Process for separating and recovering metals

摘要

A process for treating spent catalyst containing heavy metals, e.g., Group VIB metals and Group VIII metals is provided. In one embodiment after deoiling, the spent catalyst is treated with an ammonia leach solution under conditions sufficient to dissolve the group VIB metal and the Group VIII metal into the leaching solution, forming a leach slurry. After solid-liquid separation to recover a leach solution, chemical precipitation and solids repulping is carried out to obtain an effluent stream containing ammonium sulfate (Amsul), ammonium sulfamate, Group VB, Group VIB and Group VIII metals. Following sulfidation, the Group VIII metal is fully removed and Group VB and Group VI metals are partially removed from the Amsul stream. In the additional steps of oxydrolysis and iron precipitation, an effective amount of ferric ion at a pre-select pH is added to form insoluble complexes with the Group VB and Group VIB metals, which upon liquid-solid separation produces an effluent ammonium sulfate stream containing less than 10 ppm each of the Group VB and Group VIB metals.

主权项

1. A method for recovering metals from a spent catalyst, the method comprising:
leaching a Group VIB metal, a Group VIII metal, and a Group VB metal, from the spent catalyst with an ammonia containing leach solution at a temperature and a pressure sufficient to form a pressure leach slurry; separating and removing a solid residue from the pressure leach slurry to form a pressure leach solution comprising a Group VIB soluble metal complex and a Group VIII soluble metal complex; treating the pressure leach solution by chemical precipitation to precipitate at least a portion of the Group VIB metal and at least a portion of the Group VIII metal as precipitated metal complexes; recovering the precipitated metal complexes by at least a separation means selected from settling, filtration, decantation, centrifugation and combinations thereof, forming a first effluent stream containing less than 600 ppm of the Group VIB metal and less than 400 ppm of the group VIII metal and a solid residue containing at least 97% of incoming VIB metal and over 80% of incoming Group VIII metal; sulfiding the first effluent stream with a sulfiding agent to form a sulfided slurry comprising a Group VB metal sulfide and/or oxide, a Group VIB metal sulfide and a Group VIII metal sulfide; separating and removing the Group VB metal sulfide and/or oxide, the Group VIB metal sulfide and the Group VIII metal sulfide from the sulfided slurry, forming a second effluent stream comprising a Group VB and a Group VIB soluble metal compound; contacting the second effluent stream with an effective amount of ferric ion at a pre-selected pH for the ferric ion to form a complex with the Group VB and Group VIB metal; performing a liquid-solid separation to remove the Group VB and Group VIB metal complex as solids, forming a third effluent containing less than 5 ppm of the Group VB metal and less than 5 ppm of the Group VIB metal.