Elimination of Pb2+ Ion from Aqueous Solution by Using Calcium Hydroxide Solution or Ammonium Phosphate Solution

Abstract

The elimination of Pb2+ ion from aqueous solution was performed by adding calcium hydroxide solution or ammonium phosphate solution to a solution containing Pb2+ ion. The concentration of the filtrate was measured and the data were compared with those of the ferrite formation method. In the case of Ca(OH)2 addition, the concentration of Pb2+ ion in the filtrate was affected by the Ca2+/Pb2+ ratio. The minimum concentration of 0.58mg/dm3 was obtained when the Ca2+/Pb2+ ratio was 1, where pH of the solution was 11.74. In the case of (NH4)3PO4 addition, ill-crystallized Pb-hydroxyapatite was precipitated, and the concentration of Pb2+ ion in the filtrate was 0.01mg/dm3. The well-crystallized Pb-hydroxyapatite was obtained by the hydrothermal treatment of ill-crystallized one by using solution with pH of 12 at 150°C for 1h. This Pb-hydroxyapatite has lower solubility than lead hydroxide over a wide pH range. It is concluded that the method for elimination of Pb2+ ion from aqueous solution by using calcium hydroxide or ammonium phosphate were more effective than the ferrite formation method.