EQUILIBRIUM STUDIES OF THE INTERACTIONS OF Zn(II) AND Cu(U) IONS WITH HUMIC ACID BY POTENTIOMETRIC TITRATION, IR AND FLUORESCENCE SPECTROSCOPY

Abstract

The interactions of Zn(II) and Cu(II) with humic acids (HA) were characterized by potentiometric titration, IR and fluorescence spectroscopy. The equilibrium constants determined were Log([Zn(Cat)]/[Zn+2][Cat]) = 15.25, Log([Zn(Cat),]/[ZnCat][Cat]) = 9.80, Log([Zn(Cat)(Sal)]/[Zn(Cat)][Sal]) = 8.59, Log([Zn(Cat)(Pht)]/[Zn(Cat)][Pht]) = 3.71, Log([Zn(OH)(Cat)2][H+]/[Zn(Cat),]) = -8.91, for the Zn(II) system, and Log([Cu(Cat)]/[Cu][Cat]) = 18.45, Log([Cu(Cat)2]l[CuCat][Cat]) = 14.18, and Log([Cu(Cat)(Sal)]/[Cu(Cat)][Sal]) = 8.44 for the Cu(Il) system The amounts of each group detected by potentiometric titration were: phenol = 0.666, carboxylic = 1.042, catechol = 0.540, phtalic = 1.163, and Salicylic= 0.810 mrnoles per gram of HA, and the speciation curves were calculated.