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ABSTRACT The functionalization of graphene nanosheets is the cutting edge of materials sciences nowadays. Such research promotes the development of innovative, low cost and highly capable sorbents. This review article aims to assemble the available information on functionalized graphene used for the adsorption of organic pollutants and establishes a critical comparison between the data reported in the literature. Various optimal experimental conditions (pH, temperature, contact time, adsorbent dosage) and adsorbent characterization methods (FTIR, Raman, XPS spectra, XRD, TEM and AFM) have been listed to enlighten adsorption mechanisms, capacity and limiting aspects. Moreover, adsorption isotherms, kinetics and thermodynamic data of different functionalized graphene-based materials towards a wide range of organic pollutants were analyzed and tabulated. In each evaluation topic, environmental and human health protection is subject for discussion, as well as the scientific breakthrough works available in high impact journals in the field.

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ABSTRACT Sweet potato is an attractive feedstock for ethanol production due to its high starch content and favorable agronomic characteristics. This paper proposes a simple equation to estimate the total reducing sugars (including glucose from starch) in sweet potatoes based on their moisture content (low cost and simple measurement). It allows the calculation of the ethanol production potential of a given sweet potato mash. According to the equation, the ethanol potential increases non-linearly with increasing concentrations of sweet potato mash in the fermenting medium (w/v), reaching a constant value for high concentrations (22 % of ethanol to 10 kg: L of a sweet potato with a moisture content of 66 %). Additionally, the ethanol yield potential is very sensitive to the sweet potato moisture, increasing linearly when the moisture decreases. We emphasize that the relations proposed in this paper can be used by other researchers, who can apply them to their specific cases.

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ABSTRACT Elephant grass (Pennisetum purpureum Schumach) is regarded as a promising feedstock for second generation ethanol production, due to its high cellulose content, biomass production and rapid growth. The yeast Kluyveromyces marxianus CCT 7735 is capable of producing ethanol from agroindustrial residues, such as lignocellulosic biomass. Therefore, this study aimed to establish the optimal conditions for ethanol production by K. marxianus CCT 7735 from elephant grass. Five factors were evaluated: temperature (35-45 ºC), pH (4.5-5.8), agitation (50-150 rpm), cellulase concentration (7.5-22.5 FPU/mL) and elephant grass biomass (8-16% w/v). Enzymatic concentration (22.5 FPU/mL), biomass concentration (16% w/v) and temperature (38 ºC) were the significant optimized factors. K. marxianus CCT 7735 produced a high ethanol concentration (around 45.5 g/L) under these optimized conditions, which is considered feasible in terms of energy requirements in the distillation step.

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ABSTRACT Biorefineries based on microalgae produce biofuels and co-products with added value. Microalgae mainly require water, carbon dioxide and sunlight for growth. The bioproducts of the cultivation of these microorganisms can be fully used in a microalgae photobiorefinery. The objective of this work was to study the behavior of physico-chemical variables and kinetic and biological responses in industrial cultivation of Spirulina sp. LEB 18, aiming at the operation of a microalgal photobiorefinery. The maximum specific growth rate (0.133 1/d), the minimum generation time (5.2 d) and maximum productivity (14.9 g/m².d) were obtained in the first 9 d of microalgae growth. The maximum biomass concentration (1.64 g/L) was obtained in 37 d of cultivation. The highest levels of carbohydrates, proteins and lipids in the biomass were 10.6, 57.0 and 11.7%, respectively. The plant monitoring demonstrated that the microalgae produced biomass with high quality for application as biofuels, energy, health and nutrition human.

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ABSTRACT Water contamination by monoaromatic compounds has risen throughout time, which leads to the necessity of developing new water treatment technology, capable of minimizing their negative effect on the environment. In this context, biological processes present themselves as a solution to the processes of extraction. Bioremediation makes use of microbial groups capable of using hydrocarbons as a source of carbon to perform their metabolic functions. This work evaluated the biodegradation efficiency of Pseudomonas aeruginosa strain isolated from contaminated matrices, for the substrates benzene, ethylbenzene and toluene, aiming to determine to which compound the bacteria had better adaptation. For that, bioremediation assays were performed for each of the monoaromatic compounds, in an isolated way, with the goal of obtaining experimental data and from this Monod and Andrews kinetic models were discretized and numerically developed through the Runge-Kutta method. It was possible to observe that Pseudomonas aeruginosa has a bigger affinity for ethylbenzene, while benzene generated a bigger microbian coefficient. Monod´s model was capable of predicting satisfactorily the experimental data.

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ABSTRACT Polyhydroxyalkanoates (PHA) are biocompatible and biodegradable polyesters produced by prokaryotic microbes for energy storage and carbon reserve. These polymers are an option to diminish the massive impact caused by inadequate disposal of synthetic plastics. In this study, evaluation and characterization of PHA produced by Cupriavidus necator (IPT 026 and IPT 027) and Burkholderia cepacia (IPT 119 and IPT 400), using soybean as substrate, were carried out (soybean 15 g L-1, pH 7.0, 150 rpm, 72 hours). The highest polymer production was achieved using IPT 027 (0.84 ± 0.07 g L-1). All PHA produced showed the characteristic bands of polyester functional groups in the FTIR spectra. Polymers synthesized by Cupriavidus necator exhibited initial temperatures of degradation superior to 300oC and higher molecular weights than the ones produced by Burkholderia cepacia, which in turn, exhibited lower crystallinity (inferior to 30%), revealing high influence of the microorganism strain on PHA properties and production.

