In-depth study of adsorption mechanisms and interactions in the removal of pharmaceutical contaminants via activated carbon: a physicochemical analysis.

This study presents a theoretical analysis of the adsorption process of pharmaceutical pollutants, specifically acetaminophen (ATP) and diclofenac (DFC), onto activated carbon (AC) derived from avocado biomass waste. The adsorption isotherms of ATP and DFC were analyzed using a multilayer model, which revealed the formation of two to four adsorption layers depending on the temperature of the aqueous solution. The saturation adsorption capacities for ATP and DFC were 52.71 and 116.53 mg/g, respectively. A steric analysis suggested that the adsorption mechanisms of ATP and DFC involved a multi-molecular process. The calculated adsorption energies (ΔE1 and ΔE2) varied between 12.86 and 22.58 kJ/mol, with the highest values observed for DFC removal. Therefore, the adsorption of these organic molecules was associated with physisorption interactions: van der Waals forces and hydrogen bonds. These findings enhance the understanding of the depollution processes of pharmaceutical compounds using carbon-based adsorbents and highlight the potential of utilizing waste biomass for environmental remediation.

Physicochemical assessment of anionic dye adsorption on bone char using a multilayer statistical physics model.

The statistical physics modeling is a reliable approach to interpret and understand the adsorption mechanism of both organic and inorganic adsorbates. Herein, a theoretical study of the adsorption mechanism of anionic dyes, namely reactive blue 4 (RB4), acid blue 74 (AB74), and acid blue 25 (AB25), on bone char was performed with a multilayer statistical physics model. This model was applied to fit the equilibrium adsorption data of these dyes at 298-313 K and pH 4. Results indicated that the global number of formed dye layers on the bone char varied from 1.62 to 2.24 for RB4, AB74, and AB25 dyes depending on the solution temperature where the saturation adsorption capacities ranged from 0.08 to 0.12 mmol/g. Dye molecular aggregation was also identified for these dyes where dimers and trimers prevailed at different operating conditions especially for adsorbates RB4 and AB74. Adsorption mechanism of these dyes was multimolecular and endothermic with adsorption energies from 10.6 to 20.8 kJ/mol where van der Waals interactions and hydrogen bonding could be present. This investigation contributes to understand the physicochemical variables associated to dye adsorption using low-cost adsorbents as bone char.