Stability constants of complexes of metal ions with peatsoil humic acids under non-acid-conditions

Abstract

Stability constants of complexes of four divalent metal ions viz. Cu²⁺, Pb²⁺,Mg²⁺ and Cd²⁺  with humic acids (HA) were determined by potentiometric titration of humic acids with the corresponding salt of the divalent metals in aqueous media under non-acid-condition. The log K (logarithm of the stability constant) ranged from 1.0942 to 2.7471 for metal-humic acid complexes were determined using point-wise computational method. The order of stability constants were obtained as follows: Cu >Pb> Cd > Mg for metal -HA complexes respectively, indicating a higher degree of complexation with Cu metal ion.