Solubility of Phosphates, Rates of Solution of Calcium Phosphates in Phosphoric Acid Solutions

Huffman, E. O.; Cate, W. E.; Deming, M. E.; Elmore, Kelly L.

doi:10.1021/jf60074a001

Cited by 45 publications

(24 citation statements)

References 15 publications

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“…Similar curves of the degree of conversion were observed by Huffman et al (1957) and similar curves of CaO contents of the filtrate were observed by van der Sluis et al (1987). If phosphate ore is digested by phosphoric acid, the following reactions may take place (Elmore and Farr, 1940 …”

Section: Po and Cao Contents Of The 9 W 2 5 P N Fraction Leach Solusupporting

confidence: 88%

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Exploration of mesoporous structure of tunisian raw and acid‐leached phosphate ore particles

1997

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Rock phosphate fractions were examined for their porous structure by nitrogen adsorption. The pore size distribution and the shape of pores does not seem to depend on the particle size. The specific surface area values present two regions, one above and one below that of the particles with 125 pm diameter. Particles of a given size were leached with dilute phosphoric acid (1.5 mass% P,O,) at 25°C. It was observed that there is a widening of the initial pores during leaching. The particles collected at the initial period of the reaction are pitted and those collected at the final period are disintegrated.On a examine la structure poreuse de fractions de phosphate de roche par adsorption de I'azote. La distribution de la taille des pores et la forme des pores ne semblent pas dependre de la taille des particules. Les valeurs de surface specifique presentent deux regions, I'une au-dessus et I'autre en-dessous de celle des particules d'un diametre de 125 pm. Les particules d'une taille donnee ont ete lessivees a l'acide phosphorique dilue ( 1 3 % de P,O, en masse) a 25°C. On a observe un elargissement des pores initiales lors du lessivage. Les particules collectees au debut de la reaction sont corrod& et les particules collectees a la fin desintegrees.

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Section: Po and Cao Contents Of The 9 W 2 5 P N Fraction Leach Solusupporting

confidence: 88%

“…, the maximums reached by X and (%CaO)d are about 60%, while that of (%P205)d is about 35%. Similar curves of the degree of conversion were observed byHuffman et al (1957) and similar curves of CaO contents of the filtrate were observed by van der Sluis et al(1987). Mass ratio CaO/P,O, and pH in the leach solutions vs. time.…”

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confidence: 88%

Exploration of mesoporous structure of tunisian raw and acid‐leached phosphate ore particles

1997

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“…This is usually observed when a system is controlled by a chemical reaction and not by diffusionnal phenomena which involve low values. According to Huffman et al (1957), when the rate of dissolution is controlled by the chemical reaction between the solid and liquid, microscopic roughness and porosity are important.…”

Section: T-150'cmentioning

confidence: 99%

The dissolution kinetics of sand as function of particle size

1998

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The initial dissolution rate of sand into sodium hydroxide solution (12.5 mol/L) over a wide range of temperatures (1 50 to 220°C) and pressures (0.47 to 2.29 MPa) has been determined. A semi-empirical equation was found to fit the dissolution data obtained at different temperatures and at different particle sizes. The influence of temperature on the reaction extent led to the activation energy of the dissolution, E, = 74.41 kJ/mol. Six samples of sieved silica having narrow particle size distribution 38-40, 100-125, 212-200, 400-500 and 850-1000 pn were reacted with 12.5 mol/L sodium hydroxide solution at 220°C. The effect of particle size, i.e., surface area of the grains, on the initial rate of dissolution (denoted vo) has been described by an empirical equation. Evidence is given here showing that the general assumption of the simple proportionality between the rate of reaction and the exposed surface of solid is not always confirmed.On a determine la vitesse de dissolution initiale du sable dans une solution d'hydroxyde de sodium (12,5 mol/L) pour une vaste gamme de temperatures (de 150 a 220°C) et de pressions (de 0,47 a 2,29 Mpa). On a trouve qu'une equation semi-empirique calait les donnees de dissolution obtenues A diffkrentes temperatures et tailles de particules. L'influence de la temperature sur la conversion a permis d'etablir I'energie d'activation de la distillation, E, = 74,41 kJ/mol. On a fait reagir six echantillons de silice tamisee ayant des distributions de tailles des particules etroites, de 38-10, 100-145, 21 2-200,400-500 et 850-1000 pn, avec une solution d'hydroxyde de sodium de 12,5 mol/L a 220°C. L'effet de la taille des particules, soit la surface specifique des grains, sur la vitesse de dissolution (appelke vo), est decrit par une equation empirique. On a la preuve ici que l'hypothese generale de la proportionnalitk simple entre la vitesse de reaction et la surface de solide exposee ne se confirme pas toujours.

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“…Various types of calcium phosphate cornpounds have different Ca/P ratios ranging from 2.0 to 0.5. While calcium phosphate with higher Ca/P ratios are precipitated in alkaline environment and those with lower Ca/P ratios are precipitated in acid environment, OCP is produced in neutral solution (Brown WE et aL, 1962;Huffman EO et al, 1957).…”

Section: Discussionmentioning

confidence: 99%

Morphological Character of Crystalline Components Present in Saiga Horn

Hashiguchi

Hashimoto

Akao

2001

Okajimas Folia Anatomica Japonica

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Summary: The purpose of this study was to investigate the ultrastructure of saiga-antelope (Saiga tatarica) horn for proposing the mechanism of the initial mineralization. Horn is derived from horny tooth of Cyclostomata. The minerals in saiga horn were identified crystallographically using electron microscopy and X-ray diffraction techniques. Soft X-ray photographs revealed the degree of the mineralization pattern. However, the number of rings did not indicate the age of saiga.Mineral deposites were observed among well banded keratin fibers and composed of powder like crystals. This deposited crystals were found by the X-ray diffraction method to be octacalcium phospate (OCP) by comparing these periodic lattice fringes to JCPDS card data The chemical formula of OCP is Ca8H2(PO4)6 5H2O. Evidences for the presence of OCP in mature hard tissues have never been obtained. This phenomenon described here may be characteristic of saiga horn because we have found no reports on this type of OCP mineralization in any other animal species. It is possible that OCP is the precursor in the initial mineralization step, indicating in a nucleation of mineral on the keratin fibers.

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Solubility of Phosphates, Rates of Solution of Calcium Phosphates in Phosphoric Acid Solutions

Cited by 45 publications

References 15 publications

Exploration of mesoporous structure of tunisian raw and acid‐leached phosphate ore particles

Exploration of mesoporous structure of tunisian raw and acid‐leached phosphate ore particles

The dissolution kinetics of sand as function of particle size

Morphological Character of Crystalline Components Present in Saiga Horn

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