A new strategy on biomining of low grade base-metal sulfide tailings.

• The ratios of ferrous and sulfur oxidizers on tailings biomining were studied. • EPS components were analyzed by 3DEEM- PARAFAC for the first time. • L. ferriphilum played a major role in the biomining by the mixed cultures. • The mineral surface was barely covered by secondary minerals during bioleaching. • A new strategy for biomining of low grade base-metal sulfide tailings is proposed. This study investigated the effect of designed microbial consortia on biomining of low grade base-metal sulfide tailings. The results show the amount of recycled metals were equal if the tailings were leached by mixed cultures of Leptospirillum ferriphilum and Acidithiobacillus thiooxidans at three different ratios or by pure culture of L. ferriphilum , which was better than the pure culture of Acidithiobacillus ferrooxidans. qPCR (quantitative polymerase chain reaction) demonstrated only L. ferriphilum functioned in the mixtures at initial stage. The results of extracellular polymeric substances (EPS) via three-dimensional excitation-emission matrix combined with parallel factor analysis (3DEEM-PARAFAC) collected from mixed or pure cultures indicated there were no interactions between two strains. Secondary minerals were formed, but did not influence the leaching process. A new strategy for tailings biomining was proposed: only ferrous oxidizers should be added during the initial and middle biomining stage, while sulfur oxidizers should be added at the end. [ABSTRACT FROM AUTHOR]