Impact mechanism of particle size and coexisting ions on nitrobenzene reduction in the Fe2+aq-goethite heterogeneous system: Insights from reduction potential.

The chemical reduction of pollutants by Fe2+aq-iron oxides heterogeneous systems is an important component of abiotic natural attenuation. A linear free energy relationship (LFERs) can be established between the reduction potential (EH) of the heterogeneous system and the kinetic parameter (k) of pollutant degradation. However, this relationship was limited to a single iron oxide. The difference in iron oxides particle size and the coexisting anions and cations in groundwater should also be considered. Here, this study investigated the effect of coexisting ions on the nitrobenzene reduction in the Fe2+aq-goethite systems with different particle sizes, and explored the response of LFERs. The results indicated that the standard reduction potential (EH0) of Gt-200 was highest among Gt-200, Gt-700 and Gt-1000. However, the nitrobenzene reduction rate exhibited the highest in the Fe2+aq-Gt-200 heterogenous systems, which was ascribed to the best adsorption affinity of Fe2+aq on Gt-200. Besides, the presence of cations and anions inhibited the reduction rate of nitrobenzene. As for LFERs, the slopes were the same for the Fe2+aq-goethite systems with different particle sizes and coexisting ions. The intercept terms were different. The maximum difference in intercept terms was reduced from 0.98 to 0.37 by correcting the LFERs based on the saturated adsorption capacity of Fe2+aq. The adsorption performance of Fe2+aq on goethite was an important factor affecting the reduction of nitrobenzene. These findings would provide theoretical support for accurately predicting the abiotic natural attenuation rate of nitrobenzene in the presence of coexisting ions in actual groundwater.