Complexation study of humic acids with cadmium (II) and lead (II)

Pinheiro, José Paulo; Mota, A.M.; Gonçalves, Maria Eduarda

doi:10.1016/0003-2670(94)85059-3

Cited by 115 publications

(60 citation statements)

References 14 publications

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“…Despite the differences of experimental conditions and measurement techniques, the log K DEF and Γ values obtained for the Spirulina are of the same order of magnitude reported in the literature [8][9][10][11]16 for other materials. This suggests that these values are governed by the nature of the metal cation and by the chemical nature of the binding sites, which have some similarity between algal materials and humic substances.…”

supporting

confidence: 75%

“…This decrease of log K DEF with the increase of the log θ may be explained by the fact that the sites with stronger affinity by Cu(II) are occupied first, resulting higher log K DEF values. Table 2 presents the values of K D 0 EF for the three materials studied, as well as the heterogeneity parameters, which were between 0.4 and 0.5, denoting an elevated degree of heterogeneity [8][9][10][11]16 for both, the cell surfaces and the soluble complexants. As mentioned before, this heterogeneity is due to the presence of amine, phenolic, phosphate and carboxylic groups in the studied materials.…”

Section: The Differential Equilibrium Functionsmentioning

confidence: 99%

“…Usually, these studies report results for natural organic matter in waters (humic substances), and using anodic stripping voltammetry (ASV) for measurement of the labile fraction of the metal cation. [8][9][10]16 Rollemberg et al…”

Section: The Differential Equilibrium Functionsmentioning

confidence: 99%

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Evaluating Scatchard and Differential Equilibrium Functions to study the binding properties of Cu(II) to the surface of mixed species of lyophilized Spirulina (Cyanobacteria)

Parmeggiani

Masini

2003

J. Braz. Chem. Soc.

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A ligação de Cu(II) à superfície de espécies mistas da microalga Spirulina foi estudada em pH 6.0 por titulação potenciométrica monitorada com eletrodo íon-seletivo para Cu(II). Três materiais foram estudados: a suspensão completa da alga, a água de lavagem obtida por centrifugação da suspensão completa e a suspensão composta por células lavadas com água. Os métodos de Scatchard e de Funções Diferenciais de Equilíbrio (DEF) foram usados para tratamento dos dados de titulação. Os gráficos de Scatchard possibilitaram a determinação de duas classes de sítios de complexação, sendo que os valores de log K' para os sítios mais fortes variaram entre 7,3 e 7,9. Para os sítios mais fracos os valores de log K' foram determinados entre 3,5 e 3,9. As concentrações totais dos sítios de complexação foram 1,6±0,1; 1,5±0,5 e 0,92±0,08 mmol g -1 para a suspensão total, água de lavagem e células lavadas, respectivamente. O método DEF revelou uma variação linear dos valores de log K DEF em função do log θ (θ = grau de ocupação dos sítios de complexação), sendo que os valores de log K DEF decresceram de 9 para 4 em conseqüência do aumento de log θ de -2,5 para -0,25. Os graus de heterogeneidade determinados por DEF ficaram na faixa entre 0,4 e 0,5 para os três materiais estudados.The binding of Cu(II) to the surface of mixed species of Spirulina was studied at pH 6.0 by potentiometric titration monitored with a copper ion selective electrode. Three materials were studied: the total suspension of alga, the washing water that resulted from centrifugation of the total suspension, and the water-washed cells. The Scatchard method and the Differential Equilibrium Functions (DEF) were used for the treatment of the titration data. The Scatchard plots determined two classes of binding sites, with log K' values for stronger sites varying between 7.3 and 7.9. For the weaker sites the log K' values ranged between 3.5 and 3.9. The total concentration of binding sites were 1.6±0.1, 1.5±0.5 and 0.92±0.08 mmol g -1 for the total suspension, washing water, and washed cells, respectively. The DEF approach revealed a linear variation of log K DEF as a function of log θ (θ = degree of site occupation), with log K DEF decreasing from 9 to 4 as a consequence of increasing log θ from -2.5 to -0.25. The degree of site heterogeneity determined by the DEF approach was between 0.4 and 0.5 for the three materials studied.

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supporting

confidence: 75%

Section: The Differential Equilibrium Functionsmentioning

confidence: 99%

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Evaluating Scatchard and Differential Equilibrium Functions to study the binding properties of Cu(II) to the surface of mixed species of lyophilized Spirulina (Cyanobacteria)

Parmeggiani

Masini

2003

J. Braz. Chem. Soc.

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“…Cu and Pb have higher affinity for DOM and therefore a very small fraction of these metals exists as free hydrated metal ions in soil solution (Aualiitia and Pickering, 1986;Sauvé et al, 1998;Weng et al, 2001b). On the other hand, metals such as Cd, Ni and Zn are less prone to form such stable metal-organic complexes (Aualiitia and Pickering, 1986;Pinheiro et al, 1994;Holm et al, 1995). Thus, a larger fraction of these metals is recovered as free hydrated metal ions.…”

Section: Tablementioning

confidence: 99%

Effects of rice straw on the speciation of cadmium (Cd) and copper (Cu) in soils

Cui

Weng

et al. 2008

Geoderma

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“…39 In cases of quenching of the fluorescence signals is possible to determine the conditional stability constant (K C ) of AHS-metal complex using the Stern-Volmer model. [40][41][42][43] The K C provides information as to whether or not favoring the formation of AHS-metal complex, where higher values indicate K C favoring the complexation of metals in AHS. The Stern-Volmer model allows the calculation of K C from experiments where the metals are being gradually added to the AHS and the fluorescence signal is begin followed after each addition.…”

mentioning

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.

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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% ...

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Complexation study of humic acids with cadmium (II) and lead (II)

Cited by 115 publications

References 14 publications

Evaluating Scatchard and Differential Equilibrium Functions to study the binding properties of Cu(II) to the surface of mixed species of lyophilized Spirulina (Cyanobacteria)

Evaluating Scatchard and Differential Equilibrium Functions to study the binding properties of Cu(II) to the surface of mixed species of lyophilized Spirulina (Cyanobacteria)

Effects of rice straw on the speciation of cadmium (Cd) and copper (Cu) in soils

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

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