Mg2+调控低温环境下单水方解石的合成

Synthesis of monohydrocalcite regulated by Mg2+ in low temperature environment

在4℃的低温条件下,通过模拟纳木错湖水中主要离子种类,控制反应体系中的Mg/Ca摩尔比,探究纳木错单水方解石(MHC)的无机成因,并利用X-射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和电感耦合等离子体发射光谱(ICP-OES)对实验沉淀产物进行了分析。结果表明,单水方解石是通过无定形碳酸钙(ACC)转化而来的,且单水方解石的形成和稳定受溶液中的Mg^2+调控。当反应溶液中Mg/Ca<2时,生成方解石和镁方解石;当反应溶液中Mg/Ca>2时,单水方解石生成,并且在溶液中的存在时间随着Mg/Ca摩尔比的增加而增加。Mg/Ca=2时,单水方解石在溶液中仅存在48 h,随后转化为文石和少量镁方解石。单水方解石形成过程中Mg^2+的作用主要是抑制方解石成核和生长,使单水方解石能够在溶液中形成并稳定存在。此结果为纳木错单水方解石无机成因提供一定的研究基础。

At low temperature of 4℃,the inorganic origin of monohydrocalcite(MHC)in Lake Nam Co was investigated by simulating the mainly ionic species and controlling the Mg/Ca ratio in the reaction system.The experimental result indicates that MHC is transformed from amorphous calcium carbonate(ACC),and the formation and stability of MHC are regulated by Mg^2+in the reaction solution.When Mg/Ca ratio<2 in the reaction solution,calcite and magnesian calcite are formed,and when Mg/Ca ratio>2 in the solution,MHC is formed,and the existence time in the solution increases with the Mg/Ca ratio.In the case of Mg/Ca ratio being 2,MHC exists in the solution for 48 h,then it transforms to aragonite and a small amount of magnesian calcite.The effect of Mg^2+in the formation of MHC lies mainly in inhibiting the nucleation of calcite,so that MHC can be formed and stable in the solution.The results could provide a certain basis for the study of inorganic origin of the MHC in Lake Nam Co.