Environmental Engineering Reference
In-Depth Information
Figure 11.14a: Effect of temperature on molybdenum recovery.
extracted as sodium molybdate. The sodium molybdate solution was treated with HCl to adjust
the pH to 2 and then purified by adsorption on activated charcoal with ammonia and the
solution was heated at 90
◦
C to produce ammonium polymolybdate which on calcination at
450
◦
C produced highly pure (99.9%) MoO
3
. A schematic diagram of the overall process is
shown in
Fig. 11.15 [657]
.
In another related study published recently by Karr et al.
[658]
, roasting of spent catalyst with
NaCl was also found to be effective for Mo recovery from a spent hydrorefining catalyst that
contained 21.8 wt.% MoO
3
, 4.97 wt.% NiO, 1.54 wt.% Co
3
O
4
, 60.4 wt.% Al
2
O
3
, and
Figure 11.14b: Effect of soda ash addition on recovery of molybdenum.