The metal complexing capacity and the nature of the chelating ligands of organic matter extracted from broiler house litter were studied by ion-exchange equilibrium and dissolution methods and infrared spectroscopy.
The water extract of broiler house litter appeared to exhibit a significant chelating effect on the cations Cu2+, Zn2+, Mg2+, and Al3+. The amount of organic matter complexed by one mole of metal and the stability of metal complexes increased with increasing pH in the cases of Cu-, Mg-, and Al-complexes, but were unaffected by changes in pH in the case of Zn-complexes. With respect to the divalent ions, the amount of organic matter chelated and the stability of the divalent metal-complexes decreased in the order Cu > Zn > Mg.
Dissolution studies with insoluble Al2O3 and Fe2O3 powders showed that both Al and Fe were chelated in the aqueous extract, but 10 times more Al than Fe was dissolved in a given time period.
Infrared analysis revealed spectrograms of the ligands similar to those obtained for polysaccharides. However, since the freeze-dried extract contained 9% N, some NH2 groups must have been present, although bands of these groups were not resolved from overlapping O-H bands. Functional group frequency vibration comparisons at 3,500, 3,200, 1,650, and 1,400 cm-1 showed that the formation of stable metal-complexes involved carboxyl electrovalent linkages and probably hydroxyl and/or amino coordinate linkages.