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-In the direct current mode (DC), widely used in electroflocculation (EC), the formation of an impermeable oxide layer on the cathode causes the declining of the efficiency of this process. This disadvantage has been reduced by adopting alternating current (AC). In this study, the effects of AC and DC on operational parameters such as the removal of oils and greases (O&G), color and turbidity from oil-inwater (O/W) emulsions of the petroleum industry using aluminum electrodes were investigated. Removal efficiencies of 95%, 97% and 99% of O&G, color and turbidity with energy consumption of 0.280 kWh/m 3 and electrode consumption of 0.12 g and 0.18 g were achieved at a current density of 3 A, operation time of 3 minutes and initial pH of 9.0 using AC and DC, respectively. In continuous flow tests performed with the same experimental conditions, the electrode consumption at times up to 60 minutes were 1.6 g and 3.4 g using AC and DC, respectively.

This study reports a simple, reusable, and recoverable niobium-based heterogeneous catalysts for Biginelli multicomponent reactions. Different methods of catalysts preparation were investigated. For this purpose, HY-340 (Nb 2 O 5 • nH 2 O) and Nb 2 O 5 were chemically and/or thermally treated and investigated as catalysts for dihydropyrimidinones (DHPMs) production. The catalysts were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, temperature-programmed desorption of NH 3 , adsorption/desorption of N 2 at −196 °C, and thermogravimetric and differential thermal analysis. The characterization results showed that niobium oxides have the potential to be used as catalysts because of high crystallinity and large surface area. Among the tested catalysts, Nb 2 O 5 chemically treated (Nb 2 O 5 /T) showed the best catalytic performance. In the absence of solvents, 94% yield of DHPMs was achieved. Also, Nb 2 O 5 /T can be reused three times without a significant yield decrease. Additionally, a feasible reaction pathway was suggested based on the Knoevenagel mechanism for DHPM synthesis using niobium-based catalysts.

Resumo: Sedimentos de manguezais têm uma grande capacidade em acumular metais traço que podem ser remobilizados e contaminar a água e a biota. Amostras de sedimentos foram coletadas em três florestas de mangue da Baía de Sepetiba (Itacuruçá, Coroa Grande e Guaratiba). Após a coleta foi efetuada a caracterização físico-química dos sedimentos (pH, Eh, salinidade, composição granulométrica, carbono orgânico total-COT, Ntotal e P-total) e as concentrações dos metais traço (Cu, Ni, Pb e Zn) foram determinadas por dois diferentes protocolos de digestão ácida assistidos por micro-ondas (HNO 3 e HCl/HNO 3 ), que foram comparados, a fim de dar suporte à elaboração de uma futura legislação brasileira de avaliação da qualidade do sedimento. Os resultados mostraram que a escolha do método de digestão utilizado na avaliação da contaminação ambiental e no monitoramento de metais traço em sedimentos deve ser feita criteriosamente. Para isso, devem se levar conta as características físicas e químicas dos sedimentos, de forma a se evitarem erros de classificação de impactos ambientais.

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A method based on disposable pipette extraction (DPX) was successfully applied to creatinine determination in urine samples analysis using liquid chromatography with ultraviolet spectrophotometric detection (DPX/LC-UV). DPX variables, number of draw/eject cycles, sample pH, and type of the desorption solvent, were employed in a factorial experimental design to optimize the sorption equilibrium and time analysis. Among the evaluated DPX variables, the highest extraction efficiency was obtained with 500 µL of urine sample mixed with 1 mL of borate solution (pH 9) with one draw/eject cycle followed by liquid desorption of 1 mL of methanol in seven draw/eject cycles. The developed DPX/LC-UV method showed a linear response from the limit of quantification of 0.317 to 3.390 g L -1 with r 2 = 0.996 and inter-day precision with a coefficient of variation below 8.8%. Based on these results, the proposed method can be a useful tool for determining the creatinine levels in urine samples.