Sorption of divalent Fe, Co, Ni, and mixed-valent Fe into mesoporous silica grafted with an aminopropyl group, and their adsorption properties

Abstract

A reflux process was carried out for hybridization of aminopropyl-grafted mesoporous silica and metal cations at 110 and 140°C. For the sample hybridized with Fe²⁺, Co²⁺ and Ni²⁺, magnetite, Co₂(OH)₃Cl, and Ni₂(OH)₂CO₃·4H₂O particles of approx. 5-30 nm in diameter were formed. The amount of metal compounds was approx. 9-12 mol%. These compounds formed a porous aggregate on the outer surface of the mesoporous silica particles. For the hybrid with Fe²⁺ and Fe³⁺, magnetite approx. 3 nm in diameter formed not only on the outer surface but also within the mesopores derived from the mesoporous silica. The amount of magnetite achieved approx. 30 mol%. This hybrid shows an O₂ adsorption property three times as high as the other samples. These results demonstrate that nanoscale magnetite shows significant O₂ adsorption competence at room temperature.