2-octanol extraction - stripping

Table 62. Typical purity of tantalum and niobium oxides prepared from strip solutions after extraction with 2-octanol. Impurity level is given in ppm.

In almost all theoretical studies of AGf , it is postulated or tacitly understood that when an ion is transferred across the 0/W interface, it strips off solvated molecules completely, and hence the crystal ionic radius is usually employed for the calculation of AGfr°. Although Abraham and Liszi [17], in considering the transfer between mutually saturated solvents, were aware of the effects of hydration of ions in organic solvents in which water is quite soluble (e.g., 1-octanol, 1-pentanol, and methylisobutyl ketone), they concluded that in solvents such as NB andl,2-DCE, the solubility of water is rather small and most ions in the water-saturated solvent exist as unhydrated entities. However, even a water-immiscible organic solvent such as NB dissolves a considerable amount of water (e.g., ca. 170mM H2O in NB). In such a medium, hydrophilic ions such as Li, Na, Ca, Ba, CH, and Br are selectively solvated by water. This phenomenon has become apparent since at least 1968 by solvent extraction studies with the Karl-Fischer method [35 5]. Rais et al. [35] and Iwachido and coworkers [36-39] determined hydration numbers, i.e., the number of coextracted water molecules, for alkali and alkaline earth metal... 

Fig. 7. Effects of flow rates of (A) feed solution, (B) organic solvent, and (C) stripping base solution on extraction of lactic acid by Alamine 336 (30% [v/v] in 2-octanol) at pH 4.5. Only one flow rate was varied in the range studied whereas the other two flow rates were kept at 80 mL/min. The feed contained 10 g/L of lactic acid in (A) and (C), and 40 g/L of lactic acid in (B). The curve and horizontal lines are from the model simulation.

An initial experiment involving the treatment of small irradiated Pu/Al targets for the production of americium 243 and curium 244 was carried out in France in 1968 (2). The chemical process was based essentially on the use of a system comparable to the Talspeak system. After plutonium extraction by a 0.08 M trilaurylammonium nitrate solution in dodecane containing 3 vol % 2-octanol, the actinides (americium, curium) were coextracted with a fraction of the lanthanides by a 0.25 M HDEHP -dodecane solvent from an aqueous solution previously neutralized by A1(N0 ) x(0H)x and adjusted to 0.04 M DTPA. The actinides were selectively stripped by placing the organic phase in contact with an aqueous solution of the composition 3 M LiN0 -0.05 M DTPA. While this experiment achieved the recovery of 150 mg of americium 243 and 15 mg of curium 244 with good yields, the process presented a drawback due to the slow extraction of Al(III) which saturates the HDEHP. This process was therefore abandoned. 

The treatment scheme for the first irradiated targets (8) was based on the TLAHNO-/DTPA system implemented by liquid-liquid extraction. After dissolution of the Pu/Al targets by nitric acid, the solution was adjusted to low acidity by addition of Al(NO-)-. (OH) and then countercurrently contacted with an organic isoiution of the composition 0.64 M TLA.HNO- in dodecane containing 3 vol % 2-octanol. The co-extracted elements are then separated by selective stripping as follows ... 

Mandal et al. (in preparation) incorporated p-cyclodextrin in an aqueous solution (0.7 M P-cyclodextrin, 7.5% NaOH, 37.5% urea, pH = 12) and employed it as a CLM in a permeator containing 300 symmetric hydrophobic feed fibers and 300 similar strip fibers. The feed was an equimolar (0.005 M) mixture of structural isomers o-nitroaniline and /7-nitroaniline in 80% octanol-20% heptane with the same solvent mixture as the strip liquid (Figure 3a). They obtained a selectivity of almost 5 for /7-nitroaniline over the ortho isomer. The operation was stable. The longest run continued for a period of almost two days with the feed solution and the strip solvent in coxmtercurrent flow. This successful separation indicated that employing a reflux arrangement at the end of the extraction cascade, it would be possible to continuously separate structural isomers into high purity (99%). ... 

---