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Showing papers in "Brazilian Journal of Chemical Engineering in 2011"


Journal ArticleDOI
TL;DR: The experimental conditions were optimized for the synthesis of amorphous SiO2 particles by the reaction of neutralization of sodium silicate solution with H2SO4 solution as discussed by the authors.
Abstract: The experimental conditions were optimized for the synthesis of amorphous SiO2 particles by the reaction of neutralization of sodium silicate solution with H2SO4 solution Amorphous SiO2 particles were characterized by XRD, FT-IR, FE-SEM, EDS and microelectrophoresis The amorphous peak was located at 2θ = 218o in the XRD pattern Primary SiO2 particles were ~ 15 to ~ 30 nm in size and they aggregated into bigger particles Amorphous SiO2 particles showed a specific surface area up to 130 m2g-1, dependent on the parameters of the precipitation process The EDS spectrum of amorphous SiO2 particles did not show contamination with sulfate or other ions, which cannot be excluded in traces pHzpc =17 was obtained by microelectrophoresis

462 citations


Journal ArticleDOI
TL;DR: In this article, a simple pyrolysis reactor system was used to produce high-density polyethylene (HDPE) plastic as the material for pyrolyses, with the objective of optimizing the liquid product yield at a temperature range of 400oC to 550oC.
Abstract: Thermal degradation of waste plastics in an inert atmosphere has been regarded as a productive method, because this process can convert waste plastics into hydrocarbons that can be used either as fuels or as a source of chemicals. In this work, waste high-density polyethylene (HDPE) plastic was chosen as the material for pyrolysis. A simple pyrolysis reactor system has been used to pyrolyse waste HDPE with the objective of optimizing the liquid product yield at a temperature range of 400oC to 550oC. Results of pyrolysis experiments showed that, at a temperature of 450oC and below, the major product of the pyrolysis was oily liquid which became a viscous liquid or waxy solid at temperatures above 475oC. The yield of the liquid fraction obtained increased with the residence time for waste HDPE. The liquid fractions obtained were analyzed for composition using FTIR and GC-MS. The physical properties of the pyrolytic oil show the presence of a mixture of different fuel fractions such as gasoline, kerosene and diesel in the oil.

212 citations


Journal ArticleDOI
TL;DR: In this work, chitosan nanoparticles and nanofibers used to encapsulate bioactive substances and immobilize enzymes were reviewed and some problems encountered with nano - structured chitan carriers for bioactive substance encapsulation and enzyme immobilization were discussed.
Abstract: Encapsulation and immobilization technology is important for the food processing and bioengineering industries. Chitosan is a natural polysaccharide prepared by the N - deacetylation of chitin. It has been widely used in food and bioengineering industries, including the encapsulation of active food ingredients, in enzyme immobilization, and as a carrier for controlled drug delivery, due to its significant biological and chemical properties such as biodegradability, biocompatibility, bioactivity, and polycationicity. In this work, chitosan nanoparticles and nanofibers used to encapsulate bioactive substances and immobilize enzymes were reviewed. Preparation of chitosan nanoparticles and nanofibers, including the work achieved in our group on chitosan nanoparticles for enzyme immobilization, were also introduced. Some problems encountered with nano - structured chitosan carriers for bioactive substance encapsulation and enzyme immobilization were discussed, together with the future prospects of such systems.

209 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of chitosan on the adaption of FD&C Red n°40 food dye was investigated using the batch method, from 298 to 338 K. The results showed that the adsorption process is exothermic, spontaneous, and favorable.
Abstract: Chitosan is a natural polymer that has been employed in dye adsorption. In this work, adsorption and thermodynamic data for the interaction of FD&C Red n° 40 food dye with chitosan in aqueous solutions were investigated. The equilibrium adsorption isotherms were determined by the batch method, from 298 to 338 K. Adsorption data were adjusted to five isotherm models: Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich, in order to determine which presented the best adjustment to the experimental data. Error analysis showed that the Langmuir isotherm model was the most appropriate for fitting the experimental data, with a maximum monolayer adsorption of 3065.8 µmol g-1 at 308 K. Negative enthalpy (-112.7 kJ mol-1), entropy (-0.338 kJ mol-1 K-1) and Gibbs free energy (-15.6 to 1.0 kJ mol-1) values demonstrated that the adsorption process is exothermic, spontaneous, favorable, and that randomness of the system decreases during the adsorption process.

