Polyphenol Interactions with Aluminium(III) and Iron(III): their Possible Involvement int he Podzolization Process

Abstract

The stability and solubility of complexes formed between AlIII , FeIII and an epicatechin dimer (B2) and an epicatechin polymer or tannin (T) have been studied. Polyphenols such as these could be active in mobilizing iron and aluminium in organic soils; they have the potential to act as bis-catecholate ligands toward these metal ions at neutral pH. However, it is established that the dimer functions only as a mono- catecholate , and its pH dependent stability constants (for aluminium) are no greater than those of catechol . Aqueous solutions of the ligands do not solubilize amorphous Fe(OH)3 significantly under aerobic conditions and the complexes of T are insoluble except at very low metal (Al, Fe) : donor site ratios. These observations are discussed in relation to the soil-forming process of podzolization.