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Mercury decontamination in the Philippines

GEUS - Internationale udviklingsprojekter.
Philippines on globe Philippines*

In 2001, a report from the Department of Health in Manila documented a yearly release of 140 tons of mercury from two small scale mining communities on the island of Mindanao. In 2007, further investigations by GEUS discovered mercury releases from yet two other small-scale mining communities of Mindanao in the order of 5 tons per year. Extrapolated to all small-scale mining communities of the Philippines, these figures suggest, that 200 to 500 tons of mercury is being released annually into the environment.

The reason for this massive release from small-scale mining, is that mercury is added to gold ore in the grinding process. Prolonged grinding of mercury produces mercury flour which cannot coalesce and thus cannot be recovered by the miners, and it ends up in the tailing dams. Sampling of tailings showed mercury contents up to 420 gram per ton. Large amounts of gold are trapped in the mercury flour and this gold is unrecoverable, a major loss since gold contents up to 16 gram per ton have been measured in the tailings.

Most of the released mercury throughout the Philippines is hosted in the gold miners' tailing dams that unfortunately are not properly secured. With time, the contents of these leak into the sea, where mercury will pervade the mangrove swamps that fringe the Philippines. These swamps serve as hatching grounds for fish and shellfish, the main source of protein for the Philippine population.

How can mercury and gold be extracted from the tailing dams?

Tailings "secured" by plastic sacks
Tailings "secured" by plastic sacks
Extracting mercury from the vast tailing dams is not an easy task and no standard method is available. One possibility is to test whether a so-called State Battery can solve the problem. This was invented in the nineteenth century by the Australian government as a tool to help gold miners in the extraction of mercury and gold from their ore. A similar gadget was used in California during the gold rush in the 1800's and fairly recently in Venezuela for clean-up of mercury spills.

 

State Battery
State Battery
A State Battery is a fairly simple construction involving of a number of copper plates stacked above each other in such a way that a mixture of tailings and water can run from one plate to the next (see figure below). The copper must be covered by a thin film of mercury and the water-tailing mixture should run slowly from one plate to the next. The mercury flour is supposed to stick to the mercury film on the copper plates. The process needs to be repeated several times. With regular intervals the mercury film will be scraped off the plates and distilled in order to recover the gold in the mercury.

If this process is successful, such State Battery plants have the potential to clean tailing dams of their mercury content throughout the Philippines. The whole operation will probably be cost neutral or it may even create a substantial profit from the gold that can be recovered along with the mercury.

In September 2010 tests were carried out during which a spiked tailing with 2700 ppm mercury was passed through a State Battery After two runs the mercury content was down to 12 ppm.

Stakeholders
Project support: Sumitomo Foundation in Japan and GEUS.
Project period: 1st December 2009 to 30th November 2011.
Partners: Metals Industry Research and Development Centre, Philippines; Department of Geology, University of the Philippines; Department of Science and Technology, Manila and Japan Atomic Energy Agency, Tokai.

References
GEUS report 2011/127: Cleaning mercury polluted mine tailings in the Phillippines (pdf-file ~4mb)
GEUS report 2007/35: Training of Small Scale Miners - Philippines
Videnskab.dk: Gigantisk kviksølvkatastrofe truer Filippinerne

Contact:
Peter W. U. Appel
Senior research scientist
E-mail: pa@geus.dk
Telephone: +45 3814 2214

 
Mercury decontamination in the Philippines