文石与方解石在含Cu^(2+)溶液中的界面溶解—再沉淀

Interfacial dissolution-reprecipitation of aragonite and calcite in Cu^(2+)-bearing solutions

碳酸钙与重金属离子之间特定的界面相互作用,控制着重金属离子在环境中的固定和转化。然而,文石和方解石(两种最常见的碳酸钙同质多像矿物)与重金属离子的这种特定界面作用有何异同还不得而知。本研究采用X射线衍射仪(XRD),原位扫描探针显微镜(SPM)、X射线光电子能谱仪(XPS)和透射电子显微镜(TEM),对比考察了文石和方解石在含Cu^(2+)溶液中的界面溶解–再沉淀反应。结果表明:(1)文石(110)与方解石(10.4)面在10 mmol/L Cu(NO_(3))_(2)溶液中溶解后,表面均生成了≡Ca–OH物种,但前者的物种含量低于后者;(2)文石与方解石粉末在10 mmol/L CuCl_(2)、Cu(NO_(3))_(2)和CuSO_(4)溶液中发生溶解–再沉淀,均产生了孔雀石矿物;(3)文石与方解石粉末在10 mmol/L CuSO_(4)溶液中溶解后形成CaSO_(4)(aq)离子对,诱导了硬石膏的形成,说明在含SO^(2−)_(4)体系中,CaSO_(4)(aq)离子对是调控碳酸钙溶解进程的关键因素。本研究不仅加深了对文石和方解石晶面“构–效”关系的认识,还有助于理解Cu^(2+)在含不同类型阴离子和碳酸钙的环境中的迁移和固定。

Specific interfacial interactions between calcium carbonate and heavy metal ions control the immobilization and transformation of heavy metal ions in the environment.However,it is not clear whether aragonite and calcite,which are two of the most common calcium carbonate polymorphs,have different or similar specific interfacial interactions with heavy metal ions.In this study,the interfacial dissolution-reprecipitation of aragonite and calcite in Cu^(2+)-bearing solutions was investigated using X-ray diffractometry(XRD),in situ scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),and transmission electron microscopy(TEM).The results demonstrated that(1)after dissolving in 10 mmol/L Cu(NO_(3))_(2) solution,the≡Ca-OH species is formed on both aragonite(110)and calcite(10.4)surfaces,with the species content in the former being lower than that in the latter;(2)the dissolution-reprecipitation of both aragonite and calcite powders in 10 mmol/L CuCl_(2),Cu(NO_(3))_(2),and CuSO_(4) solutions forms the malachite mineral;(3)the dissolution of aragonite and calcite powders in 10 mmol/L CuSO_(4) solution generates the CaSO_(4)(aq)ion pairs and induces the formation of anhydrite,suggesting that the CaSO_(4)(aq)ion pairs are critical factors controlling the dissolution process of calcium carbonate in the SO_(4)^(2-) system.This study not only improves the understanding of the“structure-activity”relationship between aragonite and calcite crystal faces but also helps clarify the migration and immobilization mechanism of Cu^(2+)in an environment containing different types of anions and calcium carbonate.