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Free Content INFLUENCE OF GIBBSITE SURFACE AREA AND CITRATE ON Ni SORPTION MECHANISMS AT pH 7.5

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We investigated the sorption of Ni to gibbsite of two different surface areas at pH 7.5, in the presence and absence of citrate, over a time period of 180 days. Extended X-ray absorption fine-structure spectroscopy was employed to elucidate the sorption mechanisms at the molecular level. In agreement with former results, Ni-Al layered double hydroxide (LDH) formed in the presence of gibbsite of low surface area. However, gibbsite of high surface area suppressed the formation of the surface precipitate. Instead, two Al atoms neighboring Ni at distances of 2.95 ­2.98 A˚indicated formation of an inner-sphere sorption complex, where each NiO6-octahedron shares edges with two AlO6-octahedra. Focused multiple scattering arising from Al atoms at a distance of 6 A˚suggest that sorbed Ni(OH)2(OH2)4 monomers epitaxially extend the hexagonal arrangement of Al atoms in gibbsite. Only after 30 days or more was a small amount of LDH formed. The presence of citrate prevented the formation of LDH, while maintaining the formation of inner-sphere sorption complexes.

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Keywords: CITRATE; EXAFS; GIBBSITE; LAYERED DOUBLE HYDROXIDE; NI; PRECIPITATE; SORPTION; SURFACE; SURFACE AREA

Document Type: Research Article

Publication date: 2002-12-01

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  • The JOURNAL publishes articles of interest to the international community of clay scientists, including but not limited to areas in mineralogy, crystallography, geology, geochemistry, sedimentology, soil science, agronomy, physical chemistry, colloid chemistry, ceramics, petroleum engineering, foundry engineering, and soil mechanics. Clays and Clay Minerals exists to disseminate to its worldwide readership the most recent developments in all of these aspects of clay materials. Manuscripts are welcome from all countries.

    Clays and Clay Minerals is the official publication of The Clay Minerals Society.

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