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Removal Of Some Heavy Metals From Aqueous Solutions:Potentiometric And Thermodynamic Studies Of Vanillin And ItsMetal Complexes

A.S.Al-Shihri,A.A.El-Bindary, A.M.AL-Sharhani

Proton-ligand dissociation constant of 3-methoxy-4-hydroxybenzaldehyde (Vanillin) and metal-ligand stability constants of its complexes with (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) metal ions have been determined potentiometrically in 0.1 M–KCl and 10 vol.% ethanol–water mixture. The stability constants of the formed complexes increases in the order Mn2+, Co2+, Ni2+, Zn2+ and Cu2+. The effect of temperature was studied and the corresponding thermodynamic parameters (G, H and S) were derived and discussed. The dissociation process is nonspontaneous, endothermic and entropically unfavourable. The fotmation of the metal complexes has been found to be spontaneous, endothermic and entropically favourable.