A novel process for sorting fine-sized sulphide minerals by biocoagulation

Based on a process design idea, investigations at Technical University of Berlin confirm that the biocoagulation of microorganisms and solid particles would be a new method to generate coarser particles suitable for sorting. The procedure of selective biocoagulation of microorganisms, e.g. yeasts like Saccharomyces cerevisiae and Yarrowia lipolytica respectively, and micro-dispersed solids, e.g. minerals like galena and sphalerite, has been analyzed as a basis for a novel sorting process. Therefore, especially the characteristics of the cell surface of the microorganisms, e.g. the electrostatic charge and the composition of extracellular polymeric substances, as well as their influence on the selective biocoagulation were studied. Experimental investigations show that the microorganisms and the sulphide particles below 10 µm coagulate effectively. Furthermore, the flotation is suitable for the separation of the selectively formed biocoagulates. With the designed column flotation, satisfying recovery rates are reached.