Sorption of lead ions from aqueous solution by chickpea leaves, stems and fruit peelings

Leaves, stems and fruit peelings of chickpea (Cicer arientinum L.) were successfully utilized for the accumulation of lead ions from aqueous solutions onto their surfaces. The rate and extent of accumulation were affected by pH, particle size, contact time and the initial concentration of Pb(II) ions, respectively. The sorption capacities of leaves, stems and fruit peelings towards Pb(II) ions were found to be 81.30, 80.10 and 53.26%, respectively, at an initial Pb(II) ion concentration of 200 mg/dm³, optimum pH conditions of 6.0, a particle size of 0.354 mm and a contact time of 120 min. Most of the sorption occurred within the first 15 min and attained a maximum value after 120 min. The Bangham equation was used to express the adsorption mechanism. The adsorption rates of Pb(II) ions were found to decrease in the order: leaves > stems > fruit peelings. Possible cell-metal ion interactions may be due to the involvement of -COOH, -OH and -NH groups in the sorption process. The obtained sorption data were well fitted by the Freundlich and Langmuir adsorption isotherms, respectively. The results showed that chickpea leaves and stems behave as good adsorbents for the removal of Pb(II) ions from aqueous solution.