Effect of natural organic matter on the reduction of nitroaromatics by Fe(II) species.

Uncertainty still exists regarding the role(s) of natural organic matter in the reduction of chemicals in anoxic environments. This work studied the effect of Suwannee river humic acid (SRHA) on the reduction of nitrobenzenes in goethite suspensions by Fe(II) species. The pseudo-first-order rate constant for the reduction of p-cyanonitrobenzene (k(CNNB)) was different for the first 3 half-lives in systems where Fe(II)aq and dissolved SRHA were equilibrated in reverse orders with goethite in suspensions.

QSAR study of the reduction of nitroaromatics by Fe(II) species.

The development of predictive models for the reductive transformation of nitroaromatics requires further clarification of the effect of environmentally relevant variables on reaction kinetics and the identification of readily available molecular descriptors for calculating reactivity. Toward these goals, studies were performed on the reduction of a series of monosubstituted nitrobenzenes in Fe(II)-treated goethite suspensions. The energy of the lowest unoccupied molecular orbital, ELUMO (B3LYP/6-31G*,water), of the nitrobenzenes was capable of explaining 99% of the variability in the rates.

Reduction of nitrosobenzenes and N-hydroxylanilines by Fe(II) species: elucidation of the reaction mechanism.

Although there has been a substantial effort toward understanding the reduction of nitroaromatics in Fe(II)-treated ferric oxide systems, little has been done to gain insight into the factors controlling the transformation of their reaction intermediates, nitrosobenzenes and N-hydroxylanilines, in such systems. Nitrosobenzenes, the first intermediates, were reduced by Fe(II) solutions as well as by Fe(II)-treated goethite suspensions at pH 6.6.

Sediment-associated reactions of aromatic amines. 2. QSAR development.

The fate of aromatic amines in soils and sediments is dominated by irreversible binding through nucleophilic addition and oxidative radical coupling. Despite the common occurrence of the aromatic amine functional group in organic chemicals, the molecular properties useful for predicting reaction kinetics in natural systems have not been thoroughly investigated. Toward this goal, the sorption kinetics for a series of anilines with substituents in the ortho, meta, or para positions were measured in sediment slurries.