Thermodynamics studies on the adsorption of phenol from aqueous solution by coffee husk activated carbon

Abstract

Activated carbons (ACs) obtained from coffee husk by KOH activation at 650 (ACK-650) and 750 o C (ACK-750), were used as an adsorbent for the adsorption of phenol from aqueous solution. The ACs was characterized by SEM, EDX, BET, and Boehm titration techniques. The experimental equilibrium data of phenol adsorption was analyzed by eight isotherm models, which are four two-parameter equations (Langmuir, Freundlich, Elovich, and Temkin) and four three-parameter equations (Redlich-Peterson, Sips, Radke-Prausnitz, and Tóth). The results reveal that in general, three-parameter isotherms can provide better prediction than two-parameter isotherms. The best fit for ACK-650 sample is Sips isotherm, while for ACK-750 sample is Redlich-Peterson isotherm. Isosteric heat and thermodynamic parameters ΔG o , ΔH o , and ΔS o of the adsorption were determined, and the results showed that the adsorption of phenol was exothermic and physical in nature. A scale-up of a batch system is designed for 2 to 10 L phenol with an initial concentration of 100 mg L -1 .

KOH activated carbons from Brazil nut shell: Preparation, characterization, and their application in phenol adsorption

“…At low adsorbate concentrations, the Sips model reduces to the Freundlich model, and at high concentrations, it predicts monolayer formation, which is characteristic of the Langmuir isotherm. Kamiński et al (2020) and Ta et al (2021) also demonstrated that the Sips model was more suitable for representing phenol adsorption equilibrium data using activated carbons.…”