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ABSTRACT In order to overcome the bottlenecks related to lignocellulosic-derived sugars, the search for more efficient enzymatic cocktails, containing a broad-spectrum of specific activities, relies on an important feature. This paper describes new enzyme activities derived from the novel strain of the Scytalidium genus isolated from the Amazonas rainforest. The production of the enzymatic cocktail was induced by delignified-hydrothermal bagasse (DHB), and yeast extract was used to improve secretion activities, resulting in a positive influence on total cellulase activity. The enzymatic cocktail produced by this novel strain contains specific activities for biomass degradation, including FPAse, xylanase and β-glucosidase. Moreover, it is capable of hydrolyzing 62% of the alkaline pretreated bagasse, surpassing in 14% the hydrolytic capability achieved by the commercial cocktail Celluclast. To this extent, the strain described here emerges as a reliable alternative to other available enzymes and, consequently, amplification of available specific substrate activities.

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This study aims to assess a new approach for concomitant valorization of two industrial wastes - raw glycerin and spent brewer’s yeast - for the bioproduction of valuable carotenoids. Microbial pigments have numerous applications in the food and cosmetic industries. First, four cultures of yeasts were screened using pure glycerol and either (NH4)2SO4 or urea as carbon and nitrogen sources, respectively. The ability of the best performing culture to accumulate carotenoids was investigated in a medium in which only wastes were supplemented as carbon and nitrogen sources. All the fermentations were carried out in 500 mL-Erlenmeyer flasks containing 150 mL of the medium. Microbial culture was incubated at 30 °C and 150 rpm for 120 h. Particularly, R. marina was the strain with the biggest potential to produce total carotenoids (up to 420 μg g-1). The four major carotenoid pigments identified by LCAPCI-MS were β-carotene, γ-carotene, torulene, and torularhodin. All fermentation assays and all the determinations were performed in triplicate. Results show that the bioprocess proposed in this work is technically and environmentally feasible, and sustainable. The simultaneous use of raw glycerin and spent brewer’s yeast for the production of carotenoids by R. marina is reported for the first time.

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ABSTRACT Re-engineering of chemical materials at the nanoscale level that employ modification and improvement in their physical and chemical properties has been constantly pursued for application in biomedical and biotechnology industries. Moreover, immobilization of catalysts on these bio/chemically modified nanomaterials improved the performance of enzymes in a plethora of industrial uses. Hence, in this study, cerium oxide nanoparticles (CNPs) were synthesized and their morphology was investigated by TEM and UV-spectra. They were modified by carboxylation and glutaraldehyde to achieve highly efficient surface functionalized nanomatrices for immobilizing Aspergillus oryzae β-galactosidase for producing lactose-free products in dairy industries. Enzyme activity for soluble and immobilized enzyme was observed in different pH and temperature ranges, and on galactose mediated competitive inhibition offered by the substrate. It was observed that all the enzyme preparations exhibited temperature-optima at 50 °C and pH-optima at pH 4.5, respectively. Michaelis-Menten Km (mmole/L) values were 2.40, 5.88, 6.02 and 6.11 for soluble β-galactosidase, and enzyme immobilized on CNPs, carboxylated CNPs and glutaraldehyde modified CNPs, respectively. However, Vmax (mmole/L/min) was found to be 518, 507, 495 and 480 for these enzyme preparations under identical conditions. Immobilized enzyme demonstrated excellent reusability even after seven repeat uses. The bioconversion rates of lactose from solution in continuous batch reactors revealed the remarkable catalytic efficiency of β-galactosidase immobilized on glutaraldehyde modified CNPs in comparison to other enzyme preparations.

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ABSTRACT Different yeast strains from forests located in southern Brazil, with potential to produce carotenoids, were isolated. Three microorganisms were selected as potential carotenoid producers. Sporiodiobolus pararoseus, Rhodotorula mucilaginosa and Pichia fermentans were grown in Yeast Malt (YM) medium and the carotenoids produced identified as cryptoxanthin and β-carotene. In order to reduce production costs, agroindustrial residues were used in the formulation of medium A (parboiled rice water and crude glycerol) and medium B (parboiled rice water and sugar cane molasses). The highest carotenoid production was obtained with S. pararoseus. It reached 905.30 μ gL-1 (122.82 μg g-1) in YM medium, 820 μg L-1 (68.04 μg g-1) in medium B and 710 μg L-1 (86.46 μg g-1) in medium A. R. mucilaginosa exhibited the best performance in medium B (360 μg L-1 and 30.16 μg g-1) and a new microorganism - P. fermentans - reached 48% (medium A) and 78% (medium B) of the value found in YM medium. Therefore, the agroindustrial residues under evaluation, which replaced the commonly used nitrogen and carbon sources in culture media, enabled the isolated yeasts to yield carotenoids.

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ABSTRACT This research evaluated the effect of different delignification pretreatments (enzymatic and organosolv), on the crystallinity and enzymatic hydrolysis of harvested sugar cane residues. The Crystallinity Index (CrI), the Relative Number of Intensity (Ir), the degree of cellulose mercerization (IIC-%), and the Global Index of Saccharification (GIS) were used as measurement parameters for six different substrates obtained from sugar cane residues (tops and leaves) by different processes. In this characterization, the spectroscopic ty Techniques of Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction and scanning eElectron microscopy (SEM) were used. Substrates to which only organosolv pretreatment was applied, without any further treatment, presented good behavior for the enzymatic hydrolysis and a high CrI, possibly due to the increase of the crystallinity by elimination of amorphous material.

