Determinação de metais em água produzida de petróleo

In order to enable the reuse of the large surplus volume of petroleum produced water for irrigation of crops inedible, the quality evaluation of this water is very important. This work aimed to evaluate the effectiveness of the diffusive gradient in thin films technique (DGT) for the determination of labile Cu (II), Mn (II) and Zn (II) in petroleum produced water destined to reuse in agriculture. Samples were collected at the exit of the wastewater treatment plant (WWTP) (after separation oil/water and flotation) of a Petrobrás onshore production region. Basically, the laboratory experiments with DGT devices involved the evaluation of the behavior of the main variables of the technique for determination of analytes in the samples (diffusion coefficients, immersion time, fractionation of organic and inorganic species, and performance of diffusion gels with different porosities, among others). Also, experiments were conducted based on the solid phase extraction (SPE) protocol with Chelex- 100 resin using previously established protocols to support the study. During the project the possibility of in situ immersions in water treatment plants was evaluated. The DGT technique presented satisfactory results for determination of Mn in produced water, and can be used for in situ determinations. However, the results obtained for Cu and Zn show the need of additional studiesVisando possibilitar o reuso do grande volume excedente de água produzida de petróleo para irrigação de culturas não comestíveis, a avaliação da qualidade desta água é muito importante. Este trabalho teve 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 Cu (II), Mn(II) e Zn(II) em águas produzidas de petróleo destinadas a reuso em agricultura. Foram coletadas amostras na saída da estação de tratamento de efluentes - ETE (após separação água/óleo e flotação) de uma região de produção “onshore” da Petrobrás. Basicamente, os experimentos em laboratório com os dispositivos DGT envolveram a avaliação do comportamento das principais variáveis da técnica para determinações dos analitos nas amostras (coeficientes de difusão, tempo de imersão, fracionamento de espécies orgânicas e inorgânicas, desempenho dos géis de difusão com porosidades diferentes, entre outras). Também foram conduzidos experimentos baseados na extração em fase sólida (SPE) com a resina Chelex-100 usando protocolos previamente estabelecidos para suportar o estudo. Durante o projeto foi avaliada a possibilidade de imersões in situ em estações de tratamento de água para irrigação. A técnica DGT apresentou resultados satisfatórios para determinação de Mn em água produzida, podendo ser utilizada para determinações in situ. Contudo, os resultados obtidos para Cu e Zn mostram a necessidade de estudos adicionai

Speciation of lead in seawater and river water by using Saccharomyces cerevisiae immobilized in agarose gel as a binding agent in the diffusive gradients in thin films technique

Saccharomyces cerevisiae immobilized in agarose gel is proposed as a binding agent for the diffusive gradients in thin films (DGT) technique for determination of Pb in river water and seawater. DGT samplers were assembled with the proposed binding agent (25-mm disk containing 20 %, m/v, S. cerevisiae and 3.0 %, m/v, agarose) and a diffusive layer of cellulose (3MM Chr chromatography paper of 25-mm diameter). The effects of some DGT parameters (e.g., immersion time, ionic strength, and pH) were evaluated. Elution of Pb from the binding agent was effectively done with 1.75 mol L-1 HNO3. The deployment curve (between 2 and 24 h) was characterized by a significant uptake of Pb (346 ng Pb h(-1)) and good linear regression (R (2) = 0.9757). The experimental results are in excellent agreement with the predicted theoretical curve for mass uptake. Consistent results were found for solutions with ionic strengths of 0.005 mol L-1 or greater and within a pH range of 4.5-8.5. Interferences from Cu (20:1), Mn (20:1), Fe (20:1), Zn (20:1), Ca (250:1), and Mg (250:1) in Pb retention were negligible. Determination of Pb in spiked river water samples (from the Corumbatai and Piracicaba rivers) performed using the proposed device was in agreement with total dissolved Pb, whereas measurements in seawater suggest that of the various species of Pb present in the samples, only cationic Pb species are adsorbed by the agarose-yeast gel disks. The in situ concentration of Pb obtained at two different sites of the Rio Claro stream (Corumbatai basin) were 1.13 +/- 0.01 and 1.34 +/- 0.04 mu g L-1. For 72-h deployments, a detection limit of 0.75 mu g L-1 was calculated. The combination of inductively coupled plasma optical emission spectroscopy and in situ deployments of DGT samplers during the 72-h period makes possible the determination of labile Pb in river water.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq