Abstract
Humic acid with hydroxyl-, phenoxyl-, and carboxyl-reactive groups can form coordination compounds with metals. The ion-exchange equilibrium method using Dowex AG 50W-X8, 20-25 mesh Na+ form was used to determine stability constants of complexes formed between humic acid (isolated from the soil) 50–250 μg (≈3×10−5–15×10−5 mol/liter) and metal salts solution 200 μg at pH 3.5. The stability constant (log K) for different metal–humic acid complexes indicated the following order of the stabilities of complexes formed between humic acid and metal ions: Cu>Fe>Pb>Ni>Co>Ca>Cd>Zn>Mn>Mg. The data on stability constants demonstrated substantial deviation from Irwing–Williams series reported for divalent ions. The molar humic acid/metal ratios were also calculated. Some of the factors affecting the stability constants such as cation exchange capacity of humus soil, molecular radius, and molecular surface area of humic molecules were also estimated. The significance of the data to predict the behavior of these complexes in the environment is discussed.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
