Kralj Damir, Kontrec Jasminka, Brecević Ljerka, Falini Giuseppe, Nöthig-Laslo Vesna
Laboratory for Precipitation Processes, Division of Materials Chemistry, Ruder Bosković Institute, P.O. Box 180, HR-10002 Zagreb, Croatia.
Chemistry. 2004 Apr 2;10(7):1647-56. doi: 10.1002/chem.200305313.
Calcium carbonate was precipitated from calcium hydroxide and carbonic acid solutions at 25 degrees C, with and without addition of different magnesium (MgSO(4), Mg(NO(3))(2) and MgCl(2)) and sodium salts (Na(2)SO(4), NaNO(3) and NaCl) of identical anions, in order to study the mode of incorporation of magnesium and inorganic anions and their effect on the morphology of calcite crystals over a range of initial reactant concentrations and limited c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios. The morphology, crystal size distribution, composition, structure, and specific surface area of the precipitated crystals, as well as the mode of cation and anion incorporation into the calcite crystal lattice, were studied by a combination of optical and scanning electron microscopy (SEM), electronic counting, a multiple BET method, thermogravimetry, FT-IR spectroscopy, X-ray diffraction (XRD), and electron paramagnetic resonance (EPR) spectroscopy. In the systems of high initial relative supersaturation, precipitation of an amorphous precursor phase preceded the formation of calcite, whereas in those of lower supersaturation calcite was the first and only polymorphic modification of calcium carbonate that appeared in the system. The magnesium content in calcite increased with the magnesium concentration in solution and was correlated with the type of magnesium salt used. Mg incorporation caused the formation of crystals elongated along the calcite c axis and, in some cases, the appearance of new [011] faces. Polycrystalline aggregates were formed when the c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios in solution were increased. Addition of sulfate ions, alone, caused formation of spherical calcite polycrystalline aggregates.
在25℃下，从氢氧化钙和碳酸溶液中沉淀碳酸钙，分别添加和不添加具有相同阴离子的不同镁盐（硫酸镁、硝酸镁和氯化镁）及钠盐（硫酸钠、硝酸钠和氯化钠），以研究在一系列初始反应物浓度和有限的c(i)(Mg(2+))/c(i)(Ca(2+))摩尔比范围内，镁和无机阴离子的掺入方式及其对方解石晶体形态的影响。通过光学显微镜和扫描电子显微镜（SEM）、电子计数、多点BET法、热重分析法、傅里叶变换红外光谱（FT-IR）、X射线衍射（XRD）以及电子顺磁共振（EPR）光谱等方法，研究了沉淀晶体的形态、晶体尺寸分布、组成、结构和比表面积，以及阳离子和阴离子掺入方解石晶格的方式。在高初始相对过饱和度体系中，无定形前驱相的沉淀先于方解石的形成，而在较低过饱和度体系中，方解石是体系中出现的第一个也是唯一的碳酸钙多晶型变体。方解石中的镁含量随溶液中镁浓度的增加而增加，且与所用镁盐的类型相关。镁的掺入导致晶体沿方解石c轴拉长，在某些情况下，还会出现新的[011]面。当溶液中的c(i)(Mg(2+))/c(i)(Ca(2+))摩尔比增加时，会形成多晶聚集体。单独添加硫酸根离子会导致形成球形方解石多晶聚集体。
