The influence of Si(iv) on the reactivity of [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples for 2-nitrophenol reduction in γ-AlO suspensions.

In a natural environment, Fe(ii) adsorbed onto the surfaces of natural particles to form various surface complex species can influence the transformation of contaminants. The reductive reactivity of the [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples are close correlated with the surrounding conditions. In this study, we investigated the effects of Si(iv) on the reductive reactivity of [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples adsorbed onto γ-AlO. Experiments were conducted under different conditions to investigate the effects of Si(iv) on the reactivity of [[triple bond, length as m-dash]Fe(iii)]/[[triple bond, length as m-dash]Fe(ii)] couples for 2-nitrophenol (2-NP, selected as the model pollutant) reduction in γ-AlO suspensions. Kinetics results revealed that chemical adsorption is the rate limiting step in Fe(ii) and Si(iv) adsorption processes and the reduction of 2-NP is an endothermic reaction. The linear correlations between the reduced peak oxidation potential ( ) ( SCE) and 2-NP reduction rate (ln ), and between the adsorbed Fe(ii) density ( ) and ln , illustrated that and are two key factors in the inhibiting effects of Si(iv) on the reductive reactivity of Fe(iii)/Fe(ii) couples on γ-AlO. The results of Fe -edge X-ray absorption spectroscopy revealed that the increase of Si(iv) concentration resulted in the gradual change in the composition of the adsorbed Fe species from pure [triple bond, length as m-dash]AlOFe (γ-AlO surface-bound Fe(ii) species with higher reductive reactivity) to a mixture of [triple bond, length as m-dash]AlOFe and [triple bond, length as m-dash]SiOFe (SiO surface-bound Fe(ii) species with lower reductive reactivity), leading to the decrease in , the positive shift in , the increase in activation energy ( ), and consequently the decrease in the reduction rate (ln ) of 2-NP.