25-27 November 2015
National Centre for Synchrotron Science
Australia/Melbourne timezone

Mechanism of Fe(III)-Precipitate Formation and Transformation in Circumneutral Aqueous Solutions in the Presence of Phosphate Under Conditions Relevant to Membrane Bioreactor Wastewater Treatment

26 Nov 2015, 13:30
Exhibition space (National Centre for Synchrotron Science)

Exhibition space

National Centre for Synchrotron Science

Australian Synchrotron 800 Blackburn Road Clayton VIC 3168
Board: EE-11
Poster Earth and Environment Poster Session 1


Dr Christopher Miller (School of Civil and Environmental Engineering, The University of New South Wales)


The formation of iron-phosphate minerals influences the transport and bioavailability of phosphate in natural systems, despite this importance, understanding of the mechanism and rate of this process is limited. Iron addition is also used to remove phosphorous during municipal wastewater treatment to prevent eutrophication and associated algal blooms in receiving waters. The poor understanding of the kinetics of the interaction between Fe and P and the ability of Fe$^{\rm III}$PO$_{4}$(s) formation to compete with rapid Fe(III) hydrolysis to iron oxyhydroxides limits the effective use of this technology, which is one of the few available processes to treat wastewaters to increasingly stringent phosphate discharge limits. This study has used Fe K-edge and P K-edge X-ray absorption spectroscopy experiments (undertaken at BL17C1 and BL16A1 at NSRRC Taiwan) to determine the composition of the Fe-P species in the sludge formed from Fe- and P-containing solutions under a range of initial Fe-oxidation states, relative Fe and P concentrations and also pH (which strongly influences the rate of Fe(II) oxidation and Fe(III)-precipitation). This data has been interpreted using a linear combination fitting scheme that has been adjusted to fit the sample composition to the Fe XANES and EXAFS as well as the P-XANES simultaneously. Coupling this solid-state chemical composition with the solution phase kinetics derived from standard chemical measurements allows the critical processes in the formation of the desired Fe-PO$_{4}$ minerals to be examined.
Keywords multi-element, linear combination fitting, XANES, EXAFS, iron, phosphate, kinetics

Primary authors

Dr Christopher Miller (School of Civil and Environmental Engineering, The University of New South Wales) Mr Hao Wu (The University of New South Wales)


Dr Atsushi Ikeda-Ohno (Helmholtz-Zentrum Dresden-Rossendorf) Prof. T. David Waite (The University of New South Wales) Dr Yuan Wang (The University of New South Wales)

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