Hydrophobic volume variation

An intuitive explanation of the oscillatory volume variations is given by Yoshida in Ref [8] it is based on hydrophobic effects that induce a difference of swelling rate between the oxidized and the reduced states of the catalyst. For a small piece of gel, the oscillations occur homogeneously [39]. But when the chemical wavelength is smaller than the system size, some inhomogeneous behavior in the form of waves may arise [8]. 

Artola-Garicano et al. [24] measured the free and total concentrations of AHTN and HHCB in the influent of a wastewater treatment plant in The Netherlands every 2 h over a 24-h period. Their data indicate that the variation in total concentration of AHTN and HHCB in influent was 19%, while the variation in free concentration was less than 10% over the 24-h period. These authors suggested that fluctuations in water volume cause fluctuations in total concentrations however, for hydrophobic FMs such as AHTN and HHCB, the solids act as a reservoir and stabilize the free concentrations. 

Williams et al. have also investigated the effect of variation of the DVB content of the monomer phase on the cellular structure of the resulting foam [130]. The phase volume and surfactant and initiator concentrations were kept constant while the DVB content was increased from 0 to 100% this caused a drop in average cell size from 15 pm to 6 pm. The increased hydrophobicity of DVB compared to styrene probably results in a more stable emulsion, giving a slower rate of droplet coalescence and smaller average cell size. 

Variation of v. The last mixed micelle case studied were mixtures in which the volume of the hydrophobic tails was varied by mixing monoalkyl and dialkyl cationic surfactants (DTAB/DDAB). The aggregate structures found as a function of composition are detailed in Table IV. TTiey range from lamellar packed liquid... 

Other parameters (molar refractivity of the molecules/substituents, molar volume, Taft s steric constant, and Verio op s sterimol parameters) also appear in several QSAR. In some cases, these parameters correlate all of the observed variations in activity, but they do not seem to play as important a role as hydrophobicity for the data sets that we have examined. 

Figure 13.11 shows the principal characteristics of Sulzer CY packing for water distillation service [M6]. The optimum throughput is said to be at 75 percent of flooding, at which the F factor is 1.7. At this load, the gas-phase pressure drop is about 4 Torr/m, the Uquid holdup is about 6 percent of the packed volume, and the observed height of a transfer unit (htu) has been found to be between 6.5 and 12 cm. The observed variations in htu are attributed to variations in the wetting of the packing, which is impaired by traces of oil and other hydrophobic impurities in the water. 

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