Resumo em Inglês:

Abstract The fractioning into separate liquid and solid fractions obtained by centrifugation of thickened fresh and thermally pretreated (170 ºC, 50 minutes) secondary sludge showed that 30% of the particulate organic matter was released during the pretreatment, correspondingly increasing the methane production of the particulate matter by 30% (from 259 to 329 mL CH4/g VSfed). The responsible of this enhancement was the liquid fraction, as the biodegradability of the solid fraction remained constant after the pretreatment. Mass balances showed that 34% of the VS were released to the liquid fraction, generating nearly 50% of the total methane produced, with much faster kinetics compared to the solid fraction. These results support the hypothesis of a separate liquid-solid digestion of thermally pretreated sludge, which would result in decreasing the digestion volume to half while duplicating the methane productivity per kilogram of sludge fed to digestion.

Resumo em Inglês:

Abstract This work investigated the anaerobic degradation of the model azo dye Remazol Yellow Gold RNL in batch reactors using discharged residual yeast as the source of redox mediators (RM). Two yeast lysis methods (mechanical lysis and sonication) were tested and optimized to produce a riboflavin-rich yeast lysate. The reactors were operated at 25 ºC for 48 hours, evaluating the effect of external carbon source (glucose) and RM (from residual yeast lysate and commercial yeast extract) addition. The results showed that color removal efficiencies for the batch reactors fed with commercial yeast extract reached 90%, whereas those fed with discharged yeast lysate reached 80% (sonication) and 73% (mechanical lysis). These values were statistically higher when compared to reactors operating without RM (48 to 66%), demonstrating that yeast extract enhances azo dye degradation in anaerobic conditions and that the residual yeast is a cheap and alternative source of carbon and of the RM riboflavin.

Resumo em Inglês:

Abstract UASB reactors are a common technology for wastewater treatment. However, certain disadvantages must be considered. One of the disadvantages relates to the presence of dissolved gases, hydrogen sulfide and methane, in the effluent, which can potentially be released into the atmosphere. This can cause malodours and contribute to the greenhouse effect. In this perspective, this work investigated alternative techniques to minimize these disadvantages: air stripping inside the settling compartment; and a dissipation chamber immediately after the reactor outlet. Results achieved with the air stripping technique showed low removal efficiencies for methane, around 30%, and in the range of 40 to 60% for hydrogen sulfide. On the other hand, the removal efficiencies obtained with the dissipation chamber technique were much higher, consistently reaching 60% or more for both gases, plus a relatively lower exhaust flow. For the best operational condition tested, median removal efficiencies of 73 and 97% were observed for dissolved methane and dissolved sulfide, respectively.

Resumo em Inglês:

Abstract This study presents the environmental evaluation of an abandoned and potentially contaminated landfill using analyses for the presence of heavy metals and for methane generation potential. The site is located in the city of Santiago, Chile, and was used as a rural landfill for domestic, industrial and construction waste until 1978, but is now in a heavily urbanized area and surrounded by houses. Analyses performed on 24 samples taken in and around the site show Potential Methane Generation (PMG) values between 1.6% and 11.3% of maximum projected levels. These low values, compared to those of an active landfill, indicate that waste material stored in the site has a low capacity to generate methane. Concentrations of heavy metals in the surface and deep soil are similar to typical levels for these metals in normal soil, according to international USEPA standards, and do not present imminent risk to human health. The use of the PMG test technique for the study of the health risk of an abandoned landfill is a new contribution to the Chilean evaluation methodology and management program for Abandoned Sites with Potential Presence of Contaminants (SAPPC). As part of the environmental management strategy for the site, two of the five operable units studied were transformed into a park after this study.

Resumo em Inglês:

Abstract The aim of this study was to evaluate the application of the anaerobic bioreactor with fixed-structured bed (ABFSB) for brewery wastewater treatment with high volumetric organic loading rate (VOLR) and its comparison with a traditional packed-fixed bed bioreactor. Two different biomass support materials were tested, including polyurethane (PU) and polypropylene (PP) for both configurations. The best global efficiency was reached by the structured-fixed bed reactor with polyurethane as biomass support (SB PU). For a VOLR of 14.0 kg CODt m-3 d-1 (HRT of 8 h) and 20.3 kg CODt m-3 d-1(HRT of 12 h), the SB PU reached the average CODt removal efficiencies (ECOD) of 81% and 71%, respectively. The results show that ABFSB is a promising technology for high organic matter and solids concentration wastewater treatment, but the type of the biomass support had a big impact on the reactors performance.

