Spent NiMH batteries are important secondary sources of different REEs that also contain significant quantities of valuable base metals such as Mn, Ni, Co, Fe, Al, and Zn. REEs are critical metals with high economic importance that suffer from an imminent risk of supply depletion.
“The low-cost and sustainable recycling of REE containing waste materials, such as used NiMH batteries, is very important. In this way, environmental and supply issues related to the extraction of rare earths from natural resources can be resolved, while at the same time making a significant economic profit,” says Payam Rasoulnia.
In his dissertation, Payam Rasoulnia used bioleaching approach to enable efficient REE and base metal extraction from spent NiMH batteries. To reach this goal, he developed an ecological engineering strategy for high-rate and -yield continuous production of the bio-based leaching agent (gluconic acid) under non-aseptic conditions.
“The developed biological system was highly contaminant resistant, and the gluconic acid production rates were one of the highest so far reported. By stepwise optimisation of the process parameters, the total REEs extraction yield from the spent NiMH batteries increased by almost a factor of five,” he says.
The obtained base metal and REE leaching yields were considerably higher than the earlier reports for such materials. These achievements represent a major leap forward in the field of heterotrophic bioleaching.
Public defence on Friday 15 September
The doctoral dissertation of MSc (Tech) Payam Rasoulnia in the field of Environmental Engineering titled Heterotrophic Bioleaching of Rare Earth Elements and Base Metals from Spent Nickel-Metal-Hydride Batteries will be publicly examined at the Faculty of Engineering and Natural Sciences at Tampere University at 12:00 on Friday 15.09.2023 at Hervanta Campus, Festia Building, Pieni Sali 1, FA032 (Korkeakoulunkatu 8, Tampere). The Opponent will be Doctor Katrin Pollmann from HZDR, Helmholtz Institute Freiberg for Resource Technology, Germany. The Custos will be Professor Jaakko Puhakka from the faculty of Engineering and Natural Sciences, Tampere university.
Photo: Maria Mostafazadeh