Alfa Fiber-Mesoporous Activated Carbon for Copper Ions Adsorption: Comparative Study, Kinetics, Isotherm and Thermodynamic Studies

Abstract

Alfa fiber is used as a low-cost precursor for the production of activated carbon (ACAF) through chemical activation with zinc chloride at 500 °C. In this context, ACAF was applied to the elimination of Cu(II) from water and compared with commercial activated carbon (CAC). The porosity, structural, and thermal stability were characterized by SEM, FTIR, BET, and TGA analysis. The surface oxygen functional groups were analyzed using Boehm's titration. Batch experiments in a stirred reactor were performed to study the effect of the operating parameters on the adsorption process: the pH (2–6), temperature (25–55 °C), and the amount of adsorbent (0.03–0.1 g). Isotherms models: Langmuir, Freundlich, and Dubinin–Raduskevich were tested. The results revealed that the ACAF had a high surface area of 1013 m²/g compared to the CAC adsorbent, 978.85 m²/g. The adsorption isotherms and the kinetics of Cu(II) onto both adsorbents can be described well by the Langmuir isotherm and pseudo-second-order models. The monolayer maximum capacity for ACAF and CAC toward Cu(II) were 41.666 and 21.276 mg/g at 328 K, respectively. Thermodynamics indicated that Cu(II) adsorption on ACAF and CAC adsorbents was spontaneous and endothermic. The adsorption mechanism of Cu(II) ions onto ACAF was an electrostatic interaction.