The Influence of Iron (II) and (III) on the Kinetics of Goethite Dissolution by EDTA

✍ Scribed by Marı́a C. Ballesteros; Elsa H. Rueda; Miguel A. Blesa

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 151 KB
• Volume: 201
• Category: Article
• ISSN: 0021-9797
• DOI: 10.1006/jcis.1997.5360

✦ Synopsis

The dissolution of goethite in aqueous media containing EDTA, experimental study of the influence of Fe III addition on the Fe(II), and Fe(III) has been studied. The main dissolution pathrate of goethite dissolution by ferrous EDTA in acidic media.

ways involve the inner or outer sphere electron transfer in mixed-

The adsorption of EDTA onto iron oxides has been studied valence EDTA-bridged surface complexes and in surface ''ion by us (6-8) and by others (9-15). More than one mode pairs.'' A synergistic effect is observed between ferrous EDTA and of surface complexation has been proposed, the modes diffree EDTA. The rate dependencies on [EDTA] and [Fe II ] are fering in the number of anchoring bonds to the solid surface. interpreted in terms of Fe(II) phase transfer from three different For example, in (7), it is proposed that adsorption takes surface complexes: GFe III -Y-Fe II (Y is the EDTA anion), place in two stages; at low EDTA concentration, four carbox-GFe III -YrrrFe II Y, and the dimeric species with adjacent sites GFe III -Y and GFe III -Y-Fe II . Addition of iron(III) produces a ylate groups bind surface Fe(III) ions in magnetite, whereas rate decrease that is explained on the basis of the adsorption behavat higher EDTA concentrations, binding through only two ior of Fe III Y 0 , for which adsorption data are presented. The redox -COO 0 was proposed. Nowack and Sigg (15) have proequilibration of the surface is discussed. ᭧ 1998 Academic Press posed the two modes depicted in Eqs. [1] and [2], with the Key Words: reductive dissolution; goethite; Fe II -EDTA/Fe IIIquoted intrinsic surface complexation constants calculated EDTA complexes; surface complexation. using the constant capacitance model for the double-layer region.

In what follows, H n Y n0 4 shall represent the various proto-