The indiscriminate discharge of Cu and Pb ions to the environment is a major concern in most industrial cities of the world. The adsorptive removal of Cu (II) and Pb (II) from aqueous solution from industrial effluents using melon shell, an agricultural waste, modified with 10% phosphoric acid was investigated. The residual metal ion concentration was determined using Atomic Absorption Spectroscopic, AAS. Batch mode experiments were conducted to study the effects of concentration, pH, contact time and temperature on Cu (II) and Pb (II) adsorption. The adsorbent was characterized by FTIR spectroscopy. The study revealed that the adsorption efficiency of activated melon shell was dependent on the pH of Cu (II) and Pb (II) solution, with pH 8 being optimal. The contact time for the adsorption was found to be at 80 minutes for both metals. Adsorption of Cu (II) and Pb (II) on the activated melon was found to increase with increase in concentration, with removal efficiency of 98.8% and 83.9% for 26mg/l. Equilibrium adsorption isotherm, kinetic and thermodynamic studies were investigated. The experimental data were analyzed by the Langmuir and Freundlich models and the isotherm data fitted well to the Langmuir isotherm with of 0.985 and 0.727 and monolayer adsorption capacity of 0.034mg/g and 0.180mg/g for Cu (II) and Pb (II) respectively. The kinetic date obtained at different contact time was analyzed using pseudo first order and pseudo second order equation. The experimental data for both Cu (II) and Pb (II) fitted very well for pseudo second order kinetic model. The adsorption process was thermodynamic feasible and spontaneous as G values were negative (-2.7353Kj/mol for Pb and -6.8877KJ/mol for Cu). The negative and positive values of H (-2.6089KJ/mol and +16.6446KJ/mol) showed that adsorption process was exothermic and endothermic for Cu (II) and Pb (II) respectively. This study revealed that activated melon shell is a viable agricultural waste for the removal of Cu (II) and Pb (II) ions from aqueous solution.
Keywords: Contact time, Melon Shell, absorption, aqueous solution, spontaneous
