On-line quantification of solid-phase metal extraction efficiencies using instrumented millifluidics platform

A semi-automated and fully integrated millifluidic platform has been developed for rapid development and study of Solid-phase extraction (SPE) processes. In this instrumented setup, the fluid coming out of the extraction mini-column is analysed directly using on-line X-ray fluorescence, enabling a real-time, fast and accurate measurement of the elemental concentrations within the flowing liquid. This platform aims at enhancing and facilitating the development of SPEs whose numerous experimental parameters make it time consuming to optimize and upscale. Hence, this approach solves the labour intensity issue and is as accurate as off-line Inductively Coupled Plasma, for instance. This is exemplified with a system, typical of the electronic wastes recycling industry, comprising of a mixture of Rare-Earth Elements (REEs) and Iron, whose separation is investigated as a function of various experimental parameters. It enabled us to study the performance of the newly released METALICAPT® commercial materials and to determine an optimized path towards the almost total separation of Iron from the initial mixture. Overall, the original SPE process reported herein demonstrates the platform's reliability, performance and range of applicability. National Environmental Agency (NEA) National Research Foundation (NRF) Submitted/Accepted version FO, SC and J.C.G. acknowledge financial support from SCARCE project, which is supported by the National Research Foundation, Singapore, and National Environment Agency, Singapore under its Closing the Waste Loop Funding Initiative (Award No. USS-IF-2018-4). J.C.G. acknowledges funding for the platform from the European Research Council under the European Union’s 7th Framework Program (FP/2007-2013)/ERC Grant Agreement N◦ [320915] “REE-CYCLE”: Rare Earth Element reCYCling with Low harmful Emissions. BK ac- knowledges financial support from the European Research Council under the European Union’s 7th Framework Program (FP/2007-2013)/ ERC Proof of Concept Grant Agreement N◦ [768722] “SYNEXTRACT”: All Aqueous, continuous, Solid-Liquid SYNergistic EXTRACTion of rare earth elements. FO thanks CEA’s program “Mat ́eriaux et Proc ́ed ́es” for a PhD grant support (project MICROPRO).