Concentrations, toluene mass distribution

Toluene concentrations Toluene mass distribution Volume of four phases... 

The experimental zero-shear viscosities obtained for polystyrene (PS) of different molar masses (with a very narrow molar mass distribution Mw/Mn=1.06-1.30) and different concentrations in toluene and fra s-decalin are plotted as log r sp vs. log (c- [r ]) in Fig. 6. 

Polymers in solution or as melts exhibit a shear rate dependent viscosity above a critical shear rate, ycrit. The region in which the viscosity is a decreasing function of shear rate is called the non-Newtonian or power-law region. As the concentration increases, for constant molar mass, the value of ycrit is shifted to lower shear rates. Below ycrit the solution viscosity is independent of shear rate and is called the zero-shear viscosity, q0. Flow curves (plots of log q vs. log y) for a very high molar mass polystyrene in toluene at various concentrations are presented in Fig. 9. The transition from the shear-rate independent to the shear-rate dependent viscosity occurs over a relatively small region due to the narrow molar mass distribution of the PS sample. 

The concentrations and the mass distribution of toluene in the four phases, as calculated from this set of equations, are presented in Table 14.4. As seen in the table, the major part of the toluene, i.e., 68.9%, remains in the vadose zone as free NAPL, 27.6% is adsorbed on the surfaces of solid particles, and only 3.5% is distributed between the aqueous and gas phases. Free NAPL occupies only a small part of the available pore volume, and it is not expected to disturb the movement of air through the contaminated zone. 

Concentrations, Mass Distribution of Toluene, and Volume Occupied by the Four Phases in the Vadose Zone... 

An organic compound present in low concentration in water is being extracted into toluene. The distribution coefficient of A between the aqueous phase and toluene is kao = 25. The aqueous-phase mass-transfer coefficientfor solute AiskAM/= 1-06 x 10 cm/s. The organic-phase mass-transfer coefficient is of the same order as kAw Calculate K w and Kao. (Ans. Xak,= 1-06 x 10 cm/s Kao= 4.2 x 10 " cm/s.)... 

Some assumptions were made for the derivation of Equation [4.4.54], especially the partial specific volume, the refractive index, and the derivative dn/dw2 must not depend on the molar mass distribution of the polymer. If one further assumes that the Flory-Huggins X-function depends only on temperature and concentration, but not on molar mass, the partial derivative of the chemical potential can be calculated by Equation [4.4.13a] to obtain values of the x-function. Scholte carried out experiments for solutions of polystyrene in cyclohexane or toluene at different temperatures and in a concentration range of 0 to 80 wt%. 

Fig. 3. Specific states of solution of narrowly distributed polystyrene in toluene as a function of the molar mass and the polymer concentration [19,40]...

Fig. 15. Influence of molar mass and concentration on the slope of the flow curve for narrowly distributed polystyrene in toluene (n=f(c) for Mw=l-107g/mol n=f(Mw) for c= 0.06 g/ml)...

Step 4 Estimate the effectiveness factor i) for the removal and the cleanup time required to obtain a residual toluene concentration of 150 mg/L. The phase distribution calculations carried out in Step 2 indicate that the equilibrium concentration of toluene in the gas phase is Ca equil = 109 mg/L (see Table 14.4). The concentration measured in the extracted air during the field tests is lower, at Q,flew = 78 mg/L, indicating that the removal effectiveness is limited either as a result of mass transfer phenomena or the existence of uncontaminated zones in the airflow pattern. The corresponding effectiveness factor is T = 78/109 = 0.716. 

The second complicating factor is interfacial turbulence (1, 12), very similar to the surface turbulence discussed above. It is readily seen when a solution of 4% acetone dissolved in toluene is quietly placed in contact with water talc particles sprinkled on to the plane oil surface fall to the interface, where they undergo rapid, jerky movements. This effect is related to changes in interfacial tension during mass transfer, and depends quantitatively on the distribution coefficient of the solute (here acetone) between the oil and the water, on the concentration of the solute, and on the variation of the interfacial tension with this concentration. Such spontaneous interfacial turbulence can increase the mass-transfer rate by 10 times 38). 

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