Column bioleaching applications, process development, mechanism, parametric effect and modelling: A review

Bioleaching being an economically feasible process is considered as a potential alternative of hydro- and pyro-metallurgical processes of metal recovery. The process can be performed in shake flasks, batch reactors, continuous reactors, columns and heap. As the data and knowledge obtained from both column and heap bioleaching are often similar, the majority of successful small scale (shake flasks, batch reactors and continuous reactors) studies are scaled up to heap after the interpretation of the results in column studies and extrapolation, indicating the importance of column bioleaching. This review is the first in this domain, especially on column bioleaching, elaborating the process operation, applications and the various critical factors viz., ore pretreatment, column bioleaching set-up, microbial adaptation, pH, temperature, size fractions, microbial diversity, irrigation (flow) rate, process optimisation, rDNA technology, etc. affecting column bioleaching. Further, the potential microbial types used in column bioleaching and their mechanism of action have been extensively discussed. The modelling feature to determine bioleaching controlling steps, maximum metal dissolution rate, and additionally a glimpse challenges and future prospects of column bioleaching have been represented.