Metal concentrations in the organic

A distribution isotherm is then constructed by plotting the metal concentration in the organic phase against the concentration in the aqueous phase, as a function of the phase ratio. An example of such an isotherm is shown in Fig. 7.1, for the extraction of nickel by DEHPA(Na) at pH 6, showing three different concentrations of extractant [1]. 

As stated earlier the polymeric species are often involved in the extraction of metal carboxylates. Therefore, the extraction equilibrium is sometimes more complicated than in the chelate extraction system. As is evident from the following treatment, it is advantageous and often indispensable to study the total metal concentration in the organic phase [Eq. (8)] instead of the conventionally utilized distribution ratio of the metal [Eq. (7)]. 

The observable parameter that describes the behavior of a metal ion in any separation process is the distribution ratio, simply the ratio of the total metal concentrations in the organic (or resin) phase to that in the aqueous phase. For all systems, therefore, the distribution ratio is... 

Complex formation in the organic phase is high so that the metal concentration in the organic phase can be neglected ... 

Ecological Analysts, Inc. 1981. The Sources, Chemistry, Fate, and Effects of Chromium in Aquatic Environments. (Avail, from American Petroleum Institute, 2101 L St., N.W., Washington, D.C. 20037. 207 pp.) Eisler, R. 1981. Trace Metal Concentrations in Marine Organisms. Pergamon Press, NY. 687 pp. 

For most exploratory work, analysis of the organic phase is not necessary. If no volume change of the phases occurs and no third phase or crud is formed, the analysis of the aqueous raffinates is sufficient, since the metal concentration in the solvent can be readily calculated from the initial metal concentration of the feed solution and the phase ratio used. 

Catalysis is a valuable and indispensable tool in organic synthesis. Transition metals, most preferably precious metals, are often used. However, potential residual metal contamination from these heterogeneously or homogeneously catalyzed reactions may be detrimental to product quality or, as in the case of active pharmaceutical ingredients (API s), the metal concentration in the final product may be regulated. Degussa s Deloxan Metal Scavengers recover valuable precious metals from reaction mixtures and reduce the metal concentration in process solutions to an acceptable level (<5 ppm). 

Kv is not a constant and may vary by several orders of magnitude. It is affected by element properties and both solid phase and pore water characteristics. Knowledge of the relationship between soil characteristics and Kp values enables the calculation of the distribution of heavy metals over the solid phase and pore water for different soils. When coupled to an uptake model for metals by biota that are directly or indirectly exposed via the pore water, the relationships for predicting Kp values may be used to predict metal uptake for these organisms on the basis of the metal concentration in the solid phase and some selected soil properties. The latter should, like the total concentrations, be easily determinable. 

The extraction kinetics of Ni(II) and Zn(II) with //-alkyl-substituted dithizone (HL) in chloroform has been studied by HSS method [7]. The observed extraction rate constants was linearly proportional to both metal ion concentration in the aqueous phase [M2+] and ligand concentration in the organic phase [HL]0, and inversely to the hydrogen ion concentration [H + ] in the aqueous phase. Thus, the rate law for the extraction was determined as... 

The equilibrium metal concentrations in the aqueous and organic phases and the equilibrium acidity of the aqueous phase are presented along with the calculated values for the distribution coefficient in Table IV. 

The practical significance of metal release from sulfide minerals has focussed attention on the mechanisms which operate under the conditions of the highest metal concentrations in the aqueous phase of field situations, and on the associated organisms. The most studied substrates have been iron and copper sulfide minerals and the unique position of T. ferrooxidans as the principal terminal member of the pH-dependent successions of both sulfur-oxidizing and iron-oxidizing bacteria has led to intensive investigation of this... 

The HNO3 dependencies of the extraction of U(VI) and Th(IV), shown in Figure 4, should be considered of operational significance only since several parameters vary simultaneously as the equilibrium aqueous HNO3 concentration is varied. For example, NOl activity and nitrato complexing of metals in the aqueous and the free extractant concentration in the organic phase may vary as the aqueous HNO3 concentration is varied. 

The degree of the metal extractions depends on its concentration. Por example, with increasing europium concentration the distribution coefficients in the alkali-DOBTA system decrease, while in the alkali-tartaric acid system a maximum at 7x10 4 M Eu concentration is observed. As we suggested the enhancement in the metal distribution coefficient is evidently due to the metal polymerization in the organic phase, and the decrease is caused by polymerization in the aqueous phase, which eventually results in low extractable polymer form. The latter assumption is supported by the fact that as the alkali concentration increases the maximum on extraction curves undergoes a shift towards lower concentration of the metal. 

As DOP concentration in the organic phase increases from 0.01 to 0.05 JS, extraction of Am and Eu increases, the best results being obtained with the use of 0.04 M. DOP in toluene solutions. Further enhancement in the extractant concentration is not reasonable due to intermolecular hydrogen bonds between DOP molecules. It follows from the slope of the log D = f log /DOP/ curves, that in the extraction from 1 M NaOH the metal/reagent ratio in the compound being extracted is 1 2. The elements appear to be extracted from 1 M NaOH in the form of hydrated compounds. 

Also selective extractions were carried out in order to obtain information about solid speciation of the elements. The results (Table 8.4) show that the metals concentration in the adsorbed, carbonade, organic and sulphide fractions are in the natural range. The values also show that the extraction sequence is, in general, in the order ... 

A high percentage of recovery is possible and recovery checks can be carried out by spiking the sample with metals of interest. However, if all the metals present in the organic liquid are in a reasonable concentration it may be possible to dilute it in a solvent that is compatible with ICP-OES. 

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