Effect of Substitution on Irreversible Binding and Transformation of Aromatic Amines with Soils in Aqueous Systems

Abstract

Predicting the irreversible interactions between aromatic amines and soil is essential for assessing mobility, bioavailability and subsequent remediation of aromatic aminecontaminated sites. The kinetics of irreversible binding and/ or transformation of a series of para-substituted anilines and R-naphthylamine were studied on several surface soils for a one-to two-month equilibration period. To estimate reaction rates, a heterogeneous reactivity model was developed assuming that irreversible reactions are firstorder with respect to the amine solution concentration; activation energies vary linearly as a function of reacted sites; and available soil reactive sites change over time but remain more numerous than sites consumed. The validity of the latter assumption was demonstrated for the experimental variables in these studies. The observed change in reaction rates with time was best described using a biphasic approach where apparent rate constants (k app ) and the relationship between activation energies and reacted sites (R) were independently estimated for contact times e 20 h and > 20 h. For both operationally defined time frames, inverse log-linear relationships are observed between k app values and both Hammett constants and half-wave oxidation potentials (E 1/2 ), which are indicators of the intrinsic solute reactivity. Dimerization was only evident for amines with reactivity greater than methylaniline or with E 1/2 < 0.54 V. Reaction complexity and site heterogeneity resulted in a lack of correlation with soil properties. However, preliminary results showing an increase in exchangeable Mn 2+ from soils after irreversible reactions with amines were allowed to occur demonstrated that manganese oxides in whole soils play a significant role in causing radical amine cation formation and subsequent coupling.

Methanogenic inhibition by roxarsone (4-hydroxy-3-nitrophenylarsonic acid) and related aromatic arsenic compounds

“…Although the oxidative transformation products formed in the initial phase of the oxidation are considerably more toxic than HAPA and roxarsone, further polymerization to high molecular weight compounds is expected to decrease toxicity. Similarly to other amino-aromatic compounds [41, 42], HAPA autooxidation in soils and sediments is likely to result in incorporation of the organoarsenic compound into humic structures. Copolymerization of amino-aromatic compounds with humic structures is an irreversible process that often leads to a sharp decrease in the mobility and toxicity of the aromatic compounds.…”

Biodecolorization of the Azo Dye Reactive Red 2 by a Halotolerant Enrichment Culture

“…The decrease in aniline concentration is attributed to an aniline‐consuming process. Although it has been well‐documented that aniline degradation under anaerobic conditions does not generally take place ( O'Neill et al, 2000 ), there are other processes, such as association of aniline with quinones and solids, which could lead to a decrease of free aniline in the liquid phase ( Li and Lee, 1999 ; Li et al, 2000 ; Weber et al, 1996 ). Based on the maximum measured aniline concentrations, the calculated aniline recovery varied from 12.3 to 33.5% (Table 1).…”

Review of the Ecotoxicological Properties of the Methylenedianiline Substances

“…The 8 h value achieved approximately 90 % of the value measured after 7 days equilibration time. After 7 days, part of the MDA could be desorbed when equilibrated with fresh 0.1 M CaCl 2 for 24 h. The high affinity of MDA to soil is most likely attributable to reversible and irreversible binding of the aromatic amino group to organic matter (Tatsumi et al 1994;Parris 1980;Weber et al 1996;Li et al 2000;Colón et al 2002).…”