A method of removing metal ions from silicate glasses for recycling by liquid-phase deposition

A method of removing metal ions from silicate glasses for recycling was stu died. This method utilizes a liquid-phase deposition (LPD) technique using a hydrofluosilicic acid (H2SiF6) aqueous solution supersaturated with silic a. Silicate glass powder prepared from a glass bottle was dissolved in aque ous hydrofluoric acid (HF) solution. The fluorinated silicon oxide (SiOF) s eparated from the H2SiF6, and then an LPD-SiOF gel was formed in the supers aturated H2SiF6 aqueous solution. Almost all ratios of metals to silicon (S i) were reduced by at least one order of magnitude. The LPD-SiOF powder for med by drying the LPD-SiOF gel at 23 degreesC showed a different chemical b onding structure than that of the initial silicate glass powder. The LPD-Si OF powder showed a cluster structure of spheres 1-2 mum in diameter. A poss ible mechanism for removal of the non-Si primary component metal oxides and other impurity metal ions is proposed. The features of this method and a p ossible application for recycled silica are also discussed. (C) 2001 Elsevi er Science B.V. All rights reserved.