Adsorption of Cd Ions From Aqueous Solution Onto Date Palm Leaflets Powder: Isotherms, Kinetics and Thermodynamics

Abstract

In this study, a series of batch laboratory experiments were conducted in order to investigate the feasibility of date palm leaves powder (DPLP) for the removal of Cadmium from aqueous solution by the adsorption process. Investigation was carried out by studying the influence of initial solution pH, adsorbent dosage and initial concentration of Cadmium, the particle size of (DPLP) and temperature. The single component equilibrium data was analyzed using Langmuir, Freundlich, Dubinin-Radushkevich and Temkin adsorption isotherms. The results showed that equilibrium was reached within 80 min. The used biosorbent gave the highest adsorption capacity at pH 5. The experimental isotherm data were analyzed and modeled. The maximum adsorption capacity, Langmuir’s qmax, improved from 9.80 to 9.90 mg/g as the temperature increased from 15 to 45°C. The enthalpy !H° and entropy !S° values were respectively estimated at 30.33 kJ mol-1 and 0.156 kJ K-1 mol-1 for the process, the negative value of !G° indicates that the adsorption of Cd(II) ions on (DPLP) is a spontaneous process. Three simplified kinetic models including a pseudo-firstorder equation, pseudo-second-order equation and intraparticle diffusion equation were selected to follow the adsorption process. Kinetic parameters, rate constants, equilibrium sorption capacities and related correlation coefficients, for each kinetic model were calculated and discussed. It was shown that the adsorption of Cd(II) ions could be described by the pseudo-second order equation, suggesting that the adsorption process is presumable a chemisorption.