ABSTRACT
Interfacial Chemistry of Dissolving Metal Oxide Particles: Dissolution by Organic Acids J. ADRIAN SALFITY, ALBERTO E. REGAZZONI, and MIGUEL A. BLESA Department of Chemistry, Atomic Energy Commission, Buenos Aires, Argentina
I. Introduction 513 II. Brief Review of the Relevant Aqueous Chemistry o f Metal Ions and
Organic Acids 514 A. The stability of carboxylate complexes in solution 514 B. Kinetics o f metal ion complexation by carboxylates 516 C. The structure of dissolved complexes 518 D. Electron-transfer reactions in solution 519
III. The Interaction of Carboxylates with Metal Oxide Surfaces Immersed in Water 520
IV. Nonequilibrated Interfaces in Mineral and Organic Acids 529 A. Kinetics of surface complexation 529 B. Kinetics o f metal oxide dissolution 530 C. Dissolution in the presence of carboxylic acids 533 References 538
I. INTRODUCTION
The surface complexation approach has been much used to describe chemisorption of ions and molecules. Mainly, equilibrated systems have been analyzed, and the analogy with homogeneous coordination chemistry has been stressed. By now, an impressive wealth of knowledge is available that supports this equilibrium description, even accepting the approximate nature of the concept of surface complex (for earlier reviews of the subject, see Ref. 1-4). Within the subjects described by the surface complexation approach, the adsorption of carboxylic and phenolic acids onto metal oxides takes a prominent place. Because of the wide usage of synthetic organic acids, and the widespread occurrence of natural acids, the environmental relevance of the question is large. The mobilization of heavy metal ions in the environment is heavily influenced by surface complexation reactions of this type. Also, in several fields of technology, the interaction is of importance: for instance, in the procedures to decontaminate nuclear reactors, or to clean steam generators. Finally, the biological relevance of the subject is also high.
