Catalytic effects of Fe(III) during oxygenation of Fe(II) in continuous flow iron removal systems

Abstract

In this study, an iron removal process, which makes use of the catalytic effect of ferric iron, is proposed. For this purpose, a lab-scale continuous flow aeration/ sedimentation unit with or without recycling was built. The aim of the study was to verify the validity of the findings of batch-type oxidation experiments also for continuous flow conditions. The efficiency of oxidation was about 57-79 % when the system was operated without recycling. Fe(II) removal efficiencies could be increased to 80-89 %, 90-97 % and 98-99.6% for the recycling ratios of 50 %, 80% and 100%, respectively. The increase of Fe(II) removal was explained by an increase of ferric concentration in the aeration tank as a result of recycling. The higher the Fe(III) concentration in the aeration tank the better was the Fe(II) removal efficiency up to a Fe(III) concentration of 300 mg/l. Beyond this level, no significant increase in removal efficiency of ferrous iron was observed with increasing ferric iron concentration.