New challenges and applications of supported liquid membrane systems based on facilitated transport in liquid phase separations of metallic species

The linear economic model based on “take-make-dispose” has become unsustainable, revealing the necessity of shifting towards a circular economy approach, in which secondary raw materials play a key role in closing material cycles. In this context, industrial effluents with metallic content, are considered a potential secondary source for these elements, the lack of the availability of the appropriate technology being the main barrier when implementing circular economy principles at industrial scale. In this regard, supported liquid membrane systems based on facilitated transport may be decisive. Thus, the objective of this research paper is to show the potential of facilitated transport systems to foster the transition to a more sustainable management of industrial metallic effluents. To accomplish that, three different applications of supported liquid membrane systems in acidic industrial effluents will be presented: a) Zn/Fe separation, b) Ni/Cd separations and c) Removal of hexavalent Cr. Additionally, the recovery and separation of two different critical raw materials, i.e. Li and rare earth elements will be discussed. Although facilitated transport systems have been successfully applied to both, Zn/Fe and Ni/Cd separation, as well as to hexavalent Cr removal, further work should be done for the successful recovery and separation of Li and rare earths with supported liquid membrane systems, especially in terms of selectivity improvement and validation with real industrial effluents.