| Abstract |
The reductive detoxification of Cr(VI) by sulfite is known as the prevailing strategy and can be successfully implemented for the treatment of Cr(VI)-contaminated waters. However, this method inevitably faces the challenges of excessive consumption of sulfite due to the generations of highly oxidative (OH)-O-center dot and SO4 center dot- during the process of sulfite reducing Cr(VI). In this study, we find that a small quantity of thiocyanate (SCN) can catalytically enhance the process efficiency of Cr(V1) reduction by sulfite and effectively prevent the excessive consumption of sulfite. Specifically, when adding 5 mu M SCN into 100 mu M Cr(VI) + 600 mu M sulfite reaction system at pH 3.5, Cr(VI) reduction amount and [sulfite](oxidation)/[Cr(VI)](reduction) ratio value were approximately 2 and 0.45, respectively, times those in the SCN-free case. The maximum Cr(VI) reduction amount can be achieved at an initial [SCN]/[Cr(V1)] molar ratio of 2.0. Electron spin resonance measurement, combined with the fluorescence spectrum detection, verified that the process of sulfite reducing Cr(VI) mediated by SCN probably proceeds via the non -radical pathway, avoiding the formation of (OH)-O-center dot and SO4 center dot- under aerobic condition. (C) 2017 Elsevier B.V. All rights reserved. |
