Adsorption isotherm, kinetic, and optimization studies for copper (II) removal from aqueous solutions by banana leaves and derived activated carbon

Abstract

This study presents a unique, inexpensive, abundant availability in nature and insoluble in most solvents adsorbents. Banana leaves (BL) which dried and grinded, used as adsorbent and precursor for activated carbon, a comparison study was investigated between (BL) powder as the same and produced banana leaves activated carbon (BLAC) as adsorbents for copper (II) removal from aqueous solutions. The effects of initial concentration, temperature, pH, dose, and agitation speed were investigated. Results of the adsorption process exhibited significant sensitivity toward the copper ions at optimum conditions; the copper ions uptake was enhanced with increasing contact time, a dose of adsorbents, agitation speed, and temperature, and achieved appropriate selectivity and optimum removal efficiency of 52% and 83% for BL and BLAC, respectively at pH 5. The adsorption isotherm studies were performed and the resulted data were analyzed using Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R) equations. The Langmuir isotherm equation displayed a better fit for both adsorbents with regression coefficient (R2 = 0.999) and the maximum adsorption capacity of copper (II) was obtained as 48.7 and 66.2 mg/g for BL and BLAC, respectively. Values of thermodynamic parameters (ΔG, ΔH, and ΔS) of copper (II) adsorption onto the surface of BL and BLAC revealed the feasibility, spontaneity, and endothermic nature of copper (II) adsorption on these surfaces. The kinetics studies indicate that the adsorption process follows the pseudo-second-order kinetic model, Eloivch model, and fitted well with the intraparticle diffusion model. The experimental results confirmed the superiority of the created adsorbents compared to the opposite used.