Synthesis and characterization of fibrous nickel hydroxide obtained from spent nickel catalyst

The recovery of nickel from spent nickel catalyst for the preparation of nickel hydroxide was studied. Nickel was extracted from the spent catalyst by acid leaching with 1 mol/L sulfuric acid at 90 °C. Purified nickel solution was used in the preparation of nickel hydroxide. Three different methods, namely urea hydrolysis, conventional, and hydrothermal methods, of precipitation using NaOH were employed to get various nickel hydroxides samples named as Ni(OH)2-U, Ni(OH)2-C, and Ni(OH)2-H, respectively. Hydrothermal treatment induced better crystallinity in the Ni(OH)2 compared with conventional method. Both Ni(OH)2-C and Ni(OH)2-H samples have mixed phases of β-Ni(OH)2 and α*-Ni(OH)2·0.75H2O phases, whereas Ni(OH)2-U has only α*-Ni(OH)2·0.75H2O. TEM image of Ni(OH)2-U sample shows rod-like Ni(OH)2 structures. Among all, Ni(OH)2-U shows the best electrochemical activity.