Scielo RSS <![CDATA[Brazilian Journal of Chemical Engineering]]> vol. 23 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<B>The process of biosorption of heavy metals in bioreactors loaded with sanitary sewage sludge</B>]]> This work on the process of biosorption of nickel and chromium in an ascendant continuous-flow, fixed packed-bed bioreactor of sanitary sewage sludge was conducted in a search for solutions to the environmental problem caused by heavy metals. Analysis of the results demonstrated that the absorbent had an extraordinary capacity for biosorption of the heavy metals studied at about 9.0 pH of the effluent, with a removal percentage of over 90.0% for the two metals. Chemometric study results demonstrated that 20 days of the experimental system function were sufficient for achieving the maximum efficiency of sorption of the heavy metals studied by the sanitary sewage sludge employed. <![CDATA[<B>Parameters optimization for enzymatic assays using experimental design</B>]]> The conditions for maximization enzymatic activity were determined using experimental design and inulinase from Kluyveromyces marxianus ATCC 16045. The effects of substrate concentration (sucrose and inulin), pH and temperature on inulinase activity were verified using four factorial design and surface response analysis. Using sucrose as substrate. It has bean shown that the effects sucrose on enzymatic activity is not statistically significant and the best condition for the highest activity (110 U/mL) was achieved with temperature between 60&deg;C and 68&deg;C and pH between 4.5 and 5.0. Using inulin as substrate it was verified that temperature is the only variable statistically significant and the maximum activity was 7.3 U/mL at temperature between 50&deg;C and 51&deg;C. <![CDATA[<B>Design and optimization of new simulated moving bed plants</B>]]> The simulated moving bed (SMB) technology has attracted considerable attention for its efficiency as a chromatographic adsorptive separation. It has been increasingly applied to the separation of binary mixtures with low separation factors, namely to separate isomers. Although quite a vast amount of information has been published concerning the simulation and design of operating conditions of existing SMB plants, fewer works have addressed the question of design and optimisation of geometric parameters and operating conditions of a new adsorber, especially when mass transfer resistances are significant. The present work extends an algorithm developed elsewhere to design SMB equipment and optimize its operating conditions and applies it to the case of fructose-glucose separation using a cation-exchange resin as stationary phase in order to obtain nearly pure fructose in the extract and glucose in the raffinate. The constraints were set as 99% purity for both products. The objective function was chosen to be the adsorbent productivity. The algorithm attempted to find the minimum column lengths for increasing throughputs, which met the required purity constraint. Then, the best construction parameters and operating conditions were chosen as those for which the adsorbent productivity was maximum. The effects of the safety margins applied on the velocity ratios in sections 1 and 4 were examined and a heuristic rule for optimum eluent flowrate was derived. The effect of the purity requirements was also investigated. Finally, the calculated optimal operating points, in terms of flowrate ratios in SMB sections 2 and 3, were analysed in the frame of the equilibrium theory. Sound coherence was verified, which confirmed the accuracy and adequacy of the extended algorithm for the design and optimisation of a SMB adsorber with strong mass transfer effects. <![CDATA[<B>Interfacial phenomena at the compressed co<SUB>2</SUB>-water interface</B>]]> Compressed CO2 is considered to be a viable alternative to toxic volatile organic solvents with potential applications in areas including separation reactions, and materials formation processes. Thus an interest in CO2 stems from the fact that it is very inexpensive, has low toxicity, and is not a regulated. However, compressed CO2 has a zero dipole moment and weak van der Waals forces and thus is a poor solvent for both polar and most high molecular weight solutes, characteristics that severely restrict its applicability. In order to overcome this inherent inability, surfactant-stabilized organic and aqueous dispersions in CO2 have been proposed. This work will discuss fundamentals and recent advances in the design of amphiphiles for the novel CO2-water interface. <![CDATA[<B>Solubility of dense CO<SUB>2</SUB> in two biocompatible acrylate copolymers</B>]]> Biocompatible polymers and copolymers are frequently being used as part of controlled delivery systems. These systems can be prepared using a "clean and environment friendly" technology like supercritical fluids. One great advantage of this process is that compressed carbon dioxide has excellent plasticizing properties and can swell most biocompatible polymeric matrixes, thus promoting drug impregnation processes. Mass sorption of two acrylate biocompatible copolymers contact with supercritical carbon dioxide is reported. Equilibrium solubility of dense carbon dioxide in poly(methylmethacrylate-co-ethylhexylacrylate) and poly(methylmethacrylate-co-ethylhexylacrylate-co-ethyleneglycoldimethacrylate) was