Abstract: A process for leaching low sulphur content ores to release metal values employs two operational steps. In the first step fine, rod-milled elemental sulphur is preconditioned with sulphur oxidizing bacteria which may include Thiobacillus, in an agitated reactor with water. Sulphur produced by this preconditioning process is added to the ore heap during a typical agglomeration process used to adhere small ore particles to the large particles, which increases the permeability of the ore heap. The sulphuric acid produced during the sulphur preconditioning process can be added to the heap during agglomeration as well as by adding some of the acid to the leach solution reservoir. This process results in a homogeneous distribution of the sulphur in the heap so that acid will be produced at the reactive mineral sites and will be consumed immediately, thus maintaining a low acid concentration and a low driving force for the acid/gangue reactions resulting in overall lower acid consumption.

Abstract: This application relates to an improved method for oxidizing multimetallic sulphide ores and concentrates, using a combination chemical/biological leaching process and at least three different types of bacteria. The treatment process for multi-metallic ores such as arsenopyrite can be made to work rapidly and to as much as 98% sulphide oxidation, when the finely ground ore or concentrate is leached in agitated, air sparged tanks, with strains of three different bacteria, T. thiooxidans, T. ferrooxidans, and Leptospirillum ferrooxidans. L. ferrooxidans is quite similar to T. ferrooxidans and obtains its energy for growth from the oxidation of ferrous iron. The process of the invention may conveniently be a continuously operating process utilizing more than one stage. Most of the chemical/biological action using the bacterium T. thiooxidans preferably takes place in the first stage, while in the subsequent stages the activity of T. thiooxidans is decreased in favor of the activity of the bacteria T.

Abstract: This application relates to an improved method for oxidizing multimetallic sulphide ores and concentrates, using a combination chemical/biological leaching process and at least three different types of bacteria. The treatment process for multi-metallic ores such as arsenopyrite can be made to work rapidly and to as much as 98% sulphide oxidation, when the finely ground ore or concentrate is leached in agitated, air sparged tanks, with strains of three different bacteria, T. thiooxidans, T. ferrooxidans, and Leptospirillum ferrooxidans. L. ferrooxidans is quite similar to T. ferrooxidans and obtains its energy for growth from the oxidation of ferrous iron. The process of the invention may conveniently be a continuously operating process utilizing more than one stage. Most of the chemical/biological action using the bacterium T. thiooxidans preferably takes place in the first stage, while in the subsequent stages the activity of T. thiooxidans is decreased in favour of the activity of the bacteria T.

Abstract: Bacterial cultures of T. thiooxidans, T. ferrooxidans and L. ferrooxidans used to oxidize multimetallic sulfide ores are first adapted to high dissolved arsenic concentrations and low pH by subjecting the cultures in a solution containing dissolved arsenic, to successive incremental concentrations of arsenic while operating in a continuous mode.

Abstract: A process for leaching copper from copper sulphide containing ore, in particular copper from chalcopyrite containing ore, is provided. The ore is preferably initially ground up and mixed with an aqueous acid leaching medium containing sulphide oxidizing bacteria, and a bacterial nutrient, and a catalytic amount of silver. Provision is made in the bacterial nutrient for a source of carbon dioxide and oxygen for the bacteria, both of which may be supplied by means of sparging with carbon dioxide enriched air. A bacterial compatible acid is added initially to the ore and leaching medium mixture and periodically during the process so that sulphide in the copper sulphide is oxidized in stoichiometric amounts to elemental sulphur. During leaching the oxidation potential is maintained between about 0.54 to 0.66 volts, most readily by initial addition of thiosulphate and dissolved copper.