205 citations


Journal ArticleDOI
TL;DR: The extraction using ultrasonic bath in the presence of glass pearls in the biomass proved to be the most efficient method, 56% higher than using freezing and thawing (the method most frequently used), and presented a extraction yield of 43.75 mg.g-1.
Abstract: C-Phycocyanin is a natural blue dye used in food and pharmaceutical industry. In the present study, a simple and efficient method to extract C-phycocyanin from Spirulina platensis wet biomass is reported. The extractions were carried out using six different methods, including chemical (organic and inorganic acid treatment), physical (freezing and thawing, sonication, homogenization) and enzymatic (lysozyme treatment) methods. The extraction using ultrasonic bath in the presence of glass pearls in the biomass proved to be the most efficient method, 56% higher than using freezing and thawing (the method most frequently used), and presented a extraction yield of 43.75 mg.g-1 and a C-phycocyanin concentration of 0.21 mg.mL-1.

126 citations


Journal ArticleDOI
TL;DR: In this article, the fixed-bed adsorption of carbon dioxide and a carbon dioxide-nitrogen mixture on zeolite 13X was investigated and the breakthrough curves were determined at different temperatures - 301-306 K, 323 K, 373 K and 423 K.
Abstract: In this study, the fixed-bed adsorption of carbon dioxide and a carbon dioxide-nitrogen mixture on zeolite 13X was investigated. The adsorption equilibrium and breakthrough curves were determined at different temperatures - 301-306 K, 323 K, 373 K and 423 K. A model based on the LDF approximation for the mass transfer, considering the energy and momentum balances, was used to describe the adsorption kinetics of carbon dioxide and a carbon dioxide-nitrogen mixture. The model acceptably reproduced all of the breakthrough curves and can be considered as adequate for designing a PSA cycle to separate carbon dioxide- nitrogen mixtures.

95 citations


Journal ArticleDOI
TL;DR: In this paper, a study on the heterogeneous Fenton reaction using hematite powder (Fe2O3) in suspension for the discolouration of the reactive dye Drimarene Red X-6BN in aqueous solutions is presented.
Abstract: This work reports a study on the heterogeneous Fenton reaction using hematite powder (Fe2O3) in suspension for the discolouration of the reactive dye Drimarene Red X-6BN in aqueous solutions. The efficiency of the process was studied as a function of the experimental conditions: initial pH; H2O2 dose; and hematite powder concentration; all of which showed a strong effect on the reaction kinetics. Under the best experimental conditions: pH = 2.5; H2O2 dose = 800 mg/L; and [Hematite] = 20 g/L, it was possible to remove about 99% of the initial colour in 120 minutes in a batch reaction at 25oC. The analysis of the kinetic results suggests that the reaction is initiated by heterogeneous generation of free radicals on the hematite surface, but as soluble iron (III) and iron (II) species are released into the solution during the course of the reaction, a simultaneous homogeneous Fenton reaction step propagates and contributes to the overall reaction.

74 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used supercritical carbon dioxide to extract citronella essential oil, and the results were modeled using a predictive way, reproducing the extraction curves over the maximum time of the process.
Abstract: Citronella essential oil has more than eighty components, of which the most important ones are citronellal, geranial and limonene. They are present at high concentrations in the oil and are responsible for the repellent properties of the oil. The oil was extracted using supercritical carbon dioxide due to the high selectivity of the solvent. The operational conditions studied varied from 313.15 to 353.15 K for the temperature and the applied pressures were 6.2, 10.0, 15.0 and 180.0 MPa. Better values of efficiency of the extracted oil were obtained at higher pressure conditions. At constant temperature, the amount of extracted oil increased when the pressure increased, but the opposite occurred when the temperature increased at constant pressure. The composition of the essential oil was complex, although there were several main components in the oil and some waxes were presented in the extracted oils above 10.0 MPa. The results were modeled using a mathematical model in a predictive way, reproducing the extraction curves over the maximum time of the process.

