Estudo da intensificação da coalescência de emulsões de água em óleo com a aplicação de onda estacionária de ultrassom.

Considerando que o petróleo quando extraído dos poços em águas profundas chega a ter teor de água superior a 50% e que antes de ser enviado à refinaria deve ter uma quantidade de água inferior a 1%, torna-se necessário o uso de técnicas de redução da quantidade de água. Durante a extração do petróleo formam-se emulsões de água em óleo que são muito estáveis devido a um filme interfacial contendo asfaltenos e/ou resinas ao redor das gotas de água. Nesse trabalho é apresentada a utilização de ondas estacionárias de ultrassom para realizar a quebra dessas emulsões. Quando gotículas de água com dimensões da ordem de 10m, muito menores que o comprimento de onda, são submetidas a um campo acústico estacionário em óleo, a força de radiação acústica empurra as gotículas para os nós de pressão da onda. Uma célula de coalescência com frequência central ao redor de 1 MHz, constituída por quatro camadas sendo uma piezelétrica, uma de acoplamento sólido, uma com o líquido e outra refletora, foi modelada empregando o método da matriz de transferência, que permite calcular a impedância elétrica em função da frequência. Para minimizar o efeito do gradiente de temperatura entre a entrada e a saída da cavidade da célula, quando está em operação, foram utilizados dois transdutores piezelétricos posicionados transversalmente ao fluxo que são excitados e controlados independentemente. Foi implementado um controlador digital para ajustar a frequência e a potência de cada transdutor. O controlador tem como entrada o módulo e a fase da corrente elétrica no transdutor e como saída a amplitude da tensão elétrica e a frequência. Para as células desenvolvidas, o algoritmo de controle segue um determinado pico de ressonância no interior da cavidade da célula no intervalo de frequência de 1,09 a 1,15 MHz. A separação acústica de emulsões de água em óleo foi realizada em uma planta de laboratório de processamento de petróleo no CENPES/PETROBRAS. Foram testados a variação da quantidade de desemulsificante, o teor inicial de água na emulsão e a influência da vazão do sistema, com uma potência de 80 W. O teor final de água na emulsão mostrou que a aplicação de ultrassom aumentou a coalescência de água da emulsão, em todas as condições testadas, quando comparada a um teste sem aplicação de ultrassom. Identificou-se o tempo de residência no interior da célula de separação como um fator importante no processo de coalescência de emulsões de água e óleo. O uso de desemulsificante químico é necessário para realizar a separação, porém, em quantidades elevadas implicaria no uso de processos adicionais antes do repasse final do petróleo à refinaria. Os teores iniciais de água na emulsão de 30 e 50% indicam que o uso da onda estacionária na coalescência de emulsões não tem limitação quanto a esse parâmetro. De acordo com os resultados obtidos em laboratório, essa técnica seria indicada como uma alternativa para integrar um sistema de processamento primário em conjunto com um separador eletrostático.

Estudo da extração de índio a partir de telas de cristal líquido (LCD).

Ao longo dos últimos anos, o crescimento ao acesso a esse tipo de tecnologia pelos consumidores brasileiros tem intensificado o aumento no interesse ambiental e econômico dos LCDs. Os displays de cristal líquido são utilizados em televisores, calculadoras, telefones celulares, computadores (portáteis e tablets), vídeo games entre outros equipamentos eletrônicos. O avanço tecnológico neste campo tem tornado estes aparelhos obsoletos cada vez mais rápido, aumentando o volume de resíduos de LCDs a ser dispostos em aterros o que contribui para a redução da sua vida útil. Neste contexto, os LCDs provenientes de televisores de LED LCD tem se tornado uma fonte importante de resíduos de equipamentos eletroeletrônicos (REEE). Assim, torna-se essencial o desenvolvimento de métodos e processos para tratamento e reciclagem de LCDs. Deste modo, o objetivo do presente trabalho é a caracterização física e química de telas de cristal líquido provenientes de displays de televisores de LED LCDs e o estudo de uma rota hidrometalúrgica para recuperação de índio. Para tanto se utilizou técnicas de tratamento de minérios e análises físicas e químicas (separação granulométrica, perda ao fogo, visualização em lupa binocular, TGA, FRX, FT-IR) para caracterização do material e quantificação do índio antes e, após, a rota hidrometalúrgica que, por sua vez, foi realizada em reatores de bancada utilizando três agentes lixiviantes (ácido nítrico, sulfúrico e clorídrico), três temperaturas (25ºC, 40ºC e 60ºC) e quatro tempos (0,5h; 1h; 2h e 4h). Encontrou-se que a tela de cristal líquido representa cerca de 20% da massa total do display de televisores de LCD e que é composta por aproximadamente 11% em massa de polímeros e 90% de vidro + cristal líquido. Verificou-se também que há seis camadas poliméricas nas telas de cristal líquido, onde: um conjunto com 3 polímeros compõe o analisador e o polarizador, sendo que o polímero da primeira e da terceira camada de cada conjunto é triacetato de celulose e corresponde a 64% da massa de polímeros das telas. Já o polímero da segunda camada é polivinilalcool e representa 36% da massa de polímeros. Os melhores resultados obtidos nos processos de lixiviação foram com o ácido sulfúrico, nas condições de 60°C por 4h, relação sólido-líquido 1/5. Nessas condições, foi extraído em torno de 61% do índio contido tela de LCD.

