Sips isotherm

The Sips isotherm was suitable for CPA and 2,4-D among the various isotherms, and the equilibrium adsorption capacity for CPA and 2,4-D onto GAC decreased with increasing pH of the solution. 

This three-parameter equation behaves linearly in the Henry s law region and reduces to the Langmuir isotherm for m = 1. Other well-known isotherms include the Langmuir-Freundlich isotherm or Sips isotherm [Sips,/. Chem. Phys., 16, 490 (1948) Koble and Corrigan, Ind. Eng. Chem., 44,383 (1952)] or loading ratio correlation with prescribed temperature dependence [Yon and Turnock, AlChE Symp. Sen, 67(117), 75 (1971)]... 

Take the example of propane on activated carbon, we plot the isosteric heat (eq. 3.2-19f) versus the fractional loading for the Toth equation using the parameters obtained in Table 3.2-6 (Figure 3.2-11). Just like the case of the Sips isotherm, the isosteric heat decreases with loading, and it shows a weak temperature dependence. 

The parameter allows for interaction among molecules of the same type, and nj allows for other effects of heterogeneity. Eq.(5.2-17) can be viewed as the generalization of the Langmuir-Freundlich (Sips) isotherm. 

It is not difficult to show from eq. (5.3-3la) and the corresponding equation for Sips isotherm in Table 5.3-3 that the hypothetical pure component pressure is given by... 

The adsorption equilibria measurements of N2 and CO2 on activated carbon were performed using a standard static gravimetric method. Further details of these measurements are reported elsewhere." " The Sips isotherm extended to multi-component adsorption was adopted to fit the experimental equilibrium data (Table 9.2). This model has the Langmuirian form applied to non-uniform surfaces and it has been extensively used to model gas adsorption on micro-porous adsorbents and PSA systems. Optimal parameters were found for the adsorption isotherm model, by fitting simultaneously all the data at multiple temperatures. A global isotherm was obtained for each species as illustrated in Figure 9.15." ... 

Figure 9.15 Fitting of the experimental adsorption data for N2 (left) and CO2 (right) by the Sips isotherm model, whose parameters are listed in Table 9.2. Symbols represent experimental data and lines are the isotherm model. Adapted from Ref. 48.

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