Porosity breakthrough curves

A plot called a breakthrough curve shows the effluent liquid concentration c divided by the influent liquid concentration c0 as a function of pore volumes of flow (see Figure 26.11). One pore volume of flow is equal to the volume of the void space in the soil. The effective porosity of the soil is determined by measuring a breakthrough curve. 

Water moves through a sand column 2 m long with a specific discharge of 15 cm/hr. Sketch the breakthrough curve of an initially sharp front of a tracer if porosity is 0.3 and median sand grain diameter is 2 mm. (Be sure to indicate the width of the breakthrough curve.)... 

Figures 10.1 (a), (b), (c), (e), (f), and (g) show the composition of the solution exiting from the column at cell 40, as a function of the amount of fluid that has flowed through, a total of three pore volumes. A pore volume is the cross-sectional area of the column times the length times the porosity, and the number of pore volume is equivalent to a dimensionless time. These diagrams, looking at the composition of the fluid exiting from the column versus time, are called breakthrough curves.

The profile side-pore diffusion model simulated the experimental data from the 0.043 mmol/1 column almost exactly and was within the accuracy of the breakthrough data (Figure 6b). Based on the best fit simulation of the Br-breakthrough curve (Figure 2), the immobile-water phase was calculated to be about 5 percent of the total porosity. Apparently, diffusion into and out of this volume of immobile water was responsible for the observed shoulder and tail of the curves of the experimental data. 

The contents of this chapter summarize the several methodologies used to characterize the porosity of activated carbon. The isotherms of the N2 (77 K), CO2 (273 K), H2O (298 K), making use of DR and BET equations, together with a-plots, in association with enthalpies of immersion, characterize porosity in activated carbon. Equilibria data are complemented by the kinetic data from breakthrough curves. 

Liquid chromatography breakthrough curves have been used to characterize the porosity of a dealuminated Y zeolite, and more precisely the mesopores in cavities and the cylindrical mesopores. The methodology presented in this paper shows that the use of several probe molecules with different molecular size and adsorption strength can give an estimation of the zeolite porosity. 

The methodology presented herein is, to our knowledge, the first attempt to characterize the different porosities of dealuminated Y zeolites by breakthrough curves. Even if the results are not fully satisfactory, these first sets of experiments carried out on two pelletized Y zeolites can lead to the following conclusions. 

Table 2 shows, not surprisingly, a clear correlation between the breakthrough times for pentane vapour and the level of porosity in the samples. The uptakes derived from the breakthrou curves show an excellent match to those read from the adsorption isotherm comparison with the uptakes at p/pO = 0.95 show how little of the microporosity is utilised at this test concentration (a result of the low partial pressure). Lillo-R6denas et al have recently shown [6] a correlation between benzene adsorption at 200ppmv and the amount of narrow microporosity as determined by CO2 adsorption at 273K it is assumed that only the narrower micropores are occupied by pentane in these tests. 

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