A comparative study on the dissolution and solubility of hydroxylapatite and fluorapatite at 25°C and 45°C

Zhu, Yinian; Zhang, Xuehong; Chen, Yudao; Quan, Xie; Lan, Jing; Qian, Meifang; He, Na

doi:10.1016/j.chemgeo.2009.07.014

Cited by 97 publications

(57 citation statements)

References 29 publications

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“…In the calculations, we assume water activities of unity, and the equilibrium constant values that were used for Reactions 1-3 were 10 À13.17 , 10 À43.53 , and 10 À53.28 , respectively (Martell and Smith, 2001;Gorman-Lewis et al, 2009;Zhu et al, 2009). …”

Section: Saturation States Calculationsmentioning

confidence: 99%

The effects of non-metabolizing bacterial cells on the precipitation of U, Pb and Ca phosphates

Dunham‐Cheatham

Xue

Bunker

et al. 2011

Geochimica et Cosmochimica Acta

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In this study, we test the potential for passive cell wall biomineralization by determining the effects of non-metabolizing bacteria on the precipitation of uranyl, lead, and calcium phosphates from a range of over-saturated conditions. Experiments were performed using Gram-positive Bacillus subtilis and Gram-negative Shewanella oneidensis MR-1. After equilibration, the aqueous phases were sampled and the remaining metal and P concentrations were analyzed using inductively coupled plasmaoptical emission spectroscopy (ICP-OES); the solid phases were collected and analyzed using X-ray diffractometry (XRD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS).At the lower degrees of over-saturation studied, bacterial cells exerted no discernable effect on the mode of precipitation of the metal phosphates, with homogeneous precipitation occurring exclusively. However, at higher saturation states in the U system, we observed heterogeneous mineralization and extensive nucleation of hydrogen uranyl phosphate (HUP) mineralization throughout the fabric of the bacterial cell walls. This mineral nucleation effect was observed in both B. subtilis and S. oneidensis cells. In both cases, the biogenic mineral precipitates formed under the higher saturation state conditions were significantly smaller than those that formed in the abiotic controls.The cell wall nucleation effects that occurred in some of the U systems were not observed under any of the saturation state conditions studied in the Pb or Ca systems. The presence of B. subtilis significantly decreased the extent of precipitation in the U system, but had little effect in the Pb and Ca systems. At least part of this effect is due to higher solubility of the nanoscale HUP precipitate relative to macroscopic HUP. This study documents several effects of non-metabolizing bacterial cells on the nature and extent of metal phosphate precipitation. Each of these effects likely contributes to higher metal mobilities in geologic media, but the effects are not universal, and occur only with some elements and only under a subset of the conditions studied.

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Section: Saturation States Calculationsmentioning

confidence: 99%

The effects of non-metabolizing bacterial cells on the precipitation of U, Pb and Ca phosphates

Dunham‐Cheatham

Xue

Bunker

et al. 2011

Geochimica et Cosmochimica Acta

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“…An SI greater than zero indicates supersaturation, and an SI less than zero indicates undersaturation. [21] The K sp values 10 À53.28 for Ca 5 (PO 4 ) 3 (OH) was ,3.72 log units lower than 10 À57 reported by Stumm and Morgan. [34] The thermodynamic solubility product for HAP was K sp ¼ 10 À58.3 [35] and 10 À53.9 .…”

Section: Saturation With Respect To Calcium Phosphates and Arsenatesmentioning

confidence: 46%

“…[34] The thermodynamic solubility product for HAP was K sp ¼ 10 À58.3 [35] and 10 À53.9 . [5] Inconsistency in data presented in literature could be due to the failure to achieve equilibrium, [21,31] even though some mineral suspensions were equilibrated for as long as 6 weeks [36] or 120 h [37] before being analysed. Apatite is known to be often non-stoichiometric, specifically Ca deficient.…”