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ABSTRACT This study aimed to determine the best dilute acid hydrolysis condition for the hemicellulosic fraction of sweet sorghum bagasse for ethanol production by Scheffersomyces stipitis. The experiment followed a 23 factorial design with four central points, and had as variables: sulfuric acid concentration, temperature and hydrolysis time. Sorghum bagasse presented the following chemical composition: 24.77% of lignin, 31.28% of hemicellulose and 34.80% of cellulose. The hydrolysis that resulted in the highest sugars concentration (14.22 g/L of xylose and 2.42 g/L glucose) was 1.75% H2SO4, 121 ºC and 40 minutes. This same condition provided low concentrations of toxic compounds (1.34 g/L of acetic acid, 0.90 g/L of phenol; 124.54 mg/L of hydroxymethylfurfural (HMF) and 978 mg/L of furfural). The fermentation of the hemicellulose-derived sugars by S. stiptis resulted in 22 g/L of ethanol, YP/S 0.40 g/g and Qp 0.34 g/L.h.

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ABSTRACT Yeast strains were isolated from sugar cane molasses (S1), dates (S2) and figs (S3) and the ethanol production was evaluated in batch condition. A comparison was made with the yeast Saccharomyces cerevisiae. The strains showed tolerant characteristics to stressful conditions like salinity and ethanol. The isolated strains produced ethanol; at 20 h of fermentation ethanol yields were 0.38-0.39 g.g-1, and the productivities were almost 0.58 g.L-1. S. cerevisiae and S1 tolerated up to 14% (v/v) of ethanol; while interestingly the isolates S2 and S3 were highly tolerant, up to 20% (v/v) ethanol. Thus, S2 and S3 could serve as potential strains for ethanol fermentation, with 0.27 and 0.29 g.g-1 yield of ethanol in the presence of 1.37 mol.L-1NaCl. These values were higher than the value obtained using the yeast of reference and S1 (0.16 g.g-1). Co-cultures of S2 and S3 enhanced the ethanol production, increasing the yield of ethanol by 12.5% compared with the single culture. The strains were identified as species S.cerevisiae, and S2 and S3 were very similar. For an application in the valorization of biomass such as green macro-algae, some assays were done on a synthetic model medium of hydrolysate of macro-algae and the strains S2 and S3 demonstrated excellent fermentative performances.

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ABSTRACT Nanomaterial-based biocatalysts have emerged as current carriers suitable for enzyme immobilization. The nano-sized materials provide large surface area for enzyme attachment, thus increasing the probability for its efficient catalyst activity. By using magnetized nanomaterials, enhancement of the downstream processing is evident as it eases the immobilized enzyme separation from the reaction mixture further. Lipase / maghemite composites were prepared by initial maghemite surface modification to cater to the needs for biocatalyst attachment. Surface modification using chitosan and subsequent cross-linking with glutaraldehyde provide a suitable environment for the enzyme to be immobilized. Optimization of the conditions for lipase immobilization was carried out using a response surface methodology (RSM) experimental design to obtain the precise optimized conditions for the process. Selected process variables involved were chosen and optimized conditions for lipase immobilization were 9 hour incubation time, 55°C incubation temperature and 12 % (v/v) glutaraldehyde content. The optimized immobilized lipase activity was 1.8 U. Characterizations of the on synthesized materials were also performed. The size distribution of maghemite nanomaterials was mainly within the range of 2-3 nm. Thermal properties of the synthesized maghemite was investigated using DSC and TGA analyses and we found that maghemite changes to hematite at 456.3°C. Magnetic properties of both untreated and lipase immobilized maghemite were studied using VSM and both were superparamagnetic nanomaterials with saturation magnetizations of 34.3 and 80.3, respectively.

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ABSTRACT Immobilizing the photocatalyst on a support is an alternative solution to a critical issue in photocatalysis, which is the need for unit operations to remove the photocatalyst from the effluent. In this work, TiO2 was immobilized onto a cotton textile substrate by polycarboxylic acid binders (succinic and citric acids) using a solution deposition method, and the most appropriate conditions for pre-treatment and the relationship between variables were determined by an experimental design. Then, samples prepared at optimum conditions were exposed to UV for an extended period of time to evaluate the deactivation. The results showed an increase in photocatalytic activity and deposited mass by raising curing temperature, a statistically significant variable for tested binders. However, the increase in photocatalyst mass deposition is not always followed by an increase in photocatalytic activity, indicating that the photocatalyst distribution on the substrate is also important for photocatalytic efficiency. Both binders formed UV light active materials with sufficient displacement strength for photocatalysis use.

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ABSTRACT Kinetic studies of sulfentrazone herbicide dechlorination by Fe/Ni nanoparticles were performed in the presence of different electrolytes such as: Cl-, SO42-, NO3-, Cu2+, Na+ and Zn2+. In the presence of Cl- and SO42- the reaction occurred efficiently, reaching approximately 100% of dechlorination after 30 minutes of reaction. In the presence of NO3- and Cu2+ ions the sulfentrazone dechlorination was significantly inhibited, because these ions tend to compete with the substrate for the electrons donated by Fe0. In the presence of Na+ ions, the dechlorination efficiency remained approximately 100%, however, this electrolyte provided an increase on the reaction rate, due to the increase of the ionic strength in the system. The Zn2+ ions has no influence on the dechlorination efficiency, but the reaction rate was reduced due to the formation of a protective layer formed by the sorption of Zn2+ ions on the surface of the nanoparticles.

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ABSTRACT Three different bismuth catalysts (Bi2WO6, BiOI and BiVO4) were synthesized using solvo- and hydrothermal methods. Different reaction times, calcination and the addition of poly (vinyl pyrrolidone) during synthesis were tested to investigate the effect of these variables on the catalysts’ morphology and photocatalytic activity. The photocatalytic activity was evaluated using the degradation of rhodamine B dye under both visible light and natural solar radiation. The Bi2WO6 samples presented good crystallinity and morphological similarities, despite having undergone different treatments. The BiOI and Bi2WO6 catalysts presented a spherical shape, and no morphological difference was observed as a result of the addition of PVP. The BiVO4 sample presented a parallelepiped shape. BiOI containing PVP and ethylene glycol was the catalyst that presented the highest activity, while BiVO4 presented the lowest. In experiments using scavengers, photogenerated holes demonstrated a key role in dye degradation.