Some examples of modeling in chemical engineering: thermal treatment of polymers, phase equilibrium calculations and process design

Presentation submitted to PSE Seminar, Chemical Engineering Department, Center for Advanced Process Design-making (CAPD), Carnegie Mellon University, Pittsburgh (USA), October 2012.

Optimal synthesis of liquid-liquid multistage extractors

Presentation in the 11th European Symposium of the Working Party on Computer Aided Process Engineering, Kolding, Denmark, May 27-30, 2001.

Determination of cyclic and linear siloxanes in wastewater samples by ultrasound-assisted dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry

A fast, simple and environmentally friendly ultrasound-assisted dispersive liquid-liquid microextraction (USA-DLLME) procedure has been developed to preconcentrate eight cyclic and linear siloxanes from wastewater samples prior to quantification by gas chromatography-mass spectrometry (GC-MS). A two-stage multivariate optimization approach has been developed employing a Plackett-Burman design for screening and selecting the significant factors involved in the USA-DLLME procedure, which was later optimized by means of a circumscribed central composite design. The optimum conditions were: extractant solvent volume, 13 µL; solvent type, chlorobenzene; sample volume, 13 mL; centrifugation speed, 2300 rpm; centrifugation time, 5 min; and sonication time, 2 min. Under the optimized experimental conditions the method gave levels of repeatability with coefficients of variation between 10 and 24% (n=7). Limits of detection were between 0.002 and 1.4 µg L−1. Calculated calibration curves gave high levels of linearity with correlation coefficient values between 0.991 and 0.9997. Finally, the proposed method was applied for the analysis of wastewater samples. Relative recovery values ranged between 71–116% showing that the matrix had a negligible effect upon extraction. To our knowledge, this is the first time that combines LLME and GC-MS for the analysis of methylsiloxanes in wastewater samples.

Screen-printed electrode-based electrochemical detector coupled with in-situ ionic-liquid-assisted dispersive liquid–liquid microextraction for determination of 2,4,6-trinitrotoluene

A novel method is reported, whereby screen-printed electrodes (SPELs) are combined with dispersive liquid–liquid microextraction. In-situ ionic liquid (IL) formation was used as an extractant phase in the microextraction technique and proved to be a simple, fast and inexpensive analytical method. This approach uses miniaturized systems both in sample preparation and in the detection stage, helping to develop environmentally friendly analytical methods and portable devices to enable rapid and onsite measurement. The microextraction method is based on a simple metathesis reaction, in which a water-immiscible IL (1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [Hmim][NTf2]) is formed from a water-miscible IL (1-hexyl-3-methylimidazolium chloride, [Hmim][Cl]) and an ion-exchange reagent (lithium bis[(trifluoromethyl)sulfonyl]imide, LiNTf2) in sample solutions. The explosive 2,4,6-trinitrotoluene (TNT) was used as a model analyte to develop the method. The electrochemical behavior of TNT in [Hmim][NTf2] has been studied in SPELs. The extraction method was first optimized by use of a two-step multivariate optimization strategy, using Plackett–Burman and central composite designs. The method was then evaluated under optimum conditions and a good level of linearity was obtained, with a correlation coefficient of 0.9990. Limits of detection and quantification were 7 μg L−1 and 9 μg L−1, respectively. The repeatability of the proposed method was evaluated at two different spiking levels (20 and 50 μg L−1), and coefficients of variation of 7 % and 5 % (n = 5) were obtained. Tap water and industrial wastewater were selected as real-world water samples to assess the applicability of the method.

