Evaluation of two-step processes for the selective recovery of Mn from a rich Mn residue

S. Maryam Sadeghi, Carlos M.H. Ferreira, Helena M.V.M. Soares*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)


In this work, effective two-step processes for recovering manganese (Mn), as well as zinc (Zn), from a rich Mn residue, that mainly consists of Mn and carbon with lesser amounts of Zn and Fe, are proposed. First, three different methods (conventional, ultrasound- and microwave-assisted) were evaluated for reductive acid leaching of the residue. Subsequently, two different strategies for purification of Mn from the leachate were considered: oxidative precipitation of Mn with persulfate and solvent extraction with Cyanex 302 as the extractant. The results showed that microwave-assisted leaching was the most effective in terms of the percentage of metal leached (with 98 and 100% of Mn and Zn, respectively) as well as the effectiveness of time and reagent consumption. Both Mn purification strategies were effective; with the oxidative precipitation, a 99.7% pure MnO2 precipitate and 3.30 g/L Zn solution with a purity of 99.9% were obtained at a global yield of 97.4 and 94.8%, respectively. Solvent extraction resulted in a 32.6 g/L Mn solution with a purity of 99.9% and 35.2 g/L Zn solution with a purity of 98.4%, with global yields of 96.3 and 100%, respectively. Based on these results, a sequential two-step procedure for recovering all valuable products (Mn, Zn and graphite) with high efficiency from a Mn rich residue is proposed.

Original languageEnglish
Pages (from-to)148-155
Number of pages8
JournalMinerals Engineering
Publication statusPublished - Jan 2019
Externally publishedYes


  • Circular economy
  • Manganese
  • Microwave
  • Oxidative precipitation
  • Recycling
  • Reductive leaching
  • Solvent extraction
  • Ultrasound
  • Zinc


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