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ABSTRACT N2O emissions from wastewater treatment plants have become an important issue, since this compound is a significant greenhouse gas that affects the sustainability of sewage treatment. This work aimed to investigate and to reduce N2O emission from a pilot-scale aerobic granular sludge sequencing batch reactor (AGS-SBR) operated for carbon and nitrogen removal from domestic wastewater under subtropical climate condition. Three operational strategies (S-I, S-II and S-III) with different anoxic phase durations were compared regarding treatment efficiency and N2O emission. For all the studied strategies, volatile suspended solids (VSS) was between 1.0 and 1.2 g/L. S-III, with the longest anoxic phase, obtained the highest biological oxygen demand (BOD) and NH4+-N removal efficiencies (86% and 84%, respectively), the lowest N2O emission factor (16.99 gN2O-N/person·year) and the lowest total nitrogen (TN) to N2O conversion ratio (0.47%). The results indicated that the extension of the anoxic phase was an effective way to significantly reduce N2O emission and to improve treatment efficiency.

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ABSTRACT The design and process of heat transfer elements, from its source to heat sink through various media vary according to the product and system concerned. The effect of thickness of a steel plate on heat transfer characteristics with an impinging air jet at the stagnation point was studied. Experiments were carried out with different nozzles, heights, and velocities. It was concluded that the heat transfer increases with the increase in velocity and the increase in Reynolds Number, but decreases with the increase in nozzle height from the impinging point. A maximum stagnation Nusselt number of 309.06 was obtained at the optimum conditions with a plate thickness of 3 mm. The new empirical correlations calculated from the experiments were in reasonable agreement with the equations in the literature and the deviation was less than 15%.

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ABSTRACT The rheological behavior of an aqueous suspension of silver nanoparticles stabilized with aminosilane-based surfactant flowing under confinement was investigated. Three stability levels were defined based on the zeta potential: high (41.73 mV, pH 4.3), medium (10.44 mV, pH 7.4), and low (0.74 mV, pH 8.6). Furthermore, the preliminary investigation showed that the surface charge remained positive, and the formation of agglomerates was not observed. Due to the particle coating and the ionization of the amino groups of the surfactant an electrosteric stabilization was evidenced. Shear rates ranging from 50 to 1000 s-1 and shear stresses between 0.02 and 0.2 Pa, at the temperatures of 15, 25 and 35 ºC, were evaluated with the nanofluid flowing in microchannels with a gap of 100, 300 and 500 µm. A trend to dilatant behavior was observed at high shear rate and a slit size of 500 µm, while Newtonian behavior was predominant at lower slit sizes. A reduction of 47.3% was noticed at 25 ºC with the variation in the slit size from 500 to 300 µm. Furthermore, the viscosity of the nanofluid decreased as much as 60% when the slit size was reduced from 500 to 100 µm.

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ABSTRACT One of the highlighted areas in the development of new materials is the generation of micro- and nanoparticles as drug carriers which allow the progress in formulations with the ability to release active agents in a controlled way. The proanthocyanidins (PAC) extracted from the bark of the Black Wattle have stood out for their biological activities. However, most polyflavonoids have some features which limit their application in the pharmaceutical field, such as light fastness, low bioavailability of active agents, and unpleasant taste. In this context, this study aims to present the synthesis and characterization of PAC-loaded lactic-co-glycolic acid (PLGA) microparticles obtained by the multiple emulsion method. The incorporation of PAC into PLGA was successfully achieved with PAC encapsulation efficiency around 73%. Spherical microparticles were obtained with a size distribution in the range of 0.6 to 2.4 μm. The presence of PAC modified the thermal properties of the PLGA matrix. The results of in vitro assays with Vero and T24 lineage celss showed that PLGA/PAC microparticles did not promote any effect on cell proliferation by MTT assay after 24 h. The novel Acacia mearnsii proanthocyanidin-loaded PLGA microparticles have potential for application in biological systems.

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ABSTRACT Herein, the influence of pure and modified polyvinyl chloride (PVC) support layers on the performance of thin-film composite (TFC) membranes was investigated in water desalination. Accordingly, the PVC support was modified using (3-Aminopropyl) triethoxysilane (APTES) through bulk modification. The supports were synthesized at different doses of APTES (0-6 wt%) and characterized with various analytical techniques. The results showed that APTES affected considerably both the morphology and surface properties of the support layer. Afterwards, the polyamide (PA) layer was formed via an identical interfacial polymerization (IP). The separation experiments showed that modification of the support improved the performance of the TFC membranes, which stems from the improvement in the degree of cross-linking of the PVC structure. At an appropriate condition, permeate fluxes were 0.89 L.m-2.h-1.bar-1 and 2.70 L.m-2.h-1.bar-1for TFC membranes with pure and modified PVC support layers, respectively. Interestingly, there were no significant changes in salt rejection of the prepared membranes.

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ABSTRACT Reducing sulfur and nitrogen compounds is essential in producing clean fuels for providing a green environment. In this regard, a novel nanocatalyst has been proposed for Hydrodesulfurization (HDS) and Hydrodenitrogenation (HDN) of heavy naphtha. To this end, Ni-Mo was loaded on nanoporous graphene (Ni-Mo/NG) through the incipient wetness impregnation method. The synthesized nanocatalyst was characterized by FE-SEM, ICP, BET, FTIR, XRD and TPR methods. The catalytic activity of the Ni-Mo/NG catalyst was evaluated at 290ºC and 30 bar. For the synthesized Ni-Mo/NG catalyst, conversions of total sulfur, total nitrogen and R-SH compounds (mercaptans) were obtained as 99.5, 99.4 and 99.3%, respectively, which shows considerable enhancement in comparison to the Ni-Mo/γ-Alumina industrial catalyst.