studied by a static method at 10.0 MPa and 313 K. The reticulated copolymer had Fickean behavior and its diffusion coefficient was calculated, under operating conditions. <![CDATA[<B>Improvement of soluble coffee aroma using an integrated process of supercritical CO<SUB>2</SUB> extraction with selective removal of the pungent volatiles by adsorption on activates carbon</B>]]> In this paper a two-step integrated process consisting of CO2 supercritical extraction of volatile coffee compounds (the most valuable) from roasted and milled coffee, and a subsequent step of selective removal of pungent volatiles by adsorption on activated carbon is presented. Some experiments were carried out with key compounds from roasted coffee aroma in order to study the adsorption step: ethyl acetate as a desirable compound and furfural as a pungent component. Operational parameters such as adsorption pressure and temperature and CO2 flowrate were optimized. Experiments were conducted at adsorption pressures of 12-17 MPa, adsorption temperatures of 35-50ºC and a solvent flow rate of 3-5 kg/h. In all cases, the solute concentration and the activated particle size were kept constant. Results show that low pressures (12 MPa), low temperatures (35ºC) and low CO2 flowrates (3 kg/h) are suitable for removing the undesirable pungent and smell components (e.g. furfural) and retaining the desirable aroma compounds (e.g. ethyl acetate). The later operation with real roasted coffee has corroborated the previous results obtained with the key compounds. <![CDATA[<B>Efficiency of water removal from water/ethanol mixtures using supercritical carbon dioxide</B>]]> Techniques involving supercritical carbon dioxide have been successfully used for the formation of drug particles with controlled size distributions. However, these processes show some limitations, particularly in processing aqueous solutions. A diagram walking algorithm based on available experimental data was developed to evaluate the effect of ethanol on the efficiency of water removal processes under different process conditions. Ethanol feeding was the key parameter resulting in a tenfold increase in the efficiency of water extraction. <![CDATA[<B>Desorption of heavy metals from ion exchange resin with water and carbon dioxide</B>]]> Adsorption and regeneration of ion exchange resins were studied using a subcritical solution of a CO2-H2O mixture and a fixed bed column. The commercial Amberlite IRC-50/IRC-86 cation exchange resins and Amberlite IRA-67 anion exchange resin were tested for heavy metals (Pb, Cu, Cd) adsorption from a solution with different initial metal concentrations at different temperatures. After adsorption, the loaded resins were regenerated with water and carbon dioxide at different temperatures and a pressure of 25 MPa. The efficiency of the IRC-50 resin was lower than that of the IRC-86 resin for the adsorption of metals like Cd, Cu and Pb. Results obtained for desorption of these metals indicated that the process could be used for Cd and in principle for Cu. Sorption of metal ions depended strongly on feed concentration. Mathematical modeling of the metal desorption process was carried out successfully as an extraction process. For this purpose, the VTII Model, which is applied to extraction from solids using supercritical solvents, was used in this work. <![CDATA[<B>Application of molecular sieves in the fractionation of lemongrass oil from high-pressure carbon dioxide extraction</B>]]> The aim of this work was to study the feasibility of simultaneous process of high-pressure extraction and fractionation of lemongrass essential oil using molecular sieves. For this purpose, a high-pressure laboratory-scale extraction unit coupled with a column with four different stationary phases for fractionation: ZSM5 zeolite, MCM-41 mesoporous material, alumina and silica was employed. Additionally, the effect of carbon dioxide extraction variables on the global yield and chemical composition of the essential oil was also studied in a temperature range of 293 to 313 K and a pressure range of 100 to 200 bar. The volatile organic compounds of the extracts were identified by a gas chromatograph coupled with a mass spectrometer detector (GC/MS). The results indicated that the extraction process variables and the stationary phase exerted an effect on both the extraction yield and the chemical composition of the extracts. <![CDATA[<B>Impregnation of pet films and PHB granules with curcumin in supercritical CO<SUB>2</B></SUB>]]> The process of dyeing poly(ethylene terephthalate) - PET films at 50, 60 and 65ºC and poly(hydroxybutyrate) - PHB granules at 60, 70 and 80ºC using supercritical carbon dioxide (scCO2) as solvent and ethanol as cosolvent was studied by DSC, TGA analysis and measurements of shrinkage to determine the morphological modifications caused by the scCO2 treatment of these materials. A comparison of the effects of annealing both polymers in scCO2 provided evidence that PHB had plasticization activity due to its crystallinity and that PET favored the dyeing process at high pressure when its temperature was raised to close to the Tg value. DSC and TGA measurements were obtained for all the samples. The DSC results showed that there was no significant structural change and the TGA data showed that