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Paper Information

Title: 

THE APPLICATION OF NANOMINERALOGY METHODS IN THE STUDY OF ARSENIC ABSORPTION BY IRON OXIDE AND HYDROXIDES

Type: PAPER
Author(s): RAZMARA MORTEZA*
 
 *
 
Name of Seminar: SYMPOSIUM OF EARTH SCIENCES
Type of Seminar:  SYMPOSIUM
Sponsor:  ORGANIZATION OF GEOLOGICAL OF IRAN
Date:  2006Volume 24
 
 
Abstract: 

The mobility and toxicity of arsenic and its compounds in the environment varies dependent on its oxidation states. As a result determination of its oxidation state is necessary. Extended x-ray absorption fine structure (EXAFS) provided element specific, averaged short range structural information on the radial environment surrounding the target element (As). Thus it was possible to obtain local coordination number, interatomic distances and neighbouring atoms by nanomineralogical methods. The mean bond length between, As-Ag, As-S, Fe-S, Sb-S and As-As in arsenic minerals was determined by XAS. The ligands information around arsenic atoms was obtained directly from EXAFS and indirect from XANES. Direct measurements of disorder parameters (Debye – Waller factors) in the samples were obtained by EXAFS methods. Rietveld refinements are used to determine the unit cell parameters and site occupancy for powder XRD patterns. Arsenic bearing phases and diffusion of As in minerals were distinguished by HRXRD, SEM and EPMA. The XANES analysis showed that, although other As states were observed in the samples, but As5+ was the dominant oxidation state. The study showed that arsenic sorbed to iron oxides through a distinct mechanism. These data indicated that although arsenic adsorbed strongly by iron oxide minerals; but the major adsorbent of As is trivalent iron.

 
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