Resumo em Inglês:

Abstract The behavior of anaerobic digestion in batch and UASB reactors using a microaerobic process and natural zeolites was studied. Laboratory assays were carried out across 4 sets of variables: different COD/SO42- ratios, different airflow levels, with and without natural zeolites and room and mesophilic controlled temperatures. The microaerobic process demonstrated hydrogen sulfide removal levels exceeding 90% in most cases, while maintaining the flammable condition of the generated biogas. The level of COD removal exceeded 75% in UASB reactors despite their operation under very low hydraulic retention times (2.8-4.8 hours). The effectiveness of natural zeolites in accelerating UASB reactor startup was demonstrated. Results showing the positive influence of zeolites on the granulation process in UASB reactors were also achieved.

Resumo em Inglês:

Abstract The aim of the present study was to evaluate the efficacy of treating vinasse using anaerobic digestion (AD) followed by ozonation. The AD process was performed using a laboratory-scale upflow anaerobic filter reactor (UAFR) under continuous operation at 29 ± 1 °C. Stable conditions were reached at 10 kgCOD m-3 d-1 and a hydraulic retention time (HRT) of 5 days. Under these conditions, the efficiency of reduction of the chemical oxygen demand (COD) and the methane yield were 75.1% and 0.315 m3CH4 kgCODr-1, respectively. The anaerobically digested effluent was further treated using ozone in a bubbling column. An experimental 23 array [C(03)g= 70; 100 mgO3 L-1; pH= 7.5; 10; tc = 1 and 3 h] was used. The best conditions for effluent ozonation were 100 mgO3 L-1, pH 7.5 and 3 hours of contact with ozone. The average efficiencies for COD, color and turbidity reduction were 82.4, 93.8 and 99.3%, respectively.

Resumo em Inglês:

Abstract Conventional production of instant coffee is based on solubilisation of polysaccharides present in roasted coffee. Higher process temperatures increase the solubilisation yield, but also lead to carbohydrate degradation and formation of undesirable volatile compounds. Enzymatic hydrolysis of roasted coffee is an alternative to minimize carbohydrate degradation. In this work, products obtained from thermal and enzymatic processes were compared in terms of carbohydrates and volatiles composition. Roasted coffee was extracted with water at 125 °C, and spent coffee was processed by thermal (180 °C) or enzymatic hydrolysis. Enzymatic hydrolysis experiments were carried out at 50 °C using the commercial enzyme preparations Powercell (Prozyn), Galactomannanase (HBI-Enzymes), and Ultraflo XL (Novozymes). These formulations were previously selected from eleven different commercial enzyme preparations, and their main enzymatic activities included cellulase, galactomannanase, galactanase, and β-glucanase. Enzymatic hydrolysis yield was 18% (dry basis), similar to the extraction yield at 125 °C (20%), but lower than the thermal hydrolysis yield at 180 °C (28%). Instant coffee produced by enzymatic hydrolysis had a low content of undesirable volatile compounds and 21% (w/w) of total carbohydrates. These results point to the enzymatic process as a feasible alternative for instant coffee production, with benefits including improved quality as well as reduced energy consumption.

Resumo em Inglês:

Abstract Microalgae are considered as promising feedstocks for the third generation of biofuels. They are autotrophic organisms with high growth rate and can stock an enormous quantity of lipids (about 20 - 40% of their dried cellular weight). This work was aimed at studying the cultivation of Scenedesmus obliquus in a two-stage system composed of a photobioreactor and a settler to concentrate and partially recycle the biomass as a way to enhance the microalgae cellular productivity. It was attempted to specify by simulation and experimental data a relationship between the recycling rate, kinetic parameters of microalgal growth and photobioreactor operating conditions. Scenedesmus obliquus cells were cultivated in a lab-scale flat-plate reactor, homogenized by aeration, and running in continuous flow with a residence time of 1.66 day. Experimental data for the microalgal growth were used in a semi-empirical simulation model. The best results were obtained for Fw=0.2FI, when R = 1 and kd = 0 and 0.05 day-1, with the biomass production in the reactor varying between 8 g L -1 and 14 g L-1, respectively. The mathematical model fitted to the microalgal growth experimental data was appropriate for predicting the efficiency of the reactor in producing Scenedesmus obliquus cells, establishing a relation between cellular productivity and the minimum recycling rate that must be used in the system.

