Showing papers in "Química Nova in 2011"
TL;DR: In this paper, the authors used multiple regression to predict the micropore volume and total pore volume of activated carbon samples produced from several raw materials, including methylene blue and iodine adsorption.
Abstract: micropore volume and total pore volume using multiple regression. The models obtained from the calibrations were used in predicting these physical properties of a test group of activated carbon samples produced from several raw materials. In all cases, the predicted values were in good agreement with the expected values. The method allows extracting more information from the methylene blue and iodine adsorption studies than normally obtained with this type of material.
164 citations
TL;DR: In this article, a critical and comprehensive review about the principles and recent mechanism advances in electrocatalysis for wastewater treatment is presented, where the authors focus on the role of the electrode material in the selectivity.
Abstract: Over 50 years, several scientists and industries have developed new alternatives for wastewater treatment and remediation. Recently, electrochemical technology has been largely developed mainly because of its versatility and environmental compatibility. Scientific contributions about role of the electrode material have allowed determining that the influence of material in the selectivity is an important parameter. However, to interpret this behavior, comprehensive physical chemistry models for organics destruction, related to electrochemical phenomena and material surfaces, were proposed in the last decades. So, this paper presents a critical and comprehensive review about the principles and recent mechanism advances in electrocatalysis for wastewater treatment.
103 citations
TL;DR: In this article, the feasibility of preparing nanocapsules and nanoemulsions using tea tree oil as oily phase aiming to protect its volatilization was evaluated, and the results showed that the inclusion of the oil in nanocapules showed higher protection against VOLATILization.
Abstract: The goal of this study was to evaluate the feasibility of preparing nanocapsules and nanoemulsions using tea tree oil as oily phase aiming to protect its volatilization. The nanostructures presented nanometric mean size (160-220 nm) with a polydispersity index below 0.25 and negative zeta potential. The pH values were 6.43 ± 0.37 and 5.98 ± 0.00 for nanoemulsions and nanocapsules, respectively. The oil content after preparation was 96%. The inclusion of tea tree oil in nanocapsules showed higher protection against volatilization. The analysis of mean size and polydispersity index of formulations presented no significant alteration during the storage time.
84 citations
TL;DR: In this paper, the authors compared activated carbon, activated earth, diatomaceous earth, chitin and chitosan to removal acid blue 9, food yellow 3 and FD&C yellow no 5 dyes from aqueous solutions with different pH values (2-10).
Abstract: This work compared activated carbon, activated earth, diatomaceous earth, chitin and chitosan to removal acid blue 9, food yellow 3 and FD&C yellow no 5 dyes from aqueous solutions with different pH values (2-10). In the best process condition for each dye, equilibrium studies were carried out at different temperatures (from 298 to 328 K) and Langmuir, Freundlich, Redlich-Peterson, Temkin and Dubinin-Radushkevich models were fitted with experimental data. In addition, entropy change, Gibbs free energy change and enthalpy change were obtained in order to verify the thermodynamic adsorption behavior.
82 citations
TL;DR: In this article, the authors describe the structure, properties, synthesis and performance of compounds that are catalytic active in both esterification and transesterification reactions in biodiesel.
Abstract: The recent increase in the world biodiesel demand, along with the need to reduce costs while improving the environmental sustainability of the entire biodiesel production chain, have led to the search for heterogeneous catalysts that would be efficient and highly amenable to recycling. Many classes of materials have been tested for these purposes. Among these are zeolites, ion-exchange resins, inorganic oxides, guanidines, metal complexes, layered compounds and ionic liquids. This review article describes the structure, properties, synthesis and performance of compounds that are catalytic active in both esterification and transesterification reactions.
63 citations
TL;DR: The volatile oils from A. virgata was the most active, exhibiting moderate antimicrobial activity against the bacteria Staphylococcus aureus, Bacillus cereus and Escherichia coli.
Abstract: Volatile oils from the leaves of Verbenaceae species Aloysia virgata, Lantana camara, Lantana trifolia, Lantana montevidensis, Lippia brasiliensis and Lippia sericea were investigated for its chemical composition and antibacterial activity. The volatile oils were characterized by a high content of sesquiterpenes of which (E)-caryophyllene (10-35%), germacrene-D (5-46%) and bicyclogermacrene (7-17%) were the major components for all studied species. For the flowers, a higher concentration of monoterpenes was observed for the species L. camara, L. trifolia and L. brasiliensis. These compounds probably act as attractive to specific pollinators. The volatile oils from A. virgata was the most active, exhibiting moderate antimicrobial activity against the bacteria Staphylococcus aureus, Bacillus cereus and Escherichia coli.
