Removal of toxic metal ions from natural and waste waters is of greatimportance for the health of living organisms and for environmentalprotection. Alternatively to the conventional chemical treatments, such asprecipitation, reverse osmosis, etc, biosorption shows a growing interest fortoxic metal ions removal from contaminated aqueous solutions.The sorption ability of every type of biomass towards metal ions depends onmany variables that characterize the solution. Among these, the ionicstrength (I) is one of the most important and cannot be neglected during anaccurate adsorption study.For this reason and with the aim of quantitatively define the influence of I,here are reported the results of kinetic and thermodynamic studies on thesorption capacity of Hazelnut (HS) and Almond (AS) shells toward Pb(II)and Cd(II) in NaCl aqueous solution in a wide I range (0.05 <I (mol L-1) <0.5) at room temperature. The formation of chloride complexes have beenalways considered. To avoid the hydrolysis of the metal ions the pH valueof solutions was kept at 5. HS and AS have been grinded, washed andsieved before using. The materials were characterized by FT-IR and SEMEDXanalysis. The FT-IR spectra showed the presence of numerous Odonorsites indicating that sorption process occurs by chemical interactionof metal ions with these binding groups.The residual metal concentration in aqueous solutions during the kinetic andequilibrium experiments was measured by Differential Pulse AnodicStripping Voltammetry (DP-ASV).Several kinetic and isotherm equations were used to fit the experimentaldata. The pseudo second order equation was the best in terms of fit for allthe systems investigated. Although all the isotherm models fitted properlythe equilibrium data, the Langmuir model was the best one for the Pb(II)-HS/AS systems, whereas Sips model showed the best results for the Cd(II)-HS/AS systems.
|Numero di pagine||0|
|Stato di pubblicazione||Published - 2016|