The Potential of Date-palm Leaf Ash as Low-cost Adsorbent for the Removal of Pb(II) Ion from Aqueous Solution

This study investigated the feasibility of Date-palm) Phoenix dactylifera (Leaf Ash (DLA) (an inexpensive agricultural-byproduct) as an application to adsorb Pb(II) ions. An adsorption process was carried out to evaluate initial concentration Pb(II) ions, adsorbent dose, contact time, pH and temperature on the systematic removal of Pb(II). The effects were examined and results showed that removal efficiency decreased with an increase of initial Pb(II) concentration and optimum removal efficiency of 99.72% was at 50 mg/l Pb(II) solution, 0.5 g/l DLA dose and pH level of 5. The results showed that with increased dose of adsorbent dose, Pb(II) adsorption also increased. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm models by nonlinear regression analysis at 20, 30 and 40 ˚C. It was found that the Langmuir isotherm model fitted better than the Freundlich isotherm model. However, the kinetic adsorption of Pb(II) ions was tried using three kinetic models, the pseudo-first-order, the pseudo-second-order and the intra-particle diffusion model and these tests demonstrated that the overall adsorption process was the one most suited to the pseudo-second-order kinetic model. Thermodynamic parameters, Gibbs free energy (∆G˚), enthalpy (∆H˚), and entropy (∆S˚) were also evaluated, with application of the van’t Hoff equation that describes the dependence of equilibrium constant on temperature. Final evaluation of the thermodynamics of Pb(II) adsorption onto DLA demonstrated that adsorption was spontaneous and endothermic.