Mineralogy of mine wastes and strategies for remediation
Published:January 01, 2012
The release of acid mine drainage (AMD) from mines and mine wastes is an environmental problem of international scale. The AMD results from the oxidation of sulfide minerals and the release of acidity at rates that exceed the capacity of carbonate and aluminosilicate gangue minerals to neutralize the pH. Static testing protocols used to assess the potential for AMD generation are based on chemical characteristics, and generally do not consider the mineralogy of the waste materials. Static testing of pure minerals and samples of typical host rocks indicate that aluminosilicate minerals are unlikely to provide neutralization at rates that are sufficient to prevent the release of AMD in wastes containing more than a very modest sulfide content. The products of sulfide oxidation include a broad range of (oxy)hydroxide, sulfate and hydroxysulfate minerals. The most common of these secondary minerals are goethite, gypsum and jarosite. Covellite is common in wastes derived from copper deposits, and marcasite and elemental sulfur are common in waste deposits containing pyrrhotite. The mechanisms of abiotic and microbially mediated sulfide oxidation have been studied extensively. Microbiallymediated oxidation of acid-soluble sulfide minerals is initiated by the release of H2S, and follows the polysulfide pathway, whereas the oxidation of acid-insoluble sulfide minerals is initiated by oxidation by Fe(III) and follows the thiosulfate pathway. The paragenetic sequence for the oxidation of sulfide-bearing mine wastes has been defined. This sequence includes more extensive accumulation of elemental sulfur associated with wastes containing acid-soluble sulfide minerals. A variety of active and passive approaches exists for the remediation of AMD-generating waste-disposal sites. Although many of these techniques have been implemented at mine sites, other novel approaches are currently being evaluated. Passive treatment systems are desirable because of the lower costs associated with these systems and the long duration of AMD generation.
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Environmental Mineralogy II
In 1997, the European Mineralogical Union (EMU) began organizing a series of Short Courses (‘Schools’) with the associated publication of a series of review volumes (the ‘EMU Notes in Mineralogy’) on topics of interest to mineral scientists. The second School was held in Budapest in May 2000, along with the publication of Volume 2 of the Notes, on the then emerging subject of Environmental Mineralogy. This volume (edited by D.J. Vaughan and R.A. Wogelius) was well received and has sold well in the 12 years since it appeared (such that very few copies remain available for purchase). Given the continuing demand for books in this field, the President and Council of EMU approached the editors and asked them to consider several options. These were: (1) simply to reprint the original volume; (2) to produce a new volume using the original chapter authors as far as possible; or (3) to organize a new School and accompanying volume. It was decided to take the second of these options and to publish what might be thought of as a ‘second edition’, although the extensive revisions undertaken in what we have entitled Environmental Mineralogy II justify regarding it as a new book, and hence in making it ‘Volume 13’ of the Notes. The layout and organization of this new book follow closely that used in the old volume. I was delighted to find that the great majority of contributors to the earlier volume were keen to take on the job of producing a new, up-to-date chapter on their chosen subject. Again, therefore, the book consists of 11 chapters, eight of which retain the same authors, and two of which have added one author (Kevin Taylor joins Andy Aplin for Chapter 4, and Kath Morris joins Charles Curtis for Chapter 9). In the case of Chapter 3, the previous authors are no longer actively involved in the area of soil science, and the challenge of that topic area has been ably taken up by David Manning. All of the chapters were subject to external peer review and I wish to thank Nick Bryan, Linda Campbell, Hugh Coe, Ian Freestone, Barry Johnson, Francis Livens, Jon Lloyd, Richard Pattrick, Claire Robinson, Eva Valsami-Jones and Dave Wray for their help with this important process. At the same time, it should be emphasized that any errors and imperfections that remain in this volume are solely the responsibility of the authors and editors.