1,720,967 research outputs found
Activity of magnetite-immobilized catalase in hydrogen peroxide decomposition
Get PDFThe present work analyzes the activity in decomposition of H 2O2 using magnetite-immobilized catalase. The support of catalase is a glutaraldehyde-treated magnetite (Fe3O4). The data obtained in the H2O2 decomposition are analyzed. The fitting of the initial rate of the H2O2 decomposition versus hydrogen peroxide concentration data is discussed using a specific program for enzyme kinetics modeling (Leonora). The free catalase from Aspergillus niger (3.5 or 10 U/mL) does not show substrate inactivation up to 0.4 M H2O2. The immobilized catalase at low catalyst concentration shows substrate inhibition. Using 1 mg/mL of supported catalase the predicted maximum activity is higher than in the case of the free catalase at similar catalase concentration, although the optimum temperature is lower (40°C versus 60°C).Fil: Horst, María Fernanda. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
Magnetite supported hematin as a biomimetic of horseradish peroxidase phenol removal by polymerization
Get PDFPhenol removal using HRP and hematin as biomimetic of HRP is presented at selected conditions at room temperature. The best results are obtained with treatment in two steps, with double addition of HRP or hematin and a final treatment with activated carbon. This two-step treatment achieved 90 % minimal conversion of initial phenol, at conditions commonly found in wastewaters (from 400 up to 1500 ppm phenol). Other additives such as chitosan, cellulose or polyethylenglycol (PEG) gave no satisfactory results. Hematin and magnetite-supported hematin showed comparable activities in phenol removal from aqueous solution. The supported hematin is an interesting alternative to HRP for practical application of biomimetic catalyst to phenol removal.Fil: Ambrosio, Karina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; Argentin
Activity of free peroxidases, hematin, magnetite-supported peroxidases and magnetite-supported hematin in the aniline elimination from water-UV-vis analysis
Get PDFThis manuscript presents the UV-vis study of the aniline elimination by polymerization using peroxidases from different sources and hematin, free and supported. The use of magnetite-supported hematin has potential in the implementation of aniline elimination by polymerization in acidic media at pH 4. The temperature must be selected between 45 and 65°C. Crude preparations of Pleurotus sajor caju (PSC) are an alternative to purified Horseradish peroxidase (HRP) as the catalyst of the reaction. Pernigraniline is the main species found in the reaction media after aniline elimination procedure. Supported oxidoreductases are active biocatalysts and conversion of aniline in the 30-90% range can be obtained, depending on the catalyst. The UV-vis spectra show bands corresponding to base and protoned (blue and purple-deep red) pernigraniline, a contribution of quinoid species at 480 nm and a minor contribution of base blue emeraldine and another oxidation intermediate states between pernigraniline and emeraldine. At selected conditions, the recovered solid showed greenish/reddish coloration. The goal is the precipitation of the aniline as polyaniline. Supported biocatalysts were less active than free enzymes.Fil: Saidman, Silvana Beatriz. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur; ArgentinaFil: Ferreira, María Luján. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
Adsorption of alizarin, Eriochrome blue black R, and fluorescein using different iron oxides as adsorbents
Get PDFThis work presents kinetic and thermodynamic analysis of the adsorption of three dyes: alizarin, eriochrome blue black R, and fluorescein onto goethite, Co-goethite, and magnetite of medium Brunauer-Emmett-Teller surface area. The adsorption of the dyes on the oxides is fast. Fluorescein exhibits the lowest level adsorption for all adsorbents with goethite being the most efficient adsorbent when milligrams of dye per gram of oxide are considered. The Langmuir isotherm is the most appropriate for describing the adsorption data for the following systems: alizarin-magnetite and eriochrome and fluorescein with the three adsorbents, while alizarin-goethite and alizarin-Co-goethite show better fits with Freundlich isotherm. Molecular modeling using MM2 was used to analyze the steric effects on adsorption.Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
