Please cite this article as: J. Almeida, R. Craveiro, P. Faria, et al., Electrodialytic removal of tungsten and arsenic from secondary mine resources -Deep eutectic solvents enhancement, Science of the Total Environment (2018), https://doi..pt (A. B. Ribeiro) HIGHLIGHTS Proof of concept in coupling DES + ED for As and W removal from mining residues Best As and W extraction achieved with ChCl:MA (1:2) and ChCl:OA (1:1) DES and electrical current use improved extraction for As (22 %) and W (11 %) From total As and W extracted, electromigration achieved 82 % for As and 77 % for W Journal Pre-proof J o u r n a l P r e -p r o o f 2 ABSTRACTTungsten is a critical raw material for European and U.S. economies. Tungsten mine residues, usually considered an environmental burden due to e.g. arsenic content, are also secondary tungsten resources. The electrodialytic (ED) process and deep eutectic solvents (DES) have been successfully and independently applied for the extraction of metals from different complex environmental matrices. In this study a proof of concept demonstrates that coupling DES in a two-compartment ED set-up enhances the removal and separation of arsenic and tungsten from Panasqueira mine secondary resources. Choline chloride with malonic acid (1:2), and choline chloride with oxalic acid (1:1) were the DES that in batch extracted the average maximum contents of arsenic (16 %) and tungsten (9 %) from the residues. However, when ED was operated at a current intensity of 100 mA for 4 days, the extraction yields increased 22 % for arsenic and 11 % for tungsten, comparing to the tests with no current.From the total arsenic and tungsten extracted, 82 % and 77 % respectively were successfully removed from the matrix compartment, as they electromigrated to the anolyte compartment, from where these elements can be further separated. This achievement potentiates circular economy, as the final treated residue could be incorporated in construction materials production, mitigating current environmental problems in both mining and construction sectors.
KeywordsCritical raw material, harmful compound, secondary resource, electro-based technology, choline chloride/malonic acid, choline chloride/oxalic acid Abbreviations Journal Pre-proof J o u r n a l P r e -p r o o f 3 "W" -Tungsten; "As" -Arsenic; "ED" -Electrodialytic; "DES" -Deep Eutectic Solvents; "ChCl:OA" -Choline Chloride/ Oxalic Acid; "ChCl:MA" -Choline Chloride/ Malonic Acid; "ChCl:LA" -Choline Chloride/ Latic Acid; "PA:U" -Propionic Acid/ Urea the individuals exposed (Coelho et al., 2014).The electrodialytic (ED) process is a treatment technology, that has been studied over the last three decades, to remove heavy metals from several environmental matrices: (1) soil (Ribeiro Journal Pre-proof W that electromigrated into the anode compartment (anolyte) were determined according to Eq. 3 (in section 2.3.3) and presented in Table 6. The high migration percentages were obtained with ChCl:MA at 100 mA for As (82.3 ± 1.3 %) and 50 mA for W (76.5 ± 8.6 %).This ...