62 citations
TL;DR: In this article, a solvent emulsification evaporation method was used to produce poly-e-caprolactone (PCL) nanoparticles with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process, excellent encapsulation efficiency (81.3 ± 4.2%), and spherical shape.
Abstract: Nanoparticles were produced by solvent emulsification evaporation method with the following characteristics: nanometric size (238 ± 3 nm), narrow polydispersity index (0.11), negative zeta potential (-15.1 mV), good yield of the process (73 ± 1.5%), excellent encapsulation efficiency (81.3 ± 4.2%) and spherical shape. X-rays diffraction demonstrated the loss of drug crystallinity after encapsulation; however, the profile of the diffractograms of the poly-e-caprolactone (PCL) nanoparticles was kept. Differential scanning calorimetry thermograms, correspondingly, exhibited the loss of drug melting peak and the increasing of the melting point of the PCL nanoparticles, evidencing an interaction drug-polymer. Naproxen release was low and sustained obeying the Higuchi´s kinetic. The results show that nanoparticles are promising sustained release system to the naproxen.
61 citations
TL;DR: The absorption and metabolism of phenolic acids, a class ofphenolic compounds abundant in food, and the methodologies used for evaluation of bioavailability are discussed.
Abstract: The daily intake of phenolic compounds does not necessarily reflect the dose at which they reach the physiological targets in the organisms. The biological activity of phenolic compounds metabolites found in blood, organs and target tissues, as a result of digestive and hepatic activity, may differ from those of the native forms of the substances. This review discusses the absorption and metabolism of phenolic acids, a class of phenolic compounds abundant in food, and the methodologies used for evaluation of bioavailability.
56 citations
TL;DR: In this article, a study on the production of silica gel in hydrothermal process using residual rice husk ash is presented, and the compressive strengths were determined for cement pastes containing silica Gel (0.0, 2.5 or 5% by mass).
Abstract: This paper presents a study on the production of silica gel in hydrothermal process using residual rice husk ash. Measurements of the chemical composition, X-ray diffraction, infrared spectroscopy, particle size distribution, and pozzolanic activity were carried out in order to characterize the obtained material, and the optimal silica gel was selected for use as a mineral additive in cement pastes. The compressive strengths were determined for cement pastes containing silica gel (0.0, 2.5 or 5% by mass) in different times. The results indicate that the mixtures containing silica gel showed improved mechanical behavior over all time periods evaluated.
54 citations
TL;DR: In this paper, a review mainly deals with chemical and enzymatic transformations of glycerol to obtain chiral building blocks for synthesis of pharmaceuticals and natural products, which is considered a coproduct of biodiesel industry.
Abstract: Presently glycerol is considered a co-product of biodiesel industry. As the biodiesel production is exponentially increasing, glycerol generated from the transesterification of vegetable oils and fats is also being produced on a large scale, and turned out to be essential seeking for novel alternatives to the consumption of the extra volume, in crude and/or as derivatives high added value. This review mainly deals with chemical and enzymatic transformations of glycerol to obtain chiral building blocks for synthesis of pharmaceuticals and natural products.
54 citations
TL;DR: In this article, the authors describe the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide, and three heavy metals were selected for this study: cadmium, lead and silver.
Abstract: This paper describes the adsorption of heavy metals ions from aqueous solution by hydrous niobium oxide. Three heavy metals were selected for this study: cadmium, lead and silver. Adsorption isotherms were well fitted by Langmuir model. Maximum adsorption capacity (Q0) for Pb2 +, Ag+ and Cd2 + was found to be 452.5, 188.68 and 8.85 mg g-1, respectively.
TL;DR: This review is an insight into the exploitation of utilization of chitosan based-supports in different geometrical configurations on the immobilization of enzymes by different protocols for further application in biotransformation reactions.
Abstract: Chitosan, poly[β-(1-4)-linked-2-amino-2-deoxy-D-glucose], is the N-deacetylated product of chitin which is a major component of arthropod and crustacean shells such as lobsters, crabs, shrimps, and cuttlefishes. In addition, chitosan has many significant biological and chemical properties such as biodegradability, biocompatibility and bioactivity as well as polycationic properties. Thus, it has been widely used in many industrial and biomedical applications including wastewater treatment, chromatographic support, carriers for controlled drug delivery and enzyme immobilization. This review is an insight into the exploitation of utilization of chitosan based-supports in different geometrical configurations on the immobilization of enzymes by different protocols for further application in biotransformation reactions.
