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- THE SIMULATION OF INTERACTING LIQUID-LIQUID DISPERSIONS - A NEW ALGORITHM AND ITS POTENTIALITYPublication . Guimarães, M. M. L.; Cruz-Pinto, J. J. C.; Regueiras, P. F. R.; Madureira, C. N. M.[Abstract] The simulation of interacting liquid-liquid dispersions undergoing mass transfer and/or chemical reactions is a major chemical engineering problem, that has not yet been satisfactorily solved. The difficulties do not exclusively lie on the experimental validation of the models and their predictions, but are still rooted on the inability of current algorithms to describe the real nature of the dispersion, namely its full trivariate structure - distribution of drop volumes (v), ages (tT) and _= solute concentrations (c) - where v, t and ce are not satistically independent. A survey is given of the authors' latest, recently published (1,2), work and a detailed discussion is then presented of the fine structure and behaviour of the dispersion; the major requirement of an adequate statistical analysis of the simulation results is also dealt with. The paper ends with the authors views on possible trends of future research on this topic.
- Efficient computer simulation of the dynamics of na agitated liquid-liquid extraction columnPublication . Guimarães, M. M. L.; Gomes, M. L.; Regueiras, P. F. R.; Ribeiro, M. L.; Cruz-Pinto, J. J. C.Given the difficulties associated with experimentation upon liquid-liquid extraction processes, computer simulation of these processes has recently acquired great relevance and usefulness as complement, if not an alternative, to direct experimentation. This is becoming increasingly attractive, as both the power and the availability of personal computing increase. Recently, Ribeiro (1995), Ribeiro ef al. (1997)) developed a fast and precise algorithm, adapting population balance models as Coulaloglou and Tavlarides' (1977) for the dispersed phase breakage and coalescence, and both the rigid and the oscillating drop models as proposed by Cruz-Pinto ef al. (1983), for mass transfer. The algorithm enabled the simulation’ of the evolution in time of the trivariate joint distribution of drop properties in two-phase continuous mixers, in steady and transient states. A simplified version of this algorithm, that calculates the drop size distribution and the mean and standard deviation of solute concentration within each volume class, was further developed by Regueiras ef al (1996). In this work, the applicability of this simplified algorithm to the dynamic simulation of a Kithni liquid-liquid extraction column is illustrated. A transport model was developed from previous models of Cruz-Pinto (1979). Coulaloglou and Tavlarides’ (1977) drop interaction model was again adopted. It is shown that the algorithm is able to describe both the transient and the steady-state behaviour of a Kihni pilot column (Technical University of Munich), and the simulation runs that were made show good agreement with the experimental results. The present version of the algorithm predicts local hold-ups and drop size distributions at different column stages. So far, the results do not include mass transfer, but future work will contemplate this feature.
- Tabela Periódica: Um Elemento em cada casa, uma casa para cada ElementoPublication . Delerue-Matos, Cristina; Morais, Simone; Freitas, Olga; Teixeira, Salomé; Soares da Silva, Maria Aurora; de Sá Barroso, Maria de FátimaUm concurso sobre a Tabela Periódica? Mas isso, é o que eu penso que é? e é motivo para um concurso? O resultado está à vista. Os cerca de 40 trabalhos apresentados a concurso, envolvendo um total de 180 participantes, utilizaram técnicas diversificadas nas área da pintura, escultura, música, literatura, fotografia, culinária, vídeo, novas tecnologias… A Tabela Periódica transformou-se, associando o carácter científico e sua semiótica a uma visão mais abrangente no campo da percepção, da estética, da imagem, das sensações, isto é da Arte. Surge assim uma abordagem inovadora e irreverente, de uma matéria classificada pelos alunos de "árida e inacessível". Um processo de levar a Química às camadas mais jovens e a todos aqueles que se interessam pela Ciência.
