方解石(1014)晶面在含重金属溶液中的生长及新生长面的溶解

Growth of Calcite Crystal Face(1014)in Solutions Containing Heavy Metals and Subsequent Dissolution of the Newly Grown Crystal Face

溶液中的金属离子对方解石的生长和溶解均有影响,但关于方解石中固有的杂质离子对其溶解的影响还了解甚少。本研究利用原位原子力显微镜(AFM)考察了室温下方解石(1014)晶面在含Mn^(2+)及含Cd^(2+)溶液中的生长过程,并对其新生长面直接进行原位溶解观察。实验表明,溶液中的Mn^(2+)和Cd^(2+)可参与方解石的生长,分别形成(Ca,Mn)CO3固溶体和(Ca,Cd)CO3固溶体。新生成的含Mn、Cd方解石的溶解速率仅为纯方解石的14.3%~60.3%,说明晶体中的Mn和Cd可抑制方解石的溶解。因此方解石生长阶段可通过在(1014)晶面形成含重金属固溶体从而固定Mn和Cd,由于新生长的固溶体溶解速率小于纯方解石,从而延缓Mn和Cd的迁移,并降低其环境污染的风险。

Metal ions in aqueous solution could influence the growth and dissolution of calcite.However,the effects of inherent impurity ions in calcite on its dissolution are poorly understood at present.In this study,we have investigated the growth process of calcite crystal face(1014)in Mn/Cd-bearing aqueous solutions at room temperature,and then observed the dissolution of the newly grown surface by using the in-situ time-lapse atomic force microscopy(AFM).The results show that Mn^(2+)and Cd^(2+)in the aqueous solutions were involved in the growth of calcite in forms of respective solid-solutions of(Ca,Mn)CO3 and(Ca,Cd)CO3.The dissolution rate of the newly grown Mn/Cd-bearing calcite is only 14.3%~60.3%of that for pure calcite,indicating that Mn and Cd ions in crystal lattice of calcite could inhibit its dissolution.Therefore,Mn and Cd could be immobilized in growing calcite by the formation of(Ca,Mn)CO3/(Ca,Cd)CO3 solid-solutions during the growth of calcite(1014)surface.Due to the dissolution rate of newly grown heavy metal-bearing solid-solution is less than that of pure calcite,the migration of Mn and Cd ions in solutions could be retarded.Thus,the risk of environmental pollution caused by heavy metal-bearing solutions could be reduced.