thermal stability was not affected in the samples analyzed. <![CDATA[<B>Ginger and turmeric starches hydrolysis using subcritical water + CO<SUB>2</B></SUB>: <B>the effect of the SFE pre-treatment</B>]]> In this work, the hydrolysis of fresh and dried turmeric (Curcuma longa L.) and ginger (Zingiber officinale R.) in the presence of subcritical water + CO2 was studied. The hydrolysis of ginger and turmeric bagasses from supercritical fluid extraction was also studied. The reactions were done using subcritical water and CO2 at 150 bar, 200 &deg;C and reaction time of 11 minutes; the degree of reaction was monitored through the amount of starch hydrolyzed. Process yields were calculated using the amount of reducing and total sugars formed. The effects of supercritical fluid extraction in the starchy structures were observed by scanning electron microscopy. Higher degree of hydrolysis (97- 98 %) were obtained for fresh materials and the highest total sugar yield (74%) was established for ginger bagasse. The supercritical fluid extraction did not significantly modify the degree of hydrolysis in the tested conditions. <![CDATA[<B>Supercritical fluid extraction (SFE) of rice bran oil to obtain fractions enriched with tocopherols and tocotrienols</B>]]> Parboiled rice bran oil was obtained with supercritical CO2 at temperatures and pressures varying from 25 to 60ºC and from 150 to 250 bar, respectively. This study was divided into two different parts: initially, the experiments were carried out with one separation step. In the second part, experiments were performed with two separators in series. The temperatures and the pressures of the first separator were 25 and 40ºC, and 100 and 150 bar. The second separator was maintained at 2ºC and 25bar. This procedure results in the precipitation of rice bran oil with different concentrations of tocols in the first and second separators. The extracts obtained were analyzed by HPLC to verify the presence of tocopherols and tocotrienols. Unlike other vegetable oils, rice bran oil contains a larger amount of tocotrienols, specially gamma-tocotrienol, than of tocopherols. Finally the extraction curves were modeled by Sovová's method. <![CDATA[<B>Supercritical carbon dioxide extraction of pigments from <I>Bixa orellana</I> seeds (experiments and modeling)</B>]]> Supercritical CO2 extraction of the pigments from Bixa orellana seeds was carried out in a flow apparatus at a pressure of 200 bar and a temperature of 40 ºC at two fluid flow rates (0.67g/min and 1.12g/min). The efficiency of the extraction was low (only about 1% of the pigment was extracted). The increase in flow rate led to a decrease in pigment recovery. A large increase in recovery (from 1% to 45%) was achieved using supercritical carbon dioxide with 5 mol % ethanol as extraction fluid at pressures of 200 and 300 bar and temperatures of 40 and 60 ºC. Although the increase in temperature and pressure led to an increase in recovery, the changes in flow rate did not seem to affect it. Furthermore, two plug flow models were applied to describe the supercritical extraction of the pigments from annatto seeds. Mass transfer coefficients were determined and compared well with those obtained by other researchers with similar models for the supercritical extraction of solutes from plant materials. <![CDATA[<B>Extraction of ho-sho (<I>Cinnamomum camphora</I> nees and eberm var<I>. Linaloolifera fujita</I>) essential oil with supercritical CO<SUB>2</B></SUB>: <B>experiments and modeling</B>]]> Supercritical CO2 extraction of essential oil from the leaves of a variety of camphor tree known as Ho-Sho was studied. Experiments were carried out within the following ranges: CO2 flow rate (1 - 4 mL/min); pressure (80 - 100 bar); temperature (40 - 60 ºC) and particle size (0.37 - 1.0 mm). The equipment used was an HP 8670 T extractor module with an extraction cell volume of 7 mL. Two mathematical models of the process were proposed. Model 1 was a modified version of the traditional shrinking core model with effective diffusivity and the external mass transfer coefficient as the fitting parameters. Model 2 used an additional kinetic parameter based on an Arrhenius-like expression. Both models took into account the cell pressurization step. The best fit between the extraction model curves and the experimental data was obtained using model 2. <![CDATA[<B>Polypropylene grafted with glycidyl methacrylate using supercritical CO<SUB>2</SUB> medium</B>]]> Films of polypropylene (PP) were grafted with glycidil methacrylate (GMA) using supercritical CO2 as swelling agent and solvent. Different pressures and temperatures were used to study their effects on the soaking and grafting process. FTIR results showed signals at 1726 and 1640 cm-1, assigned to C=O and C=C (after the soaking process), and a decreased signal at 1640 cm-1 (after the grafting procedure), suggesting the effective grafting of GMA. For the grafted material immersed in ethylenediamine, peaks in the 3600 to 3250 cm-1 range (N-H stretching) were evident. Contact angle measurements showed an increasingly hydrophilic nature in the direction from pure PP to grafted PP/GMA (PP-g-GMA) to PP-g-GMA immersed in ethylenediamine (PP-g-GMA/En). X-ray photoelectron spectroscopy provided evidenced of the effective incorporation of ethylenediamine in the grafted material.