The content, chemical state and accumulation of vanadium in a drill core of Alum shale from Kinnekulle

Abstract: Exploitation of alum shale is a controversial subject in Sweden due to the history of pollution of the environment and groundwater, from past mining industries. The extraction of vanadium from alum shale is no different. Nevertheless the metal is a valuable resource used in tools, building, industries and aerospace materials. A look to the future reveals that vanadium may play a role in renewable energy. Vanadium redox flow batteries can store large amount of energy utilizing the many oxidation state of vanadium. This could solve the problem of energy storage many sources of renewable energy faces. This project is devoted to give a better understanding of how vanadium is bound and accumulated in the Cambrian Alum Shale Formation of southern Sweden, with the hope that this knowledge can help find an environmental friendly process to extract vanadium from alum shale in the future. In this project a drill core penetrating the Alum Shale Formation at Kinnekulle, has been analyzed with x-ray fluorescence spectroscopy, x-ray powder diffraction, x-ray photoelectron spectroscopy, IR-spectroscopy and a total organic carbon analysis. The aim is to identify the chemical state and evaluate possible correlations between vanadium, trace elements, organic carbon and minerals. The drill core was found to be enriched in several trace elements, such as vanadium, barium, molybdenum, uranium, lead, copper and nickel, compared to Clarke values of black shale. Illite, the suspected main carrier of vanadium, had a very low signal in the x-ray powder diffraction and organic matter is proposed as a major carrier of vanadium. The level of anoxia in the waters at the time of sedimentation showed a rise in dissolved oxygen at 1,02 m, which could be the cause of the lower amount of vanadium in the top-most section of the drill core.