- Guia de segurança para laboratóriosPublication . Delerue-Matos, Cristina; Ferreira Sales, Maria Goreti; Martins, Florinda; Martins, Isabel; Rosas, Mónica; Morais, SérgioSegurança em laboratórios químicos é uma área em que o Grupo de Reacção e Análises Químicas (GRAQ), pertencente ao Laboratório Associado REQUIMTE (REde de QUÍMica e TEcnologia), conjuntamente com o TRELAB (TRatamento de REsíduos de LABoratório) do Instituto Superior de Engenharia do Porto do Instituto Politécnico do Porto vêm realizando actividades de Investigação e Desenvolvimento. A experiência que a equipa tem vindo a adquirir tem resultado na orientação de diferentes acções de formação dirigidas especialmente a técnicos de laboratórios de ensino e investigação, de análises químicas, de controlo de qualidade e de processos, enologia... que reconhecem a necessidade de trabalhar em ambiente seguro. Este Guia é fruto de uma acção dirigida a técnicos e investigadores de laboratórios de Enologia associados da ALABE (Associação de LABoratórios de Enologia). Pretende ser uma compilação de notas e regras facilitadoras de consulta a implementar em laboratórios interessados em caminhar para uma gestão que contemple a segurança, a qualidade e o ambiente. Assim o Guia versa a temática da Segurança, a que se associa a vertente da Qualidade e do Ambiente. Nesta última estão incluídas as preocupações da Gestão dos Resíduos de Laboratório numa perspectiva sustentável, ogo economicista, de recuperação de recursos e que segue o lema #resíduo trata resíduo". Pretende-se que o Guia seja pragmático e venha a ser útil.
- Characterization of Active Sites on Carbon CatalystsPublication . Figueiredo, José L.; Pereira, Manuel F. R.; Freitas, Maria M. A.; Órfão, José J. M.A method based on the deconvolution of TPD spectra is proposed for the characterization of surface oxygen groups, which can act as the active sites on carbon catalysts. The method, which was previously used to characterize activated carbons oxidized in the gas phase, has been extended and applied to other materials, carbons oxidized in the liquid phase. It is shown that this method fits quite well the TPD experimental data of the original activated carbon as well as the gas-phase and liquid-phase oxidized materials and is suitable to estimate the amounts of each type of oxygen surface groups.
- Microalgae for biodiesel production and other applications: A reviewPublication . Mata, Teresa M.; Martins, António A.; Caetano, Nídia SáSustainable production of renewable energy is being hotly debated globally since it is increasingly understood that first generation biofuels, primarily produced from food crops and mostly oil seeds are limited in their ability to achieve targets for biofuel production, climate change mitigation and economic growth. These concerns have increased the interest in developing second generation biofuels produced from non-food feedstocks such as microalgae, which potentially offer greatest opportunities in the longer term. This paper reviews the current status of microalgae use for biodiesel production, including their cultivation, harvesting, and processing. The microalgae species most used for biodiesel production are presented and their main advantages described in comparison with other available biodiesel feedstocks. The various aspects associated with the design of microalgae production units are described, giving an overview of the current state of development of algae cultivation systems (photo-bioreactors and open ponds). Other potential applications and products from microalgae are also presented such as for biological sequestration of CO2, wastewater treatment, in human health, as food additive, and for aquaculture.
- Lipophilic Caffeic and Ferulic Acid Derivatives Presenting Cytotoxicity against Human Breast Cancer CellsPublication . Serafim, Teresa L.; Carvalho, Filipa S.; Marques, Maria P. M.; Calheiros, Rita; Silva, Tiago; Garrido, J.M.P.J.; Milhazes, Nuno; Borges, Fernanda; Roleira, Fernanda; Silva, Elisário T.; Holy, Jon; Oliveira, Paulo J.In the present work, lipophilic caffeic and ferulic acid derivatives were synthesized, and their cytotoxicity on cultured breast cancer cells was compared. A total of six compounds were initially evaluated: caffeic acid (CA), hexyl caffeate (HC), caffeoylhexylamide (HCA), ferulic acid (FA), hexyl ferulate (HF), and feruloylhexylamide (HFA). Cell proliferation, cell cycle progression, and apoptotic signaling were investigated in three human breast cancer cell lines, including estrogen-sensitive (MCF-7) and insensitive (MDA-MB-231 and HS578T). Furthermore, direct mitochondrial effects of parent and modified compounds were investigated by using isolated liver mitochondria. The results indicated that although the parent compounds presented no cytotoxicity, the new compounds inhibited cell proliferation and induced cell cycle alterations and cell death, with a predominant effect on MCF-7 cells. Interestingly, cell cyle data indicates that effects on nontumor BJ fibroblasts were predominantly cytostatic and not cytotoxic. The parent compounds and derivatives also promoted direct alterations on hepatic mitochondrial bioenergetics, although the most unexpected and never before reported one was that FA induces the mitochondrial permeability transition. The results show that the new caffeic and ferulic acid lipophilic derivatives show increased cytotoxicity toward human breast cancer cell lines, although the magnitude and type of effects appear to be dependent on the cell type. Mitochondrial data had no direct correspondence with effects on intact cells suggesting that this organelle may not be a critical component of the cellular effects observed. The data provide a rational approach to the design of effective cytotoxic lipophilic hydroxycinnamic derivatives that in the future could be profitably applied for chemopreventive and/or chemotherapeutic purposes.
