Unlocking the potential of sustainable bioleaching: evaluating microbially induced metal recovery in copper-bearing black shales

Some of deposits parameters, such as lower grade or peculiar composition (i.e. refractory phases, organic compounds) hinder their effective processing for metal recovery. However, bioleaching-based methods could support metal extraction from materials showing either poor metal content or complex mineralogy. In this study, two distinctly different samples of Kupferschiefer shale (LG – with low copper content, HG – organic-rich with high copper content) were examined in terms of metal bioleaching using two bacteria: Acidithiobacillus thiooxidans and Pseudomonas fluorescens. For LG sample, activity of P. fluorescens supports high extraction of Cu and Mo, while A. thiooxidans supports As extraction. For HG sample, activity of A. thiooxidans and P. fluorescens resulted in poor copper recovery of 1.8% and 7.26%, respectively. Alteration on shale surfaces were specific to the applied microorganism, revealing different features of post-leaching sulfides.