Process intensification of metal solvent extraction studies using a miniaturized solvent extraction plant

Abstract

This study examines the potential of a miniaturized solvent extraction plant (MSXP) to improve the efficiency and reproducibility of laboratory and pilot-scale metallurgical studies that typically require extended testing periods. The MSXP has been designed to replace conventional solvent extraction (SX) apparatus and aims to reduce start-up time, time to reach equilibrium, and overall test time. Two copper solvent extraction (Cu-SX) research campaigns were conducted to test the functionality, ease of operation, modularity, and reproducibility of the MSXP. The first campaign quantified the extraction efficiency and net copper transfer, while the second campaign operated the MSXP in a semicontinuous countercurrent flow configuration with three extraction and two stripping stages. The main variables studied in the first campaign are the number of stages (1-3), volumetric flow rates (O/A, 1-3), and organic phase residence time in the micro-contactor (0.7-2.4 min). The results demonstrate that the MSXP can work with very low stage efficiencies (48%), while achieving high copper recoveries (> 90%). At the stripping circuit level, we show that the MSXP can operate at superior stage efficiencies (> 100%), with low copper recoveries (30%–55%). The reproducibility evaluation also demonstrates high statistical confidence (< 6% CV) in the obtained process values. The MSXP offers great flexibility in net copper transfer and can be used to benchmark and emulate a wide range of Cu-SX systems. Experimental Cu-SX campaigns can be run in about 60 min while investing roughly US$1.4/h on reagents, which is significantly lower compared to typical campaigns that can last from days to weeks to reach reliable research outcomes and require about US$62/h for reagents. The potential of MSXP extends to more elaborate solvent extraction systems, specifically those designed to purify energy-critical elements like lithium, nickel, cobalt, or rare-earth elements. This study demonstrates the promise of process intensification approaches for improving the efficiency of laboratory and pilot-scale SX studies, which can help in reducing time, reagents, and energy consumption while improving the reproducibility of results.