Biocoagulation as part of a new technology for separation of fine particles
Jana Pinka
Technical University Berlin, Mechanical Process Engineering & Solids Processing
Microbes can enrich or degrade particles Figure 1: Process design
due to different charges of particles and
microbes. This fact is exploited in microLoading by
Biocoagulation
biological separation processes like bioaccumulation, bioprecipitation and bioSorting by
sorption. Such processes are used to ree.g. Flotation
cover metals, either valuable or nuisance,
from bleeds and effluents from bioleachSeparation by
e.g. Washing
ing operations and other hydrometallurgical treatments. Still, the transport of partiSorting products
Microorganism
cles by microbes is not well-investigated
[1]. Biocoagulation new technology for
making extremely fine-grained particles
collectible, and differs from well-known processes like biosorption [2], bioaccumulation and
biotransformation: In biocoagulation the particles are very small and solid. For the other processes, the minerals dissolve and the ions are adsorbed or accumulated.
Mikroorganismus
Sortierprodukte
The investigations follow three major directions (figure 1): Firstly, the different behaviour of
particles, minerals and microbes, in electrolytes is used. Between the electrolyte and the particle surface, a transition of charge carriers (electrons, ions) often takes place. Thereby the
charge carriers can migrate into the liquid phase or vice versa - adsorb to the solid phase. Because of the enrichment of charge carriers, an electrochemical bilayer originates consisting of
a relatively fixed layer (Stern Layer) and a more diffuse layer (Gouy-Chapman-Layer). The
Electrokinetic
potential of the shearing layer in direction
Potential 
to the neutral solution is called zetapotential. Different zeta-potentials at the
surfaces of minerals and microbes are
connecting the minerals and microbes
into clusters.
Measurements of the zeta-potential were
performed to find the best conditions for
coagulation of the model minerals Galena
and Sphalerite and the yeasts Saccharomyces cerevisiae and Yarrowia lipolytica.
Distance r
Saccharomyces cerevisae
Figure 2: Potentials of the electrochemical bilayer. The
charge carriers may be the metal ions one wants to collect
Sphalerite
The yeasts were cultivated, gathered and provided for coagulation tests. Microscopic studies demonstrate the adhesion of the sulphidic
minerals onto the yeasts’ surface.
[1] Bowen et al. (2001) J Colloid Interface Sci. 1, 237,
54-61
[2] Strouhal et.al. (2003) Bioelectrochemistry 60, 29-36
15.02.2016
Yarrowia lipolytica
Figure 3: Microscopic pictures showing different yeasts
adhering to the model mineral Sphalerite