Efficient adsorption of Cu(II) and Cr(VI) metal ions by Schiff base modified SBA-15

SBA-15 was functionalized with amine (–NH2) and 3-methoxy salicylaldehyde (3-MS) to form a mesoporous silica with Schiff base modified surface (3-MS–SBA-15). The materials were characterized and analyzed by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), Nitrogen adsorption-desorption (BET), and X-ray diffraction (XRD) spectroscopy. The removal of Cu(II) and Cr(VI) metal ions onto 3-MS-SBA-15 was then studied from their aqueous solutions in order to investigate and optimize the effect of contact time, solution pH, adsorbent dose and temperature in batch system. The equilibrium data were analyzed using the Tempkin, Dubinin- Radashkovich, Langmuir and Freundlich isotherms. Freundlich and Langmuir isotherms were well fitted for Cu(II) and Cr(VI) adsorption process, respectively. The kinetics analyses showed that the total adsorption process was completely fitted with the pseudo-second-order kinetics model. The adsorption depended strongly on temperature, as the adsorption capacity decreased for Cu(II) while increased for Cr(VI) by increasing the temperature of the system, indicating the exothermic and spontaneous nature for Cu(II) and the endothermic and spontaneous nature for Cr(VI).