Please use this identifier to cite or link to this item:
Title: Reduction of mercury(II) by tropical river humic substances (Rio Negro) - Part II. Influence of structural features (molecular size, aromaticity, phenolic groups, organically bound sulfur)
Authors: Rocha, Júlio César
Sargentini, Ézio
Zara, Luiz Fabrício
Rosa, André Henrique
dos Santos, Ademir Bernardo
Burba, Peter
Keywords: Complexation
Mercury (metal)
Molecular Weight
Ph Effects
Ultraviolet Spectroscopy
Volume Fraction
Phenol Derivative
Aqueous Solution
Binding Affinity
Humic Substance
Molecular Size
Molecular Weight
Structure Analysis
Ultraviolet Spectroscopy
Issue Date: 2003
metadata.dc.publisher.journal: Talanta
metadata.dc.relation.ispartof: Volume 61, Número 5, Pags. 699-707
Abstract: The influence of structural features of tropical river humic substances (HS) on their capability to reduce mercury(II) in aqueous solutions was studied. The HS investigated were conventionally isolated from Rio Negro water-Amazonas State/Brazil by means of the collector XAD 8. In addition, the isolated HS were on-line fractionated by tangential-flow multistage ultrafiltration (nominal molecular-weight cut-offs: 100, 50, 30, 10, 5 kDa) and characterized by potentiometry and UV/VIS spectroscopy. The reduction of Hg(II) ions to elemental Hg by size-fractions of Rio Negro HS was assessed by cold-vapor AAS (CVAAS). UV/VIS spectrometry revealed that the fractions of high molecular-size (F1 > 100 kDa and F2: 50-100 kDa) have a higher aromaticity compared to the fractions of small molecular-size (F5: 5-10 kDa, F6: < 5 kDa). In contrast, the potentiometric study showed different concentration of functional groups in the studied HS fractions. The reduction of Hg(II) by aquatic HS fractions at pH 5 proceeded in two steps (I, II) of slow first order kinetics (t1/2 of I: 160 min, t 1/2 of II: 300 min) weakly influenced by the molecular-size, in contrast to the differing degree of Hg(II) reduction (F5 > F 2 > > F1 > F3 > F4 > > F6). Accordingly, Hg(II) ions were preferably reduced by HS molecules having a relatively high ratio of phenolic/carboxylic groups and a small concentration of sulfur. From these results a complex 'competition' between reduction and complexation of mercury(II) by aquatic HS occurring in tropical rivers such as the Rio Negro can be suggested. © 2003 Elsevier B.V. All rights reserved.
metadata.dc.identifier.doi: 10.1016/S0039-9140(03)00351-5
Appears in Collections:Artigos

Files in This Item:
There are no files associated with this item.

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.