Mercury determination in urine samples by gold nanostructured screen-printed carbon electrodes after vortex-assisted ionic liquid dispersive liquid–liquid microextraction

A novel approach is presented to determine mercury in urine samples, employing vortex-assisted ionic liquid dispersive liquid–liquid microextraction and microvolume back-extraction to prepare samples, and screen-printed electrodes modified with gold nanoparticles for voltammetric analysis. Mercury was extracted directly from non-digested urine samples in a water-immiscible ionic liquid, being back-extracted into an acidic aqueous solution. Subsequently, it was determined using gold nanoparticle-modified screen-printed electrodes. Under optimized microextraction conditions, standard addition calibration was applied to urine samples containing 5, 10 and 15 μg L−1 of mercury. Standard addition calibration curves using standards between 0 and 20 μg L−1 gave a high level of linearity with correlation coefficients ranging from 0.990 to 0.999 (N = 5). The limit of detection was empirical and statistically evaluated, obtaining values that ranged from 0.5 to 1.5 μg L−1, and from 1.1 to 1.3 μg L−1, respectively, which are significantly lower than the threshold level established by the World Health Organization for normal mercury content in urine (i.e., 10–20 μg L−1). A certified reference material (REC-8848/Level II) was analyzed to assess method accuracy finding 87% and 3 μg L−1 as the recovery (trueness) and standard deviation values, respectively. Finally, the method was used to analyze spiked urine samples, obtaining good agreement between spiked and found concentrations (recovery ranged from 97 to 100%).

Concentrations of perfluorinated carboxylic acids (PFCAs) and sulfonic acids (PFSAs) in liver samples of different marine mammals (1984-2009)

Temporal variations in concentrations of perfluorinated carboxylic acids (PFCAs) and sulfonic acids (PFSAs), including perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) structural isomers, were examined in livers of pilot whale (Globicephala melas), ringed seal (Phoca hispida), minke whale (Balaenoptera acutorostrata), harbor porpoise (Phocoena phocoena), hooded seal (Cystophora cristata), Atlantic white-sided dolphin (Lagenorhynchus acutus) and in muscle tissue of fin whales (Balaenoptera physalus). The sampling spanned over 20 years (1984-2009) and covered a large geographical area of the North Atlantic and West Greenland. Liver and muscle samples were homogenized, extracted with acetonitrile, cleaned up using hexane and solid phase extraction (SPE), and analyzed by liquid chromatography with negative electrospray tandem mass spectrometry (LC-MS/MS). In general, the levels of the long-chained PFCAs (C9-C12) increased whereas the levels of PFOS remained steady over the studied period. The PFOS isomer pattern in pilot whale liver was relatively constant over the sampling years. However, in ringed seals there seemed to be a decrease in linear PFOS (L-PFOS) with time, going from 91% in 1984 to 83% in 2006.

Dissolved organic carbon concentrations, amino sugar concentrations and highly significantly correlating FT-ICR mass peak magnitudes obtained from solid phase extracted marine dissolved organic matter during POLARSTERN cruise ANT-XXV/1

Dissolved organic matter (DOM) was extracted with solid phase extraction (SPE) from 137 water samples from different climate zones and different depths along an Eastern Atlantic Ocean transect. The extracts were analyzed with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with electrospray ionization (ESI). D14C analyses were performed on subsamples of the SPE-DOM. In addition, the amount of dissolved organic carbon was determined for all water and SPE-DOM samples as well as the yield of amino sugars for selected samples. Linear correlations were observed between the magnitudes of 43% of the FT-ICR mass peaks and the extract D14C values. Decreasing SPE-DOM D14C values went along with a shift in the molecular composition to higher average masses (m/z) and lower hydrogen/carbon (H/C) ratios. The correlation was used to model the SPE-DOM D14C distribution for all 137 samples. Based on single mass peaks a degradation index was developed to compare the degradation state of marine SPE-DOM samples analyzed with FT-ICR MS. A correlation between D14C, degradation index, DOC values and amino sugar yield supports that SPE-DOM analyzed with FT-ICR MS reflects trends of bulk DOM. A relative mass peak magnitude ratio was used to compare aged SPE-DOM and fresh SPE-DOM regarding single mass peaks. The magnitude ratios show a continuum of different reactivities for the single compounds. Only few of the compounds present in the FT-ICR mass spectra are expected to be highly degraded in the oldest water masses of the Pacific Ocean. All other compounds should persist partly thermohaline circulation. Prokaryotic (bacterial) production, transformation and accumulation of this very stable DOM occurs probably primarily in the upper ocean. This DOM is an important contribution to very old DOM, showing that production and degradation are dynamic processes.

Heat extraction from the ANL research salt gradient solar pond /

"ILENR/AE-86/03."

