Journal Article•
Síntesis y caracterización de fosfato de calcio y su relación con las propiedades de adsorción del Cr(VI)
28 Aug 2010-Revista Internacional De Contaminacion Ambiental (Centro de Ciencias de la Atmósfera, UNAM)-Vol. 26, Iss: 2, pp 129-134
TL;DR: In this article, the ability of calcium phosphate with hydroxyapatite structure to adsorb Cr(VI) from aqueous solution is presented. But, the specific surface area of the synthesized powder was found to be 64.5 m 2 g 1.
Abstract: Calcium phosphate with hydroxyapatite structure was synthesized and its ability to adsorb Cr(VI) from aqueous solution is presented. XRD, BET, IR, TGA, SEM and EDS techniques were used to characterize the obtained material. A pure phase was obtained through a simple synthesis process. The specific surface area of the synthesized powder was found to be 64.5 m 2 g -1 . The X-ray diffraction pattern shows that the calcium phosphate formed was nanocrystalline with an average grain size of approximately 75 nm. A fast adsorption was observed and in less than 24 h it was found that 2.41 x 10 -4 meq g -1 of Cr(VI) ions were adsorbed on calcium phosphate. Desorption experiments showed that Cr(VI) adsorption decreased to 2.23 x 10 -4 meq g -1 of calcium phosphate. This behavior is a consequence of partial dehydration of the synthesized material. Calcium phosphate can be effectively used for removing Cr(VI) from aqueous solutions in treatment processes of metal wastes.
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Cites background from "Síntesis y caracterización de fosfa..."
...[32], indicating a crystalline single phase of HA hexagonal structure....
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References
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Book•
09 Jun 2013
TL;DR: In this article, X-Rays and Diffraction Lattices and Crystal Structures and Hexagonal Structures are used for X-Ray Diffraction Experimental Modules: Crystal structure determination, I: Cubic Structures Crystal Structure Determination, II: Hexagonal structures Precise Lattice Parameter Measurements Phase Diagram Determination Detection of Long-Range Ordering Determination of Crystallite Size and Lattite Strain Quantitative Analysis of Powder Mixtures Identification of an Unknown Specimen: Appendices: Plane-Spacing Equations and Unit
Abstract: Basics: X-Rays and Diffraction Lattices and Crystal Structures Practical Aspects of X-Ray Diffraction Experimental Modules: Crystal Structure Determination, I: Cubic Structures Crystal Structure Determination, II: Hexagonal Structures Precise Lattice Parameter Measurements Phase Diagram Determination Detection of Long-Range Ordering Determination of Crystallite Size and Lattice Strain Quantitative Analysis of Powder Mixtures Identification of an Unknown Specimen: Appendices: Plane-Spacing Equations and Unit Cell Volumes Quadratic Forms of Miller Indices for the Cubic System Atomic and Ionic Scattering Factors of Some Selected Elements Summary of Structure Factor Calculations Mass Absorption Coefficients mu/rho (cm2/g) and Densities rho (g/cm3) of Some Selected Elements Multiplicity Factors Lorentz-Polarization Factor Physical Constants and Conversion Factors JCPDS-ICDD Card Numbers for Some Common Materials Index
1,594 citations
Book•
22 Jan 1991
TL;DR: The history of Inorganic Ion Exchangers, their classification and present status can be found in this article, with particular references to Zeolites and their applications in radio chemical analysis.
Abstract: Historical Background of Inorganic Ion Exchangers, Their Classification and Present Status. Modern Theories of Ion Exchange and Ion Exchange Selectivity With Particular References to Zeolites. Insoluble Heteropolyacid Salts. Inorganic Ion Exchangers in Radio Chemical Analysis. Inorganic Ion Exchangers for Ion Selective Electrodes. Amorphous Inorganic Ion Exchangersillus.
144 citations
TL;DR: Porous block HA is a viable material for long-term implantation in the maxilla during orthognathic surgery and its microhardness values indicate that the structural integrity of the porous block HA/bone aggregate had been maintained.
129 citations
TL;DR: It has been determined that the variation on the hydroxyapatite sorption capacity is neither related to sample solubility nor to hydroxyAPatite Ca/P molar ratio, and the influence of sample thermal treatment on Cd2+ sorption efficiency is studied.
Abstract: This paper intends to evaluate the uptake of cadmium ions from aqueous solution by 21 hydroxyapatite samples which have been synthesized in different conditions. It has been determined thatthe variation on the hydroxyapatite sorption capacity is neither related to sample solubility nor to hydroxyapatite Ca/P molar ratio. Cd2+ sorption is controlled by sample BET surface area, which shows a direct dependence on the hydroxyapatite crystallite dimensions. The hydroxyapatite pore distribution presented modes at 1000 and 60,000 A, corresponding to intracrystallite voids and voids between the agglomerate of these crystallites, respectively. Pores belonging to the former mode immobilize the major part of Cd2+. The influence of sample thermal treatment on Cd2+ sorption efficiency has been studied using hydroxyapatite samples calcined at temperatures ranging from 500 to 1140 degrees C. Similarly to nonthermally treat samples, the Cd2+ sorption on calcined hydroxyapatite could be described by Langmuir isotherms. The results showed that the maximum sorption capacity decreased from 0.631 mmol g(-1) for the noncalcined sample to 0.150 mmol g(-1) for the one calcined at 900 degrees C. This drop in the sorption capacity could also be explained by a reduction in its specific surface area, which is induced bythe increase of the crystal size.
108 citations
"Síntesis y caracterización de fosfa..." refers result in this paper
...(1998), in strong agreement with literature data (Da-Rocha et al. 2002)....
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TL;DR: In this paper, the precipitation of hydroxyapatite (HA), Ca 5 (OH)(PO 4 ) 3, from highly concentrated CaCl 2 and K 2 HPO 4 solutions, carried out by a continuous method in a MSMPR reactor, is presented.
Abstract: In this paper we present the precipitation of hydroxyapatite (HA), Ca 5 (OH)(PO 4 ) 3 , from highly concentrated CaCl 2 and K 2 HPO 4 solutions, carried out by a continuous method in a MSMPR reactor. The procedure consists of adding the reagents in a ratio Ca to P equal to 1.67, maintaining a temperature of 85°C, inert N 2 atmosphere inside the reactor, and monitoring and adjusting automatically the pH by means of a pH-stat system (pH =9.0 ± 0.1). Under these conditions HA with a Ca to P ratio equal or close to the stoichiometric composition (Ca/P = 1.667), with a high yield (up to 99%) and a high production rate (up to 1.17 g/l.min) is obtained at steady state. The CSD, morphology, crystallinity of the precipitates and impurities present fit the requirement for its biomedical applications.
104 citations
"Síntesis y caracterización de fosfa..." refers methods in this paper
...Materials Calcium phosphate was synthesized at room temperature by the continuous precipitation method as reported by Gómez-Morales et al. (2001). To obtain 10 g of calcium phosphate (hydroxyapatite) 23....
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