PROTON AND METAL COMPLEXATION BY WATER-SOLUBLE LIGANDS EXTRACTED FROM ANAEROBICALLY DIGESTED SEWAGE-SLUDGE

Conditional protonation constants were determined from the formation function computed from the titration data. The common logarithms of the average protonation constants for functional groups titrated between pH 3 and 11 were 4. 2, 7. 2, and 9. 6. Trace metal-WSE complexes were chromatographed on a molecular size exclusion gel. Copper formed the more stable complexes with the ligands in the WSE when compared to Ni or Cd. Cadmium was present predominately as the free metal ion or in inorganic complexes. Adsorption of Cu by montmorillonite was significantly reduced in the presence of the WSE. The primary factor controlling Cu solubility was concluded to be the formation of simulate qualitatively the proton binding of the inorganic ligands whose relative concentrations were previously analytically determined for the WSE. The 'mixture model' ligands were employed to model Cu and Cd speciation for gel filtration and adsorption experiments.