Labile/inert metal species in aquatic humic substances: an ion-exchange study

An ion-exchange procedure has been developed for the analytical fractionation of metals (e.g. Al, Co, Cu, Fe, Mn, Ni, Pb, Zn) forming labile/inert complexes with aquatic humic substances (HS) isolated (XAD 2, XAD 8, ultrafiltration) from bog, forest, ground and lake water. Using 1-(2-hydroxyphenylazo)-2-naphthol groups immobilized on cellulose (Cellulose HYPHANTM) as chelating collector (batch and column procedure, resp.) for reactive metal fractions in dissolved HS, the kinetics and the degree of separation (referred to the total metal content) serve for the operational characterization of the metal lability. According to the separation kinetics (96 h), mostly the reactivity order Mn > Zn > Co > Pb > Ni > Cu >> Al > Fe is observed for the above metals in HS, resulting in recoveries of > 98% for Mn and Zn, but strongly varying for the other metals (e.g., 44-95% Cu, 18-84% Fe). (orig.)