Ultrafine calcite formed in Namsan karst cave of DPR of Korea
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ORIGINAL ARTICLE
Ultrafine calcite formed in Namsan karst cave of DPR of Korea Hyon Hwangbo1 · Hak‑Chol Sim1 · Chol‑Man Choe1 Accepted: 28 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The mineralogical characteristics of the ultrafine calcite (UFC) in the Namsan karst cave were studied. The UFC formed in the cave comes in the form of a gel with white or light yellow very fine mineral particles containing water. Chemical composition of UFC is CaO 55.62%, MgO 0.3%, S iO2 0.09%, A l2O3 0.01%, F e2O3 0.03% and ignition loss 43.78%. The minimum particle size of UFC was 0.12 μm, the maximum size was 5.25 μm, and it was characterized in that the average particle size (1.39 μm was very small and the size distribution was narrow by a result of laser particle size analysis. The pyrolysis temperature (630 ~ 900 °C) was much lower than the theoretical that of calcite. Infrared absorption curves with a wavelength of 711.8, 873.9, 1423.6 and 1797.9/cm agree very well with the curve of typical carbonate minerals. Microscopic observation showed that almost round individual particles were formed into a net shape by being formed into a chain shape. The crystal particle size of UFC by X-ray diffraction (XRD) analysis was 149.3 μm The crystal structure of UFC was in agreement with the crystal structure of the chain-like calcium carbonate produced by the synthetic method and is confirmed as a chain-like UFC not known in nature hitherto by a result of XRD. The pH of UFC was 7.3, the covering power 56.8 g/m2, and the predicted specific surface area 1989.19 m2/kg. In Namsan karst cave, the UFC were basically divided into 20 ~ 30 cm thickness on the ceiling of the cave and 30 ~ 50 cm thickness on the middle of the cave bottom sediment layer. UFC in the Namsan karst cave was very important in not only mineralogy but also resources. Keywords Karst · Ultrafine · Calcite · Calcium · Carbonates · Namsan
Introduction Calcium carbonate, CaCO3, makes up nearly 4% of Earth’s crust as one of the most abundant materials in the world. Recently, it has been found that ultrafine calcium carbonate generally has much more advantages than ordinary calcium carbonate. The new properties of UFC have attracted much research interest. Calcium carbonate, C aCO3, is one of the most commonly used fillers in many industries (e.g., plastics, rubber, papermaking and medicine etc.) due to its small particle size, less impurities, high whiteness, low oil absorption and good insulation fluidity (Rungruang et al. 2006; Sheng et al. 2004; Yang et al. 2009). Also, calcium carbonate is the main ingredient of cement industry and widely used as building material (Qian et al. 2019). Calcite is used in the * Hak‑Chol Sim [email protected] 1
Faculty of Geology, Kim Il Sung University, Ryongnam‑dong, Taesong District, Pyongyang, Democratic People’s Republic of Korea
environment as an effective remedy for toxic elements such as heavy metals (Alexandratos et al. 2007; Curti 1999; Ucurum et al. 2018). In this case, ca
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