Extracellular polymeric substances (EPS) from bioleaching systems and its application in bioflotation

The use of EPS-producing heterotrophic and chemolithotrophic bacteria in bioflotation processes have been investigated for the last two decades. These studies have mostly been confined to laboratory microflotation tests using pure cultures. In this study the use of EPS, extracted from bioleaching consortia, to float chalcopyrite was evaluated and key process parameters such as pH, flotation time and the concentration of collector, bacterial cells and EPS were optimised. Analyses of the EPS extracted from various bioleach systems indicated that the EPS consisted mainly of carbohydrates, proteins and uronic acids. Microflotation tests using free EPS yielded a chalcopyrite recovery of 77% when chalcopyrite was floated alone and 70% during the separation of a mixture of pure chalcopyrite and pure pyrite compared to 32% when using SIBX only. The results obtained suggested that the flotation of chalcopyrite could be significantly increased in the presence of EPS extracted from bioleaching populations.

Research highlights
► Determining the effect of bioleaching microorganisms and their EPS on chalcopyrite floatability.
► Parameters: collector, bacterial cell and EPS concentration, flotation time and pH were optimized.
► Biochemical analysis indicated the EPS consisted of carbohydrates, proteins and uronic acids.
► Chalcopyrite recoveries between 70–77% could be achieved using free EPS.
► This study demonstrates the potential use of free EPS as a bioflotation agent.