Scielo RSS <![CDATA[Brazilian Journal of Chemical Engineering]]> http://www.scielo.br/rss.php?pid=0104-663220180001&lang=en vol. 35 num. 1 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Acetic acid production by the newly isolated <em>Pseudomonas</em> sp. CSJ-3]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100001&lng=en&nrm=iso&tlng=en ABSTRACT A fermentative acetic acid producing strain, named CSJ-3, was isolated from sludge and identified as Pseudomonas sp. on the basis of 16S rRNA gene analysis. The effects of cultivation conditions on the production of acetic acid by Pseudomonas sp. CSJ-3 were investigated in batch fermentation, and the maximum yield of acetic acid reached up to 0.49 % during 30 h cultivation under the optimum growth condition, including fermentation temperature of 37.0 ºC, fermentation pH of 4.50, ethanol concentration of 8 %, carbon source (glucose) amount of 10 g/L, and rotation speed of 120 r/min. When ultraviolet (UV) irradiation was used for the mutation in culture medium to improve the yield of acetic acid, the results showed that the yield of acetic acid reached up to 0.59 %. UV and FTIR confirmed that acetic acid was the major fermented product. <![CDATA[Ethanol production from <em>Dekkera bruxellensis</em> in synthetic media with pentose]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100011&lng=en&nrm=iso&tlng=en Abstract Ethanol is obtained in Brazil from the fermentation of sugarcane, molasses or a mixture of these. Alternatively, it can also be obtained from products composed of cellulose and hemicellulose, called “second generation ethanol - 2G”. The yeast Saccharomyces cerevisiae, commonly applied in industrial ethanol production, is not efficient in the conversion of pentoses, which is present in high amounts in lignocellulosic materials. This study aimed to evaluate the ability of a yeast strain of Dekkera bruxellensis in producing ethanol from synthetic media, containing xylose or arabinose, xylose and glucose as the sole carbon sources. The results indicated that D. bruxellensis was capable of producing ethanol from xylose and arabinose, with ethanol concentration similar for both carbon sources, 1.9 g L-1. For the fermentations performed with xylose and glucose, there was an increase in the concentration of ethanol to 5.9 g L-1, lower than the standard yeast Pichia stipitis (9.3 g L-1), but with similar maximum yield in ethanol (0.9 g g TOC-1). This proves that the yeast D. bruxellensis produced lower amounts of ethanol when compared with P. stipitis, but showed that is capable of fermenting xylose and can be a promising alternative for ethanol conversion from hydrolysates containing glucose and xylose as carbon source. <![CDATA[Heterotrophic cultivation of <em>Euglena gracilis</em> on chemically pretreated media]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100019&lng=en&nrm=iso&tlng=en Abstract In this research, the impact of chemical agents on the growth of Euglena gracilis and contaminants (S. cerevisiae and B. subtilis) in different cultivation media was studied. E. gracilis was cultivated on modified Hutner and complex medium in Erlenmeyer flasks and a stirred tank bioreactor. H2O2 and antimycin were used as suppressors of contaminant growth activities during algae cultivation. The use of antimycin as a chemical suppressor of contaminants is not recommendable because of its significant impact on the E. gracilis growth. At a H2O2 concentration of 5 mg L-1 contaminant growth activities were almost completely suppressed. In these conditions, E. gracilis is capable to grow, but a further increase of H2O2 concentration is related to significant reduction of algae growth. H2O2 as a suppressor of contaminants has great potential for industrial application, but its optimal concentration for a particular bioprocess has to be determined in order to obtain the maximal bioprocess efficiency. <![CDATA[Feasibility of biohydrogen production by co-digestion of vinasse (sugarcane stillage) and molasses in an AnSBBR]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100027&lng=en&nrm=iso&tlng=en Abstract This work studied the feasibility of biohydrogen production by co-digestion of vinasse/molasses in an AnSBBR operated with mechanical stirring (30°C and 200 rpm). Hydrogen production by co-digestion of vinasse/sucrose was also studied to verify the performance of the process with a known co-substrate with easy degradation. The effects of influent composition (vinasse/sucrose and vinasse/molasses), influent concentration (3000 and 4000 mgCOD.L-1) and cycle time (3 and 4 h) on performance indicators were evaluated using stability, organic matter removal efficiency, molar hydrogen yield, productivity and biogas composition. The condition with vinasse/molasses in the influent that showed the best results was obtained with a 3-hour cycle time, influent