose of adsorbent, adsorption time, initial concentration of Cd(II) ions and temperature. The equilibrium, kinetics and thermodynamics of Cd(II) adsorption were also studied. The maximum adsorption capacity of amine functionalized silica microspheres (AMSM) for Cd(II) was 35.6 mg g^-1. Cd(II) adsorption onto AMSM had highest consistency with Sips and Langmuir isotherms, while adsorption kinetics was best fitted with pseudo-second order model. Thermodynamics of adsorption revealed that Cd(II) adsorption on AMSM was spontaneous, feasible and exothermic with physical interactions and pore diffusion being the dominant mechanisms in the adsorption process. Results confirmed that AMSM adsorbent has the potential to be a suitable candidate for Cd(II) removal from aqueous solutions.