Recovery of Valuable Metals from Spent Al2O3-Based Catalysts by Sodium Carbonate Roasting and Water Leaching

This paper reports a comprehensive recovery of valuable metals from spent Al2O3-based catalysts using sodium carbonate roasting and water leaching. In all experimental parameters, roasting is one of the most critical influences on the leaching effect. During the roasting of sodium carbonate, insoluble NiAl2O4 and α-Al2O3 are converted to soluble NaAlO2, which can be leached by water. Then, Al, Ni, and V were recovered by leaching solution and residue, respectively. The experimental results showed that Al and V leaching rates were 99.64% and 99.24%, respectively, under the optimal leaching conditions. Moreover, the simple metal composition in the leachate and residue is more favorable for metal recovery than the direct recovery of Al and Ni from the spent Al2O3-based catalyst. Adding Ba(OH)2, which is stoichiometric with V, to the leachate allows the recovery of V first. Subsequently, Al(OH)3 precipitation was obtained by adding the appropriate amount of hydrochloric acid dropwise, and γ-Al2O3 was obtained by calcination. The residue was acid-leached using sulfuric acid again, and after the reaction, Ni(OH)2 was recovered by adding excess NaOH. Ni(OH)2 was heated to a certain temperature to obtain NiO. The recoveries of Al and Ni were 98.68% and 96.31%, respectively, during the whole experiment.