Clean and cost-efficient preparation of vanadium electrolyte from the vanadium-rich solution of black shale by solvent extraction

This study proposes a clean and cost-efficient preparation process for vanadium electrolytes from the vanadium -rich solution of black shale. The introduction of saponified D2EHPA promoted vanadium recovery and further separation of impurities from vanadium-rich solutions. The preparation of a high-purity vanadium electrolyte was achieved by a four-stage countercurrent extraction at an initial pH as low as 1.0, 8 min, D2EHPA concen-tration of 30%, saponification degree of 60%, and phase ratio of 1:1, as well as a three-stage countercurrent stripping with 4 mol L-1 H2SO4 at phase ratio (O/A) of 6:1, 30 min. The developed electrolyte showed qualified electrochemical and charge-discharge performance, with coulombic efficiency, voltage efficiency, and energy efficiency reaching 91.07%, 93.44%, and 85.10%, respectively. This method saves 30.28% in preparation costs over the traditional method and produces no ammonia, nitrogen, or harmful gases. The technology is techno-logically advanced, economically sensible, and ecologically friendly, and is expected to be applied to large-scale production and promote the development of VRFB and new energy.