The effect of pH in the adsorption of Alizarin and Eriochrome Blue Black R onto iron oxides
Get PDFThe adsorption process of two dyes as a function of pH on three different adsorbents (goethite, Co-goethite, and magnetite) has been analyzed. Typical anionic adsorption behavior was observed for both dyes onto goethite and Co-goethite. The adsorption level was practically constant in the range of pH studied when the adsorbent was magnetite. The constant capacitance model (CCM) was employed to fit the experimental results. The surface complexes proposed from the adsorption data were in agreement with the patterns obtained from FTIR spectroscopy and a molecular mechanics calculation. Goethite has very good performance as adsorbent of Alizarin and Eriochrome Blue Black R. The presence of a foreign cation in Co-goethite does not improve the adsorption abilities of goethite. At low pH, the amounts of Alizarin and Eriochrome Blue Black R adsorbed on goethite and Co-goethite are similar. However, a higher dependence with the increase of pH is observed by Eriochrome Blue Black R. On magnetite, the dye adsorption shows less affinity for both dyes. Electronic and steric considerations can explain the trends found in the adsorption of the two dyes on the three iron oxides studied in this work. © 2009 Elsevier B.V. All rights reserved.Fil: Pirillo, Silvina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
Structure and reactivity of synthetic Co-substituted goethites
Get PDFA set of synthetic goethites were prepared from Fe3+- and Co2+-nitrate solutions in alkaline media with a Co/(Co + Fe) ratio (xCo) up to 10 mol%. The structural characterization of the resultant solid phases was carried out by X-ray diffraction (XRD). XRD analyses showed that in preparations with xCo <10 mol%, Co-substituted goethite was the only crystalline phase present. Atomic and cell parameters for the samples synthesized were obtained by the Rietveld refinement of the XRD data, and showed that the unit cell in the goethite-like phase is contracted as a function of xCo. Little deviation from the Vegard rule was observed for all unit-cell parameters. Cobalt substitution produces an increase in the surface area of the goethite, as well as an increment in the dehydroxylation temperature. The acid dissolution of all Co-goethites showed an increase in dissolution rate with the Co content, and a congruent behavior was observed. The activation energy for dissolution was obtained two samples. A modified first-order Kabai equation best describes the dissolution data.Fil: Alvarez, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Sileo, Elsa Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
Supported biocatalysts for Alizarin and Eriochrome Blue Black R degradation using hydrogen peroxide
Get PDFThe goal of this manuscript was to study the immobilization of horseradish peroxidase (HRP) and hematin on different supports at selected conditions to be used in the removal of two synthetic dyes: Alizarin Red (AR) and Eriochrome Blue Black R (EBBR). Reuse in the target reactions was tested for the best biocatalysts. Three supports were selected: magnetite-activated carbon Fe 3O 4/C, activated carbon C and chitosan CS. Several reasons led to discard the use of Fe 3O 4/C and C as supports for hematin and HRP. CS-glutaraldehyde (GA)-HRP not only has low ability to remove EBBR, but also the enzymatic activity of HRP could not be separated from the dye adsorption on CS. However, some adsorptive functions of CS-GA were lost when HRP was supported on it. In the case of CS-GA-hematin, the most important factors for EBBR removal are dye concentration and mass of catalyst, whereas the temperature has almost no effect on the conversion of dye, considering in all cases the H 2O 2 concentration (0.021M) constant. There was not a marked decrease in the removal of AR even after the ninth reuse in the case of CS-GA-hematin. For EBBR removal, with CS-GA-HRP, in the second reuse the catalyst was completely deactivated, whereas with CS-GA-hematin this was found only in the fourth reuse.Fil: Pirillo, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina. Universidad Nacional del Sur. Departamento de Química; Argentin
An accurate UV/visible method to quantify proteins and nzymes:Impact of aggregation, buffer concentration and the nature of the standard
