Photocatalyfic reduction of Cr(VI) in the presence of NO3- and Cl- electrolytes as influenced by Fe(III)
Journal
Environmental Science and Technology
Journal Volume
41
Journal Volume
41
Journal Issue
22
Journal Issue
22
Pages
7907-7914
Start Page
7907
End Page
7914
ISSN
0013936X
Date Issued
2007-11-15
Author(s)
Abstract
Photoreduction of Cr(VI) involving Fe is strongly affected by the presence of organic or inorganic compounds in an acidic environment. In this study, we have found a new pathway of Cr(VI) photoreduction in the presence of Fe(III) that is influenced by two inorganic electrolytes (i.e., NO3 - and Cl-) and the pH. In NO3- and Cl- systems without Fe(III), Cr(VI) photoreduction could occur and was independent of the Cr(VI) concentration. The zero-order rate constant of the photoreduction reaction increased when the solution pH was decreased from 2 to 1; the reaction rate was higher in the NO3- system than in the Cl- system. The higher reaction rate in the NO3 - system was attributed to the photolysis of NO3 -, which resulted in the formation of NO2- for reduction of Cr(VI). Conversely, the effect of Fe(III) addition on the increase in Cr(VI) photoreduction rate in the Cl- system was more significant than that in the NO3- system. The addition of Fe(III) to the Cl- system caused the formation of [Fe(OH2) 5Cl]2+, the photolysis of which subsequently resulted in the formation of Fe(II) for reduction ofthe Cr(VI).Thisstudy suggests thatthe photolysis of NO3- and Fe-Cl complex may contribute significantly to Cr(VI) reduction in surface waterthat receives electroplating wastewater containing high levels of NO3-, Cl-, and Fe(III). Therefore, under the acidic conditions that are favorable for Fe-Cl complex formation or in the presence of NO3-, the effects of inorganic components on Cr(VI) photoreduction cannot be ignored for the precise evaluation of the transformation of Cr in the environment.
SDGs
Type
journal article