STUDIES OF THE PROTONATION AND METAL ION COMPLEXATION EQUILIBRIA OF NATURAL ORGANIC ACIDS: FULVIC ACIDS

The complicating factors present in the proton and metal ion complexation equilibria with Armadale Horizons Bh Fulvic Acid and Suwannee River Fulvic Acid have been described via the use of a unified physicochemical approach. By use of a Donnan potential and Marcus electroneutral cell based-model, it has been possible to characterise the above-mentioned fulvic acid molecules as heterogeneous charged and hydrophobic, ie. impermeable to bulk electrolyte.; From nonaqueous titrations and protonation enhancement titrations in the presence of Eu(III) and Cu(II), four different acidic functionalities with varying dissociation constants and abundances have been proposed for each fulvic acid molecule.; Using the proposed acidic functionalities, the binding of metal ions eg. Cu(II), Co(II), Zn(II), and Eu(III), to the fulvic acid molecules has been adequately described thus substantiating the validity of the model.