Bio hydrometallurgical recovery of metals from Fine Shredder Residues

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. This concentrate has been produced by physical treatment of Fine Shredder Residues derived from a shredding plant processing a mixed feed of metallic scraps, waste electric equipments and end-of-life vehicles. Bacterially assisted leaching experiments have been carried out using a copper-adapted consortium of mesophilic bacterial strains. The influence of various operating conditions such as stirring speed, temperature (25–50 °C), pulp solids density (5–20%) and initial iron concentration (0–15 g/L) has been studied. Temperature and stirring speed have proved to be the most influential parameter regarding copper dissolution kinetics, while pulp solids density and initial iron concentration have been found to have a subordinate importance. In optimum conditions, 95% extractions of zinc and copper were achieved within 48 h. Bacterial presence has been found beneficial in terms of catalysing copper dissolution.

► Bio hydrometallurgy should be regarded as a way to recycle polymetallic wastes.
► Very high copper recoveries have been achieved.
► Strong influence of temperature and agitation speed.
► Significant upgrading of precious metals, tin and lead in the leach residue.