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ABSTRACT Different basic materials, such as K-L zeolite, K-Al2O3, K-Mg/Al mixed oxide and MgO, were used as supports of Pt-catalysts for the dry reforming of methane (DR) reaction. The effects of the distribution of basic strength in the support on the metal-support properties and catalyst performance were evaluated. The density of strong and the total basic sites decreased as follows: MgO>K(Mg-Al) >K-Al2O3>K-L. The total basic sites decrease from 214 to 23 µmol CO2. g-1, for MgO and KL, respectively. Pt catalysts supported on materials with high density of strong basic sites such as MgO were the most adequate for the DR reaction. An increase in the dehydrogenation velocity of 12.1 to 25.2 mol h-1 g-1 was observed between Pt/KL and Pt/MgO, which indicates a higher metallic dispersion of the latter catalyst. With respect to the DR reaction, both catalysts have a similar CO2 conversion, but the CH4 conversion and the H2/CO ratio increase from 71.1 to 83.0 % and 0.5 to 0.73, respectively. The best catalytic behaviour of Pt/MgO would be related with the good interaction between the metal and the basic support. The methane conversion and the H2/CO ratios obtained by DR reaction correlate quite well with the basicity of the different catalysts.

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ABSTRACT This work studies the synthesis of fatty acid methyl esters (FAME) using crude olive pomace oil as raw material and zinc stearate as catalyst. Pomace oil is a non-edible by-product of olive oil production. The oil was characterized. In order to reduce the plant pigment content in the oil, the liquid was contacted with a modified clay. An experimental design was applied to determine the optimum operating conditions to achieve the minimum pigment concentration and the maximum amount of recovered oil. Response surface methodology was used to study the relationship between process variables and the selected response variables. A mixed-level factorial design was used, and the studied responses were triglyceride and free fatty acid (FFA) conversion and FAME yield at 30 min of reaction time. Under optimum conditions (temperature (T): 140ºC, catalyst loading (C): 3 wt%, initial molar ratio of the reactants (MR): 30), 98% and 67% of triglyceride and FFA conversions were achieved, with 84% of FAME yield. This study shows that pomace oil can be used as a raw material for biodiesel production. At short reaction times and under moderate operating conditions, it was possible to convert triglycerides and fatty acids selectively toward FAME.

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ABSTRACT A semi-batch bubble reactor has been developed to produce fatty acid ethyl ester (biodiesel) by acid-catalyzed esterification of oleic acid with superheated ethanol vapor. In this paper, the effects of reaction temperature (110, 130 and 150°C), ethanol volumetric flow rate (1.35, 2.50 and 3.65 mL/min) and vapor bubble size on the reactor performance were evaluated. The results demonstrated that temperature and volumetric flow rate have significant effects on the chemical reaction, gas phase solubility and mass transfer limitations. In addition, the free fatty acid conversion velocity was increased by approximately 56% when a microporous stainless-steel tube was employed to generate and distribute the vapor bubbles inside the reactor, which allowed the process to reach 95% conversion in approximately 40 minutes for the operating temperature of 150°C and volumetric flow rate of 2.5 mL/min.

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ABSTRACT In this work the production of glucose via hydrolysis of cellobiose using sulfonated active carbons as catalysts was studied. Commercial carbons presenting different types of porous system (micropores and mesopores) have been treated with sulfuric acid at different temperatures, being characterized afterwards. Such carbons have been tested as catalysts in the reaction of cellobiose hydrolysis. The results indicated that the type and density of sulfonic sites are not the only parameters responsible for the activity of the catalysts. Indeed, the porosity of the catalysts also plays an important role in the determination of the catalyst activity.

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ABSTRACT Chemical engineering optimization represents a significant challenge due to the complexity of the mathematical models that are frequently required in this area. These models are normally associated with nonlinear equations that represent mass, energy, and momentum balances, which are submitted to physical, constitutive, environmental, and design limitations. The design of chemical systems is generally carried out by considering the model, the vector of design variables, and system parameters as deterministic values, i.e., small variations in these quantities do not affect the objective function. In this contribution, a new methodology based on a double loop iteration process to evaluate the influence of uncertainties on chemical engineering design is proposed. The inner optimization loop is used to find the solution associated with the highest probability value by using the so-called Inverse Reliability Analysis and the outer loop is the regular optimization loop used to determine the vector of design variables. For this aim, the Multi-Objective Optimization Water Cycle Algorithm is improved, adopting a mechanism of neighborhood exploration. For illustration purposes, the proposed methodology is applied to mathematical functions and to chemical engineering design. The obtained results demonstrate that the proposed strategy represents an interesting alternative to reliability design in chemical engineering.

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ABSTRACT This paper presents a numerical analysis of entropy generation in a two-dimensional rectangular channel where the inlet flow undergoes thermal decomposition resulting from a chemical reaction. The model considered viscosity and thermal conductivity to be dependent of temperature. Irreversibility due to mass transport was included in the entropy generation analysis. Relevant applications of this study are possible for the design of power generation systems and reactors. The effects of the Reynolds number, Schmidt number, and length of the heat source on thermal fluid dynamics, mass transfer, and irreversibility were also investigated. It was found that thermal decomposition increases at: a) low Reynolds numbers, b) low Schmidt numbers, and c) increased length of heat source. Additionally, overall entropy generation increased when Reynolds number and length of heat source were increased, although in all cases, overall irreversibility attains a minimum value at a specific Schmidt number.

