Effects of EDTA and ethanol on the morphology of CaCO3 particle

2012 ◽  
Vol 7 (6) ◽  
pp. 508
Author(s):  
Xingbo Shi ◽  
Julin Wang ◽  
Xiaoping Cai
Keyword(s):  
Caco3 Particle

Experimental Investigation of the SO2 Abatement Capacity of South African Calcium-Based Materials

2007 ◽  
Author(s):  
Zachary O. Siagi ◽  
Makame Mbarawa
Keyword(s):  
Particle Size ◽  
Dissolution Rate ◽  
South African ◽  
Efficient Operation ◽  
Shrinking Core ◽  
Caco3 Particle ◽  
Ph Stat ◽  
Kinetics Of ◽  
Different Sources ◽  
So2 Absorption

One of the most important steps in the wet limestone-gypsum flue gas desulphurization (WFGD) process is CaCO3 dissolution, which provides the dissolved alkalinity necessary for SO2 absorption. Accurately evaluating the CaCO3 dissolution rate is important in the design and efficient operation of WFGD plants. In the present work, the dissolution of limestone from different sources in South Africa has been studied in a pH-stat apparatus under conditions similar to those encountered in wet FGD processes. The influence of various parameters such as the reaction temperature (30 ≤ T ≤ 70°C), CaCO3 particle size (25 ≤ dp ≤ 63μm), solution acidity (4 ≤ pH ≤ 6), and chemical composition were studied in order to determine the kinetics of CaCO3 dissolution. The results obtained indicate that the dissolution rate increased with a decrease in particle size and an increase in temperature. The dissolution curves were evaluated in order to test the shrinking core model for fluid–solid systems. The analysis indicated that the dissolution of CaCO3 was controlled by chemical reaction, i.e. 1 − (1 − X)1/3 = kt.

scholarly journals Kinetics and mechanisms of heterogeneous reaction of NO<sub>2</sub> on CaCO<sub>3</sub> surfaces under dry and wet conditions

2010 ◽  
Vol 10 (2) ◽  
pp. 463-474 ◽  
Author(s):  
H. J. Li ◽  
T. Zhu ◽  
D. F. Zhao ◽  
Z. F. Zhang ◽  
Z. M. Chen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Heterogeneous Reaction ◽  
Adsorbed Water ◽  
Uptake Coefficient ◽  
Liquid Reaction ◽  
Dry Conditions ◽  
Caco3 Particle ◽  
Condensed Water ◽  
Diffuse Reflectance Infrared ◽  
Initial Uptake

Abstract. With increasing NO2 concentration in the troposphere, the importance of NO2 reaction with mineral dust in the atmosphere needs to be evaluated. Until now, little is known about the reaction of NO2 with CaCO3. In this study, the heterogeneous reaction of NO2 on the surface of CaCO3 particles was investigated at 296 K and NO2 concentrations between 4.58×1015 molecules cm−3 to 1.68×1016 molecules cm−3, using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) combined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), under wet and dry conditions. Nitrate formation was observed under both conditions, while nitrite was observed under wet conditions, indicating the reaction of NO2 on the CaCO3 surface produced nitrate and probably nitrous acid (HONO). Relative humidity (RH) influences both the initial uptake coefficient and the reaction mechanism. At low RH, surface −OH is formed through dissociation of the surface adsorbed water via oxygen vacancy, thus determining the reaction order. As RH increases, water starts to condense on the surface and the gas-liquid reaction of NO2 with the condensed water begins. With high enough RH (>52% in our experiment), the gas-liquid reaction of NO2 with condensed water becomes dominant, forming HNO3 and HONO. The initial uptake coefficient γ0 was determined to be (4.25±1.18)×10−9 under dry conditions and up to (6.56±0.34)×10−8 under wet conditions. These results suggest that the reaction of NO2 on CaCO3 particle is unable to compete with that of HNO3 in the atmosphere. Further studies at lower NO2 concentrations and with a more accurate assessment of the surface area for calculating the uptake coefficient of the reaction of NO2 on CaCO3 particle and to examine its importance as a source of HONO in the atmosphere are needed.

Formation of Water-in-Oil Microemulsions and Their Applications for Caco3 Particle Preparation

1989 ◽  
pp. 253-262 ◽  
Author(s):  
Kazuhiko Kandori ◽  
Kijiro Kon-no ◽  
Ayao Kitahara ◽  
Masami Fujiwara ◽  
Takamitsu Tamura
Keyword(s):  
Caco3 Particle ◽  
Particle Preparation

scholarly journals Controlling CaCO3 Particle Size with {Ca2+}:{CO32–} Ratios in Aqueous Environments

2021 ◽  
Author(s):  
Sergěj Y. M. H. Seepma ◽  
Sergio E. Ruiz-Hernandez ◽  
Gernot Nehrke ◽  
Karline Soetaert ◽  
Albert P. Philipse ◽  
...  
Keyword(s):  
Particle Size ◽  
Aqueous Environments ◽  
Caco3 Particle

scholarly journals A multi-species coccolith volume response to an anthropogenically-modified ocean

2008 ◽  
Vol 5 (4) ◽  
pp. 2923-2930
Author(s):  
P. R. Halloran ◽  
I. R. Hall ◽  
E. Colmenero-Hidalgo ◽  
R. E. M. Rickaby
Keyword(s):  
Numerical Models ◽  
Size Fraction ◽  
Distribution Data ◽  
Volume Distribution ◽  
Particle Volume ◽  
Realistic Representation ◽  
Volume Response ◽  
Caco3 Particle ◽  
Species Specific ◽  
Co2 Release

Abstract. Major questions surround the species-specific nature of coccolithophore calcification in response to rising atmospheric CO2 levels. Here we present CaCO3 particle volume distribution data from the coccolith size-fraction of a rapidly accumulating North Atlantic sediment core. These data appear to indicate that coccoliths produced by the larger coccolithophore species present at this location increase in mass in parallel with anthropogenic CO2 release. This finding has significant implications for the realistic representation of an assemblage-wide coccolithophore CO2-calcification response in numerical models.

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