Kinetics of iron (II) oxidation determined in the field

Geroni, Jennifer N. and Sapsford, Devin James ORCID: https://orcid.org/0000-0002-6763-7909 2011. Kinetics of iron (II) oxidation determined in the field. Applied Geochemistry 26 (8) , pp. 1452-1457. 10.1016/j.apgeochem.2011.05.018

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Abstract

This paper presents the results of extensive field trials measuring rates of Fe(II) oxidation at a number of Fe-bearing mine drainage discharges in the UK. Batch experiments were carried out with samples taken at regular intervals and Fe(II) concentration determined spectrophotometrically using 2′2-bipyridyl as the complexing agent. Initial concentrations for Fe(II) were 5.65–76.5 mg/L. Temperature, pH and dissolved O2 (DO) were logged every 10 s, with pH at the start of the experiments in the range 5.64–6.95 and alkalinity ranging from 73 to 741 mg/L CaCO3 equivalent. A numerical model based on a fourth order Runge–Kutta method was developed to calculate values for k1, the rate constant for homogeneous oxidation, from the experimental data. The measured values of pH, temperature, [Fe(II)] and DO were input into the model with resulting values for k1 found to be in the range 2.7 × 1014–2.7 × 1016 M−2 atm−1 min−1. These values for k1 are 1–3 orders of magnitude higher than previously reported for laboratory studies at a similar pH. Comparison of the observed Fe(II) oxidation rates to data published by other authors show a good correlation with heterogenous oxidation rates and may indicate the importance of autocatalysis in these systems. These higher than expected rates of Fe oxidation could have a significant impact on the design of treatment schemes for the remediation of mine drainage and other Fe-bearing ground waters in the future.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Subjects:	Q Science > QE Geology T Technology > TN Mining engineering. Metallurgy
Publisher:	Elsevier
ISSN:	0883-2927
Last Modified:	18 Oct 2022 13:29
URI:	https://orca.cardiff.ac.uk/id/eprint/14040

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