Selective leaching trace elements from bauxite residue (Red mud) without and with adding solid NH4Cl using microwave heating

Jin Seok Kim, Nag Choul Choi, Ho Young Jo

Research output: Contribution to journalArticlepeer-review

Abstract

Bauxite residue (red mud), which is an industrial byproduct, contains valuable trace elements. Solid NH4Cl was used as a chlorinating agent during the microwave heating of red mud to convert trace elements into soluble metal chloride. Red mud was heated using microwave ovens under various conditions (i.e., with the addition of solid NH4Cl and with a range of microwave output powers and microwave heating times). Leaching tests were then conducted using deionized (DI) water on the microwave-heated red mud to leach trace elements from red mud. V, Cr, and As were selectively leached from the microwave heated red mud slurry (30% water content), whereas Mn, Cu, Co, Ni, Zn, and Pb were selectively leached from the microwave-heated red mud with the addition of solid NH4Cl. The oxides of V, Cr, and As in red mud could be transformed into metal chlorides by chlorination, which are insoluble in water, or could be easily volatilized when red mud was microwave-heated in the presence of solid NH4Cl. On the other hand, the oxides of Mn, Cu, Co, Zn, Ni, and Pb in red mud could be heated rapidly by microwave irradiating, resulting in metal chlorides in the presence of solid NH4Cl. Those metal chlorides are relatively soluble in water, leading to higher leaching efficiency for microwave-heated red mud with the addition of solid NH4Cl. Experimental results suggest that trace elements from red mud can be selectively leached by microwave heating of red mud without or with the addition of solid NH4Cl.

Original languageEnglish
Article number1281
JournalMetals
Volume11
Issue number8
DOIs
Publication statusPublished - 2021 Aug

Bibliographical note

Funding Information:
Funding: This research was supported by the Korea Environmental Industry & Technology Institute (KEITI) through the Advanced Technology Program for Environmental Industry, funded by the Korea Ministry of Environment (MOE) (2017000140010) and was partially supported by Korea Environment Industry & Technology Institute (KEITI) through Subsurface Environment Management (SEM) Project, funded by Korea Ministry of Environment (MOE) (2018002440002).

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Keywords

  • Ammonium chloride
  • Leaching
  • Microwave heating
  • Red mud
  • Trace elements

ASJC Scopus subject areas

  • General Materials Science
  • Metals and Alloys

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