Monday, 10 July 2017

The role of biohydrometallurgy in the sustainable development of mineral resources

Over the past 40 years, biohydrometallurgy has been recognised increasingly as an emerging technology for extraction of metal values from recalcitrant minerals, low grade ores or mineral resources carrying penalty metals.  This has led to the development of commercial tank and heap leaching processes, processing concentrates and crushed ores to liberate metals of interest through bioleaching of base metals and biooxidation to enable subsequent recovery of gold and PGMs.  The potential of in situ leaching of mineral reserves is under consideration with biohydrometallurgy of key interest owing to the potential for ongoing regeneration of leach agents. 
Processes based on biohydrometallurgy have potential to deliver environmental benefits over competing extraction approaches and to enhance the degree of extraction from the overall resource. While many of the commercial applications of biohydrometallurgy for recovery of metal values use solvent extraction and electrowinning for metal recovery, the importance of biohydrometallurgy in the recovery of metals or, mainly, the removal of metals from aqueous solutions has been considered from the environmental perspective through, for example, biological sulfate reduction with associated metal precipitation. 
Currently, the recognition of the relevance of biohydrometallurgy in a broader context is growing.  Key aspects include the need to account for unintentional bioleaching reactions on the disposal of waste rock and tailings and the need for the long term prevention of such reactions to enable appropriate handling of waste rock and restoration and rehabilitation of prior mine sites with associated protection of water resources.  Further, limited global resources of key metals highlight both the need to process mineral resources of decreasing grade, smaller size of deposit and increasing complexity and the ability to extract metals from secondary sources for re-use.  In the former, biohydrometallurgy has potential to expand technological approaches.  In the latter, with an increasing focus on the circular economy, the sources of metals or modern-day ‘ores’ are changing to include secondary resources such as waste electrical and electronic equipment (WEEE) and municipal solid waste (MSW). These present new challenges for biohydrometallurgists. 
Prof. Sue Harrison
Next year in Namibia, MEI has two important conferences back to back, Biohydromet '18, followed by Sustainable Minerals '18. On the final morning of Biohydromet '18, Prof. Sue Harrison, Head of the Centre for Bioprocess Engineering Research, at the University of Cape Town, will present a keynote lecture on the role of biohydrometallurgy in the sustainable development of mineral resources, highlighting the contribution of and challenges for biohydrometallurgy in sustainable development of mineral resources, and consideration of the supply of key metals with the goal of maximising resource efficiency while minimising environmental burden.
Prof. Harrison, who is also an MEI consultant for biohydrometallurgy, has some 20 years experience in research in bioprocess engineering, gained in the industrial and academic arenas, and she collaborates actively with researchers at the Universities of Mumbai, Cambridge and Imperial College London and with companies in South Africa and abroad. Since her appointment to the UCT academic staff in 1991 more than 40 MSc and PhD students have been awarded research degrees under her supervision. She was awarded the South African DST Research Chair in Bioprocess Engineering, with effect from 2008.

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