concentration of 3000 mgCOD.L-1 and composition of 33% vinasse and 67% molasses. The molar productivity in this condition was 3.8 molH2.m-3.d-1 with a hydrogen molar fraction of 16% (and a methane molar fraction of 14%). A first order kinetic model was fitted efficiently to the best conditions. <![CDATA[Lead hazard evaluation for cathode ray tube monitors in Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100043&lng=en&nrm=iso&tlng=en Abstract Cathode ray tube (CRT) monitors are electronic equipment mainly made of glass, polymers and metals. These devices became obsolete because of emerging technologies such as LCD, LED and plasma; thus generating a huge stockpile of e-waste worldwide. In this CRT study, a natural leaching simulation (NBR10005) was performed to determine the toxicity of this e-waste. The standard NBR 10005 procedure was performed for 7 different monitors. The results show all samples are hazardous according to local environmental law (NBR 10004) due to lead leaching. The CRT panel is lead free, while the CRT funnel and neck have about 20% of lead oxide in their composition. Moreover, six optimum thermal lead removal procedures were performed and the NBR 10005 procedure was repeated. The results reveal that vacuum atmosphere and the addition of 5% carbon graphite as reducing agent are optimum conditions to turn the CRT into a non-hazardous waste. Three out of six parameters were capable of satisfactorily removing the lead and turning the post-procedure waste lead-leaching safe. <![CDATA[Wastewater treatment in a pilot-scale submerged membrane bioreactor: study of hydrodynamics under constant operating pressure]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100051&lng=en&nrm=iso&tlng=en Abstract A pilot-scale Submerged Membrane Bioreactor provided with PEI hollow fiber membranes was operated under constant pressure mode in order to evaluate the effects of hydrodynamic conditions on the process performance, such as air flow rate, module packing density and aeration configuration. For the three different air flow rates studied (2, 5 and 8 L/min), results showed a limit value for this parameter, in which above this value a better performance will not be obtained and can even be worse. The air flow rate of 5 L/min presented the best performance, followed by 8 and 2 L/min. The module packing density was studied for two diameters (0.75 and 1 inch); the best result was observed for the larger diameter module, because lower packing density causes more space between fibers, increasing the aeration homogeneity inside de fiber bundle. Both aeration geometric tested showed similar permeate fluxes, indicating they did not affect the process performance. For all hydrodynamic conditions, the removal of TOC and COD was 96% and 93%, respectively. <![CDATA[Electroremediation of deactivated catalysts from fluidised catalytic cracking for vanadium removal - the effect of a dual cathode chamber reactor]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100063&lng=en&nrm=iso&tlng=en Abstract The aim of this study was to evaluate the quantity of vanadium removed through electrokinetic remediation applied to catalyst waste used in a fluid catalytic cracking process. In excess, vanadium affects process efficiency by reducing the catalyst’s activity, causing deactivation and reducing its useful life in petroleum cracking during refining. The electrochemical reactor used was composed of an extra cathode chamber coupled with an ion-selective cation exchange membrane, Nafion ®. The function of the cathode chamber was to increase the overpotential for a hydrogen reduction reaction (HRR) and the electric field to favour metal ion removal. Sodium citrate was used for electrolyte remediation (complexing vanadium) at 0.5 mol/L with an 11.0 V (ε =0.5 V/cm) potential applied. The treatment efficiency was analysed based on the vanadium ion concentration in the electrolyte collected. The results show that electrokinetic remediation using the dual cathode chamber yielded more metal removal and lower energy consumption. <![CDATA[Development of eco-efficiency comparison index through eco-indicators for industrial applications]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100069&lng=en&nrm=iso&tlng=en Abstract In the last decades companies aligned with the concepts and principles of sustainable development have been seeking to minimize the environmental and social impacts caused by their operations. Typically, the primary environmental concerns in the industry were related to water consumption, wastewater production, waste generation, energy consumption and mainly CO2 emission - which is one of the causes of the greenhouse effect. However, the environmental eco-efficiency is not clearly seen when the evaluations of these eco-indicators are individually used and, therefore, it becomes necessary to implement