Hybrid leaching of tantalum and other valuable metals from tantalum capacitor waste

Asma Sikander, Steven Kelly, Kerstin Kuchta, Anika Sievers, Thomas Willner, Andrew S. Hursthouse*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


We propose a novel integrated model for the recovery of tantalum from tantalum-rich waste using a combination of hydrometallurgical and bio-metallurgical processes. To this end, leaching experiments with heterotrophs (Pseudomonas putida, Bacillus subtilis and Penicillium simplicissimum) were carried out. The heterotrophic fungal strain leached manganese with an efficiency of 98%, however no tantalum was detected in the leachate. An unidentified species did mobilise 16% tantalum in 28 days in an experiment with non-sterile tantalum capacitor scrap. Attempts to cultivate isolate and identify these species failed. The results of a range of leaching trials resulted in an effective strategy for Ta recovery. A bulk sample of homogenised Ta capacitor scrap was first subjected to microbial leaching using Penicillium simplicissimum, which solubilised manganese and base metals. The residue was subjected to second leach using 4M HNO3. This effectively solubilised silver and other impurities. The residue collected after second leach was pure tantalum in concentrated form. The hybrid model produced derives from observations from previous independent studies and shows that we can effectively recover tantalum along with silver and manganese in an efficient and environmentally friendly manner from tantalum capacitor scrap.
Original languageEnglish
Pages (from-to)59621-59631
Number of pages11
JournalEnvironmental Science and Pollution Research
Publication statusPublished - 3 Apr 2023


  • circular economy
  • critical material
  • WEEE
  • recycling
  • hydrometallurgy
  • biometallurgy


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