Silicate digestion with fructose under mild conditions

Abstract

Treatment of silica gel or silicate mineral with an aqueous solution of the weak base triethylenetetraamine and the sugar fructose results in partial dispersion into particles smaller than 450 nm under conditions of ambient pressure and mild heating (60–100 °C) in times less than 1 h. Redeposition occurs at longer times. The final material has 13–31% higher surface area and 17–18% lower D50 (50% of the accumulated weight percentage is smaller than this particle size). Dissolution or decrystallization of some of the aluminosilicate phase is indicated by X-ray diffraction for the Berea sandstone. The proposed mechanism involves deprotonation at the anomeric hydroxyl, followed by attack on the solid silicate centers by fructose to form a pentacoordinate silicon complex. The stereochemistry of fructose then allows a planar diolato ring to form containing C2 and C3 of fructose and a second position on pentacoordinate silicon. The reaction results in displacement of a portion of the silicate matrix. Reformation of Si–O–Si bonds gives rise to redeposition. An equilibrium between dissolution and redeposition results in the final reworked material with reduced particle size.