a methodology that enables a joint assessment involving various aspects. In this paper we have developed an environmental index, called Eco-efficiency Comparison Index (ECI), applied to evaluate in real time a petrochemical facility. Throughout a study-case based on experimental data, the results have evidenced that the ECI is a useful tool for eco-efficiency analysis for process monitoring. <![CDATA[Application of submerged membrane bioreactor technology for the treatment of high strength dairy wastewater]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100091&lng=en&nrm=iso&tlng=en Abstract In this study, an aerobic submerged membrane bioreactor (sMBR) was used for the treatment of dairy wastewater at 15 h of hydraulic retention time (HRT) and 40 d of sludge retention time (SRT) with constant permeate flux (9.5 L.m-3.d-1(LMH)). The COD, ammonia-nitrogen (NH3-N) and orthophosphate (PO4-P) removal efficiencies were 98.2%, 95.4% and 88.9%, respectively. The results demonstrated that sMBR was a suitable and effective treatment for removal of organic matter and nutrients for treating dairy wastewater. The properties of the activated sludge, such as extracellular polymeric substances (EPS) and soluble microbial products (SMP) concentration, protein and carbohydrate, relative hydrophobicity, zeta potential and floc size distribution were also investigated. According to the results obtained, the total EPS content was lower than that of domestic wastewater treatment by MBR technology. <![CDATA[Experimental study of the diffusion-controlled corrosion of copper in the bottom of a jet stirred reactor]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100101&lng=en&nrm=iso&tlng=en Abstract Jet stirred tank reactors are usually preferred to mechanically stirred tank reactors in the case of high pressure stirred tank reactors in order to avoid the mechanical problems inherent with mechanically agitated reactors. Owing to the impact force exercised by the fluid jet on the tank bottom, the tank bottom is subjected to severe corrosion. The aim of the present work is to address this problem using an accelerated system which simulates natural diffusion-controlled corrosion of metals. Diffusion-controlled corrosion of a fixed copper disc, at the bottom of a cylindrical tank, under a single phase forced jet flow of acidified dichromate solution was investigated. Variables studied were: physical properties of the solution, solution velocity through different diameters of jet nozzle, distance between the jet outlet nozzle and the copper disc surface; and the effect of using a drag reducing polymer. An overall correlation was obtained: Sh = 0.579 Sc 0.33 Re 0.975 (h/d) 0.049 valid for 850 &lt; Sc &lt; 1322, 1852 &lt; Re &lt; 5000 and 0.3 &lt; h/d &lt; 1.2. Addition of polyethylene oxide as a drag reducing polymer was found to diminish the rate of corrosion under single phase forced jet flow by an amount depending on the operation conditions. <![CDATA[Leaching kinetics of ulexite ore in aqueous medium at different CO <sub>2</sub> partial pressures]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100111&lng=en&nrm=iso&tlng=en Abstract This manuscript presents a study regarding the leaching kinetics of ulexite (Na2O.2CaO.5B2O3.16H2O) under different CO2 partial pressures in aqueous media. The effects of the reaction temperature, particle size, CO2 partial pressure, solid-liquid ratio, and agitation speed were investigated in the boron extraction from the ore. As a result of the experimental studies, it was found that the leaching rate increased with the rise in the reaction temperature and CO2 partial pressure, and decreased with the increase in the particle size and solid-liquid ratio. The reaction temperature was found to be a significant parameter affecting the leaching rate, which varied from 13% to 97% between 303 and 393 K. Agitation speed appears to have no significant effect on the leaching rate. By using several empirical kinetic models to correlate the experimental data, it was found that the leaching rate fits to the Avrami Model. The activation energy of the process is found to be 21.1 kJ.mol-1. <![CDATA[Influence of reaction time on the structure of polyaniline synthesized on a pre-pilot scale]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100123&lng=en&nrm=iso&tlng=en Abstract The aim of this work is to follow the structural variations of polyaniline (PAni) obtained by chemical oxidation on a pre-pilot scale, with different reaction times. Synthesis of PAni is well known, but when it is carried out on a pre-pilot scale, several factors can lead to structural changes and understanding these changes is important to improve controls on the synthesis process. The polymers formed were characterized by spectroscopic techniques (Raman spectroscopy, Fourier Transform Infrared - FTIR and UV-Visible). Degree