ADSORPTION OF LEAD (II) ION and CADMIUM (II) ION USING BANANA Musa acuminata AND MORINGA Oleifera LEAVES

Abstract

Adsorption has been investigated as an effective technique for the treatment of waste water containing heavy metals, resulting from humans and industrial activities. The hazardous and adverse effects caused by heavy metals present in waste waters which are released onto the environment from different industrial wastes are of significant environmental concern, and adsorption techniques have been investigated as an effective method for their removal. Banana and moringa leaves were collected from a farm located around Oluokun village, Ido Local Government Area of Ibadan, Oyo State. They were washed, dried and pulverized, then used without further modification, as biosorbents for the uptake of lead (II) and cadmium (II) ions from aqueous solutions. Adsorption experiments was carried out as a function of contact time (5, 15, 30, 60, 90, 120, 180, 240, 300 and 360 minutes), solution pH (2–8), (from initial concentration of 100mg/L of the metal ions) and initial concentration (50, 100, 200, 300 and 400 mg/L). The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models, while Pseudo 1st order, 2nd order and Elovich models were used to study the kinetics of the adsorption process. Thermodynamics parameters was analyzed using the equation ΔGo = ΔHo - TΔSo. The results obtained showed that adsorption capacity (qe) of both ions increases with increase in contact time and initial metal ions concentration. Optimum uptake of Cd(II) and Pb(II) ions onto banana leaves was achieved in acidic medium (pH 2- 4), and at neutral pH onto moringa leaves. The Langmuir monolayer adsorption capacity qmax of 54.95 mg/g, and 125 mg/g was obtained for Cd (II) ions on the biomass and 11.95 mg/g and 58.82 mg/g for lead ions on both banana and moringa leaves respectively, and all the 1/n values obtained from the Freundlich model were below one, showing that adsorption of Cd(II) and Pb(II) ions was favourable. The kinetics study revealed that the adsorption of metal ions was second order. The adsorption of Cd(II) and Pb(II) ions onto banana leaves increases with contact time. The adsorption of cadmium (II) ions onto moringa attained maximum at 5 minutes, while it takes 90 minutes for banana to achieve maximum uptake of the metal ion. Banana leaves had maximum uptake of lead (II) ions at 15 minutes, and it took 90 minutes for moringa to attain optimum sorption of the metal ion at the condition of study. The thermodynamics studies of the adsorption process reflected that the reaction is endothermic, spontaneous, with high entropy. The results of the study showed that banana and moringa can serve as good substitute for activated carbon, as potential adsorbents for the removal of metal ions and other pollutants from the water bodies. Keywords: Adsorption, Adsorbents, Langmuir, Freundlich, Temkin, Elovich, Pseudo 1st and 2nd order isotherms, banana leaves (BL), Moringa leaves (ML).