Search CRC LEME :

powered by FreeFind

Publication Policy

Open File Report Series

OFRS Index


Regolith Maps

Annual Reports

Articles & Papers


Minerals Briefs

"Focus on Salt"

Other LEME Reports

Order Form

Open File Report 42

The sorption of gold and silver on soil minerals

Gray, D.J.

The sorption of Au and Ag was investigated by reacting synthesised Au and Ag complexes with a range of different soils. The systems used were Au and Ag in humic, thiosulphate, iodide and chloride solutions, and in a poorly complexed form.

Soils used were 4% Peat Moss - 96% Quartz, organic rich soil sample 1467, Fe oxide rich soil sample 1468, carbonate rich soil sample 1470, Fe oxide rich standard 7, Mn oxide rich Mount Keith Shaft, 44 m depth, and a Mn oxide rich segregation collected at Ora Banda. The solutions and soils were equilibrated together and the Au and Ag concentrations in the soil solutions were measured at two weeks and again at three months.

Gold and Ag thiosulphates had a high initial solubility when contacting most of the soils, with the exception of the Mn rich soils, which quickly sorbed most of the Au and Ag. In general, both Au and Ag had similar solubilities in thiosulphate solution. When finally sorbed, Au did not redissolve.

In an acidic chloride-rich solution Au was more readily sorbed than Ag, only having an appreciable solubility when in contact with the most Mn rich material. This contrasts with the results for thiosulphate complexes, demonstrating the critical importance of the Au complex on the extent of sorption. Results were similar for Au iodide.

Humate complexes were found to maintain only small concentrations of Au in solution, suggesting a weak interaction between Au and humate. This is in contrast with work on Au humate interactions by other workers which has suggested that humate can be very effective at dissolving Au.

An important observation is the ability of the soils to redissolve Au. When the uncomplexed Au and Ag were mixed with the various soils they were quickly sorbed. After three months, however, a number of the mixtures contained significant quantities of dissolved Au (but not Ag). This is possibly due to soluble species with a high affinity for Au being produced by biological activity. Very similar effects were also observed for Au iodide. The humate mixtures also showed appreciable redissolution of Au, though in a different manner to the uncomplexed and the iodide mixtures, possibly due to the different types and concentrations of organic matter in the humate mixtures. These results suggest that Au is readily mobilized in soils, and this metal should be considered to be mobile under such environments.

Last updated: Thursday, January 06, 2000 08:33 AM


Cooperative Research Centres Australia

About Us | News & Events | Research
Publications | Education | Staff Only | Links

Contact Us | Disclaimer | Sitemap
© CRC LEME 2004

CRC LEME is established and supported under the Australian Government's Cooperative Research Centres Program. The CRC Program is an Australian Government initiative which brings together research groups with common interests.

CRC LEME Core Parties