Quantitation of Hydroxyl Radicals from Photolysis of Fe(III)-Citrate Complexes in Aerobic Water (5 pp) |
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Authors: | Changbo Zhang Lei Wang Feng Wu Nansheng Deng |
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Institution: | (1) Changbo Zhang School of Resources and Environmental Science Wuhan University Wuhan, 430079 PR China, , ,;(2) Lei Wang School of Resources and Environmental Science Wuhan University Wuhan, 430079 PR China, , ,;(3) Feng Wu School of Resources and Environmental Science Wuhan University Wuhan, 430079 PR China, , ,;(4) Prof. Nansheng Deng School of Resources and Environmental Science Wuhan University Wuhan, 430079 PR China, , , |
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Abstract: | Background For their high photoreactivity, Fe(III)-carboxylate complexes are important sources of H2O2 for some atmospheric and surface
waters. Citrate is one kind of carboxylate, which can form complexes with Fe(III). In our previous study, we have applied
Fe(III)-citrate complexes to degrade and decolorize dyes in aqueous solutions both under UV light and sunlight. Results have
shown that carboxylic acids can promote the photodegradation efficiency. It is indicated that the photolysis of Fe(III)-citrate
complexes may cause the formation of some reactive species (e. g. H2O2 and ·OH). This work is attempted to quantify hydroxyl
radicals generated in the aqueous solution containing Fe(III)-citrate complexes and to interpret the photoreactivity of Fe(III)-citrate
complexes for degrading organic compounds.
Methods By using benzene as the scavenger to produce phenol, the photogeneration of ·OH in the aqueous solution containing Fe (III)-citrate
complexes was determined by HPLC.
Results and Discussion In the aqueous solution containing 60.0/30.0 mM Fe(III)/citrate and 7.0 mM benzene at pH 3.0, 96.66 mM ·OH was produced after
irradiation by a 250W metal halide light (l ≥ 313 nm) for 160 minutes. Effects of initial pH value and concentrations of Fe(III)
and citrate on ·OH radical generation were all examined. The results show that the greatest photoproduction of ·OH in the
aqueous solution (pH ranged from 3.0 to 7.0) was at pH 3.0. The photoproduction of ·OH increased with increasing Fe(III) or
citrate concentrations.
Conclusion In the aqueous solutions containing Fe(III)-citrate complexes, ·OH radicals were produced after irradiation by a 250W metal
halide light. It can be concluded that Fe(III)-citrate complexes are important sources of ·OH radicals for some atmospheric
and surface waters.
Recommendations and Outlook It is believed that the photolysis of Fe(III)-citrate complexes in the presence of oxygen play an important role in producing
·OH both in atmospheric waters and surface water where high concentrations of ferric ions and citrate ions exist. The photoproduction
of ·OH has a high oxidizing potential for the degradation of a wide variety of natural and anthropogenic organic and inorganic
substances. We can use this method for toxic organic pollutants such as organic dyes and pesticides. |
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Keywords: | hydroxyl radicals photoproduction Fe(III)-citrate complexes photoreactivity aerobic water |
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