Adsorption of 3-aminophenol and resorcinol on avocado seed activated carbon: Mathematical modelling, thermodynamic study and description of adsorbent performance

Statistical physics calculations were performed to analyze and interpret the steric and energetic parameters of the adsorption of 3-aminophenol and resorcinol on activated carbon obtained from the carbonization of avocado seed via microwave-heating and ZnCl2 activation. Experimental isotherms at 25-50 degrees C and pH 7 were analyzed and interpreted via a monolayer adsorption model with one energy. Results showed that the adsorption of these two pollutants was endothermic and implied a parallel adsorption orientation on activated carbon surface where molecular aggregation was absent in the aqueous solution. Saturation adsorption capacities were maximum at 50 degrees C (i.e., 406 and 455 mg/g for resorcinol and 3-aminophenol, respectively). Calculated adsorption energies ranged from 22.3 to 31.2 kJ/mol and were associated to a physical adsorption. Thermodynamic functions, namely Gibbs free energy, internal energy and entropy, were calculated and discussed for both adsorption systems showing that the removal of this pollutant was spontaneous. These findings contribute to understand the adsorption mechanism involved in the removal of organic pollutants such as phenolic compounds. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Statistical physics calculations were used to analyze and interpret the adsorption of 3-aminophenol and resorcinol on activated carbon obtained from avocado seed through microwave heating and ZnCl2 activation. The results showed that the adsorption was endothermic and the saturation adsorption capacities were highest at 50 degrees Celsius. The calculated adsorption energies ranged from 22.3 to 31.2 kJ/mol, indicating a physical adsorption mechanism.