3.2 Adsorption isotherms
The adsorption isotherm is one of the most important approaches to
illustrate the mechanism of the adsorption systems. The adsorption
isotherms of γ-tocopherol on silica gel were fitted using Langmuir model
(Fig. 3a) and Freundlich model (Fig. 3b), respectively. The parameters
of Langmuir and Freundlich models were summarized in Table 1.
From Fig. 3a and Fig. 3b, the Langmuir model can be considered as a
better model for describing adsorption equilibrium due to its higher
correlation coefficient (R2 = 0.9944), followed by the
Freundlich model with an R2 value of 0.8997. The value
of Qm gives the maximum monolayer adsorption capacity of
the adsorbent. In most cases, the constant n of the Freundlich equation
shows the adsorption intensity, and the n value between 1 and 10 shows
beneficial adsorption (Duran et al. 2011). The n value of the adsorption
model was 4.36, which indicated that the adsorption on silica gel
(200-300 mesh) can easily take place.