pH-dependence of solubilities of solid solutions of calcium and strontium hydroxylapatites

Narasaraju, T. S. B.; Chickerur, N. S.; Singh, Raghuvir

doi:10.1016/0022-1902(71)80093-3

Cited by 15 publications

(5 citation statements)

References 6 publications

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“…Collin [20] reported that the apatitic solid solutions had a much smaller Sr/Ca ratio than the aqueous solutions from which they were precipitated. This is in agreement with solubility measurements on solid solutions carried out by Narasaraju, Chickerur, and Singh [23], who found that strontium incorporation causes increased solubility. On the other hand, synergistic 0171-967X/79/0029-0127 $01.00 effects for fluoride and strontium are reported on calcium hydroxyapatite dissolution [24][25][26], which should indicate that the apatite phase would prefer incorporation of strontium over that of calcium.…”

Section: Introductionsupporting

confidence: 92%

Lattice parameters and cation distribution of solid solutions of calcium and strontium hydroxyapatite

1979

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Summary. Solid solutions of strontium and calcium hydroxyapatite were synthesized by solid-state reaction. Lattice parameters of these compounds were determined using two types of Guinier cameras. They vary linearly with the molar percentage of strontium hydroxyapatite. The distribution of Ca and Sr ions over the fourfold and sixfold positions in the apatite structure was determined by comparing experimental and calculated values for the intensity ratios of suitable reflections. A slight, although significant, preference of Sr for the sixfold position was found. An ideal behavior is predicted for these solid solutions.

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Section: Introductionsupporting

confidence: 92%

Lattice parameters and cation distribution of solid solutions of calcium and strontium hydroxyapatite

1979

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“…While preliminary experiments indicated the suitability of the pH range for such solubility investigation, studies on dissolution kinetics provided the optimum period of equilibration for the formation of a saturated solution of the sample. It was found to be 4 h. In order to be doubly sure about the attainment of saturation, the equilibration period was extended to 12 h, the rest of the experimental details for solubility studies being the same as those described elsewhere [19,20]. The effect of common ions on pK~p of the sample was also investigated at convenient pH values.…”

Section: Methodsmentioning

confidence: 99%

Physico-chemical aspects of calcium vanadate apatite

1986

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By appropriate modifications of existing precipitation methods, a sample of calcium vanadate apatite, Cal0(VO4)e(OH)2 was prepared at 11 0 ° C. It was characterized through X-ray, electron microscopic, infrared and thermoanalytical analyses in addition to chemical analysis. Equilibrating the sample in buffered aqueous media at 37 ° C, the solubility was measured using microanalytical techniques of Ca 2+ and VO 3-present in the saturated solutions after separating the colloidal component of the solute. Duration of equilibration for the attainment of saturation of the solution of the sample was obtained from a study on its dissolution kinetics. The pK~p of calcium vanadate apatite was found to be 1 07.09. The investigation showed that pK~p was independent of the presence of the common ions.

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“…For both apatites the amount of released phosphate was the highest for the initial pH 3. This confirms that the apatite solubility increases with decreasing pH (Chien et al 1975, Arends et al 1987, Narasaraju et al 1971, Narasaraju & Phebe 1996. The higher solubility of the HAP as compared to the FAP is caused by the difference in solubility products (K SP ) of the minerals which are equal to 10 -58.23 and 10 -59.56 , respectively (Lindsay 1979).…”

Section: Apatites Dissolutionmentioning

confidence: 72%

Aqueous cadmium removal by hydroxylapatite and fluoroapatite

Matusik¹,

Bajda²,

Manecki³

2012

geol

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Reducing the bioavailability of toxic heavy metals in groundwaters and urban soils by phosphate addition is an effective technique described in the literature. It is based on the reaction between metal ions and phosphates and results in the precipitation of metal substituted phosphate phases. The formed phosphates are highly insoluble and thermodynamically stable over almost entire pH and Eh range. In the presented study the efficiency and mechanism of cadmium uptake by synthetic hydroxylapatite and natural fluoroapatite was examined within the pH range of 3 7 for different reaction times (2 1440 hours). The solids after reactions were characterized by XRD and SEM-EDS. Percentage reduction of cadmium concentration in the experiments with fluoroapatite and hydroxylapatite, regardless of pH, did not exceed 17% and 25%, respectively. Cadmium uptake from the solution mainly resulted from the formation of cadmium phosphates and/or Ca-Cd phosphate solid solutions on the apatites surface. The release rate of phosphate ions by hydroxylapatite was relatively high. This promoted crystallization of a large number of small crystals. In turn dissolution of fluoroapatite was slower and thus the formation of large crystals was observed. There was no clear evidence for cadmium-calcium ion-exchange mechanism.

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pH-dependence of solubilities of solid solutions of calcium and strontium hydroxylapatites

Cited by 15 publications

References 6 publications

Lattice parameters and cation distribution of solid solutions of calcium and strontium hydroxyapatite

Lattice parameters and cation distribution of solid solutions of calcium and strontium hydroxyapatite

Physico-chemical aspects of calcium vanadate apatite

Aqueous cadmium removal by hydroxylapatite and fluoroapatite

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