Extractants regime

Criteria 1-3 are difficult to apply and have been used only occasionally to evaluate the extraction regime. 

Finally, it has to be emphasized that both the hydrodynamic parameters and the concentrations of the species involved in the extraction reaction simultaneously determine whether the extraction regime is of kinetic, diffusional, or mixed diffusional-kinetic type. It, therefore, is not surprising that different investigators, who studied the same chemical solvent extraction system in different hydrodynamic and concentration conditions, may have interpreted their results in terms of completely different extraction regimes. 

A mathematically simple case, that occurs frequently in solvent extraction systems, in which the extracting reagent exhibits very low water solubility and is strongly adsorbed at the liquid interface, is illustrated. Even here, the interpretation of experimental extraction kinetic data occurring in a mixed extraction regime usually requires detailed information on the boundary conditions of the diffusion equations (i.e., on the rate at which the chemical species appear and disappear at the interface). 

Miscibihty of lactic acid depends on the concentration of lactic acid in the extraction regime. The value of the physical mass transfer coefficient ki is required for confirming the regime of extraction. This coefficient can be obtained by conducting physical extraction of lactic acid from water. For a batch process, a differential mass balance yields the following equation ... 

The enhanced rate expressions for regimes 3 and 4 have been presented (48) and can be appHed (49,50) when one phase consists of a pure reactant, for example in the saponification of an ester. However, it should be noted that in the more general case where component C in equation 19 is transferred from one inert solvent (A) to another (B), an enhancement of the mass-transfer coefficient in the B-rich phase has the effect of moving the controlling mass-transfer resistance to the A-rich phase, in accordance with equation 17. Resistance in both Hquid phases is taken into account in a detailed model (51) which is apphcable to the reversible reactions involved in metal extraction. This model, which can accommodate the case of interfacial reaction, has been successfully compared with rate data from the Hterature (51). 

The carbon-containing catalyst was treated by ultra-sound (US) in acetone at different conditions. The power of US treatment, and the time and regime (constant or pulsed), were varied. Even the weakest treatments made it possible to extract the nanotubules from the catalyst. With the increase of the time and the power of treatment the amount of extracted carbon increased. However, we noticed limitations of this method of purification. The quantity of carbon species separated from the substrate was no more than 10% from all deposited carbon after the most powerful treatment. Moreover, the increase of power led to the partial destruction of silica grains, which were then extracted with the tubules. As a result, even in the optimal conditions the final product was never completely free of silica (Fig. 12). 

Additionally, our experimental regime now includes extensive use of computer modelling of the polymerisation process and we need to extract chemical, thermal and engineering data for model assembly, verification and for final process improvement. In ICI at Slough we have developed our own approach to the control and data acquisition process used on our semi-technical reactors. 

The SHV flow regime has been studied systematically using the spin-echo and FLASH imaging sequences [39]. Figure 4.4.6 describes the steps for extracting... 

Table 3.3. Concentrations of trace elements in soil solutions extracted by saturated paste from two metal salt-spiked Israeli soils incubated at the saturated paste regime...

Table 6.2. The original metal concentration (HN03-extractable) in native soils and levels of addition to the two Israeli arid soils incubated under the saturated paste regime condition ...

Figure 7.4. Comparisons of decreases in NH4N03-extractable Zn, Ni and Cu in an Israeli loessial soil receiving metal nitrates and incubated under saturated paste, field capacity, and wetting/drying cycle moisture regimes (Han and Banin, 1997,1999, and Han et al., 2001a)...

Figure 7.6. Decreases in bioavailability (as NH4N03-extractable) of Cu, Ni and Zn in an Israeli loess soil receiving metal salts and incubated under field capacity regime for one year (data from Han and Banin, 1999)...

The major ion composition of dispersed soil solutions and saturation extracts from selected soils in California, U.S. Concentrations of trace elements in soil solutions of the California soils that received sludge applications. Concentrations of trace elements in soil solutions extracted by saturated paste from two metal salt-spiked Israeli soils incubated at saturated regime. 

---