A kinetic study of the interaction of hydrous aluminum oxide colloids with a well-characterized soil fulvic acid

Abstract

Models of the species arising from the interaction of hydrous aluminum oxide colloids with humic substances have been prepared by neutralizing Al(III) stock solutions in the presence of a well-characterized fulvic acid and aging for 24 h. These samples have been examined kinetically using the fluorimetric Al(III) reagent calcein blue. The rates of formation of Al(III) calcein blue complexes allows recognition of five kinetically distinguishable components in the mixtures. Some are similar in lability to simple organic chelates of Al(III). Others are much less labile. Evidence for non-labile colloidal "ternary" complexes of Al(III) ion species complexed to fulvic acid, and bound to hydrous aluminum oxide colloid is presented. The polydisperse mixture character of fulvic acid is seen in patterns of complex lability much as it is seen in patterns of complex stability.