The reaction characteristics of calcium carbonates (calcite, aragonite and vaterite) with Pb
2+ ions in aqueous solutions containing various counter-anions (CH
3COO
-, NO
3-and Cl
-) have been investigated by a normal bath method at 25°C.
It was found that the fixation of Pb
2+ ions using calcium carbonates did not proceed by an ion-exchange reaction but by dissolution and recrystallization mechanism, and the reaction characteristics depended on kind of counter-anions. Namely, Pb
2+ ions in Pb (CH
3COO)
2 and Pb (NO
3)
2 aqueous solutions were fixed as PbCO
3, while those in PbCl
2 aqueous solution were done as PbCO
3, Pb
3 (CO
3)
2 (OH)
2 and unknown compounds. These were considered to be ascribed to the different variation in pH values during the reactions. The influence of H+ ions on these characteristics was further examined. The results showed that Pb
2+ ions in PbCl
2 aqueous solution at pH=5.0 and 4.5 controlled by HCl were immobilized as PbCO
3, Pb
2 (CO
3) Cl
2 and unknown compounds by calcium carbonates.
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