Strong enhancement of dye removal through addition of sulfite to persulfate activated by a supported ferric citrate catalyst

In this study, reductive sulfite (S(IV)) was innovatively introduced into activated carbon fibers supported ferric citrate (Cit-Fe@ACFs) and persulfate (PS) process for organic dye removal. The addition of S(IV) enhanced the catalytic elimination rate of organic dye Reactive Red M-3BE from 15.2% to 96.2% in 12 min (k(obs) (pseudo-first-order rate constant) from 0.015 to 0.324 min(-1)). More importantly, the simultaneous removal of S(IV), which is a common inorganic pollutant, was also achieved. This Cit-Fe@ACFs/S (IV)/PS system exhibited superior sustained catalytic ability and distinguished pH-tolerant performance for the simultaneous rapid removal of dyes and inorganic S(IV). Furthermore, the reaction rate constant (k(obs)) increased with the increase of concentration of S(IV) below 1 mM, while decreased over 1 mM. Finally, various radical scavengers were used together with electron paramagnetic resonance spectroscopy to confirm that hydroxyl ((OH)-O-center dot), sulfate (SO4 center dot-) and peroxymonosulfate (SO5 center dot-) radicals served as the major reactive oxygen species in the Cit-Fe@ACF5/S(IV)/PS system. This study provides a promising idea to use polluting S(IV) in sewage treatment for the simultaneous removal of organic and inorganic pollutants. (C) 2015 Elsevier B.V. All rights reserved.