Resumo em Inglês:

Abstract Recovery of spores and crystals from the fermentation broth of Bacillus thuringiensis (Bt) was studied using the membrane separation technology. Four types of polymeric membranes, with different characteristics, in the range of microfiltration (MF) and ultrafiltration (UF) were used for evaluating their permeate flux and spore-crystal recovery capacity. Results indicated that both MF and UF membranes are effective for spore-crystal recovery. The hydrophobic MF membrane made of polyvinylidene fluoride (PVDF) achieved a better performance compared to the one made with hydrophilic cellulose acetate (CA). Both had a 0.22 µm pore size, under the condition of an upper range of feed pressure. Also, with the increase of the feed flow rate, a higher flux was achieved for the PVDF membrane. A UF membrane made of polyethersulfone (PES) polymer was also used effectively for spore/crystal recovery from the broth, but under a higher operating pressure. In the entire experiment, a 99.9% rejection factor was measured with the applied membranes for the spore/crystal in the fermentation broth.

Resumo em Inglês:

Abstract In recent years, there has been a resurgence of interest concerning solid-state cultivation processes due to a number of advantages over submerged cultivation. However, studies on oxygen transfer and the performance of bioreactors are lacking. Processes that use inert supports loaded with chemically-defined liquid media have several potential applications and offer numerous advantages, such as improved process control and monitoring and enhanced process consistency compared with cultivation on natural solid substrates. The aim of this research was to study the oxygen transfer for the production of allergenic proteins from a biomass of Drechslera (Helminthosporium) monoceras cultured in a packed-bed reactor filled with polyurethane foam. The results show that a high protein concentration can be produced on an inert support with a high overall oxygen transfer coefficient (KLa) during cultivation.

Resumo em Inglês:

Abstract The IWA Anaerobic Digestion Model No. 1 (ADM1) was chosen to simulate a two-stage anaerobic digestion lab-scale plant treating domestic wastewater. Initially, the model was preliminary tested using synthetic wastewater. The simulation results were satisfactorily compared to NH4+ and chemical oxygen demand (COD) data for the first and second stages, respectively. A transformation method was then applied to estimate from the domestic wastewater composition the input variables to the ADM1. After proper calibration and further validation, the model was able to successfully predict the COD degradation from a varying influent, showing its practical applicability. Finally, a standalone application based on the validated model was developed to be used for monitoring purposes at the treatment plant. The developed application is suitable for direct implementation at a full-scale plant without the need of additional software or specialized assistance.

Resumo em Inglês:

Abstract This paper evaluated the treatment of textile wastewater in submerged anaerobic membrane bioreactors (SAMBR) operated on a bench scale. Particularly, the influence of operational conditions, such as the applied organic rate (OLR) and the dilution factor (for toxicity attenuation) of the textile wastewater, was evaluated on color and organic matter removal. In addition, the effect of powdered activated carbon (PAC) on SAMBR-1 and the addition of yeast extract (source of the redox mediator riboflavin) were also investigated. The results showed that reducing the textile wastewater dilution factor from 10× (phase 1) to 4× (phase 2) and 0× (no dilution) decreased the COD and color removal efficiencies in both SAMBRs, probably due to an increase in the toxic load. Nevertheless, PAC adsorbed toxic compounds found in the textile wastewater and helped biomass acclimatization, which led to higher COD and color removal efficiencies in SAMBR-1. The presence of yeast extract enhanced color removal efficiencies 3-fold in both SAMBRs when they were fed with undiluted textile wastewater.

Resumo em Inglês:

Abstract The use of earthworms to bioremediate soil results in decreasing the pollutant concentration through a bioaccumulation mechanism of the contaminants in the earthworm's body. The present work is an empirical study that was carried out on soils contaminated with chromium and cadmium. Organic matter in the amount of 5% and 9% of soil weight was added. Chromium and cadmium concentrations in soil and in the body of worms were measured at two time periods of 21 and 42 days. According to the results, increasing from 5% to 9% the organic material of the soil contaminated with chromium at the initial concentration of 0.06 mg/g, the removal efficiency decreased by 5%. In 0.1 mg/g concentration the bioremediation efficiency decreased by 20%, showing that the earthworms probably have more tendency to consume the organic material and low tendency for consuming the soil contaminated by metal. Results showed that, considering the increased mortality of worms in the soil at a concentration of 0.08 mg/g of chromium, using this method is not recommended. For cadmium we require more study, though we can say that the organic material had no influence on the bioremediation of the soil.

