沉积CaCO_3与金属离子界面反应动力学研究

Kinetic study of the interface reactions between metal ions and sediment CaCO_3

金属离子与沉积碳酸盐之间界面反应动力学模拟实验表明，由于CaCO3快速溶解和溶液pH急剧上升，大部分Pb2+、Zn2+离子与溶液中CO2-3和OH-离子反应生成白铅矿PbCO3、水白铅矿Pb3（OH）2（CO3）2，或Zn（OH）2和水锌矿Zn（OH）6（CO3）2沉淀于体相溶液中，仅有少部分Pb2+、Zn2+通过扩散与CaCO3表面发生离子交换反应。25℃时，Ph2+溶液中以白铝矿沉淀为主，Zn2+溶液中以水锌矿沉淀为主。温度上升，沉淀速率加快的同时，离子交换量也增大。然而，在25℃Ag+吸附实验中，未发现有Ag2CO3沉淀。但温度上升至50℃，溶液中Ag+离子损耗明显增加，但CaCO3对Ag+离子吸附量却减少，这意味着在体相溶液中也可能有Ag2CO3沉淀产生。

The simulation experiments on the interface reaction kinetics between the metal ions and sediment CaCO3 show that most of the divalent ion Pb2 + and Zn2+ were precipitated as phase cerussite PbCO3, hydrocerussite Pb3(OH),(CO3)2, or Zn(OH)2 and hydrozincite Zn5(OH)6(CO3), by carbonic ion CO2-3 that resulted from the dissolution of CaCO3, only few of metal ions diffused onto the CaCo3 surface to exchange with calcium atoms. At 25 ℃, the ma jor precipitated phase is cerusite in Pb2+-containing solution, meanwhile the hydrozincite is dominant precipitation phase in Zn2+-containing solution. As temperature raised, the precipitation rate increased and exchanged values increased too. In Ag+ -containing solution there was no silver carbonate precipitation found at 25℃.At 50℃, however, as adsorption capacity of ion Ag+ onto CaCO3 decreased the loss of ion Ag+ in solution was increased. This guggests that the silver carbonate precipitation may exist in solution as temperature raised.