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ABSTRACT Biodiesel appears to be a likely substitute to conventional diesel. However, the main challenge has been the creation of a competitive advantage for the biodiesel production process in terms of innovation and efficiency. The reactive distillation technique for biodiesel production is possibly a key force to overcome this technological issue because it combines chemical reaction and the separation process inside the same unit. This work presents kinetic data for biodiesel production via the ethylic route and compare them with the methylic one. It also compares experimental results in a 1.5m reactive distillation pilot plant with simulated ones in ASPEN PLUS for ethylic biodiesel production with a molar ratio 6/1 (alcohol/oil). Kinetic parameters obtained for the ethylic study were ko = 8173dm3/(mol.min) and Ea =27.48 kJ/mol. Indeed, at the bottom of a six stage column overall the ethylic and methylic biodiesel accounted for 60.1% and 67.8%, respectively. Following this, a sensitivity analysis considering 20 stages of equilibrium showed an ester conversion above 97%. The total energy required to produce biodiesel via a conventional batch reactor was 1210W/h for the ethylic route and 2430 W/h for methylic one, while it amounted to approximately 1000W/h for both routes in the reactive distillation process.

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ABSTRACT The performances of the Standard κ-ε, RNG, Realizable, κ-ω and RSM turbulence models to describe the behavior of the flow in agitated tank reactors were evaluated. Because most of these tanks have complex geometries, structured meshing schemes are not a practical alternative in engineering. Two particular unstructured meshing schemes composed of either Cartesian Cut-Cell (CC) or Tetrahedral elements were tested in domains larger than 3 million cells. In this work, the blade thickness, which is usually disregarded, was accounted for. The performance of the turbulence models was validated by PIV measurements. A strong dependence on the grid size and the power number was found, with CC grids having good agreement with grids > 3.6 Million. The pumping number was independent of the cell number and the values agree with experimental data. The Realizable model resolved with a tetrahedral grid presented the overall best performance.

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ABSTRACT Computational modeling has been proven to be very useful in tissue engineering over the past years. Because the model is a simplification of the experimental system, the processes accounted for in the model should be analyzed carefully. However, new and complex models are usually proposed without a clear comparison with the basic ones. In this study, the contribution of oxygen to Contois growth kinetics and porosity variation with time due to polymer degradation was evaluated through a sensitivity analysis. The effect of initial glucose concentration, porosity and thickness of the scaffold on the cell volume fraction and substrate concentration was analyzed for three models. Even with the inclusion of oxygen concentration in the model, the output variables are more affected by the initial cell number, while the model with variable porosity is quite robust to variations in the input variables.

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ABSTRACT Operational KPIs play an extremely important role in the process industry, aiding in decision making. However, they need to be reliably calculated to be representative. The present work presents a schematic methodology for the calculation of these KPIs, including techniques of steady-state detection, denoising, error propagation and sensitivity analysis, presented, as far as it is known, in the form of a new graphical tool proposed by the authors named StatSSCandlePlot. The methodology was applied in a real case study of a gas fired boiler in which the indicator studied was its efficiency evaluated by the Stack Loss Method. From the StatSSCandlePlot it was possible to identify the trends of the indicator, the portion of each window in the steady-state, the values to be considered from the indicator and, in a complementary way, to identify the variable that most influences the variation of the indicator, through the sensitivity analysis.

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ABSTRACT Y-rank can present faults when dealing with non-linear problems. A methodology is proposed to improve the selection of data in situations where y-rank is fragile. The proposed alternative, called k-rank, consists of splitting the data set into clusters using the k-means algorithm, and then apply y-rank to the generated clusters. Models were calibrated and tested with subsets split by y-rank and k-rank. For the Heating Tank case study, in 59% of the simulations, models calibrated with k-rank subsets achieved better results. For the Propylene / Propane Separation Unit case, when dealing with a small number of sample points, the y-rank models had errors almost three times higher than the k-rank models for the test subset, meaning that the fitted model could not deal properly with new unseen data. The proposed methodology was successful in splitting the data, especially in cases with a limited amount of samples.

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ABSTRACT In this paper a controller is proposed based on linear algebra for a fed-batch bioethanol production process. It involves finding feed rate profiles (control actions obtained as a solution of a linear equations system) in order to make the system follow predefined concentration profiles. A neural network states estimation is designed in order to know those variables that cannot be measured. The controller is tuned using a Monte Carlo experiment for which a cost function that penalizes tracking errors is defined. Moreover, several tests (adding parametric uncertainty and perturbations in the control action) are carried out so as to evaluate the controller performance. A comparison with another controller is made. The demonstration of the error convergence, as well as the stability analysis of the neural network, are included.

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ABSTRACT There is a continual desire around the world to reduce the sulphur content of diesel fuel to ultra-low levels (below 10 ppm) due to environmental concerns and the intention of improving air quality and lowering harmful exhaust emissions of diesel engines. In this work, a hydrodesulfurization unit fed with multiple diesel streams was addressed using a phenomenological mathematical model aiming to produce Ultra-Low Sulfur Diesel (ULSD). A three-phase model of a trickle-bed reactor was considered. A model-based predictive control strategy (MPC) was implemented with the objective of controlling the sulfur concentration at the exit of the reactor, manipulating the flow rates of the oils entering the system, the superficial velocity of the gas and the temperature of the load in the presence of disturbances in the concentration of organic sulfur compounds in the fed oils. It was observed that the control strategy reduced the contaminant content to the specification range of diesel S10.

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ABSTRACT The present study addresses the novel application of the simulated annealing algorithm (SAA) to optimize the pressure-swing distillation (PSD) process for anhydrous ethanol purification. Three different softwares (Aspen Plus®, Excel® and Matlab®) were integrated to simultaneously optimize seven design and operational variables. The configuration with the best TAC represented a 40.2% saving per year in comparison to the non-optimized PSD. Such reduction was achieved by using the higher acceptance probability and the slower temperature decrement. This saving is mainly related to operational cost reductions, a fact that evidences the viability of using the herein described optimization methodology to improve the PSD design.