Resumo em Inglês:

Abstract Currently the oil refining sector is responsible for approximately 5% of the total Brazilian energy related CO2 emissions. Possibilities to reduce CO2 emissions and related costs at the largest Brazilian refinery have been estimated. The abatement costs related to energy saving options are negative, meaning that feasibility exists without specific income due to emission reductions. The assessment shows that short-term mitigation options, i.e., fuel substitution and energy efficiency measures, could reduce CO2 emissions by 6% of the total current refinery emissions. It is further shown that carbon capture and storage offers the greatest potential for more significant emission reductions in the longer term (up to 43%), but costs in the range of 64 to162 US$/t CO2, depending on the CO2 emission source (regenerators of FCC units or hydrogen production units) and the CO2 capture technology considered (oxyfuel combustion or post-combustion). Effects of uncertainties in key parameters on abatement costs are also evaluated via sensitivity analysis.

Resumo em Inglês:

Abstract This article describes bench scale sequential, biological and coagulation-flocculation treatment of mature leachate for the removal of nitrogen and biodegradable and recalcitrant carbonaceous material. The biological stage was conducted on two SBRs, one of which inoculated with nitrifying sludge, another without an inoculum, for 152 and 133 days, respectively. The coagulation-flocculation stage used four coagulants at different doses and pH adjustments. The treatment conducted on the inoculated SBR when a pH control was used produced mean removals of BOD5, COD and TKN of 69.6%, 38.5% and 51.6%, respectively, and practically complete denitrification. Coagulation-flocculation applied to the effluent of the inoculated biological reactor showed a superior effectiveness of the ferric coagulants, when the pH was adjusted to close to 6.0, producing removals of turbidity, COD and true color close to 95%, 78% and 92%, respectively.

Resumo em Inglês:

Abstract This study evaluated the effects of aeration (constant aeration, intermittent aeration and a lack of aeration) and hydraulic retention time (HRT) (2, 3 and 4 days) on a continuous process with cell recycling, using chitosan as a natural coagulant for the sedimentation of a C1 mixed culture. This culture was used for the biodegradation of hydrocarbons present in the effluent contaminated with diesel oil and gasoline. The responses monitored included the turbidity removal (TR), total petroleum hydrocarbon (TPH) removal and volatile suspended solids (VSS). Constant aeration and an HRT of 4 days produced the best results for the continuous process, resulting in the highest TPH removals (94% and 75% reductions in the supernatant and reaction tank, respectively) and TR (95%).

Resumo em Inglês:

Abstract Biogas production is becoming increasingly important in the environmental area because, besides treating wastewaters, it also generates energy. Co-digestion has become more and more powerful since it is possible, with the use of abundant and cheap substrates, to dilute the inhibitory effects of various other substrates, making the process of anaerobic digestion more efficient and stable. Biogas process modelling describes the kinetics and stoichiometry of different steps in the anaerobic digestion process. This mathematical modelling provides an understanding of the processes and interactions occurring inside the biogas system. The present work investigated the interactions between different simple co-substrates (carbohydrate, lipid and protein) and real co-substrates (corn silage, fodder beet, grass and wheat straw) under co-digestion with manure, in order to verify synergetic effects. Subsequently, some experiments were reproduced, in order to evaluate the synergy obtained in the previous simulation and validate the model.

Resumo em Inglês:

Abstract The paper presents the results of experimental verification of the simplified set of scaling parameters for which the particle density as well as the cold model length scale may be chosen independently. The tests were carried out on two large scale 1/10 and 1/20 geometrically similar cold models of the Lagisza 966 MWth supercritical CFB boiler. The proposed set of dimensionless quantities allowed the Lagisza 966 MWth CFB boiler to be closely modeled by cold models. However, the agreement between the hot bed and cold model's suspension density distributions is better for the 1/10 scale cold model. That suggests that the choice of the scale of a cold model is not without effect on the macroscopic movements of solids in the riser. Moreover, the study shows that a simplification of the scaling laws which excludes the very important solid-to-gas density ratio can give acceptable results over a wide range of boiler loadings.

