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SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES: 1. ELUCIDATION OF SORPTION MECHANISMS
Citation:
Weber, E J., D Colon, AND G L. Baughman. SEDIMENT-ASSOCIATED REACTIONS OF AROMATIC AMINES: 1. ELUCIDATION OF SORPTION MECHANISMS. ENVIRONMENTAL SCIENCE & TECHNOLOGY 35(12):2470-2475, (2001).
Impact/Purpose:
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
Description:
Sorption of aromatic amines to sediments and soils can occur by both reversible physical processes and irreversible chemical processes. To elucidate the significance of these sorption pathways, the sorption kinetics of aniline and pyridine were studied in resaturated pond sediment. Ani line and pyridine behaved quite differently in the sediment-water systems. The
sorption kinetics of pyridine were quite fast, reaching equilibrium within 1-2 h. in contrast, the sorption kinetics of aniline were characterized by a rapid initial loss of aniline from the aqueous phase followed by a much slower rate of disappearance. The rapid initial sorption of aniline upon respiking after an equilibration period of 200 h, and results of sorption kinetic studies as a
function of substrate concentration, demonstrated that sorptive sites were not being saturated at the nominal concentration of aniline. Sequential extraction of a sediment treated with C-14-labeled pyridine and aniline suggested that pyridine was bound primarily through a reversible cation-exchange process, whereas aniline sorbed through bath cation-exchange and covalent binding processes. At longer reaction periods sorption became increasingly dominated by covalent binding. The reaction kinetics for the slow, irreversible sorption of aniline appeared to be limited by the reactivity and/or availability of covalent binding sites. The initial rate and extent of aniline sorption was pH dependent (sorption increased with decreasing pH). At pH values above the pK(a) of aniline, sorption kinetics for the slower, irreversible loss of aniline were independent of pH.