TL;DR: In this paper, the properties of silica (SiO2) from rice husk (RH) and Rice husk ash (RHA) extracted by acid-and heat-treatment were compared.
Abstract: This study compared properties of silica (SiO2) from rice husk (RH) and rice husk ash (RHA) extracted by acid- and heat-treatment. The SiO2 from RH was in amorphous phase with nearly 100% purity while that from RHA was in crystalline phase with 97.56% purity. Both extracted SiO2 were used in the synthesis of zeolite NaY but that from RH was better due to the efficiency in product recovery and simplicity of extraction. After the NaY was exchanged to NH4Y and calcined to convert to HY, the product did not carry over the textural properties of the parent NaY and NH4Y.
TL;DR: The test results obtained from thermal analysis are directly related to the quality of a pharmaceutical product, whether the stability or bioavailability of the pharmaceutical product.
Abstract: Several matters of the pharmaceutical demonstrate the great importance of thermal analysis application, especially TG and DSC for the pharmaceutical industry future, namely: characterization of the drugs with the thermal events definition, in studies of drug purity, in the polymorphs identification, in compatibility studies of solid dosage pharmaceutical formulations, in drugs and pharmaceutical formulations thermal stability, and in determination of shelf life for isothermal degradation kinetics by extrapolation using the Arrhenius equation. Thus, the test results obtained from thermal analysis are directly related to the quality of a pharmaceutical product, whether the stability or bioavailability of the pharmaceutical product.
TL;DR: The data presented in this work strongly supports the view that plants of Byrsonima genus have potential therapeutic action.
Abstract: Species of the Byrsonima genus are widely distributed around the neotropical zone, being frequently used in folk medicine to treat gastrointestinal, respiratory and skin diseases. This article briefly reviews the ethnopharmacology, pharmacology and phytochemistry of the Byrsonima genus. Eighty three compounds isolated from different species are reported, most of them being flavonoids or triperpenes. The pharmacological studies carried out with the extracts from these plants emphasize on the antimicrobial activity, however other activities have also been investigated leading to promising results. The data presented in this work strongly supports the view that plants of Byrsonima genus have potential therapeutic action.
TL;DR: This paper emphasizes the coordination of metals to antibiotics as a strategy for reversing antibiotic resistance and production of new drugs, with a special focus on quinolones, fluoroquinolone, sulfonamides and tetracyclines.
Abstract: Antibiotic resistance has been growing at an alarming rate and consequently the arsenal of effective antibiotics against Gram-negative and Gram-positive bacteria has dropped dramatically. In this sense there is a strong need to produce new substances that not only have good spectrum of activity, but having new mechanisms of action. In this regard, this paper emphasizes the coordination of metals to antibiotics as a strategy for reversing antibiotic resistance and production of new drugs, with a special focus on quinolones, fluoroquinolones, sulfonamides and tetracyclines.
TL;DR: In this paper, the principles of these sample preparation techniques associated with the analysis by Liquid Chromatography with Diode Array Detection (LC-DAD) or Mass Spectrometry (LCMS) are described and an overview of several applications were presented and discussed.
Abstract: The determination of pesticide residues in water samples by Liquid Chromatography require sample preparation for extraction and enrichment of the analytes with the minimization of interferences to achieve adequate detection limits. The Solid Phase Extraction (SPE), Solid Phase Microextraction (SPME), Stir Bar Sorptive Extraction (SBSE) and Dispersive Liquid-Liquid Microextraction (DLLME) techniques have been widely used for extraction of pesticides in water. In this review, the principles of these sample preparation techniques associated with the analysis by Liquid Chromatography with Diode Array Detection (LC-DAD) or Mass Spectrometry (LC-MS) are described and an overview of several applications were presented and discussed.
TL;DR: This work aims to discuss some strategies related to the crosslinking of chitosan focusing on reagents, reaction mechanisms and properties/applications of the crosslinked derivatives in several fields of science.
Abstract: One of the most important aspects of chitosan' derivatization depends on the crosslinking of their polymeric chains. This chemical strategy may confer new properties to those derivatives, which can be used to enhance their biotechnological applications. So far, this work aims to discuss some strategies related to the crosslinking of chitosan focusing on reagents, reaction mechanisms and properties/applications of the crosslinked derivatives in several fields of science.
