Adsorption and thermodynamics of lead (II) using seeds of watermelon (SWM) as a low cost sorbent

Salem E. Samra, Bakir Jeragh, Ahmed M. EL-Nokrashy, Ahmed A. El-Asmy

The removal of lead(II) ions from aqueous solutions using seeds of watermelon (SWM) by adsorption technique has been studied. The adsorption % of Pb2+ at pH 6 and 120 min is ~ 97%. Solution pH, initial concentrations of Pb2+ ions and seeds of watermelon, shaking time and temperature were optimized. The Freundlich and Langmuir equations were applied. The thermodynamic parameters viz. the change in Gibbs free energy change (ΔG, - 20.96 kJ mol-1 at 333 K), enthalpy (ΔH, 18.51 Jmol-1) and entropy (ΔS, 63.00 Jmol-1 K-1) were also evaluated. The negative ΔG◦ value indicates that the adsorption is spontaneous thermodynamically. The removal of ~97% of Pb2+ ions was attained using 2 g/L SWM applying the suggested optimum experimental conditions. The procedure was successfully applied to remove Pb2+ from aqueous and different natural water samples.