Document Type : Original Article
Chemistry Department, Faculty of Science, Mansoura University, Mansoura 35516, Egypt
In the present study three biosorbents are prepared from orange peel bio-wastes. These are the raw orange peel (RR), the sodium hydroxide modified orange peel (RN) and the sulfuric acid modified orange peel (RS). The prepared biosorbents are characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), point of zero charge. Batch adsorption method is applied to determine the optimum operational parameters for lead ion removal from aqueous solutions such as pH, initial concentration of metal ion, contact time and adsorbent dosage. Kinetic models have been applied to test the experimental data to determine the mechanism of adsorption and its potential rate-controlling step. The obtained kinetics data revealed that the adsorption process of lead ion is more fitted to pseudo-second order than pseudo-first order. Equilibrium data showed that adsorption of lead ions fitted well with Langmuir equilibrium isotherm model. Thermodynamic parameters ΔG°, ΔH° and ΔS° parameters have been investigated. The negative values of ΔG° of all biosorbents explain the spontaneous behavior of adsorption process. The negative values of ΔH° can explain the exothermic behavior of (RR, RN), while positive value of ΔH° can explain the endothermic behavior of (RS). The prepared orange peel derived biosorbents were successfully applied for removal of lead ion from different water samples.