Amine-functionalized MCM-48 as Adsorbent of Zn2+ and Ni2+ Ions

Abstract

A compound, 3-aminopropyltrimetoxy silane, has been used to modify mesoporous silica, MCM-48. The modified silica (NH₂-MCM-48) was utilized to remove Zn²⁺ and Ni²⁺ ions from solutions. The mesoporous material was synthesized in the alkaline solution. Characterization of the unmodified materials was conducted by X-ray diffraction and FT-IR spectroscopy. The ions adsorbed on NH2-MCM-48 were studied at various pHs, contact times and initial ions concentrations. An Atomic Absorption Spectrophotometer (AAS) measured the ions content in the solution.. Pseudo-first-order and pseudo-second-order models performed the kinetic adsorption. The adsorption isotherm was examined by Langmuir and Freundlich isotherms. The result found that optimum contact time for the adsorption of Zn²⁺ ion was lower than that for Ni²⁺ ion. The adsorption followed the pseudo-second-order model with the adsorption rate of 4.56x10^-2 g mg^-1 min^-1 for Zn²⁺ ion and 7x10^-4 g mg^-1 min^-1 for Ni²⁺ ion. The optimum pH was 6 and 4 for Zn²⁺ and Ni²⁺ adsorption, respectively. The uptake of both ions from solutions by NH₂-MCM-48 fixed better the Langmuir than the Freundlich model with the adsorption capacity of 0.55 and 0.43 mmol g^-1, correspondingly. This research work provides valuable information on the interaction between the ions and the functional group of adsorbent.