Adsorption of ferrous iron on synthesized [gamma]-FeOOH

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Choi, Suingill
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E. Robert Baumann
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Civil, Construction, and Environmental Engineering

Heterogeneous oxidation, where the precipitates resulting from the oxidation of ferrous iron in water accelerate the oxidation rate of ferrous iron has a significant potential for affecting current practice in removal of dissolved iron from water. A better understanding of the oxidation rate law and the factors affecting the rate are necessary in examining the feasibility of applying heterogeneous oxidation to engineering practice;Among many factors, the capacity of the oxidation products for adsorption of ferrous iron seems to take a vital place in the heterogeneous oxidation. Thus, lepidocrocite, which is apparently one of the major oxidation products of ferrous iron, was investigated to evaluate the ferrous iron adsorption capacity as well as its morphology and surface area;Lepidocrocites were synthesized by two different methods and a third lepidocrocite was obtained from the 3M Co. The three were identified as true lepidocrocite by their X-ray diffraction patterns. Ferrous iron was oxidized in water in the presence of lepidocrocite and the morphology of the precipitate was observed through Scanning Electron Microscopy. The adsorption capacities of the three lepidocrocites were measured over a pH range of 6 to 6.75 and up to an equilibrium ferrous iron concentration of 10 mg/l;Lepidocrocites used in this study had a variety of morphologies and surface areas from ranging 48.98 to 150.28 m[superscript]2/g. The adsorbed ferrous iron was oxidized on the surface of lepidocrocite and its adsorption capacity was not determined solely by the surface area. A model based on the Freundlich isotherm was developed to predict the effect of pH and the equilibrium ferrous iron concentration in the bulk liquid phase;In addition, the feasibility of applying heterogeneous oxidation to practice was examined qualitatively by testing whether dissolved iron was removed from the raw water when it passed through the iron deposited in a sand filter;The results of this study can be used for further investigation of heterogeneous oxidation by lepidocrocite.

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Thu Jan 01 00:00:00 UTC 1987