Get PDFA simple, fast and low cost UV/visible based method to quantify proteins or enzymes is presented. This method avoids some drawbacks found using conventional techniques. Representative proteins and enzymes such as bovine serum albumin (BSA), insulin (Ins.), Rhizomucor meihei lipase (RML), Candida rugosa lipase (CRL) and horseradish peroxidase (HRP) were assayed as model. Experiments revealed that the aggregation of the enzyme/protein molecules in aqueous solution was the main cause of inaccurate results obtained with the simple UV/visible method. It was determined that aggregation of proteins/ enzymes in aqueous solutions follows a reversible mechanism that could be reverted by simple magnetic stirring treatment. The results achieved within this study warn about common error sources in protein quantification by UV/visible based methods and clearly shows the magnitude of the mistakes that could be achieved if aggregation and other factors are not considered.Fil: Lassalle, Verónica Leticia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Pirillo, Silvina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Rueda, Elsa Haydee. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Química del Sur. Universidad Nacional del Sur. Departamento de Química. Instituto de Química del Sur; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
On the nature of goethite, Mn-goethite and Co-goethite as supports for gold nanoparticles
Get PDFMn- and Co-substituted goethite (α-MnFeOOH and α-CoFeOOH) and pure goethite (α-FeOOH) were studied as supports for gold catalysts. The textural properties of these solids were studied by N2/77 K adsorption. Mn and Co substitutions gave rise to an increase of the specific surface area, as measured by BET equation. A DTA study indicated that the thermal stability of goethite was increased by Mn and Co incorporation. XRD analysis showed that both Mn and Co strongly modified goethite cell parameters, giving rise to an increase of the reducibility of both substituted oxyhydroxides, as measured by TPR. Three different samples were obtained by anchoring gold by direct anion exchange (DAE) method from HAuCl4: Au/α-FeOOH, Au/α-CoFeOOH and Au/α-MnFeOOH. FT-IR indicated that gold species were attached to OH goethite groups, while TEM analysis demonstrated that gold particles were in the nanometric range for all the samples. On pure goethite gold particles size distribution was relatively narrow, while for the cases of Au/α-MnFeOOH and Au/α-CoFeOOH a wide crystal size distribution were obtained. It is concluded that α-MnFeOOH and α-CoFeOOH are better supports for the gold particles since reducibility, thermal stability and specific surface area are higher than in the case of pure α-FeOOH. © 2007 Elsevier B.V. All rights reserved.Fil: Campo, Betiana Carla. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Rosseler, Olivier. Centre National de la Recherche Scientifique; FranciaFil: Alvarez, Mariana. Universidad Nacional del Sur; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur; ArgentinaFil: Volpe, María Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentin
A discussion of a mechanism for isomerization of n-butane on sulfated zirconia
Get PDFAlthough a huge amount of experimental work has been done, there is no clear picture about the superacidity in sulfated zirconia (SZ). Some authors think that sulfated zirconia is not superacid at all. Moreover, the structure of active site in n-butane isomerization is still now under controversy. This work tries to give some light about the mechanism of n-butane isomerization, taking into account experimental and theoretical works from others and from our own. MM2 and DFT simple calculations were performed in order to clarify the nature of the supported active species in sulfated zirconia. It is clear that a penta-coordinated species, monomeric or even dimeric, would be responsible for forming the most active sites at reaction conditions of n-butane isomerization. This idea is the key of this article. Different studies demonstrated that no superacidity is present before contact with n-butane. The sites formed at reaction conditions allow the n-butane dehydrogenation and its isomerization. A bimolecular mechanism of n-butane isomerization on penta-coordinated sites is proposed to occur. Several steps are discussed.Fil: García, Elba Ana. Universidad Nacional del Sur. Departamento de Química; ArgentinaFil: Volpe, María Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Ferreira, María Luján. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; ArgentinaFil: Rueda, Elsa Haydee. Universidad Nacional del Sur. Departamento de Química; Argentin
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