Metal Reclamation from Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 271

Figure 11.3: Effect of alamine 304 concentration on Mo extraction (pH 1.5, 25 C) [From
ref. 619 . Reprinted with permission].
corresponding sulfates, was 2.1:1. Preoxidation of spent catalyst influenced the leaching
efficiency. A higher efficiency was achieved when preoxidation was carefully controlled to
avoid sintering of metals. Otherwise, diffusion and/or reaction of metals with the support
during preoxidation affected subsequent leaching. After leaching, the residual solid was
filtered off and filtrate used for metal separation using combination of solvent extraction,
selective precipitation, and ion exchange column. Figure 11.3 [619] shows the effect of
concentration of extracting agent, such as alamine 304 in kerosene on the extraction of Mo.
Besides alamine 304 concentration, pH of the solution had a pronounced effect on leaching.
As it is shown in Fig. 11.4 [619] , the best extraction efficiency was attained when pH of 2 was
approached. The raffinate was used for recovery of the Co and/or Ni. This was achieved by
adding 0.3mol/L solution of (NH 4 ) 2 C 2 O 4 until the solution became colorless. Solid oxalates
of Co or Ni were filtered off and washed with 0.1mol/L (NH 4 ) 2 C 2 O 4 and dried.
Figure 11.4: Effect of pH on Mo extraction with 5 vol.% alamine 304 at 25 C [From ref. 619 .
Reprinted with permission].