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ABSTRACT The startup operation of distillation columns is one of the most complex steps performed in the industry. This complexity becomes even greater for thermally coupled extractive distillation systems. Thermally coupled configurations are commonly used in order to minimize the excessive amount of energy required to perform distillation. In view of this, this study aimed to develop a startup procedure for the thermally coupled extractive distillation system to obtain anhydrous ethanol by simulation using the computational package Aspen Plus Dynamics. From the startup procedure developed, the complex dynamic behavior of the system under study was analyzed (strong interaction between variables). Large variations in the stripping section of the extractive column were observed, resulting from the variation of the molar density of the liquid mixture in addition to the delay in the startup operation when the amount of ethanol in the recovery column increases.

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ABSTRACT Extracts from the leaves of Psidium guajava L have been studied due to their importance as a source of natural antioxidant components with possible applications in the pharmaceutical and food industries. In this work, the sequential use of steam distillation and supercritical fluid extraction was studied to obtain the essential oil from the leaves and non-volatile compounds from the residue. The non-volatile compounds were obtained by CO2 supercritical extraction. Experiments were performed in a automated pilot-scale extractor at constant pressure of 15 MPa, at 313 K and 333 K in three different flow rate conditions. The analysis of the essential oil with GC-MS identified E-caryophyllene, β-selinene1, α-selinene, selin-11-en-4-α-ol and E-nerolidol as main compounds. Antioxidant activity was observed in all extracts. The experimental extraction curves were compared to simulated ones predicted by a mathematical model based on mass transfer principles with two adjustable parameters. The model used fitted accurately the experimental data.

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ABSTRACT Polyvinylchloride (PVC) based membranes are prepared via a phase inversion method using N,N-dimethylacetamide (DMAc) as solvent and water as precipitation bath. Polyvinylpyrrolidone (PVP) and lithium nitrate (LiNO3) are used as additives. Experimental cloud point data and solution viscosity measurements are evaluated. Precipitation rates, transport properties and membrane morphology are quantified. Membranes with different morphologies and transport properties are prepared by changing the additive and its concentration, changing the PVC concentration and by varying the exposure time to the environment before immersion. An augment in PVC concentration increases solution viscosity, reduces precipitation rate and water permeability (Jw), but it does not affect the instantaneous precipitation mechanism. PVC solutions with additives present higher viscosity values, slower light transmittance decay and membranes with higher Jw (highest: ~1,350 L.h-1.m-2.bar-1). LiNO3 in the polymeric solution results in delayed demixing. A combination of high PVP concentration and environment exposure time changes the membrane morphology, suggesting spinodal demixing.

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ABSTRACT Aqueous amine solutions are benchmark solvents for CO2 capture and their operational drawbacks are well-known. In order to overcome these problems, the support of amines on solid materials appears as an option for CO2 capture. Cellulose is a versatile and low-cost material that can be used as a support. This study reports chemical modification of cellulose fibers extracted from rice husk with different amines and their potential for CO2 capture. The obtained compounds were characterized by different techniques. The CO2 sorption capacity was gravimetrically assessed in a Magnetic Suspension Balance. Quantum mechanical simulations and experimental results revealed that -NH- and -NH2 represent major working sites of the employed compounds. The best result for CO2 sorption was attained for the amine-modified cellulose CL-D-400 with a sorption capacity of 409 µmol CO2/g at 1 bar and 1091 µmol CO2/g at 10 bar with amine concentrations as low as 2 × 10- 6 mol/mg.

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ABSTRACT In this research, sol-gel precipitation using CO2 impregnation and mechanical fragmentation method was applied to produce precipitated silica from Palm Oil Mill Fly Ash (POMFA). Carbon dioxide (CO2) was used in order to reduce the cost of the process and to enable sodium hydroxide recovery. The precipitation process was done in a stirred temperature-controlled baffled glass precipitator. The response surface method with the central composite design was applied to optimize the stirring speed and the CO2 flow rate. The pH and the temperature of the precipitation process were varied for tailoring the specific surface area of the precipitated silica. The mechanical fragmentation and wet crushing process were applied to control the agglomerate particle size of the precipitated silica obtained. The results show that precipitated silica with a specific surface area in the range of 50 - 140 m2/g can be obtained.

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ABSTRACT In this work the applicability of a natural volcanic glass (technological type I material) from Cuba is investigated as adsorbent for separation of mixtures of C1-(C5; C6; C7; C8; C9) hydrocarbons by inverse gas chromatography under flow conditions in a temperature range of 328-343 K. The experimental results indicated that the material was mainly composed of silica and, in a lower proportion, of alumina, that provided surface Si-OH and Al-OH groups to favor the interaction and separation of the different components of paraffin mixtures. In fact, the calculated heats of adsorption were high enough to facilitate the separation procedure. The high availability and low cost of these materials make them potential and attractive candidates to be used in large scale applications.

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ABSTRACT The present study assessed the competing behavior between metals and extractants applied to the solvent extraction of calcium and/or nickel present in sulfuric solutions using the extractants Cyanex 272 (bis-2,4,4-trimethylpentyl phosphinic acid) and/or D2EHPA (di-2-ethylhexyl phosphoric acid). Tests were designed to allow equivalent competing conditions between metals and extractants. Considering metal competition in the aqueous phase, calcium extraction remained unaffected in the presence of nickel, while nickel extraction curves with pH displaced to the right in the presence of calcium when D2EHPA (ΔpH1/2 = 1.4) or Cyanex 272 + D2EHPA (ΔpH1/2 = 0.9) were used. Considering extractant competition in the organic phase, metal extractions with Cyanex 272 + D2EHPA closely followed the curves obtained with D2EHPA, thus evidencing that it acts as the main extractant agent, synergism or antagonism effects being attributed to the presence of Cyanex 272. A synergistic increase in the calcium extraction occurred at pH ≥ 4.5, being unaffected in the presence of nickel, whereas rejection for nickel occurred in the whole pH range in the absence of calcium, and at pH < 5.5 in the presence of calcium. For the operating conditions investigated, Ca/Ni separation reached a maximum at pH = 4.5 (calcium extraction > 80%, nickel extraction < 0.25%, βCa/Ni = 2159).

