Etude cinétique et thermodynamique de la dissolution de la fluorapatite dans l’acide phosphorique

Brahim, Khemaies; Khattech, Ismail; Dubès, J.P.; Jemal, M.

doi:10.1016/j.tca.2005.06.019

Cited by 37 publications

(14 citation statements)

References 21 publications

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“…A brief look at the literature allows us to discover a value given by Brahim et al Δ H r = −172 kJ mol −1 , which is different from our value. This can be explained by the fact that the fluoroapatite studied by these authors is synthetic.…”

Section: Modelling Of the Dissolution Reactioncontrasting

confidence: 92%

Modelling of a solid dissolution in liquid with chemical reaction: Application to the attack reaction of phosphate by sulphuric acid

2014

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This paper aims at the determination of the kinetics and thermodynamics of a liquid–solid reaction: the attack reaction of the phosphate ore by sulphuric acid. This reaction, which is used industrially for the production of phosphoric acid, has two stages, the first of which consists in the dissolution of phosphate ore in the diluted phosphoric acid diluted and the second relates to the attack of the dissolved ore by sulphuric acid. The thermodynamic properties and the kinetic parameters of each reaction are determined using a calorimetric approach. The complete kinetic study of the step in dissolving the phosphate ore was conducted to develop a kinetic model involving the process of transfer kinetic liquid–solid and the chemical kinetic processes. This model takes into account the coupling between the mass and heat balance and the multitude particles' sizes of phosphate and the stirring speed. The study of the attack of monocalcium phosphate by sulphuric acid allows the evaluation of the reaction order and the values of various parameters that describe the kinetic model of the precipitation reaction. The comparison of different parameters determined with those reported in the literature shows the reliability and the relevance of the proposed methodology.

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Section: Modelling Of the Dissolution Reactioncontrasting

confidence: 92%

Modelling of a solid dissolution in liquid with chemical reaction: Application to the attack reaction of phosphate by sulphuric acid

2014

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“…The results seem to be in agreement with a homogeneous model having an order of 2 with respect to the apatite. Activation energy values were deduced as 15.8 AE 1.4, 15.5 AE 0.9, and 8.5 AE 0.5 kJ mol À1 for the 1.58, 3.05, and 5.94 wt% carbonate, respectively [22]. These values are of the same order of magnitude as that determined for pure FAP below 45 C (16 kJ mol…”

mentioning

confidence: 57%

“…Dissolution of 10-60 mg of solid in 4.5 ml acid solution is a simple phenomenon without any resulting precipitate. The drawing of the energy released as a function of the solid amount led to the molar dissolution enthalpies as À201 AE 4, À208 AE 5, and À205 AE 5 kJ mol À1 for the 1.05, 3.05, and 5.94 wt% carbonate, respectively [22]. These values are lower than that corresponding to dissolution of carbonate-free fluorapatite in the same conditions (À171 kJ mol…”

Section: Thermochemistry Of Some B-type Carbonate Hydroxyapatitesmentioning

confidence: 96%

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Jemal¹

2017

Phosphoric Acid Industry - Problems and Solutions

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The principal material in the phosphate ores is composed of calcium fluorapatite Ca 10 (PO 4 ) 6 F 2 , in which the various components have been partially substituted by magnesium, sodium, carbonate, and hydroxyl ions. These substitutions affect the stability of the material and its reactivity toward the acid attack. The present chapter reports the influence of carbonates and magnesium on these properties. Using different calorimeters, dissolution experiments of carbonated and noncarbonated Ca and Ca/Mg apatites were carried out in acid solutions leading to thermochemical quantities. The results show that substitution of carbonate for F ions in the channel (to get A-type carbonate F-apatites) results in increasing the stability of the edifice, while substitution of CO 3 for PO 4 in fluor-or hydroxyapatites (to get B-type apatites) leads to a decrease in stability. The latter phenomenon was also observed when substituting magnesium for calcium in F-apatites. The presence of the former in the apatite structure results in an increase of the speed of dissolution in acid solution that is enhanced when carbonate is also replacing phosphate groups. Dissolution mechanism of synthesized Ca/Mg F-apatites seems to be a one-step process, while dissolution of a Gafsa (TN) natural phosphate to get superphosphate fertilizer is more complex.

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“…It should be noticed that these values depend on the nature of couple of cells introduced in the device . SETARAM provides Joule effect calibration cells very different from the reaction cells, consequently it was necessary to provide the latter with electrical resistances in order to get the time constants values in the same conditions as for the chemical process (Brahim et al, 2005). Electrical resistance fixed in the reaction cell was connected to stabilized DC supplier in order to deliver a certain amount of Joule effect energy.…”

Section: Methodsmentioning

confidence: 99%

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions

Jemal¹

2011

Application of Thermodynamics to Biological and Materials Science

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Etude cinétique et thermodynamique de la dissolution de la fluorapatite dans l’acide phosphorique

Cited by 37 publications

References 21 publications

Modelling of a solid dissolution in liquid with chemical reaction: Application to the attack reaction of phosphate by sulphuric acid

Modelling of a solid dissolution in liquid with chemical reaction: Application to the attack reaction of phosphate by sulphuric acid

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions (II)

Thermochemistry and Kinetics of the Reactions of Apatite Phosphates with Acid Solutions

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