Aproveitamento da glicerina proveniente da produção de biodiesel na obtenção de híbrido de caulinita para adsorção de Cr3+

The aim of this work was to contribute to the creation of new ways of treating wastewater contaminated with Cr3+, based on solid-liquid adsorption. An adsorbent material was prepared by functionalization of kaolinite with glycerin biodiesel by-product. This material was tested for adsorption performed using a batch method, and results showed that inclusion of glycerin in the structure of kaolinite led to a significant increase in the capacity of Cr3+ adsorption. This contributes to the allocation of by-product of biodiesel and to the treatment of effluents from tanneries.

Especiação de cobre e zinco em urina: importância dos metais em doenças neurodegenerativas

Metals such as copper and zinc are essential for the development and maintenance of numerous enzymatic activities, mitochondrial functions, neurotransmission, and also for memorization and learning. However, disruption in their homeostasis can cause neurodegenerative disorders such as the Alzheimer and Parkinson diseases. In this work, the speciation of copper and zinc in urine samples was carried out. To this end, free and total metal concentrations were determined by square wave anodic stripping voltammetry using a glassy carbon electrode coated with bismuth film. The digestion of the samples was performed in a microwave with the addition of oxidant reagents.

Emissões naturais e antrópicas de nitrogênio, fósforo e metais para a bacia do Rio Macaé (Macaé, RJ, Brasil) sob influência das atividades de exploração de petroleo e gás na Bacia de Campos

Emission factors of natural processes and anthropogenic activities were used to estimate nutrients and metal loads for the lower Macaé river basin, which hosts the operational base for the offshore oil and gas exploration in the Campos Basin. The estimates indicated that emissions from anthropogenic activities are higher than natural emissions. Major contributing drivers include husbandry and urbanization, whose effluents receive no treatment. The increasing offshore oil exploration along the Brazilian littoral has resulted in rapid urbanization and, therefore might increase the inshore emission of anthropogenic chemicals in cases where effective residue control measures are not implemented in fluvial basins of the region.

Bioacumulação de metais pesados e nutrientes no mexilhão dourado do reservatório da Usina Hidrelétrica de Itaipu Binacional

This study aims to evaluate the bioaccumulation of macronutrients and heavy metals in the golden mussel according to its collection site and seasonality in the aquaculture area of the reservoir from April/2009 to March/2010. There is no difference (p > 0.05) in the concentration of metals with respect to the point of collection. The concentrations of Cu, Fe, Mn, Zn, Cd and Pb were higher (p < 0.05) in spring and summer than in fall and winter. Values of the heavy-metal pollution index (MPI) for collection point and seasonality indicate environmental contamination in the aquaculture area.

Síntese, caracterização e atividade fotocatalítica de catalisadores nanoestruturados de TiO2 dopados com metais

Titanium dioxide nanostructured catalysts (nanotubes) doped with different metals (silver, gold, copper, palladium and zinc) were synthesized by the hydrothermal method in order to promote an increase in their photocatalytic activity under visible light. The catalysts were characterized by X-ray diffraction, diffuse reflectance spectroscopy, transmission electron microscopy and specific area and pore volume determination. The materials' photocatalytic activity was evaluated by rhodamine B decomposition in a glass batch reactor. Under UV radiation, only nanotubes doped with palladium were more active than the TiO2 P25, but the samples doped with silver, palladium and gold exhibited better results than the undoped samples under visible light.

Adsorção do corante Reativo Azul 19 em solução aquosa por lama vermelha tratada quimicamente com peróxido de hidrogênio

Adsorption of Reactive Blue 19 dye onto activated red mud was investigated. Red mud was treated with hydrogen peroxide (LVQ) and heated at both 400 ºC (LVQ400) and 500 ºC (LVQ500). These samples were characterized by pH, specific surface area, point of zero charge and mineralogical composition. Adsorption was found to be significantly dependent on solution pH, with acidic conditions proving to be the most favorable. The adsorption followed pseudo-second-order kinetics. The Langmuir isotherm was the most appropriate to describe the phenomenon of dye removal using LVQ, LVQ400 and LVQ500, with maximum adsorption capacity of 384.62, 357.14 and 454.54 mg g-1, respectively.

Influência dos precursores de prata no crescimento de nanopartículas metálicas em vidros óxidos de metais pesados

In this work we report a systematic study on the influence of the chemical nature of silver precursors on the formation of glass-ceramics from oxide glasses. Thermal, structural and optical properties were analyzed as a function of the glass composition. Controlled crystallization was achieved by thermal treatment of the samples above glass transition. The influence of time of treatment on both nanoparticle growth and optical properties of the samples was studied by transmission electron microscopy and UV-Vis spectroscopy, respectively. Results showed that only glasses containing AgCl and AgNO3 led to glass-ceramics growth after thermal treatment.

A etimologia de biomoléculas com metais de transição como auxiliar na aprendizagem de Química Biológica

Numerous functional biomolecules are associated with metals, i.e. the metallobiomolecules; more specifically, some are dependent on transition metals required for several crucial biological roles. Nevertheless, their names can lead to ambiguous interpretations concerning the properties and performances of this group of biological molecules. Their etymology may be useful by providing a more perceptive insight into their features. However, etymology can lead to incongruous conclusions, requiring an especially careful approach to prevent errors. Examples illustrating these subjects shall be examined.

