Effects of pH and Temperature on the Interaction of Pb(II) with Azraq Humic Acid Studied with Schubert's Ion Exchange Method
Keywords:humic acid, Schubert's method, lead, stability constant, thermodynamic parameters
The binding of Pb(II) to humic acid extracted from the Azraq Oasis was studied. The influence of temperature and pH was investigated at a constant ionic strength of 0.1. This analysis was done using Schubert's ion-exchange equilibrium method and its modified version. The data showed temperature and pH dependence. The derived conditional stability constants (log βn) for 1:1 and 1:2 lead-humate complexes were determined. It was noticed that the conditional stability constant (log β1) increased with increasing pH and temperature. The derived constants and their temperature dependences were used to calculate the corresponding thermodynamic parameters ΔG, ΔH and ΔS. The results indicate that the stability of these complexes derives from a very favorable entropy increase.
Permanent URL: http://hdl.handle.net/2047/d10006126