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Rates and mechanisms of chemical processes affecting the treatment of ferruginous mine water

Geroni, Jennifer 2011. Rates and mechanisms of chemical processes affecting the treatment of ferruginous mine water. PhD Thesis, Cardiff University.

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Abstract

This thesis presents the results of research undertaken into the rates of Fe(II) oxidation and CO2 stripping from ferruginous mine drainage. It also provides new insight into the applicability of Vertical Flow Reactors (VFRs) to the treatment circumneutral waters. Batch-wise experiments were used to determine Fe(II) oxidation rates in the field. The data collected were used to show that values for the rate constant k1 were up to 3 orders of magnitude greater at the field sites than would be predicted from previously published laboratory studies. A methodology was also developed for determining k2 (the heterogenous oxidation rate constant) in the field. The results of field based monitoring of aeration cascades as well as batchwise CO2 stripping experiments conducted using waters of varying chemistry were combined with geochemical modelling to demonstrate the evolution of the chemistry in these systems over time. The aeration cascades were shown to remove approximately 50% of the dissolved CO2 initially present but this was not shown to have an appreciable effect on mine water treatability. Continued removal of the residual CO2 fraction by mechanical aeration resulted in the elevation of pH by up to 2 units. Trials of pilot scale Vertical Flow Reactors (VFR) at two sites in South Wales showed that rapid decreases in bed permeability over time make these systems unsuitable for deployment in the treatment highly net alkaline waters. As a result of adverse weather conditions and other technical difficulties there was insufficient data collected to determine the performance of these systems under net acid conditions. Qualitative observations suggest however that Fe removal was taking place at a significantly higher rate than would be seen in settling lagoons under the same conditions.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TP Chemical technology
Uncontrolled Keywords: Mine drainage; Iron oxidation rates; CO2 degassing
Date of First Compliant Deposit: 30 March 2016
Last Modified: 15 Dec 2017 09:14
URI: http://orca.cf.ac.uk/id/eprint/19120

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