Geochemical evaluation of heap rinsing of the Gold Acres Heap, Cortez joint venture, Nevada

Bowell, R. J.; Parshley, J. V.; McClelland, G.E.; Upton, B.; Zhan, Guosheng

doi:10.1016/j.mineng.2008.12.012

Cited by 9 publications

(8 citation statements)

References 2 publications

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“…However, a key difference lies in the amount of cyanide used, and the timeframe over which this cyanide is used. Heap leaching requires the constant use of chemical over a timeframe of years (Bowell et al, 2009) where the purpose of cyanide use is to leach gold through the rock pile. Phytomining requires the use of cyanide once only, over a timeframe of minutes, where the purpose of the chemical is to promote sufficient solubility for uptake.…”

Section: Environmental Considerations Of Gold Phytominingmentioning

confidence: 99%

Gold phytomining. A review of the relevance of this technology to mineral extraction in the 21st century

Wilson-Corral

Anderson

Rodríguez-López

2012

Journal of Environmental Management

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Section: Environmental Considerations Of Gold Phytominingmentioning

confidence: 99%

Gold phytomining. A review of the relevance of this technology to mineral extraction in the 21st century

Wilson-Corral

Anderson

Rodríguez-López

2012

Journal of Environmental Management

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“…Many closure plans of the time incorrectly assumed that the 'pore volume' described in Cellan et al (1996), was the volume of void space within a heap or the volume of fluid required to saturate the spent ore, which is actually the definition of a 'bed volume' (Bowell et al, 2009). In fact, the definition of 'pore volume' used in Cellan was the metallurgical definition, which defines void space within the particles of a solid mass, but not the void space between the particles (Figure 1).…”

Section: Early Closure Regulationsmentioning

confidence: 99%

“…Other constituents are likely to remain in heap drainage solutions after concentrations of cyanide compounds have decreased, and may even increase through rinsing because the pH-redox state of heap solutions will ultimately determine the chemistry of drainage from a heap, and long-term rinsing of spent heap ore is likely to alter the pH-redox conditions in the heap (Bowell et al, 2009). This can result in the release of constituents though desorption and dissolution of previously stable constituents ( Figure 2).…”

Section: Heap Solution Chemistrymentioning

confidence: 99%

“…As an example, a column rinsing test conducted on Gold Acres heap material revealed the presence of leachable metals and metalloids as soluble salts stored in the material (Bowell et al, 2009). Results of the field rinsing test indicated rinsing the Gold Acres Heap with recirculated barren solution does not have any benefit in decreasing the solute load of the heap.…”

Section: Heap Solution Chemistrymentioning

confidence: 99%

“…In the two decades since the first modern gold heap leach facilities were closed, the approach to closure of heap leach pads has evolved considerably. In particular, rinsing of leach pads, initially considered an integral part of heap closure, has since become recognised as generally unnecessary, and often a waste of valuable water resources (Bowell et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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The evolution of cyanide heap leach closure methods

Parshley¹,

Willow²,

Bowell³

2012

Proceedings of the International Conference on Mine Closure

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The last two decades have seen a significant evolution in the approaches used to close gold heap leach pad facilities in an environmentally responsible manner. With the promulgation of new cyanide regulations in the State of Nevada, USA in 1989, the mining industry was faced with the need to develop new methods to safely close cyanide heap leach pads in a manner that eliminated long-term risks associated with cyanide and other chemical constituents that could be discharged from the heap leach pads following closure. Initially, rinsing of the heaps was thought to be the only approach to reduce concentrations of cyanide, and this was reflected in the new regulations as a requirement to rinse heaps, unless other methods could be demonstrated to adequately stabilise the spent ore and solutions. However, the regulations were unclear as to when closure of the heap began and if circulation of process solutions, after cyanide addition ceased, constituted rinsing. Many closure plans developed during the early years immediately following promulgation of the new regulations assumed that rinsing would be done with fresh water in quantities of up to three times the total pore volume of the heap based solely on the results of a study published in 1996 (Cellan et al.). If implemented, this would result in the consumption of significant quantities of clean water in a region where water resources are limited, and the benefits of freshwater rinsing were not always apparent. Rinsing heaps during closure also generated large quantities of additional "process" solutions that required management through other methods, such as forced evaporation, or chemical or biological treatment. By the late 1990s, the mining industry had closed enough heap leach pads to allow review of ideas and to use this to make changes in the regulations and approaches employed by the industry. A better definition of when heap closure begins was needed. The currently accepted criterion for closure was after economic gold recovery ceases. Continued research on this led to the demonstration for closed heaps that additional rinsing after the residual gold recovery period is often not needed to reduce cyanide risks from the heap drainage because the more toxic forms of cyanide volatilise and other deleterious elements become mobile as solutions are recirculated through the heap (Bowell et al., 2009). To address the shortcomings of heap rinsing as the primary method of chemical stabilisation of spent ore, a number of approaches were tried, and many of the early approaches were abandoned in favour of more practical and economic methods which were equally effective. This paper documents the history of heap leach closure approaches since the late 1980s and discusses the evolution of understanding and consequently the methods proposed to stabilise spent heap ore during closure. Data from several closed heaps are presented as illustrations of the progression of approaches to heap rinsing. Current trends in the existing best practice and their probable impact on the focus...

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