Resumo em Inglês:

Abstract To investigate the mass transfer behavior of a liquid-liquid system with high density difference (∆ρ≈500 kg/m3), single drop experiments were performed by using the ternary chloroform-ethanol-water system. The mass transfer direction was from the dispersed phase to the continuous phase, while the aqueous phase was dispersed in chloroform to generate drops. The influences of drop diameter, initial solute concentration and temperature on the mass transfer were investigated. The effects of the drop diameter and initial solute concentration on interfacial instability of droplets hanging in the continuous phase were also observed. For the purpose of correlation, a mass transfer enhancement factor F was introduced and then correlated as a function of dimensionless variables. The modified correlation from the mass transfer coefficient model was found to fit well with the experimental values.

Resumo em Inglês:

Abstract In this research, the effect of different citric acid concentrations, ammonia concentration, temperature, leaching time, stirring speed and liquid-to-solid ratio on the zinc leaching from low-grade zinc oxide ore in a NH3-H3C6H5O7-H2O system were studied. The results showed that the zinc leaching rate is only 4.7% when the citric acid concentration is 0 M, and the leaching efficiency of Zn increased with increasing citric acid concentration. Under the conditions: citric acid concentration of 1.0 M, ammonia concentration of 6 M, temperature of 25 °C, leaching time of 60 min, stirring speed of 300 rpm and the starting solid-to-liquid ratio of 1:5, 81.2% of Zn is leached. The mineralogical changes of the low-grade zinc oxide ores during the processes were characterized by X-ray fluorescence (XRF), X-ray powder diffraction (XRD), Scanning Electron Microscopy associated with Energy Dispersive Spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FT-IR). From the evidence we deduced that citric ions complexed with zinc ions, forming a Zn-citrate complex. As a result, the zinc leaching rate was improved without the risk of pollution or pretreatment. This makes it as a good choice for a more ecological treatment of hemimorphite.

Resumo em Inglês:

Abstract The multiobjective optimization method was applied in order to improve the droplet size distribution and stability of water-in-oil emulsions composed of sunflower and pumpkin seed oils as continuous phase, polyglycerol polyricinoleate as emulsifier, water as dispersed phase and sodium chloride as co-stabilizer (lipophobe). Three composition factors were varied based on the three level Box-Behnken design and three characteristics of the obtained emulsions were measured for each experimental run. The mean volume diameter of water droplets and the span of the droplet size distribution, both determined immediately upon preparation of the emulsion, as well as the stability index over a three-month period were interrelated by regression functions with the surfactant concentration, oil composition and the salt content in the water phase of the emulsion. Also, the fourth objective function based on a difference in the prices of pumpkin seed and sunflower oils was considered for optimization. The multiobjective optimum was calculated by using the minimal loss method with weight factors. Additionally, effects of the continuous phase composition and the salt content on the equilibrium interfacial tension of water-oil systems and the changes of the droplet size distribution over time were studied.

Resumo em Inglês:

Abstract The main aim of this paper is to present a possibility to enhance the drag reduction effect in straight pipe flow by the simultaneous addition to the transported liquid of a small amount of high molecular weight polymers and surfactants. Qualitative analysis of the polymer-micellar additive influence on the shape and character of flow resistance curves has been performed. Also multicomponent polymer-micellar solution flow resistance curves were compared with appropriate single additive polymer or surfactant solution flow resistance curves. The experimental data shows that, for polymer-micellar solutions, the stable transitional zone between the laminar and the turbulent flow regions is extended toward higher values of the critical Reynolds numbers. Occurrence of the phenomenon can be explained by the flow laminarization caused by polymer-micellar aggregates. Existence of the third extended drag reduction zone in the turbulent range of flow has also been observed for the first time.

Resumo em Inglês:

Abstract Poly(vinylidene fluoride) (PVDF) and PVDF blends with various molecular weights of poly (N- vinylpyrrolidone) (PVP) films were prepared in dimethyl formamide through the solution casting method. Non-isothermal melt crystallization studies of PVDF films were carried out by cooling the molten samples at different temperatures using differential scanning calorimetry (DSC). The obtained films have been characterized by dynamic mechanical thermal analysis (DMTA). Crystallization kinetics of PVDF films were successfully described by the Jeziorney, Mo and Ziabicki models. The Ozawa equation was found to be invalid for describing the crystallization kinetics. Kinetic parameters such as t1/2, Zc and F(T) indicated that the crystallization rate decreased for PVDF/PVP films as compared to neat PVDF films and was affected by the molecular weight of PVP. The results based on Ziabicki's model revealed that the addition of PVP decreased the ability of PVDF to crystallize under non-isothermal melt crystallization conditions. The activation energy was calculated through Friedman and advanced isoconversional methods. Results showed that the addition of PVP to PVDF films caused an increase in activation energy. By comparing DMTA results of PVDF/PVP blends with neat PVDF films, it could be concluded that blending PVDF with PVP caused an increase in the glass transition temperature (Tg) while the storage modulus was decreased.

