Pulps of 20% solids is prepared from -200 mesh pyrite concentrate (after froth flotation), and is inoculated with 5% (V/V) of adapted bacterial solution. The bioleaching tests is carried out in 250 ml Erlenmayer flasks, each contained about 220 ml pulp. The pulps is aerated with air bubbling at one liter per minute air flow rate, and is continuously
Extended freezing conditions exist in many parts of the world in the winter because of latitude or high altitude or both. Such conditions, coupled with the sprinkling techniques commonly used in heap leaching, result in formation of layers of ice which inhibit leaching by tying up solution
Some gold and silver ores are difficult to successfully heap leach because of the high percentage of clay, and/or fines which are intrinsic in the material or generated by the crushing or ore preparation. This type of ore can result in extremely slow percolation during heap leaching. Channeling can result which promotes dry areas within the heap,
It is feasible to conduct cyanide heap leaching at high altitudes as has been demonstrated by a number of pilot and commercial operations in the altiplano of the Andes Mountains. Operations at elevations in excess of 3000 meters (9800 ft) must be conducted with care to insure that heaps are fully permeable and the lixiviant solution does not become
There are locations on the west coast of South America, in Australia, and in the California internal desert where fresh water is practically unavailable. It has been found that precious metal dissolution can be accomplished in sea water or in strong brine provided the leaching environment is adjusted to compensate for the buffering characteristics
The previous tests demonstrated the use of facultative and extreme thermophiles for refractory sulfide gold ores and flotation concentrates. The following tests were conducted on carbonaceous gold ores to evaluate response to bioleaching.
Facultative Thermophile Bioleaching of Carbonaceous Gold Ore
The facultative thermophile S1I was used to pretreat a carbonaceous gold ore under CSTR conditions. This ore is
A few representative cycles from the first 20 oxidation/reduction cycles for a pyrite electrode in 0.1 M sodium borate are presented in Figure 3. The first scan was made in the cathodic direction starting from the rest potential of the mineral which typically had a value of 0.18 V. The large reduction peak observed in the first cycle shows the presence
The Gunnison, Colorado, tailings provide an example of the chemical reactions across the interface with soils rich in pyrite but low in calcite. In this case, the retardation of trace components is determined primarily from the Eh controls and less from the pH (Johnson, 1985). The compositions of groundwater from wells in the vicinity of the tailings
The dissolution of gold in ammoniacal solutions cannot take place in the absence of oxidants. Cupric ammine can act as an oxidant in this system according to Equation 3.
The effect of cupric ammine concentration on the dissolution rate of gold was investigated in a solution of 0.6 M total ammonia concentration (0.1 M (NH4)2SO4 and 0.4 M NH3). The