Removal of lead ions from solution by phosphosilicate glass

A new technique to remove Pb(2+) ions from a solution by using a phosphosilicate glass was introduced. When the phosphosilicate glass with an invert glass composition [mol%: 44.9%SiO(2)-5.2%P(2)O(5)-23.7%Na(2)O-26.2%CaO] was reacted with the solution containing Pb(2+) ions. The glass surface turned into silica-rich layer by leaching of glass modifies, such as Na(+) and Ca(2+) ions, and the Pb(10)(PO(4))(6)(OH)(2) crystals developed on the silica-rich layer. The Pb(2+) ions were removed from the solution by precipitating this crystal on the glass surface. The Pb(2+) ion removal rate depended strongly on the pH of the solution and was the highest at pH 2.0. In the solution of pH 1, Pb(10)(PO(4))(6)(OH)(2) was not formed due to its high solubility in such a strong acid.