Effect of pre-concentration on membrane solvent extraction process for the recovery of rare earth elements from dilute acidic leachate

Yüksekdağ A., Köse Mutlu B., Wiesner M. R., Koyuncu İ.

PROCESS SAFETY AND ENVIRONMENTAL PROTECTION, vol.161, pp.210-220, 2022 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 161
  • Publication Date: 2022
  • Doi Number: 10.1016/j.psep.2022.03.035
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Aqualine, Aquatic Science & Fisheries Abstracts (ASFA), Biotechnology Research Abstracts, CAB Abstracts, Chemical Abstracts Core, Communication Abstracts, Environment Index, Greenfile, INSPEC, Metadex, Pollution Abstracts, Veterinary Science Database, Civil Engineering Abstracts
  • Page Numbers: pp.210-220
  • Keywords: Mixed e-waste, Rare earth elements, Nanofiltration, Supported liquid membrane, Separation, IONIC LIQUIDS, STRATEGIES, REAGENTS
  • Istanbul Technical University Affiliated: Yes


Pre-concentration and separation processes of Rare Earth Elements (REEs) were investigated in terms of several factors. Nitric acid leachate of e-waste was first pre-treated by increasing pH and filtering through microfiltration. For pre-concentration, pre-treated leachate was concentrated by nanofiltration. While a 70% permeate recovery ratio was kept constant, the rare earth elements concentrations were triplicated under optimum conditions. A flat sheet supported liquid membrane process with a polyvinylidene fluoride (PVDF) support membrane was successfully used to extract REEs from the pre-treated leachate. Of the two extractants evaluated, bis-2-ethylhexyl phosphoric acid (D2EHPA) displayed a higher REE separation efficiency than did di-2,4,4,-trimethylpentyl phosphinic acid (Cyanex 272). However, Cyanex 272 separated Sc more selectively. For direct membrane solvent extraction (MSX) and MSX with pre-concentration, pretreatment pH and D2EHPA concentrations were optimized at values of 1.5% and 15%, respectively. When comparing the results of MSX for direct and pre-concentrated configurations, it was seen that REEs and HREEs recoveries were increased 10% and 30% in MSX with pre-concentration at the end of single-stage MSX. Pre-concentration not only increased the MSX process efficiency but also enabled acid recovery from nanofiltration permeate. A more environmentally friendly and economical process scheme was proposed, including acid recovery from both NF filtrate and post-MSX leaching residue by two different membrane distillation configurations.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.