Recovery of Vanadium and Nickel from Industrial Wastes.

Extraction of Vanadium and Nickel from waste material was investigated using alkaline and acidic leaching systems. Spent catalyst coming from manufacture of sulfuric acid (3.5% V and 0.63% Ni) and boiler ash (25% V and 13% Ni) can be used as a secondary source of metals. Statistical design of experiments and analysis of variance (ANOVA) were performed in order to determine the main effects and interactions of the investigated factors, which were temperature of roasting and leaching; concentration of the leaching reagent (H2SO4/NaOH); pulp concentration and process time. ANOVA shows that roasting step is the main factor with positive effect on the recovery of metals, whereas pulp concentration shows a negative effect probable due to the inefficient mixing.