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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2012
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_01691317_v58_n_p88_Tufo http://hdl.handle.net/20.500.12110/paper_01691317_v58_n_p88_Tufo |
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paper:paper_01691317_v58_n_p88_Tufo2023-06-08T15:18:13Z Release of metals from synthetic Cr-goethites under acidic and reductive conditions: Effect of aging and composition Tufo, Ana Elisabeth Sileo, Elsa Ester 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. 2012 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_01691317_v58_n_p88_Tufo 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, Ana Elisabeth Sileo, Elsa Ester 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. |
| author |
Tufo, Ana Elisabeth Sileo, Elsa Ester |
| author_facet |
Tufo, Ana Elisabeth Sileo, Elsa Ester |
| author_sort |
Tufo, Ana Elisabeth |
| 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 |
| publishDate |
2012 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_01691317_v58_n_p88_Tufo http://hdl.handle.net/20.500.12110/paper_01691317_v58_n_p88_Tufo |
| work_keys_str_mv |
AT tufoanaelisabeth releaseofmetalsfromsyntheticcrgoethitesunderacidicandreductiveconditionseffectofagingandcomposition AT sileoelsaester releaseofmetalsfromsyntheticcrgoethitesunderacidicandreductiveconditionseffectofagingandcomposition |
| _version_ |
1768542078059413504 |