Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition

The dissolution mechanism of pure and Cr-substituted, synthetic goethites with different aging times, as well as the changes in morphology, crystallinity and structural changes, were investigated. The Cr-goethites were obtained by synthesizing goethite in solutions that contained different concentra...

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Autores principales:	Tufo, A.E., Sileo, E.E., Morando, P.J.
Formato:	JOUR
Materias:	Acid dissolution Cr-goethite Crystallite size Lattice parameters Reductive dissolution Acid concentrations Aging time CrIII ions Crystal planes Crystallinities Dissolution mechanism Dissolution process Dissolution rates Dissolution time Homogeneous distribution KOH concentration Oxalic Acid Rietveld Structural change Surface reaction control Time span Unit cell parameters XRD Activation energy Chemical analysis Chromium Chromium compounds Dissolution Lattice constants Optical glass Organic acids Rate constants Structural metals Synthetic metals activation energy chemical analysis chromium crystal structure dissolution goethite immobilization lattice dynamics Rietveld analysis substitution
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_01691317_v58_n_p88_Tufo
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

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spelling	todo:paper_01691317_v58_n_p88_Tufo2023-10-03T15:06:57Z Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition Tufo, A.E. Sileo, E.E. Morando, P.J. Acid dissolution Cr-goethite Crystallite size Lattice parameters Reductive dissolution Acid concentrations Acid dissolution Aging time Cr-goethite CrIII ions Crystal planes Crystallinities Dissolution mechanism Dissolution process Dissolution rates Dissolution time Homogeneous distribution KOH concentration Oxalic Acid Reductive dissolution Rietveld Structural change Surface reaction control Time span Unit cell parameters XRD Activation energy Chemical analysis Chromium Chromium compounds Crystallite size Dissolution Lattice constants Optical glass Organic acids Rate constants Structural metals Synthetic metals activation energy chemical analysis chromium crystal structure dissolution goethite immobilization lattice dynamics Rietveld analysis substitution The dissolution mechanism of pure and Cr-substituted, synthetic goethites with different aging times, as well as the changes in morphology, crystallinity and structural changes, were investigated. The Cr-goethites were obtained by synthesizing goethite in solutions that contained different concentrations of Cr(III) ions. The obtained suspensions were aged in the parent solutions for different time spans. Two samples of pure goethites, prepared using different KOH concentrations, were also studied for comparative purposes. Chemical analyses showed that Cr-for-Fe substitution was greatest in samples aged for longer time. Rietveld simulation of XRD powder data indicated that the unit cell parameters of pure goethite increased for samples prepared at a higher KOH concentration, and decreased with Cr-incorporation. Simulation also showed that the mean coherence path dimension (MCP), or crystallite size, in the direction perpendicular to crystal plane (110), did not change much in the samples, whereas the crystallite size in the direction parallel to crystal plane (110) increased with Cr-content, KOH concentration and aging time. The obtained MCP values indicate an increasing elongated form in the domains. Chromium substituted goethites presented a good capacity for immobilizating Cr when the dissolution rates were studied in 3.98M HCl, 0.10M oxalic acid (H 2Oxal), and reductive media (H 2Oxal/Fe(II)). The shape of the f vs. t profile, where f stands for the fraction of Fe dissolved (dissolved Fe mass/total Fe mass) and t refers to the dissolution time, follows a contracting bidimensional model, and when dissolved in similar acid concentrations, the reactivity follows the trend HCl<H 2Oxal≪H 2Oxal/Fe(II), indicating that dissolution is noticeably increased in complexing-reducing media. The dissolution rate constant k values were highly depend on crystallite size, and the dissolution rate decreased in the samples aged longest and in goethites containing higher concentrations of Cr. The release of Fe and Cr is congruent and shows a homogeneous distribution of Fe and Cr in the samples. The calculated activation energies values support a surface reaction control for the dissolution process. © 2012 Elsevier B.V. Fil:Tufo, A.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Sileo, E.E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_01691317_v58_n_p88_Tufo
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Acid dissolution Cr-goethite Crystallite size Lattice parameters Reductive dissolution Acid concentrations Acid dissolution Aging time Cr-goethite CrIII ions Crystal planes Crystallinities Dissolution mechanism Dissolution process Dissolution rates Dissolution time Homogeneous distribution KOH concentration Oxalic Acid Reductive dissolution Rietveld Structural change Surface reaction control Time span Unit cell parameters XRD Activation energy Chemical analysis Chromium Chromium compounds Crystallite size Dissolution Lattice constants Optical glass Organic acids Rate constants Structural metals Synthetic metals activation energy chemical analysis chromium crystal structure dissolution goethite immobilization lattice dynamics Rietveld analysis substitution
