Department of Mineralogy and Petrology, University of Granada , Fuentenueva s/n, 18071 Granada, Spain.
Environ Sci Technol. 2013 Oct 1;47(19):11342-9. doi: 10.1021/es402061c. Epub 2013 Sep 11.
The dissolution and carbonation of portlandite (Ca(OH)2) single crystals was studied by a combination of in situ Atomic Force Microscopy, Scanning Electron Microscopy, and two-dimensional X-ray diffraction. The dissolution of portlandite {0001} surfaces in water proceeds by the formation and expansion of pseudohexagonal etch pits, with edges parallel to ⟨100⟩ directions. Etch pits on {010} surfaces are elongated along ⟨001⟩, with edges parallel to ⟨101⟩. The interaction between carbonate-bearing solutions and portlandite results in the dissolution of the substrate coupled with the precipitation of thick islands of CaCO3 that appear oriented on the portlandite substrate. Ex situ carbonation of portlandite in contact with air results in the formation of pseudomorphs that fully preserve the external shape of the original portlandite single crystals. Our observations suggest that portlandite carbonation in contact with air and carbonate-bearing solutions occurs by a similar mechanism, i.e. coupled dissolution-precipitation. Calcite grows epitaxially on {0001} portlandite surfaces with the following orientation: ⟨001⟩Cc∥ ⟨001⟩Port. Apparently, no porosity is generated during the reaction, which progresses through the formation of fractures. Our results are of relevance to many processes in which the carbonation of portlandite takes place, such as CO2 capture and storage or the carbonation of cementitious materials.
通过原位原子力显微镜、扫描电子显微镜和二维 X 射线衍射的组合，研究了单水氢氧化钙（Ca(OH)2）的溶解和碳化过程。在水中，单水氢氧化钙 {0001} 表面的溶解是通过形成和扩展伪六边形腐蚀坑来进行的，腐蚀坑的边缘平行于 ⟨100⟩方向。{010} 表面上的腐蚀坑沿 ⟨001⟩方向拉长，边缘平行于 ⟨101⟩。含碳酸盐溶液与单水氢氧化钙的相互作用导致基质的溶解，同时沉淀出厚的碳酸钙岛，这些岛在单水氢氧化钙基质上呈现出取向。与空气接触的单水氢氧化钙的异位碳化导致形成完全保留原始单水氢氧化钙单晶外部形状的伪晶。我们的观察表明，与空气和含碳酸盐溶液接触的单水氢氧化钙碳化是通过类似的机制发生的，即溶解-沉淀耦合。方解石在 {0001} 单水氢氧化钙表面外延生长，其取向为： ⟨001⟩Cc∥ ⟨001⟩Port。显然，在反应过程中没有产生孔隙，反应通过形成裂缝进行。我们的结果与许多发生单水氢氧化钙碳化的过程有关，例如二氧化碳捕集和封存或胶凝材料的碳化。
