Mild Extraction of Ammonium Metavanadate From Alumina Solid Waste and Its Electrochemical Calcium Storage Application

The alumina industry generates a large amount of sodium oxalate solid waste every year, posing a serious environmental risk. However, this waste also contains abundant vanadium resources. Vanadium, as a rare metal, has important applications in various fields. In this case, we develop a mild vanadium extraction method from the waste to prepare ammonium metavanadate (NH 4 VO 3 ) and explore its application potential in electrochemical calcium storage. Evaluated by green chemistry principles, this waste‐to‐resource route circumvents the harsh conditions typical of conventional extraction, offering a notably milder pathway with competitive atom economy and a significant reduction in secondary waste generation, showcasing notable advantages in process efficiency and waste minimization over conventional high‐intensity extraction methods. The achieved NH 4 VO 3 material featured a characteristic block‐like morphology and delivered good electrochemical calcium storage capability. The capacity retained 38.6 mAh·g −1 after 5000 cycles at 2 A·g −1 . This work not only exemplifies the upcycling of industrial solid waste into a high‐value energy storage material but also presents a quantifiably green and efficient strategy for sustainable battery material production.