- Impact of fluorides on the removal of heavy metals from an electroplating effluent using a flocculent brewer’s yeast strain of Saccharomyces cerevisiaePublication . Machado, Manuela D.; Soares, Eduardo V.; Soares, Helena M.V.M.Besides several toxic heavy metals, electroplating effluents can have in solution different cations and anions, which may influence heavy metals removal by the biomass. Among them, fluorides are commonly used in the electroplating industries and thus can be found in the respective wastewaters. In the present work, the effect of the presence of fluorides in the efficiency of chromium(III), copper(II) and nickel(II) removal, from an effluent, by heat-inactivated cells of a brewing flocculent strain of Saccharomyces cerevisiae was evaluated. The presence of fluorides severely decreased (460%) the removal of chromium(III) by yeast biomass. This effect impaired the effective treatment of the effluent according to the US Environmental Protection Agency and the Portuguese law; conversely, a higher removal of copper(II) and nickel(II) was observed. This behaviour can be understood by metal speciation. In the presence of fluorides, chromium(III) was mainly complexed, becoming unavailable for yeast accumulation; this effect decreased the efficiency of chromium(III) removal. Thus, in the presence of fluorides, less chromium(III) is associated with biomass and consequently more yeast binding sites remain available for the uptake of other metals present in solution. This fact explains the increase of copper(II) and nickel(II) removal in the presence of fluorides.
- Selective recovery of chromium, copper, nickel, and zinc from an acid solution using an environmentally friendly processPublication . Machado, Manuela D.; Soares, Eduardo V.; Soares, Helena M.V.M.Purpose Real electroplating effluents contain multiple metals. An important point related with the feasibility of the bioremediation process is linked with the strategy to recover selectively metals. In this work, a multimetal solution, obtained after microwave acid digestion of the ashes resulted from the incineration of Saccharomyces cerevisiae contaminated biomass, was used to recover selectively chromium, copper, nickel, and zinc. Results The acid solution contained 3.8, 0.4, 2.8, and 0.2 g/L of chromium(III), copper, nickel, and zinc, respectively. The strategy developed consisted of recovering copper (97.6%), as a metal, by electrolyzing the solution at a controlled potential. Then, the simultaneous alkalinization of the solution (pH 14), addition of H2O2, and heating of the solution led to a complete oxidation of chromium and nickel recovery (87.9% as a precipitate of nickel hydroxide). After adjusting the pH of the remaining solution at pH 10, selective recovery of zinc (82.7% as zinc hydroxide) and chromium (95.4% as a solution of cromate) was achieved. Conclusion The approach, used in the present work, allowed a selective and efficient recovery of chromium, copper, nickel, and zinc from an acid solution using a combined electrochemical and chemical process. The strategy proposed can be used for the selective recovery of metals present in an acid digestion solution, which resulted from the incineration of ashes of biomass used in the treatment of heavy metals rich industrial effluents.
- Introduction of the parameter 'Total Organic Carbon' (TOC) as a standard for the quality control of swimming pool waterPublication . Beleza, Vitorino de Matos; Costa, Rosária Santos; Baptista, Marta Pinto; Beleza, Vitorino; Pereira, IsabelSwimmers introduce organic compounds into swimming pools due to the transferring of sweat, saliva, skin, hair, urine, feces, among other materials, to the water. Water quality control in the tank must include some chemical parameters that will quantitatively reflect the presence of these contaminants in the water. Oxidability to permanganate is included in the regulations and norms of public swimming pools in most developed countries. According to the Portuguese norm NP-731, permanganate oxidability is determined by the oxidation of organic compounds in the water by potassium permanganate in acidic conditions when boiling for 10 minutes. |n fact, this procedure detects all reductants oxidized by the essay conditions, whether organic or inorganic. To overcome these limitations, several entities suggested the determination of Total Organic Carbon (TOC). lsocyanuric acid, H30;C;N;, is used as a stabilising agent for free chlorine. In its combustion, cyanuric acid is totally oxidised, and the products of this reaction are carbon dioxide, which contributes to the TOC value, water and nitrogen. Analytical confirmation of the carbon:isocyanuric acid relationship was performed in the Centro de Estudos de Aguas laboratory, achieving ‘the value of 0.27 quite close to the theoretical relation carbon:isocyanuric acid (0.28). This relationship will help to definition of a maximum value for TOC in swimming pool water, in function of its depth.