Resumo em Inglês:

Abstract In the present study, transalkylation of 1,4-diispropylbenzene (DIPB) with benzene in the presence of modified beta zeolite was performed to produce cumene in a fixed bed reactor. Beta zeolite was exchanged with cerium in order to modify its catalytic activity. Activity of the modified catalyst was evaluated in the range of temperature 493K-593K, space time 4.2 kg h/kmol-9.03 kg h/k mol and benzene/1,4-DIPB molar ratio 1-15 to maximize the reactant conversion and selectivity of cumene. The activity and selectivity of the modified catalyst was found to increase with increase in cerium loading. Maximum selectivity of cumene (83.82%) was achieved at 573 K, benzene/1,4-DIPB 5:1 at one atmosphere pressure. A suitable kinetic model for this reaction was proposed from the product distribution pattern following the Langmuir-Hinshelwood approach. Applying non-linear regression, the model parameters were estimated. The activation energy for the transalkylation reaction was found to be 116.53 kJ/mol.

Resumo em Inglês:

Abstract Real time measurements and development of sensor technology are research issues associated with robustness and safety during oil well drilling operations, making feasible the diagnosis of problems and the development of a regulatory strategy. The major objective of this paper is to use an experimental plant and also field data, collected from a basin operation, offshore Brazil, for implementing smart monitoring and decision making, in order to assure drilling inside operational window, despite the commonly observed disturbances that produce fluctuations in the well annulus bottom hole pressure. Using real time measurements, the performance of a continuous automated drilling unit is analyzed under a scenario of varying levels of rate of penetration; aiming pressure set point tracking (inside the operational drilling window) and also rejecting kick, a phenomenon that occurs when the annulus bottom hole pressure is inferior to the porous pressure, producing the migration of reservoir fluids into the annulus region. Finally, an empirical model was built, using real experimental data from offshore Brazil basins, enabling diagnosing and regulating a real drilling site by employing classic and advanced control strategies.

Resumo em Inglês:

Abstract The hydrodealkylation process of toluene (HDA) has been used as a case study in a large number of control studies. However, in terms of industrial application, this process has become obsolete and is nowadays superseded by new technologies capable of processing heavy aromatic compounds, which increase the added value of the raw materials, such as the process of transalkylation and disproportionation of toluene (TADP). TADP also presents more complex feed and product streams and challenging operational characteristics both in the reactor and separator sections than in HDA. This work is aimed at proposing the TADP process as a new benchmark for plantwide control studies in lieu of the HAD process. For this purpose, a nonlinear dynamic rigorous model for the TADP process was developed using Aspen Plus™ and Aspen Dynamics™ and industrial conditions. Plantwide control structures (oriented to control and to the process) were adapted and applied for the first time for this process. The results show that, even though both strategies are similar in terms of control performance, the optimization of economic factors must still be sought.

Resumo em Inglês:

Abstract Ultrasound assisted extraction of wedelolactone, a major coumestan present in Eclipta alba, is investigated in the present work.Various process parameters such as type of solvent, power, solvent to solid ratio and extraction temperature, which affect the extraction yield, are optimized. In the ultrasound-assisted extraction with final optimized conditions, i.e., methanol as solvent, 170 W power, 60:1 solvent to solid ratio, 50 °C temperature and 60% duty cycle, amaximum extraction yieldof 0.62 mg/g is obtained in 45 minutes. The kinetic model (Peleg's model) has been used for the prediction of the yield of wedelolactone in the extract at a given time for all experimental conditions. The values of predicted yields show good agreement with the experimental data for all parameters, i.e., power, solvent to solid ratio and temperature. The extraction of wedelolactone from Eclipta alba is also carried out by conventional extraction methods, i.e., Soxhlet and batch extraction. Ultrasound-assisted extraction gives higher extraction yield in less time as compared to batch extraction (0.41 mg/g in 90 min) and Soxhlet extraction(0.7 mg/g in 360 min). The ultrasound-assisted extraction of wedelolactone from Eclipta alba is an effective way of extraction with the advantages of lower time and higher extraction.

