Recovery of spent VOSO 4 using an organic ligand for vanadium redox flow battery applications.

To recover the spent vanadium compound, Rhodamine-B-based Schiff's base ligand (L ₁ ) was synthesized via ultrasonication process and was evaluated with vanadyl sulfate (VOSO ₄ ), which has shown considerable selectivity towards V(IV). The change of the solution color from colorless to pink is attributed to L ₁ after the reaction with vanadium ion owing to the successful formation of the vanadium complex and the opening of the spirolactam ring in the L ₁ structure. In FT-IR spectra, the vanadyl peaks are co-existed with the L ₁ structure, which confirmed the complex formation of the L ₁ with vanadium. Similarly, the binding energy of V(IV) was identified at 516.2 eV for V2p _3/2 in XPS spectra. The new strategy for VOSO ₄ recovery was established through solvent extraction and acid leaching. After recovery process, the absence of vanadium peak in the XPS confirmed the complete removal of V(IV) from the complex. The recovered VOSO ₄ solution used as an electrolyte in vanadium redox flow battery (VRFB) systems, where the unit cell performance is comparable with the conventional electrolyte solution. The advantage of study is reuse of VOSO ₄ as a resource for energy storage applications.
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