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Strategies for Reduced Acid and Metalliferous Drainage by Pyrite Surface Passivation
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Minerals 2017, 7(6), 89; https://doi.org/10.3390/min7060089

Control of Acid Generation from Pyrite Oxidation in a Highly Reactive Natural Waste: A Laboratory Case Study

1
Natural and Built Environments Research Centre, School of Natural and Built Environments, University of South Australia, Mawson Lakes SA 5095, Australia
2
Future Industries Institute, University of South Australia, Mawson Lakes SA 5095, Australia
3
Levay & Co. Environmental Services, Edinburgh SA 5111, Australia
4
Blue Minerals Consultancy, Middleton SA 5213, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Liliana Lefticariu
Received: 28 April 2017 / Revised: 23 May 2017 / Accepted: 25 May 2017 / Published: 30 May 2017
(This article belongs to the Special Issue Biogeochemistry of Acid Mine Drainage)
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Abstract

Laboratory kinetic leach column (KLC) tests were carried out to define the conditions required to control acid generation from a highly reactive, potentially acid-forming (PAF) iron ore waste rock. It was found that lime addition (0.1 wt % blended) plus either blending of silicates (25 wt % K-feldspar and 25 wt % chlorite), or addition of a non-acid forming (NAF) top cover containing about 10% dolomite (PAF:NAF = 5:1 wt %), when watered/flushed with lime-saturated water, greatly reduced acid generation as compared to the control KLC (PAF alone, watered/flushed with Milli-Q water), but did not result in circum-neutral pH as required for pyrite surface passivation and effective acid and metalliferous drainage (AMD) mitigation. In contrast, the combined use of these treatments—blended lime and silicates with an NAF cover and watering/flushing with lime-saturated water—resulted in leachate pH of 12 (up to 24 weeks). Mass balance calculations for Ca2+ and scanning electron microscopy (SEM) analyses suggest that calcite or gypsum may have formed in the NAF-amended KLCs and lime with added silicate KLC. Although the combined approach in the form trialled here may not be practical or cost-effective, control of a highly reactive natural PAF waste by pyrite surface passivation appears to be possible, and an improved treatment methodology (e.g., slightly increased lime blending without the need for further lime watering/flushing) could usefully be examined in the future. View Full-Text
Keywords: at-source AMD remediation; kinetic leach column; NAF cover; pyrite surface passivation; reactive silicates; secondary minerals at-source AMD remediation; kinetic leach column; NAF cover; pyrite surface passivation; reactive silicates; secondary minerals
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Zhou, Y.; Short, M.D.; Li, J.; Schumann, R.C.; Smart, R.S.C.; Gerson, A.R.; Qian, G. Control of Acid Generation from Pyrite Oxidation in a Highly Reactive Natural Waste: A Laboratory Case Study. Minerals 2017, 7, 89.

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