59 citations


Journal ArticleDOI
TL;DR: In this article, the reduction in surface tension of Bacillus subtilis MTCC 2423 was studied in submerged batch cultivation using waste frying oils, which facilitates safe disposal of waste frying oil, as well as reducing the production cost of surfactin.
Abstract: - One of the obstacles in the way of wide scale industrial application of biosurfactants is the high production cost coupled with a low production rate. In order to lower the production cost surfactin production by Bacillus subtilis MTCC 2423 was studied in submerged batch cultivation using waste frying oils. It was observed that the decrease in surface tension was 56.32%, 48.5% and 46.1% with glucose, waste frying sunflower oil and waste frying rice bran oil, respectively. Biomass formation was 4.36 g/L, 3.67 g/L and 4.67 g/L for glucose, waste frying sunflower oil and waste frying rice bran oil, respectively. Product yield (g product/g substrate) was 2.1%, 1.49% and 1.1% with glucose, waste frying sunflower oil and waste frying rice bran oil as substrates. This process facilitates safe disposal of waste frying oil, as well reducing the production cost of surfactin. Keywords : Biosurfactants; Bacillus subtilis ; Surface Tension; Waste frying oils; Secondary metabolite.

55 citations


Journal ArticleDOI
TL;DR: In this article, a Plackett-Burman experimental design was used to evaluate seven medium components added to molasses (corn steep liquor, sodium acetate, magnesium sulfate, manganese sulfate and ammonium citrate, potassium phosphate and Tween 80).
Abstract: A Plackett-Burman experimental design was used to evaluate seven medium components added to molasses (corn steep liquor, sodium acetate, magnesium sulfate, manganese sulfate, ammonium citrate, potassium phosphate and Tween 80). Corn steep liquor (CSL), K2HPO4 and Tween 80 increased lactic acid production. The concentrations of these three components as well as the molasses were further optimized using the response surface method. A maximal lactic acid production of 94.8 g L-1 was obtained when the concentrations of molasses, CSL, K2HPO4 and Tween 80 were 193.50 g L-1, 37.50 mL L-1, 2.65 g L-1 and 0.83 mL L-1, respectively. However, in both shaker and bioreactor, approximately one fourth of the sugar added initially was not utilized after 48 hours of fermentation. Future studies that consider high conversion of sugar into final product as well as high volumetric productivity are necessary to improve the fermentation process and to reduce the downstream costs.

53 citations


Journal ArticleDOI
TL;DR: In this paper, starch enzymatic hydrolysis was investigated using commercial α-amylase and glucoamylases, considering particle size, solid:liquid ratio and enzyme load as variables.
Abstract: The production of ethanol from sorghum grains was investigated in the present work. Initially, starch enzymatic hydrolysis was investigated using commercial α-amylase and glucoamylase, considering particle size, solid:liquid ratio and enzyme load as variables. The hydrolysate, in the best conditions (73 U of α-amylase/g grain and 1150 U glucoamylase/g grain), contained glucose at a concentration of approximately 250 g/L, which was fermented to produce ethanol in a bioreactor in batch mode. Using an industrial strain of Saccharomyces cerevisiae, the maximum ethanol concentration produced was roughly 106 g.L-1 in 24 h of fermentation, resulting in a volumetric productivity of 4.4 g.L-1.h-1 and a product yield based on the substrate consumed (0.499 g.g-1) close to the theoretical.

