| Summary: | In order to model the transport and fate of aniline and chloroaniline in the subsurface, the geochemical reactions between these contaminants and important metals and minerals surfaces must be quantified. === The thermodynamic stabilities of the aqueous and surface aluminum-aniline and aluminum-2-chloroaniline complexes were investigated at 55$ sp circ$C and 80$ sp circ$C. Solubility and adsorption experiments place quantitative constraints on the thermodynamic properties of these complexes. No evidence was found for stable Al-aniline or Al-2-chloroaniline aqueous complexes. Conversely, the adsorption data provide unequivocal evidence for the presence of two distinct surface Al-aniline and A-chloroaniline complexes according to the following reactions: (1) $Aniline sp circ + { equiv}Al(OH) sp circ leftrightarrow { equiv}(AlOH(Aniline) sp circ$; (2) $Aniline sp circ + { equiv}Al(O) sp- leftrightarrow { equiv}AlO(Aniline) sp-$; (3) $Chloroaniline sp circ + { equiv}Al(OH) sp circ leftrightarrow { equiv}AlOH(Chloroaniline) sp circ$; (4) $Chloroaniline sp circ + { equiv}Al(OH sb2) sp+ leftrightarrow { equiv}AlOH sb2(Chloroaniline) sp+$. === A constant capacitance model is used to quantify the stability constants for reactions (1) - (4), and the results yield equilibrium constant values of 10$ sp{2.09}$, 10$ sp{2.67}$, 10$ sp{2.87}$ and 10$ sp{2.30}$ respectively. These results indicate that mineral surface complexation can significantly affect total aniline and chloroaniline budgets.
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