of oxidation and yield were calculated for each reaction time. The analysis by FTIR, the calculated degree of oxidation and the yield showed significant changes in polymer structure at reaction times of 65 and 80 min. This result was attributed to the excessive oxidation of PAni, with the breaking of its polymer chain. The changes observed in the structure of PAni gave subsidies to the optimization of the process of obtaining polyaniline by chemical synthesis. <![CDATA[Catalytic hydrogen generation from NaBH <sub>4</sub> /H <sub>2</sub> O system: effects of catalyst and promoters]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100131&lng=en&nrm=iso&tlng=en Abstract A hydrogen generation system based on NaBH4 hydrolysis is affected by the nature of the catalyst and catalyst promoter. Various catalyst promoters such as Al2O3 nanoparticles, Al2O3 particles, ZrO2 sand, SiO2, MMT clay, CNT and zeolite are compared with respect to hydrogen generation (HG) and hydrogen generation rate (HGR). The highest HG and HGR are observed with alumina nanoparticles as compared to other promoters. Cobalt chloride is found to be most efficient catalyst among the other cobalt based salts (CoCl2.6H2O, CoSO4.7H2O, (CH3COO)2Co.4H2O, Co(NO3)2.H2O), cadmium based salt (CdSO4) and copper based salt (CuSO4.5H2O). Maximum HGR obtained is 19.47 moles/L.sec for NaBH4 (1.26 moles/L)/Al2O3 nanoparticles (0.12 moles/L)/H2O and CoCl2.6H2O (0.02 moles/L) as catalyst at room temperature and atmospheric pressure. NaBH4 and alumina hydrolysis reactions, hydrophilic and amphoteric nature of alumina, affinity of Co+2 towards BH4 - ions and formation of aluminates are the factors that promote HGR, as illustrated in this work. Residue obtained from hydrolysis reaction is characterized for its elemental composition by the EDS technique, which confirmed a maximum percentage of boron in the residue. XRD and FTIR results concluded that adsorption of Na+ and Co+ ions occurred on the alumina surface and resulted in the formation of sodium aluminates and cobalt aluminates in the solution. <![CDATA[Optimization of the performance of a microbial fuel cell using the ratio electrode-surface area / anode-compartment volume]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100141&lng=en&nrm=iso&tlng=en Abstract This paper focus on the determination of the influence of the electrode-surface area / anode-compartment volume ratio (ESAVR) on the performance of microbial fuel cells (MFC), both in terms of the generation of electricity and the removal of organic matter from waste. Real wastewater coming from a winery factory was used and five ESAVRs were tested in separate MFCs, ranging from 0.15 to 0.75cm2cm-3. Results demonstrate that the electricity generation increases by decreasing the anode-compartment volume. Thus, by increasing ESAVR, maximum current density increased from 583 to 2416 mA m-2. However, the COD removal was found to be more efficient upon decreasing the ESAVR (from 590 to 1075 mg COD L-1 d-1). Results are of extreme significance for the mechanical design of MFC in order to optimize their performance during normal operation. <![CDATA[Ce/kaolin clay as an active catalyst for fatty acid methyl esters production from cottonseed oil in a new integrated apparatus]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100147&lng=en&nrm=iso&tlng=en Abstract An efficient solid acid catalyst (Ce/Kaolin clay) was prepared and investigated for transesterification of cottonseed oil to fatty acid methyl esters (FAME). The catalysts were characterized by XRD, BET, and NH3-TPD measurements. A new integrated apparatus for extraction and transesterification of cottonseed oil was developed. The effects of cerium loading, catalyst calcination temperature, methanol flow rate, reaction temperature, reaction time, and catalyst amount were also investigated. The results indicated that the Ce/Kaolin clay showed high catalytic activity under the calcination temperature of 700 oC and cerium loading of 0.05 g/g. The optimum transesterification reaction conditions were as follows: methanol flow rate 4.0 mL/min, reaction temperature 60 oC,reaction time 3 h, and catalyst amount 15 g. Under these conditions, the yield of FAME was up to 91%.The catalytic activity of Ce/Kaolin clay still remained high after 4 times of repeated use. The results indicated that the Ce/Kaolin clay catalysts had a good potential for use in the large-scale production of FAME. <![CDATA[Effect of Lime Addition to CaSO <sub>4</sub> Oxygen Carrier in Chemical Looping Combustion]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100155&lng=en&nrm=iso&tlng=en Abstract Chemical-looping combustion (CLC), which has the characteristic of greenhouse gas CO2 inherent separation, is a novel combustion technology. In this study, CLC experiments of methane using CaSO4 oxygen carrier with lime addition