Resumo em Inglês:

Abstract The objective of this study was to evaluate the separation of fructooligosaccharides (FOS) from yacon extract by an ultrafiltration process using membranes of 10 and 30 kDa. The total resistance (Rt), membrane resistance (Rm), fouling resistance (Rf), and concentration polarization (Rc) during the separation process were also assessed. The operating pressures were 1.2 and 0.75 bar for UF-10 and UF-30, respectively. The permeate flux increased upon increasing the pressure from 0.5 to 2 bar and the resistance values showed a slight increase with increasing pressure. The fouling percentages were 61.24% and 57.33% for the membranes UF-10 and UF-30, being reversible after the cleaning procedure with acidic and basic solution, resulting in high percentages of flux recovery of 76.46% and 83.56% for U-10 and UF-30, respectively. The FOS retention values were 24.48% and 6.49% for both membranes UF-10 and UF-30, corresponding to 24% and 18.4% purity.

Resumo em Inglês:

Abstract The effects of relative humidity (RH), carbon dioxide (CO2), methane (CH4), oxygen (O2) presence and gas hourly space velocity (GHSV) on H2S adsorption dynamics of KOH/CaO impregnated activated carbon are investigated in this study. X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray detector (SEM-EDX), thermogravimetric analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) techniques are applied and nitrogen adsorption characteristics are determined for characterization. The presence of water, O2 and lower GHSV has beneficial effects on the activated carbon performance. CO2 decreases the adsorption capacity due to its acidic characteristics. Best adsorption capacity is obtained as 13 wt % in KOH/CaO impregnated activated carbon, in a CH4 (60%)/CO2 (38%)/O2 (2%) gas atmosphere, at ambient temperature, RH 90 and 5000 h-1 GHSV. Sulphur species formation was verified with the help of SEM-EDX, XRD, TGA, FTIR and nitrogen adsorption analysis on the exhausted samples.

Resumo em Inglês:

Abstract The influences of extractants concentrations and solvent polarity on the efficiency of pantothenic acid separation by synergic extraction with tri-n-octylamine (TOA) and di(2-ethylhexyl) phosphoric acid (D2EHPA) mixture have been analyzed. The results indicated the formation of an interfacial compound which includes one molecule of pantothenic acid and one of D2EHPA, its hydrophobicity being increased by solvation with additional TOA molecules. For solvents with lower dielectric constants, n-heptane and n-butyl acetate, the number of amine molecules participating in the interfacial complex formation was controlled by solvent polarity and D2EHPA concentration, decreasing with the increase of these two parameters. For dichloromethane, the chemical structure of the extracted compound remained the same regardless of D2EHPA concentration. The most important synergic effect corresponded to the extractant mixture dissolved in n-heptane, at low D2EHPA concentration in the organic phase (5 g/l).

Resumo em Inglês:

Abstract A method is proposed to study the separation of minimum-, maximum-boiling azeotropic, and low volatility mixtures with a light entrainer, to investigate feasible regions of the key operating parameters reboil ratio (S) and entrainer - feed flowrate ratio (FE/F) for continuous processes. The thermodynamic topological predictions are carried out for 1.0-2, 1.0-1a, and 0.0-1 Serafimov's class diagrams. It relies upon the knowledge of residue curve maps, along with the univolatility line, and it enables the prediction of possible products at the bottom of the column and limiting values of FE/F. The profiles of the stripping, extractive, and rectifying sections are calculated by equations considering S and FE/F, and they bring information about the location of singular points and possible composition profile separatrices that could impair process feasibility. Providing specified product composition and recovery, the approximate calculations are compared with rigorous simulations of extractive distillation processes. Separating non-ideal mixtures using a light entrainer provides more opportunities for the case when it is not easy to find an appropriate heavy or intermediate entrainer.