Journal ArticleDOI
TL;DR: The ethanol production by Pichia stipitis was evaluated in a stirred tank bioreactor using semi- defined medium containing xylose (90.0 g/l) as the main carbon source and results are promising and contribute to the development of a suitable process for ethanol production fromxylose by Pchia stipitas.
Abstract: The ethanol production by Pichia stipitis was evaluated in a stirred tank bioreactor using semi- defined medium containing xylose (90.0 g/l) as the main carbon source. Experimental assays were performed according to a 2 2 full factorial design to evaluate the influence of aeration (0.25 to 0.75 vvm) and agitation (150 to 250 rpm) conditions on ethanol production. In the studied range of values, the agitation increase and aeration decrease favored ethanol production, which was maximum (26.7 g/l) using 250 rpm and 0.25 vvm, conditions that gave a volumetric oxygen transfer coefficient (kLa value) of 4.9 h -1 . Under these conditions, the ethanol yield factor, ethanol productivity, and the process efficiency were 0.32 g/g, 0.32 g/l.h, and 63%, respectively. These results are promising and contribute to the development of a suitable process for ethanol production from xylose by Pichia stipitis.

Journal ArticleDOI
TL;DR: This work reviews recent trends in the modeling of cellulose hydrolysis, within the perspective of application of kinetic models in a bioreactor engineering framework, including scale-up, design and process optimization.
Abstract: This work reviews recent trends in the modeling of cellulose hydrolysis, within the perspective of application of kinetic models in a bioreactor engineering framework, including scale-up, design and process optimization. From this point of view, despite the phenomenological insight that mechanistic models can provide, the expectation that more detailed approaches could be a basis for extrapolations to different substrates and/or enzymatic pools is still not fulfilled. The complexity of the lignocellulosic matrix, the different mechanisms of catalytic action, the role of mass transfer limitations and the deviations from ideal mixing are important difficulties for the modeler, which will continue to impose more conservative approaches for scale-up. Nevertheless, the search for more robust models is a very important task, provided that the engineer is aware of their limitations. Data-driven, non-mechanistic models such as artificial neural networks, perhaps in combination with other approaches in the so-called hybrid models, is also a promising alternative.

Journal ArticleDOI
TL;DR: In this paper, a multi-layer perception neural network was used to estimate the thermal efficiency and resistance of a closed thermosyphon during application of a magnetic field and using nanoparticles in the water as the working fluid.
Abstract: Heat transfer of a silver/water nanofluid in a two-phase closed thermosyphon that is thermally enhanced by magnetic field has been predicted by an optimized artificial Neural Network. Artificial neural network is a technique with flexible mathematical structure that is capable of identifying complex non-linear relationships between input and output data. A multi-layer perception neural network was used to estimate the thermal efficiency and resistance of a thermosyphon during application of a magnetic field and using nanoparticles in the water as the working fluid. The magnetic field strength, volume fraction of nanofluid in water and inlet power were used as input parameters and the thermal efficiency and thermal resistance were used as output parameters. The results were compared with experimental data and it was found that the thermal efficiency and resistance estimated by the multi-layer perception neural network are accurate. The GA-ANN (Genetic Algorithm-Artificial Neural network) predicts the thermosyphon behavior correctly within the given range of the training data. In this study, a new approach for the auto-design of neural networks, based on a genetic algorithm, has been used to predict collection output of a closed thermosyphon.

Journal ArticleDOI
TL;DR: In this article, an investigation was carried out on the synthesis of titanium dioxide nanopowders via the hydrothermal method, examining the influence of temperature (150oC and 200oC) and reaction time (6 to 36 h).
Abstract: An investigation was carried out on the synthesis of titanium dioxide nanopowders via the hydrothermal method, examining the influence of temperature (150oC and 200oC) and reaction time (6 to 36 h). The resulting powders were characterized by X-ray diffraction, infrared absorption spectrophotometry, transmission electron micrographs and surface area. The X-ray diffraction revealed that there was formation of a pure crystalline phase, consisting only of anatase for all conditions of synthesis. Both temperature and reaction time proved to have a slight influence on the crystallite size (from 9 to 17 nm) and a significant influence on the surface area (from 86 to 168 m2.g-1).

