Molybdenum (VI) binded to humic and nitrohumic acid models in aqueous solutions: phthalic, 3- and 4-nitrophthalic acids, catechol and 4-nitrocathecol, part 1

Mercê, Ana Lúcia Ramalho; Greboge, Cristiane; Mendes, Giovani; Mangrich, Antônio S.

doi:10.1590/s0103-50532005000100006

Cited by 11 publications

(7 citation statements)

References 29 publications

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“…[3][4][5] Soil organic matter (OM) promotes soil aggregation and its chemical function is recognized by its ability to interact with metals, oxides, metal hydroxides and mineral clays to form organometallic complexes. Soil OM improves N, P, and S bioavailability, therefore it has the potential use as a slow release fertilizer.…”

Section: Moo 3 + H-bonding Ligandmentioning

confidence: 99%

“…Also the complexation of metals by heterogeneous ligands is dependent on metal loading (the rate of bound metal to the binding site concentration). To overcome some of these difficulties this study deals with some molecular models of HAs according to the sorption sites following others in the literature 5,[26][27][28] presenting data on those HAs main sorption sites that can reliably be used in those mathematical models as well as the speciation along a wide range of pH values.…”

Section: Moo 3 + H-bonding Ligandmentioning

confidence: 99%

“…5,30 Aware of the region where the uptaking of protons by molybdate is seen, only when MoO 2 2+ cations were present the calculations began. This initial portion of the pH profiles produced no complexed species rather than polyanions, under the experimental conditions employed.…”

Section: +mentioning

confidence: 99%

“…This initial portion of the pH profiles produced no complexed species rather than polyanions, under the experimental conditions employed. The mathematical model for the calculations took into account the possible rates of bound metal to the binding site concentration (the metal loading parameter) 5 in order to simulate an heterogeneous ligand such as humic and nitrohumic substances, the hydrolysis constants of molybdenum ions 31,32 and the standardized concentrations of KOH -the titrant employed -and the concentration of the mineral acid (HNO 3 ) added when necessary.…”

Section: +mentioning

confidence: 99%

“…5 Nonetheless, the nitrohumic substances, laboratory artifacts, presented as an alternative fertilizer by providing more N content when the mineralization of the soil occur, can also bind differently to metal ions when compared to non nitro organic matter in a wider range of pH values.…”

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confidence: 99%

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Molybdenum (VI) binded to humic and nitrohumic acid models in aqueous solutions. Salicylic, 3-nitrosalicylic, 5-nitrosalicylic and 3,5 dinitrosalicylic acids: part 2

Lúcia¹,

Mercè²,

Mangrich³

et al. 2006

J. Braz. Chem. Soc.

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Apresentam-se neste trabalho, estudos eletroquímicos e espectroscópicos na região do Ultravioleta-Visível de modelos derivados do ácido salicílico de ácidos húmicos e nitrohúmicos, esse último um artefato laboratorial, na presença de molibdênio para determinar a afinidade desses modelos com esse íon metálico. Molibdênio tem um papel importante na química de solo e conjuntamente com as substâncias húmicas, promove fertilidade ao solo e água e é um elemento chave na enzima nitrogenase. Os resultados obtidos mostraram que pelo menos uma espécie complexada está presente na faixa de pH 6,3 a 8,0, mesmo para o modelo menos básico escolhido, dos ácidos nitrossalicílicos. Estudo anterior mostrou que modelos derivados do ácido ftálico e nitroftálico, modelos também para os ácidos húmicos e nitrohúmicos, apresentaram espécies complexadas apenas até pH 6,5. As constantes de formação calculadas mostraram que a substituição do grupamento nitro na posição orto desfavorece a complexação, quando comparada à substitução para, devido provavelmente ao impedimento estérico no primeiro caso, uma vez que esse impedimento se manifesta indubitavelmente no composto duplamente substituído com o grupamento nitro. Os espectros obtidos por voltametria cíclica e por espectroscopia no Ultravioleta-Visível mostraram que a química do molibdênio em solução aquosa é muito complexa com a variação do pH, e que o ânion molibdato deixa de ser um ânion em valores de pH próximos a 4, quando então passa a se comportar como cátion, MoO 2 2+ (M).In this work electrochemical and Ultraviolet-Visible studies were performed in solutions of salicylic acid models of humic and nitrohumic acids, a laboratory artifact, and molybdenum in order to determine the affinity of these models towards the metal ion. Molybdenum, which plays a very important role in the soil chemistry, and together with humic substances, impart fertility to soil and water and is a key element in the activity of nitrogenase. The obtained results showed that at least one complexed species is present at the pH range of 6.3 to 8.0, even for the less basic chosen models, the nitrosalicylic acids. Previous study showed that phthalic and nitrophthalic, also humic and nitrohumic acids model compounds, presented complexed species with molybdenum only till pH 6.5. The calculated formation constants showed that the substitution of the nitro group in the orto position was less favoured than in the para substitution, probably due to a steric hindrance in the former, which was clearly seen in the double substituted salicylic nitro derivative. The cyclic voltammetry as well as the Ultraviolet-Visible obtained spectra were able to show that the chemistry of molybdenum in aqueous solutions as the pH is increased is very complex, and the molybdate stops acting as an anion only after pH around 4, when it finally becomes a cation MoO 2 2+ (M).

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Section: Moo 3 + H-bonding Ligandmentioning

confidence: 99%