Geobiotics - Innovators in Biooxidation Technology

GEOCOAT® Testwork

GEOCOAT® Testwork

GeoBiotics conducts testwork to demonstrate the amenability of a concentrate to the GEOCOAT® heap biooxidation technology, and to collect the process data necessary for plant design.

For the treatment of refractory gold concentrates, batch amenability tests are carried out in stirred reactors to establish the relationship between the extent of sulfide oxidation and the subsequent recovery of gold from the oxidized product by cyanidation. For base metal concentrates (copper, nickel, cobalt, zinc), batch amenability testing provides a measure of the relative rates of leaching of metals and an initial indication of the ultimate leach recoveries by complete oxidation of the sulfides.

At the next level of testing, the GEOCOAT® heap biooxidation technology is simulated in tall columns. The column charge, consisting of concentrated-coated support rock, is continuously irrigated with acid solution containing bacteria. The column is externally heated to a temperature appropriate for the type of microorganism being used. Columns inoculated with mesophilic bacteria are typically heated to 38-40°C, while columns inoculated with thermophilic Archaea are maintained at 65-70°C. Air is fed to the column to provide the oxygen necessary for the bacterial metabolism and for the sulfide oxidation reactions. Oxidation rates vary, but column tests typically run for 60 to 120 days. When testing refractory gold concentrates, the column charge is removed when oxidation is complete and the concentrate is separated from the support rock for cyanidation testing. The leaching of base metals from concentrates is followed by periodic analysis of the circulating solution. At the end of the test, the oxidized concentrate is weighed and analyzed to allow a final mass balance to be determined.

In some cases, a third level of testing, involving the construction and operation of a large-scale demonstration heap, may be required. This is most conveniently carried out at the mine site where the necessary concentrate and other resources are available. A heap, containing 100 to 1,000 tonnes of concentrate, is constructed and operated under typical production conditions. The data collected is used for process and engineering design. Tests may also be carried out in "cribs" which are large, lined and insulated bins. Because of the site- and project-specific nature of these tests, details must be worked out in consultation with GeoBiotics and the client.

GeoBiotics conducts testwork at qualified, independent laboratories in South Africa, Australia, North America, and Chile.

A more detailed description of GEOCOAT® testing procedures can be found here.