Sorption and abiotic reactions of aromatic amines in aqueous soil systems
Abstract
The short and long-term interactions of several aromatic amines in CaCl 2 electrolyte solutions were studied with five soils using a batch equilibration method. Soils varied in pH (4.4–7.4), cation exchange capacity (CEC, 4.4–36.2 cmol(–)/kg), and organic carbon content (OC, 0.4–5%). Reversible sorption processes reached equilibrium within the first day of equilibration while irreversible binding and/or transformation proceeded for much longer times. Cation exchange contributed the most to the reversible sorption of aromatic amines with soil-solution pH and cation exchange capacity being the primary controlling factors. Soil-induced irreversible abiotic reactions of aromatic amines included both mineral-catalyzed redox transformation and covalent binding to SOM. For the combination of aromatic amines and soils investigated in this study, oxidative radical coupling was only evident for amines with half-wave oxidation potentials (E1/2) < 0.54V. For p-methoxyaniline and α-naphthylamine, evidence of mineral-catalyzed dimerization was confirmed with GC/MS and UV-Vis detection. Irreversible and reversible processes appeared to occur in parallel, thus reversible sorption impacted the aromatic amine concentrations available for irreversible abiotic transformations. Estimated irreversible reaction rates were found to be inversely related to both Hammett constants and E 1/2 values, which are indicators of the intrinsic solute reactivity. The information obtained in this study improves our ability to assess mobility, bioavailability and subsequent remediation of sites contaminated with aromatic amines.
Degree
Ph.D.
Advisors
Lee, Purdue University.
Subject Area
Environmental science|Soil sciences|Environmental engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.