Green technology actively seeks new solvents to replace common organic solvents that present inherent toxicity and have high volatility, leading to evaporation of volatile organic compounds to the atmosphere. Over the past two decades, ionic liquids (ILs) have gained enormous attention from the scientific community, and the number of reported articles in the literature has grown exponentially. Nevertheless, IL "greenness" is often challenged, mainly due to their poor biodegradability, biocompatibility, and sustainability. An alternative to ILs are deep eutectic solvents (DES). Deep eutectic solvents are defined as a mixture of two or more components, which may be solid or liquid and that at a particular composition present a high melting point depression becoming liquids at room temperature. When the compounds that constitute the DES are primary metabolites, namely, aminoacids, organic acids, sugars, or choline derivatives, the DES are so called natural deep eutectic solvents (NADES). NADES fully represent green chemistry principles. Can natural deep eutectic solvents be foreseen as the next generation solvents and can a similar path to ionic liquids be outlined? The current state of the art concerning the advances made on these solvents in the past few years is reviewed in this paper, which is more than an overview on the different applications for which they have been suggested, particularly, biocatalysis, electrochemistry, and extraction of new data. Citotoxicity of different NADES was evaluated and compared to conventional imidazolium-based ionic liquids, and hints at the extraction of phenolic compounds from green coffee beans and on the foaming effect of NADES are revealed. Future perspectives on the major directions toward which the research on NADES is envisaged are here discussed, and these comprised undoubtedly a wide range of chemically related subjects.

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Deep eutectic solvents (DES) can be formed by bioactive compounds or pharmaceutical ingredients. A therapeutic DES (THEDES) based on ibuprofen, a non-steroidal anti-inflammatory drug (NSAID), and menthol was synthesized and its thermal behavior was analyzed by differential scanning calorimetry (DSC). A controlled drug delivery system was developed by impregnating a starch:poly-ϵ-caprolactone polymeric blend (SPCL 30:70) with the menthol:ibuprofen THEDES in different ratios (10 and 20 wt%), after supercritical fluid sintering at 20 MPa and 50 °C. The morphological characterization of SPCL matrices impregnated with THEDES was performed by scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). Drug release studies were carried out in a phosphate buffered saline. The results obtained provide important clues for the development of carriers for the sustainable delivery of bioactive compounds.

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Recent findings have reported the reason why some living beings are able to withstand the huge thermal amplitudes between winter and summer in their natural habitats. They are able to produce metabolites decreasing deeply the crystallization temperature of water, avoiding cell disrupture due to the presence of ice crystals and overcoming osmotic effects. In vitro, the possibility to cool living cells and tissues to cryogenic temperatures in the absence of ice can be achieved through a vitrification process. Vitrification has been suggested as an alternative approach to cryopreservation and could hereafter follow an interesting biomimetic perspective. The metabolites produced by these animals are mostly sugars, organic acids, choline derivatives, or urea. When combined at a particular composition, these compounds form a new liquid phase which has been defined as Natural Deep Eutectic Solvents (NADES). In this review, we relate the findings of different areas of knowledge from evolutive biology, cryobiology, and thermodynamics and give a perspective to the potential of NADES in the development of new cryoprotective agents.

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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 ...