Removal of Rhodamine B under visible irradiation in the presence of Fe0, H2O2, citrate and aeration at circumneutral pH

A new Vis-Fe-H2O2-citrate-O-2 system comprising zero-valent iron, hydrogen peroxide, citrate anion and aeration at circumneutral pH under visible irradiation was studied. 21 mu mol L-1 of Rhodamine B (RhB) was chosen as the substrate to be tested. Experiments were conducted under conditions of 2.9 mmol L-1 of H2O2, 12.6 g of Fe-0 and 1.0 mmol L-1 of citrate at pH 7.5. Results showed that, in 1 h reaction, 54% of RhB was removed with corresponding 26% of COD reduced. Meanwhile, the amount of released dissolved irons from Fe-0 surface was found to be at a very low level as <5.4 mu mol L-1. Extinguishing tests with isopropanol suggested that RhB oxidation by hydroxyl radicals was the main process taken place in Vis-Fe-0-H2O2-citrate-O-2 system, which accounted for 75% of substrate removal in 3 h reaction. Control and factor influencing experiments showed that the prohibitive extents of individual factor importance on RhB removal followed a decreasing order of Fe > H2O2 > citrate > Vis > O-2. This study showed an excellent system that could remove refractory organic compounds from water in laboratory researches, and also provided a good idea to reduce secondary contamination by dissolved irons in future investigations. (C) 2011 Elsevier Ltd. All rights reserved.