In the 25 years since the first report of mixed ionic and electronic conducting ceramics, perovskite membranes underwent both research and development phases, with the latest works entering pilot ...trials for oxygen separation from air. During this time a number of perovskite synthesis methods were investigated from the original solid state chemistry through the more advanced and well established sol–gel route via the Pechinni method. The advances in synthesis methods were possible due to the desirable full incorporation of cations into the A and B-sites of perovskites with a general ABO3 structure. In terms of membrane manufacturing, perovskite hollow fibres attracted a major research effort due to small membrane thickness and high fluxes. This led to a number of investigations by doping with other cations or by surface modification, all aiming at increasing oxygen fluxes. Recently, advanced ceramic processing by tape casting has led to the preparation of very thin dense films either on porous supports or as monoliths containing internal porous regions. All these developments in perovskite synthesis and membrane preparation methods, together with other types of methods requiring special equipment are addressed in this review, including an analysis of the state of the art. Finally, future challenges are discussed in terms of competing technologies and potential industrial design directions of perovskite membranes for oxygen separation from air.
New food technologies are promoting innovations in the food sector. However, not all technologies are accepted and understood by consumers; some cause resistance. The present work sought to study the ...behavior of Brazilian consumers in relation to different food technologies. A questionnaire was administered to a representative sample of 389 respondents in Belo Horizonte-MG, Brazil. Questionnaire collected information on consumer perceptions regarding new technologies by means of the Food Technology Neophobia Scale (FTNS), translated and validated into Portuguese, in addition to familiarity and willingness to try yogurts labeled such as traditional, pasteurized, organic, genetically modified, enriched with bioactive proteins and nanotechnology. Results suggested that neophobia regarding food technology is important to explain consumer behavior in relation to new technologies, especially for nanotechnology. Participants were less familiar with foods labeled as GM and nanotechnology, and willingness to try these products was lower. Consumers are still wary of GM and nanotechnology, possibly due to lack of assurance that these foods are safe for human health and the environment. For new food technologies (such as nanotechnology) that are still recent, communication is very important, being decisive for the consolidation of consumer perceptions, and consequently for the acceptance of these innovations on the market.
•This study was the first attempt to use the FTNS in a Portuguese speaking country.•It provides interesting data for effective implementation of food technology neophobia scale.•Food technology neophobia was influenced by socioeconomic factors.•It was possible to determine the relationship between neophobia and nanotechnology.
One of the major challenges for obtaining asymmetric membranes has been the preparation of ceramic supports with tailored pore structures. The methods commonly used for processing these materials do ...not allow a fine control of the support structure, which may decrease their mass transport capacity. As a consequence, freeze-casting is a promising technique for obtaining supports with tailored pore structures and permeation behaviors. This work deals with the preparation of freeze-cast alumina macroporous supports. Different freezing routes and alumina powders were used in this study. It was correlated the effect of these parameters on the pore structure and permeation capacity of the obtained supports. It was shown that the isotropic layer observed at the samples bottom side plays a key role in their non-Darcian permeability. As far as we know, this is the first time that this approach is reported in the literature for freeze-cast samples.
Freeze-casting is a promising technique for fabricating macroporous ceramics because it is an environmentally friendly, cost effective, and easy scale-up method. Several freezing vehicles have been ...used in freeze-casting, including water, camphene, tert-butyl alcohol, urea, and naphthalene-camphor (Naph-Camp). This work focuses on the preparation of freeze-cast alumina samples using different Naph-Camp compositions as freezing vehicle, alumina loading ranging from 20 to 40 vol% and various freezing conditions. It was observed that macroporous materials with different pore structures and mechanical behaviors can be obtained by changing the Naph-Camp solvent composition. Moreover, the freezing route also showed a great effect on these properties, besides allowing the preparation of samples with oriented pores. These are important findings because naphthalene and camphor are widely available, have low toxicity, and show an easier sublimation than water, which has been commonly used as the freezing vehicle in many works. The range of pore structures and mechanical strengths obtained in this study demonstrates the versatility of the processing route used herein, which could be used to obtain samples for several applications, including catalysis, fluids filtration, and bioengineering. This study is supported by a series of experimental characterizations, including optical microscopy, scanning electron microscopy, Archimedes measurements, and cold crushing tests.
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•Successful preparation of tubular alumina membranes for treating sugarcane vinasse.•Samples prepared by the co-use of the slip-casting and dip-coating techniques.•Slip-cast supports ...coated with α- and γ-alumina films.•Decrease in color, turbidity and chemical oxygen demand of vinasse after permeation.•The membranes showed a regeneration capacity after a chemical cleaning procedure.
In this work asymmetric tubular membranes were successfully prepared by the co-use of the slip casting and dip-coating techniques. These membranes were used for treating a sugarcane vinasse sample obtained in ethanol production. This study is supported by a series of experimental tests, including scanning electron microscopy, mercury intrusion porosimetry, and Archimedes tests. Parameters such as color, turbidity and chemical oxygen demand (COD) of vinasse were taken into consideration for evaluating the performance of the membranes prepared herein. On one hand, it was observed that a slip-cast support prepared in this study exhibited an expressive capacity for separating the solid particles present in vinasse from water. On the other hand, the deposition of a boehmite coating on this sample led to a further increase in the membrane performance. Reductions as high as 31, 98 and 89% for COD, turbidity and color were obtained when vinasse was permeated through an asymmetric membrane prepared in this study.
