Browsing by Issue Date, starting with "2014"
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- Valorização de recursos minerais : contribuição do projecto MinReMol para uma recuperação sustentável do rénio a partir de resíduos mineirosPublication . Silva, Teresa; Figueiredo, M. Ondina; Santos, Renata; de Oliveira, Daniel Pipa Soares; Veiga, JP; Batista, Maria Joao
- Catalisadores de automóvel: Caracterização, Reciclagem e Recuperação de Metais PreciososPublication . Paiva, A. P.; Nogueira, Carlos; Costa, Ana M. Rosa da; Costa, M. ClaraOs catalisadores de automóvel desempenham um papel importante no tratamento dos gases de escape dos veículos, minimizando as emissões de substâncias nocivas para o ambiente. No final do seu ciclo de vida constituem resíduos que devem ser reciclados, não só por razões ambientais, mas também económicas e de conservação de recursos. Os agentes catalíticos destes dispositivos são os metais nobres do grupo da platina (Pt, Pd e Rh) cuja recuperação é crucial pelo seu valor e raridade. Neste artigo apresenta-se uma descrição do funcionamento, composição e de processos para a reciclagem de catalisadores de automóvel, bem como alguns resultados de um projecto de investigação em curso que visa contribuir para o desenvolvimento de operações hidro-metalúrgicas, como a lixiviação e a extracção por solventes, aplicáveis aos metais nobres contidos nestes resíduos. Estudou-se a lixiviação em meio de HCl, na presença de um oxidante, demonstrando-se o efeito de variáveis processuais como a concentração dos reagentes e a temperatura nos rendimentos de lixiviação dos metais. Foram também desenvolvidos extractantes (diamidas), que extraem eficiente e selectivamente os metais nobres de meios cloretados, possibilitando a sua separação e recuperação.
- Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestionPublication . Gil, Luís; La Cara, F.; Marques, Isabel PaulaIn addition to energy benefits, anaerobic digestion offers other interesting advantages. The cork industry is of great environmental, economic and social significance in the western Mediterranean region, with Portugal being the world-leading producer and exporter. Cork boiling wastewater (CBW) is a toxic and recalcitrant organic effluent produced by this sector, which constitutes a serious environmental hazard. However, there is no documented research on anaerobic treatment/valorization performed with this effluent. The work presented here was developed with the aim to use the anaerobic digestion process to convert the CBW polluting organic load into an energy carrier gas and valuable molecules for industry.
- Towards the recovery of by-product metals from mine wastes : an X-Ray absorption spectroscopy study on the binding state of rhenium in debris from a centennial Iberian Pyrite Belt minePublication . Figueiredo, M. Ondina; Silva, Teresa; Veiga, JP; de Oliveira, Daniel Pipa Soares; Batista, Maria JoaoRhenium is a very scarce element, occurring in the Earth's crust mainly carried by molybdenite (MoS2). Due to a very low availability comparative to actual industrial demand, rhenium is nowadays one of the most expensive mineral commodities and an increased interest is focused on exploring residues resulting from a long-term mining, particularly of sulphide ore deposits. It is therefore noteworthy to assign the presence of rhenium (in a concentration up to 3 ppm) in the waste materials from the old sulphur factory at the abandoned mine of São Domingos (Iberian Pyrite Belt, Southeast Portugal), exploited since the Roman occupation of Iberia. Aiming at a potential sustainable recovery of rhenium as a by-product, X-ray near-edge absorption spectroscopy (XANES) was applied to clarify the Re-binding and mode of occurrence by comparing Re L3-edge XANES spectra obtained from mine waste samples (previously fully characterized by X-ray laboratory techniques) with similar spectra collected from Re-rich molybdenites (Mo1-xRexS2) and from Re-O model compounds configuring various valences and coordination environments of rhenium ions. Obtained results are commented, ruling out a possible Re-S binding and rather conforming with the binding of rhenium to oxygen in the analysed mine waste materials.
- Selecting low-cost carbon sources for carotenoid and lipid production by the pink yeast Rhodosporidium toruloides NCYC 921 using flow cytometryPublication . Freitas, Claúdia; Parreira, Teresa M.; Roseiro, J. Carlos; Reis, Alberto; Silva, Teresa Lopes daThe present work studied low-cost carbon sources for carotenoid and lipid production using the yeast Rhodosporidum toruloides NCYC 921. Carob pulp syrup and sugarcane molasses at different concentrations were used as low-cost carbon sources in R. toruloides batch cultivations. Carob pulp syrup containing a total sugar concentration of 75 g L1 induced the highest total fatty acid productivity (1.90 g L1 h1) and the highest carotenoid productivity (9.79 lg L1 h1). Flow cytometric analysis revealed that most of the yeast cells (>60%) grown on carob pulp syrup displayed intact polarised membranes, conversely to the cells grown on sugarcane molasses, wherein a large proportion (>45%) displayed permeabilised cytoplasmic membranes.
- PV system with maximum power point tracking: modeling, simulation and experimental resultsPublication . Pereira, R.; Melício, R.; Mendes, V. M. F.; Joyce, AThis paper focuses on the five parameters modeling, consisting on a current controlled generator, single-diode, a shunt and series resistances. Also, a simulation, identification of the parameters for a photovoltaic system and the maximum power point tracking based on VP„g„g is presented. The identification of parameters and the performance of the equivalent circuit model for a solar module simulation are validated by data measured on the photovoltaic system.
