The impact of Mn oxide coatings on Zn distribution

Document Type

Article

Publication Date

6-15-2006

Abstract

Zinc sorption to hydrous manganese oxide (HMO)-coated clay was investigated macroscopically, kinetically, and spectroscopically. Adsorption edges and isotherms revealed that the affinity and capacity of the HMO-coated montmorillonite was greater than that of montmorillonite, and when normalized to the oxide present, the coatings behaved similarly to the discrete Mn oxide. Over two pH conditions, 5 and 6, a linear relationship was observed for the isotherms; further analysis with X-ray absorption spectroscopy (XAS) resulted in one type of sorption configuration as a function of loading and ionic strength at pH 5. However, at a surface loading of 10-3 molZn gHMO - coated clay-1 when the pH increased from 5 to 7, the first shell distance decreased slightly, while the atoms and coordination numbers remained the same; this change may be attributed to an increase in electrostatic interactions. After a contact time of 4 months where an additional 60% of the sites become occupied, the slower sorption process was modeled as intraparticle surface diffusion. Best fit diffusivities ranged from 10-18 to 10-17 cm2 / s, where a slower process was observed for the coated surface as compared to the discrete oxide. Interestingly, the porosity of the Mn oxide coating appears to be influenced by the substrate during its growth, as its increase and shift to a smaller pore size distribution resulted in a diffusivity between that observed for discrete HMO and montmorillonite. © 2006 Elsevier Inc. All rights reserved.

Identifier

33646374150 (Scopus)

Publication Title

Journal of Colloid and Interface Science

External Full Text Location

https://doi.org/10.1016/j.jcis.2006.01.026

ISSN

00219797

First Page

615

Last Page

623

Issue

2

Volume

298

Grant

DE-AC02-98CH10886

Fund Ref

National Science Foundation

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