To address the issue of wastewater decontamination, this meticulous study leverages the concepts of probabilistic physics formalism to depict the adsorptive equilibrium data of two widely used pesticides: 2,4-dichlorophenoxyacetic acid (2,4-D) and carbofuran on phosphoric acid-activated peach stone biochar. Numerically, we proposed three advanced models─monoenergetic linking monolayer scenario, bienergetic linking monolayer scenario, and multilayer linking with saturation scenario─to fit the experimental data. The analysis of data-theory accuracy through χred2 and Radj2 reveals that the adhesion of both toxic compounds occurs through a single monolayer at a single energy level. Based on the most probable scenario, our investigation demonstrates that an increase in temperature enhances retention on activated carbon, enabling a more optimized purification process. Regarding the equilibrium adsorption, a higher adsorption capacity is observed for 2,4-D (500 mg·g–1) compared to carbofuran (250 mg·g–1). Steric analysis further indicates that the number of adsorbate molecules per site, n, ranges from 2.46 to 1.65 for 2,4-D and from 1.29 to 1.68 for carbofuran over the temperature range of 25–65 °C. These values suggest multimolecular adsorption, in which a single binding site accommodates multiple adsorbate molecules, often with nonparallel anchoring orientations. As the temperature rises from 25 to 65 °C, the density of adsorption sites, nm, increases by a factor of 1.9 for 2,4-D and by a factor of 1.3 for carbofuran, reflecting a more pronounced temperature-dependent availability of active sites for 2,4-D and suggesting enhanced adsorption capacity at elevated temperatures. At 65 °C, energetic analysis indicates that the adsorption mechanism for both pesticides is primarily physisorption, with adsorption energies not exceeding 40 kJ·mol–1. Specifically, the adsorption energy for 2,4-D is approximately 17 kJ·mol–1, while for carbofuran, it is around 9 kJ·mol–1, reflecting weaker interactions with the adsorbent surface in the case of carbofuran. Pore size distribution characterization indicates that the smaller pore size ranges observed correspond to the microporous region (<2 nm) for both pesticides, while adsorption energy distribution confirms that van der Waals forces are the primary contributors to molecular adhesion. This study concludes that (2,4-D) is preferentially removed compared to carbofuran when in contact with activated carbon, highlighting its superior efficacy for wastewater treatment applications.
Naifar et al. (Wed,) studied this question.