The Investigation of the heavy metal adsorption kinetics and equilibrium on different plants waste

VI SUMMARY Increasing industrial activities have given rise to the question of depollution of waste waters, particularly where heavy metal ions are concerned. Several methods such as chemical precipitation, ion exchange, filtration and adsorption have been used to remove metal ions from solution, but they are all generally expensive. Adsorption is one of the effective methods widely used. However, the cost is an important parameter in adsorption. Hence, the usage of less expensive indigenous biodegradable resources for processing hazardous waste would be promising in emerging of environmental biotechnology. The study involves an investigation of effects of very low cost adsorbents such as shells of hazelnut and almond, sawdust of walnut and poplar as well as their modified species on the removal of metal ions such as Ni(II), Cd(II) and Pb(II) from aqueous solution. Certain amount of raw and modified adsorbents were mixed with metal ion solution whose initial concentration is known and thus corresponding kinetics and equilibrium times were determined by measuring decrease in equilibrium concentration of metal ions against time. Kinetics fit pseudo- first and second order models and hence adsorption rate constants were calculated. A series of solutions with different metal ion concentration was mixed with constant amount of raw and modified adsorbents and shaked at there different temperatures for the period of equilibrium time determined preously, and thus equilibrium concentrations were determined by analysing the amounts of metal ion remained in solution. Adsorption isotherms were obtained by plotting equilibrium concentration versus metal ion concentration adsorbed on the unit amount of adsorbant. Isotherm data followed Freundlich and Langmuir equations and corresponding isotherm constants were calculated. Thermodynamic parameters AG, AH and AS were also calculated from K", adsorption equilibrium constant, obtained at different temperatures, for each adsorbent and metal ion. In addition the adsorption competition of Ni(II), Cd(II) and Pb(H)ions were determined from A% values obtained from double and triple mixtures of these ions.