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- Hylander, Lars D., et al.
(författare)
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Comparison of different gold recovery methods with regard to pollution control and efficiency
- 2007
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Ingår i: Clean - Soil, Air, Water. - : Wiley. - 1863-0650 .- 1863-0669. ; 35:1, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- This case study performed at the largest gold mining village in the Philippines compares four methods for gold recovery: amalgamation, cyanide leaching, a shaking sluice, and Cleangoldm sluices. The results show that a combination of manual panning or Cleangoldm sluices followed by cyanidation is the best solution under present conditions, followed by cyanidation alone. Based on the knowledge obtained, remarks on suitable policy actions, which may be applied also in other gold fields, are made.
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| 2. |
- Hylander, Lars Daniel, 1954-, et al.
(författare)
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Consequences of a soaring gold price for gold producing countries and the global environment.
- 2009
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Ingår i: Securing the Future and 8<sup>th</sup>ICARD. - Skellefteå. ; , s. 67-68
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The presently soaring gold price adds to hazards threatening the sustainability of fishing and agriculture as means of support to living. This is by increased gold mining and related emissions of mercury and cyanide into the environment. Amalgamation, practiced in more than 50 countries, results in that metallic Hg is emitted to air, soil, and water and subsequently transformed to very toxic methyl-Hg and bio-accumulated in fish. Thereby, this highly nutritive feeding source eventually is ingested and becomes a poison to man. Four methods for gold recovery: amalgamation, cyanide leaching, a shaking sluice, and Cleangold® sluices, were compared in a case study performed at the largest gold mining village in the Philippines. The results show that the amalgamation method is presently used on all ores, in spite of gold recovery rates of 10–35% of initial gold content of the ore. With a light microscopy and photomicrographs, we documented that the following factors contribute to the low recovery: small and occluded gold grains and gold grains with oxidized surfaces that do not amalgamate. As a consequence, the miners are sending all amalgamated ore tailings for cyanide leaching. This was the most efficient of the methods studied, recovering up to 95% of initial gold content. The Cleangold® sluices recovered more gold than amalgamation, although gravimetric methods have limitations on the actual specific ore. Therefore, a combination of manual panning and/or Cleangold® sluices followed by cyanidation is the best solution under present conditions, followed by cyanidation alone. The used cyanide solution must be properly handled to not threaten the food security. Transition to less hazardous gold mining is urgent, considering that gold is a limited stored resource. Agricultural fields and fish populations are at the contrary fund resources, which will yield a return for an indefinite future if properly managed. Loans for investment in safe and efficient gold extraction technology, information and practical training of the miners, political and scientific guidance of the informal mining sector, restrictions on Hg availability and on sales from industrialized countries are suggested to counteract the present worst case situation, where amalgamation is followed by cyanidation. This combination increases the bioavailability of Hg lost. into the environment.
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| 3. |
- Lücke, Sofie, et al.
(författare)
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Evaluation of a new method using magnetic sluices for mercury-free small-scale gold mining in the Philippines.
- 2006
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Ingår i: Abstracts of Eighth International Conference on Mercury as a Global Pollutant. - 1932078657 ; , s. 574-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Approximately 100 000 people are involved in small-scale gold mining a in the Philippines. They mainly use the amalgamation and/or cyanidation processes. The use of mercury started in the 1980’s, when the price of gold went up. The workers live in thesame place as they work, they do not use safety equipment and the tailings are generally left anywhere. The concentrations of mercury in drinking water, soils, sediments, tailings and fish near gold mining operations exceed in general national and international limits.The aim of this study was to evaluate a new method for gold recovery, suitable for smallscale miners and in which mercury, cyanide or other chemicals are not used. Interviews with some miners were also performed in order to understand the complex situation from a miner’s perspective and evaluate the possibilities to improve the situation. The gold separation method, Cleangold (US patent granted in July 1999, #5,927,508) is developedby David Plath, USA, and uses magnetism to create riffles in a simple sluice, for a physical separation of gold from grains with lower density. The study was performed at five different sites in the Philippines (Diwalwal, Mainit, Acupan, Balatoc and Paracale).The gold recovery from the different sites varied both between and within the sites. The highest recovery was obtained in Balatoc (73%) and the lowest in Acupan with a top value of 15%. In comparison, the recovery using the amalgamation method is generally between 25 and 50% at the sites and at cyanidation estimated to approximately 90%. The chances of reducing the use of mercury are large, for example by adding mercury in the final step only, while panning, in case the magnetic sluices cannot completely replace amalgamation. In conclusion: the miners want and need a change. The obstacles for development are lack of technology and knowledge, unstable economy, habits and the fact that mercury and cyanide are easily accessible on the market. Further, for development and adaptation of environmentally benign methods, stricter control/legislation and accessible loans/micro credits to the miners are important. Industrial countries could play an important role by transferring appropriate knowledge rather than mercury.
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