TL;DR: In this paper, high performance liquid chromatography is recommended to separate emerging organic pollutants with characteristics of high polarity and low volatility, especially pharmaceuticals, from environmental matrices, which may be candidates for future regulation as they offer potential risk to environmental and human health due to their continual entrance into the environment.
Abstract: Emerging organic pollutants (EOP) include many environmental contaminants based on commercial products such as pharmaceuticals, personal care products, detergents, gasoline, polymers, etc. EOP may be candidates for future regulation as they offer potential risk to environmental and human health due to their continual entrance into the environment and to the fact that even the most modern wastewater treatment plants are not able to totally transform / remove these compounds. High performance liquid chromatography is recommended to separate emerging organic pollutants with characteristics of high polarity and low volatility, especially pharmaceuticals, from environmental matrices.
TL;DR: Citric acid was used as a compatibilizer in the production of starch and PBAT films plasticized with glycerol and processed by blow extrusion as discussed by the authors, which was characterized by WVP, mechanical properties, FT-IR-ATR and SEM.
Abstract: Citric acid was used as a compatibilizer in the production of starch and PBAT films plasticized with glycerol and processed by blow extrusion. Films produced were characterized by WVP, mechanical properties, FT-IR-ATR and SEM. WPV ranged from 3.71 to 12.73×10-11 g m-1 s-1 Pa-1, while tensile strength and elongation at break ranged from 1.81 to 7.15 MPa and from 8.61 to 23.63%, respectively. Increasing the citric acid concentration improved WVP and slightly decreased film resistance and elongation. The films micrographs revealed a more homogeneous material with the addition of citric acid. However, the infrared spectra revealed little about cross-linking esterification reaction
TL;DR: A brief history on the three generations of antifouling paints was provided and actions were suggested in order to appraise the current status of the environmental impact caused by these compounds in South America.
Abstract: Antifouling agents have been used on vessels and boats since ancient civilizations. Thus, a brief history on the three generations of antifouling paints was provided in the present review. Additionally, information about physic-chemical properties, environmental levels, toxicology and analytical methods was discussed for the 16 "new" booster biocides used as third-generation antifouling paints. The main problems, limitations and future trends related to this subject were also presented. Finally, actions were suggested in order to appraise the current status of the environmental impact caused by these compounds in South America.
TL;DR: In this paper, two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits, which were characterised by sensory and thermal analyses (TGA-DSC), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Abstract: Two food products (powders) were obtained by hot-air drying or lyophilisation methods on the whole guava fruits. The powders were characterised by sensory and thermal analyses (TGA-DSC), infrared spectroscopy (IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Thermal, morphological and structural characterisations showed a similar behaviour for the two solids. TGA-DSC and IR showed the presence of pectin as the main constituent of solids. A semi-crystalline profile was evidenced by XRD, and lamellar/spherical morphologies were observed by SEM. Sensory analyses revealed an aroma highly related to guava. These value-added food products are an alternative to process guava and avoid loss during postharvest handling.
TL;DR: Galactomannans show potential in the global trend towards the use of more plant-based products for ecological motives, and their production and application do not cause pollution or disturb the ecosystem.
Abstract: The pharmaceutical use of galactomannans from different sources, commercial and noncommercial, has been extensively studied over the past decade. Galactomannans show potential in the global trend towards the use of more plant-based products for ecological motives, and their production and application do not cause pollution or disturb the ecosystem. There is a variety of galactomannan sources and various pharmaceutical forms of application, such as tablets or capsules, hydrogels and films. Besides the simple use as inert excipient this polysaccharides play role in the modification of drug release, especially in colonic environmental, as a matrix or coating material.
TL;DR: In this paper, an evaluation was made of the properties of sugarcane bagasse during the storage process for subsequent burning in a boiler, and the results indicated that, during storage of bagasse, dry or damp, the biomass loses up to 32% of its calorific power, due to decomposition of the hemicellulose.
Abstract: An evaluation was made of the properties of sugarcane bagasse during the storage process for subsequent burning in a boiler. Samples of bagasse were collected over a period of 150 days from the Caete sugar mill (MG) at various points of the stockpile soon after the sugarcane was pressed to extract its juice, as well as from natural bagasse, dry and damp. Thermal analyses of the samples were carried out and the results indicated that, during the storage of bagasse, dry or damp, the biomass loses up to 32% of its calorific power, due to decomposition of the hemicellulose.
TL;DR: Results suggest the importance of feeding habits and trophic level in the bioaccumulation of methylmercury by aquatic biota and indicate that biomagnification may be occurring along the food web.
