Stability of iron in clays under different leaching conditions

0439270 - ÚACH 2015 RIV US eng J - Článek v odborném periodiku
Doušová, B. - Fuitová, L. - Koloušek, D. - Lhotka, M. - Matys Grygar, Tomáš - Spurná, P.
Stability of iron in clays under different leaching conditions.
Clays and Clay Minerals. Roč. 62, 1-2 (2014), s. 145-152. ISSN 0009-8604. E-ISSN 1552-8367
Institucionální podpora: RVO:61388980
Klíčová slova: Clays * Iron * Leaching Stability * Structure * Surface Properties
Kód oboru RIV: DD - Geochemie
Impakt faktor: 1.228, rok: 2014

The iron chemistry of aluminosilicates can markedly affect their adsorption properties due to possible changes in surface charge upon exposure to a variety of processes in the environment. One of these processes is chemical leaching, but to date little has been reported on the susceptibility of structural Fe to chemical leaching. The purpose of the current study was to determine the effects of solution pH on the stability of structural Fe in kaolinites, illite, and bentonite and the potential for formation of ancillary (oxyhydr)oxides. Structurally bound Fe does not participate in sorption properties but Fe that is released and phase transformed during leaching could take part in adsorption processes and form complexes and/or covalent bonds via Fe ions. Five different Fe-bearing clay minerals were treated in 0.5 M and 2 M HCl, distilled H2O, 0.1 M KCl, and 0.5 M KHCO3 for 24 h. The amount of Fe leached varied from 10 mu g g(-1) (for 0.1 M KCl) to 104 fig (for 2 M HCl) depending on the leaching agents. Acidic and water treatments indicated a relative independence of leached Fe on the initial Fe content in the clay and, conversely, a heavy dependence on the crystallinity of initial Fe phases. Well crystallized Fe(III) was stable during the leaching process, while poorly crystallized and amorphous Fe(III) phases were less stable, forming new ion-exchangeable Fe3+ particles. Under alkaline conditions, no relation between Fe crystallinity and mobility was found. The structural and surface changes resulting from leaching processes were identified by equilibrium adsorption isotherms. In kaolinite, the specific surface area (SBET) and porosity changed independently of Fe leaching due to the stability and crystallinity of Fe.
Trvalý link: http://hdl.handle.net/11104/0242615