Immobilization of aluminum chloride on MCM-41 as a new catalyst system for liquid-phase isopropylation of naphthalene

A great deal of effort has been made at searching for alternative catalysts to replace conventional Lewis acid catalyst aluminum trichloride (AlCl3). In this paper, immobilization of AlCl3 on mesoporous MCM-41 silica with and without modification was carried out. The catalytic properties of the immobilized catalyst systems for liquid-phase isopropylation of naphthalene were studied and compared with those of H/MCM-41 and H/mordenite. The structures of the surface-immobilized aluminum chloride catalysts were studied and identified by using solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption, and X-ray diffraction (XRD) techniques. The catalytic activity of the immobilized catalysts was found to be similar to that of acidic mordenite zeolite. A significant enhancement in the selectivity of 2,6-diisopropylnaphthalene (2,6-DIPN) was observed over the immobilized aluminum chloride catalysts. Immobilization of aluminum chloride on mesoporous silica coupled with surface silylation is a promising way of developing alternative catalyst system for liquid-phase Friedel-Crafts alkylation reactions. (C) 2002 Elsevier Science B.V. All rights reserved.

A dynamic mathematical model for sequential leach bed anaerobic digestion of organic fraction of municipal solid waste

A mathematical model that describes the operation of a sequential leach bed process for anaerobic digestion of organic fraction of municipal solid waste (MSW) is developed and validated. This model assumes that ultimate mineralisation of the organic component of the waste occurs in three steps, namely solubilisation of particulate matter, fermentation to volatile organic acids (modelled as acetic acid) along with liberation of carbon dioxide and hydrogen, and methanogenesis from acetate and hydrogen. The model incorporates the ionic equilibrium equations arising due to dissolution of carbon dioxide, generation of alkalinity from breakdown of solids and dissociation of acetic acid. Rather than a charge balance, a mass balance on the hydronium and hydroxide ions is used to calculate pH. The flow of liquid through the bed is modelled as occurring through two zones-a permeable zone with high flushing rates and the other more stagnant. Some of the kinetic parameters for the biological processes were obtained from batch MSW digestion experiments. The parameters for flow model were obtained from residence time distribution studies conducted using tritium as a tracer. The model was validated using data from leach bed digestion experiments in which a leachate volume equal to 10% of the fresh waste bed volume was sequenced. The model was then tested, without altering any kinetic or flow parameters, by varying volume of leachate that is sequenced between the beds. Simulations for sequencing/recirculating 5 and 30% of the bed volume are presented and compared with experimental results. (C) 2002 Elsevier Science B.V. All rights reserved.

The measurement of nicotine in human plasma by high-performance liquid chromatography-electrospray-tandem mass spectrometry

The authors describe a reverse-phase high-performance liquid chromatography-electrospray-tandem mass spectrometry method for the measurement of nicotine in human plasma. Samples (500 muL) with added deuterium-labeled d(3)-nicotine as an internal standard (IS) were treated with a 2-step process of ether extraction (6 mL) followed by back-extraction into 0.1% formic acid (50 muL). Chromatography was performed on a phenyl Novapak column with a mobile phase consisting of 50% 10 mM ammonium fortriate (pH 3.3) and acetonitrile (50:50, vol/vol). A flow rate of 0.2 mL/min resulted in a total analysis time of 5 minutes per sample. Mass spectrometric detection was by selected reactant monitoring (nicotine m/z 163.2 --> 130.2; IS m/z 166.2 --> 87.2). The assay was linear from 0.5 to 100 mug/L (r > 0.993, n = 9). The accuracy and imprecision of the method for quality control sampleswere 87.5% to 113% and < 10.2%, respectively. Interday accuracy and imprecision at the limit of quantification (0.5 mug/L) was 113% and 7.2% (n = 4). The process efficiency for nicotine in plasma was > 75%. The method described has good process efficiency, stabilized nicotine, avoided concentration steps, and most importantly minimized potential contamination. Further, we have established that water-based standards and controls are interchangeable with plasma-based samples. This method was used successfully to measure the pharmacokinetic profiles of subjects involved in the development of an aerosol inhalation drug delivery system.

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immuno suppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

Solid phase microextraction of stale flavour volatiles from the headspace of UHT milk

Solid phase microextraction (SPME) offers a solvent-free and less labour-intensive alternative to traditional flavour isolation techniques. In this instance, SPME was optimised for the extraction of 17 stale flavour volatiles (C3-11,13 methyl ketones and C4-10 saturated aldehydes) from the headspace of full-cream ultrahigh-temperature (UHT)-processed milk. A comparison of relative extraction efficiencies was made using three fibre coatings, three extraction times and three extraction temperatures. Linearity of calibration curves, limits of detection and repeatability (coefficients of variation) were also used in determining the optimum extraction conditions. A 2 cm fibre coating of 50130 gm divinylbenzene/Carboxen/polydimethylsiloxane in conjunction with a 15 min extraction at 40 degrees C were chosen as the final optimum conditions. This method can be used as an objective tool for monitoring the flavour quality of UHT milk during storage. (c) 2005 Society of Chemical Industry.