Coeficientes de difusão de metais em materiais não convencionais (agarose e acetato de celulose) usados na técnica de difusão em filmes finos por gradientes de concentração

The DGT technique allows one to measure quantitatively free and labile metal species in aquatic systems. Nevertheless, for this approach, knowledge is required of the diffusion coefficients of the analytes in a diffusive layer. In this study, the diffusion coefficients of Hg(II), As(III), Mn(II), Mg(II), Cu(II), Cd(II) were determined in agarose gel and those of Ba(II), Cd(II), Cu(II), Mg(II), Mn(II) e Zn(II) in cellulose acetate membranes. These materials presented good performance and the reported results can be used as a data base for further DGT studies

Uso da técnica de difusão em filmes finos por gradientes de concentração (DGT) para determinação in situ de metais-traço nos rios da Bacia Amazônica Central

Este projeto tem como principal objetivo avaliar a eficiência da técnica de difusão em filmes finos por gradientes de concentração (DGT) para a determinação da fração lábil de metais em águas da bacia Amazônica. Em decorrência da complexidade do uso da DGT, especificamente para algumas amostras da região amazônica (baixa força iônica e alto teor de matéria orgânica) foi desenvolvido um novo procedimento analítico. O procedimento é baseado na calibração em laboratório dos dispositivos DGT especificamente para alguns dos principais rios da bacia Amazônica Central (Negro, Solimões e Amazonas), medindo o coeficiente de difusão aparente de alguns metais. Foi avaliada a adequabilidade deste procedimento fazendo a determinação in situ de alumínio, cádmio, chumbo, cobalto, cobre, manganês, níquel e zinco. Também poderá ser avaliado o emprego de géis com diferentes porosidades para alumínio e cobreThe main purpose of this project is to evaluate the effectiveness of diffusive gradients in thin films technique (DGT) for determination of fraction of labile metals in waters of the Amazon basin. Because of the complexity of the use of DGT, specifically for some samples of the Amazon region (low ionic strength and high organic matter content) has been developed a new analytical procedure. The procedure is based on the determination of an apparent diffusion coefficient (Dap) in laboratory by deployments in a similar matrix to that site of study (major rivers of the Amazon Central basin – Negro, Solimões and Amazonas). The Dap determined is then used for in situ measurements. It was evaluated the suitability of this procedure by the in situ determination of aluminum, cadmium, lead, cobalt, copper, manganese, nickel and zin

