| 1. |
- 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. |
- Miranda, Conrado R., et al.
(författare)
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Mercury use and emissions in small-scale gold mining in southeastern Mindanao, Philippines and the need for intervention.
- 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
- There are several small-scale gold mining operations scattered throughout the Philippine archipelago occupying about 50,000 miners and mineral processors. The sites with the larger number of miners involved are located in Southeastern Mindanao, Philippines, particularly in Compostela Valley Province. Our objective is to relate observations made in relation to mercury use in small-scale gold mining in the Philippines. Although the useof cyanide has been introduced, mercury amalgamation for gold recovery is still, in a number of operation sites, the dominating method. Amalgamation tailings (aside from unprocessed ore) are generally further processed in a cyanidation plant because most gold is left after amalgamation. Amalgamation and cyanidation tailings are usually dumped into improvised, generally leaking, dams or directly in the surroundings. Mercury is thus released into the environment by direct disposal or seepage into rivers and unconfined blow torching of mercury amalgam. There is no complete record or inventory of mercury importation for use in small-scale gold mining operations. Amounts of mercury releasedare not documented and reliability of estimates is poor. Recovery and recycling of mercury has not been commonly practiced because the efforts are not commensurate to any large monetary savings, although there is presently an increasing interest in economizing mercury use as an effect of increased mercury prices. Records of high levels of mercury in sediments and waters within and downstream mining areas indicate significant releases of mercury. It has been estimated that 50 tons of mercury might have been released annually into the rivers in the Diwalwal gold-rush area, the largest smallscale mining operation in Mindanao, at the height of the gold rush from 1986-1988. Releases declined then to 26 tons annually, which was further reduced to 17 tons annually in the past two years. These emissions threaten the ecosystem as well as the workers and their families, also in communities downstream. Therefore education campaigns, global initiatives to restrict mercury availability and a continuous strict enforcement of existing regulations on mercury use must be prioritized to reduce theareas and the numbers of individuals affected by mercury pollution.
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