Journal ArticleDOI
TL;DR: In this article, two bentonite clays with different mineralogical compositions from Mendoza, Argentine, were activated with H2SO4 solutions of 4 and 8 N at 90oC for 3.5 hours.
Abstract: Two bentonite clays with different mineralogical compositions from Mendoza, Argentine, were activated with H2SO4 solutions of 4 and 8 N at 90oC for 3.5 hours. This treatment affected clay structural properties, as was shown by thermogravimetry, infrared spectrometry and chemical analysis. Bleaching efficiency for sunflower oil was strongly dependent on the acid concentration used for clay activation. The samples have bleaching capacity comparable to that observed with a commercial adsorbent standard. The mineralogical composition of natural clays influenced the properties of the activated clays.

Journal ArticleDOI
TL;DR: In this article, a 76 mm diameter pulsed disc and doughnut extraction column for the toluene-acetone-water system is presented, where the axial diffusion model is interpreted in terms of axial dispersion and the effect of operating parameters on the overall volumetric mass transfer coefficients is investigated.
Abstract: Mass transfer performance is presented for a 76 mm diameter pulsed disc and doughnut extraction column for the toluene-acetone-water system. The experiments were carried out for both mass transfer directions. The mass transfer data are interpreted in terms of the axial diffusion model, thus accounting for continuous phase axial dispersion. The effect of operating parameters on the overall volumetric mass transfer coefficients has been investigated. The results show that the column performance increases with an increase in pulsation intensity. At high pulsation intensity, however, the overall volumetric mass transfer coefficient decreases due to the production of very fine dispersed droplets. It was also found that the column performance decreases with both an increase in dispersed phase velocity and a decrease in continuous phase velocity. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is derived in terms of the overall Sherwood number, Reynolds number and dispersed phase holdup for each mass transfer direction. The prediction of continuous phase overall mass transfer coefficients from the presented correlations is in good agreement with experimental data.

Journal ArticleDOI
TL;DR: In this article, diesel-based microemulsions and a surfactant/diesel blend, using ethoxylated (5 EO) nonylphenol as surfactants, were prepared and tested in a diesel engine to evaluate its performance and emissions.
Abstract: - Diesel-based microemulsions and a surfactant/diesel blend, using ethoxylated (5 EO) nonylphenol as surfactant, were prepared and tested in a diesel engine to evaluate its performance and emissions. The following properties were evaluated: density, viscosity, cloud point and corrosiveness. Experimental results showed that density and viscosity were greater than those obtained for neat diesel. Cloud point and corrosiveness were not affected by water and surfactant. Specific fuel consumption of the microemulsion systems was greater than that of diesel, but the small droplets of water improved diesel combustion. Compared with diesel, an increase in carbon monoxide (CO) and nitrogen oxide (NOx) emissions and a decrease in black smoke emissions were obtained. In general, only microemulsions with up to 6% water are in accord with Brazilian diesel/biodiesel fuel regulations and specifications. Keywords : Diesel; Diesel engine; Surfactant; Microemulsion; Emissions. INTRODUCTION Diesel oil is a fossil fuel used in compression ignition engines. Combustion of diesel fuel contributes greatly to environmental pollution due to carbon monoxide, nitrogen oxides and particulate matter emissions to the atmosphere. The necessity of reducing gas emissions and the search for better engine performance have increased the interest in alternative fuels or emulsion/microemulson systems, such as: blends of diesel with biodiesel and vegetable oils, diesel-based microemulsions, natural gas/diesel blends, and water-in-oil emulsions (Crookes

Journal ArticleDOI
TL;DR: In this article, a 76 mm diameter pulsed disc and doughnut extraction column for three different liquid-liquid systems was investigated and the effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on holdup was found to be significant.
Abstract: Dispersed phase holdup has been measured in a 76 mm diameter pulsed disc and doughnut extraction column for three different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on holdup have been investigated and found to be significant. The existence of three different operational regimes, namely mixer-settler, dispersion, and emulsion regimes, was observed when the energy input was changed. The results indicated that the characteristic velocity approach is applicable to this type of extraction column for analysis of holdup in the transition and emulsion regions. Empirical correlations are derived for prediction of the dispersed phase holdup in terms of the physical properties of the system and the operating variables in different operating regimes. Good agreement between prediction and experiments was found for all operating conditions investigated.

