Influence of humic acid on adsorption of Hg(II) by vermiculite

Autor(es)

do Nascimento, Fernando Henrique ^[1] ; Masini, Jorge Cesar ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Environmental Management; v. 143, p. 1-7, OCT 1 2014.
• Citações Web of Science: 19

Resumo

Geochemical mobility of Hg(II) species is strongly affected by the interactions of these compounds with naturally occurring adsorbents such as humic acids, clay minerals, oxides, etc. Interactions among these sorbents affect their affinity for Hg(II) and a full understanding of these processes is still lacking. The present work describes the influence of a humic acid (HA) sample on the adsorption of Hg(II) by vermiculite (VT). Adsorption isotherms were constructed to evaluate the affinity of Hg(II) by VT, HA, VT modified with humic acid (VT-HA), and VT-HA in presence of soluble humic acid (VT-HA HA). All experiments were made at pH 6.0 +/- 0.1 in 0.02 M NaNO3 and 25.0 +/- 0.5 degrees C for initial Hg(II) concentrations from 1.0 to 100 mu M. Determinations of Hg(II) were made by square wave voltammetry automated by sequential injection analysis, an approach that enables the determination of the free plus labile fractions of Hg(II) in HA suspensions without the need for laborious separation steps. The adsorption isotherms were fitted to Langmuir and Freundlich equations, showing that HA was the material with the higher adsorption capacity (537 +/- 30 mu mol g(-1)) in comparison with VT and VT-HA (44 +/- 3 and 51 +/- 11 mu mol g(-1), respectively). Adsorption order was HA VT-HA HA > VT = VT-HA. At pH 6.0 the interaction of HA with VT is weak and only 14% of C initially added to the suspension was effectively retained by the mineral. Desorption of Hg(II) in acidic medium (0.05 M HCl) was higher in binary (VT-HA) and ternary (VT-HA HA) systems in comparison with that of VT and HA alone, suggesting that interactions between VT and HA are facilitated in acidic medium, weakening the binding to Hg(II). (C) 2014 Elsevier Ltd. All rights reserved. (AU)

• Processo FAPESP: 12/08065-1 - Desenvolvimento e validação de metodologias em fluxo com detecção eletroquímica para aplicação em estudos de interações de Hg(II), As(III) e Se(IV) com ligantes heterogêneos de ocorrência natural
• Beneficiário: Fernando Henrique Do Nascimento
• Modalidade de apoio: Bolsas no Brasil - Doutorado