pH-Controlled precipitation of cobalt and molybdenum from industrial waste effluents of a cobalt electrodeposition process

Bioleaching of spent hydro-processing catalyst using acidophilic bacteria and its kinetics aspect

“…However, at spent catalyst amount of 30 g/L or 50 g/L, the redox potential of the aqueous solution increased. As a result, Mo 3+ transform into MoO 3 or MoO 2 and precipitates with the solid phase [29]. It has also been reported that in hydrometallurgical processes Mo is usually recovered by precipitating it at lower pH and higher redox potential as molybdenum trioxide [30,31].…”

Prospects for the incorporation of cobalt into α-Fe2O3 nanorods during hydrothermal synthesis

“…, being too active to exist as atomic cobalt in acidic or neutral solution [32]. Cobalt has been shown to precipitate from solution at values of pH [ 8 [33]. Accordingly, the HS of this sample set (S1 to S4) was repeated at pH *8 (Samples S5 to S8), with a view to promoting the precipitation of Co during a-Fe 2 O 3 growth.…”

“…Again, the phosphate surfactant acts to suppress a-Fe 2 O 3 NP growth and drives the x value in Co x Fe (3-x) Recognising that Co 2? cations prefer to stay in solution at values of low pH [32,33], preformed Co 3 O 4 NPs (from Sample S10) and CoFe 2 O 4 NPs (from Sample S18) added to FeCl 3 precursor solution with 3 mg NH 4 H 2 PO 4 and reheated at 200°C for 120 min (Samples S13* and S19*, respectively), allowed the effect of cobalt dissolution on a-Fe 2 O 3 NR growth to be examined.…”

“…6d, arrowed), positioned at the same 2h value as the highest peak intensity of Sample S10, was attributed to {311} Co 3 The suggestion is that the cobalt atoms at the CoFe 2 O 4 NP surfaces dissolve into solution as Co 2? cations at low pH values [32,33], leaving vacancies in the CoFe 2 O 4 NP surface crystal lattice [56]. When a CoFe 2 O 4 NP attaches to an a-Fe 2 O 3 NR surface, these vacancies may be filled by surface Fe atoms from the a-Fe 2 O 3 .…”

“…Further, pH control is recognised as being key in the precipitation of cobalt. Hence, detailed investigation is required to elucidate the role of pH in the doping of a-Fe 2 O 3 [32][33][34].…”