Related Experiment Video
Updated: May 7, 2026

Experimental Column Setup for Studying Anaerobic Biogeochemical Interactions Between Iron (Oxy)Hydroxides, Trace Elements, and Bacteria
Published on: December 19, 2017
Anodic reactivity of ferrous sulfide precipitates changing over time due to particulate speciation
Elena Mejia Likosova1, Richard N Collins, Jurg Keller
1The University of Queensland , Advanced Water Management Centre (AWMC), St Lucia, Brisbane, Queensland 4072, Australia.
Abstract:
The disposal of ferric phosphate (FePO4) sludge, routinely generated in wastewater and drinking water treatment, has a major impact on the overall treatment cost. Iron sulfide (FeSx) precipitation via sulfide addition to ferric phosphate (FePO4) sludge has been proven to be an effective method for phosphate recovery. Electrochemical oxidation of FeSx can then be utilized to recover ferric iron for reuse back in the phosphate removal process. In this study, the reactivity of FeSx particles for anodic oxidation at pH 4 was studied as a function of time after FeSx precipitate generation at a S/Fe molar ratio of 1.75. Cyclic voltammetry showed high reactivity for fresh FeSx particles, but the reactivity diminished significantly over a period of 1 month. X-ray absorption spectroscopy (XAS) revealed that this reduced reactivity with time is a consequence of the transformation of the FeSx particles in suspension from mackinawite (FeS) to pyrite (FeS2).
Related Concept Videos
Precipitation and Co-precipitation
Acid Mine Drainage
Precipitate Formation and Particle Size Control
The obtained precipitate should be either a pure substance of known composition or easily converted to one by a simple process, such as ignition or drying. In addition, the precipitate should be insoluble and easily filterable. In general, filterability...
Ladder Diagrams: Redox Equilibria
Consider the Fe3+/Fe2+ half-reaction, which has a standard-state potential of +0.771 V. At potentials more positive than +0.771 V, Fe3+ predominates, whereas Fe2+...
Electrodeposition
Electrodeposition can...
Precipitation Titration: Endpoint Detection Methods
In the Volhard method, a standard excess of AgNO3 is first added to the...

