scholarly journals Dissolution kinetics of hydrated calcium aluminates (AFm-Cl) as a function of pH and at room temperature

2017 ◽  
Vol 81 (5) ◽  
pp. 1245-1259 ◽  
Author(s):  
Nicolas C. M. Marty ◽  
Sylvain Grangeon ◽  
Catherine Lerouge ◽  
Fabienne Warmont ◽  
Olivier Rozenbaum ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Room Temperature ◽  
Dissolution Kinetics ◽  
Dissolution Rates ◽  
Ph Values ◽  
Surface Areas ◽  
Calcium Aluminates ◽  
Waste Repositories ◽  
Kinetics Of ◽  
Hydrated Calcium

AbstractThe determination of reliable weathering/dissolution rates for cement phases is of fundamental importance for the modelling of the temporal evolution of both radioactive waste repositories and CO2 geological storage sites (e.g. waste matrix, plug in boreholes). Here, the dissolution kinetics of AFm-Cl (hydrated calcium aluminates containing interlayer Cl) has been studied using flow-through experiments conducted at pH values ranging from 9.2 to 13. Mineralogical (XRD) and chemical (EPMA, TEM) analyses have been performed to determine the evolution of the phases during the dissolution experiments. For pH values between 10 and 13, the dissolution of AFm-Cl is congruent (i.e. Ca/Al ratios close to 2 both for solids and outlet concentrations). In contrast, the precipitation of amorphous Al-phases and possibly amorphous mixed Al/Ca phases is observed at pH 9.2, leading to Ca/Al ratios in the outlet solutions higher than those of the initial solid. Therefore, at pH 9.2, even if Cl–/OH– exchange occurs, estimation of dissolution rate from released Cl appears to be the best proxy. Dissolution rates were normalized to the final specific surface areas (ranging from 6.1 to 35.4 m2 g−1). Dissolution rate appears to be pH-independent and therefore the far-from-equilibrium dissolution rate at room temperature is expressed as: logR(mol m–2 s–1) = –9.23 ± 0.18

Aqueous dissolution kinetics of pyrochlore, zirconolite and brannerite at 25, 50, and 75 °C

2000 ◽  
Vol 88 (9-11) ◽  
Author(s):  
S. K. Roberts ◽  
W.L. Bourcier ◽  
H.F. Shaw
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Dissolution Rate ◽  
Dissolution Kinetics ◽  
Kcal Mole ◽  
Dissolution Rates ◽  
Flow Through ◽  
Kinetics Of ◽  
Total Dissolution ◽  
Calculated Average

We measured the rates of dissolution of pyrochlore, zirconolite, and brannerite in pH-buffered solutions of pH 2, 4, 6, 8, 10, and 12 at temperatures of 25, 50, and 75 °C in flow-through reactors. The dissolution rates for all phases show a minimum near pH 8. Zirconolite dissolves the slowest of the three phases, with a slightly higher rate for pyrochlore and a much higher dissolution rate for brannerite. Brannerite dissolves as much has 30 times faster than zirconolite. The rates increase with temperature, but the magnitude of the increase varies with pH. The calculated average apparent activation energy for dissolution is 6±3 kcal/mole. Dissolution is non-stoichiometric at all pHs. Ti and Hf are released most slowly, and are often below detection limits (1 ppb for Ti, 0.2 ppb for Hf). Releases of Ca, U, Gd, and Ce appear to be stoichiometric below pH 8. At pH 8 and above only U is measurable in solution. Dissolution rates are slow under all conditions, and commonly in the range of 1-100 nm total dissolution/year (between 10

scholarly journals The initial dissolution rates of simulated UK Magnox–ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

2015 ◽  
Vol 79 (6) ◽  
pp. 1529-1542 ◽  
Author(s):  
N. Cassingham ◽  
C.L. Corkhill ◽  
D.J. Backhouse ◽  
R.J. Hand ◽  
J.V. Ryan ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Intrinsic Rate ◽  
Waste Glass ◽  
High Level Waste ◽  
Dissolution Mechanism ◽  
Dissolution Rates ◽  
Forward Rates ◽  
Glass Dissolution ◽  
High Level ◽  
Kinetics Of

AbstractThe first comprehensive assessment of the dissolution kinetics of simulant Magnox–ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (Ea), pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55 ± 3 to 83 ± 9 kJ mol–1, indicating that Magnox–THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolution mechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.

scholarly journals Kinetics of carbonate mineral dissolution in CO2-acidified brines at storage reservoir conditions

2016 ◽  
Vol 192 ◽  
pp. 545-560 ◽  
Author(s):  
Cheng Peng ◽  
Benaiah U. Anabaraonye ◽  
John P. Crawshaw ◽  
Geoffrey C. Maitland ◽  
J. P. Martin Trusler
Keyword(s):  
Kinetic Model ◽  
Carbonic Acid ◽  
Dissolution Kinetics ◽  
Carbonate Reservoir ◽  
Mineral Dissolution ◽  
Direct Reaction ◽  
Carbonate Mineral ◽  
Dissolution Rates ◽  
Saturated Water ◽  
Kinetics Of

We report experimental measurements of the dissolution rate of several carbonate minerals in CO2-saturated water or brine at temperatures between 323 K and 373 K and at pressures up to 15 MPa. The dissolution kinetics of pure calcite were studied in CO2-saturated NaCl brines with molalities of up to 5 mol kg−1. The results of these experiments were found to depend only weakly on the brine molality and to conform reasonably well with a kinetic model involving two parallel first-order reactions: one involving reactions with protons and the other involving reaction with carbonic acid. The dissolution rates of dolomite and magnesite were studied in both aqueous HCl solution and in CO2-saturated water. For these minerals, the dissolution rates could be explained by a simpler kinetic model involving only direct reaction between protons and the mineral surface. Finally, the rates of dissolution of two carbonate-reservoir analogue minerals (Ketton limestone and North-Sea chalk) in CO2-saturated water were found to follow the same kinetics as found for pure calcite. Vertical scanning interferometry was used to study the surface morphology of unreacted and reacted samples. The results of the present study may find application in reactive-flow simulations of CO2-injection into carbonate-mineral saline aquifers.

