Portal de Periódicos da CAPES

Artigo Produção Nacional Revisado por pares

BIBTEX RIS

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)

2003; Elsevier BV; Volume: 61; Issue: 5 Linguagem: Inglês

10.1016/s0039-9140(03)00351-5

1873-3573

Joana Rocha,

Mercury impact and mitigation studies

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: F2>>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.