In this work we fabricated alumina samples by the freeze-casting technique using tert-butanol as the solvent. The prepared materials were examined by scanning electron microscopy and X-ray ...microtomography. Next, they were coated with sol–gel silica films by dip-coating. Permeability tests were carried out in order to assess the permeation behavior of the materials processed in this study. We observed that the sintering time and alumina loading showed a remarkable effect on both the structural properties and flexural strength of the freeze-cast samples. Nitrogen adsorption tests revealed that the silica prepared in this study exhibited a microporous structure. It was observed that the presence of silica coatings on the alumina surface decreased the CO2 permeance by about one order of magnitude. Because of the similar kinetic diameters of nitrogen and carbon dioxide, the CO2/N2 system showed a separation efficiency that was lower than that observed for the He/CO2 and He/N2 systems. We noticed that increasing the feed pressure improved the separation capacity of the obtained materials.
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•Porous alumina samples obtained by the freeze-casting technique•Microporous silica coating prepared by a simple sol–gel dip-coating methodology•Samples examined by SEM, μ-CT, and nitrogen sorption tests•Mechanical tests were carried out in the freeze-cast samples.•The presence of silica coatings on the alumina surface decreased the CO2 permeance.
This study has been focused on obtaining fungal laccases and structural modification of lignin by enzymatic action in laccase-ABTS system, mainly reducing molecular stiffness. The best specific ...aeration rate in bubble column reactor is 0.67 vvm, with 3260 U/L laccase activity, and enzymatic activity increased by 60% in stirred tank reactor. Enzymatic cocktail has been concentrated in a hollow fiber system and partially characterized. Laccase-ABTS system promoted significant thermal and structural changes in Kraft lignin in all essayed reaction times (2, 24, 48, and 72 h). The best reaction time of the enzymatic treatment is LT-lac48, which promoted the highest relaxation coefficient (18.0%). The enzymatic cocktail produced herein is efficient for structural modification of Kraft lignin. The positive evidence of lignin’s relaxation/flexibility and its linearization and homogenization suggests that treatment performed may adjust studied lignin to produce high-performance lignin suitable for many applications.
Agribusiness has a great relevance in the world׳s economy. It generates a considerable impact in the gross national product of several nations. Hence, it is the major driver of many national ...economies. Nowadays, from each new planting to harvesting process it is mandatory and crucial to apply some kind of technology to optimize a given singular process, or even the entire cropping chain. For instance, digital image analysis joined with machine learning methods can be applied to obtain and guarantee a higher quality of the harvest, leading to not only a greater profit for producers, but also better products with lower cost to the final consumers. Thus, to provide this possibility this work describes a visual feature dataset from soybean seed images obtained from the tetrazolium test. This is a test capable to define how healthy a given seed is (e.g. how much the plant will produce, or if it is resistant to inclement weather, among others). To answer these questions we proposed this dataset which is the cornerstone to provide an effective classification of the soybean seed vigor (i.e. an extremely tiresome human visual inspection process). Besides, as one of the most prominent international commodity, the soybean production must follow rigid quality control process to be part of world trade. Hence, small mistakes in the seed vigor definition of a given seed lot can lead to huge losses.
In this work we successfully obtained slip-cast alumina supports with tubular shape. It was investigated the influence of both the starting powder particle size and heat treatment program on the pore ...structure and water permeability of the prepared materials. This study is supported by a series of experimental tests, including Archimedes method, mercury intrusion porosimetry, scanning electron microscopy, and cold crushing tests. We observed that the heat treatment temperature exhibited a more significant effect on the porosity than the sintering time. It was noticed that, in a general way, the higher the sintering temperature, the smaller the porosity and the larger the apparent density of the prepared materials. In addition, the raise of the sintering temperature from 1100 to 1500°C increased the cold crushing strength of the tested samples. This behavior was not observed for F2, which seems to be related to the poor sinterability of the starting alumina powder used in its preparation. Among the samples prepared in this work, F2 showed the highest water permeability, followed by F3 and F1. The water permeation behavior of these materials is discussed on the basis of their mean pore size, porosity, genus per unit volume, and pore network tortuosity.
β,β-Disubstituted-1,3-dinitro compounds were obtained exclusively with an overall yield of 83% through a domino nitroaldol/elimination/1,4-addition process, when excess nitromethane was added to ...cyclohexanone or butanone using DBU (1,8-diazabicyclo5.4.0undec-7-ene), as a basic catalyst. On the other hand, β-nitroalcohols could be obtained in 30-84% yield, when nitromethane reacts with different aliphatic ketones in stoichiometric amounts, in the presence of catalytic amounts of K2CO3(s), Amberlyst®-A21 or TBAF.3H2O (tetra-n-butylammonium fluoride trihydrate)/THF (tetrahydrofuran). In addition, a new and versatile route to obtainment of allylic nitro compounds, by treatment of acetylated nitroalcohols and aldehydes in catalytic amounts of DBU or TBAF.3H2O, via a one-pot elimination/nitroaldol reaction sequence, was developed.
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