scholarly journals Dissolution of Tunisian phosphate ore by a mixture of sulfuric and phosphoric acid: Kinetics study by means of differential reaction calorimetry

2019 ◽  
Vol 55 (1) ◽  
pp. 9-19
Author(s):  
Olfa Lachkar-Zamouri ◽  
Khemaies Brahim ◽  
Faten Bennour ◽  
Ismail Khattech
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Dissolution Rate ◽  
Dissolution Kinetics ◽  
Reaction Model ◽  
Reaction Calorimetry ◽  
Phosphate Ore ◽  
Differential Reaction ◽  
Apparent Activation Energies ◽  
Kinetics Of

A mixture of phosphoric and sulfuric acid was used to investigate the dissolution kinetics of phosphate ore by Differential Reaction Calorimetry (DRC). The effect of the solid-to-iquid ratio, concentration, stirring speed, particle size and temperature of the reaction is examined. It was established that the dissolution rate increased with stirring speed and particle size. However, rising the olid-to-iquid ratio, temperature and concentration decreased the dissolution rate. It was determined that the dissolution rate fits in the first order of the pseudo-homogeneous reaction model. Two negative values of apparent activation energies were found in the range of 25 to 60?C. The experimental data were tested by graphical and statistical methods and it was found that the following models were best fitted for the experimental data and an empirical equation for the process was developed. -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (2671/T)]t. T? 40?C -ln (1 ? x) = [2,2 E-09((S/L)0.75C -0.461G0.447(SS) 0.471exp (6959/T)]t. T > 45?C

The Dissolution Kinetics of Tincal in Phosphoric Acid Solutions

2007 ◽  
Vol 5 (1) ◽  
Author(s):  
Yuksel Abali ◽  
Salih U Bayca ◽  
Ayse E Guler
Keyword(s):  
Particle Size ◽  
Phosphoric Acid ◽  
Dissolution Rate ◽  
Acid Concentration ◽  
Reaction Temperature ◽  
Dissolution Kinetics ◽  
Reaction Model ◽  
Acid Solutions ◽  
Liquid Ratio ◽  
Kinetics Of

In this study, the dissolution kinetics of tincal in phosphoric acid solutions was investigated. The effects of reaction temperature, acid concentration, solid to liquid ratio, particle size and stirring speed were determined in the experiments. The results showed that the dissolution rate increased with increasing acid concentration, reaction temperature, stirring speed and increased with decreasing particle size and solid to liquid ratio. The dissolution rate was found to be based on the first order pseudo homogenous reaction model. The activation energy of the tincal in phosphoric acid solution was determined as 42.28 kJ.mol-1.

Film dissolution kinetics of aluminium at precisely adjusted pH-values

2016 ◽  
Vol 213 (6) ◽  
pp. 1410-1416
Author(s):  
Sarah Walkner ◽  
Martina Hafner ◽  
Achim Walter Hassel
Keyword(s):  
Dissolution Kinetics ◽  
Ph Values ◽  
Kinetics Of

Dissolution kinetics of a sodium borosilicate glass in Tris buffer solutions: Impact of Tris concentration and acid (HCl/HNO3) identity

2021 ◽  
Author(s):  
Nicholas Stone-Weiss ◽  
Nicholas J Smith ◽  
Randall Yougman ◽  
Eric Pierce ◽  
Ashutosh Goel
Keyword(s):  
Regenerative Medicine ◽  
Nuclear Waste ◽  
Borosilicate Glass ◽  
Dissolution Kinetics ◽  
Sodium Borosilicate Glass ◽  
Buffer Solutions ◽  
Ph Values ◽  
Waste Immobilization ◽  
Nuclear Waste Immobilization ◽  
Kinetics Of

Understanding the corrosion behavior of glasses in near-neutral environments is crucial for many technologies including glasses for regenerative medicine and nuclear waste immobilization. To maintain consistent pH values throughout experiments...

scholarly journals Kinetic Model for Dissolution of Cement Copper in Sulfuric Acid Solutions Containing Cupric Ions

2021 ◽  
Vol 15 (3) ◽  
pp. 395-402
Author(s):  
Nizamettin Demirkıran ◽  
◽  
G. Deniz Turhan Özdemir ◽  
Keyword(s):  
Sulfuric Acid ◽  
Dissolution Rate ◽  
Copper Powder ◽  
Dissolution Kinetics ◽  
Reaction Model ◽  
Ion Concentration ◽  
Acid Solutions ◽  
Cupric Ion ◽  
Sulfuric Acid Solutions ◽  
Kinetics Of

In this paper, the dissolution kinetics of cement copper powder in sulfuric acid solutions containing cupric ions was examined. It was observed that the dissolution rate of copper increased with increasing the acid concentration, temperature, and stirring speed. It was determined that the dissolution rate of copper enhanced with increasing the cupric ion concentration up to 0.025 M. It was found that the temperature and concentration of cupric ion had more considerable effects on the dissolution of copper powder. The kinetic analysis of the process was performed, and it was observed that it fits the first order pseudo-homogenous reaction model. The activation energy was calculated to be 31.1 kJ/mol.

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