A combined experimental and theoretical investigation via statistical physics for adsorption evaluation of 3 aminophenol (AMP) onto the activated carbon derived from avocado seeds (ASAC) adsorbent

Abstract

With advances in industrialization, water pollution has become an increasing concern, and research must be directed towards developing solutions to address this growing threat to both human health and ecosystems. This current paper is devoted to investigating the adsorption of a phenolic material, 3-aminophenol (AMP)—a raw material used in dye production—on activated carbon derived from avocado seed adsorbent (ASAC) for the purpose of remediating polluted water. Rooted in a statistical physics approach, five distinct models were applied to fit the empirical data: the single-energy monolayer model (Model 1), dual-energy monolayer model (Model 2), tri-energetic monolayer model (Model 3), single-energy bilayer model (Model 4) and dual-energy bilayer model (Model 5). Additionally, a topographic examination was conducted to assess the pore size distribution (PSD) and the adsorbed energy distribution (AED), contributing significantly to the comprehensiveness of linking reaction. It appears that the model 1 provides the most accurate fit, based on the convergence criteria (R², R²_Adj and RMS). By exploiting the involved variables of Model 1, we have quantified three thermodynamic properties (entropy, Gibbs free energy, and internal energy) as a function of distinct temperature and concentration intervals. Stereographic elucidation has revealed that the number of adsorbed molecules per site (n) is typically below 0.5, indicating that adsorbate entities are trapped through the action of one or more adhesion cavities. Meanwhile, the orientation of linked entities is parallel, interacting with two or more sites. The abundance of receptor sites, N_m, significantly increased from 643.8853 to 812.3822 mg/g when the temperature was raised from 303 to 323 K. The computed adhesion energies confirmed were below 40 kJ/mol, indicating an exothermic physisorption associated with van der Waals forces and hydrogen bonding. The adsorbent/adsorbate system is likely spontaneous, as the analysis of Gibbs free energy yielded negative results. Finally, PSD analysis suggested that the adsorbent surface is predominantly composed of macropores. Additionally, AED inspection confirmed the physisorption mechanism.