spellingShingle	Acid dissolution Cr-goethite Crystallite size Lattice parameters Reductive dissolution Acid concentrations Acid dissolution Aging time Cr-goethite CrIII ions Crystal planes Crystallinities Dissolution mechanism Dissolution process Dissolution rates Dissolution time Homogeneous distribution KOH concentration Oxalic Acid Reductive dissolution Rietveld Structural change Surface reaction control Time span Unit cell parameters XRD Activation energy Chemical analysis Chromium Chromium compounds Crystallite size Dissolution Lattice constants Optical glass Organic acids Rate constants Structural metals Synthetic metals activation energy chemical analysis chromium crystal structure dissolution goethite immobilization lattice dynamics Rietveld analysis substitution Tufo, A.E. Sileo, E.E. Morando, P.J. Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
topic_facet	Acid dissolution Cr-goethite Crystallite size Lattice parameters Reductive dissolution Acid concentrations Acid dissolution Aging time Cr-goethite CrIII ions Crystal planes Crystallinities Dissolution mechanism Dissolution process Dissolution rates Dissolution time Homogeneous distribution KOH concentration Oxalic Acid Reductive dissolution Rietveld Structural change Surface reaction control Time span Unit cell parameters XRD Activation energy Chemical analysis Chromium Chromium compounds Crystallite size Dissolution Lattice constants Optical glass Organic acids Rate constants Structural metals Synthetic metals activation energy chemical analysis chromium crystal structure dissolution goethite immobilization lattice dynamics Rietveld analysis substitution
description	The dissolution mechanism of pure and Cr-substituted, synthetic goethites with different aging times, as well as the changes in morphology, crystallinity and structural changes, were investigated. The Cr-goethites were obtained by synthesizing goethite in solutions that contained different concentrations of Cr(III) ions. The obtained suspensions were aged in the parent solutions for different time spans. Two samples of pure goethites, prepared using different KOH concentrations, were also studied for comparative purposes. Chemical analyses showed that Cr-for-Fe substitution was greatest in samples aged for longer time. Rietveld simulation of XRD powder data indicated that the unit cell parameters of pure goethite increased for samples prepared at a higher KOH concentration, and decreased with Cr-incorporation. Simulation also showed that the mean coherence path dimension (MCP), or crystallite size, in the direction perpendicular to crystal plane (110), did not change much in the samples, whereas the crystallite size in the direction parallel to crystal plane (110) increased with Cr-content, KOH concentration and aging time. The obtained MCP values indicate an increasing elongated form in the domains. Chromium substituted goethites presented a good capacity for immobilizating Cr when the dissolution rates were studied in 3.98M HCl, 0.10M oxalic acid (H 2Oxal), and reductive media (H 2Oxal/Fe(II)). The shape of the f vs. t profile, where f stands for the fraction of Fe dissolved (dissolved Fe mass/total Fe mass) and t refers to the dissolution time, follows a contracting bidimensional model, and when dissolved in similar acid concentrations, the reactivity follows the trend HCl<H 2Oxal≪H 2Oxal/Fe(II), indicating that dissolution is noticeably increased in complexing-reducing media. The dissolution rate constant k values were highly depend on crystallite size, and the dissolution rate decreased in the samples aged longest and in goethites containing higher concentrations of Cr. The release of Fe and Cr is congruent and shows a homogeneous distribution of Fe and Cr in the samples. The calculated activation energies values support a surface reaction control for the dissolution process. © 2012 Elsevier B.V.
format	JOUR
author	Tufo, A.E. Sileo, E.E. Morando, P.J.
author_facet	Tufo, A.E. Sileo, E.E. Morando, P.J.
author_sort	Tufo, A.E.
title	Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
title_short	Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
title_full	Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
title_fullStr	Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
title_full_unstemmed	Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition
title_sort	release of metals from synthetic cr-goethites under acidic and reductive conditions: effect of aging and composition
url	http://hdl.handle.net/20.500.12110/paper_01691317_v58_n_p88_Tufo
work_keys_str_mv	AT tufoae releaseofmetalsfromsyntheticcrgoethitesunderacidicandreductiveconditionseffectofagingandcomposition AT sileoee releaseofmetalsfromsyntheticcrgoethitesunderacidicandreductiveconditionseffectofagingandcomposition AT morandopj releaseofmetalsfromsyntheticcrgoethitesunderacidicandreductiveconditionseffectofagingandcomposition
_version_	1807319168972750848

Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition

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