were carried out in a batched fluidized bed reactor, where the sample was exposed to alternate oxidizing and reducing conditions. The influences of temperature, calcium-to-sulphur ratio and lime particle size on the conversion of CaSO4 and sulfur capture were investigated and a suitable operation condition was determined. Under the optimal operation condition, a multi-cycle test was performed to evaluate the cyclic redox behavior of the lime-promoted CaSO4 sample. X-ray diffraction and a field emission scanning electron microscope were used to characterize the phase and surface morphology of the samples used. The results show that the addition of lime could improve the conversion rate of CaSO4 and the capture efficiency of sulfur-containing gases. The operation conditions of calcium-to-sulfur ratio 0.8, lime particle size of 180-250 μm and operation temperature of 900 °C turned out to be the optimal conditions. Besides, the average desulphurization rate of lime was up to 78.77% during the cyclic test. <![CDATA[Modification of palm oil crystallization by phytosterol addition as a tool for structuring a low saturated lipid blend]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100169&lng=en&nrm=iso&tlng=en Abstract Fat structural modifications promoted by phytosterol addition ( a hypocholesterolemic component ( to palm oil and a mixture of palm oil and canola oilwere evaluated in order to develop fats with reduced saturated fatty acids. Palm oil added with free or esterified phytosterols was investigated in terms of triacylglycerol composition, microstructure, solid fat content, and crystallization behavior before and after chemical interesterification. The addition of 10% of free phytosterols to samples before interesterification built up a denser crystal fat network structure. After interesterification, the free phytosterols lost their structuring ability and behaved as the esterified form. Free phytosterols were subsequently added to blends of palm oil and canola oil (50:50 w/w%) at different concentrations. Consistency measurements and microscopic observation confirmed that, at concentrations of 6, 8, and 10%, the free phytosterols upgraded the fat structure forming a strongly cohesivefat crystal network. <![CDATA[ZnO nanoparticle fabrication starting from ultra-high (1:2) PVOH/ZnAc proportion electrospun nanowire mats]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100181&lng=en&nrm=iso&tlng=en Abstract: The high versatility of nanostructured ZnO has drawn considerable attention from the scientific community since the second half of the two thousand decade. Within this timeframe, electrospinning became one of the simplest ways to produce nanostructured ZnO. In this work, we present the production and characterization of ZnO nanoparticles obtained from electrospun fiber mats using the highest (1:2) PVOH/ZnAc proportion reported so far. The thermally annealed samples were characterized using , X-Ray Diffraction (XRD), High Resolution Scanning Electron Microscopy (HRSEM), Energy Dispersive X-Ray analysis (EDS) and Cathodoluminescence (CL). The results obtained show that all annealed samples present excess zinc as oxygen vacancies (VO, VO +) or oxygen antisites (OZn) which contribute to a considerable change in the CL spectra. This change evidences the presence of defect levels within the ZnO gap, which might be an indication that our nanoparticles present higher catalytic activity within the visible spectrum. <![CDATA[Lithium containing MgAl mixed oxides obtained from sol-gel hydrotalcite for transesterification]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100189&lng=en&nrm=iso&tlng=en Abstract The innumerous advantages of heterogeneous catalysts employed in biodiesel production have stimulated the search for a solid catalyst capable of replacing the industrially used homogeneous catalysts. This paper investigates the effect of the sol-gel method in the catalytic activity and stability of Li-MgAl mixed oxides prepared by the “in situ” lithium addition to a MgAl hydrotalcite. The analyses based on N2 physisorption, thermogravimetric analysis, X-ray diffractometry, scanning electron microscopy and temperature-programmed desorption of CO2 were carried out to elucidate the properties of the catalysts. Considerable differences in the physico-chemical properties of the catalysts were observed with the Li addition. Li reduced the surface area and increased the crystallite size of the oxides. Furthermore, Li-MgAl mixed oxides prepared by the calcination of the sol-gel MgAl hydrotalcites presented substantial morphological differences when compared to the same oxides obtained by heat treatment of hydrotalcites synthesized via the conventional co-precipitation route. Furthermore, Li increased the number and strength of the base sites which resulted in the increase of the oxide reactivities towards the transesterification reaction between methyl acetate and ethanol. The activity was dependent on the Li loading on the catalysts. The catalyst containing only 5 wt.