A better way to treat mercury-waste

The US Department of Energy's Brookhaven National Laboratory has licensed its mercury-waste treatment technology to Newmont Technologies Limited, an affiliate of Newmont Mining Corporation, the largest gold producer in North America.

Brookhaven's technology chemically stabilises and solidifies liquid elemental mercury, a by product of gold mining, to safely isolate the material from the environment.

The license gives Denver-based Newmont exclusive rights for mining applications under a pending patent application filed by Brookhaven to protect the technology. Newmont will work with Brookhaven researchers to scale-up the technology for industrial use and afterwards will offer sublicenses to other mining operations around the world.

In Brookhaven's process, called Sulphur Polymer Stabilisation/Solidification (SPSS), toxic liquid mercury is mixed with sulphur-polymer cement and small amounts of additives in a heated vessel until all the mercury is converted into mercuric sulphide, a compound that has low solubility and low vapour pressure. The thermoplastic mixture is then melted to form a homogeneous mixture and poured into a mould in which it cools and solidifies. This solid waste form immobilises the mercury so that it exceeds stringent Environmental Protection Agency standards for leaching.

'Incorporating the mercury into a solid form is an important part of our method, ' said Paul Kalb, Brookhaven's principal researcher on this project. 'Conventional amalgamation also chemically stabilises mercury, but it transforms the element into a dispersible powder, which is more accessible for human exposure and can be easily mobilised by wind and groundwater. Our method makes mercury easier and safer to handle and to dispose of, and it isolates the toxic metal from the environment.'

The SPSS process is based on a patented mixed-waste treatment technology developed at Brookhaven in 1997. Mixed waste consists of metals and/or chemicals as well as radioactive materials. The work, as well as development of the new method for mercury stabilisation, was funded by the U.S. Department of Energy.

In the past, gold-mining companies and other industries sold by-product, elemental mercury for industrial use. The industrial use of mercury has declined, however. In the US, it has fallen from 2,000 tons per year in the 1980s to less than 50 tons per year today. Brookhaven's new technology should make disposal of the excess mercury practical and safe.

For all other non-mining fields of use, Brookhaven Science Associates, the management company that operates Brookhaven Lab, will offer licenses for SSPS, and these licenses will include the results of ongoing production scale-up engineering studies.