Resumo em Inglês:

Abstract Wax deposition behavior was investigated in a set of one-inch experiment flow loops, using a local crude oil with high wax content. The temperature of the oil phase is chosen as a variable parameter while the temperature of the coolant media is maintained constant. Detailed composition of the deposit is characterized using High Temperature Gas Chromatography. It was found that the magnitude of the diffusion of the heavier waxy components (C35-C50) decreases when the oil temperature decreases, but the magnitude of the diffusion of the lighter waxy components increases. This result means that the diffusion of wax molecules shifts towards lower carbon number, which further proves the concept of molecular diffusion. Meanwhile, a meaningful phenomenon is that the mass of the deposit increases with the oil temperature decrease, which definitely proves the influence of wax solubility on deposition, while the formation of an incipient gel layer reflects the fact that an increase in the mass of the deposit does not mean a larger wax percentage fraction at lower oil temperature.

Resumo em Inglês:

Abstract Part of the oil found in the Brazilian subsoil has a high wax content, which makes its flow process difficult at low temperatures because of the increase in the viscosity of the fluid. This paper studied the flow behavior of waxy crude oil under variation in the temperature of the external environment of the flow, the volumetric flow rate of the oil and the emulsified water content of the oil. The results were compared with those obtained for a non-waxy crude oil that had similar rheological properties at temperatures above the wax appearance temperature (WAT). The proposed tests were based on the experimental design technique, and the behavior of the fluids was evaluated based on the pressure variation generated by the flow.

Resumo em Inglês:

Abstract This study concerns a new antiretroviral drug named CRS 74, which has a limited bioavailability because of its low aqueous solubility and dissolution rate. To improve these properties, CRS 74 can be recrystallized by using Liquid Anti-Solvent (LAS) crystallization. Ethanol is chosen as the solvent under study for the molecule and water as the anti-solvent. Since solubility data is limited, it is necessary to collect experimental data for the molecule in relation to ethanol and water-ethanol mixtures at different temperatures in order to select suitable mixture compositions and temperature for LAS process design. In this work, the CRS 74 solubility measured in the temperature range 288.15 - 303.15 K in pure ethanol and in 95% water - 5% w/w ethanol mixtures, and the CRS 74 solubility measured at 303.15 K in water-ethanol mixtures containing from 30 to 70% w/w ethanol are presented. Measurements were performed using the shake-flask method for generating the saturated solutions followed by compositional analysis by HPLC of the solution. The experimental data showed that the solubility of CRS 74 in binary hydroalcoholic mixtures increases upon increasing the temperature and mass fraction of ethanol. In order to better understand the behavior of the system and to estimate supersaturation conditions for a larger range of CRS 74 crystallization conditions, two models have been chosen to describe the experimental data: UNIQUAC and Jouyban-Acree models. The modeling of experimental solid-liquid equilibrium data proved that both models could correlate satisfactorily the solubility of the studied drug. This study provided valuable data for the recrystallization of CRS 74 by using the Liquid Anti-Solvent (LAS) crystallization process.

Resumo em Inglês:

Abstract Accurate estimation of reservoirs fluid properties, as vital tools of reservoir behavior simulation and reservoir economic investigations, seems to be necessary. In this study, two important properties of crude oil, bubble point pressure (Pb) and formation volume factor (Bob), were modelled on the basis of a number of basic oil properties: temperature, gas solubility, oil API gravity and gas specific gravity. Genetic programming, as a powerful method, was implemented on a set of 137 crude oil data and acceptable correlations were achieved. In order to evaluate models, two test datasets (17 data for Pb and 12 data for Bob) were used. The squared correlation coefficient (R2) and average absolute relative deviation (AARD %) over the total dataset (training + test) are 0.9675 and 8.22% for Pb and 0.9436 and 2.004% for Bob, respectively. Simplicity and high accuracy are the advantages of the obtained models.

Resumo em Inglês:

Abstract The reduction in the availability of fossil fuel increased the search for alternative fuel sources (for example, ethanol). In the Brazilian market, light duty vehicles can be fueled with gasohol (18 up to 27.5 %v/v of anhydrous ethanol in gasoline) and/or hydrous ethanol. To minimize the risk of water-induced phase separation of gasoline-ethanol blends, anhydrous ethanol is blended into gasoline at the distribution terminal, rather than distributing it through pipelines. Pure ethanol can be distributed through pipelines or trucks, and in pipeline cases almost all are not exclusive. To monitor the ethanol quality, several fuel sampling points are indicated: storage tanks, pipelines, and ship, if applicable. For these samples, it is important to evaluate the following parameters indicative of product quality: hydrocarbon and water amount, color, conductivity, and acidity. Monitoring ethanol storage, transport and distribution is important to maintain the ethanol quality until the final consumer.