LABILITY OF HEAVY-METAL SPECIES IN AQUATIC HUMIC SUBSTANCES CHARACTERIZED BY ION-EXCHANGE WITH CELLULOSE PHOSPHATE

Labile metal species in aquatic humic substances (HSs) were characteri zed by ion exchange on cellulose phosphate (CellPhos) by applying an o ptimized batch procedure. The HSs investigated were pre-extracted from humic-rich waters by ultrafiltration and a resin XAD 8 procedure. The HS-metal species studied were formed by complexation with Cd(II), Ni( II), Cu(II), Mn(II) and Pb(II) as a function of time and the ratio ion s to HSs. The kinetics and reaction order of this exchange process wer e studied. At the beginning (<3 min), the labile metal fractions are s eparated relatively quickly. After 3 min, the separation of the metal ions proceeds with uniform half-lives of about 12-14 min, revealing ra ther slow first-order kinetics. The metal exchange between HSs and Cel lPhos exhibited the following order of metal lability with the studied HSs: Cu > Pb > Mn > Ni > Cd. The required metal determinations were c arried out by atomic absorption spectrometry.