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ABSTRACT Duguetia furfuracea (Annonaceae) is a shrub found in the Brazilian Cerrado that is used in popular medicine as an antirheumatic, for wound healing, treatment of kidney pain and against pediculosis. The aim of this study was to analyze the extraction of leaves of Duguetia furfuracea, using supercritical CO2, ethanol and hexane as solvents. For the supercritical extraction, an experimental planning 23 with triplicates of the central point was used to evaluate the effects of temperature (313-333 K), pressure (15-23 MPa) and volumetric flow rate (3-6 mL min-1) on the extraction yield, total phenolic content and antioxidant activity compared with extracts obtained by Soxhlet extraction. The effects of the variables on the extraction yield were positive and the pressure had greater influence. However, the highest performances, total phenolic content and antioxidant activities were obtained by the Soxhlet method. The mathematical model based on the Brunauer-Emmett-Teller theory of adsorption correlated satisfactorily the experimental values of the supercritical extraction.

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ABSTRACT Asphaltenes represent the heaviest fraction of crude oils, being recognized by their tendency to self-associate and precipitate. Asphaltene precipitation and subsequent deposition can cause problems in all stages of production. The objective of this paper is to model Brazilian crude oil and asphaltene systems using the PC-SAFT equation of state. Asphaltenes were extracted from crude oil through the addition of different n-alkanes. The PC-SAFT was capable of accurately predicting liquid density for toluene and asphaltenes and boiling point elevation for crude oil at different concentrations of toluene. Asphaltene precipitation from model oil allowed us to evaluate the influence of binary interaction parameters on modeling results. The influence of precipitant agent (n-hexane and n-heptane) on the asphaltene phase behavior was analyzed, showing that n-hexane was able to precipitate more asphaltenes than n-heptane, as expected. Furthermore, simulated results are in agreement with experimental observations: the average relative errors are 3.75 % and 10.25 % for the weight percentage of precipitated asphaltene using n-hexane and n-heptane as precipitant, respectively.

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ABSTRACT Bio-oil obtained from thermal cracking of waste cooking oil (WCO) is a complex mixture of different chemical compounds and, like crude oil, it is composed mainly of hydrocarbons. The large number of compounds in bio-oil leads to complex and expensive methods for its properties determination. In this study, the distillation curves were constructed for samples of bio-oils obtained from the thermal cracking of WCO in order to predict the properties (such as molecular weight, viscosity and refractive index). Although it is not often employed for bio-oil analyses, the distillation curve method is commonly used in the petroleum industry. Atmospheric and vacuum distillations were performed according to ASTM D86 and ASTM D1160 standards, respectively, for six samples of bio-oil and one sample of crude oil. The results were converted to true boiling point (ASTM D2892) according to the API method (1997) and common petroleum refining correlations were employed. The estimated values for the properties showed little deviation in relation to the experimental data. The bio-oil and crude oil samples contained heavy compounds in their composition, and all samples studied are considered as heavy oils considering the °API range.

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ABSTRACT In the present work, some numerical and computational aspects of COSMO-based activity coefficient models were explored. The residual contribution in such models rely on the so called self-consistency equation. This equation does not have a closed-form solution and is usually solved by the successive substitution method. The performance of a classical Newton-Raphson method was tested in solving the self-consistency equation. The results obtained by the Newton implementation and by successive substitution agreed within the convergence tolerance. The CPU times for solving the model using both methods also were compared. Contradicting the usual experience, it was observed that the Newton method becomes slower than successive substitution when the number of components (or number of COSMO segments) in the mixture increases. An analysis of the number of floating point operations required showed the same, Newton’s method will be faster only for small systems.

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ABSTRACT Aqueous systems composed of ionic liquid make up a new alternative for use in processes involving the separation of biomolecules. The objective of this experiment was to obtain the thermo-physical properties of density, refractive index, electrical conductivity, molar volume, thermal expansion coefficient and apparent specific volume of the ionic liquid 1-ethyl-3-methylimidazolium chloride. The thermo-physical properties of aqueous solutions of this ionic liquid were measured as a function of the mass fraction w = (0.05, 0.125, 0.2, 0.275 and 0.35), temperature T = (293.15, 303.15, 313.15 and 323.15) K and pH = (7.5, 8.0 and 8.5). Models representing the combined effects between variables were fit since they are required for industrial applications where the physical parameters must be accurately calculated. Models representing the combined effects of the variables temperature, mass fraction and pH values of ionic liquid were adjusted and presented good fit.

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ABSTRACT L-menthol is an essential oil produced from Mentha arvensis. An experimental L-menthol solid-liquid equilibrium in menthol oil constituents was determined in the temperature range between 271 K and 300 K, by the method of creating a saturated solution at a given temperature by using an excess of crystals in the suspension. The mole fraction of the experimental data, on a logarithmic basis, were fitted against T by the Apelblat equation and by a linear equation with good results. The equations were: ln(x) =#091;- 52.45 + 1,170.70/T + 8.48.ln(T) #093; and ln(x) = 3.98 -1,249.65/T with T in K. Both equations give a good correlation with the experimental data. From the Apelblat equation the enthalpy of solution was also calculated as a linear function of temperature and has an average value of 150.31 J/mol in the temperature interval studied.