% Li turned out to be highly active (( 85% conversion at 50°C, ethanol/methyl acetate molar ratio = 6/1, 4 wt.% of catalyst and 30 min of reaction). Stability tests showed that the Li-MgAl catalysts lose activity after 3 reuse cycles. <![CDATA[An integrated optimization and simulation model for refinery planning including external loads and product evaluation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100199&lng=en&nrm=iso&tlng=en Abstract Because of its potential benefits, petroleum refineries are increasingly concerned about their planning operations. Although some refinery models for production planning were proposed, they are quite limited in their usefulness. This study describes an integrated approach involving nonlinear optimization and simulation of refinery units in order to obtain a production planning for a given refinery that maximizes profit. The problem is modeled through the LINGO 16.0 software interface and is solved using LINGO’s Global Solver on an Intel i5-2410M processor (8 GB RAM). A case study pertaining to the Refinaria de Paulínia (REPLAN) is proposed, and external loads, product adding, and product pricing is studied, achieving a global optimum solution for the blending in less than a second in every case.The small computational time assures the model usefulness in refinery planning, being important for sensitivity analyses and the determination of break-even points of external loads and of new products. These results indicate that this new approach has a considerable potential for achieving significant gains in terms of planning and profit increase. The model can therefore be used by planners, with significant advantages over other models. The flexibility of the model allied with its quick generation of good solutions is highlighted. <![CDATA[Harmonious interaction of incorporating CNTs and zeolitic imidazole frameworks into polysulfone to prepare high performance MMMs for CO <sub>2</sub> separation from humidified post combustion gases]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100217&lng=en&nrm=iso&tlng=en Abstract Multi-walled carbon nanotubes (CNTs) and zeolitic imidazole frameworks (ZIF-301) were synergistically incorporated into glassy polysulfone (PSF) to prepare mixed-matrix membranes (MMMs) to separate CO2 from post combustion flue gas. The flexible MMMs rendering consistent distribution and improved adhesion of nanofillers with the polymer matrix were hydrothermally stable under wet conditions. Gas sorption analysis along with dry and wet gas permeation experiments showed that both CO2 permeability and CO2/N2 selectivity of MMMs were improved owing to the synergistic effect of nanofillers. The MMM filled with 18 wt % ZIF-301 nanofillers and 6 wt % CNTs showed an optimum separation performance by providing a CO2 permeability of 19 Barrers with a CO2/N2 selectivity of 48. The CO2 separation performance of MMMs prepared in this work was found to be better than those of already existing hydrothermally stable MMMs. <![CDATA[<strong>Fractionation of <em>Apis mellifera</em> venom by means of ultrafiltration: removal of phospholipase A</strong> <sub><strong>2</strong></sub>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100229&lng=en&nrm=iso&tlng=en Abstract The fractionation of apitoxin (bee venom) by means of a commercial 10 kDa ultrafiltration membrane was investigated aiming at the removal of phospholipase A2, the main allergenic substance. The feed content was varied from 1 to 50 g apitoxin/L, in deionized water, and caused changes in membrane flux and rejection, due to concentration polarization. The increase in pressure difference and stirring rate improved the flux through the membrane. The best result was achieved for 1 g apitoxin/L in feed stream, with a pressure difference of 220 kPa, and 750 rpm, with a permeate flux of 103 kg/m2h. The use of ultrafiltration was efficient to improve the permeate safety since biological tests revealed that the remaining enzyme lost its ability to catalyze the hydrolysis of phospholipids. <![CDATA[Mathematical modeling of the batch adsorption of proteins on new restricted access media with poly(ethylene glycol) as a semi-permeable barrier using compact finite differences]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100237&lng=en&nrm=iso&tlng=en Abstract In this work we describe a mathematical analysis of the batch adsorption process of several proteins using a new restricted access medium consisting of agarose beads grafted with poly(ethylene glycol) (PEG) as a semi-permeable barrier and immobilized metal ions or ion exchange groups as binding sites. The model was fitted to experimental data, allowing the estimation of the adsorption