title: Lability of heavy metal species in aquatic humic substances characterized by ion exchange with cellulose phosphate.
abstract: Labile metal species in aquatic humic substances (HSs) were characterized by ion exchange on cellulose phosphate (CellPhos) by applying an optimized 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 ions to HSs. The kinetics and reaction order of this exchange process were studied. At the beginning (<3 min), the labile metal fractions are separated relatively quickly. After 3 min, the separation of the metal ions proceeds with uniform half-lives of about 12-14 min, revealing rather slow first-order kinetics. The metal exchange between HSs and CellPhos exhibited the following order of metal lability with the studied HSs: Cu > Pb > Mn > Ni > Cd. The required metal determinations were carried out by atomic absorption spectrometry.
authors.affiliation: Analytical Chemistry Department, Institute of Chemistry of Araraquara, UNESP 14800-900, CP 355, Araraquara, SP, Brazil.
authors.forename: J C
authors.initials: JC
authors.lastname: Rocha
authors.forename: I A
authors.initials: IA
authors.lastname: Toscano
authors.forename: P
authors.initials: P
authors.lastname: Burba