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 2O 5–23.7%Na 2O–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.