Material size distribution in concurrent bio-leaching and precipitation: Experimental procedure and modelling

Abstract : This study presents the approach used to develop a model for a continuous bioleaching system in stirred tank reactors. In bioleaching of metallic sulfides, precipitation concurrently occurs with dissolution of sulfides. Therefore, the model incorporates both the leaching and the precipitation kinetics. It is based on a shrinking particle model for the leaching part and a Mixed Suspension Mixed Product Removal (MSMPR) crystallizer model with germination and growing kinetics for the precipitation part. To establish the model, it was necessary to have access to the size distribution of both sulfide and precipitated particles. A procedure for the bioleached residue characterization was developed in the BRGM laboratory to be able to dissociate sulfide and precipitated particles in the solid phase. The current paper presents the analytical procedure, the mathematical model in detail and its application to a continuous pilot plant test.