How does bioleaching start?

Discrete particle size fractions of a zinc sulphide ore were bioleached in stirred tank reactors operated in batch mode. Kinetic analyses of these tests revealed that the leaching process was divided into two stages: (1) a period of colonization of the ore by bacteria, and (2) a steady rate period where the reaction could be described by classical shrinking-core kinetics. The colonization period itself could be described by classical bacterial growth kinetics and followed the logistic equation. The bacterial colonization rate constant was a function of the available zinc sulphide mineral surface area and could be described by classical Monod-type kinetics. The steady reaction rate constant was also a function of the particle size and fractional zinc content.