Ionic Liquids as Extraction Media in a Two-Step Eco-Friendly Process for Selective Tantalum Recovery

Abstract

The unique properties of tantalum (Ta) have resulted in its important usage to supply the capacitors and semiconductor production for electronics devices. Technological needs make Ta economically and strategically important to industrialized countries. Among different possibilities, the recovery of Ta from industrial waste and end-of-life products represents an economically attractive and viable approach, which aims at decreasing the environmental footprint in general. Currently, there is a lack of an efficient Ta recycling strategy from e-waste. In the present work we studied the possibility to use pure ionic liquids such as N-butyl-N-ethylpiperidinium bis(trifluoromethylsulfonyl)imide (EBPiP-NTf2), N-octyl-N-ethyl-piperidinium bis(trifluoromethylsulfonyl)imide (EOPiP-NTf2) as extracting media. Ionic liquids were used as alternative solvents that will have limited impact on health and environment compared to traditional organic solvents. We propose an eco-friendly process for the extraction and stripping of tantalum from sulfuric acidic medium that may come from of the dissolution of bottom ash and by-products of industrial activities, as well as from secondary sources such as waste electrical and electronic equipment (WEEE). The extractability of ILs for Ta was demonstrated, and under the experimental conditions, the more promising properties have been highlighted for EOPiP-NTf2. Back extraction of Ta from the loaded ionic liquid phase was also examined and showed that quantitative recovery of metal was possible using water, allowing thus to recover the ionic liquid and the Ta. Considering the efficiency as well as greener aspects of the process, due to the use of ionic liquids which loss is highly limited in aqueous phase, a more "sustainable process" is proposed in comparison to organic solvents and previous ionic liquid based extraction system useful for the selective recovery of tantalum.

Recent Studies on Ionic Liquids in Metal Recovery from E-Waste and Secondary Sources by Liquid-Liquid Extraction and Electrodeposition: a Review

“…Using IL as a viscosity-reducing agent may have a positive (Devi and Sukla 2019) or negative (Łukomska et al 2020a, b) effect on extraction. As another important challenge in the use of ILs, the ability to recover and reuse them in the extraction process is very important (Li et al 2019;Micheau et al 2020). Decreasing the number of metal recovery steps also saves time and cost of these processes, which can create a high potential for use in industry (Micheau et al 2020).…”

“…As another important challenge in the use of ILs, the ability to recover and reuse them in the extraction process is very important (Li et al 2019;Micheau et al 2020). Decreasing the number of metal recovery steps also saves time and cost of these processes, which can create a high potential for use in industry (Micheau et al 2020). ILs are also used in the leaching process; the advantages of which are selective leaching, short leaching time (Orefice et al 2020), and preventing the release of highly toxic metals into the environment (In e-waste metal leaching, which may lead to human health harms by releasing highly toxic metals, using solutions to prevent this from happening is a very important challenge.)…”

“…Therefore, it has been observed that, when ILs are used as extractants, diluents are also used along with ILs to solve the problem of high viscosity (Dhiman and Gupta 2020). Sometimes ILs with low viscosity are used to solve the problem of high viscosity and sometimes a mixture of two ILs can be used to reduce the viscosity, but their mixture may not show a synergistic effect and have a negative effect on the extraction efficiency (Łukomska et al 2020a, b;Micheau et al 2020;Vereycken et al 2020).…”

Insight into the Liquid–Liquid Extraction System AuCl4−/HCl/A327H+Cl− Ionic Liquid/Toluene

“…Due to these properties, these liquids are considered to be green solvents. Ionic liquids are used in several Processes 2021, 9, 608 2 of 13 fields, e.g., biochemistry [24], electrochemistry [25], pharmaceutics [26,27], and analytical chemistry [28], and in the recovery of metals, with recent applications discussed in the literature including base metals [29][30][31], rare earths [32][33][34], indium [35,36], gold [37,38], and others [39,40].…”

Insight the Liquid-Liquid Extraction System AuCl4-/HCl/A327H+Cl- Ionic Liquid/Toluene

“…Ionic liquids had been amply used, in the recovery of metals, being some recent applications given in the literature, i.e. base metals [15][16][17], rare earths [18][19][20], indium [21,22], gold [23,24] and others [25,26].…”