Redução de crômio hexavalente por substâncias húmicas aquáticas imobilizadas em aminopropil sílica

Romão, Luciane Pimenta Cruz; Araújo, Adriana Barbosa; Rosa, André Henrique; Rocha, Júlio César

doi:10.1590/s0100-46702002000200031

Cited by 2 publications

(1 citation statement)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the first case AHS could reduce Cr(VI) to Cr(III) form and subsequently complex the reduced form. Romão et al 50 demonstrated that AHS can reduce Cr(VI) in acid pH (2.5), being that this behavior was not observed for pH 6.0. Probably this mechanism can be disregarded for this work.…”

Section: Fluorescence Spectramentioning

confidence: 99%

Solar radiation effect on the complexation capacity of aquatic humic substances with metals

Melo

Toffoli

Moreira

et al. 2012

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

Este estudo teve como principal objetivo avaliar o efeito da radiação solar sobre a capacidade de complexação das substâncias húmicas aquáticas (AHS) com as espécies metálicas Al 3+ , Cr 3+ , CrO 42-e Ni 2+ . Microcosmos foram montados com AHS extraídas do Rio Preto com concentração de 5,0 mg L -1 de carbono orgânico dissolvido e diferentes concentrações de metais, sendo expostos à radiação solar in situ. As constantes de estabilidade condicional foram de 2,0 × 10 -2 , 1,1 × 10 -5 e 2,6 × 10 -2 para os complexos AHS-Cr 3+ , AHS-Ni 2+ e AHS-CrO 4 2-, respectivamente. Os resultados mostraram que a radiação solar foi responsável por um decréscimo na capacidade de complexação de 15-26% para AHS-Al 3+ , 15-72% para AHS-Cr 3+ , 12-18% para AHS-CrO 4 2-e de 13-42% para AHS-Ni 2+ . Conclui-se que a radiação solar altera a disponibilidade de metais previamente complexados às AHS, tornando-os disponíveis no corpo aquático.This study had as main objective to assess the effect of solar radiation on the capacity of the aquatic humic substances (AHS) to complex Al 3+ , Cr 3+ , CrO 4 2-and Ni 2+ . Microcosms were prepared with AHS from Preto River containing 5.0 mg L -1 of dissolved organic carbon and different concentrations of metal species, being exposed to solar radiation, in situ. Conditional stability constants obtained for the AHS-Cr 3+ , AHS-Ni 2+ and AHS-CrO 4 2-complexes were 2.0 × 10 -2 , 1.1 × 10 -5 and 2.6 × 10 -2 , respectively. The results showed that solar radiation is responsible for decreasing capacity complexation in 15-26% for AHS-Al 3+ , 15-72% for AHS-Cr 3+ , 12-18% for AHS-CrO 4 2-and 13-42% for AHS-Ni 2+ . We can conclude that solar radiation alters metals' availability previously complexed to AHS, making them available in the aquatic body.Keywords: aquatic humic substances, metal complexation, solar radiation, fluorescence IntroductionAquatic humic substances (AHS) have been intensively studied because they play an essential role in biogeochemical processes. 1,2 They can participate in the complexation reactions with metal ions thereby influencing the transport and availability of them in the environment, 2-4 may suffer interactions with organic compounds and thus, reduce or increase its toxicity to the biota, 4,5 can act in redox 6 and photochemical reactions. 7 Aquatic HS are products of the decomposition of vegetal and animal remains from microbiological transformations. They are normally dark colored organic macromolecules with a high molecular weight, a complex structure consisting of aromatic and aliphatic compounds, which have a large number of functional groups containing oxygen, e.g., carboxylates (-COOH), phenolics (aromatics-OH), alcoholics (-OH), quinones (aromatics=O), among others. 1,2 Depending on the water solubility, AHS can be operationally separated into three fractions: fulvic acids that are soluble in all pH range, humic acids that are soluble in alkaline pH and insoluble in acid pH, and humin that is insoluble in all pH range. It is worth noting that the AHS comprise about 40-60% ...

show abstract

Section: Fluorescence Spectramentioning

confidence: 99%