Recovery and Separation of Vanadium, Nickel, and Molybdenum from the Industrial Waste of a Petroleum Refinery by a Complexation Method

Based on the characteristics of complexation reactions, a novel method for the recovery and separation of vanadium (V), molybdenum (Mo), and nickel (Ni) is proposed. This approach mainly utilizes oxalic acid and hexamethylenetetramine (HMT) as complexing agents to recover and separate V, Mo, and Ni from the roasting slag of the byproduct carbon black from petroleum refineries, which includes the above elements plus iron and calcium. According to the differences in the solubilities of the metallic oxalic acid complexes, V and Mo were selectively leached with efficiencies of 95.49% and 97.74%, respectively, while Ni, iron, and calcium remained in the residue. After decomplexing the V and Mo complexes in the leachate by adding sulfuric acid, the oxalic acid was recycled. Then, the solution containing V and Mo was treated with HMT, and 93.19% of the Mo was complexed and precipitated. Finally, the precipitated Mo complex was dissociated by the addition of calcium oxide to separate and recover Mo and HMT with a Mo recovery efficiency of 95.72%, and HMT was regenerated and used in the following cycles. As a result, the method proposed in this study is an efficient and sustainable way to recover and separate V, Mo, and Ni from the industrial waste of petroleum refineries.