Equilibrium, kinetic and thermodynamic assessment of the adsorption of copper (Cu²⁺) ion using <i>Luffa cylindrica</i> seed shell biomass

Abstract

The adsorption of copper (ii) ions from aqueous solution by Luffa cylindrica seed shell biomass was carried out with effects of initial metal ion concentration, solution pH, contact time, adsorbent dose and temperature of the process investigated. An optimum adsorbent dosage of 3.0g showed maximum metal uptake capacity (qe) of 1.9229 mg/g (98.2%) for an initial metal ion concentration of 2.0 mg/L and pH 5.5. Sorption equilibrium time was observed in 30 minutes. The equilibrium adsorption data were analyzed using Langmuir, Freundlich, and Temkin adsorption isotherm models. Temkin isotherm yielded the best fit to the experimental equilibrium adsorption data with a correlation coefficient (R²) of 0.7027. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were used to discuss the kinetics of the adsorption. It was discovered that the adsorption of copper (ii) ions could be described by the pseudo-second-order kinetic model. Thermodynamic parameters such as enthalpy (ΔH⁰) and entropy change of the sorption (ΔS⁰) evaluated showed that the process was spontaneous, feasible and exothermic in nature. The results indicated that L. Cylindrica seed shell biomass can be used as an effective and low-cost adsorbent to remove copper (ii) ions from aqueous solutions.

Keywords: Adsorption, Biomass, Copper (ii) ion, Equilibrium, Kinetics, Thermodynamics