Removal of Heavy Metal Pb(II) Ions from Aqueous Solution Using Pentaclethra Macrophylla and Tetracarpidium Conophorum Seed Shells Based Activated Carbons: Equilibrium, Kinetics and Thermodynmamics Studies
C. F. Okey-Onyesolu *
Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria
O. D. Onukwuli
Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria
C. C. Okoye
Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria
I. C. Nwokedi
Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria
*Author to whom correspondence should be addressed.
Abstract
Biosorption potentials of activated carbons from pentaclethra Macrophylla (PMAC) and Tetracarpidium Conophorum (TCAC) seed shells for the removal of Pb(II) from aqueous solution were investigated. The adsorbents were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray fluorescence (XRF) and x-ray diffraction (XRD). The effects of particle size (0.2 - 1.2 mm), adsorbent dosage (0.2 - 3.0 g), initial pH of solution (2 - 8), initial Pb(II) concentration (100-500 mg/l), temperature (20ºC - 60ºC) and contact time (10 - 180 min) were studied. The percent Pb(II) uptake was found to increase with increase with increase in adsorbent dosage and contact time and decreased with increase in particle size, initial Pb(II) concentration and temperature. Optimum adsorption of Pb(II) was observed at pH 6. The biosorption equilibrium data were well represented by both Langmuir and the Freundlich models. Kinetic data obtained fitted the pseudo-second-order model very well with high correlation coefficient. The calculated thermodynamic parameters (∆G, ∆H and ∆S) indicated that adsorption of Pb(II) onto PMAC and TCAC was exothermic, spontaneous and feasible in the temperature range studied. Results of this work showed that PMAC and TCAC could be used as low cost adsorbents for the removal of Pb(II) from aqueous wastewater.
Keywords: Removal efficiency, Pb(II), adsorbents, kinetics and isotherm studies