Método hidrometalúrgico para reciclagem de metais terras raras, cobalto, níquel, ferro e manganês de eletrodos negativos de baterias exauridas de Ni-MH de telefone celular

A hydrometallurgical method for the recovery of rare earth metals, cobalt, nickel, iron, and manganese from the negative electrodes of spent Ni - MH mobile phone batteries was developed. The rare earth compounds were obtained by chemical precipitation at pH 1.5, with sodium cerium sulfate (NaCe(SO4)2.H2O) and lanthanum sulfate (La2(SO4)3.H2O) as the major recovered components. Iron was recovered as Fe(OH)3 and FeO. Manganese was obtained as Mn3O4.The recovered Ni(OH)2 and Co(OH)2 were subsequently used to synthesize LiCoO2, LiNiO2 and CoO, for use as cathodes in ion-Li batteries. The anodes and recycled materials were characterized by analytical techniques.

Impregnação do ácido 12-tungstofosfórico em sílica - parte II: efeito de diferentes solventes na impregnação e atividade catalítica na esterificação metílica de ácido esteárico

Materials obtained by the immobilization of 12-tungstophosphoric acid (PTA) on silica using the method of impregnation with excess solution in distinct solvents (aqueous HCl, methanol:H2O, and acetonitrile) were evaluated for use as catalysts in the methyl esterification of stearic acid. Optimum conditions were established for the impregnation of 0.5 g (w/w) of PTA on amorphous silica, under stirring at 150 rpm for 24 h, using 20 mL of 0.1 mol L-1 HCl as the solvent. After calcination at 200 ºC, high conversions were obtained under mild reaction conditions, resulting in high turnover numbers. The catalyst was evaluated in ten catalytic cycles of use, where the activity was reduced only slightly, attesting its stability and the possibility to apply it to industrial production of methylesters.

Adsorção de CO2 em peneiras moleculares micro e mesoporosas

Microporous molecular sieves of type Y, Beta, ZSM-5, ZSM-12 and ZSM-35, and mesoporous molecular sieves of type MCM-41 and MCM-48, and these sieves modified with triethanolamine and ethylenediamine were obtained and characterized by XRD, FTIR, TGA and nitrogen adsorption. The adsorption tests were performed by the gravimetric method under a stream of CO2 at ambient temperature and pressure. The adsorbents studied showed maximum adsorption capacity of carbon dioxide in the range of 13.1 to 85.5 mg of CO2 per gram of adsorbent.

Influência das substâncias húmicas de sedimentos na biodisponibilidade de metais para o sistema aquático

In rivers, sediments act as sinks for retaining contaminants. This study evaluated the influence of sediment humic substances (HS) on the bioavailability of metals. The levels of metals in sediments and HS indicated that most are complexed with HS. Characterization of HS showed a high degree of humification. The complexation capacity of HS for metals established the affinity order:Pb2+

Adsorção de alfa-lactalbumina do soro de leite em hidroxiapatita: efeito do pH e da temperatura e análise termodinâmica

The nutritional and functional benefits offered by whey protein α-lactalbumin justify the great interest in its manufacture in large quantities at a high purity level. Hydroxyapatite is a calcium phosphate material able to adsorb proteins and can be synthesized at low production cost. Therefore, this work evaluated the adsorption of α-lactalbumin on hydroxyapatite using solid-liquid phase equilibrium data reported as adsorption isotherms. Van't Hoff's thermodynamics analysis showed that the adsorption process is entropically driven.

Desenvolvimento de reator tipo "dip catalyst" para filmes poliméricos contendo nanopartículas de metais de transição

This article describes the development of a new catalytic reactor designed to operate with nanoparticle-embedded polymer thin films. Stabilization of metal nanoparticles in films that serve as catalysts in organic reactions is relatively new; therefore, the development of reactors to facilitate their use is necessary. We describe in detail the preparation of the GDCR reactor-type "dip catalyst" and its evaluation in the Suzuki - Miyaura cross-coupling reaction of phenylboronic acid and 4-bromoanisole catalyzed by palladium nanoparticle-embedded cellulose acetate thin film (CA/PD(0)). Compared with earlier prototypes, GDCR reactor showed excellent results when operating with CA/PD(0) thin films.

AVALIAÇÃO DE MÉTODOS DE SOLUBILIZAÇÃO PARA DETERMINAÇÃO DE METAIS EM GLICERINA PROVENIENTE DA PRODUÇÃO DE BIODIESEL POR TÉCNICAS DE ESPECTROMETRIA ATÔMICA

This paper describes the evaluation of simple and fast solubilization methods for the determination of Ca, Mg, and K in glycerin samples from biodiesel production by atomic spectrometry. The solubilization in water was compared with two other methods: solubilization in formic acid and solubilization in ethanol. Using solubilization in water, determination of the three analytes was possible; the values of limits of detection for Ca, K, Mg were 0.31, 0.06, and 0.16 mg kg−1, respectively. Because no adequate reference material was available, the accuracy was evaluated by assessing the recoveries tests with both solubilization methods; the evaluation ranged from 90% to 115%, with values of relative standard deviation >8%, indicating good accuracy of the measure. Four crude glycerin samples obtained from biodiesel plants of Rio Grande do Sul were analyzed after treatment with the different methods of solubilization, and the obtained results of Ca, Mg, and K concentration were in agreement with the values obtained from both solubilization methods. Therefore, solubilization in water is concluded to be a simpler, faster, and viable method for sample preparation of glycerin.