Sustainable recovery of nickel, molybdenum, and vanadium from spent hydroprocessing catalysts by an integrated selective route

Abstract

Abstract: In this work, nickel, molybdenum, and vanadium were selectively extracted from the spent hydroprocessing catalysts (Ni–Mo–V/Al2O3) by using an integrated ammoniacal leaching and selective separation process. After roasted at 400 °C, molybdenum and nickel were selectively extracted by ammoniacal liquors at pH 9 in the first step and the leaching efficiency of nickel and molybdenum was 88.74% and 97.92%, respectively. In the second leaching step, vanadium was selectively extracted from the residues by ammoniacal liquors containing 6% (v/v) H2O2 at pH 12 and the leaching efficiency of vanadium was above 97.13%. The selective separation of nickel in the leachate was achieved at pH of 6.86 by solvent extraction with 2 mol/L neo-decanoic acid (Versatic10) in sulfonated kerosene, where the extraction efficiency was about 96% and the complete stripping of Ni was achieved with 3 mol/L NaOH to directly obtain Ni(OH)2 precipitates. The molybdenum in extraction raffinate can be recovered by barium molybdate precipitate method. The vanadium-bearing leachate was further treated to obtain ammonium metavanadate precursor by adding HNO3 to adjust the solution pH to 7.5–9 and then flower-like V2O5 was obtained after calcination at 500 °C. Based on the above highly-selective treatment process, nickel, molybdenum, and vanadium in the spent hydroprocessing catalysts were recovered as the corresponding metal compounds, respectively.