Removal of Various Ions from Acid Solution by Surface Active Glass

초록

An invert type of glass, which contains less than 50 mole% of glass former, forms a thick silica-rich layer when the glass is reacted in an acidic solution. This is due to the leaching of a large amount of alkali ions out of glass surface. If some ions are present in the solution, those ions can be precipitated on the silica-rich layer to form a crystalline phase. In case of bioactive glass, the crystalline phase is hydroxyapatite, which shows a behavior of a chemical bonding to a living tissue when the glass is implated in a body. On the basis of this property of glass, this study includes an experiment to remove various ions dissolved in a solution by a surface active glass. A glass with composition of 44.9%SiO2-5.2%P2O5-23.7%Na2O-26.2%CaO (mole%) was reacted in a solution containing various ions, such as Pb, Cr, Ni, Fe, Cu, Mn ions. The reaction was carried out under the condition of various pH and various reaction time. The ions can be removed by precipitation of the crystalline phase containing those ions on the glass surface. The ion removal capacity strongly depended on the pH of the solution, that is, the capacity was the highest in a solution with a specific pH. The removal capacity also depended on the type of crystalline phases formed on the glass surface. Those phenomena are discussed in terms of a thermodynamic behavior of the formation.