Abstract
•A physical model was applied to study the adsorption mechanism of two dyes.•The orientation of dyes on the adsorbent surface was described.•An aggregation phenomenon of adsorbed molecules occurred upon adsorption.•Adsorption energies were calculated to characterize the interactions of the systems.
In this paper, the Agaricus bisporus residue (ABR) is employed as an adsorbent to study the adsorption mechanism of two relevant dyes, namely Crystal Violet (CV) and Acid Red 97 (AR97). The adsorption mechanism is theoretically analyzed by application of models derived from statistical physics and the model parameters derived from the best fitting are used for the interpretation of the experimental results. A double-layer model best fitsboth CV and AR97 experimental data,showing that AR97 molecules aggregate only at high temperature forming a dimer (n = 2.55 at T = 328 K). Similarly, CV dye tends to form a monomer with a slight tendency to a dimer at high temperature.AR97 dye is adsorbed through a non-parallel orientation on the ABR surface at most of the investigated temperatures (T = 298, 318 and 328 K), while CV dye is removed via both parallel and non-parallel orientations. The analysis of the adsorption capacity suggests that ABR adsorbent has a stronger affinity to remove AR97. The calculation of the adsorption energies indicated that the adsorption process is a physisorption.