Abstract: -1 dry wt.), whereas microplankton presented the lowest (8.9 ± 3.3 µg kg -1 dry wt.). The successive amplification of methylmercury concentrations and its bioconcentration factor with increasing trophic levels from base to top indicate that biomagnification may be occurring along the food web. Results suggest the importance of feeding habits and trophic level in the bioaccumulation of methylmercury by aquatic biota.
TL;DR: The authors described a Problem-Based Learning (PBL) experience that taught organophosphorus pesticides chemistry, its human health effects and acetylcholinesterase assay to secondary students.
Abstract: This article describes a Problem-Based Learning (PBL) experience that taught organophosphorus pesticides chemistry, its human health effects and acetylcholinesterase assay to secondary students. The teaching process was based on a real intoxication case and ended with students' activities report presentation. The apparent lack of teacher reference and inexistence of a curriculum based on a strict textbook in which PBL is based on leads inexperienced students to insecurity and the idea that teachers are not doing there jobs. One way to minimize this situation is to use real cases in other to interest students as stakeholders of central problem solution.
TL;DR: The enzymatic and non-enzymatic mechanisms involved in the biodegradation of lignocellulosic materials by fungi were reviewed and the technological applications of these extracellular metabolites are presented and discussed.
Abstract: MECHANISMS INVOLVED IN THE BIODEGRADATION OF LIGNOCELLULOSIC MATERIALS AND RELATED TECHNOLOGICAL APPLICATIONS. The biodegradation of lignocellulosic materials is an important natural process because it is responsible for the carbon recycling. When induced under controlled conditions, this process can be used for technological applications such as biopulping, biobleaching of cellulosic pulps, pre-treatment for subsequent saccharification and cellulosic-ethanol production, and increase of the digestibility in agroindustrial residues used for animal feed. In the present work, the enzymatic and non-enzymatic mechanisms involved in the biodegradation of lignocellulosic materials by fungi were reviewed. Furthermore, the technological applications of these extracellular metabolites are presented and discussed.
TL;DR: The intent of this revision was to catalyze research efforts to expand the list of products and to present an updated evaluation of potential target structures for chemical production.
Abstract: A sugar cane mill is at the present moment a modest biorefinery producing few products such as sugar, ethanol and polyhydroxybutyrate (PHB). In the near future, this mill can expand its production using several renewable feedstock's to produce biofuels and high value biobased chemicals. However, the choice of appropriate products for addition to the portfolio is challenged by a lack of broad-based conversion technology coupled with a plethora of potential targets. The intent of this revision was to catalyze research efforts to expand the list of products and to present an updated evaluation of potential target structures for chemical production.
TL;DR: Although acacetin and 7,4′-Di-O-methylisoscutellarein did not display relevant antibacterial activity, they modulated the activity of antibiotics, i.e. in combination with antibiotics at 64 µg/mL (¼ MIC), a two-fold reduction in the MIC was observed for norfloxacin and ethidium bromide.
Abstract: From the aerial parts of Sidastrum micranthum (A. St.-Hil.) Fryxell (Malvaceae) were isolated m-methoxy-p-hydroxy-benzaldehyde, o-hydroxy-benzoic acid, acacetin, quercetin, 7,4′-Di-O-methylisoscutellarein, genkwanin and tiliroside. These compounds were identified by data analyses of spectroscopic methods. Although acacetin and 7,4′-Di-O-methylisoscutellarein did not display relevant antibacterial activity (MIC = 256 µg/mL), they modulated the activity of antibiotics, i.e. in combination with antibiotics at 64 µg/mL (¼ MIC), a two-fold reduction in the MIC was observed for norfloxacin and ethidium bromide; regarding tetracycline and erythromycin a two-fold reduction in the MIC was observed only with 7,4′-Di-O-methylisoscutellarein.
TL;DR: Glyphosate was determined in runoff and leaching waters in agricultural soil that received an application of active ingredient and was exposed to simulated intensive rain conditions as mentioned in this paper, and the concentrations were lower than the pattern in the Brazilian Regulation MS N. 518/2004 for drinking water.
Abstract: Glyphosate was determined in runoff and leaching waters in agricultural soil that received an application of active ingredient and was exposed to simulated intensive rain conditions. The concentrations decreased during the simulation period and the concentrations of the runoff were higher than those achieved in the samples of leaching waters. The concentrations were lower than the pattern in the Brazilian Regulation MS N. 518/2004 for drinking water. The transported load of the applied active ingredient by the leaching was of 15.4% (w/w) and for the runoff was of 1.7% (w/w).