Recovery of vanadium and nickel from boiler-ash by sulphuric acid leaching

Increasing environmental concerns and the new obligations regarding the disposal of hazardous residues is forcing companies to take new precautions for their own hazardous wastes. Recycling of some industrial waste containing base metals (such as V, Ni, Co and Zn) may be an economical opportunity in the exploitation of these wastes. In the present work a preliminary study to recover V and Ni from industrial waste is reported: boiler ashes and spent catalysts were considered in this study to develop a hydrometallurgical operation in which sulphuric acid leaching is the main step of the overall process. Fractional and full-factorial experiments were carried out to study the effect of the roasting process, sulphuric acid concentration, leaching temperature, pulp concentration and the presence of H2O2 on the leaching treatment. The experimental results indicated the influence of the above mentioned factors on the V and Ni extraction yield and shown a preliminary technical feasibility of the process