Journal ArticleDOI
TL;DR: The thermal stability, as well as stability over a wide range of pH, was significantly improved by the immobilization process and the immobilized enzyme was able to retain 84 % of the initial catalytic activity after 5.0 cycles.
Abstract: - Aspergillus aculeatus tannase was immobilized on several carriers by entrapment and covalent binding with cross-linking. Tannase immobilized on gelatin with cross-linking agent showed the highest activity and immobilization yield. The optimum pH of the immobilized enzyme was shifted to a more acidic range compared with the free enzyme (from pH 5.5 to pH 5.0). The optimum temperature of the reaction was determined to be 50°C for the free enzyme and 60°C for the immobilized form. The thermal stability, as well as stability over a wide range of pH, was significantly improved by the immobilization process. The calculated K m of the immobilized tannase (11.8 mg ml -1 ) is higher than that of the free tannase (6.5 mg ml -1 ), while V max of the immobilized enzyme (0.32 U (µg protein) -1 ) is lower than that of the free tannase ( 2.7 U (µg protein) -1 ). The immobilized enzyme was able to retain 84 % of the initial catalytic activity after 5.0 cycles. Keywords : Tannase; Enzyme immobilization; SSF, Green tea (

Journal ArticleDOI
TL;DR: In this paper, xanthan and guar gum [0.3, 0.7 and 1.0% (w/w)] were added to yellow passion fruit pulp and the changes in the dynamic and steady - shear rheological behavior evaluated.
Abstract: Yellow passion fruit pulp is unstable, presenting phase separation that can be avoided by the addition of hydrocolloids. For this purpose, xanthan and guar gum [0.3, 0.7 and 1.0% (w/w)] were added to yellow passion fruit pulp and the changes in the dynamic and steady - shear rheological behavior evaluated. Xanthan dispersions showed a more pronounced pseudoplasticity and the presence of yield stress, which was not observed in the guar gum dispersions. Cross model fitting to flow curves showed that the xanthan suspensions also had higher zero shear viscosity than the guar suspensions, and, for both gums, an increase in temperature led to lower values for this parameter. The gums showed different behavior as a function of temperature in the range of 5 - 35oC. The activation energy of the apparent viscosity was dependent on the shear rate and gum concentration for guar, whereas for xanthan these values only varied with the concentration. The mechanical spectra were well described by the generalized Maxwell model and the xanthan dispersions showed a more elastic character than the guar dispersions, with higher values for the relaxation time. Xanthan was characterized as a weak gel, while guar presented a concentrated solution behavior. The simultaneous evaluation of temperature and concentration showed a stronger influence of the polysaccharide concentration on the apparent viscosity and the G' and G" moduli than the variation in temperature.

Journal ArticleDOI
TL;DR: In this article, the influence of chromium from tanning, deacidification pH, fatliquors, chrome retanning and vegetable re-anning on the formation of Cr(VI) in leather was analyzed by comparing natural and aged samples.
Abstract: Chromium used in leather manufacturing can be oxidized from the trivalent to the hexavalent state, causing environmental concerns. In this study, the influence of Cr(III) from tanning, deacidification pH, fatliquors, chrome retanning and vegetable retanning on the formation of Cr(VI) in leather was analyzed by comparing natural and aged samples. In wet-blue leather, even after aging and in fatliquored leathers that did not suffer the aging process, the presence of Cr(VI) was always below the detection limit of 3 mg/kg. Considering the presence of Cr(VI), the supply of chromium during the retanning step had a more significant effect than during the tanning. In the fatliquoring process with sulfites, fish and synthetic fatliquor leather samples contained Cr(VI) when aged, and the highest concentration detected was 26.7 mg/kg. The evaluation of Cr(VI) formation led to recommendations for regulation in the leather industry.

