Preparation of Mg, Ca, or Sr-included mesoporous silica from glass bottle waste for recovery of rare earth metal elements

Abstract

Mesoporous silica-alkali earth (Mg, Ca, or Sr) hybrids were prepared from waste glass as a silica source. Mesoporous silica containing no alkali earth succeeded in preparing a perfect pore structure arranged hexagonally. On increasing the alkali-earth element, mesoporous structures are preserved on a small amount of the alkali-earth element as a substituent and tend to diminish with an increase in the substituent, reducing the surface area. We examined a scale-up experiment for the production of a large amount of hybrids. The scale-up system factor we proposed was relatively small, indicating relatively high production efficiency. The hybrids were also examined for the ion-exchangeability of rare-earth metals. The tendency of the amount for ion-exchange showed a positive convex tetrad effect, which means a decrease in the ionicity of the rare-earth metals during an exchange. Since XANES spectra confirm the trivalent state of each rare-earth metal in ion-exchanged hybrids, the rare-earth metals are found to exchange from the alkali-earth elements because the exchanged amount is 2/3 of the alkali-earth element leached.