By Grayson G Camp

Faculty Mentor: Dr Leanna Giancarlo

Abstract

Adsorption processes are essential in environmental science and industry, especially for contaminant removal. Many of these adsorption processes have been described utilizing traditional adsorption isotherms, such as the Langmuir and Freundlich. Even with these known isotherms, a clear understanding of the underlying adsorbate-adsorbate and adsorbate-substrate interactions has not been achieved. Therefore, using a novel ABC isotherm derived by Shimizu and Matubayasi to account for interactions between adsorbates at the interface will allow for a better understanding of the adsorption behavior of methylene blue (MB), Congo red (CR), and methyl blue (MeB) on activated carbon (AC) and other carbon-like surfaces. For MB on AC, the A parameter (-1.51×10-⁹) indicates equal MB-AC and MB-H₂O interactions, while the negative B (-0.00557) reflects weak repulsive forces between adsorbates. In contrast, CR exhibits stronger surface interactions (A = 0.03226) with significant intermolecular repulsion (B = -14.01). MeB shows strong surface affinity (A = 0.02519) and pronounced attractive intermolecular interactions (B = 84.77). The C parameter further captures coverage-dependent behavior, distinguishing steric crowding for MB (-3.014), reduction of lateral repulsive interactions for CR (2873), and cooperative packing for MeB (-2.61×10⁵). Together, these results demonstrate the novel capability of the ABC isotherm to help quantitatively resolve complex intermolecular forces governing adsorption on carbon-like surfaces.