Aqueous-phase equilibrium

Fig. 3. Plots of initial mineralization rates (IMR) versus equilibrium aqueous phase concentrations for naphthalene-degrading bacteria. Open circles represent Capac soil, closed circles represent Colwood soil, and squares represent soil-free control data points. Reprinted with permission from Guerin and Boyd (1992). Copyright (1992) American Society for Microbiology.

It is safe to conclude that there is no equilibrium aqueous phase chemistry of Tl2+. 

Am distribution coefficients, D. s, as a function of the equilibrium aqueous phase acidity of the feed were obtained. (D is defined as the ratio of the Am concentration in the organic phase to that in the aqueous phase when the phases are in equilibrium.) These results are shown in Figure 11. The D s vary from 6 to 60 for acidities from 0.4 to 0.03... 

Figure 3. Effect of CA W equilibrium aqueous phase acidity on DBBP extraction...

The hydrogen ion activity of the equilibrium aqueous phase was measured with Beckman pH and saturated calomel electrodes. The reference voltage Ea of the system was calculated using the Nemst Equation and the electrode measurement of standard buffer solutions. For all pH electrode measurements Ea varied only slightly between 414 and 417 mV. The data are shown in Table III and the calculated hydrogen ion activity [H+] is based on the average of the two values of electrode voltage (El and E2). 

For pH <5, the dissolved carbon dioxide does not dissociate appreciably and its effective Henry s law constant is, for all practical purposes, equal to its Henry s law constant. For a gas-phase C02 mixing ratio equal to 330 ppm, the equilibrium aqueous-phase concentration is 11.2 pM (Figure 7.4). As the pH increases to values higher than 5,C02 H20 starts dissociating and the dissolved total carbon dioxide increases exponentially. However, even at pH 8, Hq0i is only 1.5 M atm-1, and practically all the available carbon dioxide is still in the gas phase. The aqueous-phase concentration of total carbon dioxide increases to hundreds of pM for alkaline water. 

The problems associated with the M state of the elements of group III have been noted previously (cf. Sections 25.1.13 and 25.2.3). The TP ion has been identified in pulse radiolysis decomposition of aqueous Tl2S04, and in y-irradiated frozen aqueous solutions. Thallium(II) has also been invoked as an intermediate in the photochemical reduction of aqueous Tl" solutionsbut there is dispute as to its involvement in redox reactions. It is safe to conclude that there is no equilibrium aqueous phase chemistry of TP" ". 

Equilibrium aqueous phase composition (%) Equilibrium [HsPO/iltora) (mM) Selectivity H2SO4/ H3PO4 ... 

Exp. Equilibrium aqueous phase concentration (%) Equilibrium [Flor (g/L) Selectivity F/PO4... 

To quantify the effects of mixed waste con sition on wettability and interfacial tension equilibrium, aqueous phase receding contact angle and interfacial tension were measured. Inter cial tension was measured ida a spinning drop tensiometer Model 500 (University of Texas, Austin, TX) and contact angles were obtained using axisymmetric drop shape analysis (17) on quartz slides. Contact angles are reported through the aqueous phase. 

Figure 15.2-4 shows measured equilibrium data for extraction of phenol from an aqueous feed containing 5000 ppm phenol at 22.5 C into a solvent composed of 25% w/w TOPO in diisobutyl ketone (DIBK). Here the data are expressed as Ku, the concentration (mass or moles/volume) in the solvent divided the concentration of phenol in the equilibrium aqueous phase. Predicted curves are drawn for a theoretical model, in which fitted parameters are K, the physic (or unreacted) distribution coefficient, and Kg, the equilibrium constant of a complexation reaction with one-to-one stoichiometry. The curves are drawn for... 

The effect of rhamnolipids on the partitioning of the PAHs, naphthalene, fluorene, phenanthrene and pyrene from NAPLs was examined [71]. Enhanced partitioning of the PAHs, occurred even with humic acid-smectite clay complexes, with the exception of naphthalene. The rhamnolipids sorbed onto the solids increasing the amount of solid phase PAHs. These solids are typical of those found in the subsurface and thus indicate the potential for enhancement of the in situ partitioning of PAHs. The equation dC/dt = k(C - C) was used where Cgq is the equilibrium aqueous phase concentration and C the PAH in the aqueous and solid phases. At biosurfactant concentrations above the CMC, k values were lower since there was competition for the PAH between the sorbed biosurfactants and micelles. 

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