Studies for the optimisation of bioleaching of heavy metals from contaminated sediments from Reconquista River

Abstract

Bioleaching processes are effective for removing heavy metals from contaminated sediments, but optimising performance requires understanding interactions between microbial activity, sediment properties, and metal behaviour. Most studies emphasise metal solubilisation, often overlooking effects on the solid phase, particle movement, and metal reprecipitation. This study evaluates bioleaching in fixed-bed reactors, testing sulphur addition and bioaugmentation with native microbial strains. It examines relationships among microbial activity, metal mobilisation and reprecipitation, and changes in solid-phase characteristics. Results showed metals were mobilised from upper to lower reactor sections, where they accumulated. Although acidification occurred, it did not reduce pH throughout the column but significantly altered particle size, surface properties, and pore networks. Additionally, compaction from drainage and movement further influenced metal mobility and speciation. Modifying reactor geometry - favouring shallower designs with larger surface areas - could improve performance by enhancing drainage, microbial distribution, and metal recovery. These findings highlight the importance of physical changes during bioleaching.