A new insight into the pseudo-first-order model: investigation of the adsorption mechanism of amoxicillin, diclofenac sodium, and methylene blue on various adsorbents based on the pseudo-first-order rate constant

Abstract

In this study, a new approach has been proposed to determine the adsorption mechanism based on the pseudo-first-order rate constant (PFO). The mathematical expression of the PFO rate constant based on the Langmuir adsorption mechanism was obtained. This expression includes a new parameter called the contact surface area of the adsorbed molecule with the adsorbent. By analyzing the relationship between the PFO rate constant and the initial concentration of the adsorbate, this parameter can be calculated. The value of this parameter provides information about the orientation and adsorption mechanism of a molecule on the adsorbent surface. The proposed method was evaluated using the adsorption data of amoxicillin, diclofenac sodium, and methylene blue on various adsorbents; the results were in good agreement with experimental data.