Influence of iron on the extraction of vanadium from oil ashes

The disposal of large amounts of ashes derived from the combustion of oil in power stations poses serious environmental problems. However, the relatively high content of useful metals in the ashes provides an incentive to develop processes for their recovery. The influence of iron on the alkali extraction of vanadium has been investigated by following, using Mössbauer spectroscopy, the physico-chemical changes in iron samples originating from power plants located in Sicily. The extraction yield is influenced by factors such as the dimensions and morphology of the particles and the occlusion of vanadium in alkali-resistant particles (both related to firing conditions), together with the presence of vanadium in the tetravalent state. Formation of iron vanadates as a limiting factor of vanadium solubility under alkaline leaching is not supported by experimental evidence.