Section: Saturation With Respect To Calcium Phosphates and Arsenatesmentioning

confidence: 99%

“…[15] Some synthesis experiments at ambient temperatures were conducted to evaluate the conditions of formation and solubilities of different calcium arsenates. [11,16,17] Hydroxylapatite (HAP) is one of the most stable forms of calcium phosphate and exhibits a low solubility (K sp ¼ 10 À53.02 -10 À53.51 ); however, the solubility of AsHAP [Ca 5 (AsO 4 ) 3 (OH)] is significantly greater than that of HAP, [11,[18][19][20][21][22] which suggested that phosphate substitution in the arsenate compound could significantly reduce their solubilities. [21][22][23][24] The thermodynamic properties of solid solutions have a vital influence on the transport and fate of toxic metals in the environment.…”

Section: Introductionmentioning

confidence: 99%

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Dissolution and solubility of the arsenate - phosphate hydroxylapatite solid solution [Ca5(PxAs1 - xO4)3(OH)] at 25°C

et al. 2011

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Environmental context. Apatites form a large family of minerals and compounds that can incorporate a variety of ions, including arsenate that can substitute for phosphate. Apatites may therefore control the concentration of arsenic in some aqueous environments. This manuscript describes the synthesis and characterisation of the arsenate-phosphate hydroxylapatite solid solution and the solid solution-aqueous solution interaction.Abstract. Nine different members of the arsenate-phosphate hydroxylapatite solid solution [Ca 5 (P x As 1Àx O 4 ) 3 (OH)] were prepared and characterised by various techniques, and then dissolution of the synthetic solids was studied at 258C and pH 2 in a series of batch experiments. The concentrations of aqueous arsenate species increased rapidly at the beginning of the dissolution and reached a steady-state after 480 h. The concentrations of aqueous phosphate species increased very fast initially and reached a peak value within the first hour of dissolution and then declined slowly with time and remained constant after 240-360 h. The solubility of the Ca 5 (P x As 1Àx O 4 ) 3 (OH) solid solution increased and its stability decreased with an increase in the mole fraction of Ca 5 (AsO 4 ) 3 (OH). The dissolution followed or slightly overshot the Lippmann solutus curve, then approached the solutus curve. The Ca 5 (AsO 4 ) 3 (OH)-poor solid solution was in equilibrium with the arsenate-rich aqueous solution.

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“…It is used, among others, as luminophosphor and in the production of phosphate-based fertilizers. Calcium phosphate hydroxyapatite is showing promise for use as a bioceramic material and as a catalyst or sorbent [6]. Ionic substitution for Ca 2+ , PO 4 3− , and OH − in hydroxyapatite (HAP) is [7].…”

Section: Introductionmentioning

confidence: 99%

Transition from Endothermic to Exothermic Dissolution of Hydroxyapatite Ca5(PO4)3OH–Johnbaumite Ca5(AsO4)3OH Solid Solution Series at Temperatures Ranging from 5 to 65 °C

2018

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Abstract:Five crystalline members of the hydroxyapatite (HAP; Ca 5 (PO 4 ) 3 OH)-johnbaumite (JBM; Ca 5 (AsO 4 ) 3 OH) series were crystallized at alkaline pH from aqueous solutions and used in dissolution experiments at 5, 25, 45, and 65 • C. Equilibrium was established within three months. Dissolution was slightly incongruent, particularly at the high-P end of the series. For the first time, the Gibbs free energy of formation ∆G

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A comparative study on the dissolution and solubility of hydroxylapatite and fluorapatite at 25°C and 45°C

Cited by 97 publications

References 29 publications

The effects of non-metabolizing bacterial cells on the precipitation of U, Pb and Ca phosphates

The effects of non-metabolizing bacterial cells on the precipitation of U, Pb and Ca phosphates

Dissolution and solubility of the arsenate - phosphate hydroxylapatite solid solution [Ca5(PxAs1 - xO4)3(OH)] at 25°C

Transition from Endothermic to Exothermic Dissolution of Hydroxyapatite Ca5(PO4)3OH–Johnbaumite Ca5(AsO4)3OH Solid Solution Series at Temperatures Ranging from 5 to 65 °C

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