- Dynamics of knowledge production and technology diffusion: Insights from the emergence of wind energyPublication . Sousa, Cristina; Bento, Nuno; Fontes, MargaridaThe objective of this paper is to contribute to a better understanding of the relation between the dynamics of knowledge production and technology diffusion along the process of emergence of a new technology, as it unfolds in diverse spatial locations. For this purpose, the paper traces the process of knowledge production over time – expressed in the number of scientific publications - and assesses how its dynamics relate with those of technology up-scaling and diffusion, for the case of a new renewable energy technology: wind power. It also compares these processes in different spatial areas, looking at similarities and differences in the evolving patterns, in initial markets and follower regions. In order to trace the dynamics of knowledge production we conduct a bibliometric analysis, using data collected from the Thomson Reuters Web of Science database (for the period 1970-2012). In order to trace the diffusion dynamics we use data collected on both unit scale of turbines and installed capacity of wind power (starting in late 1970s), following the empirical scaling methodology. These analyses are conducted at global scale and, subsequently, at a regional scale, for a pioneer (Denmark) and a fast follower (Portugal). The comparison of the outcomes from the bibliometric and the technology growth analyses permits to understand the rhythm and order in which knowledge was created and applied in this particular innovation. It also provides a preliminary account of the interplay between pioneer and fast follower regions.
- Identification and characterisation of xylanolytic yeasts isolated from decaying wood and sugarcane bagasse in BrazilPublication . Lara, Carla A.; Santos, Renata O.; Cadete, Raquel, M.; Ferreira, Carla; Marques, SusanaIn this study, yeasts associated with lignocellulosic materials in Brazil, including decaying wood and sugarcane bagasse, were isolated, and their ability to produce xylanolytic enzymes was investigated. A total of 358 yeast isolates were obtained, with 198 strains isolated from decaying wood and 160 strains isolated from decaying sugarcane bagasse samples. Seventy-five isolates possessed xylanase activity in solid medium and were identified as belonging to nine species: Candida intermedia, C. tropicalis, Meyerozyma guilliermondii, Scheffersomyces shehatae, Sugiyamaella smithiae, Cryptococcus diffluens, Cr. heveanensis, Cr. laurentii and Trichosporon mycotoxinivorans. Twenty-one isolates were further screened for total xylanase activity in liquid medium with xylan, and five xylanolytic yeasts were selected for further characterization, which included quantitative analysis of growth in xylan and xylose and xylanase and ß-d-xylosidase activities. The yeasts showing the highest growth rate and cell density in xylan, Cr. laurentii UFMG-HB-48, Su. smithiae UFMG-HM-80.1 and Sc. shehatae UFMG-HM-9.1a, were, simultaneously, those exhibiting higher xylanase activity. Xylan induced the highest level of (extracellular) xylanase activity in Cr. laurentii UFMG-HB-48 and the highest level of (intracellular, extracellular and membrane-associated) ß-d-xylosidase activity in Su. smithiae UFMG-HM-80.1. Also, significant ß-d-xylosidase levels were detected in xylan-induced cultures of Cr. laurentii UFMG-HB-48 and Sc. shehatae UFMG-HM-9.1a, mainly in extracellular and intracellular spaces, respectively. Under xylose induction, Cr. laurentii UFMG-HB-48 showed the highest intracellular ß-d-xylosidase activity among all the yeast tested. C. tropicalis UFMG-HB 93a showed its higher (intracellular) ß-d-xylosidase activity under xylose induction and higher at 30 °C than at 50 °C. This study revealed different xylanolytic abilities and strategies in yeasts to metabolise xylan and/or its hydrolysis products (xylo-oligosaccharides and xylose). Xylanolytic yeasts are able to secrete xylanolytic enzymes mainly when induced by xylan and present different strategies (intra- and/or extracellular hydrolysis) for the metabolism of xylo-oligosaccharides. Some of the unique xylanolytic traits identified here should be further explored for their applicability in specific biotechnological processes.
- Biorefinery concept with green solvents towards the phenolic valorizationPublication . Lukasik, Rafal M.The efficient separation, hydrolysis and conversion of principal components of lignocellulosic biomass allows to produce chemicals and value added compounds. Ionic liquids (ILs) have been used for the pre-treatment and fractionation of biomass.1-3 The pre-treatment reveals that phenolic compounds were found in the IL phase. This work was devoted for the extraction of phenolic compounds from the recovered IL liquid using several adsorption resins in small scale batch processes. Phenolic compounds, such as vanillin, catechol and flavonoids were identified in extraction samples and also quantified. Temperature, residence time and water amount were evaluated in order to find optimal extraction conditions of phenolic compounds from IL.
- Optimality-based bound contraction with multiparametric disaggregation for the global optimization of mixed-integer bilinear problemsPublication . Castro, Pedro; Grossmann, Ignacio E.We address nonconvex mixed-integer bilinear problems where the main challenge is the computation of a tight upper bound for the objective function to be maximized. This can be obtained by using the recently developed concept of multiparametric disaggregation following the solution of a mixed-integer linear relaxation of the bilinear problem. Besides showing that it can provide tighter bounds than a commercial global optimization solver within a given computational time, we propose to also take advantage of the relaxed formulation for contracting the variables domain and further reduce the optimality gap. Through the solution of a real-life case study from a hydroelectric power system, we show that this can be an efficient approach depending on the problem size. The relaxed formulation from multiparametric formulation is provided for a generic numeric representation system featuring a base between 2 (binary) and 10 (decimal).