rate constant and the effective diffusivity for each protein. The model was solved using compact finite differences in a MATLAB® platform. According to the results, the presence of grafted PEG reduces the adsorption of all proteins to different extent; with high molecular weight proteins being affected the most. The model also establishes a reduction in the adsorption rate constant (which affects protein interaction with binding sites). The movement of the protein molecules in the adsorbent pores is also affected by the grafted PEG, but to a lesser extent. <![CDATA[Competitive Adsorption of Dye Species onto Biomass Nanoporous Carbon in Single and Bicomponent Systems]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100253&lng=en&nrm=iso&tlng=en ABSTRACT We first present a cost-effective approach to simultaneously dispose of rutaceae plant waste (the discarded peels of orange, finger citron, pomelo and lemon) to yield biomass nanoporous carbons (BNCs). The adsorption of orange II (OII) and acid chrome blue K (ACBK) from aqueous solutions in single and binary dye systems by four types of BNCs were studied in a batch adsorption system. The adsorption studies include both equilibrium adsorption isotherms and kinetics. Four adsorption models for predicting the multicomponent equilibrium sorption isotherms have been compared in order to determine which one is the best fit model to predict or correlate binary adsorption data. The kinetic data were well described by the pseudo-second-order kinetic model. It was found that the adsorption capacity of orange peel-based nanoporous carbon (OPC) is much higher than those of the other types of BNCs. In addition, OPC also shows higher OII uptake capacities from binary dye solutions. The four types of BNCs could be employed as a low-cost alternative for the removal of textile dyes from effluents. <![CDATA[An Examination of the Prediction of Hydrate Formation Conditions in the Presence of Thermodynamic Inhibitors]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100265&lng=en&nrm=iso&tlng=en Abstract Gas hydrates are crystalline compounds, solid structures where water traps small guest molecules, typically light gases, in cages formed by hydrogen bonds. They are notorious for causing problems in oil and gas production, transportation and processing. Gas hydrates may form at pressures and temperatures commonly found in natural gas and oil production pipelines, thus causing partial or complete pipe blockages. In order to inhibit hydrate formation, chemicals such as alcohols (e.g., ethanol, methanol, mono-ethylene glycol) and salts (sodium, magnesium or potassium chloride) are injected into the produced stream. The purpose of this work is to briefly review the literature on hydrate formation in mixtures containing light gases (hydrocarbons and carbon dioxide) and water in the presence of thermodynamic inhibitors. Four calculation methods to predict hydrate formation in those systems were examined and compared. Three commercial packages (Multiflash®, PVTSim® and CSMGem) and a hydrate prediction routine in Fortran90 using the van der Waals and Platteeuw theory and the Peng-Robinson equation of state were tested. Predictions given by the four methods were compared to independent experimental data from the literature. In general, the four methods were found to be reasonably accurate. CSMGem and Multiflash® showed the best results. <![CDATA[Erratum]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322018000100275&lng=en&nrm=iso&tlng=en Abstract Gas hydrates are crystalline compounds, solid structures where water traps small guest molecules, typically light gases, in cages formed by hydrogen bonds. They are notorious for causing problems in oil and gas production, transportation and processing. Gas hydrates may form at pressures and temperatures commonly found in natural gas and oil production pipelines, thus causing partial or complete pipe blockages. In order to inhibit hydrate formation, chemicals such as alcohols (e.g., ethanol, methanol, mono-ethylene glycol) and salts (sodium, magnesium or potassium chloride) are injected into the produced stream. The purpose of this work is to briefly review the literature on hydrate formation in mixtures containing light gases (hydrocarbons and carbon dioxide) and water in the presence of thermodynamic inhibitors. Four calculation methods to predict hydrate formation in those systems were examined and compared. Three commercial packages (Multiflash®, PVTSim® and CSMGem) and a hydrate prediction routine in Fortran90 using the van der Waals and Platteeuw theory and the Peng-Robinson equation of state were tested. Predictions given by the four methods were compared to independent experimental data from the literature. In general, the four methods were found to be reasonably accurate. CSMGem and Multiflash® showed the best results.