A method is disclosed for separating and recovering base metals from a used hydroprocessing catalyst originating from Group VIB and Group VIII metals and containing at least a Group VB
metal. In one embodiment, the method comprises the steps of: contacting the used catalyst with an
ammonia leaching solution under conditions sufficient to dissolve the group VIB
metal and the Group VIII
metal into the leaching solution; forming a leached
slurry containing at least a group VIB metal complex and at least a group VIII metal complex,
ammonium sulfate and a
solid residue containing at least a Group VB metal complex and
coke; separating and removing from the leached
slurry the
solid residue and
coke; precipitating from the remaining solution at least a portion of the Group VIB metal complex and at least a portion of the Group VIII metal complex by controlling the pH to form a liquid material substantially free of Group VB, Group VIB and Group VIII metals and another
solid material comprising substantially Group VIB and Group VIII metal complexes. Said
solid material is further processed by
dissolution, means of separation, further means of
precipitation and oxidative
dissolution to produce, separately, a Group VIB metal product solution, a Group VIII metal product solution and a purified
ammonium sulfate product solution.