Mechanisms and Kinetics of Silica-Rich Binary Na2O-SiO2 Glass Corrosion in 100°C Water at pH=7

2007 ◽  
Vol 336-338 ◽  
pp. 1823-1826 ◽  
Author(s):  
K.G. Nickel ◽  
S. Merkel
Keyword(s):  
Dissolution Rate ◽  
Rate Constant ◽  
Edge Length ◽  
Sio2 Content ◽  
Shrinking Core Model ◽  
Water Interaction ◽  
Glass Corrosion ◽  
Shrinking Core ◽  
Dissolution Rate Constant ◽  
Kinetics Of

Sodium-rich glasses of the system Na2O-SiO2 are well known to be easily soluble in water. This is not true for silica-rich compositions. We have manufactured quenched glasses with silica contents between 65 and 80 wt.% SiO2 and followed the water interaction at 100°C by measuring mass and sample dimensions in intervals. Comparing the path of edge length, mass and volume to a general shrinking core model for cuboids we conclude that only compositions between 65 and 70 wt% SiO2 can be described well by a simple dissolution process. The logarithm of the dissolution rate constant varies linearly with the SiO2 content. At higher silica contents the mechanism changes towards leaching of sodium. We propose changing glass structures to be responsible for the change in mechanism.

Reaction kinetics of malachite in ammonium carbamate solution

2015 ◽  
Vol 69 (9) ◽  
Author(s):  
Ying-Bo Mao ◽  
Jiu-Shuai Deng ◽  
Shu-Ming Wen ◽  
Jian-Jun Fang
Keyword(s):  
Activation Energy ◽  
Particle Size ◽  
Dissolution Rate ◽  
Batch Reactor ◽  
Shrinking Core Model ◽  
Surface Chemical ◽  
Surface Chemical Reaction ◽  
Ammonium Carbamate ◽  
Shrinking Core ◽  
Kinetics Of

AbstractThe dissolution of malachite particles in ammonium carbamate (AC) solutions was investigated in a batch reactor, using the parameters of temperature, AC concentration, particle size, and stirring speed. The shrinking core model was evaluated for the dissolution rate increased by decreasing particle size and increasing the temperature and AC concentration. No important effect was observed for variations in stirring speed. Dissolution curves were evaluated in order to test shrinking core models for fluid-solid systems. The dissolution rate was determined as being controlled by surface chemical reaction. The activation energy of the leaching process was determined as 46.04 kJ mol

scholarly journals Macerals of Shengli Lignite in Inner Mongolia of China and Their Combustion Reactivity

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Ying Yue Teng ◽  
Yu Zhe Liu ◽  
Quan Sheng Liu ◽  
Chang Qing Li
Keyword(s):  
Activation Energy ◽  
Homogeneous Model ◽  
Optical Microscope ◽  
Core Model ◽  
Shrinking Core Model ◽  
Compact Structure ◽  
Shrinking Core ◽  
Combustion Reactivity ◽  
Combustion Processes ◽  
Kinetics Of

The macerals, including fusinitic coal containing 72.20% inertinite and xyloid coal containing 91.43% huminite, were separated from Shengli lignite using an optical microscope, and their combustion reactivity was examined by thermogravimetric analysis. Several combustion parameters, including ignition and burnout indices, were analyzed, and the combustion kinetics of the samples were calculated by regression. Fusinitic coal presented a porous structure, while xyloid coal presented a compact structure. The specific surface area of fusinitic coal was 2.5 times larger than that of xyloid coal, and the light-off temperature of the former was higher than that of the latter. However, the overall combustion reactivity of fusinitic coal was better than that of xyloid coal. The combustion processes of fusinitic and xyloid coals can be accurately described by both the homogeneous model and the shrinking core model. The features of xyloid coal agree with the shrinking core model when its conversion rate is 10%–90%. The activation energy of fusinitic coal during combustion can be divided into three phases, with the middle phase featuring the highest energy. The activation energy of xyloid coal is lower than that of fusinitic coal in the light-off phase, which may explain the low light-off temperature of this coal.

scholarly journals Kinetics of the dissolution of sand into alkaline solutions: application of a modified shrinking core model

2004 ◽  
Vol 71 (3-4) ◽  
pp. 435-446 ◽  
Author(s):  
A Mgaidi ◽  
F Jendoubi ◽  
D Oulahna ◽  
M El Maaoui ◽  
J.A Dodds
Keyword(s):  
Core Model ◽  
Alkaline Solutions ◽  
Shrinking Core Model ◽  
Shrinking Core ◽  
Kinetics Of

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.

Dissolution kinetics of Amazonian metakaolin in hydrochloric acid

Clay Minerals ◽  
2017 ◽  
Vol 52 (1) ◽  
pp. 75-82 ◽  
Author(s):  
Paula E.A. Lima ◽  
Rômulo S. Angélica ◽  
Roberto F. Neves
Keyword(s):  
Hydrochloric Acid ◽  
Dissolution Kinetics ◽  
Regression Coefficients ◽  
Shrinking Core Model ◽  
First Order ◽  
Constant Size ◽  
Shrinking Core ◽  
Kinetics Of Dissolution ◽  
Leaching Reaction ◽  
Kinetics Of

AbstractThe kinetics of dissolution of Amazonian metakaolin in hydrochloric acid (HCl) was studied using the ‘Shrinking Core Model’ for spherical and ‘flat plate’ particles of constant size. The Amazonian kaolin was calcined at 700°C for 2 h. The calcined samples (metakaolins) were leached in an HCl solution with 5% excess at 70, 80 and 95 ± 3°C for 3 h. Samples were collected every 15 min and subjected to Al analysis by the EDTA titrimetric method. Experimental data showed that the spherical morphology produced a better fit with respect to the regression coefficients. The activation energy of the reaction was 90.6 kJ/mol. The chemical process is a first-order leaching reaction. The results of the present study are consistent with those from previous research on this topic, which used HCl with an excess of >90%.

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