Abstract: The invention discloses a method of introducing microorganisms into a heap of material for bio-assisted heap leaching by prepraring microorganisms substantially without exopolymers on their external cell walls; adding such microorganisms to the heap; and re-activating the production of exopolymers on the external cells walls of the microorganisms in the heap. The invention also extends to a method of enriching the environment of microorganisms' embedded in a heap for bio-assisted heap leaching.

Abstract: The invention discloses a method of controlling a heap leach process through controlling an irrigation rate of a heap as a function of at least one of an aeration rate of the heap, a determination of advection at least at one predetermined point in the heap, and a determination of temperature at least at one predetermined point in the heap. Also disclosed is for the aeration to be forced and for the method to include the step of controlling the aeration rate as 10 a function of a determination of the oxidation rate of material within the heap. The invention also extends to a method for the introduction of microorganisms into the heap of material, a method for increasing the temperature of heap of material for heap leaching, a method of determining an optimum heap configuration for a bio-assisted heap leach process of an ore heap, and a method of enriching the environment of microorganisms embedded in a heap of material for bio-assisted heap leaching.

Abstract: A method of recovering nickel from a nickel bearing sulphide mineral slurry which includes the steps of subjecting the slurry to a bioleaching process, supplying a feed gas which contains in excess of 21% oxygen by volume, to the slurry, and recovering nickel from a bioleach residue of the bioleaching process.