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Electrokinetic generation of reactive iron-rich barriers in wet sediments: implications for contaminated land management

¹ Division of Civil Engineering and Geology, University of Brighton, Brighton BN2 4GJ, UK
² Centre for Environmental Research, University of Sussex, Brighton BN1 9QJ, UK

^* E-mail: d.w.s.faulkner{at}brighton.ac.uk

Here we describe preliminary research into the in situ electrokinetic generation of continuous iron-rich precipitates to act as sub-surface barriers for the containment of contaminated sites. This is achieved using sacrificial iron electrodes emplaced either side of a soil/sediment mass to introduce iron into the system, and their dissolution and re-precipitation under the influence of an applied (DC) electric field. Continuous vertical and horizontal iron-rich bands (up to 2 cm thick) have been generated over a timescale of 300–500 h, at voltages of <5 V with an electrode separation of between 15 and 30 cm. The thickness of the iron-rich band increases as the applied voltage is increased. Geotechnical tests in sand indicate that the iron-rich band produced is practically impervious (coefficient of permeability of 10^–9 ms^–1 or less), and has significant mechanical strength (unconfined compressive strength of 10.8 N mm^–2). By monitoring the current, the integrity of the iron-rich band may be assessed, and by continued application of current, the barrier may ‘self heal’. The iron-rich barrier is composed of amorphous iron, goethite, lepidocrocite, maghemite and native iron.

KEYWORDS: electrokinetics, horizontal barriers, iron, contaminated land

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