Journal ArticleDOI
TL;DR: The removal efficiency of organic matter and how it relates to the decrease of toxic and mutagenic effects when an anaerobic reactor is used to treat the bleaching effluent from two kraft pulp mills indicate that these effluents are recalcitrant but not toxic.
Abstract: This study assessed the removal efficiency of organic matter and how it relates to the decrease of toxic and mutagenic effects when an anaerobic reactor is used to treat the bleaching effluent from two kraft pulp mills. Parameters such as COD (chemical oxygen demand), DOC (dissolved organic carbon), AOX (adsorbable organic halogen), ASL (acid soluble lignin), color, chlorides, total phenols and absorbance values in the UV-VIS spectral region were measured. The acute and chronic toxicity and genetic toxicity assessments were performed with Daphnia similis, Ceriodaphnia sp. and Allium cepa L, respectively. The removal efficiency of organic matter measured as COD, ranged from 45% to 55%, while AOX removal ranged from 40% to 45%. The acute toxic and chronic effects, as well as the cytotoxic, genotoxic and mutagenic effects, decrease as the biodegradable fraction of the organics is removed. These results, together with the organic load measurement of the effluents of the anaerobic treatment, indicate that these effluents are recalcitrant but not toxic. As expected, color increased when the anaerobic treatment was applied. However, the colored compounds are of microbial origin and do not cause an increase in genotoxic effects. To discharge the wastewater, it is necessary to apply a physico-chemical or aerobic biological post-treatment to the effluents of the anaerobic reactor.

Journal ArticleDOI
TL;DR: In this article, supercritical fluid extraction was used to obtain volatile and non-volatile compounds from the aerial parts of Schinus molle L. and the influence of the process on the composition of the extracts.
Abstract: Schinus molle L., also known as pepper tree, has been reported to have antimicrobial, antifungal, anti-inflammatory, antispasmodic, antipyretic, antitumoural and cicatrizing properties. This work studies supercritical fluid extraction (SFE) to obtain volatile and non-volatile compounds from the aerial parts of Schinus molle L. and the influence of the process on the composition of the extracts. Experiments were performed in a pilot-scale extractor with a capacity of 1 L at pressures of 9, 10, 12, 15 and 20 MPa at 323.15 K. The volatile compounds were obtained by CO2 supercritical extraction with moderate pressure (9 MPa), whereas the non-volatile compounds were extracted at higher pressure (12 to 20 MPa). The analysis of the essential oil was carried out by GC-MS and the main compounds identified were sabinene, limonene, D-germacrene, bicyclogermacrene, and spathulenol. For the non-volatile extracts, the total phenolic content was determined by the Folin-Ciocalteau method. Moreover, one of the goals of this study was to compare the experimental data with the simulated yields predicted by a mathematical model based on mass transfer. The model used requires three adjustable parameters to predict the experimental extraction yield curves.

Journal ArticleDOI
TL;DR: In this paper, a study of five commercial enzymes used commercially in tanneries to assess their ability to act upon collagen and keratin and to determine their unhairing was conducted.
Abstract: - The enzymatic treatment of hides in tannery processes is a promising technology. However, the reaction kinetics of commercial enzymes available to the leather industry are not fully understood and their activities have been mainly determined with model proteins such as casein as substrate, which are not of direct relevance for cattle hides. Therefore, it is important to determine their activities on collagen and keratin, the main proteins of skin, in order to use these enzymes in leather processing. This work describes the study of five proteases, used commercially in tanneries, to assess their ability to act upon collagen and keratin and to determine their unhairing. Results showed that all commercial enzymes tested had more activity on collagen than on keratin. Unhairing was also tested and four out of the five enzymes tested showed some unhairing activity. Optima of the temperature and pH of the enzymes were very similar for all five enzymes, with maximal activities around 55°C and pH 9 to 12, respectively.

