Pigeon peas hulls waste as potential adsorbent for removal of Pb(II) and Ni(II) from water

In this study, pigeon peas hulls powder, a low-cost agricultural by-product, was used as adsorbent for the removal of Pb(II) and Ni(II) ions from aqueous solutions. The adsorbent was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption characteristics were explored using well-established and effective parameters including the effect of pH, contact time, adsorbent dosage, initial metal ion concentration and temperature. Optimum adsorption of Pb(II) and Ni(II) was observed at pH 4.0. Kinetic studies revealed that the adsorption data fit well to pseudo-second-order model with high correlation coefficient. Langmuir model gives a better fit than the Freundlich and Dubinin-Radushkevich models. Thermodynamic properties, i.e., Delta G degrees, Delta H degrees, and Delta S degrees showed that adsorption of Pb(II) and Ni(II) onto PPH was endothermic, spontaneous and feasible in the temperature range of 293-313 K. The PPH powder can be used as an effective, low cost, and eco-friendly green adsorbent for the removal of selected metal ions from aqueous solution. (C) 2012 Elsevier B.V. All rights reserved.