MONITORAMENTO E REMOÇÃO DE METAIS NA DIGESTÃO ANAERÓBIA TERMOFÍLICA EXTREMA DE VINHAÇA DE CANA-DE-AÇÚCAR

The determination of trace elements contents and their removal is an important information for the understanding of methanogenic processes involving anaerobic digestion of various types of wastewater. However, there are still gaps in the trace elements determination for the anaerobic digestion of vinasse sugarcane due to the complexity of this type of wastewater. Therefore, the present study was reported the monitoring results of B, Co, Cu, Fe, Mn, Ni, Se, V and Zn concentrations and their removal efficiencies in an extreme thermophilic anaerobic structured-bed reactor treating sugarcane vinasse. The maximum concentrations detected in sugarcane vinasse samples were 0.2, 0.05, 0.9, 12.7, 4.3, 0.15, 0.08, 0.05 and 1.1 mg L-1 for B, Co, Cu, Fe, Mn, Ni, Se, V, and Zn, respectively.  The mean removal efficiencies of trace elements, in the decreasing order were: Mn (80 ± 25%), Zn (78 ± 23%), Cu (77 ± 22%), Ni (68 ± 32%), Fe (63 ± 19%), V (60 ± 24%), B (60 ± 30%), Se (56 ± 22%) and Co (52 ± 22%). The removal efficiencies of trace elements that have reached at least 50%, indicating the reactor capacity in the removal of micronutrients and macronutrients. The analysis of trace elements concentrations presented in this study is important and can be a basis of impact and environmental studies involving the trace elements fate in other environmental matrices (for example, soils, surface and groundwater) avoiding environmental impacts adverse.La determinación del contenido de elementos traza y su remoción es información relevante para comprender los procesos metanogénicos que implican la digestión anaeróbica de diferentes tipos de aguas residuales. Sin embargo, todavía hay lagunas en la evaluación de elementos traza en la digestión anaeróbica de la vinaza de caña de azúcar, debido a la complejidad de este tipo de aguas residuales. En este contexto, la concentración total de elementos B, Co, Cu, Fe, Mn, Ni, Se, V y Zn y sus eficiencias de eliminación se monitorearon en un reactor de lecho fijo estructurado (ASTBR) alimentado con vinaza de caña de azúcar en condiciones de termofilia extrema. Las concentraciones máximas detectadas en las muestras de vinaza de caña de azúcar fueron 0.2; 0,05; 0.9; 12,7; 4.3; 0,15; 0,08; 0.05 y 1.1 mg L-1 para B, Co, Cu, Fe, Mn, Ni, Se, V y Zn, respectivamente. Las eficiencias medias de remoción de metales, en orden decreciente, fueron: Mn (80 ± 25%), Zn (78 ± 23%), Cu (77 ± 22%), Ni (68 ± 32%), Fe (63 ± 19%), V (60 ± 24%), B (60 ± 30%), Se (56 ± 22%) y Co (52 ± 22%). La eficiencia de la eliminación de elementos traza que alcanzó al menos el 50%, indica la capacidad del reactor para eliminar micronutrientes y macronutrientes. El análisis de la concentración de elementos traza presentado en este estudio es importante y puede servir como base para estudios de impacto y monitoreo ambiental que involucra la ruta de estos elementos traza en otras matrices ambientales (por ejemplo, suelos, aguas superficiales y subterráneas) evitando impactos ambientales adverso.A determinação dos teores de elementos-traço e sua remoção é uma informação relevante para a compreensão dos processos metanogênicos envolvendo a digestão anaeróbia de diversos tipos de águas residuárias. Entretanto, ainda existem lacunas na avaliação de elementos-traço na digestão anaeróbia da vinhaça de cana-de-açúcar, devido à complexidade deste tipo de água residuária. Diante desse contexto, a concentração total dos elementos B, Co, Cu, Fe, Mn, Ni, Se, V e Zn e suas eficiências de remoção foram monitoradas em um reator de leito fixo estruturado (ASTBR) alimentado com vinhaça de cana-de-açúcar sob condição de termofilia extrema. As concentrações máximas detectadas nas amostras de vinhaça de cana-de-açúcar foram 0,2; 0,05; 0,9; 12,7; 4,3; 0,15; 0,08; 0,05 e 1,1 mg L-1 para B, Co, Cu, Fe, Mn, Ni, Se, V e Zn, respectivamente. As eficiências médias de remoção dos metais, em ordem decrescente, foram: Mn (80 ± 25%), Zn (78 ± 23%), Cu (77 ± 22%), Ni (68 ± 32%), Fe (63 ± 19%), V (60 ± 24%), B (60 ± 30%), Se (56 ± 22%) e Co (52 ± 22%). As eficiências de remoção dos elementos-traço que atingiram no mínimo 50%, indicam a capacidade do reator na remoção de micronutrientes e macronutrientes. A análise da concentração dos elementos-traço apresentadas neste estudo é importante e pode servir de base para estudos de impacto e monitoramento ambiental envolvendo a rota destes elementos-traço nas demais matrizes ambientais (por exemplo, solos, águas superficiais e subterrâneas) evitando impactos ambientais adversos

Evaluation of diffusive gradients in thin films technique (DGT) for measuring Al, Cd, Co, Cu, Mn, Ni, and Zn in Amazonian rivers

Studies concerning the lability and bioavailability of trace metals have played a prominent role in the search for contamination of water resources. This work describes the first application yet of the diffusive gradients in thin films technique (DGT) to the determination of the fraction of free plus labile metals in waters from the Amazon Basin. Due to the complexity of the use of DGT for samples with low ionic strength and high organic matter content (characteristic of Amazonian rivers), a new analytical procedure was developed. The method is based on the determinations of apparent diffusion coefficients (Dap) in the laboratory, by performing deployments in samples collected in the corresponding sites of study. The Dap thereby determined is then used for in situ measurements. The suitability of the proposed approach for determination of labile Al, Cd, Co, Cu, Mn, Ni, and Zn in the Amazon River and Rio Negro (English: Black River) was evaluated. Except for Co, Mn (in a deployment at Rio Negro), Ni and Zn (in a deployment at Amazon River), labile in situ measurements were lower or similar to dissolved concentrations, indicating suitability of the proposed approach. © 2013 Springer Science+Business Media Dordrecht

Determination of mercury in river water by diffusive gradients in thin films using P81 membrane as binding layer

In this work, a device based on diffusive gradients in thin films (DGT) was evaluated for the determination of Hg(II) in river water. The DGT device was assembled with a cellulose phosphate ion exchange membrane (P81 Whatman) as a binding phase and agarose gel 1.5% (m/v) as a diffusive layer. Laboratory deployments showed that the binding of Hg2+ ([Hg-DGT]/[Hg-solution]) by P81 membrane was more effective (97%) than the Chelex 100 resin (80%).The effect of ionic strength, pH and potential interfering ions on Hg binding with DGT's was investigated. The results showed no significant effect on the binding of Hg(II) at pH range from 3.5 to 8.5 and at an ionic strength range from 0.0005 to 0.1 mol L-1. Uptakes of 50 mu g L-1 Hg(II) by P81 membrane were not affected by Fe, Mn, Zn, Cu, Ca and Mg at the concentration range of 200-1800 mu g L-1. Finally, the DGT device using the P81 as the binding layer was applied for in situ measurements of Hg in river water. For in situ measurements, the labile Hg concentration (from <2 to 13 ng L-1) was lower than 10% of the dissolved fraction (from 155 to 446 ng L-1). (C) 2014 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES