Aqueous-phase aging

Acenaphthene occurs naturally in coal tar. Based on laboratory analysis of 7 coal tar samples, acenaphthene concentrations ranged from 350 to 12,000 ppm (EPRl, 1990). Detected in Dyr aged coal tar film and bulk coal tar at concentrations of 5,800 and 5,900 mg/kg, respectively (Nelson et al, 1996). A high-temperature coal tar contained acenaphthene at an average concentration of 1.05 wt % (McNeil, 1983). Lee et al. (1992a) equilibrated 8 coal tars with distilled water at 25 °C. The maximum concentration of acenaphthene observed in the aqueous phase was 0.3 mg/L. 

The pronounced reduction in IFT aging observed at low temperatures is attributed to a marked reduction in the rate at which interfacially active species congregate at citrus oil/aqueous phase interfaces when such mixtures are stored cooled. This is believed to reflect primarily a reduction in rate at which these species are produced in systems that are kept at low temperatures. If cooling simply reduced the solubility of interfacially active species that existed initially in these systems, IFT should decrease, since reduced solubility favors adsorption at an interface. 

Duplicate and triplicate IFT aging curves were obtained at one or two temperatures for most of the interfaces characterized in this study. The replicate IFT data reported in Figures 1,3,4,7,8 and 10-14 show that many IFT aging curves for citrus oil/aqueous phase interfaces differ by a maximum of 1.7mJ/m2. Replicate curves often differ by less than lmJ/m2. Because each IFT aging experiment involved formation and separation of a new complex coacervate and supernatant phase, replicate IFT aging curves measure the combined effect that several factors have on reproducibility. These factors include variability of the complex coacervation procedure, protocol followed for separation of the coacervate and supernatant phases, and the IFT measurement process itself. The variability in solids content of replicate coacervate and supernatant phases shown in Table 1 could contribute to the observed IFT variability. 

We observed that for freshly contaminated soil, the compound readily desorbed into the aqueous phase and was available for microbial consumption whereas for soils containing mostly the non-labile material, the contaminant availability was limited by the mass transfer into the aqueous phase. The fraction of contaminant, which is irreversibly bound to soil is typically present in micropores or chemically bound to soil humic matter and thus is not accessible for microbial utilization. These observations are in agreement with those reported for other chemicals in the literature. It is believed that the longer the contaminant age within the soil the lower the fraction of the contaminant that will be bioavailable. The observations have significant implications to the current remedy and the possibility of natural attenuation at the site. 

Fig. 5.13 shows the general form of the curve relating the fraction of C3S consumed (a) to time in a paste of w/s 0.5 at about 25°C and with moist curing. Such curves have been determined using QXDA for unreacted C3S (e.g. Refs K20,OI0), though the precision is low for values of a below about 0.1. At low values of a, other methods are available, such as conduction calorimetry (e.g. Ref. P22), aqueous phase analyses (e.g. Ref. B63) or determinations of CH content or of non-evaporable water. At very early ages, it may be necessary to allow for the fact that the property determined depends on the nature of the hydration products e.g. precipitation of C-S-H begins before that of CH. 

Stability depends on the age of the latex, as shown in figure 5 Presumably the raising of the stability level by storage can be attributed to the decreasing content of residual monomer. The data in this figure were obtained some years ago before special attention was focused on the residual monomer because of the health hazard arising from exposure to it. Initially the monomer content in the particles of this latex was 6-8 per cent. Only a small fraction of the monomer is dissolved in the aqueous phase. 

Because C1 stays predominantly in the aqueous phase, it is mainly applied for hydrological studies, e.g. on the time of transport of water within deep layers, the rate of erosion processes and the age of deep groundwaters. In the case of ground-waters without access of cosmogenic C1, the production of C1 by the reaction Cl(n, ) C1 induced by neutrons from spontaneous fission of uranium contained in granite has to be taken into account. 

Boucher M.E., Chaala A., Pakdel H. and Roy C. (2000), Bio-Oils Obtained by Vacuum Pyrolysis of Softwood Bark as a Liquid Fuel for Gas Turbines. Part II Stability and Ageing of Bio-Oil and its Blends with Methanol and a Pyrolytic Aqueous Phase Biomass Bioenergy, In press. 

After aging at 20 °C for some hours the aqueous phase of Raffo sols contains lower polythionate anions and the amount of elemental sulfur increases resulting eventually in the crystallization and precipitation of a-Sg [26] see Eq. (12) ... 

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