Journal ArticleDOI
TL;DR: The thermal stability of the extracellular fructosyltransferase (FTase) from Rhodotorula sp.
Abstract: The thermal stability of the extracellular fructosyltransferase (FTase) from Rhodotorula sp., recovered from cultivation medium by ethanol precipitation and immobilized onto niobium ore, was studied by Arrhenius plot, half - life profile, half - inactivation temperature (T50) and thermodynamic parameters. The Arrhenius plot showed two different behaviors with different deactivation energies (Ead) only after immobilization, the transition occurring in the temperature interval between 51 and 52oC. T50 for the free enzyme was estimated to be around 62oC and, after immobilization, 66oC. After 15 minutes at 52oC, it was also possible to observe enzymatic activation for both the free and immobilized forms, but greater activation was achieved at pH 4.5 with the immobilized enzyme. Between 47 - 51oC the immobilized enzyme was more stable than the free enzyme, with pH 6.0 being the more stable condition for the immobilized enzyme. However, above 52oC the free form was more stable.

Journal ArticleDOI
TL;DR: In this article, the authors evaluate the technical and economic feasibility of a new and potential proposal at the national level, the generation of electricity and heat, through a cogeneration system using glycerol.
Abstract: Glycerol is an important by-product of biodiesel production. It is used in many industrial segments, but the increasing production of this chemical has become an issue of concern. Many studies have been done to give new applicability to this product; a promising field is the usage of glycerol for energy production. Therefore, this study evaluates the technical and economic feasibility of a new and potential proposal at the national level, the generation of electricity and heat, through a cogeneration system using glycerol. The results demonstrate the viability of this proposal, since the payback on capital invested obtained was approximately 4 years, with the possibility of reduction to 3 years when installed in regions with low infrastructure.

Journal ArticleDOI
TL;DR: In this article, the residual esterification activity and the product conversion after 10 successive cycles of utilization of a commercial lipase in three systems were investigated, and the results showed that after 10 cycles the enzyme retained 90% of its activity.
Abstract: The main focus of this work was to investigate the residual esterification activity and the product conversion after 10 successive cycles of utilization of a commercial lipase in three systems: esterification of 2-ethyl hexanol and palmitic acid in a solvent-free system; esterification of ascorbic acid and palmitic acid in tert-butanol; and transesterification of glycerol and methyl benzoate in 2-propanol. These systems were chosen based on previous results by our research group in terms of product conversion. Before scale-up, there is a need for evaluating several cycles of utilization of the biocatalyst. The esterification of 2-ethyl hexanol showed that after 10 cycles the enzyme retained 90% of its activity. The system consisting of ascorbic acid, palmitic acid, Novozym 435 and tert-butanol showed that a reduction in enzyme activity was accompanied by a reduction in reaction conversion; the same behavior was not observed for the third system.

Journal ArticleDOI
TL;DR: In this article, a neural network model was used to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin-and-flat tube (WFFT) heat exchangers.
Abstract: A three dimensional (3D) computational fluid dynamics (CFD) simulation and a neural network model are presented to estimate the behaviors of the Colburn factor (j) and the Fanning friction factor (f) for wavy fin - and - flat tube (WFFT) heat exchangers. Effects of the five geometrical factors of fin pitch, fin height, fin length, fin thickness, and wavy amplitude are investigated over a wide range of Reynolds number (600

Journal ArticleDOI
TL;DR: In this article, the influence of different carbazole concentrations on cell growth, degradation and the formation of anthranilic acid (an intermediate in the carbazoles degradation pathway) was assessed.
Abstract: The proportion of nitrogenated compounds such as carbazole in heavy fractions of crude oil is higher in Brazil than in other parts of the world. The degradation of this compound by microorganisms has already been described for bacteria such as Pseudomonas stutzeri ATCC 31258. Assays were undertaken to assess the influence of different carbazole concentrations on cell growth, carbazole degradation and the formation of anthranilic acid (an intermediate in the carbazole degradation pathway). The results indicated that there was an accumulation of anthranilic acid in the medium with the higher concentration of substrate (10 g/L), which could be related to the inhibition of Pseudomonas stutzeri growth in an excess of carbazole. With 1 g/L of carbazole, growth was found to be ten times greater (0.37 g dry cell weight/L) and there was no accumulation of anthranilic acid (formation of around 7 mg/L), with complete carbazole degradation after three days.