Adsorption of Heavy Metals
KINETIC STUDY OF LIQUID-PHASE ADSORPTIVE REMOVAL OF HEAVY METAL IONS BY ALMOND TREE (TERMINALIA CATAPPA L.) LEAVES WASTE
ABSTRACT. The kinetic sorption of five metal ions - Al3+, Cr6*, Zn2+, Ag+ and Mn2+ - from aqueous solution onto almond tree leaves (ATL) waste in single component system has been studied. The experimental data was analyzed in terms of intraparticle diffusion and rate of adsorption, thus comparing transport mechanism and chemical sorption processes. The sorption rates based on the pseudo-second order rate constants for the five metal ions are 0.018 (Al3+), 0.016 (Cr6+), 0.023 (Zn2+), 0.021 (Ag+) and 0.022 (Mn2+) g/mg.min. The adsorption rates are rapid and within 180 min of agitation more than 85 percent of these metal ions has been removed from solution by the ATL waste biomass. The kinetic data suggest that the overall adsorption process is endothermic, and that the rate-limiting step is a surface diffusion controlled process. The results from this study have revealed that the ATL waste, which is hitherto an environmental nuisance, has the ability to adsorb metal ions from solution and the data are relevant for optimal design of wastewater treatment plants. The low cost and easy availability of ATL waste make potential industrial application a strong possibility.
KEY WORDS: Kinetic sorption, Heavy metal ions, Almond tree leaves waste, Wastewater treatment plants
INTRODUCTION
Adsorption kinetic studies are important in predicting the rate of pollutant removal from aqueous systems. Kinetic studies provide information for selecting optimum operating conditions, identifying reaction pathways, understanding rate-limiting steps and are also essential for scaling-up of laboratory studies to industrial applications. The use of cheap adsorbents for the treatment of aqueous effluents to remove inorganic and organic pollutants has been recognized as a major development in the area of biosorption during the past ten years [1-10]. Some of the
ABSTRACT. The kinetic sorption of five metal ions - Al3+, Cr6*, Zn2+, Ag+ and Mn2+ - from aqueous solution onto almond tree leaves (ATL) waste in single component system has been studied. The experimental data was analyzed in terms of intraparticle diffusion and rate of adsorption, thus comparing transport mechanism and chemical sorption processes. The sorption rates based on the pseudo-second order rate constants for the five metal ions are 0.018 (Al3+), 0.016 (Cr6+), 0.023 (Zn2+), 0.021 (Ag+) and 0.022 (Mn2+) g/mg.min. The adsorption rates are rapid and within 180 min of agitation more than 85 percent of these metal ions has been removed from solution by the ATL waste biomass. The kinetic data suggest that the overall adsorption process is endothermic, and that the rate-limiting step is a surface diffusion controlled process. The results from this study have revealed that the ATL waste, which is hitherto an environmental nuisance, has the ability to adsorb metal ions from solution and the data are relevant for optimal design of wastewater treatment plants. The low cost and easy availability of ATL waste make potential industrial application a strong possibility.
KEY WORDS: Kinetic sorption, Heavy metal ions, Almond tree leaves waste, Wastewater treatment plants
INTRODUCTION
Adsorption kinetic studies are important in predicting the rate of pollutant removal from aqueous systems. Kinetic studies provide information for selecting optimum operating conditions, identifying reaction pathways, understanding rate-limiting steps and are also essential for scaling-up of laboratory studies to industrial applications. The use of cheap adsorbents for the treatment of aqueous effluents to remove inorganic and organic pollutants has been recognized as a major development in the area of biosorption during the past ten years [1-10]. Some of the
References: 1. El-Geundi, M.S. Wat. Res. 1991, 24, 271. 2 3. Ho, Y.S.; McKay, G.; Wase, D.A.J.; Forster, C.F. Adsorpt. Sci. Technol. 2000, 18, 639. 4 5. Horsfall Jr., M.; Abia, A.A. Wat. Res. 2003, 37, 4913. 6 7. Horsfall Jr., M.; Ogban, F.; Akporhonor, E.E. Chem. Biodiv. 2005, 2, 1246. 8 11. Okiemen, F.E.; Okundia, E.U.; Ogbeifun, D.E. J. Chem. Technol. Biotechnol. 1991, 51, 97. 12 13. Ho, Y.S.; McKay, G. Wat. Res. 2000, 34, 735. 14 15. Tan, W.T.; Khan, R.M. Environ. Technol. Let. 1988, 9, 1223. 16