IMMOBILIZATION OF PB2-CEMENT - THE METHOD USING LEAD HYDROXYAPATITE( WITH ORDINARY PORT LAND)

Lead hydroxyapatite was synthesized hydrothermally at 150 degrees C un der saturated vapor pressure for 1h. This apatite or lead nitrate solu tion was added to ordinary portland cement (OPC) in order to immobiliz e the Pb2+. In this paper, the effect of Pb2+ on the hydration of OPC, mechanical properties of OPC pastes and the leaching characteristic o f Pb2+ from hardened pastes were investigated. An addition of lead hyd roxyapatite did not affect the hydration of OPC significantly, while t hat of lead nitrate solution affected the hydration of OPC. Therefore, a larger amount of Pb2+ could be immobilized by cement paste with lea d hydroxyapatite than that with lead nitrate solution. The strength fo r hardened paste with lead hydroxyapatite was larger than that with ni trate solution. According to the leaching test for pastes, the apparen t diffusion coefficient of Pb2+ in the paste with lead hydroxyapatite was smaller than that of Pb2+ in the paste with addition of lead nitri te solution.