Removal Of Some Heavy Metals From Aqueous Solutions:Potentiometric And Thermodynamic Studies Of Vanillin And ItsMetal ComplexesAuthor(s): 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 MÂKCl and 10 vol.% ethanolÂwater 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 (ïG, ïH and ïS) 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.