Cyclic Imide Dioximes as Practical Extractants of Vanadium from Complex Mixtures

Abstract

This thesis focuses on the development of an acid-stable chelating agent for the facile and selective extraction of pentavalent vanadium ions, V(V), from mixed metal solutions. Two cyclic imide dioxime-based ligands, phthalimidedioxime (H2CIDII) and naphthalimidedioxime (H2CIDIII), were initially evaluated for stability, scalability, and coordination to V(V). Interestingly, H2CIDIII exhibited strong coordination with V(V) and was further investigated for V(V) extraction. The six-chapter thesis discusses the essential factors for transitioning material and technology from laboratory scale to practical application. Chapter One reviews conventional V(V) extraction technologies, emphasizing the environmental impacts and limitations of current and emerging methods. The chapter introduces cyclic imide dioximes and oil sands tailings as potential materials and source for V(V) extraction. Chapter Two delves into H2CIDIII's development, evaluating scalability, stability, and toxicity using advanced spectroscopic techniques and toxicity assays. Chapter Three highlights H2CIDIII's effectiveness in V(V) recovery, achieving complete complexation in 45 minutes and instant precipitation through pH adjustment. With an extraction capacity of 205.4 mg/g, H2CIDIII ranks among the top 2% in effectiveness. Selective precipitation of the V(V)-CIDIII complexes was achieved in acidic conditions and attributed to the formation of unique and acid stable vanadium complexes. H2CIDIII was easily regenerated for multiple extraction cycles, and the extraction process was optimized and tested with simulated and real oil sands tailings. Chapter Four explores the extraction mechanism through X-ray diffraction, NMR, FTIR, and DFT calculations, revealing the pivotal roles of the negative charge and acid resistance of V(V)-CIDIII complexes in the separation and recovery of V(V). The formation of a non-oxido vanadium complex illustrates the strong interaction between V(V) and H2CIDIII, explaining its high affinity during the extraction process. Chapter Five investigates the binding constants and coordination modes of the ligands and metal ions, further highlighting H2CIDIII's higher affinity for V(V). The final chapter explores potential applications of recovered V(V) and its complexes in redox batteries and epoxidation reactions. A provisional patent has been filed, and a manuscript is undergoing final revisions for publication in Nature Communications, underscoring the project's potential impact.